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To back or not to back…or where to back?

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Capt.Moses:
I’ve recently taken it upon myself to make a recurve/Holmegaard style bow. The Holmegaard bow has very wide lower limbs that taper off quickly into thinner upper limbs, which act as levers to put more power into the lower limbs. I thought that by making them recurved, it would only enhance their levering abilities, making for a faster bow. I linked an image of the design below(without the recurve modifications). If I decide to put a linen backing on the bow, do I put it on the recurved section as well as the normal part of the bow, or only the normal flat part? Also, I haven’t yet found a definitive answer as to why fiberglass/drywall tape is a bad backing other than “it’s not natural” and “it’s ugly”. I’m sticking to linen for this build, but might try out some other types later down the road, and want to know which ones I can skip. Thanks!

sleek:
Recurves don't exactly increase leverage, they more keep the string angle constant through the draw. Which is why longer bows don't benefit from recurves.

It's one way to look at it that they increase leverage on short bows, but thats not universal to all bows. What is universal is them keeping the string angle down. So that's the way I prefer to have it explained.

Now I know that's not the question you asked, but I hope you see that with that information, recurring won't help you unless your draw exceeds what the bows length allows.

willie:
welcome capt

a backing would be for the working inner limbs, as the lever would not be bending much and be stressed less

just curious of the purpose for linen backing, and how thick are you thinking the linen will be?

this is a curious design and hope you can link to a pic showing the proposed reflexed tips
significant reflex in the outers will most likely call for thinner and wider inners than a straight bow of same poundage

sleek:
Fiberglass tape, as typically applied, adds no strength to the back. The adhesive doesn't bond to the wood well enough to reduce the strain on the back. So it's only purpose would be a shrapnel net should the bow self identify as a grenade.

If you were to apply the glass in an effective manner by removing the adhesive and laying it with epoxy, the glass would make a fantastic backing. One so good infact, that the wood would make a terrible belly. The glass will likely overpower the wood and cause belly failure, aka, set.

That being said, your planed route is acceptable. Where to put it? On the working limb of the bow is the most effective area, passing by it an inch or so to give good attachment points for the backing to non bending wood. But, backings are not a magical solution to problems, sometimes not even needed. So I guess my next question is, why do you want to back it? Backing is kind of a pain.

Capt.Moses:
Sleek,

Thank you for the advice about the fiberglass backing. I put one on my first bow I made with wood glue, and it seems to be the only thing holding it together, so I will take that into account for future builds. As for the current build, I’m making it with a hardware store plank. I don’t feel entirely confident that it’ll be able to withstand significant pressure, so I figured I’d use it to try out a new backing method(new to me at least).

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