Primitive Archer
Main Discussion Area => Bows => Topic started by: BrokenArrow on October 14, 2015, 11:53:39 am
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I have sinew backed a osage orange bow and I am close to getting a string on it.
Question: When should I apply the rawhide over the sinew? Now or when it has been tillered?
Thanks
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Why a rawhide backing over sinew?
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What Pearlie said, only adds mass !
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I suppose I should answer your question. If your intent was to add rawhide from the start then it should have been added before you started tillering. When the sinew is dry and ready to go, add the rawhide, wait 5-6 days and tiller the bow. I say wait at least 5-6 days because adding wet rawhide to a self bow isn't quite the same as adding it to a sinew backed bow. The sinew will suck up that water like a sponge and will require more time to dry than a self bow does.
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What Pearlie said. This would also be for snake or fish skins, etc.
I wait at least a few days before stressing a bow after adding skins to a selfbow, even oily wood like osage. I did this once and the weight dropped from 60# to 45#. After 4 to 5 days the weight was back up to 60#. It added just enough moisture to the wood(osage in this case) to drop the weight. Once dry again the weight went back up.
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I thought the rawhide would cover up the sinew as it is not smooth. Am I missing something here?
I'm not a fan of snake skins but do not like the rough look of sinew either.
I like painted rawhide but what is the alternative?
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Rawhide won't smooth out rough sinew unless you intend to add tons of glue to fill in all the low spots.
The solution is smooth sinew first and then any thin covering material can be used as a waterproofing layer.
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One of the hot shot bowyers mixes up sawdust and TB3 as a bondo and fills in all the gaps and crevices prior to adding rawhide. I wouldn't advocate that.
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a very thin rawhide,, deer,, wont add enough mass to hurt the performance,, or goat,,,, if you like the look of it... or want to paint it ,( pen and ink looks very nice on rawhide), it will help protect the sinew in harsh conditions just like a snake skin,, I have a bow I am planning putting rawhide on,, yes it will add mass but very little,,,, if you shoot a bow through a chrono, before and after,, you will see it is a very small difference if any,,, I made a bow for a friend last year, shot it through a chrono,, then put rawhide on the belly to cover some rasp marks,, I didnt want to loose weight by taking them off,,the bow shot the same fps after putting on the rawhide,, I had read about putting rawhide on the belly in a book AMERICAN INDIAN ARCHERY by Reginald Laubin,, he talks about putting rawhide on the belly of sinew bows to reduce checking on the belly of heavily sinewed bows,,anyway I guess my point is,,, rawhide does make a beautiful backing and with a good finish would protect your sinew back,, :) if you are worried about the performance, then narrow your tips,, reduce the string count in your string,, or shoot a fast flight,,instead of b 50,,,or draw the bow 1/2 inch more ,, work on your release and it will shoot harder than before you applied the rawhide ,, :) :)
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You can paint over the sinew with acrylic craft paint to disguise the sinew but it won't smooth out the surface.
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One of the hot shot bowyers mixes up sawdust and TB3 as a bondo and fills in all the gaps and crevices prior to adding rawhide. I wouldn't advocate that.
What's your reasoning behind that opinion? Aesthetic reasons or performance degradation?
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One of the hot shot bowyers mixes up sawdust and TB3 as a bondo and fills in all the gaps and crevices prior to adding rawhide. I wouldn't advocate that.
What's your reasoning behind that opinion? Aesthetic reasons or performance degradation?
Adding a 1/4 cup of glue and sawdust to each limb seems counter productive to me.
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Bradsmith, that's a lot of excellent advice! I recently made a mulberry paddlebow and did a light rawhide backing over the sinew so it would be easier to paint and the colors would be more apparent. Shoots great and looks great. I've heard you don't want to destroy the outer layer of sinew by sanding it as this is the layer doing the most work. I tend to agree with the concept especially for shorter bows where the sinew is really a contributing factor to its performance. So, in this regard, best to leave it be and just paint it perhaps.
