There seems to be much confusion about "Perry reflex". I've seen several build-alongs where the bowyer says they are doing "Perry reflex", when actually they are just doing "reflex."

Anyway, I made this little drawing hoping that it helps clear things up. Now granted, this is going from memory from what I read in the Trad. Bowyers Bibles, and maybe I misread it, but I'm pretty sure that this is right.

I haven't made one yet, but if I understand right, often times a "Perry reflex" bow will actually be almost flat when unstrung - not much of a reflex profile.

Also, depending on how many glue-ups you are doing, the glued stave is flipped over each time. Hope this makes sense. I'm re-reading it and I'm not sure if it does!

It's hard to see, but the orange/blue is reversed on the bottom. Thus, the reflex is "reversed" (or to coin a term "Perry'd")

What advantage does a Perry Reflex give to the bow?

Cool. Looks like I got it wrong as usual, tee hee. Ill make a note on the boo thread. Thanks for clearing it up. I often feel like im groping around in the dark at the mo, Im glad someone has a torch:-)

It makes sense, but it's what I recall the TBB explained as "Perry" reflex, which as a single glue up w/ reflex forced in one plane w/ 2 lams. To be honest, it's not a "new" technique, and I know I've read both techniques have been tried. In the case of all natural either 2 or more lams all glued at once and in the some direction. Another I think might have been a famous ELB bowyer in England (Chris Boyton?), with opposing glue ups like you describe here. Oddly neither merit being named after Dan Perry, who re-introduced the technique to a new audiance in the last decade or so.

Perry Reflex has been shown to add speed, and reduce set. I'm sure it has other advantages, too, but I don't remember what they are!

Does someone have a copy of the Trad. Bowyers Bible (I don't remember which volume) and can post some highlights of what it says?

Ive got all four of them but their at my workshop I'll have a look and post.

Any forced glued in reflex is "perry reflex" it doesn't matter how many laminations there are.

In TBB1 it was described as a bamboo backed hickory. Bacically a backed board.

No magic to it. Nothing new. No invention. No secret. It's just reflex. There is some thought that because the board is tillered so it can bend evenly when being reflexed, it's somehow a new finding. To me, that is assuming that bowyers before TBB were somehow ignorant to what they were doing.

Everything old can be new again if you close your mind to those who came before you.

The way Perry reflex got it's name was when Tim Baker named it after Dan Perry. Dan Perry never claimed to be the one who discovered it. He simply had success with it in his flight shooting bows and went on to explain the theory behind it. I don't know the exact explanation but it can only be Perry reflex on a simple backed board bow, You are adding tension strength to the core without tapping into it's capacity to bend. On an average a Perry reflexed bow will outperform a self bow by about 10%, this is very subtantial. Steve

Thanks for the help in clarifying all this. I see I was a little mistaken, too!

Cool picture though.

"...an average a Perry reflexed bow will outperform a self bow by about 10%..."

A reflexed glue up can yield 10% bonus over a selfbow, but only if the bowyer gets nearly all that's on the table. Over a naturally reflexed stave of good osage tension wood of similar profile (a fair test in my view), I'm not convinced the average home crafter would produce hunting style bows with such pronouned difference (160 fps to 176 fps at 10 gpp). But it's danged hard to quantify. Not suggesting Steve's experience doesn't consistantly yield 10%, I just hate generalization I guess.

David, it would be good to get some hard facts on this. Speaking just for myself I usually try to expect between about 166 to 172 from a self bow. From a perry reflex bow I look for a minimum of about 175 to 185. The speed is not neccessarily 10% greater but the kinetic energy is 10% or more greater. 168 fps shooting 500 grains=about 31.3 ft pounds. 176 fps shooting same arrow =about 34.3 ft pounds. Steve

Hi,

A coworker asked to see a picture of a "Perry Reflex", so I did a yahoo search hoping there might be a picture someone had posted. We saw this thread, and I thought I should help those on this site understand a few things better.

"What advantage does a Perry Reflex give to the bow?"

Some advantages are:

1) Maintains a high energy profile better. 2) Stores a little more energy per limb mass. 3) Shares the work load over a greater surface area with a narrower bow. 4) Allows manipulation of surface stresses of the belly and back of the bow.

If used properly, it allows you to build a lighter bow that is easier on the shoulders, while maintaining the same velocity of a traditionally made bow of heavier draw weight, within reason. (It takes more than 10% increased draw weight to gain 10% additional velocity.)

Some disadvantages:

1) Longer build time. 2) More variables to keep track of. 3) Tendency to flop tiller. (Lower limb becoming weaker from shooting a lot, due to more strain placed on the lower limb. This happens regardless of making the lower limb stiffer, longer, or shorter. and it does it more than a non reflexed wood bow.)

Prior Post: "In TBB1 it was described as a bamboo backed hickory. Bacically a backed board. No magic to it. Nothing new. No invention. No secret. It's just reflex. There is some thought that because the board is tillered so it can bend evenly when being reflexed, it's somehow a new finding. To me, that is assuming that bowyers before TBB were somehow ignorant to what they were doing.

Everything old can be new again if you close your mind to those who came before you."

I feel bad that this design is understood so poorly after all of these years. I have also been concerned, since the TBB Vol III was published, that many people would view me exactly as the person who submitted this post does. Steve, thank you for setting the record straight on that topic.

Years ago, Paul called me and wanted me to publicly defend myself because things had become nasty, but I declined. I didn't see any way to maintain any semblance of dignity in such a cat fight. When Paul, Tim and the others did the research on it, the concepts behind it had never been published. Those who made laminated bows felt slighted. Not understanding the principles behind it, they didn't understand what the difference was. I am afraid most still don't.

I believe I had to explain this to Rod and Chris Boyton on the P.A. site a long time ago. Before I re-explain it here, I want it to be understood that I hold Chris Boyton in high regard. I consider him a world class bowyer, and am very impressed with his work.

I restate here, in defense of Tim, Paul and the others, their pooled knowledge and resources had shown no record of these concepts ever being published.

Lets address this statement first:

"Basically a backed board. No magic to it. Nothing new. No invention. No secret. It's just reflex."

This statement pretty well sums up why so many people believe this was nothing new. It's just "a backed board." "It's just reflex."

When a bow is bent, the back stretches and the belly compresses. By reflexing a bow of full thickness before applying the backing lamination, there is MUCH more surface travel in compression on the back of the bow than you could ever get from thin laminations. By reflexing a thicker than finished dimension bow before applying the backing, the surface travel on the back of the bow increases exponentially with the thickness of the bow. It is basis for I beams in construction.

