What did I do wrong???

[osage outlaw]

My sinew backing started to pull loose from the bow that I am working on.  This is my first attempt at using sinew.  The bow is a 60" osage selfbow.  I used knox gelatin for the glue.  I think that I didn't degrease the bow enough.  I used veg. oil while heating it.  I wiped it down several times with a rag soaked in acetone before putting the sinew on.  I tried to save it by wrapping it with some back pieces, but it kept coming loose in other areas.  I went ahead and cut it on the handle and peeled the sinew off.  It came off pretty easy.  The glue held the sinew together, just didn't hold it to the bow.  I want to sand it down and try again, so any advice or help would be great.

Here is how it was pulling loose









Here is the underside of the sinew layer



Here is the back of the bow.

[yazoo]

I think the oil penetrated the wood a little,,when you degreased the back,,some more oil came to the surface,,you must make sure that you keep a layer or two of shellac on the bow to prevent oil from soaking in or dont use oil when you plan on sinew backing,,,mike

[sonny]

did you size the back with two or three or four (not kidding) thin coats of glue before you applied the sinew ??
I learned that lesson the hard way several years ago when I applied sinew to a buddy's bow and it subsequently pulled free.
now I know better.

moral of the story- the back of the bow should be shiny with glue before attempting to sinew back it..........

[ricktrojanowski]

I would skip the knox and use some hide glue.  Also really degrease the back with acetone well and scuff it up.  Also make sure you size the back with a couple layers of glue before applying sinew.

[billy]

HEy Osage,

You have to rough up the back I use a hacksaw blade), and then scrub the back very well with a stiff brush and hot water and dish soap.  I've had the same problem when sinew backing osage because I didn't de-grease the back properly.  Osage also has a resin in it that will prevent glue from sticking, so you really need to be sure you degrease it very well.  However, I really think sinew is useless on osage because osage is plenty strong and doesn't require sinew anyway.

I've used knox gelatin and it is plenty strong and does a superb job of binding sinew to wood.....if the back is prepared and cleaned properly.     

[sulphur]

i bet sonny is right.  the best gluing procedure for any glue is to apply it to both surfaces.  The knox should work fine.  I however, do you hide glue that i bought at wood craft.  its not too expensive and is high quality.  its made by brehen i think.

[venisonburger]

I'm with billy, hacksaw blade scraped across in an X pattern to give the glue something to grab to, and better degreasing.
VB

[Pat B]

I'm getting ready to repair a sinew backed osage bow I built in 06. I used Knox, used a toothing plane to groove the back, de-greased with acetone and had the sinew pop loose in sheets. This bow, Elkie, had many hundreds of shots through her over the last few years.  My redo will be to degrease like Billy said with dish detergent(Dawn) and hot water and I will use a good quality hide/fish glue and size the back quite a few times before adding the sinew.
  Keep us posted on your results and I will do the same. 

[osage outlaw]

I sized it with one coat of glue.  I roughed the back a little with a hacksaw blade, but probably not enough.  This bow has thin rings so I was afraid to rough it up too much.  I think the knox was plenty strong enough.  I can bend the sheets of sinew in half, and they don't even crack. 

So if I got it right, I need to degrease better,  rough up the back some more, and put 4 or 5 coats of glue on for sizing.

Thanks for the help.

[osage outlaw]

When I size the back 4 or 5 times, how long do I let each coat dry?

Also, in TBB the chapter about sinew says that you can put two layers of sinew down at once, instead of letting each layer dry.  Has anyone tried that, and how did it work?

[El Destructo]

OK...I am going to p1$$ people off...Knox is for eating and making your Finger Nails stronger...If you want to back a Bow....use a good Luthiers Grade Hide Glue...they don't make a Stronger Glue than Pure Hide Glue...show me another Glue that that when applied to a Window....when it dries...it will pull shards from the sheet of Glass.......

[VenomBOWslinger]

I would def. rough up the back with some sandpaper the back looks really smooth and having oil on it well thats probably what happened.  All the guys are right assess things and start over you will get it!  Good luck and keep us posted.

Russ

[Timo]

I have never used acetone to degrease a back before sinew. I have always given it a lye bath, and have never had a sinew lifting problem. You can pick it up at some hardware/grocery stores,(probly have to sign you life  away to buy it now though) Of just go down the street to your local meth lab and pick up a bottle or two. Might need some back up, so plan on it.

Read the dangers and follow them. It'll degrease a hogs back.

[artcher1]

Take and put you a couple good coats of varnish on the back of your bow and then re-glue (scuff up finish first) the sinew strips back down with Tite-bond glue. Bet it'll stay put then! ART

[osage outlaw]

Would it help to take the sinew down the sides of the bow a little, or just keep it on the back only?