does adding more sinew raise draw weight ?

[TimPotter]

Correct me if I'm wrong but isn't Polly water proof? I'd think it would effect the curing time of sinew as it would seal it off from oxygen too soon. But hey to each their own. As to draw weight increase the answer is yes. A properly layed course of sinew can raise it by 5-10#.

[mullet]

Poly is water resistant, and it does slow the curing process. I've had to retiller some bows with sinew overtime that were not sealed with polyurethane.

[Pat B]

Nothing will prevent sinew or wood from changing M/C as the R/H changes. Both are hygroscopic and that means they take on and release moisture to the atmosphere as the R/H changes.
 My Massey Medicine Bow(sinew backed hickory) has changed weight from 45# to 65# depending of the R/H at the time. That bow was sealed with Massey finish(2ton epoxy thinned with acetone), 5 coats of Tru-Oil and a spray of satin poly.
 

[TimPotter]

Thanks for the info. I know of some who apply sinew with TitebondII and III and as a protective backing I see it as fine, but I much prefer hide or sinew glue and then set it aside to cure for a time then maybe sealing it with something water proof. When you think of it the birch-bark wrappings done on the ancient bows and even the snake skin were water barriers.

[rockrush69]

I have so many bows that have been backed with sinew its rediculus and 2 of them are hickory . I have never wieghed them during moist and dry times.  But i have never noticed a change.  Looks like im gonna need to check on this ... i definatly belive you . Because number one hickory and si ew both suck water up like crazy . And number two . Well .... you guys are respected members of this site . Who are very good bowyers . And yes . Poly slows down the process . But nothing really totally seals anything period ..... im sure it may help with the moisture changing the bows weight from day to day though . As it slows this down ....

[Blaflair2]

Can u seal the sinew with a layer or two of super glue

[mullet]

I took Pat's Medicine bow hunting one morning near the Kissimmee River and shot a hog with it. No doubt it was shooting in the 60# range. By afternoon with the temperature and humidity climbing I had to park it for the Benelli. It was shooting my arrows to inconsistently to hunt with.