From: GF
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Date: 03-Feb-16 |
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So in addition to man-made vs. natural-materials in bow lams, I've gotten to wondering about length...
Again, I'm thinking mainly about R/D longbows here, and wondering....
If you don't have a particularly long draw length to where you'd need it in order to avoid stacking, is there any up-side to going with a longer bow vs. a shorter one?
I know the shorter ones are considered "more maneuverable", but that they can also be described as difficult to shoot well...
Seems to me that a longer limb gives you more leverage, and that seems like it should translate into arrow speed...
And what about stability?
So how 'bout it? Is a longer bow likely to be a better performer? Right up to the point where it becomes unwieldy, perhaps?
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From: fdp
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Date: 03-Feb-16 |
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That is a REALLY complicated subject if you really get in to it. Then you have to start discussing how much of the limb is actually working limb versus being nearly static. The longer bow overall will always be a little faster simply due to the string angle at ANY draw length bein reduced.
This topic could...and has in the past, gone on for days. A 48 " bow can have the same length working limb as a 64" bow.
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From: scienceguy
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Date: 03-Feb-16 |
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I'll add my personal experience.......I think a lot has to do with bow design. I have a Toelke Pika that is 56" in length and a Toelke Whip that is a 62 incher. Both bows are 45# draw. For whatever reason, I shoot the Pika better than the Whip. I have not chronographed the bows, but they both get a 525 gr. arrow to the target pretty quick. I can't tell them apart. With my 28" draw, they both feel the same to me. The Pika is very handy in the treestand. I also have a 43#, 56" Centaur Dark Matter Triple Carbon Elite that I shoot the best of all. It is my go to bow at this time. I don't know if it is the carbon limbs, bow design, or whatever, but this Centaur gets the same penetration on target as my 45# bows. I think you just have to shoot a pile of different bows until you find the one that "feels" right to you. I'm betting that is the primary reason why so many guys buy and sell bows, and also why they decide to keep those special bows until death do us part.
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From: GF
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Date: 03-Feb-16 |
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Yeah, I was thinking about that...
Will probably have to assume very similar designs, or maybe something as basic as "Bow X is available in lengths from 52" to 62 - how do I choose?"; so assuming (dangerously!) that all lengths come off of the same form....
But can you explain the relationship between string angle and speed? I have a couple of gut-level ideas about how that might work and I'm not even sure that they are compatible with each other, so I would love to have it explained....
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From: Bowlim
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Date: 03-Feb-16 |
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When I look at speed I look at several things, not saying they are the only things, for instance material weight is a big deal, but one of those all else equal things. So obviously you have to store enough energy to fuel the arrow speed. You have to do it with materials that are light enough to allow the bow to respond quickly enough, beyond that it comes down to gearing, or what I also call string take up speed.
A lot of explanations of what makes bows fast, the whole Norb thing, are done in the context of all else equal designs. At any given time there tends to be a similarity in prevailing design, people want to know which model bow is faster. So they run the stored energy, note the velocity, and plunk the rest of it down to static hysteresis, the fudge factor. This is a valid way of capturing the difference between similar bows. But it doesn't explain why cam bows are faster than round wheels, or longbows.
And certainly the largest factor is how they are geared. Compounds use pulleys so that string take up is twice as fast. Obviously the early guys got it because they had up to 6 wheel bows, maybe more? Of course all that clutter did cause other problems and eventually the industry focused it's energies on two wheelers. Cams while storing more energy also significantly increase string take up. On a hybrid, the max flex point is further from the tip than some other designs, same with static recurves, this means a faster take up speed, because for a given increment of limb deflection, limb tip movement and string take up are amplified. But these designs also limit speed, for instance more weight is being moved by that unit deflection. And that is true in all cases, the same thing that speeds you up slows you down, so there are trade-offs.
Long limbs are a factor in moving the string. The limb tips move through a longer arc which takes up string faster for a unit of limb recovery.
There seems to be a correlation between things that speed up string take up and store energy. I don't know if that is a rule, or just a coincidence that one can note in certain cases.
You can't have speed with a slow string, so look at geometries that will move the string back to it's arrow release point faster than other designs.
An important concept to keep in mind is that for any technology level there is a limit as to how fast limbs can recover that is expressed in their modulus of elasticity. In composites this is a variety of factors working together. But there is also what I call a system modulus which is the rate at which the system respond to a released load, at the nocking point, and that is governed by the built-in gearing factors in the design as well as the factors we are used to hearing about like modulus, stored energy, and loses.
