what is it about carbon foam?

Hello everyone!!
I will be shopping soon, and new limbs are on the list. I keep getting told "make sure you get carbon foam". Why? On the money side there are many non-carbon foam limbs selling for higher prices than some of the carbons. If carbon was "better" than they'd never sell. What is it about carbon foam that has so many people impressed? I have probably £280 to £330 set aside for limbs and I'm looking to make a 68" box on a 25" riser, looking for 42lbs on the fingers. May "cheap" carbons stop at 38lbs so I'm wondering how they're engineered compared to the expensive carbons that go well beyond 42.
 


Timid Toad

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The "foam" is a bit of nonsense. What most people mean is synthetic, as opposed to wood cores, with carbon (and sometimes glass laminates) on top. Synthetic cores tend to be lighter and uniform and a little faster (maybe 2-3fps). There's no evidence to say they last longer, feel different (that's down to the profile) or are better in any other way.
 


LionOfNarnia

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Do you really need to spend that much on limbs at this stage of your career?

A pair of Samick Ideal carbon foam limbs are an absolute BARGAIN at £77 imo. I used 36# until a fortnite ago, upgraded to 44# and am completely satisfied with them. Merlin have 68/40 & 68/42 in stock, why not give them a whirl & save y'sel £200+ for something else?

Maybe I'd have a different mind-set if I wasn't on such a tight budget, but I think people are too quick to hand over serious moolah for something which a) doesn't solve an 'issue' that they've identified (preferably with the aid of a good coach) & b) will make as-near-as-dammit ZERO difference to their ability to put an arrow in the gold.

The shops & manufacturers LOVE free-spenders but 'the trick' is too walk the path of balance ;)
 


jonUK76

Member
I have probably £280 to £330 set aside for limbs and I'm looking to make a 68" box on a 25" riser, looking for 42lbs on the fingers. May "cheap" carbons stop at 38lbs so I'm wondering how they're engineered compared to the expensive carbons that go well beyond 42.
If a limb manufacturer only offers a particular model of limb up to 38 lbs it's likely more a marketing decision than an engineering one. You can buy limbs which are cheap, very mass produced in weights to 60 lb or sometimes more for bows aimed at the hunting market (e.g. Samick Sage and clones).

On the "only get carbon foam" thing, carbon and foam is really referring to two different things. The core of the limbs, is either a synthetic material like syntactic foam or wood, which has laminates of glass fibre and/or carbon fibre bonded to it. More money should get you more carbon fibre and less fibreglass in these laminates. Incidentally many top recurve shooters seem to choose the wood core version of a limb rather than a foam core version (e.g. the MK Korea Veracity which have a wood core, seems more popular with elite archers than the otherwise similar Mach X foam core) so I would say the advice to "only" get a foam core limb is dubious.
 


Rik

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As a data point... I'm happy enough using some cheap Kap carbon limbs or Soul Black Flash, as light training limbs. They work well enough out to 70m and I don't get the impression that they are limiting me. But I will work back to my Border Hex limbs, they just feel better.
 


jonUK76

Member
My main limbs both came from eBay - 36 lb Winex's which were very lightly used but in great condition and won for a bit less than half the price of a new pair, and some 42 lb Uukha's EX1's which according to the seller were bought and then only shot a few times before he realised they were too heavy. Buying used can be a good way to get more for your money - if you're choosy anyway. No doubt some well beaten up stuff gets sold too, so beware of that.

I also have a set of the cheapest limbs I could find (£50 Samick Privileges) in 30 lb for when I was recovering from an injury and they shoot pretty well at the shorter ranges I've used them at. They physically weigh quite a bit more than the other two (the Winex's are the lightest) which is because fibreglass is heavier than carbon - less weight in the limbs should translate to more energy into the arrow.
 


mbaker74

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If you want to spend that kind of money, do yourself a favour and just buy these...

