My horn bow build-a-long

[bownarra]

Yes it is the total thickness that determines draw weight not how much there is of each layer. A bow with thicker horn will take a little less set therefore draw weight will be slightly higher but no it is the total thickness that matters.
When Adam mentions adding more sinew I think he means proportionately more sinew rather than adding 'extra' sinew. The 100 grams advise is what to go with here. 100g will probably mean you end up with 2.5 - 3mm sinew over the center of the sal.
I only used around 70g on this particular bow and horn of around 3mm in the main bending section. If I remember right these horns were recovered from an older failed bow hence the limited thickness.
This bow is around 32mm wide in the sal.
I would advise moving the thinnest section out to 35cm even if it is slightly around the bend. If your thinnest spot is at 30cm then the sal will be over strained. Better to have the thinnest spot even out to 37.5cm from the handle to lower the strain a little further.
One of the most important steps of the whole process is making sure the core is perfectly sized. Make sure you do not touch it with bare hands once it is prepared. A lot of hornbows fail because of broken cores where the sinew/wood bond isn't perfect (don't ask me how I know that one….haha).
Heat the whole core and use 5% glue for the first few coats. Very light sanding (240grit) inbetween if any fibers raise. Then you can increase the thickness of glue a little. Make sure it is glossy everywhere.
Good luck

[DC]

I would advise moving the thinnest section out to 35cm even if it is slightly around the bend. If your thinnest spot is at 30cm then the sal will be over strained. Better to have the thinnest spot even out to 37.5cm from the handle to lower the strain a little further.

Thanks for that, I was considering doing that so now I will.

[DC]

First coat of sizing on. I guess I'm on my way

[DC]

A question. Adam says to sinew within a day of sizing to avoid contamination. But then you can leave the first layer for a week or more before you put the second layer on. Am I missing something here?

[bownarra]

No not really
Just do as it says

[bownarra]

I forgot to say. when sinewing the sal I've found it useful if the first sinew you lay is on the edges of the limb. Like you are aiming to make the back flat with this first bit of sinew. Then when you add the further layers it is much easier to maintain the dead flat back.

[DC]

When your limb is only 6-7mm thick there is not much crown I thought I was going to start to see grooves. But yes, I was going to build the edges on the first layer. That's going to happen any time now. I woke up this morning and it -4c (25f) out side. I've got 3 heaters going in the shop to warm it up. Glue pot is on , sinew is soaking and I'm nervous as hell

[gorazd]

I did the sinewing in korean style (seen in youtube).... to shorten the messy procedure and to be sure to put sinew more evenly on each limb. It is pretty fast too. More time was spent on sinew processing. I separated each sinew hair down to single one - using water (to get them soft).
I did it in 3 layers - 1 or 2 week waiting between each layer. One layer was around 1mm, all together 3mm.

[DC]

First layer done. Whew! I marked the thickness of the limb on the belly so I can figure out how much sinew I've applied. I started by soaking the sinew for a half hour or so. I had it all sorted in bundles ahead of time. Then I squeezed the water out and combed the bundles. I had four bundles for each limb. In hind site dividing it further may have been wise. It would have made for easier combing.  After I had all the bundles combed out I sized the bow again with 10% hide glue. Then I soaked a bundle in the glue pot, squeezed the excess(judgement call) and smoothed it on to the bow. I did the same with both limbs and then came back and did the grip.

[DC]

More. Once I got sticking the sinew on my hands were too messy to take more pictures. So from the second picture on they are after pictures.

[DC]

More. The pictures make the sinew look lumpier. I put on about 60 grams of sinew. I wish I'd written it down because now I'm starting to get confused about what I did. I'm pretty sure I did 25 grams on each limb and 10 on the grip. I know I got it even but I'm just not sure how I got there. Stupid old fart. When it dries some the thickness will tell me.

[DC]

And here it is all gelled and reflexed some. The left limb is stiffer, darn. I just looked at the thickness measurements and where it's stiffer it's about .3 of a mm thicker. Thought I was close enough, should have done a test bend. Fussy thing. now i have a month off, maybe.

[Deerhunter21]

are you able to fix that?

[DC]

I don't know whether I can do anything now, maybe someone will chime in. I think there is a little tillering I can do when it's dry. I just read a bit in Adam's book and it sounds like this is normal to have small imbalances once it's dry. Whether or not it should happen at this point is not mentioned.
I'm wondering if I should put a little pressure on the stiff limb now.

[sleek]

Maybe as it's not reflexing as much, it will balance out when drawn. As the thinner limb comes around more just to make brace, the extra energy in the weaker limb may pull the stiffer limb back, continuing all the way to full draw until it's got a balanced full draw profile. I know I have read lots where heat is used to balance the limbs out on occasion as well. You may also get away with laying a little extra sinew on the weaker limb to strengthen it?