Thoughts on sinew

[Kegan]

I haven't seen alot of sinew backed bows lately, so I haven't given them alot of thought. I started wondering, though, if a person could make a bow 66-68" long and still sinew back it- just keep the sinew off the outer limbs? I've become extremely fond of longer bows, and was wondeirng if It'd be possible to have some of the advantages to sinew (namely- boosting weight and reducing string follow) on a longer bow?

[Pat B]

Kegan, On a bow that long you probably won't see much performance difference because you won't be pulling the sinew to its full potential.  It will work fine to protect the back though. Sinew and hide glue are heavier(physically) than wood so it is not always a benefit, especially on longer bows. A longer bow that only has a small working area on each limb might show some performance increase with sinew added to that working area.      Pat

[Kegan]

Would it still bump the draw weight up? Because at 75+#, a little loss of performance won't be too much trouble?

[sumpitan]

Much, much easier, and not as damaging to cast, would be to make the bow just a tad wider for extra poundage. A sinew back on a conventionally-tillered 66" bow of average draw length will make it slower, and not much heavier. A sinew-backing becomes feasible once you're in the 2:1 ratio of bow length / draw length.

Tuukka

[Kegan]

Thanks guys. Good to know before I waste a bunch of sinew.

[adb]

Sinew backing a long bow defeats the whole purpose. Sinew goes with short bows. The limbs just become too heavy. The longest bow I've sinewed was 58" NTN.

[JackCrafty]

Yep, sinew works well for short bows, not only because sinew is heavy but because it takes so long to apply.  Another thing to consider is the climate...sinew + humid weather = poor performance.

[son of massey]

  to be fair, if the inner 50-60" of a 66" or 68" bow compose the working limb, you would have a short bow with long wings on either end.   sinew backing that bow should do the same thing that it would do for a short bow.   the inner limb doesnt move as far, so the extra physical weight would not be such a detriment-the tips would be relatively massless.   string angle would be good and the performance enhancement of the sinew may well offset the performance deficit of having those wings out there not doing any work but adding to leverage.   SOM

[Kegan]

  to be fair, if the inner 50-60" of a 66" or 68" bow compose the working limb, you would have a short bow with long wings on either end.   sinew backing that bow should do the same thing that it would do for a short bow.   the inner limb doesnt move as far, so the extra physical weight would not be such a detriment-the tips would be relatively massless.   string angle would be good and the performance enhancement of the sinew may well offset the performance deficit of having those wings out there not doing any work but adding to leverage.   SOM

Would that really work? Seems everyone says that sinew on longbows is a no-no .

[sailordad]

well what about this then.
you take a holmgard style bow,sinew just the inner working limb area,since thay are all that really bends in this style of bow,
wouldnt this be like sinewing a short bow.just a short bow with levers right?

[Kegan]

well what about this then.
you take a holmgard style bow,sinew just the inner working limb area,since thay are all that really bends in this style of bow,
wouldnt this be like sinewing a short bow.just a short bow with levers right?

That's what I originally asked about, and what son of massey is talking about, but several have said that the sinew wouldn't be stretched enough being jsut on the inner limb.

[adb]

Sinew, like any structural backing, is best when it completely covers the bow's back. An unviolated backing, of any type, is the strongest.

[M-P]

Hi Folks,      I pretty much agree with everything that's been said, but... I like working with sinew and am willing to put a thin layer on just about any bow just as a safety factor.   I work with juniper a lot so I may be predjudiced, since sinew on juniper is such a sweet combo.  One of my current favorites though is an osage flat bow I made when I first started making bows.  I was shooting for a 40 pound @ 28' bow and 68" tip to tip.  Instead I made a dandy 25 pound bow.  I shortened the bow to 66", reflexed the tips and the sinewed the back to bring up the weight.  Recently I retillered the bow and heat treated the belly.  It now shoots a 350 grain arrow at 170 fps.  All of which is a long winded way of saying I think sinew on a long bow is OK if you are using a weak in tension wood, or want to protect a flawed back or need to bring up the draw weight.       Ron

[son of massey]

  i am not saying that sinew backing a long bow is a great idea as what that means to most people is to put a long backing of sinew down.   if it is on the working limbs, which dont happen to be real long, it would be the same as sinew backing a short bow with extra weight on the tips.   an unviolated back is important-but only where there is actual work being done.   i dont see any reason that this shouldnt work.   if the degree to which you pull the bow into reflex is the same as on a shorter bow, the efficiency increase should be the same, the weight of the sinew is near the handle where it hardly moves, and so that may not be a horrible bow to shoot at all.   

adb-if you have thick enough tips that they dont bend at all-or a thick, built up handle, you can cut through the back ring and it wont hurt the integrity of the bow.   that is if that area isnt doing bending work.   an unviolated ring or solid backing material is important when the material is bent so that the backing strips do not peel away from the inner core.   in practice, that is not a great idea either as you may have leverage at the handle area that would still pull if off, maybe.   but if the strong area runs halfway into the handle you should be ok with a violation there.   you could leave an extra few rings on the back in a built up handle to build it up on the back of the bow instead of the belly-in a backwards fashion-and that should be fine if done carefully.   so with the sinew just make sure that at the transition from sinew to outer limb you have secured the backing well to the limb and it should be ok.

sailordad-yeah, that is pretty much what we were saying.   a holmegaard is a good basic design to use when thinking of this, but i didnt want to get locked into that specifically.   the holmegaard has already got safety features in place to keep it together adn to make it efficient, even though it is similar in many ways to just another short bow.   this could be done with a longbow tillered to look like a holmegaard, for instance.   

M-P-a good point.   wood/situation depending, sinew may help more than it hurts too.  SOM

[AKAPK]

My 52" Sinew Back D bow  is pushing the limit for using sinew but , I used longer elk backstrap for that Its kinda shocky to but Hits a good group at 10 using 35-40 spined primitives.I noticed it takes the bow longwer to return to unbraced set with Sinew backing on a longer bow. :)Phillip