By moving the surfaces father apart, the surface travel increases exponentially making the beam much stiffer when bent or flexed. We have used the information that it was stiffer for hundreds of years. Understanding why it was stiffer, and looking for another application, is the key to understanding the "Perry Reflex." Bowyers can take thin laminations and curl them up into tight rings and they will still never come close to the amount of surface travel I can put into a "Perry Reflex." I thought Tim made this clear in his chapter of TBIII, but he may have assumed that people had read and understood what he had written to that point. Tim spelled out inner working limbs, but many, probably most, didn't understand the significance of the thickness of the bow being reflexed! They didn't understand the difference in surface travel.

Years back, Steve may remember, I was trying to teach how to use elastic modules, and someone who understood it, drew lines 1 inch apart on s stick of white foam rubber. He posted pictures of it while it was bent, so that the neutral plane could easily be seen . This same model is good for seeing surface travel.

So:

"In TBB1 it was described as a bamboo backed hickory. Basically a backed board. No magic to it. Nothing new. No invention. No secret. It's just reflex."

Really?

Once you understand the CONCEPTS behind the "Perry Reflex", and Elastic Modules, and the compression properties of the woods you are using or that are available, there are a lot more things you can do with a Perry Reflex than you can with a laminated bow.

Did you know?:

That with a wood elastic in compression, you can get away with a thicker bow before backing, and that it will hold more reflex?

That when you do use a thicker bow (what some call a belly lamination), that the finished bow experiences compression on the belly earlier, and greater?

There is a lot more, but I won't go into it here.

If you haven't heard this before, it could be because nay sayers never understood what I was doing in the first place.

I have always been happy to give credit where credit is due. Show me one place in our accumulated wealth of archery history where these concepts are written prior to Tim writing about it, and I will happily acknowledge it.

Do I think someone else in history knew and used these concepts? Probably.

Were they ever shared? Written? Not that I or anyone I know has ever seen.

Dan

For those who said that only the best bowyers would be able to "make" the difference, let me tell you it makes a huge difference in my bows, and I consider myself a pretty mediocre bowmaker, for various reasons. Let's just say that I'm only decent in craftsmanship and execution....

But I can see a pretty noticable boost in both performance and likelihood of successfully finishing a bow when I utilize the Perry reflex. My very first bows were boo-backed boofloo, and I can promise you that a bamboo flooring bow board is pretty dismal by itself, but viable and pretty fast when made in a tri-lam perry-style.

I notice a big difference with both really hard, heavy woods, and lighter, less dense woods. With light woods, I have , like the books says, made bows 20-30% narrower than single-piece stave bows of similar design, with similar amounts or reflex.

Quiverfull: That is a great graphic, and what you describe there is one way of doing it. I have heard reports, esp. on another site, of LOTS of European fellows doing just that, with awesome results. However, I think I understood well what Tim wrote in the TBB I, and what Dan Wrote above, and I am sure it is not the only way. Any time you force slats into reflex and secure them with glue counts.

The next level I want to understand is how thick the slats should be. I want to understand neutral plane and thickness ratios better for different materials, etc..

Springbuck,

If you really want to understand Elastic Modules, and what is going on in the glue joints, you need to get some foam strips of different densities and thicknesses, glue them together, draw lines across them at carefully measured intervals, and bend them. You will see what is happening internally as the lines distort.

This simple test alone would have removed the misunderstanding expressed in this thread.

I just taught a dozen scouts to make their own reverse twist strings, and bows from staves I cut not far from my house. Surface travel in tension and compression (Why and How a bow functions) and how to work with it, was the first thing I taught them, on a chalk board!

You will like this, 2 weeks ago, one of the boys came to me very excited, his bow soots farther than his friends compound! I am sure that there was a draw weight difference, but the wonder on his face that he had made a REAL, functional bow out of a length of a small diameter tree was priceless. ;-)

Dan

This screams build-along is anyone up for it. I'd like to see more detailed directions about the foam lamination demonstration. Heck maybe I'll get around to it once I find time to actually work on a bow.

Heck i'd like to know more. I can visualize what the foam demo would do and have read the bibles but, as always having someone who REALLY understands the concept explain and demonstrate is always the best way to learn. Thanks Dan....

Maybe ,not a good question ? Are you saying that the trick is finding the right density woods to lam together ? and in the correct sequence ?that is what will get the "BEST" performance? ie: hard back ,med.core,softer belly or vise versus,mixed a different way? This is for longbows,flatbows but not recurves,correct?

I have glued up quite a few bows in the Perry reflex style and each and everyone of them performed well. I made a caul from a 2x6 board and drilled holes at distances along the board. I then glued up simple red oak boards with hickory backings.I preshaped the boards but did not remove any material from the belly at all. The boards were glued up and shaped later. The Hickory was bias cut and in tillering I could remove material from the back and also the belly. All the bows I made in this method are still in business afer 6 or 8 years they all shoot well and with the exception of being a bit of a pain to tiller I enjoyed building them. John.

one other question.If you add Glass Lam. is all this cancelled?

I also made a Perry reflex Penobscot. Main bow was maple with Hickory backing and the little bow on top was Pacific yew. Turned out to be rather sluggish with the small bow attached. But what a looker. John.

I also made a Perry reflex Penobscot. Main bow was maple with Hickory backing and the little bow on top was Pacific yew. Turned out to be rather sluggish with the small bow attached. But what a looker. John.

Dan, thanks for coming aboard and explaining this. I believe I understand the principle, but my limited ability to absorb information is making it hard on me to understand what you are sayin, I musta had too much fun in the 70's.

This has got to be one of the best and most infomative threads I've read in a long time. Thank you. I'm going to print this out and re-read it many times and when I get home tonight I'll be cracking open the bibles and do some studying. Can anybody tell me exactly which books and chapters to turn to?

Str8, matching backs to bellies gives us an added possibliltiy for bonus performance. String backs will often prevent failure in a bow which is our usual first objective but they will also "mask" set a bow is taking. A strong back can pull a bow back into reflex even though the belly fibers are pretty well crushed allready. Most woods tend to be stronger in tension than compression. Sometimes finding a backing that is slightly weaker than the normal back on a particular wood pays off by keeping the compression up on a bow. Hickory backed ipe is a good example of this. Ash backed osage is another one. Many times I have cut a bow in half after shooting quite a bit, seperating the back from the belly. Not uncommon to see the belly go deep into deflex with lots of set even though the bow appeared to have maintained good reflex while it was still in one piece. I use a little different method while tillering a bow out that doesn't rely on visual set, I simply measure the draw weight at early stages of draw on the tiller tree and as I advance the draw length check to see if I am getting any drop in draw weight just due to longer draws. It will show in in draw weight before it shows up in set taken. Steve

Sorry for slow response, I work double shifts.

Raymo,

I hope it helped. I don't have Tim's gift with explaining ideas. It was difficult for me to even put concepts into words when I first tried to share what I was doing with Tim. It's a good thing Tim is smart and quick to visualize things.

Str8sh2ter, "Maybe ,not a good question ? Are you saying that the trick is finding the right density woods to lam together ? and in the correct sequence ?that is what will get the "BEST" performance? ie: hard back ,med.core,softer belly or vise versus,mixed a different way? This is for longbows,flatbows but not recurves,correct?"

