Sinew backing

[Jjpso]

Hello there! Im in the process of building a osage Sinew backing bow. Some years ago i remember a post or build along, of some one explaining a technique to get a more clean back, and to squezee the excess glue, but cant find that post! Does anyone remember who posted it?
Thanks

[Eric Krewson]

I don't remember the post but if you neatly wrap the wet sinew tightly with saran wrap it will smooth it out and get rid of the usual stringy look, you can then sand to look as smooth as fiberglass.

[superdav95]

I’m not sure if you are talking about my post a while back or not but if you are here is the basic method,   

Prep you sinew.  Comb and separate the fibers how you normally would or prefer by pounding or twisting depending on if using back sinew or leg sinew.  Once in fairly small fibers separate into piles of short med and long lengths.  Then weight it into separate bundles depending on how you want to lay down your sinew wether in a stagger brick pattern or in overlapping wider strips. 

Prep the back of your bow.   Many schools of thought here but for Osage in particular I would wash well with alcohol after scuffing with 60-80 grit paper or use a fine toothed hacksaw blade to make tiny grooves the length of the bow where sinew will go. 


Sizing coats is often overlooked with sinew backing.  There is a belief that it’s only necessary for glueing horn laminate but this is not the case in my opinion.   Especially with a wood like Osage.  When you wipe with alcohol you will notice color come off.  There are oils with this that can make the sinew less adhered.  Proper size coats of thin hide glue can make the difference often with backing with sinew.  I use 5-10% glue meaning if one was to want a 5% concentration you would for example take 5grams of dried hide glue and mix 95grams water then heat.  On a horn laminated bow this coat would be 12-15 times allow to dry in between.  But for sinew backing sizing I do about 3-5 coats heating or warming the back of the bow slightly with each coat. 

I lay wider premeasured strips for each limb that have been soaked in 25-30% glue that have been allowed to gel slightly on a board or a piece of glass prior to laying down.  A generous coat of glue brushed on prior also to laying down.  The strips method of laying sinew does help me to get perfectly aligned fibers combed and shaped prior too.  If the staggered method is your choice just overlap a little at each stagger.  I’ve had good results with both methods. 

After the sinew layer is down and allowed to fully gel up to the touch but not dry I wrap with horse leg wrap.  I leave this on overnight and then remove.  It leaves a smooth clean finish.  I’m sure the Curran wrap method work also but I prefer the breathable wrap.  It’s very thin and has a slight elasticity to it to compress it down well.  The problem I down with the Curran wrap sometimes was trapped moisture.   I’ve also tried ace bandage method wrapped as tight as I can and then putting it out in the sun or heat gun on low setting for about 10mins or so or until I see glue oozing out.  I will use more then normal glue knowing it will ooze out a bit the excess.   I didn’t like this method and found it quite messy and a pain to get the bandage off. 

Hope this helps.  Message me if you would like more clarification.  If you look back on some of my posts you will find more details too. 

[bassman211]

  Some claim that  there is no need to sinew back a longer bow...for me 60 inches and longer, but there is a real advantage  to using it on short bows....38 to 52 inches in my experience.  The above ways explained above work fine for smoothing it out on the back.

[Eric Krewson]

I did the saran wrap thing a few times, I only left the bow wrapped as such for a day or two, by that time the sinew had hardened enough to maintain the smooth appearance but still needed to cure.

[Pat B]

Are you talking about prepping the bows back before applying the sinew or smoothing the sinew after applying it?
 My method of prepping the back before applying the sinew is first have everything, sinew, glue, etc. ready then wash the bow's back with warm water and Dawn dish detergent then rinse with boiling water. In my opinion this wets the bow so it will accept the warm hide glue. Then I size the bow's back with warm hide glue, let it dry and repeat the sizing a few more times. Now it's time to lay down the sinew.
 I do similar to Eric but use strips of old bed sheets to wrap the bow once the sinew is applied and remove that about an hour or two later before the sinew/glue set hard. This will give you a somewhat smooth sinew surface.

