sleek
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sleek
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4:22 PM - May 05, 2018 #21

I was also thinking you may be able to wash the fibersand soak them in hide glue and press it, then use it as a horn substitute for the belly.
Once I was making some paleo mulch from a stick and after many hours was astonished to find myself holding a bow.
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Tim Baker
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1:56 AM - May 06, 2018 #22

sleek:
 
" I was also thinking you may be able to wash the fibers and soak them in hide glue and press it, then use it as a horn substitute for the belly."
 
You're referencing the dried hide glue as belly thinking from my PA postings, likely the toilet paper/glue approach? Your coconut fiber suggestions is worth trying, especially if it can be kept to a very low % of the mix, and allow a uniform thickness.. The main difficulty with such a poor-man's horn belly is getting the glue layer thick enough and uniform. When brushed. on 20 or so coats, with drying time between each, are needed to build up proper thickness, the result somewhat uneven.  Setting gossamer-thin cheap toilet paper on the belly and saturating it with glue yields about 4 brushing's worth of glue thickness, and of uniform thickness. Successive layers build up to any desired thickness. I like this solution because the TP is essentially all air,  the resulting layer maybe 90% glue, the wood fiber in the paper having essentially no plus or minus mechanical effect. Maybe the coconut fibers could be arranged to be even an higher % of air--open spaces, and due to the fiber thickness, maybe a thicker layer of glue per layer. It's worth trying.

About 15 brushed on coats of glue on a 1/2" thick redwood belly.
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Tim Baker
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1:58 AM - May 06, 2018 #23

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sleek
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2:24 AM - May 06, 2018 #24

Have you bent that bow yet? Im eager to see its results.
Once I was making some paleo mulch from a stick and after many hours was astonished to find myself holding a bow.
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Tim Baker
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8:08 AM - May 06, 2018 #25

Sleek:

" Have you bent that bow yet? I'm eager to see its results."
 
I've got to sinew it first.
 
Here's some stats:
54" long
1 3/16" wide a widest.
1/4" at the nocks
4 3/8-oz before adding the glue belly.
5 1/2-oz after -- 1-1/8-oz of dried glue on the belly, about 1/4th the weight of the bare bow.
I'll apply the same 1-1/8-oz mass of sinew on the back. With the glue in the sinew the finish bow should be at about 7-oz.
 
As the glue dried it pulled itself into a bit of deflex. The bow will be pulled into several inches of reflex when applying the sinew, putting the glue belly into strong tension, a big compression safety head start when drawn.
 
This might be a totally dumb idea, the glue belly failing in compression, but maybe not. Way cool if it doesn't
 
The bow pulled into deflex by the glue.
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sleek
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2:25 PM - May 06, 2018 #26

Im worried the glue may crack while being pulled into reflex. If so, perhaps scrape off the belly and apply it with the bow in reflex.

Of coirse im also worried aboit the glue cracking under compression, and think you will need fibers mixed into the glue to give it strength. But this is a very good test without all the variables im adding in. It will provide a very good starting point.
Once I was making some paleo mulch from a stick and after many hours was astonished to find myself holding a bow.
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Tim Baker
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9:11 PM - May 06, 2018 #27

sleek:

Quality hide glue can stretch up to 8%. It tried to shrink 15% as it dried, managing to pull the bow into small deflex. So possibly it's used up a touch less that 1% of its 8%, 7% more to go. Reflexing the bow to full reverse draw length of, say, 23", should  only stretch it another 1% or a touch less. I just relexed it 7"  with no problems. Will likely wait for the next test model before going for greater reflex. So if it's elasticity in compression is even half of that in tension then this version will be home free. The one weak link in the chain is the slightly irregular thickness of the brushed-on glue belly thickness. But even if it blows  much will be learned.
 
Hide glue saturated paper towel, revealing that unlike sinew's 4%, hide glue shrinks about 15%
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blancoh0
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5:34 PM - May 07, 2018 #28

Tim Baker wrote: Here's a piece of the mentioned hide glue foam:
Looks just like the foam glue called "Gorilla Glue ". When I use it it has to be moistened on both surfaces. When it set it foams up like your picture. I have not tried it on bows yet. For woodworking though it is messy and foams out of joints that later have to be trimmed down. Not my favorite glue right now.
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blancoh0
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5:41 PM - May 07, 2018 #29

Tim Baker wrote: Sleek:

" Have you bent that bow yet? I'm eager to see its results."
 
I've got to sinew it first.
 
Here's some stats:
54" long
1 3/16" wide a widest.
1/4" at the nocks
4 3/8-oz before adding the glue belly.
5 1/2-oz after -- 1-1/8-oz of dried glue on the belly, about 1/4th the weight of the bare bow.
I'll apply the same 1-1/8-oz mass of sinew on the back. With the glue in the sinew the finish bow should be at about 7-oz.
 