Sorry. There are a lot of concepts in that post. I will try to do better. Let me separate them a little and it may help.

The foam model is just to teach surface travel at first. Until we gain an understanding of how much difference thickness makes in the distance the surfaces travel, it will be hard to learn the rest. A single piece of 1 1/2" or thicker foam will help us see.

Draw accurate lines at 1 inch intervals across the length of a 12 inch piece of foam. Bend the tips down a couple of inches and secure it in this arch. Measure the surface travel of the arch on the compression side and tension side of the arch, (the variation from 1 inch between the lines.) Repeat the process with a 3/4 inch strip, and measure (Not an unreasonable thickness for a Perry Reflex bow limb before glue up.) Once you see the difference in the surfaces travel reducing the thickness only by half, you will begin to understand the difference between a laminated bow, and a Perry Reflex. Now repeat the process with a 1/16" thick piece of foam (not an unreasonable thickness for wood lam bows. Could you even measure the surface travel?

Now laminate 1/16" foam strips in a form with a re-positionable spray adhesive or other thin soft adhesive that will not interfere with the test, 7/8" thick. First make marks on the edges of the belly and back. Now bend this reflexed foam until it forms an arch in the other direction. Measure it first in the flat position, and then bent into an arch. When this test is measured against a 7/8 inch thick Perry Reflex foam (3/4 inch thick belly, 1/8"thick back) you will notice that the surface travel of the laminated foam compressed earlier on the belly. Why? Because the belly lam of the laminated bow experienced very little surface travel before it was glued in place.

If we want to see the deformation (strain) of the working limb of the two "DIFFERENT" reflexes, draw lines across them and you can see the difference in the "planes of strain." Sorry, I don't know another term to accurately describe what you will see.

Once we see and understand this, we are ready to try different densities of lams. The different densities are only to give an idea of what woods with different elastic modules and compression strengths will do. The problem with generalizing them by density and compression strength etc., is that it doesn't reflect how elastic the materials are in the real sense, (able to recover from compression and tension strains without breaking down) only how much force one modules of lam will apply to another. (Or resist as the case may be.) That said, it still helps to understand this.

Soooo, a hard to stretch backing may still be a good choice on a less dense belly if the the belly wood is elastic. Matching the properties is what Steve is talking about I believe. It depends on what you are trying to accomplish.

Lam bows and Perry reflex bows both have pros and cons, but you have to understand the difference first.

I am sorry I can't accurately explain concepts in a condensed form. I end up getting so wordy that the reader is lost (baffled) before I finish an idea.

If you made it to the end of this, you are truly patient or bored. ;-)

Dan

Spider1,

Tim writes about it in TBBIII in his chapter bows of the world. Don't have it close to hand. Hope this helps.

Dan

I vote for a build along too.

Str8sh2ter,

"one other question.If you add Glass Lam. is all this cancelled?"

This is a good question. Sorry I didn't get to it yesterday, but I had been awake for 22 hours and it was hard to think.

I don't make a lot of glass bows. (I don't like working with the glass) I am not drawing on a lot of experience here. How I understand it, can be visualized this way:

If you used a strip of foam for backing, and glued up a Perry Reflex using a solid fiberglass bow (Belly lamination), would it hold reflex after you unclamped it?

Why?

The the foam does apply force to the solid fiberglass belly, but it can only apply force equal to its elastic modules and compression strength. If we were to reverse the positions, this would still hold true. It appears to be a conserved principle. Wood will differ from the foam only by degree. A lamination can only exert or resist force equal to its elastic modules and compression strength.

Str8sh2er, your question shows than you suspected something like this, and you were right, to a point. Wood differs from the foam in this example only by degree. You can't exert force on the belly or back grater than you weakest link.

Would the internal wood core lamination be able to apply enough force to the fiberglass to compress a glass belly lamination? For most wood cores, probably not to much of a degree. So where is the "plane of strain"? Where is the movement taking place? What is deforming and storing energy? And eventually, what is breaking down? The glass? Or the wood core glued to it?

Don't get me wrong, the glass still has force applied to it, equal to the wood core's elastic modules and compression strength. Comparing ratios of modules and compression strength of the core to the glass will give you the degree to which a wood core can act upon the glass belly or back.

I have never studied, read about, or visited any discussion on glass laminated bows online or elsewhere, and don't know if this is common knowledge or not. And as I said before, I am not an expert. I just don't see the physics changing with the modern materials. Only the degree from the increased modules of the materials.

Dan

The idea of surface travel is one I do think lots of guys making wood bows don't understand fully, but that I have worked hard to "get", because I found out early on that some of my thinking was incorrect when I first started. Elasticity of materials is absolutely important to bow design, Dan, as you say. I have understood this in general terms for years, but I am still working on being able to predict the specifics...

Stuff like, "If I put a bamboo back this thick on a piece of hickory this thick, what will happen? Where will the neutral plane lie? How much travel in stretch and compression will the back and belly experience?" That is where I still have to feel my way through every bow, watching it on the tree and figuring it out as I go along. I know well how to move the neutral plane back and forth, etc, just not how to use that to decide how wide to make a bow and what angle to trap it to, etc..

I was thinking the other day, that in addition to Tim's and Paul Comstock's rules on width for certain woods, and Steve Gardners Mass Principle, that wee need a chart for how much directional surface travel different species or different weight woods will tolerate. After all, that is really what Tim's mantra about making bows wider to "take the strain" is all about. It is actually keeping them to reasonable thicknesses at reasonable weights to avoid excessive surface travel, from which the wood cannot return to shape.

BTW, Dan. I go to church with a guy named Wuthrich, who says he works with you. He saw me idley sketching a bow during meetings. So we're neighbors.

Springbuck,

So you are the one Wuthrich was telling me is hooked on building wood bows. Nice to have wood bowyers in the neighborhood.

I told Steve Gardner I never understood why surface travel was never addressed directly. And you are exactly right about width and surface travel. Tim once asked me why I didn't build my bows shorter, wider and thinner. I told him it would throw off the ratios for a Perry Reflex, (it hadn't been named that at the time). For the materials I was using, it was better to have the bow closer to finished thickness before gluing it up, and I needed the thickness to get the surface travel I wanted.

As I mentioned earlier, when I teach new bowyers, I teach surface travel, how width adjusts thickness to reduce or increase surface travel. Surface travel and thickness is how I learned wood bow construction when I was in college. I was making Bingham bow kits and noticed how you can roll up a thin lamination into a small circle without it damaging the wood.