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well you could paint it and lightly sand it,before adding art work,,,, and it would smooth it out somewhat ,, I have put a pretty thick coat of paint on sinew back hunting bows that were expected to hold up in the rain,, as far as putting sawdust and glue on the sinew I cant really see any reason to do that,, you are trying to use the minimum amount of hide glue in the first place to reduce mass,,
I guess if your main concern was appearance you could do it ,, but I would think it would slow the bow down or reduce performance,, I have never tried that so I am just guessing :)
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I'm working on a couple of sinew bows right now and used the method that Ed Scott used. The amount of glue/sawdust it actually takes is nowhere near the 1/4 cup I mixed up, especially after it is sanded down. I couldn't tell you the weight of the filler, but I doubt it'd be more than an ounce. If you don't use a filler of some sort and plan on using a backing (rawhide or skins), it would be very difficult, if not impossible, to not have any voids underneath the backing, at least the way I've been doing it.
If you want to leave the sinew exposed, you have to be really careful with applying the finish, making sure to completely fill all of the cracks and crevasses. You still have a pretty high probability of not getting it all of the sinew coated, and that is a recipe for failure, especially if you use hide glue.
As far as degraded performance, I doubt it'd be noticeable. My sinewed and backed bows are really good shooters, and although they have a little more mass weight than my self bows, they shoot harder, draw weights being the same.
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If you don't use use a filler of some sort and plan on using a backing (rawhide or skins), it would be very difficult, if not impossible, to not have any voids underneath the backing.
Wanna bet? It's not difficult and far from "impossible"
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If you use hide glue and thin rawhide or skins it will "suck" the backing to the sinew(if hide glue was used with the sinew) so it eliminates the voids. I've done it with both skins and rawhide.
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Hey there guys I'm new here so my opinion may not carry a bunch of weight. I'm usually over on PP and I make most of my bows with sinew backings I love the stuff. There's 2 things I would say about a smooth back 1. Your sinew shouldn't have a terribly rough texture if it's applied with skill. What I mean by that is I believe sinew should always be soaked in warm water till highly pliable and then combed out with a old school pocket comb. To make this easier I almost always use leg sinew (although back straps can do this as well) and as I split the legs I leave about 1/2 of the tendon intact which keeps the fibers all together and easily combed out so they end up nice and strait like fiber glass then that 1/2" is cut off before I apply the glue.
And number 2. If you'll use a fine grit like 150+ sand paper and sand down the back after the sinew is good and dry till the sinew is perfectly smooth (you can keep going up the grits and get it super duper smooth if you want) then dust off the back of the bow and take a damp rag and run it
Gently over the back a little bit of glue will reconstitute and coat the back in a beautiful shine. And iv never had one sanded like that break (at least not yet)
I can't see that sanding off the very microscopic top layer of sinew would hurt anything because the sinew is working as a matrix the very outer most fibers aren't working that much more than the rest
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Okay, I was wrong. I've only done a handful of sinew backed bows and only used titebond 3, not hide glue. I basically have built them like Ed taught me. His method does leave it a little rougher than what you described, Ryan, and I think makes that filler necessary. On the ones I've built, once the sinew dries, it does leave the surface with some high points and little cavities. I wouldn't call it rough, necessarily, but it's definitely not smooth, and would definitely take more than 150 grit to get the back smooth.
I think on the next one I build, I'll try to comb it out and see if I can go without the filler. I've just been laying it on and patting it flat, or I should say patting it so that the sinew is more domed, with the center being thicker than the edges. Ryan, I do like the way you are prepping your sinew. I've just been pulling it apart into separate strands. Your idea seems a lot easier.
One question, do you think using hide glue with sinew would create a more homogenous backing than using TB3, and less likely to have voids, or are the voids more of an application issue?
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I think the voids are a bit more of an application issue but at times you'll get a bit of roughness just depends on how well you comb it out and how much you soak it. With tb3 I will admit iv never used ot with sinew applications so I don't know for sure but here's my thinking on it. If you look at all the horn bow guys they always soak their sinew throughly for several reasons like the ones we have been talking about but also because sinew when it dries it should shrink draumatically which helps pull the bow into tighter recurves. The same effect should be seen on every sinew backed bow the sinew should pull that bow into atleast some back set (even if it's ever so slightly). We all know what that does to the performance of the bow but also to the performance of the sinew as sinew works best under higher stress that's why we like to hump it up in the center. Anyways....... The cool thing about hide glue is that as it dries it helps the shrinking effect of the sinew because both are water based. So water and water will dry at the same speed causing a more curing or homonigization of the "matrix" (you could call it) of the sinew. Whereas it seems to me that tb3 dries much quicker than the natural watery hide glue and watery soaked sinew which I would think would cancel the brilliant effects of natural sure backing.
Does that make any sense? I may have been too wordy.
