glue, backings, sinew & such

[willie]

What are your experiences with glues and backings other than sinew? Recent experiments may show that sinew and hide glue together do not work as commonly thought. Does this mean that other combinations could use more investigation?

[Bryce]

What’s your source?

[BowEd]

In what ways not as thought willie?

[willie]

In what ways not as thought willie?

it's commonly said that when sinew dries, it puts tension on the back of a bow

[PatM]

How does it not?

[BowEd]

Never without hide glue with it which is commonly understood.We might be looking from different views here.Not sure what you mean.

[willie]

How does it not?

Pat, smooth out some wet sinew, like it would be before putting on a bow. clamp the ends and let it dry. tell me what happens when you release the clamps.

[PatM]

 Clamp it to what?     A flat surface? Between two struts?

[hoosierf]

Here’s my list of backing attempts with some comments on my experiences.

1 - Red oak backed white ash.  The oak over powers it a bit, but a long narrow bow with 2” of perry and youve got yourself a very sweet shooter that’ll take about an inch of set. This combo is a favorite because i can cut my stock to near finished dimensions based on experience and ash is a dream to scrape and tiller.

2 - Linen over about any anything but my most successful was over a wide white oak paddle bow with frighteningly narrow tips.

3 - Flax cord over HHB - good combo but kinda ugly. And it stacks firmly at about 29” of draw. The bow is 1 3/8” wide and 67” long at 46lbs.  Like this combo.

4 - Raw Flax roving over Osage.  It broke as the stave was knotty and had some bug damage. Raw
Flax is very strong and i use it more for wraps as it seems to overpower everything. One of the most interesting things i did with raw flax is to stiffen a bendy handle bamboo osage bamboo ALB.  (As a side note i wrote here once that I used sinew for that but it was flax roving, i just looked at it the other day when my nephew was shooting it)  It was bending too much in the handle so i laid down flax roving from fade to fade on top of the boo and wrapped the ends of the courses with roving. Worked out very well but pretty crude looking.

4 -   Bamboo and Hickory. What can you say?  Tried and true. Always with TB II or Elmer’s Max.

5 - Sinew with Tite Bond II or Elmer’s Max.  I like these glues better than TB III for reasons i can’t explain. TB won’t magically pull a bow into reflex like hide glue but if you reverse string the bow while the glue is curing you won’t be able to tell the difference next to hide glue except by appearance and cure time. It still takes a week to 10 days to reach full potential.  Once the reflex cures in i find it to be indistinguishable from hide glue and sinew as long as you reverse string the bow to cure. If you don’t it does not perform as well as hide glue.

6 - Rawhide - you can have it. It’s saved me from a cut face at least twice but i think it only prevents explosions. I don’t think it makes my bows any stronger or safer.

7 - Sinew over linen. Dumb idea; the linen never allowed the sinew to do its work. Linen over sinew might be cool but unecessary.

8 - I’m floor tillering a quarter sawn 3/16” red oak backing over a quartersawn Osage timber right now. Based on prior experience i have really high hopes for this one. 

I’ve thought a fair bit about pulling strands of bamboo garden stake into fibers and treating them like sinew or roving but I’ve never tried it. One day i will.

I’m conjuring up a silk stretching jig to try a stressed silk back design but have not
Attmpted it yet.

[willie]

Clamp it to what?     A flat surface? Between two struts?

your choice, but a flat surface would give you something to make marks on. Comparative measurements would be nice.

[willie]

What’s your source?

I have moved this over from Eds thread

Ed, I just measured the three grades of glue I used to duplicate he TP test mentioned in the other thread.

weight       water:glue ratio         shrinkage
379                 3:1                       10%
251            2.25:1                        8.5%
251                 5:1                        8.5%    this mix was twice the recommended water
135            1.25:1                        8%


I should note that the three different weights of hide glue, when mixed with the recommended amount of water, had pretty much the same viscosity.

This compares with 17% shrinkage that was reported with knox in the other thread.

I do not know how fair this test is, as the tissue is free to shrink. When glue is bonded to wood, one side is restrained.

I also dried some deer backstrap sinew. the sinew  was restrained somewhat, as I suspected that just drying a strand of sinew unrestrained would allow it to shrivel more than it might if it was in matrix with glue.  Three different pieces showed very little shrinkage. The pieces were placed between two slats of cedar held together with a few wraps of electrical tape. They were stuck to the wood when the slats were separated, and when free from both pieces, measured 1% shorter than the razor cuts made when the sinew was trimmed wet before the slats were sandwiched.   Not a calibrated test by any means, but my impression is that it did not take all that much to prevent shrinkage, so the idea of it being "tensioned" inside a cured matrix seems dubious, and if it is in a matrix with glue that shrinks more, then what does that say about our understanding of the mechanics?

Link to glue specs and info
http://www.primitivearcher.com/smf/index.php?action=dlattach;topic=63182.0;attach=139366

[PatM]

You need to measure the  shrinkage unrestrained or stuck to a material that can actually  be moved by the sinew shrinking.

 Sticking it to something that is stiffer than a strand of sinew has the power to move does not tell you much.

[Bryce]

How does it not?

Pat, smooth out some wet sinew, like it would be before putting on a bow. clamp the ends and let it dry. tell me what happens when you release the clamps.

When it’s clamped down it’s not allowed to shrink. How about you soak it, stretch it. Measure it. Let it dry and measure again. THEN say it doesn’t do anything.
But it will shrink.

[PatM]

Baugh got a measurement of 3% for sinew shrinking.

 Again, it comes down to the matrix combination of materials.

 
 You wouldn't really say carbon or glass seem like very stiff materials if someone handed you  a strand.    Because they are not  really until you add the glue.

 

[willie]

Never without hide glue with it which is commonly understood.We might be looking from different views here.Not sure what you mean.

Let me bring this over from your other thread

Really this brings a thought to mind.If a person ever makes hide glue for themselves they will see the dramatic shrinkage that it does............ Hide glue IMHO opinion has super enhancing qualities with sinew making the sinew even more resilient.

Indications are that the glue does more shrinking than the sinew. Not sure what that tells us about being super enhancing, but examining the process behind your commonly held opinion is certainly part of the reason I opened this thread. Sinew and hide glue work well, no question about it. My thought is that it may not be for the reasons frequently surmised. Perhaps understanding what happens in the matrix can make for better utilization of other combos.