My horn bow build-a-long

[DC]

I thought I would bring Bownarra's measurements back here

"Here are the measurements from my 40ish# bow. 121cm.
Center - 33mm
5cm  - 26mm
10cm - 14mm
15cm  - 10.4mm
20cm - 9.6mm
25cm - 9.1mm
30cm - 8.9mm
Kasan eye 35cm - 9.5mm
40cm - 12mm
45cm - 13.5mm
50cm - 14.5mm
Base of tip 52cm - 17mm"

I'm a little thick(that's well known)at the 15 and 20 cm marks so that kind of goes with J's comment. I'm just not confident that I have enough horn. Maybe I can take a bit of horn and a bit of sinew? I heated the eye on the right limb and took a little reflex out. We'll see if it holds. It looked better to my eye. I'm not doing much, still got the crud.   

[JNystrom]

Well, its not an easy task to make a hornbow. I've broken plenty .

In case you run out of horn in sal section, basically the only effective thing to do is to add sinew to the outer limbs. Then while drying, make an effort to reflex the outer limbs as much as you can.
Other choices are to deflex bending parts or narrow them. But those doesn't really add much.

I think you have good chance of adding 2mm more sinew (as a kasan ridge). Do it in two rounds and roughen the existing sinew back properly.
Some old bows actually had even a 4-5mm thickness of sinew in the kasan ridge. Adam K. writes in his book that if you run into this kind of tillering problem or bow coming under weight, under sinewed or such, adding sinew layer after long curing is still viable option.
After this extra layer, i wouldn't wait more than 2 weeks to continue tillering.

If you can take of sinew from sal sections, after that you would need to put a full layer of sinew on top of sal, to bind everything together. But that is a viable option too. Actually, you might be best of by using both, taking of sinew from sal (if there is too much in the first place!) and adding sinew to kasan.

[DC]

If I add more sinew the DW will go up, right? If it goes over 40# it's just a wall hanging for me, I can't pull it.

" Here is some measurements of some of my bows, a typical turkish: limb next to handle 13mm thick, mid sal (most bending part) 12,2mm, kasan eye 11,7mm and from there quite fast growing to  kasan 15mm. "

What is the DW of this bow?

[DC]

Is a tillering tree ever used?

[JNystrom]

As i described, you can take of sinew from sal and add to kasan. Cause now the balance is wrong. Just an idea. This wont raise the draw weight, but balance the bending.
If you already have only the minimum 2mm of sinew in sal, then the problem is your core. Its hard to go and tiller your core at this point.

I gave those measurements as a example of proportions, that bow should be about 90-100 pounds when tillered.

Tiller tree is used when you get to brace the bow and have it straight, so it wont unstring itself.

[DC]

When I was bending it to measure the string the crack in the horn extended itself about 2". The part that I had previously CA'ed is still fine. The crack continued straight down the bow so I CA'ed the new part. But,,, right where the new section of crack is the limb now has a sideways dogleg that I'm pretty sure wasn't there before. I've been watching for twist because I was proud of myself for not having any. This doesn't look like twist, it looks like a sideways bend. But I guess it could be twisting. I'm trying to get rid of it by heating the eye.

[DC]

I got the twist/ sideways bend corrected with heat so I tried to brace it this morning. The left limb went into full bend and the right limb went into full reflex, so it was "S" shaped. The rubber band would have held it I think but it was such a delicate balancing act. If I straightened the left limb by squeezing the limb and the string it would pop through and the right limb would go full bend and the left would go into reflex. This is obviously not right. Maybe not enough brace height? I didn't have enough hands to measure it while I was playing with it but I took notice of where it was and it was about 8". That's in the ballpark according to Adam. It's like each limb is ready to oil can and any push will send it one way or the other. I'm pretty sure the left is the weakest. I was planning on resinewing but now this is happening. Not sure if I want to mess with it until I get an idea of why it's flopping back and forth.

