Too long for sinew?

[northvtarcher]

If you are making flatbows 66-68" long can you still use sinew as a backing? I was reading a post that thought over 60" was long for a sinew backed bow. If so why?

[HoBow]

On long bows, the weight of sinew takes away the benefits it adds.

[JW_Halverson]

The Traditional Bowyers Bible no. 1 has a nice line drawing of a long bow being pulled to a certain distance and a shorter bow drawn the same distance, the two bows are laid one over the top so that you see that the shorter bow tips travel farther back, the back of the two bows show the shorter one is stretched much more than the longer one. 

The longer bow just doesn't get the backing (sinew) stretched enough that it is actually doing work.  Since it isn't doing any work, it's just sitting there taking up space and adding weight.  It's a lot of work to go thru for no benefit.  If you are concerned about the back of the bow failing, back it with thin rawhide, silk, or light cotton. 

[shamus]

eh, too long.

[Kegan]

I'll admit it, I like short bows but I hate shooting them... but I like sinew backings ! On longer bows the thing is to design the bow to be overstressed, mostly by making all the bend towards the inner third, leaving the rest of the limbs as stiff levers. After reflexing and sinewing only the inner third of the limb, the sinew has to take the burden of bend from the almost-hinged inner working limbs. I did "Talea" towards this idea, not taking it to the extreme I could have (longer with a shorter sinewed section). The result is a fast bow that's relatively stable that won't want to break on you anytime soon