Sinew lifted

[razorsharptokill]

This bow has been chugging along for years, sinew backed Osage. While I was shooting it today I heard a tick at the shot and the arrow went way off target. Felt weird. I looked the bow over and noticed the tiller was off on the lower limb now and there is a separation of the sinew from the back. Here are some pics. Could I get some glue down in there and clamp it?

[PatM]

Better to soak it off and re-do it.  The glue surface was  likely not ideal so just trying to put some glue in there is repeating the same scenario.

[razorsharptokill]

It is also snake skin backed. Will that make a difference in soaking the sinew loose?

[Pat B]

The glue type will matter.

[bownarra]

If you used a collagen based glue it is quite easy to fix.
First prepare some very hot 5% glue you could also add a little alcohol. Also heat some glue around 10 - 15% solution. Do not use thicker glue!
String your bow backward very gently, just enough to allow the sinew to 'lift up' and give you easier access.
Use a hair drier to gently warm the affected area of the bow. You want to take your time and get the area hot to the touch.
Once it is nice and warm use a syringe to completely flood the area with the thin glue. You can flex the bow a little to work the glue into the area and in particular the ends of the lift.
Then quickly inject the thicker glue into the area.
Wrap the area with saran wrap whilst still hot. Then wrap with some inner tubes strips about 1 inch wide. Don't go mad with the pressure the heat and moisture will have softened the sinew a lot, you just want everything in contact.
Allow the bow to cool and the glue to gel.
After a few hours remove the wrappings and allow the surface to harden off. Then you can wrap with a strip of t-shirt fabric but it shouldn't need it. The gelled glue holds everything in place perfectly.
Allow it to dry for 3 weeks or so in 50% humidity.
Clean off any excess glue and tidy up.

[razorsharptokill]

I removed all of the sinew and snake skin backing. I would rather start fresh than risk a re-occurrence. I was planning on hunting antelope with this bow in Wyoming next year.

[bradsmith2010]

The process for the fiix seemed very positive,,.but don't think u can go wrong with re do,,,May be that part of the bow was not degreased enough...I clean with lye,,boiling water,,.and don't touch it ,,.make sure and size it well,,.use the best grade glue,,.some say Knox is very consistant

[Pat B]

I agree with Brad about prepping the surface. I use Dawn dish soap and hot water then rinse with boiling water. I do this just before laying the sinew down to be sure there are no finger prints and by using water you prime the wood to accept the hide glue, basically breaking the surface tension.

[bownarra]

No need to 'degrease'. If you look into it you will find that no matter what method you use to remove oils from the surface of wood you simply bring more to the surface. Honestly check it out It's one of those commonly held myths.
I've sinew backed plenty of osage, made hornbows with osage cores and not 'degreased' any of them - no problems. If you can glue horn and sinew to a hornbow core that will be significantly more stressed at the gluelines then ANY wooden bow could ever be without washing then I know that no wooden bow needs it.

The most likely causes are improper prep of the back eg. sizing and heating the surface. Also it is well worth scoring the back with a toothed scraper. A lot of people sand the back with 60 grit or similar BUT again that doesn't really cut the mustard. Get a new 16tpi hacksaw blade and use that. Sandpaper will leave lots of rough areas that actually end up holding tiny air bubbles. Look for some of the older articles discussing cabinet making/glues from the old days before epoxy. There are some good papers out there that explain all this stuff fully.

[bownarra]

Also with all these soaps check out the ingredient list....

[bradsmith2010]

I think its good to de grease,,,even with rawhide backing,.

[Pat B]

I agree with Brad again. We have different methods but the same results. It's not necessarily the oils in the wood but finger prints and other hand oils that may get on the surface. I do this with rawhide and snake skins and other soft backings. On hard backings like boo or hickory I give both glue surfaces a good sanding and brush off the dust just before adding the glue.

[PatM]

Always degrease oily wood.  It just makes sense.