[JNystrom]

If you cant stop the excessive bend by hand, its quite apparent that the tiller is off then. You shouldn't run into this kind of problem if you let it be freely on the peg board and it stays balanced. Is your peg board 100% symmetrical?
Try to have the pegs as far on the tips as possible to mimic being braced with the bowstring.

[DC]

Peg board is symmetrical. It doesn't do it on the pegboard. The pegs are right in the tip bend and I think there is enough friction to stop it. It happens as soon as put the tension on the string and remove a peg. I've been looking at videos of people shooting hornbows and to me it looks like all/most of the bend occurs in the inner portion of the sal. The outer part of the limb never seems to go past straight. Mine does(this goes back to your earlier comments) and that gives the limbs the opportunity to "oil can". Mine is bending more like a conventional bow. I've been looking for progressive pictures of drawing a hornbow but haven't found any yet. I think if I stiffen the outer sal/ inner kasan eye area I think it would solve the problem but that would entail putting thickness where no one seems to put thickness. The only thing I can think of is that the combination of leverage and thickness make the inner part of the sal weaker but still thicker so the limb still has taper along it's length.

PS I just looked at a picture in Adams book and it looks like the whole sal bends evenly right out to the kasan eye which doesn't quite straighten out at FD. Now I'm thinking that when I made this I wasn't really sure where the eye was. I put reflex in the sal rather than the eye. So now the eye is bending too much. I'm stripping out the last of my long sinew so I'd better get this right.

[DC]

OK here's the new kasan ridges. The dark line is shadow. It's a nice smooth blend.

[DC]

After about 3 months, while the bow still dries, it can be worked further to shape the sinew. It is done first with a file to flatten the back, or, if a flight bow to give it a slightly rounded shape. The edges are also made round, but still overlapping the belly (see the chapter on cross-sections). Sinew is also shaped on the kasan section and the excess is removed from the tips. Then the bow is sanded again to eliminate the file marks and checked with a caliper to make sure the thickness of sinew was sufficient.

Karpowicz, Adam. Ottoman Turkish bows, manufacture and design: second edition . Adam Karpowicz. Kindle Edition.

If I can do all this to make the sinew smooth why can't I scrape a bit for tillering?

[JNystrom]

Basically you want to keep the sinew fibers intact. What ever you choose to do, just keep this in mind. Small scraping such as just making the back even and flat is minor. I wouldn't personally go tillering from the sinew back.

If the bow ends up too heavy you can always equilibriate it in 60% rh or so and then heat off the reflex. I think you tried this but the moisture content of the bow makes a big difference.

I think Adam has in his book bows half drawn. Basically the kasan doesn't bend at all.

[DC]

Filed down the fade quite a bit and took a layer off out to the kasan. Then I put a new thinner layer of sinew where I had filed. Now wait a few weeks,,,, again

[bownarra]

sorry I haven@t checked in for a while!
yOU MUST NOT LET THE BOW 'FLIP FLOP' oops caps lock on haha
As I said it will be 'alive' when you first string it. You should have everything to hand eg. the inner tube pieces. A piece of cord works too.
It is doing this because it is a light bow. Simple as that. Heavy bows are much,much easier to tiller. To reduce the tendancy to do this you should let it sit on the pegboard for a few days (only once it looks nigh on perfect). The light weight bows need a lot of time to settle to the string. A light weight bow I tillered for someone else took a week being strung before it settled down. Its bending sections were far too long. Don't make any judgements about limb strength relative to one another until you are 100% certain. If you make even small mistakes with material removal you will be chasing your tail.
DO NOT tiller from the sinew back - a light flattening is ALL you should do to the back. The same rules apply as on a wooden bow. These bows are also way more strained. I seriously would not want a hornbows back to fail when I had it drawn......

[DC]

It is doing this because it is a light bow.

Do you think you could explain that somehow, it makes no sense to me. To me that's like saying a rat trap will work and a mouse trap won't. Exactly the same design but the rat trap has more tension.

So to me. Not "as simple as that"