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From: GF
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Date: 03-Feb-16 |
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Sci-guy - that's what I'm worried about! I've shot the same two 'curves for EVER with basically no complaints.... This could prove to be a VERY scary path! ROFL
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From: oldgoat
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Date: 04-Feb-16 |
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My wife tried three different lengths of limbs from a bowyer one day, all the same model and draw weight and she consistently got faster speeds from the longest limb, who really knows though, that set of limbs could of been abnormally fast or the others abnormally slow! I've read, a longer lever is more efficient and more efficient usually adds up to more speed/power!
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From: flyguysc
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Date: 04-Feb-16 |
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I have a Centuar 62" with a 25" draw set @ 52# DW. Its chronographed @ 182 fps.I shoot this bow a lot and it is a tack driver. I also have a 66" Royal longbow by West Wallace set @ 57#DW.I can shoot the Royal a lot longer period of time verse the Centuar.Just seems smoother to me and less fatiguing.I have not chronographed the 66" LB.Maybe I will today,calling for rain here.
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From: dean
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Date: 04-Feb-16 |
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I think it may all depend on the bow. I have gotten a 68" Hill style bow to perform as well as a fast 66" Hill style bow at my less than 27" draw, actually it is faster than most 66" Hill style longbows, but it is not the total length that made that happen. If going with an R/D, I would stick with the makers suggestions, if they are a very experienced builder. Most of them know there product very well. About your 'very scary path'. A few years ago three recurve shooters and one Pete George longbow shooter were at a shoot. A fellow with a Robertson Purist walks up and they all check out his bow. They shot at the target they were at with their own arrow with the Robertson Purist. One said, "Really nice looking bow, but I am not sure a longbow can worth that kind of money." The others agreed. Then the Pete George shooter pointed how nice and tight all of their various arrows were tight in the kill zone. One said, "That's the best shot I've made all day". That is how Dick Robertson sells bows.
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From: camodave
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Date: 04-Feb-16 |
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The way I determine bow performance is by shooting arrows through the chronograph...I have yet to shoot a theoretical arrow with a theoretical bow
DDave
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From: fdp
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Date: 04-Feb-16 |
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Actually...there are certain aspects of physics and levers which (with all due respect to Sid and Bob) can't be changed. That being said, efficiency at a particular bow length, and particular draw weight can be figured mathematically to a certain degree. A bow is nothing but a fulcrum with a lever on each end.
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From: GF
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Date: 04-Feb-16 |
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To be honest, I was kinda hoping Larry would weigh in here ;)
But yeah... seems that the longer the non-working lever, the stronger the working portion can be. And with a longer lever, seems that you should also get more tip travel from a given amount of flex in the working portion. So that's Math favoring a long lever and a short working limb, but you'd have to have some experience with the materials to avoid overloading the limb... And if that were all there was to it, all bows would be built with long, virtually inflexible limbs that would be used to bend an extremely short, virtually rigid working limb some minute amount.
And it would probably knock your fillings loose with the hand-shock...
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From: KyPhil
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Date: 04-Feb-16 |
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For a Black Widow I have always found the longer limb was faster. Some of the really short bows usually have so much initial deflex that it doesn't matter if it has the same working limb lenght as a longer bow, it's going to be slower just from that. Look at some 48" and 46" bows, they nearly looked braced without a string.
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From: fdp
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Date: 04-Feb-16 |
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GF...you're right, sort of. Consider this, Jack Howard used exactly the same glass to wood ratio formula in his bows to match draw weight, and draw length. The Martin Hunter used the same limb design (length) for an untold number of years. Same can be said for the Howatt Super Diablo, the 56" Groves Spitfire Magnum (that was Harold's favorite by the way), the Savage Deathmaster, and the list goes on.
And no.....the bows won't necessarily knock your fillings out. The hand shock comes from having the bulk of the limb in the places where that doesn't happen.
I'm not making light of good bow design at all....far from it. But there is a certain amount of math involved, and when you get close on the paper, then you start building them and tweak the deign from there.
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From: badger
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Date: 04-Feb-16 |
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GF, I agree with you on the longer lever and shorter working areas. Most of the energy losses are in vibration and distorsion, the best way to limit the distorsion is to have more static limb. Energy storage gives you the most if it bends close to the center of the bow or closer to the fades. A lot of guys have moved used longer risers and power lams to shorten the working limbs but at the same time moved the bending portion further from the center. Shorter working areas solve a lt of problems and allow you to add more reflex with no loss of stability.