Steve and I look at mass from different angles, but to the same conclusion. I look at it in terms of density of the material being compressed and stretched. While Steve studied tillering and how to tiller a bow to achieve the perfect mass to width ratios, I looked at the dry density of the wood to predict the maximum thickness and surface travel, achieving the correct mass. Less dense woods (such as Eastern Red Cedar) have more surface travel, but when built to their breakdown point, they have the same mass as a denser wood bow of the same design at the same point. (IPE for example.) I wrote about the total mass being the same for heavy and light woods in TBBIV and my PA article on building your own flight bows and Tackle.

I think Steve's approach it more practical. His method of getting there is better, and never occurred to me. Steve is brilliant!

The bottom line of why mass works this way is defined by a term I called "Critical Mass". Every wood has a maximum distance of surface travel it will stand. Whether it is red cedar or ipe, most bow woods tend to reach this critical mass when surface travel compresses the same mass of wood. Red cedar has more surface travel, and compresses more material, but even though the volume of wood compressed is greater than ipe, the mass is the same at the breakdown point. This is for correct moisture wood, as the lignin that is responsible for this affect becomes higher in compression strength linear to it's moisture content. (Search mechanical Properties of wood, lignin, and compression properties of lignin, moisture, if you want to know more.)

So the bottom line is, surface travel is what we are designing to. When it is designed to correctly, mass will be close to the same for the same design with different bow woods.

That is enough for now. Sorry, I get carried away and get real boring.

Dan

no need to be sorry. i enjoy reading this suff.

chris.

Dan, one of the enjoyments of discovery involving all wood bows is the unseen or unspoken collaberation we go through. I remember several years ago you ran a series of posts on primitive archer and I enjoyed your approach and logic. Outside of the online groups I hadn't read much up until that time and used theories of your self and Baker in my own work. As individuals it would be near impossible to explore all avenues but by recognising and accepting theories of a few logical builders such as yourself it allows us to move on into other areas without having to reinvent the wheel to get there. I have to admit that the last year or so I have just plum run out of new things to try. Fine tuning existing theories seems to be where most of the progres might be had these days. I also think possibly identifieng optimum belly to back matches in a wide variety of woods may yield some results. Lately I go out to my workshop and sip on my coffee just searching for something different to try, often just wandering away with a touch of frustration. A few years back I would go to bed and dream up something new, be up at day break and hit the ground running. I think they call that a creative block! LOL. I still thourouhgly enjoy my self bows which are rough and crude. Steve

I'm afraid...I dont understand surface travel yet...but I still find this thread incredibly interesting and hope to learn what it is sooooon!

Dan or Badger... that first drawing that was put up, where reflex was glued in once... then it was flipped and reflexed the other way with the backing... is that NOT accurate?? Or is that what you are doing with a Perry??

Ernie

Ernie,

I don't build bows the way it is shown at the top. By using a thicker lamination, there is not one glue joint fighting another, canceling out some of the potential. If you want more surface travel on the glue joint, the belly needs to be of a wood elastic in compression. The belly will compress earlier than it would if the belly lam were it's finished thickness at glue up.

Dan

I don't quite get the importance of reverse tillering.

Would the method for inducing reflex that Dean Torges uses in his video "Hunting the Bamboo Backed Bow" be an example of Perry Reflex? He does not reverse tiller, but he does "pull" the bow into reflex to glue it up, -- no steam or heat -- and he does taper the limbs to enable them to do that.

Could a mechanical engineer give this stuff a thought - maybe it has something to do with reverse internal residual stress during the construction.

For the layman, define surface travel. Which surface(plane)are you referring to? Back of bow, side of bow, Belly of bow? What is meant by the term travel? stretch, compression, flexion? Sorry I got lost in your terminology. Thanks!

The reverse internal residual stress Ed Bock mentioned is what Tim Baker describes on p. 91-95 of TBB3. Tim's explanation is that the advantage of "Perry Reflex" comes primarily from two things: 1) mechanical bending of the wood into reflex instead of steaming or heating and bending, and 2) the opposing tension and compression applied in the glue-up "forced the bow to store a good percentage of its energy deep inside the limb instead of primarily at belly and back surfaces..."--quoted from the book). Jim

Thank you all for a great informational thesis! This one I will have to STUDY.

Bill

Tell there won't be a quiz Friday...LOL

Dan,

In no way is your post boring! I will add this to my favorites, for further review.

It would be great if you could do a step by step build along laying out the concepts you have detailed here. It would be of great help to someone lacking essential experience such as myself.

Like my flight instructor said many years ago, "Once you have it explained to you, you are just dumb enough to be a good pilot."

Thank you, Dan, for your time and explanations.

Dave

Thanks Dan, think im gonna have to buy some foam to properly understand it though. Sounds like its worth the effort.

I too would love to see Dan.. or Steve.. .do a buildalong highlighting some of this theory...

E

Hey Dan, would it be good to use a spongy wood as a core on bows with carbon fiber backs and bellies? Jim

John Doc,

Surface travel is the distance the surfaces of the bow move in compression or tension when the bow is bent from it's resting position. By measuring the distance between the lines draw at a right angle across the 1 1/2" thick stick of foam, while it is bent, you can measure surface travel. Wood is compressed and stretched on a decreasing curve the deeper into the limb you move, towards a neutral plane. The surface will reach its limit first, hence we design bows to stay within the bows woods surface travel limits.

Zeno's Arrow,

Reverse tillering is sort of a misnomer to me. I leaned that bows that are thicker on one limb than another at glue up, will compress more wood at the glue joint and hold more reflex, leaving the bow asymmetrical, when unstrung. For the best symmetry, you need to have the limbs match thickness for thickness.

Dan

Dan, thank you for clarification. Also for your research and sharing this valuable technology.

Dan sez.. "I needed the thickness to get the surface travel I wanted." Now THAT clears up a couple things for me. I had assumed that glueing up two slats in as close to finished thickness as possible would yeild the greatest benefit. Hypothetically, if a wood were exactly equal in tension and compression strength and elasticity, then two lams, each exactly half finished dimensions, would be best. Correct me if I'm wrong, but it follows that if a backing wood is stronger in tension than compression, then the backing is made thinned than the belly. That agrees with Baker's section in TBBIII.

"most bow woods tend to reach this critical mass when surface travel compresses the same mass of wood." Another way of saying that a less massive wood needs to be wider-limbed, and a more massive wood narrower-limbed. High elasticity/light weight woods like ERC or yew, might thenbe made a little wider AND a little deeper for the same effect. Yes?

"the lignin that is responsible for this affect becomes higher in compression strength linear to it's moisture content." In other words, the compressive strength of lignin increases linearly, inversely proportionally as moisture content decreases. Strength goes up as moisture content goes down.

Reverse tillering... I have acheived best results by having the slats close to finished thickness, like Dan said above, AND as close to the tiller I am shooting for. If you took two boards and neither tapered or narrowed them and glued them up into reflex, most of your bend would be in the middle, so the outer limbs would take little advantage of the technique. I think the point Tim was trying to make, was that you need to pull the lams into reflex in a way that makes the reflex work for them throughout the limb.

