sinew delamination

[Whiskeyjet]

So, I have been picking up and putting down a bendy handle ERC with sinew for a couple years now.  I never really get around to finishing it.  I re-sinewed it last March or so (I had previously removed my first sinew back in hopes of doing a better job), and used some sinew wraps to cinch it near the bumps and such in the hope of it not pulling up. Well, today I decide to put it on the tiller and see if I could edge toward finishing it finally.  Was bending nice it seemed, but lots of ticking noises.  And it wasn't the glue I guess, its pulling away in a few spots and releasing the wood back into its natural deflex on that limb.  What are my options here? Can I glue it down and wrap it better? remove all the sinew and try again? Thanks

[PatM]

Best to soak it off.  Looks like your surface was contaminated.

[Whiskeyjet]

The whole thing you think Pat? or just the limb thats having a problem? Can I glue it back on as one piece? or do I need to re-process it and start over?

Thanks

[PatM]

Better to just start over.

[bownarra]

Yes that looks like a poor bond best get it off.
If you can get it off in one piece then yes you could glue it back in one piece.
Best to flatten any bumps/humps/dips on the back and make it smooth, then sinew it.
Get the surface smooth then use five coats of nice thin glue to size the back. Heating the back a little will help but don't heat the glue to speed drying. IPrevious layers can be warmed once properly dry.
Once the back is shiny from the sizing you are ready to glue the sinew on. Use 25 - 30% glue for the actual 'glue-up'.
It would be wise to wrap it while drying.
Good luck.

[bassman]

Looks like you will have to shape the bow again to your preference after removing the sinew, and sinewing again. Good luck. What kind of glue are you using? Maybe try Knox  gelatin this time around also, and wrap it.

[bradsmith2010]

one time I had some back sinew that was a little greasy, and didnt clean it enough,, it came off in one layer,,

[Whiskeyjet]

Looks like you will have to shape the bow again to your preference after removing the sinew, and sinewing again. Good luck. What kind of glue are you using? Maybe try Knox  gelatin this time around also, and wrap it.

Yeah I used Knox and wrapped it. The back still has some lumps and bumps and I think as the sinew shrunk it pulled up because of those high points.

[Pat B]

How did you prep the back before sinewing the bow? You could have put finger prints or some other contamination without knowing.  I had this happen to a bow I built early on. I tried using TBIII which held the sinew down but I didn't like the end results. That's when I started scrubbing the back with warm water and Dawn and rinsing with boiling water then immediately sizing the back with hide glue while it was still wet. I let that sizing dry and sized again before laying down the first layer of sinew. I think it is important to do this cleaning and sizing as soon as possible to prevent any contamination. Be sure your hands are clean too. Dawn and hot water does a good job of this. I've never has sinew lift since I started doing it this way. 
I agree with the others. I would soak off the sinew, separate it and start over from scratch.

[Whiskeyjet]

How did you prep the back before sinewing the bow?

I scored the back with sawteeth. The back was not uniform
Though, it was unviolated and had lots of waviness, especially around knots. I don’t recall what I used to clean it, I usually use acetone. Most of the lifted stops were near areas where the back is uneven, but sometimes just along the edge.

I ended up pulling it all off without having to soak it even, so the bond was just terrible. I filed down all the high spots, leaving a very uniform but very violated back. Scored it, cleaned it with acetone for sure. It’s a very aromatic piece of ERC. Presumably that means it has more oil in the wood than usual perhaps. Shredded the sinew apart again and reapplied it yesterday. Wrapped it in vetwrap and expressed out some glue, going to re wrap it.  Trying to decide if I should just leave it wrapped to hold the edges down while it cures, or just run the heat gun over it again to get any remaining excess glue out. Leaning towards leaving it wrapped, as the wrap is breathable.

[bradsmith2010]

I dont think acetone is as good as soap and boiling water,, or ashes and boiling water ,, or lye and boiling water,,

[bownarra]

Degreasing is a bit of a falicy. Don't worry tho, personally I'd sand the back and then use a very sharp scraper to get it as smooth as possible.  You'll get the best possible bond that way.
So the main thing is that you warm the back and apply a few coats of very thin glue to size the back. 5% glue is strong enough. Keep appling coats, with unforced drying inbetween, until the back is glossy. Use 25 - 30% glue for the first sinew layer.

[bradsmith2010]

  I think its important,, but even Jay Massey that recommends degreasing osage with lye and water,,, ,says he has  not had a problem, when he did not,,
Jim Hamm recommends degreasing the back as well as Laubin, these are guys I studied when learning so still follow their advise,,degreasing and cleaning the back wont have an adverse effect on your process,,if you so choose to do so,,
   
   
   

[Whiskeyjet]

I dont think acetone is as good as soap and boiling water,, or ashes and boiling water ,, or lye and boiling water,,

Yeah I'll probably use soap next time I sinew.

[Marc St Louis]

I usually only do a  light sanding of the wood before sinew backing