Author Topic: Self Bow Help - Sinew/rawhide backing questions (Read 2117 times)

rcoen2 · « **on:** September 13, 2020, 12:14:09 pm »

Hi all,

I'm new here. I recently bought my first bow. It's a Black locust recurve self bow, with a draw weight of 37 pounds at 27 inches. I do not know the length of the bow at this time.

The bow had a paint job on it, and I was wanting to return it to a more natural look. The bow maker cautioned me that sanding off the paint could disturb the growth ring. I sanded off the paint and haven't yet shot it. I don't think I disturbed a growth ring because I used super fine sand paper and was careful. Ive been researching sinew and rawhide backing to create extra insurance and security for the bow, and because I want to bring the bow over 40 pounds (for white tail deer hunting).

The bow maker also cautioned me against doing sinew backing without guidance from someone who has done it before, and said that I could accidentally ruin the bow.

At this point I've read just about every website and forum that I've been able to find on sinew and rawhide backing. I guess I have some unanswered questions and wanted to open up my process with this bow for community support.

thoughts/questions/considerations:

-It seems like if I didn't feel comfortable doing a sinew backing I could at least do a rawhide backing with hide glue. This wouldn't increase poundage as I'm wanting but it would create better protection for the bow from any weakness in the growth rings. But would this slow the bows fps down with the extra mass/weight?

-When this bow maker said I could ruin/break the bow. What are the main problems he was thinking of and cautioning me towards?

-This bow was designed to be a self bow. So adding sinew to a bow that was designed to be a self bow is different from sinew backing a bow that was designed to have sinew. So in this way what considerations might I be missing in how sinew backing could affect this bow?

-It seems that traditionally doing a sinew backing is often done by back bending the bow to increase the reflex. But it seems that a lot of people add sinew with the bow in an unflexed position. Can it be done either way in my circumstance. Is there anything to consider because the bow has already been put into a recurve.

-Being that because I haven't made a bow myself yet I don't have experience tillering. And it seems like sinew backed bows require skilled tillering... Is this a reason for me not to attempt the sinew backing process?

There are more questions and thoughts floating around my head, but I'm thinking Ill leave just these ones here for now as a starting point.

I so appreciate any help or support!

Pat B · « **Reply #1 on:** September 13, 2020, 02:36:24 pm »

Welcome to PA, recoen2.
Adding a sinew backing to an already tillered selfbow, recurved or not shouldn't harm the bow as long as you were careful sinew backing it. You will probably have to retiller the bow but not too much I wouldn't imagine. You will have to allow the sinew to cure out well before using the bow. I like to give a sinew backing a month. Even though the sinew might be dry there could still be moisture in the wood from the sinew/hide glue application. Black locust can be susceptible fretting(compression fractures) if your tillering is off so you'll have to be careful with that
Unless you sanded through the back ring while removing the paint it shouldn't harm the bow. You could tie the tips together with a little reflex so as the sinew dries it doesn't have to work so hard reflexing the bow as it dries. You will probably have to shorten the string a little as the sinew cures and draws the bow back into reflex.
Tillering isn't difficult but it should be thoughtful. Post a pic of the bow now so we can see the side and back profile. And post pics as you proceed so we can help you through the process.

bradsmith2010 · « **Reply #2 on:** September 13, 2020, 02:52:57 pm »

one even layer as Pat suggested wont effect the tiller much,, or at all,,
if you put the sinew on,, it will probaly be safe to pull the bow further and get you 40#,, but the sinew may add enough draw you wont have to do that,, just depending on how thick your layer is,,
at this point,, bending the bow backwards to apply is a good technique to know, but not absolutely necessary either,,,
if you wanted to just go with the rawhide, then you could probably pull the bow further to get your 40#,, I am just guessing,, really need more details and pics to give better advice,,all that being said, if the bow is long enough,,,you might be able to pull it to 28 and get your 40# and do nothing,, I like the idea of at least a rawhide back though,,

rcoen2 · « **Reply #3 on:** September 13, 2020, 03:12:49 pm »

Thank you both for your support! So exciting to be entering the world of bow making..

Quote from: Pat B on September 13, 2020, 02:36:24 pm

You could tie the tips together with a little reflex so as the sinew dries it doesn't have to work so hard reflexing the bow as it dries. You will probably have to shorten the string a little as the sinew cures and draws the bow back into reflex.

Is there any way that pulling the bow back like this could damage or break the bow? Or is it pretty safe to pull bows back into a minor reflex like that?

Quote from: bradsmith2010 on September 13, 2020, 02:52:57 pm

if you put the sinew on,, it will probaly be safe to pull the bow further and get you 40#...

all that being said, if the bow is long enough,,,you might be able to pull it to 28 and get your 40# and do nothing,, I like the idea of at least a rawhide back though..

I think that I'm more naturally in a 26-27" draw so I'm hoping to be able to get over the 40# mark without having to pull into a 28". If it's reasonable for me to go for a sinew backing with enough research then Id love to do that. The other option, is rawhide back it and just accept it for being a under 40# bow and then begin the process of learning to make my own bows to eventually make a bigger game hunting bow. Which I do want to move towards either way...