Let me muddy the water with diagrams.

resize....

Hmmm, I'll try to get it readable.

Springbuck, "Hypothetically, if a wood were exactly equal in tension and compression strength and elasticity, then two lams, each exactly half finished dimensions, would be best. Correct me if I'm wrong, but it follows that if a backing wood is stronger in tension than compression, then the backing is made thinned than the belly. That agrees with Baker's section in TBBIII."

Because of the boredom factor, and the time and space it would take to fully explain everything in detail, what I have presented here is often over-simplified. To this point, what you have stated here is mostly correct. 50 50 lam thickness would never be ideal because of the decreased surface travel at the glue joint. Just as 4 lams of 25% would lessen the surface travel at the glue joints. If you really want to see and understand what is happening, get some foam and start drawing lines. Laminate 1" thick foam lams out of foam, where the neutral plane is in the center, into Reflex. Bend, observe, and measure. Then glue 1 3/4" thick to 1/4" thick. Compare them.

Then use foams of different densities. What you are going to learn, is that in practice, the neutral plane isn't always where you would expect it to be. This is due to how laminations of different strengths apply force to each other. In an oversimplified model, the neutral plane doesn't shift as far to the stronger lamination material as it does in real life application. This is because the models people use are STATIC! When you introduce potential energy to the laminations before they are glued together, the affects of the interactions between different modules are amplified . I don't know if anyone understands this, especially since so many people don't understand the difference between a Perry reflex, and a traditionally laminated bow. "("most bow woods tend to reach this critical mass when surface travel compresses the same mass of wood." Another way of saying that a less massive wood needs to be wider-limbed, and a more massive wood narrower-limbed.)"

What I am saying is that lighter bow woods will be both wider and thicker at critical mass unless they are overbuilt in width.

If you look at the 2, 35# longbows in my TBIV chapter, you will see that the cedar bow is wider and THICKER, not thinner. Don't confuse the adjusting of width to stay within maximum surface travel with Critical Mass. Those 2 bows are the same mass at the same draw and the same draw weight, because the mass of wood being compressed is the same! The Red cedar bow has much more actual surface travel, but it doesn't compress any more mass.

Dan

Oh, yeah, I meant my little drawings to be oversimplified as well. The first one was just to help explain surface travel, but I can't get the little specs big enough to be visisble. And I do need to do some foam models, I'm sure.

However, since we're talking, why do you say that "the 50/50 lam thickness would never be ideal because of the decreased surface travel at the glue joint."?

Obviously if you have a thin backing and a thick belly, the thicker the belly, the more surface travel it will have, expecially at the glue line which is the "belly" side of the initial bend (into reflex).

And I know that since woods are generally stronger in tension strength than compression, the glue-side of the belly will compress more than the belly side of the belly slat will stretch. So I'm good there.

But, Baker says that the increased stiffness/deep limb energy storage comes from the two slats resisting eachother at the glue line: the backing under tension trying to relax back to neutral and the belly under compression trying to extend back to neutral.

Now I actually know this doesn't exist in the real world, exactly. But if the slats were 50/50 and perfectly balanced in tension and compression (I said "if"), then at the glue line the surface travel would be equal (one stretched x amount, one squashed x amount) and it seems to me that the DIFFERNCE between them would promote that inner-limb energy storage we are after.

Now in the real world, not many materials will act that way, so we make our belly slat thicker and gain net surface travel that way.

So, does tension surface travel count as much as compression surface travel, or less so? Is it just more difficult to get, since most materials are tension-stronger?

As I was thinking here I had this thought. Badger makes some fast bows, yes? And he also uses a much thicker bamboo backing than most. Many advocate 1/8" or even less. Steve has often posted that he uses 3/16 or even 1/4" thick bamboo. I had thought that the main benefit of this was decreased tip weight and that his tillering skills prevent him from crushing the belly, but let's take another look....

Bamboo is often 1.00 S.G. or higher at the surface, but the pith side is often pretty soft, not too far into the boo. Bending a 1/4" backing into reflex would, IT SEEMS, provide for a LOT of tension surface travel on that glue-line side. Then he pairs this with a slat of very hard,very elastic wood (like bulletwood, ipe, osage) which are both tension strong and elstic in compression. Seems like the best of both worlds, to me, but only because the materials and design are well matched.

Sorry, the ER is dead, so I got too much time to think. Take as long as you need to reply, Dan, and thanks for being patient with my inner 4 year old.. ;-)

Now, the method Quiverfull put up CAN work, right? It just isn't preferred. By your own reasoning, Dan, in the first step, there is only minimal surface travel, because the lams are thin.

IN thesecond step, it seems to me tha the inner lam will be under quite a bit of compression at the second glue line. Surface travel on the backing will be about the same, and the only place I see a loss is on the belly surface, which is under some, but not optimal tension.

It seems that if you HAD to use three lams, the way to do it would be to glue the belly/core into slight reflex, then apply the backing under more reflex, permitting maximum surface travel both on belly and glue line. OR, would it just be best to glue them straight in the first place?

You know how you get a little spring-back or relaxation off the form, the blank not matching the form exactly, but a little less severe? Well, when I used to make r/d boofloo bows I had the best success gluing the middle lam to the backing, then going back and glueing the belly on in the same form, and since the belly was usually thickest of the three, often as thick as the other two together, I would lose less reflex, which boofloo bows are famous for doing.

Some guys over on Paleoplanet are saying that they are getting good results with the stiffest, hardest wood in the center lam. Some glue core(thin) and belly (thick), into exaggerated reflex, then into the normal reflex with the belly lam. Seems to be ok to me, but I don't get the logic of having the softest wood on the belly. Input?

Badger, you out of ideas? Did you ever get around to messing with my idea about a longitudinally finger-jointed Perry Reflex? You know, thicker slats with deeply scored, matched, triangle-shaped grooves along the length of the glueing surface. I still think that amount of surface area in the glue line might make some difference.

"What I am saying is that lighter bow woods will be both wider and thicker at critical mass unless they are overbuilt in width."

Dan, I did notice the ERC bows thickness. However, this I may have had backwards. Some woods have lower strengths and higher elasticities. ERC, yew, juniper are the classic examples. I was thinking that lighter woods had to be wider to GIVE you enough "critical mass", but thinner so they don't get too much surface travel (in one direction, compression, say). But it seems you are saying wider, yes, but thicker, too so we DO get a little more surface travel. Then we are relying on the fact that we started out with negative net compression (same as belly under slight tension) on the belly to protect it.

So, this leads me to a "would this work?" question. Let's say I have a backing like hickory, 1/4 the limb thickness or less, and a highly elastic belly wood like ERC. Since ERC is a little tension weak, if I put a strap, like a lumber banding strap on the ERC BELLY side when cranking it into reflex, that would slightly increase the amount of surface travel in compression at the glue line, right? Good, bad, or indifferent?