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From: larryhatfield
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Date: 04-Feb-16 |
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when I started designing bows for howatt, the base line was the fact that we could build any sort of lam I could imagine. single, double, triple taper, 72" long, perfect from the center to each end, all possible, and all used to make a limb react the way I imagined it should in many bows we built. simple math does not account for proper lam design. we did that because of the variation in fiber/resin load throughout a glass lam and the variability of wood. if you can control how the recurve opens or use only the last 9-10 inches of a r/d longbow limb, you get stability, good shooting habits and acceptable speed. I worked with a material scientist at Battelle Northwest Labs for several years and had access to equipment that could do many things to help determine what happens to a limb or an entire bow while drawing and shooting an arrow. the fact that any material I took there for testing was too variable to put an engineering value in use made it difficult for the scientist.
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From: longbowguy
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Date: 04-Feb-16 |
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So, it looks like nobody really knows. - lbg
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From: fdp
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Date: 04-Feb-16 |
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Larry Hatfield knows....he's got enough bow designs floating around out there verify it.
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From: longbowguy
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Date: 05-Feb-16 |
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So what length is best? - lbg
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From: larryhatfield
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Date: 05-Feb-16 |
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same design 1 bow 64, bamboo viper, the other 66", venom. the venom is faster even though the limb action is the same and the individual limb length is only 1" longer. same brace height. same draw curve.
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From: Mike Mecredy
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Date: 05-Feb-16 |
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There's percentage of the overall bow length that the riser should be that makes it perform the best.
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From: Harry Schultheis
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Date: 05-Feb-16 |
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I have made 15 r/d longbows from 58" to 66" on 3 different presses.Made with different materials including carbon. they all are chronographed with 10 grains per inch same brace height same shooter. The bows shot from 172 to 178 fps. the longer bows being a little faster. I feel that how a bow fits your hand and your style of hunting are more important than a few fps.
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From: GF
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Date: 05-Feb-16 |
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This is actually headed in a direction that I really appreciate!
Larry's post - "same design 1 bow 64, bamboo viper, the other 66", venom. the venom is faster even though the limb action is the same and the individual limb length is only 1" longer. same brace height. same draw curve."
Makes a lot of sense.
And Mike - on the ratio of riser:OAL - your Predator is available from 52"-62", so do they all come off of the same form? Not trying to get you to divulge any proprietary info, but to hold riser:OAL constant, I guess you'd need a different one for about every size that you offer..... OR you address that during tillering somehow, though I would think that riser length would have to be determined before anything gets glued up... but maybe you can do a bit with static vs. working limb ratios.. (???)
I should say that whatever you do, a lot of people who've bought your bows are very pleased with the results!
But for someone with a sub-28" draw, would the 62" be any quicker, smoother, more stable, or whatever other trait (good or bot-so- good) than the 58"?
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From: GF
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Date: 05-Feb-16 |
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* bot-so-good
NOT so good.
D'OH!
Harry - full agreement on a few fps. I don't know how many fps difference are required to have a noticeable effect on trajectory out to 35 yards or so, but given the ability to make "instinctive" adjustments in elevation ....
I guess I should re-phrase that as "a noticeable effect on elevation-related aiming error" (assuming the same shooter).
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From: George D. Stout
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Date: 05-Feb-16 |
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Larry Hatfield has been there and done that, and effectively, so anyone who would consider him less than expert, better consider again.
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From: roger
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Date: 05-Feb-16 |
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......yeah, I skipped all the way down to Larry's response and marveled as I read through it - the man is a bow building beast. He really was at the forefront of this stuff.
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From: GF
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Date: 05-Feb-16 |
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"Larry Hatfield has been there and done that, and effectively, so anyone who would consider him less than expert, better consider again."
Just for the record, I don't see where anybody here is disputing or discounting what Larry has to say.
And if anything I've posted here should suggest otherwise... mea maxima culpa!
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From: George D. Stout
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Date: 05-Feb-16 |
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GF, I was referring to the, "it looks like nobody knows" comment. But then I think he was probably typing that before he saw Larry's post. It's all good.
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From: longbowguy
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Date: 05-Feb-16 |
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Thanks Larry, for some factual info. I was trying to stir the pot.
We had lots of conjecture, lots of notions, some hypotheses, no facts. The trend for many years was to presume that shorter tended to be faster, all the many other factors being about equal. My suspicion has always been that maybe longer tends to be faster, but I have no hard evidence either, other than some long recurves and longbows that have performed well for me.