Pat B · « **Reply #4 on:** September 13, 2020, 03:48:27 pm »

Frets or chrysals (both compression fractures) are caused by over bending a small area on the belly side of the limb. What it does is pushes the wood fiber into itself causing it to crack. These are visible as small squiggly lines across the belly in the overworked area. Some woods are more susceptible to fretting than others but any wood can fret if over bent. Locust, even though it has some of the highest compression values of many North American woods is brittle and that make it more susceptible to fretting. One thing you can do to help against fretting on locust and other bow woods is heat treating, scorching the belly with heat. This dries out the belly and adds to the compression values. It may also increase the draw weight enough so you won't have to sinew back the bow. You may still have to do a slight adjustment to the tiller.
You can bend a bow backwards if you don't go too far at one time. On a selfbow the back, the tension side is one growth ring so it can handle a larger degree of bending. The belly generally has feathered grain and those "feathers" can lift if bent too far back but a slight bend generally won't adversely affect the bow. Say the tips of your recurve are 3" past the back of the handle you should be able to pull them to 5" without harming the bow. As the sinew dries and draws the bow into reflex the string will become slack. At that time pull it another 2" and set it aside to dry. In either of these situations you are not overstressing the bow backwards like you would if you pulled it 4" to begin with.

willie · « **Reply #5 on:** September 13, 2020, 05:40:27 pm »

Quote

-When this bow maker said I could ruin/break the bow. What are the main problems he was thinking of and cautioning me towards?

He may have been concerned about the bow being over drawn if you were to attempt too many changes away from the original design.

Just curious if the bow maker is someone who could be of assistance to your bow making journey, either as a source of information/instruction or otherwise. You are correct that tillering is a primary skill that takes a bit of learning.

Quote

-Being that because I haven't made a bow myself yet I don't have experience tillering. And it seems like sinew backed bows require skilled tillering... Is this a reason for me not to attempt the sinew backing process?

well not backing the bow per se, but yes on account of the fact that you will be learning to tiller by trying to improve what presumably is already well tillered.

Have you considered asking the bow maker to help you find a stave that would be suitable to learn tillering with, and keeping the bow he made "as is", for a reference and example and a bow to start shooting and working with to develop the other associated archery skills?

I would be inclined to save sinewing until I have a different bow. Sinew can give some benefits to selfbow designs, but can also utilized with more effectiveness in designs that consider the sinew as part of the design, ie shorter bows for different shooting styles

bradsmith2010 · « **Reply #6 on:** September 13, 2020, 07:04:41 pm »

I like Pats observation, that heat treating the belly may put the bow over 40,,
i would rawhide back if the extra weight is achieved,,

rcoen2 · « **Reply #7 on:** September 13, 2020, 09:20:28 pm »

In this situation the bow maker isn't available to support me in this process. I'm appreciating all of your different thoughts and considerations. I'm remembering now that the bow maker did suggest heat treating as an alternative option to increase the poundage.

I like that heat treating would help protect the bow from chrysals as well as potentially increase the poundage up near 40 or over. Seems like heat treating and then rawhide/hide glue backing may be a solid option considering everything.

Currently I have my bow really well oiled with rendered deer fat. Would that affect heat treating at all?

I'm currently doing some research on heat treating to get better educated on it. Any thing specific I should keep in mind when approaching heat treating in this situation. Will the recurves stay in place? Seems like I would go for a nice even light to medium browned color change across the whole belly... going slowly...

Is heat treating connected to inducing reflex? Should I have the bow in its natural position when heat treating or bent?

I hope to get pictures for you all sometime soon but I'm currently taking refuge from the oregon fires and am not nearby my bow.

*I guess one concern I have now that I've learned more about black locusts proclivity to developing chrysals, is that making any adjustments that may require re tillering such as heat treating and/or backing would put me in a situation where likely some re tillering would be needed... and me not yet having that skill could be a set up for a not properly tillered bow.. and thus fractures..

*I'm also reading that its not recommended to induce reflex while heat treating on a bow that is already shot in... which I think my bow is...

bradsmith2010 · « **Reply #8 on:** September 13, 2020, 09:32:04 pm »

dont heat the recurves,,

Pat B · « **Reply #9 on:** September 13, 2020, 09:40:32 pm »

It will help if you have a form while heat treating to support the bow and you can add a little reflex at the same time. The deer fat will probably be forced into the wood as you heat treat. Be sure to heat treat before adding the rawhide backing. Keep the heat in the working portion of the limb and away from the recurves. Reheating them could cause them to pull out. And, give the bow plenty of time to cool before straining it. I usually give it over night.
Sorry to hear you are a fire refugee in Oregon. Be careful and stay safe.

rcoen2 · « **Reply #10 on:** September 20, 2020, 02:43:31 pm »

Okay, here are pictures of the bow. Currently planning to heat treat it in the next couple of days. And then maybe rawhide back it. One thing I am noticing about this bow, as I do more research and learning on bows.. is that this one has some curves/twists in it. It seems like these curves/twists are something that other bow makers might have chosen to work out with heat?

And If I were to heat treat this bow with a gently induing of reflex (maybe like a 2" block under neath the handle and then clamp down the ends) would that have any potentially problems with the way the bow has these asymmetrical curves/twists? Would it be wiser to just heat treat without induced reflex?

Would love to hear thoughts on the bow from what people see