How important IS it to have the post-glueing blank's belly in tension, and back in compression? Is that less important than having a lot of surface travel at the glue line.

I also want to explore how this all works with fabric backings and cable-bows.

Am I also gathering that backings with high strength and stiffness are preferred? I saw a bow once backed with ipe, which seems risky, grain-reading-wise, but wouldn't the inherent stiffness/strength of ipe be helpful in reaching closer to the "critical mass", if I'm using the term correctly? I just mean that ipe's stiffness puts more mass under more compression and more mass under more tension AT THAT THICKNESS than a less massive wood might. Thinness means reduced surface travel, stiffness means strong forces involved.

Whoooaaa Nelly!

Springbuck,

These are good questions. If you want me to just give you all of the answers at once, I will have a book here.

You are a quick study, so I am going to ask you some questions. The answers are already available from the concepts I have presented on this thread. Although, you would do well to get the foam first and run real tests before you answer. Actually "seeing it" answers most of the questions. "To this point, what you have stated here is mostly correct. 50 50 lam thickness would never be "ideal" because of the decreased surface travel at the glue joint."

Why would I agree with the placement of the glue joint with equal compression/tension materials, but question using finished dimension 50 50 lams?

You didn't define the real elasticity in compression and tension of the materials either. This would also determine what path you would take. As you already know, elastic modules and compression strength have nothing to do with how "Elastic" the materials are.

How is force transfered in shear force from one lamination to another?

I would look closer at what I posted for Str8sh2ter. After you study that, how does it relate to what the Paleo Planet people were saying? What limits the amount of force that can be transfered from one lam to another?

What function do limb cores perform? Are they just to hold the surfaces apart?

If on one side of a glue joint you have pithy bamboo, and on the other side a very strong, dense Ipe, how much of the force is transfered to the Ipe? What is straining and breaking down? The pith, or the Ipe? Or is it the dense shell of bamboo on the other side?

"How important IS it to have the post-glueing blank's belly in tension, and back in compression? Is that less important than having a lot of surface travel at the glue line."- "How important IS it to have the post-glueing blank's belly in tension, and back in compression? Is that less important than having a lot of surface travel at the glue line."-

My questions for you are:

How elastic are your materials?

What are you trying to accomplish?

Do you believe there is one application that fits all needs? All designs?

You are on the right track with the Steel banding and the Red Cedar, but couldn't you accomplish the same thing with just having the belly thicker at glue up? "Am I also gathering that backings with high strength and stiffness are preferred?"

Would you back Black Cherry with bamboo? Why?

As you pointed out, matching materials is important. Matched to what? Do you know exactly what the combination is going to produce in the transfer of force? On the back and Belly? Foam testing will help you see.

I "didn't" say that reverse laminating one or more thinner laminations before bending it into reflex and gluing a backing lam didn't work at all. I said that I don't do it this way because it is not as efficient. (Not precise words, but precise meaning) After performing an extra glue up, it still is not as efficient as just using a thicker belly.

Asking good questions is the key. I had hundreds, and no where to turn. You are starting where it took me decades to get. If you keep asking good questions, I will be a novice by comparison at the end of your career. I don't think we have all the answers. Far from it. There are at least 3 important concepts I presented here I have never seen or heard discussed anywhere else, so we are far from knowing it all.

Dan

LOL... Take your time, Dan, I just appreciate the priviledge of being able and allowed to pick your brilliant mind! lol..

I have two jobs 4 kids, limited tools, and a handicapped daughter, so I get to spend a lot more time building bows in my head and on paper than in my garage. Thus, I can't try all the things I want to try as fast as I'd like to try them. If I could I'd go find out for myself instead of bugging you. THANK YOU so much for your willing patience, Dan....

Dan: "You didn't define the real elasticity in compression and tension of the materials either." Sorry, I thought I had, but may have used the wrong terms. I was using a hypothetical that doesn't exist in wood, to my knowledge, of exactly equal tension/compression strengths. I meant to imply that the amount of surface travel, actual distance of movement, in stretch and compression WAS the same. Sorry if I muddied the water.

Now, all the stuff in the the post to Str8sh2ter with the foam model, has always made sense. I have seen it in real life and easily in my head. I read every word and understand every word, I think...I understand how multiple thinner lams have both less individual , and less net surface travel.

Dan: "How is force transfered in shear force from one lamination to another?" If I understand the question, then I don't know the answer, exactly. What I do understand is that in a "normal" limb an inordinant amount of the tension and compression, hence most of the energy storage, occurs in a superficial layer at back and belly, espceially on the belly side in most limbs. If Perry reflexed, the same amount of material is stiffer (get to that in a minute).

Now, allow me to switch terms here a minute. The back surface, which is usually under TENSION as a bow is bent, starts out in NEGATIVE TENSION (compression), and the glue line prevents it from GOIng into tension until it has bent much farther than a "normal" limb would have. The inverse is true of the belly surface. IT starts in negative compression and must travel further before it feels that concentrated compression at the surface. This causes material which is deeper in the limbs, under that "layer" that usually feels the strain to take some portion of the strain before the surfaces do.

Dan: "What limits the amount of force that can be transfered from one lam to another?" I'm assuming, the strength of the glue line will give you the limit due to failure. Otherwise, the position of any coronal plane relative to the neutral plane.

Dan: "What function do limb cores perform? Are they just to hold the surfaces apart?"

In a standard limb, since MOST energy is stored in a very superficial layer at the surface, I might say, yes.. almost.

But not so in a Perry limb. The design forces internal portions of the limb to store energy. It suddenly strikes me that a Perry limb may not have a single neutral plane. Perhaps either there is a wider semi-neutral grey area, two neutral planes (one for each lam).

More likely, it seems that the areas inside each lam, which WERE the neutral planes (of each lam) when the lams were reflexed are now working. In my mind's eye that makes both neutral planes TRY to move closer to the glue line, but the opposing tension/compression forces resist that. I don't know if the NPs are prevented from moving, but it seems that at the least they are resisted strongly.

Dan: "If on one side of a glue joint you have pithy bamboo, and on the other side a very strong, dense Ipe, how much of the force is transfered to the Ipe? What is straining and breaking down? The pith, or the Ipe? Or is it the dense shell of bamboo on the other side?"

OK, this involves the next question heavily, but I'll try not to be redundant. First, if I bend "pithy" bamboo and dense ipe into reflex and glue, it seems to me, like I said in my post about Badger's thick backings, that the bamboo's pithy side is weak enough in tension to allow for a good deal of surface travel. The ipe at the glue line is compressed somewhat.

Now, the bamboo wants to lose that surface travel and return to neutral, but the ipe won't allow it, and vice-versa If we bend the whole limb, and the glued surfaces are resisting each other, then in order to bend, either the surface of the backing needs to stretch and/or somewhere material has to compress. The compressed ipe near the joint will stay that way, held in place by the glue line, but it WON"T compress much further because it is in an area of the limb where "travel" is minimized by geometry. The ipe belly is in slight tension (negative compression) so more actual bend in is needed before it begins to take compression strain, but somewhere deep in the limb wood which usually only travels a tiny bit is now being forced to take a lot of both strain and travel.