Uukhas EX1 limbs

In my opinion, the more you spend, the better the "engineering" and build of the limb is, plus they tend to be faster and much nicer feeling than the cheaper end of the market.
historically, cheaper carbon / wood limbs have been a bit hit and miss, as its hard to get the performance of the wood in both limbs to match on a budget. Expensive wood core limbs tend to be good as more care is taken to match them.
 


KidCurry

Active member
The £280-330 price band is a grey area. I've never really decided what you get for the money. The really cheap limbs lack matching, finish and any real quality feel. The top end limbs have it all, but that area in between? I have 4 month old £550+ Hoyt X tour and £160 SF Carbon Elites and there is definitely not £390 difference in performance, build and feel. In a blind test I probably could not tell you which I was shooting, perhaps the Hoyt's have slightly more snap to them. If someone offered me £400 for the hoyts I would sell them.
If you are shooting at the top of your game you would not be asking this question. If you have a year or two under your belt you will not get any benefit top end limbs will bring. My choice would be WNS Elite Carbons and look to some good arrows.
 


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steve

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I can't see how "foam" of any sort has a place in limbs. Foam's function is to take up space. Good for insulation, but not for strength/elasticity.
 


Timid Toad

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That's exactly what it's for - to take up space. The working layers need to push/pull and need separation to do that. You need something light, flexible and hardwearing for the job.
 


Rik

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I can recall having a conversation about how the best filling for a limb would be... Vacuum. No weight, no mechanical properties to interfere with the operation of the limb... Only, how do you keep the working surfaces of the limb from collapsing together? So "foam". Note the scare quotes. Some are just a low density plastic. Some are a plastic matrix filled with plastic or ceramic beads to make a "foam" (consistent hole sizes instead of varying sized bubbles).
 


KidCurry

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You don't 'need' separation but it helps get the best properties with limited material, ie stiffness without the weight. Uukha limbs are just compressed carbon layers and have made these foam/wood cores redundant. They are effectively a carbon spring.
 


Timid Toad

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Yes, there's different ways of achieving the same thing, but it still stands: the bit in the middle does nothing but separates the working layers. So make them light, hard wearing, good in a huge temperature range and preferably easier to handle than very expensive tricky impregnated carbon weaves.
 


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I'd love to try Uukhas one day but there's so few stockists. I watched some competition footage I found on youtube that was 2019 so very recent but didn't see any being used. Yet everyone raves about them. Maybe I watched the wrong part of the competition or maybe they're not aimed at target (no pun intended). Either way, given they're price they aren't something I'd ever buy without trying them out and they don't seem to have much distribution in the UK at the moment.
 


mbaker74

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Dave, you wont see them on the main stage target archery stuff on YouTube, as Uukha don't pay the big boys to use their kit.

Do yourself a favour and get down to Perris archery in Essex, even if you make a weekend of it. I shot the Uukha set up against hoyts top of the range, which is initially what I had set my heart on, and walked away with uukha.
 


geoffretired

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Just thinking aloud; when we bend anything, the outside of the curve is being stretched and the inside is being compressed. The extreme outside surface is being stretched the most; while the extreme inside is being compressed the most. As we move in to the middle of the material, the stretching and compressing are both reduced compared to the outside. In a single layer of material the extremes in both stretching and compressing have to be tolerated by that one material. Somewhere inside the material is a layer that is not stretched or compressed. IF we could slice down the middle of that single layer and bend them as two layers( not glued together) we would find each layer would be subjected to both forces. Where the two layers lie against each other, they would rub on each other, as one surfaces is compressing and the other is stretching. It seems to me that the glue line is there to prevent movement between the two laminates and to ensure they act as one thick item, not two thin ones.
If we use two laminations, we can choose the outer for its ability to withstand stretching and the inner for its ability to withstand compression.
If the right materials are chosen along with the right thickness of each material, then the glue line can be subjected to being bent but not stretched or compressed. I think that is like the self bow of yew having the right thickness of heartwood and sapwood so the two layers both get subjected to just one of the forces. I would guess that a middle lamination could be used to good effect
 


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