Bow Backing
Next time you snatch a moose, scrape the hide (hair and flesh side), cut it lengthwise, and hang it to dry. You won't build enough bows to go through the whole hide as bow backing. If you don't hunt moose yet, talk to a person that can get you a hide.
I prefer a backed bow with a toasted stave. The backing will hold splintering and back fracturing, giving the bow far more integrity to take a lot less careful overdraws (this will compress the wood, however). Backed bows are just hard to break.
Contrary to what I have heard from a far more experienced bowyer, I don't find a very thick hide nearing the tips detrimental to bow performance. Hide has far more strength per ounce than wood, so a hide-backed bow can be thinner and lighter than a self-full wood bow of equal draw strength and speed. Again, however, this is just my very limited experience from building my own bows.
Rough up the back surface before applying glue to increase the surface area.
Regardless, the back (sinew, cotton, hide, &c.) is always a triple or quadruple hide glue layer, which is allowed to dry, before applying the backing; this will inundate the surface with a dry wood glue layer, seeping and filling every pore, readying the surface for the glue-soaked backing to ultimately make the backing material and the wood really become one; these layers should be thin to ultimately make a thick layer.
When using hide for back bows, the flesh side of the hide is usually glued to the wood back; this hide surface MUST be well scraped. If it is not, the glue will adhere only to the sinewy stuff on the surface of the hide and not the skin fibers, and the back in that area will peel away as the bow is used.
Wrap well with a cotton wrap while drying. The same bowyer mentioned earlier (Clay Haines) suggested using a weighted sleeve slid on the limb to keep the backing down while drying.
When backing sinew, don't be afraid to use glue generously to coat the wood well before the first layer of sinew and after subsequent layers to fill gaps and coat. My first sinew-backed bow was perfectly backed and featured ZERO cracking or sinew snapping sounds when drawn. The sinews were individually, randomly placed in three layers, and the sinews reaching beyond the tips curled over the tip and back on the belly; a final, light strap of sinews was formed around the bow, just under the nocks for security. This demonstrates to me that sinew snapping may be the result of using leg sinews, which aren't really long individual strands, like the back sinew and a few others, but more of the woven sinew type. I found that a tamped sinew leg bundle—the "standard" procedure for dividing and loosening sinews—was easy to break in my hands. Tamping seems to damage the sinews.
The best material to use for sinew backing is the long back strap. Curl the sinew over a thin round tool, and they will separate. When loose, pull apart dry.
Many long back sinews were used in the backing, and in my dry climate of Alberta, only nine or so days were waited from the final wet sinew when I began the final tiller; you (probably) don't need to wait six months. Then again, I'm not a 13th-century Mongol bow builder.
When I sit back, I grab a few strands and straighten them out from a mixed jar of wet strands. It's slow, but I think you get a more staggered strength than from taking larger bundles and laying them down in a brick pattern.
A sinew-backed bow is a new experience in self-made bows. The bows seem to lose little power over heavy use, making them apparently indestructible. Is sinew necessary? Sometimes, but a serviceable bow does not need sinew. Though hard to make, sinew seems to hold the investment, a statement I was strongly skeptical about before. A sinew bow will go to hell with you and not whine about it, unless it's damp or wet. Compared to self bows, cable-backed bows, or hide-backed bows, the sinew bow needs almost no maintenance over long and heavy use; eventually, the sinews on the surface seem to lose their glue coating—a recoat of hot hide glue on the surface now and then solves this. Maybe a hide backing on top of the sinew will eliminate the need for this resurfacing?
Additionally, a sinew back will make a piece of wood take an unimaginable amount of stress on a bend; don't test this too much, however, but prepare to be shocked when the sinew is well applied.
Always use hide glue hot or warm, and never at room temperature. The glue will flake off and not adhere properly if it's applied at room temperature or cold but still liquid. When refinishing the back periodically, remember what has been said.
For a quick and dirty fix, when the bow needs a bit more punch or has lost its punch, even with a hide or sinew back already there, throw a cable on—any will do. I have used sinew and hide from the borders of my smoked skins. Twist, secure, wrap, and shoot. It's prudent to let off the cable at the end of the shoot session; this can be a pain in the butt, but the cable back is usually a temporary fix.
Sinew has thus far been the best-performing back of the three mentioned, by far, and not much harder to apply than any other.
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