As the glue dried it pulled itself into a bit of deflex. The bow will be pulled into several inches of reflex when applying the sinew, putting the glue belly into strong tension, a big compression safety head start when drawn.
 
This might be a totally dumb idea, the glue belly failing in compression, but maybe not. Way cool if it doesn't
 
The bow pulled into deflex by the glue.
         from blancoh0:    "All this gluing and testing and measuring ! I wonder if this would make the Native bow makers crazy ? I think and guess that they did not do all of this stuff. Not sure who or even when all this sinew stuff started. Same as when fire making was discovered. I am sure different methods were discovered at different times. Flint and steel, friction boarding, bow and spindle,  etc... FYI " 
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Tim Baker
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8:35 PM - May 07, 2018 #30

blancoh0:
 
"All this gluing and testing and measuring ! I wonder if this would make the Native bow makers crazy ? I think and guess that they did not do all of this stuff. Not sure who or even when all this sinew stuff started. "
 
No ancient individual or group had to go crazy testing and measuring. Various bow technologies took thousands of years to slowly evolve, new composite designs, for example, often taking 1000 years between significant developments. But I image if individuals of the past did purposely set themselves to devising new and better designs they did so with the same sense of discovery, adventure and satisfaction felt by those presently doing the same. 
 
 
Anyone playing with making a glue belly, as earlier, especially if using thin fiber to evenly accept greater amounts of glue per coat than if brushed on, try using a squeeze bottle, like mustard and ketchup come in. Such allows rapid but controlled glue placement, and can be kept in the fridge between sessions, with no danger of drying out or rotting as when left outside in open containers. Set in a 'double boiler' a bowl of water, a few moment in the microwave and it's ready to use. 
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sleek
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10:04 PM - May 07, 2018 #31

Tim, why arr you brushing it on? Why not male a long jello mold in the shape if a belly strip, put the glue in, let it jell, then glue the jello belly strip on with wet hide glue. Sitting in a mold will make an even thickness belly lam, and once dry, you can scrape it down to desired thickness.
Once I was making some paleo mulch from a stick and after many hours was astonished to find myself holding a bow.
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Tim Baker
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11:50 PM - May 07, 2018 #32

Brush application was the first test method. Too may coats needed, with drying time between, and a somewhat irregular surface, so now the present almost-all-air fiber matrix for much thicker applications--The above glue bottle helping with that. The mold methods were tried, but it's a nightmare; the glue drying faster and shrinking more in some areas than others, contorting itself into irregular shapes and cross sections, even collapsing the mold as it shrinks. And of course it wants to stick to the mold. Once dry, working it to flat and regular shape is the main nightmare. All in all it's more work than applying actual horn. The idea is still on the shelf, hoping for some way to cause the needed fairly thick depth of liquid glue to dry evenly and level. Reducing the water content to the max would surely be part of it; a large area another, so the center can dry without the quicker or slower-drying edges interfering with the center likely another part. Then a surface which would allow the shrinking glue to slide instead of binding, is needed. All of this is making the brushed-on or fiber/glue-bottle method look pretty good. But maybe better materials and process will come to mind.

Desert for bacteria: This is what happens when thick liquid glue is left to dry. Some sort of antibiotic is needed.
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Tim Baker
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10:07 AM - May 14, 2018 #33

When finished I expect the elevated-sinew bow to have a fat F/D curve and to be very fast. But I've expected the same from earlier experimental designs and been disappointed. Look at the 3-point compound-bow-like F/D curves for these two designs, yet that were miserable performers. Stored energy is only half of the story.
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Fundin
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12:26 PM - May 16, 2018 #34

Man, If I didnt have 4 kids I would run some ideas of my own...
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sleek
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10:32 PM - Jun 25, 2018 #35

Well tim, hows this project going?
Once I was making some paleo mulch from a stick and after many hours was astonished to find myself holding a bow.
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Tim Baker
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10:08 PM - Jun 26, 2018 #36

sleek: 
 
That project is on hold for now while an older one gets overdue attention.
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onemississipp
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12:13 AM - Aug 27, 2018 #37

Tim,
I’m not quite following here.

I understand the use of sinew on the back to gain tension and the use of a solid material on the belly that is great at compression, and that when the sinew back is thick enough that is will result in a neutral line where back and belly meet creating a safe zone.

I would think adding sinew to the belly would only add mass and no benefit as tension is its game.

On a side note Ed Scott mentioned using 4oz of sinew on the back of his bows but I do not remember which type of bow he was speaking of at the time. It’s in his interview on YouTube.


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