From: Silverhawk
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Date: 14-Oct-16 |
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Foam Core is suppose to be faster, pound for pound, than wood core and a lot more money. Does anyone know why it's faster than wood core. Just wondering.
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From: Bronco Archer
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Date: 14-Oct-16 |
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It is lighter than wood, so the limbs react faster to the release.
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From: Missedagain
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Date: 15-Oct-16 |
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I have a foam core R/D longbow. I've chrono'd it against same make and weight red elm cores. The speed difference was negligible. I don't think it is worth the extra money.
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From: Flygirl
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Date: 15-Oct-16 |
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Have a Zipper longbow with carbon foam limbs.I have chronograhed the bow at 46 lbs. at 28 " 525 grain arrow at 198 to 202 fps consistently.I think it's the quickest bow I have had at that weight.Not that it all matters but I do think,carbon foam are great limbs by Bill Dunn at Zipper Bows.
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From: Missedagain
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Date: 15-Oct-16 |
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Carbon makes the difference, not the foam core.
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From: badger
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Date: 15-Oct-16 |
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Flygirl, congratulations! You have the worlds fastest bow!
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From: badger
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Date: 15-Oct-16 |
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I have always wondered if a special foam core could be developed that would allow the bowyer to heat and then precision press the thickness of the bow for any draw weight he wanted
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From: Bowlim
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Date: 15-Oct-16 |
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Biggest advantage to them is that they may not change much due to moisture or other environmental factors, though I wouldn't want to put high heat resistance to the test.
I just bought a set for 100 bucks and I like them a lot. They are carbon foam, and they are fast. But for that price the skinny is that they are not likely doing much extra.
Uhkaa has some limbs now that are carbon through and through. They are pretty pricey, but not relative to normal custom bowyer prices, and if you wanted a real Alaska bow, they might be just the thing. They are souped up, so part of what you are getting is a less forgiving geometry.
Apparently the FITA guys are backing away from carbon foam now that they are shooting a lot at 70M, which implies there is something less than wonderful. I found an old series of Border responses that said they were all in with Maple, and some kind of synthetic. The difference was 1-2 fps at Oly weights. In a lot of ways the maple was a winner in some of the other looked for characteristics. These were hand selected veneers.
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From: Bowlim
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Date: 15-Oct-16 |
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By the way, this summer's experiments that I did out of interest, proved to me that a far better way to go, particularly for a family or a beginner, is to buy all the limbs in 5 pound hops for an ILF, than to spend big bucks for a fancy bow. I'm a big believer in high end fancy bows, but my current philosophy is you need to be able to afford owning the spectrum of weights. With ILF you can get good limbs in the custom range of quality for 60 bucks a set. Ideally 5-6 sets of limbs, but 3-4 would probably do in most cases. It depends where you think your upper end is. The higher your upper end, the more you need to own to fully explore the lower end (and coach friends and kids if you like to).
I also believe in this approach for people like me who have been shooting for 50 years.
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From: M60gunner
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Date: 15-Oct-16 |
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I have a set of TT carbon foam limbs. I have them on a Hoyt Excel riser. I like them and would buy another set. Some guys claim the limbs "ping" when shot but my hearing an'it that good. I do not know about the fps difference between this set and a set of carbon woods I have but I do know I had to go up in spine for the carbon foam. There are just to many archer/equipment variables for the average guy on the range to really see a difference. IMO
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From: The Whittler
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Date: 15-Oct-16 |
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Carbon gives you stability less chance of limbs twisting while shooting, speed was just a benefit from lighter weight in the limbs.
From what I have read the foam was to make the limbs even lighter which gave you more speed and not affected by weather.
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From: George D. Stout
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Date: 15-Oct-16 |
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If you're going into space, light and strong is good. There is a point where limbs can be too light (mass) as well as too heavy. There is a happy medium along the line, and it's still amazing and satisfying to find that maple laminations are still pretty hard to beat in the final analysis. I'm sure there a lots of great limbs out there nowadays, but I fear I'm not good enough to tell the difference when it comes to brick fight.
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From: jk
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Date: 15-Oct-16 |
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Harold Groves told me that foam is just a spassive spacer. He used maple, disliked actionwood because it weighs more. Don't think he tried bamboo ...maybe that wouldn't be wide enough for his recurve limb design...suspect it's better for longbows and narrow hybrids.
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From: aromakr
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Date: 15-Oct-16 |
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Tim Meigs told me 20+ years ago, that some day he would make a bow with balsa wood lams and thought it would out perform any other lamination. I don't think he ever got it done though,. Bob
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From: larryhatfield
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Date: 15-Oct-16 |
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Wonder what the "carbon foam" cores really consist of? The only product i have seen are small in form and certainly not large enough for a bow limb. Is it just Syntactic foam with some added fiber?
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From: Cameron Root
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Date: 15-Oct-16 |
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Morrison foam is good Dryad not so much I think they like bamboo better. Foam should be better
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From: JRW
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Date: 15-Oct-16 |
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When peoplem talk about carbon and foam limbs they're not talking about foam made out of carbon. These are limbs containing foam cores and laminations of carbon.