[pierce_schmeichel]

I would say Gauz works better than seran wrap because the seran wrap seals the moisture in making dry time much longer. Gauz is breathable and meant to be peeled off of wounds so its honestly perfect. It can leave fibers behind after being peeled off but those are easily wiped off with a ittle warm water, that is if you're using hide glue or some-other water soluble glue(which is all I would recommend using-because glues other than hide glue make bows less powerful)

[ssrhythm]

KOBAN in the med isle of cvs works great for breathable and compressible and easy to work with wrap.  I'm gong to throw in my 0.2 that really helped me on the one and only bow I sinewed.  DO NOT SKIMP ON THE PREPARATION!  Be organized and have a plan and all your stuff together.  I recommend writing out the plan and journaling as you go.  When I started, I took my time and put much effort into separating my sinew into fairly equal length groups of long, med, short.  I then ran small diameter stout sharp nails through a scrap piece of osage and made a sinew separating brush...which was a huge help.  I then worked the sinew with my hands and then that brush to fray it down to as small of individual fibers as possible.  I then traced a rough estimate of the back of my bow and began arranging the processed, fluffy bundles onto that drawing in the manner that I wanted them to be stacked alternating long strips with shorter strips and middle length strips with tips overlapping an inch or more.  I did the middle of the back to tips first and made sure everything was symmetrical top to bottom.  I then placed the next two rows outside of that making sure that the overlapping ends fell well within the center of whatever bundle was next to it...like laying bricks. I continued to do this and adjust to get it all like I wanted it.  Once that was done to my liking, I removed each bundle and numbered/labled them as to where they were going to go when the gluing started.  Keep this part organized.   I then took each bundle in their respective size groups and weighed them.  I'd pull a few strands out of a heavy bundle and add it to it's lighter corresponding/opposite side bundle and repeated this process until I felt that the sinew would be of equal weight/thickness all along the bow with the bundles in the center of the bow and center of the limbs being slightly heavier than what was to be along the edges and further out toward the tips.   

Get your glue right...I used the double boiler or pot in a pot method and a thermometer to keep as hot as possible without damaging the glue or sinew.  Have a plan and execute it.

I roughed/grooved my bow with hacksaw blade then I used a lye solution to make dang sure there were no oils on the back.  I then "strung it backward" and I sized the back with two or three layers of hide glue, and once it was almost dry, I started laying down my strips from the center handle to the tips overlapping and meshing the ends together with a smooth antler tine,  Tried to smooth it out as flat with the least amount of sinew fibers twisting onto/over each other as possible,  Be efficient with this process, as the glue will start gelling fairly quickly.  Repeat this process with the next two rows on each side of the center row and again try to mesh the edges of the side by side sinew with the antler as well as meshing the end to end overlaps.  Continue to do this until back is covered with some rolling onto the sides. I did not wrap and let the first layer dry, but just let it sit there as I weighed out and organized bundles for my second layer.which was one robust center run from tip to tip.  The third layer was a complete layer like the first covering and enmeshing with the 2nd layer which acted to cause a slight crown on the back as well as the first layer.   The hot glue on each bundle melts the glue on previous bundles enough to get them all meshing a bit.  Once the third layer was on, I wrapped it carefully but tightly with coban and set it by my AC at night and out in the sun during the day when the RH was dropping below 8% and I'd bring it back in and put it by AC at night,

I've got exact weights of each bundle and the layers in a book at home, and it was weights based on what very wise people on here directed me to do.  I can shoot you those numbers if you want.  I wouldn't do any sanding to the dried back.  You will want a waterproofer on there, and the wrapped sinew comes out very consistent and fairly smooth once you take the wrap off.  A good sizing of TB3 on the sinew followed by a liberal TB3 gluing on of a quality snake skin will have the back smooth as baby butt with no need to sand the sinew and decrease any structural integrity you just worked so hard to get.