In my mind I see this compression during the draw starting just behind the glue joint and sort of rolling back toward the belly as the limb is progressively bent until most of the thickness of the belly lam is under about the same compressive load AND amount of travel. Hence the Baker theory that Perry reflexing "actually relieves limb strain while seeming to increase it." (TBB III)

I asked: "How important IS it to have the post-glueing blank's belly in tension, and back in compression? Is that less important than having a lot of surface travel at the glue line."

Dan answered: "My questions for you are: How elastic are your materials? What are you trying to accomplish? Do you believe there is one application that fits all needs? All designs?"

I think my original question was poorly presented.. I was really asking if having net travel in tension AND compression for each lam is vital (this would help to relieve surface stresses on both back and belly, and allow for a lot of net surface travel at the glue line.) Is what is happening at the glue line, or in the glue line AND the surfaces together what counts?

No, I don't believe the same ratios and designs would be ideal for all materials. I would not back cherry with bamboo, as you say, because bamboo would simply overpower cherry. However, a Perry reflexed cherry/boo bow would likely take the abuse longer than a straight cherry/boo bow. The straight cherry boo design would concentrate all the crushing leverage the low-stretch bamboo can muster on the most superficial layer of cherry belly. Dan: "You are on the right track with the Steel banding and the Red Cedar, but couldn't you accomplish the same thing with just having the belly thicker at glue up?" I think so, but this goes back to the question two paragraphs up. A thicker belly lam would compress more,but would also stretch more on the belly surface. If the travel att he glue line is more important, then the banding idea has merit, but if thhaving the belly under tension counts too, then both or either have merit.

If the backing is THINNER, then net surface travel is minimal and we rely on the belly to achieve the travel. But if the backing is thin and stiff, then the tension and compression strains are high, in spite of low surface travel, see? It makes a powerful attempt to return to neutral. If the backing's tension strength matters most, then this is less important.

Dan, please don't feel obligated to spend a lot of time on this. Sometimes just framing the questions is enough for me to "get" something. But I hope this is REMOTELY as interesting and entertaining to you as it is to me. I hope to finally meet you someday soon and shake your hand for the help you have given me and others.

I think it was Albert Schweitzer who said, "Small minds talk about people. Mediocre minds talk about events. Great minds talk about ideas." Thanks for the ideas, Dan.

Springbuck, between you Dan, and the foam rings from my Uncle's pool I am starting to get this concept of Perry Reflex.

Even if I did ride the short bus.

My Aunt seems to have concerns about my recent fascination with foam rubber and magic markers though.

I almost hate to admit it it but I have been using the perry reflex for so long I just quit thinking about the why. I spend a lot of energy figuring diferent things out but the perry reflex thing I have always just kind of excepted I guess. I can say for sure that I get a consistent 10% boost in stored energy for the perry relfex, along with other benefits that come form the designs we use it with. I can't say with any authority how much better it is than standard laminations because my experience is almost soley limited to simple backed relfex bows and self bows. I do often use thicker boo backings than normal with what I feel are good results. The thicker backing tends to maintain the relfex better in my opinion but only where the belly wood can stand up to it. Banboo tends to work mainly at the surface forcing most bellies into compression, the excess bamboo I feel simply acts like a core. Steve

Steve, I've admitted before how I build more bows in my head than in real life, but I do get a few done. Picking this stuff apart just helps me get nuances down. I understood what Tim wrote in the TBB's right away, but want to be able to maximixe that understanding, you know??

for instance, I have backed many bows with fabric, just tillering them, tying th tips into reflex and adding the backing. That seems kinda like the same thing; the backing holds the unstrung bow in reflex and seems to force the internal limb to store energy when drawn. BUT, I can't tell if that is the same, or less effective than a stiff backing with a little more thickness to it like boo or hick'ry. See?

I do know that when I made boofloo bows, I STARTED with less reflex and ENDED with the same amount or more if I backed a thicker slat, rather than making a tri-lam. I also have backed woods with bamboo that other people told me were a bad idea, but as long as I Perry reflexed em, it worked, and I often ended up with reflex held at resting on bows where the belly wasn't "suitable"

Now I have all these questions. If I trap the lams before gluing, is that even better? etc.. all the ones above. I can get them answered for myself by making bows, but not as fast as I'd like... So I'm glad for the help.

I want to be able to turn out a 180 fps, 10gpp @28" bow, suitable for hunting (rugged and not touchy) at will...

Steve, I know what you mean by picking things apart. I have been know to build 100 bows are even more just to test out one nuance of a theory. I was laways afraid to start trying to figure out the nuances of the perry reflex for fear it would send me to the looney bin. I never really thought about the glue line storing energy as much as it tends to take on the characteristics of the stronger wood it is glued to. I have played a lot with matching backings and bellies, I feel there is a good worthwhile science there in knowing which match up better for different applications. Very frustrating when I have one of these creative blocks like I have been having. Started creeping up on me a couple of years ago and has gotten to the point I am lucky to put out one bow a month. Just can't think of anything new to try. Steve

Steve, did you see my suggestions above? I've written 3-4 things on this thread it will be years before I get to, but I'm curious about.

Specifically, remember the thing with the finger-jointer used longitudinally? I'm still curious what difference that would make.

I've been looking for how to use heat treated limbs in reflexed and R/D bows. I was worried that cooking a glued up bow will kill the glue, and that getting a cooked slat in the form might crack it on the belly, OR that it would add less Perry-ness to it. I think I solved that with the banding strap idea.

I'll PM you the rest, if you like...

Badger, (I think we have 2 Steve's here?)

Try using a bow that acts like a car leaf spring before backing. A very thick bow. Make sure the belly wood is elastic. As soon as it is unclamped, much of the reflex will be gone until you tiller it to finished dimensions. The belly feels compression earlier made this way.

Seeing what happens with the foam models, will change you view of cores. Using different densities of foam glued up in different scenarios allows you to see what is really happening. I think you would have fun with it. I bet it jogs that block loose.

Lombard, "My Aunt seems to have concerns about my recent fascination with foam rubber and magic markers though."

It helps a lot, doesn't it!

Just remember that in a Perry Reflex, one surface is compressed, exerting an expanding force, the surface it is glued to is stretched, exerting a compression force. The distance the surfaces travel, and the modules of the materials used is the key to balancing what you are trying to accomplish.

Something to remember:

If a 1 1/2" thick strip of foam is glued to the surface of a 1/16" thick strip of fiberglass, the surface travel on the surfaces of the high modules fiberglass, (small to begin with) wouldn't be perceptibly different from it's surface travel without the thick foam glued to it. This only differs with wood by degree. The principle stays the same. A lamination can only apply force to another lamination equal to it's modules and compression strength before it breaks down. Perry Reflexing amplifies this affect.

