Equilibrium MC for sinew?

[upstatenybowyer]

Wondering... if one can periodically check the weight of a roughed-out stave to determine when it has reached equilibrium MC, can the same thing be done after sinew is applied to determine when the sinew has cured? Maybe with sinew loss of moisture is on too small of a scale to be measured in ounces?

[Pat B]

Moisture loss is moisture loss. When you sinew back a bow the wood and sinew become as one and the moisture from the wet sinew moves into the wood and they both dry together.

[BowEd]

That's a logical question,and it crossed my mind too in the beginning of bow making.Curing of sinew time is on a different type of scale time wise than wood.Other experienced users of sinew can comment better here too but sinew will continue to shrink as opposed to wood I think.It's the thickness of sinew that's applied that determines curing time.Hard to know exactly how much moisture is still in the wood too.It's kind of sealed over with the sinew.
Conditions it's drying in can make a difference too.Generally 6 to 8 weeks of waiting before tillering can be ok with moderate weight gain of just a few pounds after that with 1/8" thick sinew.Better yet at 12 weeks though.Your gonna hear opposing time ranges and earlier tillering times but generally I'm not too far off.Just tillering it early is one thing but continued use of the bow will reduce it's reflex.For just a thinner protection barrier as insurance of breakage earlier tillering times can be done I would think.

[loefflerchuck]

Sinew and high quality hide or fish glue form more and more complex bonds over weeks and months. This is very important in highly stressed composites but not so much with wood bows with thin sinew layers. One of the most important reasons for not touching a horn composite bow for at least 6 months is the bond by that time has formed such complex and powerful bonds that you can make corrections for twist and tillering using heat. Enough heat to make the bond fail in glue that has not seasoned long enough. This is also the reason why no modern epoxy or glue can hold up to composite construction.
  I have made wood bows with as many as 5 layers of sinew tillered in only 10 days. Even shooting the bow this soon the reflex and draw weight continue to increase over months. The biggest problem is if you tiller the bow in 10 days that tiller will keep on changing until the sinew has seasoned at least 6 weeks.

[mikekeswick]

I completely agree with the above but there are modern epoxies that will work and hold on with high temps. Look into laminating epoxies for high temp final applications. I have some now that will take 190 deg Celsius when fully cured.
I'm not saying that these are better than collagen glues just a different option. They are pretty specialised but worth knowing about.

[Stick Bender]

When I did my first sinew bow I read every thing I could get a hold of and found out 1 size doesent fit all there where so many different opinions & exsplanations why ,I had to go with what seemed practical the first one I did 4 weeks  73 F @ 45 RH turned out fine the second one did the same but only 3 weeks & it was still a little green I think it depends on drying conditions, at the time I was only working 1 bow at a time so it seemed for ever, the one I'm working on now I'm going to try 6 weeks same conditions & see if there is a difference . Also I think it's over looked as to what type wood is used the hickory one seemed to take longer & did not ad as much sinewed pulled reflex with osage my guess is you could probably get away with less time then white woods but don't really have any facts to back that up.

[BowEd]

upstate...Bottom line is as far as mass weighing it will not determine dryness or seasoning of sinew.Changes in weight that even a grain scale won't measure.Larger scale sinew jobs are a commitment and the waiting is like waiting for christmas as a kid.Reading into Adam Karpowizs' time frames for thickness seasoning times are a good referral to go by.
I have steam bent laminations of wood bonded with smooth on epoxy and they have held though.The specs on the glue say it can withstand it.I mentioned this earlier in a thread.Tite bond 3 will not do this but still is a very good glue yet.Just food for thought here that's all and options used in different types of situations in bow making and different types of bows.

[upstatenybowyer]

This is a great thread. Thanks to everyone for their input. And dig this... I'm currently waiting on a bow I sinewed and it will be exactly 6 weeks on Christmas! If that isn't a sign what is?

[loefflerchuck]

Thanks for the correction on the heat and modern epoxies Mike. I'll stop making that claim, but still like the idea of the magical bond with animal proteins connecting with horn and wood.