Maybe I can show a pic of some of my
Sinew work to help
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The way I've been building them is to add reflex into the overbuilt blank with heat and a caul. After applying the sinew, which I let soak in hot water for about 30 minutes, I let it set up for a few months, then proceed to tiller it out. With the TB3, the sinew dries, but it doesn't pull the stave into any more reflex than I previously put in it. I guess I could lay the sinew on a little neater, combing it out, and probably will try that on the next one, but honestly, the way I've been doing it, with the "bondo", it scrapes down to a nice smooth limb. Since I usually cover them with skins or rawhide, I guess it really doesn't matter. I'm ending up with some really good shooting bows.
I was just reading a thread that PatM did about making a really smooth sinew back and think I'm going to try his method. My only concern is that it's so humid here in SC, that it's going to take forever for the hide glue to stabilize and set up. I haven't had any problems with my sinew/TB3 bows loosing much cast with the humidity (the heat is another story), but I'm concerned with what sinew/hide glue will do in similar conditions.
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Hide glue will set up in humid areas. It still has to meet equilibrium with the local R/H. If you have it in your house with a/c it will dry more. I still give sinew/hide glue backing at least a month between layers and final curing.
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looper if you like your bows now? Try using PatMs method with hide glue or Knox. Then add your rawhide, if you still choose to. I think you will feel and see a distinct difference in the two "models".
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I have heard of using the tite bond,, but I dont recall anyone posting actual performance of the bow,, I am sure it will hold the sinew on and is waterproof,, and that the bow will shoot well,, but without pulling the bow into more reflex I am wondering if the bows with tite bond have the performance of the hide glue bows,,, I am skeptical that the tite bond bow will out perform a tradition hide glue bow,, It would be great to have some test results of a titebond bow shooting through a chrono,, :)
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I agree with you, Brad. TB and sinew probably makes a good backing but I doubt it adds performance, even if you draw your bow into reflex before adding the TB/sinew. You will get the benefit of the reflex but not the TB/sinew.
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I'll be finishing up a couple of them over the next few weeks. If I can find a chrono, I'd be more than happy to post up the results. I need to use 10 gpp arrows and 28", right?
One of them is a snakey osage, with sinew/tb3 and a snakeskin. It's 66" overall and is 60@30". It has a very slight reflex to it. I've actually reworked that bow. I built it from a blank that Mike Yancey had glued up, using his methods. Initially it was 72"overall, and, although I had a good tiller on it, it had some hand shock, simply because those long limbs, along with the sinew and snakeskins were so danged heavy. I ended up shortening it and still need to put on a finish, but it shoots night and day different than it did.
The second one was built using Ed Scott's method, which is essentially the way Mike does it, at least in regards to the sinew and titebond. I need to tiller it, but it should come out at 55-60@30". That bow has a deflex/reflex shape with Ed's modified molle tips. I'll post some pictures of it as I work on it.
I do have another one I need to finish. It's a 67" rocky mountain juniper, sinew/tbb, with horse rawhide. Ed Scott built that blank and helped me work on it. It has a straight profile and the working sections of the limbs are D shaped in cross section. It also has those long stiff limb ends that Ed preferred.
I was concerned that the horse rawhide was going to be way too heavy, but the bow actually shoots surprisingly fast. I think the light weight of the juniper offset the added weight of the rawhide. As it is, it's a really light in the hand. I just need to figure out how I want to decorate it. Being that Ed helped me with it, I want it to be a tribute to him and do him justice with the final product. It'll be unique to say the least. That horse rawhide is really dark.
I've got a couple of other blanks glued up waiting to cure, but I also have some osage blanks I got from Mr. Maguire at the Tennessee Classic. A couple of those will end up being self bows, but I think I might try the sinew/hide glue on a couple. I need to find a good Juniper stave to try that on, too. I bet that with PatM's method and Juniper low mass weight, you'd really have something.
Seems like I've got a lot to do.
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yes Looper,, if you shoot any arrow you know the weight of,, it will give a general idea of the bows performance, but 10 gpp is good, the arrow can be any length,, its the weight that helps compare performance,,, 500 grain arrows are good for testing too,, cause alot of people have shot their bow with an arrow about that weight and can tell how the bow is performing,,it will help you immensely in fine tuning your bow designs,, and help you know if what your are making,,,is really working,, or getting the most from the design you are using,,
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I think the answer to my question was right under my nose, goat rawhide not cow rawhide