Questions:

Since we now understand that the expansion and compression forces are working against each other in a Perry Reflex, where is the material distorted or strained?

Is there now one neutral plane? Does it depend on the strength disparity between the materials used?

On how many planes are materials strained, distorted?

The foam model helps us see the answers to these questions.

Dan

Yes, Badger and I are both named "Steve".

Dan sez.."The distance the surfaces travel, and the modules of the materials used is the key to balancing what you are trying to accomplish."

Had the part about surface travel long ago. Understood the compressive force and tnsion forces exist. I think maybe modulus/stiffness/strength of the materials is the part I have to understand better.

Dan did you read my whole post above? I went into a detailed "guess" about neutral plane shift and strength disparity...lol..

I have done some foam models, but so far they didn't seem better than the ones I draw in my head. And, if I can figure out how to get in onto the computer, I think UI have finally worked out a draw-able model for all to see. Wish I knew some drafting program or other...

Thanks again...

I been lurking. Very informative. Made me a foam model a week or so ago. Ain't quite got the presense of mind or mental stamina at present to really appretiate it all, but will in time.

Have experienced but not realized it was "Perry" effect in boo backed bows where I was lazy and didn't reduce the core thickness very much, or used a particularly game core w/ a softer backing. One constraint being getting such a glue up onto the form, without breaking it. And it makes it rough to do much r/d in the handle. But when you tiller it, it's like really strong tension wood. As you relieve the belly of wood, the backing takes up the slack keeping the net reflex even or increasing.

I hope you'll accept my apology Dan, if my comments here or over the years have misrepresented your position, or promoted the idea ego was at the heart of the naming "Perry reflex." Clearly you are a humble and generous man, have studied these topics thoroughly, scientifically, and enjoy the wonderlust of imagination and innovation which fuels our craft.

Springbuck, "In my mind I see this compression during the draw starting just behind the glue joint and sort of rolling back toward the belly as the limb is progressively bent until most of the thickness of the belly lam is under about the same compressive load AND amount of travel. Hence the Baker theory that Perry reflexing "actually relieves limb strain while seeming to increase it." (TBB III)"

A lot of what is written about the Perry Reflex, (like the naming of it) were Tim's ideas and were a surprise to me when I saw them. I don't remember talking with Tim about this statement he made in TBB III. 'Hence the Baker theory that Perry reflexing "actually relieves limb strain while seeming to increase it." (TBB III)" '

Tim's logic is good and the chapter is better than I could have done. This statement IS a bit misleading. It is true to a point, and under some possible applications. (like your equal compression strength, modules/ 50 50 lamination thickness question).

A more accurate description might be: The work load is shared by more of the limb.

Bamboo backed hickory, such as the one shown in the chapter, are not under less strain. If they were, they would not have the huge set on the belly lamination when the bamboo backing is sanded off. It would not require the care in tillering and matching thickness just to keep them from developing compression fractures on the belly.

Tim also saw the Perry Reflex as a way of successfully achieving extreme reflex and still holding together. We didn't talk about this either. I Find that there is a point of diminishing returns past a certain amount. Likewise, there are a lot of Principles I use that are not in the TBBIII chapter. (Using a thicker Bow (laminations) at glue up; the importance and application of surface travel; and the point I am trying to drive home here, That you cant expect a pithy or weak lamination to store or transfer more force than it's compression strength and modules allows! (This is why I kept bringing back to this point. THe pithy layer of the bamboo breaks down before it transfers much force, when placed between the hard outer shell and Ipe) I use to have an extreme example of this laying around the shop.

DMC,

I don't visit many sites. So you would be more aware of what you are referring to than me. Your apology is accepted, of course, and no hard feelings. It is not my way. Misunderstandings and misrepresentations are my own fault for not being more outspoken and participating in discussions. I hope you find the info here useful.

Dan

Dan, I have found when reflexing most bows unless making them excessively wide is that about 1 1/2 to 2" reflex is optimum as you suggested. Otherwise the wood breaks down too much. Strong backings can mask a lot of set. Steve

Steve, "Dan, I have found when reflexing most bows unless making them excessively wide is that about 1 1/2 to 2" reflex is optimum as you suggested. Otherwise the wood breaks down too much. Strong backings can mask a lot of set. Steve" That is where I glued the bows I use to sell. There is a point of diminishing returns for sure. Where it is depends on the materials used. I know you have used more combinations than I have. What was your best? Dan

like others i have the basic concept understood now ( did not before) I booked mark this and will continue to study. thanks for sharing dan.

chris.

Dan, I wished I could tell you a favorite. Possible ipe and hickory are very near the top of the list. Maple over maple is another favorite of mine. Steve

"THe pithy layer of the bamboo breaks down before it transfers much force, when placed between the hard outer shell and Ipe) I use to have an extreme example of this laying around the shop."

This was bothering me for a while, but I think I got it. I guess I think of breakdown and set primarily in terms of lost elasticity due to over-compression. When the pithy-er bamboo is stretched, I can't visualise it failing/breaking down, exactl;y, because the glue line doesn't fail, and the ipe is held in position.

I think I ran into this doing boo-backed boofloo bows, but didn't even see it until I tried a couple feeble boo-backed boo bows. I used thinned down boo for the backing, but the bellies were the same Moso I was using for backings, but the thicker-walled choice stuff.

If I put too much R/D in it, the glue line would hold and the reflex would hold, but the soft middle would break down. The point of the whole process is to get that inner stuff taking it's share of the load, right? Well, if I over did it, it would break down anyway, and even though the bow LOOKED like it was holding the glue-up, the middle layer had given up and was loafing again, and the bow would act like it was gonna be a real winner at first, but by the time I had it to full draw, it would have middling cast. That's what it seemed like.

Last question , Dan, and maybe Steve, too.

If you glue up a belly lam that is over-thick, I see how that benefits by pre-compressing at the glue line. Then the surface wood is in negative compression/tension at that point. Then, Dan, you say you are taking some of that layer off. I've done that, and I know what happens; the net limbtip reflex increases. Fine.

But, my main question all along deals with this. It seems that you have worked the belly closer to the neutral plane of the belly slat during form-bending. It seems that the belly lam is compressed near the glue line, but its new surface is under less tension. I THOUGHT that having the belly under tension helped keep the belly from failing, and that was part of the magic. I had been trying hard to get my lay-up as close to finished thickness as possible for this reason.

So, does the belly's tension surface travel matter less than the glue-line compression surface travel, the same, or not at all?

Springbuck,

Elastic in compression woods, matched with the correct thickness and elastic modules backing, will handle being thicker at glue up. It will begin to compress sooner, but not nearly as soon as a bow made from thin laminations at the same reflex.

Dan

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