So many variables, so hard to prove anything.
Does anybody else have any evidence on the originator's question: "Is a longer bow likely to be a better performer?" - lbg
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From: badger
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Date: 05-Feb-16 |
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Most of the testing I have done or witnessed on longbows seems to suggest 66" and 67" longbows are faster. I haven't seen any tests on r/d bows longer than that.
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From: GF
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Date: 05-Feb-16 |
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At that length, I'd have to mind where I put my feet! Or go back to wearing steel- toed boots.
Actually, 66" is a LONG bow in my world. Taller than I am.
"In ma' Tony Lama boots."
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From: Mike Mecredy
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Date: 06-Feb-16 |
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GF, I actually have two different forms for the prairie predator, one for shorter models and one for longer ones. But the area where the riser is pretty much the same shape. But I do increase the riser length from fade out to fade out as I increase the overall length. I found that if I made the 62" with the same length riser as I did a 55" (for example) the performance suffered very slightly, but the amount of felt hand shock went up more than I cared for. I really don't dig hand shock. So yes, the riser length does increase as the length does.
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From: GF
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Date: 09-Feb-16 |
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But then the ratio of working to non-working limb would go down in the longer version off of each form.... more leverage... stiffer working limb @ same net draw weight.... shorter working arc.... more speed when you go long, right?
And FWIW, I'm with you on handshock.
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From: Foxallan
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Date: 10-Feb-16 |
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So as example let's say 68" seems to be smoother/faster than your 62"... For whom? Is that for the shooter with 30" draw or your 25" draw shooter? Or better for either no matter what your draw? I know Black Widow PLs have a suggested length depending on draw length so I assume they've done the research on draw to draw.
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From: longbowguy
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Date: 10-Feb-16 |
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For the record, I greatly respect Larry Hatfield, all of his many interests and contributions to archery and our conversations here.
And I respect that he has not given a short and simple answer to such a complex question.
But I do sense in the flow of responses that the old notion that shorter is faster may be wrong, that in US style modern bows longer tends to be faster, up to a point. So, it appears that we can get the smoothness and stability that comes from longer bows, and pay no penalty in speed, mostly. In short, depending upon design details, longer can be faster. - lbg
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From: Archergreg
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Date: 11-Feb-16 |
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I have always been curious as to what kind of data some of the large companies like Samick, WinnWinn,UUhka,and Hoyt have compiled. As Larry Hatfield eluded, using a lab to verify design is common practice.
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From: Tinhorn
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Date: 11-Feb-16 |
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So I built a new riser for my Martin Warf project, and raked the limb tips forward one inch to get more speed, as I had lengthened the riser over 2 inches. It worked great; this is my fastest bow at 10gpp by about 5-7 fps. It also has a 5 yard farther point-on than my longbow, both are 50-52# draw weight on my scale. It throws 172fps, the longbow is at 164fps. Same arrow.
Tinhorn
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From: GF
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Date: 11-Feb-16 |
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LBG - I thought Larry was pretty direct in saying that longer = faster - especially if that length increases the ratio of static:working limb length.
But that would be just the length of the limbs... Makes me wonder what the difference looks like if you put the same limb design on a different length riser but manage to keep the peak draw weight constant...
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From: Tinhorn
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Date: 11-Feb-16 |
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GF-
I got tired of finger pinch on an ugly Martin Jaguar riser, which is why I Warfed it in the first place; I lengthened the riser several inches to solve the finger pinch, and raked the limbs forward to regain the speed I lost by lengthening the riser. For every 2" of extra riser, I rake the limb tips forward another inch to regain the speed. It works every time!
TinHorn
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From: badger
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Date: 11-Feb-16 |
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Gf, if you wanted to test that out you could just lower your arrow weight to keep the same grains per pound. If you raked them forward to pick up the lost weight you would be changing design and no longer apples to apples comparison.
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From: sammy b
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Date: 11-Feb-16 |
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I am a weldor and logger by trade and I don't know about limb and speed. But I do have a crono and two Mad dog bows I checked speed on are the fastest I have checked shooting a hunting weight arrow.
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From: sammy b
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Date: 11-Feb-16 |
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I am a weldor and logger by trade and I don't know about limb and speed. But I do have a crono and two Mad dog bows I checked speed on are the fastest I have checked shooting a hunting weight arrow.
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