time between sinew?

[uncleduck]

I planning on sinew backing for the first time and was wondering what time period is required between layers or do you do all the layers at once? All I could find was to wait at least a month after sinew before finishing the tiller work. Thanks

[JW_Halverson]

I don't think it matters a whole lot.  If the surface of the laid up sinew has had time to dry enough to be sanded, I recommend a little sanding before the next course is laid up.

The main thing is to allow lots and lots of time for the sinew to cure out fully, and then more time for the wood to cure out the moisture that it has taken up from the sinew.  I liave in a dry climate and I swear any tillering I do before the 3 month mark is going to change anyway, so I leave it the heck alone. 

[steve b.]

I only do one layer and I agree with JW that you cannot wait too long.  I've removed sinew or had it pop loose after a couple of weeks and the glue underneath was not as hard as it is after a month or so.  And don't try to force cure it by drying it with heat.  It's like concrete; it has to age in order to cure properly.  If you don't need really heavy layers of it, and since its your first, I would recommend doing one heavy layer.

[osage outlaw]

I have tried it both ways and didn't see a difference.  The last bow I backed I put two full layers and one strip down the center all at the same time.  Then I let it dry for a long time.  I like to sinew a bow each winter and then put it away until summer.  By then it is good to go.  I think using the right (hide) glue and using the right amount makes all the difference. 

[gstoneberg]

I normally do 2 courses at a time.  I want to be sure all the sinew endings from the first course are covered.  The shrinking sinew (assuming you're using hide glue) exerts a lot of force on the bow back and I want it as even as I can get over the limb.  I have tillered a sinew bow out in as quickly as 2 weeks, but you get a better bow if you go much longer than that.  If you wrap the bow with an ace bandage like I do, be sure to remove it after about a day or you'll have trouble getting it off.

Good luck,

George

[mikekeswick]

Here's how I do my sinewing.
Put the first layer on at only 1 - 2mm thick.Appy it evenly everywhere. Allow 1 week to dry.
Put 2nd layer on again only 1 - 2mm thick. Start to form a crown on the back by putting more down the center. Allow 1 week to dry
Then on the last layer I will concetrate on getting a nice crowned back by laying most of this layer down the center. The bow will be ready to tiller 2 - 3 weeks after the last layer. Of course the best thing is to leave it for a few months but sometimes it's hard to wait.....
By keeping the layers thin they only take a short while to dry. The amount of time sinew takes to dry rises exponentially with it's thickness.

[Pat B]

I'd give at least a week between courses and at least a month after sinewing before stressing the bow.

[Scaramouche]

How much difference does the relative humidity of the area matter in the curing time? Phoenix vs Seattle; I'm guessing there'll be some difference?

[Pappy]

I usually do 2 or 3 courses and put them all on at once,then a month or so in a good dry place,not a hot box but a low humidity place with air moving if possible. I make sure to squeeze all the access glue from it between my fingers before putting it down. I would say Scaramouche it would make a big difference,more humid the slower it would dry.
   Pappy

[Pat B]

Scaramouche, I've had sinew backed bow go from 45# to 65# depending on the R/H of the area it is in. On one I made it 56# and a month later when the humidity was up it went to 45#. I sent it to Colorado and a month later it was 65#.

[BowEd]

I found the more you can get your fresh wet sinew job to be smooth it will be even smoother after it dries if you want to put a covering on it of some sort.Less gaps,furrows etc.Nice straight lines.Size your wood well prior to applying sinew.Have everything ready so you don't have to scramble.Squeeze hide glue from sinew well after dipping it as Pappy said.I presoak my sinew in water first.I never wrap mine and have hardly any noise at all after first initial bending of limbs.It might sound a bit complicated but it really is'nt.You can get as technical about it as you want.Preweigh your dry sinew in grains,measure the length of limbs and divide it ending with so many grains per foot of limb.If your calculations end up 150 to 250 grains per foot you can expect some good action from your sinew job just make sure you put same amount of piles on each limb.
I was wowed by the amount of action sinew gave me the first time.Good Luck.

[BowEd]

Oh if you choose to sinew week by week.Sand and resize each time.

[Scaramouche]

Scaramouche, I've had sinew backed bow go from 45# to 65# depending on the R/H of the area it is in. On one I made it 56# and a month later when the humidity was up it went to 45#. I sent it to Colorado and a month later it was 65#.

Did those weight changes occur after the glue had already cured? Or was that in the process of curing?

I know a little about how the wood reacts during a change in r/h. Could those changes have been caused by the moisture content of the wood itself changing?

[PEARL DRUMS]

I apply all my layers with real hide glue, usually 2 or 3 at one time and let it sit in a room/area that is in the 40-50% humidty range for 3-4 weeks and finish tiller it.  I like to get the tiller right at 20" before I sinew bows. No suprises.

[Pat B]

The bow I was speaking of was completely cured out. It was sinew backed hickory and both the hickory and sinew/hide glue are hygroscopic, meaning they take on and release moisture to the atmosphere depending on the R/H.
 Even today the bow changes depending on the R/H. It has been probably 8 or so years since I built it.