Issues with truoil over sinew?

[High-Desert]

I just finished up a short sinew backed yew, 52” long Modoc style. I sinewed the bow this last winter, and it sat for several months before I finished tillering. I took the bow out and shot it quite a bit, and reflex was held. It sat for several more months before I finally got the earth pigment made and I decided on a design. I painted it and coated in truoil and let it sit a few weeks. I then took it out to shoot a few arrows, and when I unstrung it, the top limb had lost its reflex, and it hasn’t returned. Has anyone had issues with a coating doing this? I wasn’t sure if the truoil imparted moisture to the sinew or what. The bow shoots fine but the look of one limb reflexes drives me crazy. Any thoughts?

[burchett.donald]

Eric,
       How many layers or how much sinew did you use?

[Pat B]

Tru-Oil is a linseed oil based finish so I doubt it added moisture to the sinew. What did you use for the carrier of the pigments? Hide glue? If so that might be the culprit. Was the bow stored in a dry environment?

[half eye]

Eric,  this is just a guess so take it for what it is worth, OK? You did not say weather the reflex came because of pre-shaping or drying of sinew and I sure have not seen your bow but I'm guess ing that you had a small partial delamination somewhere along the limb....not the whole thing  maybe two or three small spots...that would allow the lower limb which has more early weight now pull out the reflex....but...it cant be a total delam because you indicate  that it shoots well. Seems logical that the sinew is still working on the 3/4 to full draw so the sinew has to be still be in one piece and the ends (at least) are still tight to the bow.
    You did not say what medium you used to mix your paint either so another guess would be that you got some infiltration of water or oil in through the thin edges enough to cause some spotty delamination. One other thing is that when you first started the sinew job your "prime coat" of hide glue had some bonding issues, or not enough so there were air pocket "dry" areas that in turn allowed the moisture in.

Like I said I haven't seen the bow so consider the abouve as a WAG
rich

[High-Desert]

I put abou 4 layers of sinew on, 3 oz of sinew. The carrier was acrylic, and it dried several weeks before coated with truoil.
There was a small section that delayed, about 2” long and 6” from the top, nearly a non working section of the limb, that doesn’t correspond to where the reflex pulled out.
I used PatM’s sinewing method, which worked great, probably my best sinew job. It nearly turned it clear. The climate here is always very dry. I can’t even sinew in the summer without everything glorying to fast.
The reflex was pulled in

[High-Desert]

Heres a side profile pic. The right limb is the issue

[BowEd]

Nice picture to help explain your concern.Very nice looking bow!!You say your tiller nor your poundage has changed?I feel you may have possibly heated the area of delamination too hot or too many times while wrapping to starve it of hide glue and becoming too dry.Also a laying on of sinew on a flat area where it came loose could be a contributing factor of delamination.Resting profile shows it possibly was'nt an extremely reflexed bow to begin with.Flooding the area of delamination with thin hide glue and alcohol/reverse string/and pressing the area down after gelling should fix it but not too long to where it gets dried.I would wrap sinew on the ends also then.
Nothing was said on how thick your dried sinew layer was.3 ounces dry sinew on how long of bow?Sorry just reread the length of 52".3/16" thick dried sinew can take up to 6 months to fully cure.

[High-Desert]

Thanks everyone for your help. Maybe I did hear it too much. I just don’t understand why it was fine after I shot it a bunch before it was costed, and it showed no loss in reflex. There wasn’t much reflex, about 3”. The poundage went up from 52 lbs to 58 lbs from the first time I shot it. The delam occurred about three months after sinewing, when I moved the bow from my reloading room, which is 65 degrees/55% humidity to my shop, which is 60 degrees and 30% humidity. Every one of my bows his some delam ever since I moved to the desert. I try my best to keep them in the most humid room I have for a few months.

[BowEd]

Thanks everyone for your help. Maybe I did hear it too much. I just don’t understand why it was fine after I shot it a bunch before it was costed, and it showed no loss in reflex. There wasn’t much reflex, about 3”. The poundage went up from 52 lbs to 58 lbs from the first time I shot it. The delam occurred about three months after sinewing, when I moved the bow from my reloading room, which is 65 degrees/55% humidity to my shop, which is 60 degrees and 30% humidity. Every one of my bows his some delam ever since I moved to the desert. I try my best to keep them in the most humid room I have for a few months.

Any more when I sinew a bow to over 1/8" thick dried layer I let it cure 5 to 6 months.I hate reillering it back down to desired poundage.Although as long as I don't pull past my desired drawweight while taking poundage off I don't lose any reflex then either.
When I put on snake skins or birch bark over the sinew I will reverse brace it a tad again and let it dry a good 2 weeks before finishing it up and bracing it.
I would suggest in the future to use a touch more glue along the way with your sinewing procedures,and just spit balling here to use a little thicker glue.Normally with mine after weighing dried on the bow my glue to sinew ratio mass weight wise is around 1/3 glue to 2/3 sinew.Possibly raising that ratio a little higher on the glue.
Regardless you've got a nice bow there.Congratulations.
To go farther on here I am a fan of Pat M's method posted by him for getting nice wasteless[sinew wise] smooth sinew jobs done from wet stripping sinew,but I still don't mind dry stripping sinew and love the way glue will infiltrate the dry tendon stripped sinew very well.It will look like one matrix of sinew and glue and a person will hardly be able to see any sinew lines in there.If the wet stripped sinew is flooded with enough glue prior to gelling and then wrapping and heating that matrix can be achieved though too.
After sinewing the usual way of dry strippng sinew and glueing and then using Pat M's method it can have a little learning curve to it getting used to.

[High-Desert]

Thanks Ed, I really do think my glue solution was too thin. I will hav to try again using a varied technique.

[BowEd]

Thanks Ed, I really do think my glue solution was too thin. I will hav to try again using a varied technique.

But meantime I'm sure the lifted sinew can be repaired on your bow.

[bradsmith2010]

I live in the desert too,,
maybe let the bow cure in the environment it will be shot in,, I am just guessing,,
I was thinking also,, taking some bundles and glueing seperate ones to a board,, then coating one with acrylic,, one with true oil,, one with tung oil,, one with varathane,, lettiing them cure then pealing them off to see what happens,,
I have spayed varathane on the sinew,, then painted with acrylic, thinking the varathane would keep some of the moisture out,,
I have tried lots of different things ,, trying to figure whats best to put on sinew,, and still experimenting,,
I think if you gonna paint with a water base ,, maybe do it sooner than later so it does not induce moisture into the sinew,, but will just cure as the sinew is curing,,, I am just spit balling too,, that being said I have had bows,, change tiller for no reason I could figure out,,and sometimes I think a sinew bow is slow to reveal its true self,,