Fabric Backing - just durability, or power too?

[Mububban]

Howdy

On the latest boo board bow I made with help, as an experiment and to hopefully aid the bow in holding together, I glued linen fabric on as a backing using Titebond II. The linen had a stretchy and non-stretchy dimension (weft?). I deflexed the bow about 2 inches then glued the linen on so the non-stretchy dimension ran the length of the bow.

It turned out about 43lb @ 27 inches. I think it only pulled 40lb before the linen, but silly me didn't take a really accurate poundage reading before backing it, so maybe it started at 43lb, I don't know

I've heard that natural bamboo backing adds enormous power to bows. My question is - can linen backing on a bow increase its poundage slightly, or is it mostly for protection?

Thanks!

[Stickbow Hunter]

I deflexed the bow about 2 inches then glued the linen on so the non-stretchy dimension ran the length of the bow.

I imagine you mean you reflexed the bow. I think the reflexing would have increased the weight not the linen. I think the linen would be more protection from any splinters lifting.

Jeff

[Mububban]

Yep wrong term used, I meant reflex

At what stage of shaping and tillering should the protective backing be applied? My fiend and I are going to have a go at making a crossbow prod.

I'd like to glue up the 40 inch prod from 2 bamboo strips (mildly reflexed if it'll co-operate), with hardwood nock overlays and linen backing. I'm just unsure when exactly I should back it. Should I do the initial rough shaping and apply the backing before tillering, or as it's just for protection not power, should I pretty much finish the prod off, and then just glue the linen on as a final step?

[Stickbow Hunter]

I would do it after/during the glue up as that way it will be there as protection as you work and tiller the limbs.

Jeff

[perry]

Years ago 'pre-tensioned silk' ? was used as a backing on mass produced wood bows and I've read it did pull bows into reflex and boost performance in a similar manner to sinew backing. I have never found any reference to how pre-tensioned silk was woven only read it was stretched taunt in a frame before being glued down. It is not the same as silk cloth.

I am not aware of any fabric that has this property. Rawhide will help a bow return from just unbraced set a little quicker but adds no performance other than protecting the back. Have you considered Rawhide as a backing for your crossbow prod. This mob sell Kangaroo Rawhide which is a wonderful bow backing http://www.packerleather.com/ . The large rawhide dog chew bones you can buy in a el cheapo store or supermarket are another easy source of Rawhide but the rawhide is much thicker beef hide and needs clamping between 2 boards to flatten it out before sanding it thinner, a real pain.

regards Jacko

[Mububban]

I think I'll try the free linen on this first attempt, and if it proves successful I'll be willing to pay for some rawhide as my L-plate skills slowly increase. Eventually I want to try all sorts of things - fabrics, rawhides, natural bamboo, other timber laminations etc etc.

Thanks for the advice guys, much appreciated.

[perry]

Don't be concerned about applying Rawhide as you use the same process as with material. I do recommend you use crepe bandages to clamp the backing down instead of binding if you want a smooth finish. Linen is cheaper for practice runs . I have used Hessian upholsterers webbing also . It's very thick but once saturated with glue and dry it can be scraped or sanded to the desired thickness and the crosshatch weave can be coloured to resemble snake skin by applying a stain, scrap it, to a patch work, then repeat until your happy,. Just be mindful you are applying moisture to your bow as waterproof Pva's or hide glue are the best to use and it will need to be given several weeks to dry out properly before bracing.

It does not really matter when you glue the backing on, I prefer to glue it after I have tillered the bow to brace height as the bows back should be finished being sanded with nicely rounded edges etc at that stage.

regards Jacko