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From: Silverhawk
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Date: 15-Oct-16 |
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Aeromakr, Your friend was right. In the fifties my Dad made a lot of balsa wood core bows and they shot extremely fast pound for pound. The method was an invention he had. I was hoping a boyer could jump in and give a scientific reason foam core is faster pound for pound, and it is, and it is not because it is light weight but that is close. Harry Drake once said "the best core would be air if you could do it". Not many boyers out there but a lot of bow makers.
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From: Bobby B
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Date: 16-Oct-16 |
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Speed is all about rebound and in a recurve that has more to do with the lamination than the core.
Mr. Groves and Drake realized that in a composite, the core is mostly just the thing holding the laminations apart and the farther apart those are, the stiffer the limb.
Foam gets all the credit when it is really the impressive rebound character of the fancy carbon, kevlar, ceramics or whatever other aerospace stuff that foam is always mated to that is really doing the work in the limbs.
That said, extruded foam can be manipulated for density and is very consistent in flex (much more so than natural wood grain.) Most wood is far denser than an equal volume of foam (cured maple often averages around 40 lbs/cubic foot and a really hard foam like Divinycell is often around 10 lbs/cubic foot or less!)
Wood is more lively for longer though. Foam has a much steeper down curve in breaking down in structure and going noodly on you. Maybe why olympic shooters are going back to maple I read above?
Of course the inconsistent grain structure (and therefore density and flex) of mother nature's wood makes matching limb cores well truly an art. Appreciate your bowyer.
Seen all this with building snowboards and found it fascinating. Would love to use what I know about torsional flex and weave patterns of glass to build a recurve limb I don't think anyone has tried- but I am no bowyer!
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From: Silverhawk
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Date: 16-Oct-16 |
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Bobby,You need to be a bowyer. The limb is made up of three components. Facing,core,and backing. The glass facing and backing are the fastest component for recovery of the limb. The core being slower of the three hinders the recovery of the other two. The compression side, of the core, jambs the wood fibers together thus creating a lot of stacking. The tension side stretches wood fibers but neither one adds to the recovery of the limb in speed because the core is slow compared to the glass recovery. The wood core can add eight to ten pounds to the bows weight but these are slow pounds.A perfect core would be neutral just to hold the glass apart and let the glass be all it can be. The rest is the design of the limb. The foam core can help in this respect being faster and smoother draw.
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From: Longcruise
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Date: 16-Oct-16 |
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"The compression side, of the core, jambs the wood fibers together thus creating a lot of stacking."
"It may give you a few more FPS but I like it because it makes for a smooth drawing bow that takes longer to stack on ya."
I don't think either of those aspects come into play regarding stack.
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From: Bowlim
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Date: 16-Oct-16 |
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"Harold Groves told me that foam is just a spassive spacer."
That is true, and with carbon, it is so stiff if you put it over wood in reasonable quantity, you don't use the active quality of the wood, so using a lighter material that spaces out the carbon lambs is a better model, but not an automatic winner. With glass you may use the active quality of the wood, and that can be a reason for stack. When the gougeons built their wod carbon glass structures, they put the carbon under the wood, because if they put it outside they would have to carry the whole load with it. Glass bent so close to wood they used enough for protection and then the rest was wood which is lighter. The game is different with limbs because they deflect a lot, but the principles are the same.
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From: Bobby B
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Date: 16-Oct-16 |
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Thanks for the encouragement Silverhawk! Maybe someday-
Learning more about bow building has been one of the most fun parts of getting into shooting again. Certainly gets the mind turning. Always thought it was fun to see how blending different materials in different amounts and orientations changes the result.
Amazing how different fiberglass and carbon are even using the same glues. Knowing enough about it all to properly choose where it is layered and in what amount is brilliant.
This website forum is one of the coolest things I've ever stumbled onto on the web. Lots of good people and great characters and minds on here.
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From: Osr144
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Date: 17-Oct-16 |
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I have seen a combination of two different specie of wood used in bow construction.Whilst wood lams are basically a spacer they can contribute to overall performance too.I suppose if you look at yew or a bi lam bow the bowyer is working on two different things happening at once.Tension and compression.Picking a lam of wood good in tension and an other in compression would surely be a benifit.Foam would be almost a neutral spacing medium. Different carbon formats could be helpful too.I know from experience that different weaves of carbon reinforcement can take compression better than others.I would suggest with a bit of research and development better combinations of materials will give us even better limbs.Its great that development is still going on.I thought about having a go at it but need to think it over more.I probably need more data on the finer points of different limbs characteristics.The flight shooting guys are the ones who would know more than what I do.Where's Larry? Is there any flight shooters doing serious work with foam core limbs? OSR
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From: larryhatfield
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Date: 17-Oct-16 |
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We use maple for the most part. Harry Drake had all sorts of carbon and other material available to him years ago, but he stuck with wood.
