sinew over an oil finish

[DVSHUNTER]

I have an osage selfbow that I made about a year ago. After the first 500 or so shots, it developed a crack in the back. It was super small, and came from a stiff spot in my tillering I think. Anyway, I ended up wrapping the spot with ff string and two-part epoxy and went back to the bench and fixed the stiff spot. Well after a few hundred shots more I was looking and another tiny crack appeared just under my wrap. I don't know if it is just a bad piece of osage or what. I followed the ring well and took my time tillering. I guess it might still be stiff. I would post pics, but the cracks are so small that they won't show up on my camera, and I don't want to draw it again until I fix it.
I want to sinew the back now, but I have a wax/oil finish on it and was wondering how I should prep the back to accept a good bond between the sinew and wood. Thanks dave

[tah-gah-jute]

i would think all the oil and wax would have to be removed.maybe you could lightly scrape it and sand or rasp roughing up back a little.without violating ring.and clean with acetone let dry before applying layer of glue on back let dry then add glue and sinew.

[Pat B]

The hide glue has to hold fast to ans penetrate into the wood. You will have to remove the finish and be sure all the oil is out of the wood surface. Might be easier to make a new bow.
  Are the cracks running with the grain or across it?

[DVSHUNTER]

they are running  across it. I was thinkin I would have trouble getting the oil out.I will try to get a better pic, but it is a small crack and doesn't show up in the pictures. I'm leaning towards taking off the wrap and extending it. I think twopart would grab  the wood.

[Pat B]

Cracks across the back indicate to me that the back is failing. Might be from unseen rot or over stressing. I think I'd wear a helmet and athletic cup for the next 100 shots. d;^)  
  If it were mine, I would set it aside and start another. Lots of time and effort goes into a good sinew backing. You may be able to add a hickory backing and get away with it though.

[DVSHUNTER]

are you offering to shoot the next hundred pat? ;-)  I can't let this one go. She is special. Maybe after I fix it I will retire it. Until then... Helmuts don't sound to bad. I'm thinking it is probably overstressing. After I take off the string repair I will retiller it a bit to take off more stress at the beak. It might still be savalagable.

[Frank]

If you must fix it try this.  Acetone wash, multiple times.  Take all the epoxy off and when you think you have wiped it down with acetone enough times, do it two more times.

I have done this before and it does get the oils and finishes off the bow.  Don't forget to rough up the back of the bow prior to sinewing, I use a course file.  Oh and after you rough it up, acetone wipe it one more time.

The areas that have the cracks, I would add a little extra sinew to both limbs equally, take the sinew an inch past in both directions.  Then do a decorative wrap on both limbs so they look the same.  

This is what I would do.

Good Luck.

Frank

[DVSHUNTER]

acetone acetone acetone it is. Thanks for your thoughts all.

[John Scifres]

I know a couple things here.  

The first is I have had a hard time on really oily osage getting sinew to stick even after an acetone wipedown.  Some argue that acetone merely freshens the oily coating by drawing fresh oil from deeper in the wood.

The second is that I'd still give it a try.  Use a tiller tree for the first couple hundred pulls to full draw.  Also, if you are going to wrap it anywhere, make sure the tiller is good in those areas since you'll have little opportunity for adjustments after the fact.  It's really obvious when your sinew won't stick.  It'll probably come up in a sheet.  Which you can reuse by the way.

[loyd]

how long is this bow,if the cracks are going side to side i wouldnt waste good sniew on it sniew will not help much on a longer bow, sounds like you just need to let jerry play with it for a while. sorry loyd

[DVSHUNTER]

I am definitely goingto try to sinew it. Espcially if I can reuse the sinew after I try. The bow is 60in ntn. It is 1½ in wide at the fades and ½in at the tips. I already took off the wrap over the first crack. They are both so small it really hurts me to see em. It is more like a splinter that has not lifted. I think I will put it up for a month and take it to ojam with me. John and pat, thank you both for always being quick and honest with your help. Everyonehas just reinforced what I was thinking.
loyd, jerry was here the other day. I wanted to let him shoot, but I know better. I have a great set of copperhead skins that I want to put on this bow. I am glad I waited to put em on now. Maybe at MOJAM this year.

[Pat B]

It is always a good idea for a wood bow to be well shot in before dressing it up. Lot's can happen in the mean time and it would be a shame to waste good skins due to a possible failure.
  When I building wood bows, the handle and tips are the last thing I shape. I don't need either to tiller the bow and why put the work into it if there is a possibility of a failure. With wood bows, there is always a possibility of failure!

[DVSHUNTER]

very true pat. Just as I thought I had it fixed. I hunted and shot it a lot so it itsnt a total waste if I can't fix it.  I still have another one to shoot. Not to mention about four ready to build and about a dozen good staves drying..

[Pat B]

Sounds like you are well hooked! d;^)

[Roy Steele]

I also just build another bow.