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From: ProAlpine
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Date: 17-Oct-16 |
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A friend who is a boyer had several limb cores in his shop the other day with numbers written on them. When I asked what the numbers referenced he said they were weights of the different cores of yew, bamboo and foam. Guess which one came in the lightest? Yew. Then bamboo, then foam.
Looking at other industries that use carbon and the developments there... in the ski industry there are lots of manufacturers using carbon these days, but most of them are simply adding carbon stringers and small sheets to a fiberglass lay up. The carbon is lighter and stiffer than fiberglass, but there's not much weight savings because fiberglass resin is still being used and that's quite heavy. There is one company that is employing the military technology (fighter jets) of pre-pregnated carbon nano resins. This design eliminates all fiberglass and glass resin from the ski, saving weight and adding rigidity, especially torsional rigidity where it is needed most (as with recurves).
If there was more money in bow making, materials and design wouldn't be 10-15 years behind other outdoor sports!
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From: Oldbowyer
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Date: 17-Oct-16 |
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My 2 cents. Finally built my dream bow last year carbon/foam limbs. Spent a good chunk of money on it. To be honest did not see enough performance gain out of it to justify the expense.
if your building target bows where you need the stability yeah I can see it. The stability of the limb is there. But for a good hunting bow save your money
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From: jk
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Date: 18-Oct-16 |
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IMO archery is centuries AHEAD of other "outdoor sports." It's personal, disciplined, and non-commercial and it relies more heavily on artists (bowyers) than marketing.
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From: 4nolz@work
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Date: 18-Oct-16 |
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it will be interesting to see if carbon/foam bows survive 50 years+ like the 50 year old bows of glass and wood have (for the most part).
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From: Dry Bones
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Date: 18-Oct-16 |
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Just another 2 cent addition. I had/have a bow with carbon wood core. Never shot through a chrono, but I could shoot that bow and then another wood glass bow and the carbon ALWAYS felt faster. Again it may just be a perspective thing. HOWEVER, the big issue was with an accidental dryfire in which the knock tipped off the string at the anchor and on release let the arrow fall to my feet. The carbon wood bow was done. I have had one other time a similar situation occurred with my other recurve and never so much as a creak. Checked it over and still shoot lots of arrows. My 2 cents is that if you want the most speed ( if 2 fps is enough for you to justify the expense) then carbon or better yet carbon foam may hold some appreciation, but hunting and daily use I will keep my wood glass bows. Like 4nolz said, "it will be interesting to see if carbon/foam bows survive 50 years+ like the 50 year old bows of glass and wood have (for the most part)."
-Bones
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From: dm/wolfskin
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Date: 18-Oct-16 |
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I don't think we will be here to find out Mike.
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From: 4nolz@work
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Date: 18-Oct-16 |
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Not unless 100 is the new 50.But the LW will still be here in the same format!
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From: Osr144
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Date: 18-Oct-16 |
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Matrices of carbon and fibreglass layed up the same resin over time would separate.It is even more so with kevlar glass layup though.Separate strips with glue between them would no OK.As to foam cores they have weaknesses too.Boat builders have made extra ordinary efforts to prevent composite foam carbon or glass sepatating after prolonged use.The stronger carbon puts undue stress on the foam and does eventually separate.Its the same for glass carbon too.I saw a kayak that had carbon rovings in its lay up and it was used to allow a thinner lighter hull for racing.That it did well however less than one year into its use the carbon rovings tore away from the fibreglass.I can't see carbon foam lasting 50 years.A carbon wood laminated bow should as the epoxy glue is a good buffer against the different forces.Glass wood has done it for years and it is the epoxy glue I think allows this to take place.Air was mentioned as the ultimate core but you can figure out to do it cause I can't. OSR
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From: Bobby B
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Date: 19-Oct-16 |
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The problem with foam can be various things but mostly it comes down to the fact that it has a lot of air in it- certainly when compared to wood! Air isn't that strong and resin won't stick to it 8>)
It's true that the resin will soak into the foam pretty well with all those pores on the surface but it will never bleed through the whole block of foam (even as thin as a limb core.) The air layer just under where the resin stops is where the foam will fail.
In the cloth weights that carbon is used it is very brittle without a solid substrate (an uncompromised core) and so any weakness in the foam usually means failure of the laminate. And OSR is right, the differential in flex between foam and carbon is pretty severe. It's complicated stuff!!
I remember a ski company back in maybe it was the '70s who used a honeycomb core in their skis for a while. Lighter than anything anyone had every tried (air would be the best core!) and they were really quick under your feet- but every pair of them delaminated something horrible in short order. Not near enough bonding surface with the edges of a honeycomb.
Strongest composites I ever built were done using vacuum and heat using cloth preimpregnated with resin (and thus dry at room temp.) Those things combined give maximum saturation and optimal bonding if the prepreg cloth was done well.
Building a bow that works great and lasts is an art. The details of using modern materials usage are still being sorted out for sure.
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