My horn bow build-a-long

[bownarra]

If you are close to using your allotted amount of sinew then make sure to reflex it more after the last layer is added. The tips should be close to touching. This also helps with stopping delamination between the sinew layers.
The trick with sinewing is to try and establish the shape you want after the first layer then you only have fine adjustments to make on subsequent layers.

[stuckinthemud]

Thanks for posting this thread, I've been saving it up to read in one go, my build stopped when I could not get perfect core wood, changed jobs, life got hectic, blah, blah, blah.  I have a copy of The Book and I have read it many times and still struggle with lots of information I need as a novice that is missing - the earlier explanation of glue percentages, for instance, finally answered a question I have been unable to get my head around since I first read The Book three or four years ago.  Anyway, this thread is really inspirational and very, very useful, so many thanks.
Andrew

[bownarra]

Once you have read the book AND made a few bows you will realize that ALL the info you need (and more) is there. You may not realize it but it is there
Practical experience trumps all when it comes to learning the intricacies. You simply need to roll the sleeves up and have a go to start the real journey

[stuckinthemud]

I agree that the information and more is there and find the book excellent in almost every way, I have unreservedly recommended it and even managed to print off a hard copy, but, it is not without its frustrations, and that is where threads like this come in, coming back to the glue issue, for instance, I mix glue from powder, so, 30% is a bit tricky to understand, is that by weight, by volume or by made and dried glue? Is made and dried glue always the same strength? So, when the solution (sorry couldn't resist that pun) pops up in a thread like this it just fills in the holes that the writer assumed we all know.

[DC]

When I made a 35% glue I used 35 grams of dried glue and 65 grams of water. I'm thinking that within 5-10% is close enough. As it's sitting in the pot the water is evaporating and then you add "a bit" of water to thin it out again I'm sure the concentration drifts around that much. Made and dried glue depends on your definition of the word "strength". If you mean "concentration" then dried glue is dried glue. When you make glue the first pour will be a stronger(physical strength) glue than subsequent pours.

[bownarra]

DC has got it
Dried glue is only glue Measuring is done by weight.

[stuckinthemud]

So if I make gellatin glue from powder the weight of the powder is the same as if it were made up and dried out glue sheets

[DC]

Yes with a but. The weight of the "dry" glue will vary with RH so there will be a little difference. Not enough to worry about. You may be more anal than me . The only reason I mentioned it is that I went on a search for this and wound up on some luthiers sites. These guys define anal. I just didn't want to give you my opinion and have you find a luthiers site that made me look like a liar.

[DC]

How long can I leave the sinew between layers? I've cut the tip of my index finger fairly badly carving a 1/4" long eagle for my grandsons model railroad. Adam says two weeks max between layers and then says in the curing section that if, after 3 months,if it's not thick enough to add another layer. I think there is enough sinew on it now but it's close and I'm not sure how much more it's going to shrink. It's 361 grams at the moment. It was 440 right after the last layer.

[stuckinthemud]

Isnt there a recommended thickness?  I think the recommendation for a top-up after a few months is only in case the sinew shrinks to below the required thickness after it has cured.  If you've got the right amount on there then you probably shouldnt add any more,  I'd leave it cure and once its all done you'll accurately know what to add or even sand away

[DC]

There's just one spot in the eye that's iffy and I really think it will be OK. It's almost 4mm thick there and I'm kinda going for 3mm. I just don't know how much more it's going to shrink.

[bownarra]

It won't 'shrink' much more. Just the bonds getting stronger with time now.

[DC]

OK it's officially curing now. Nothing for at least a few months so all there will be on here is some random questions about hornbows. For example.

When I do get to close to tillering do I reduce the sinew to get the thickness taper even on both limbs first? I ask this because in the book Adam only mentions reducing the horn when tillering. Is there a reason for not reducing the sinew as part of the tillering?

I can make the tepeliks now. It says to make them with the about same radius as the strung bow. How do I guess at this radius?

[bownarra]

You can sand the sinew lightly to flatten it but anything more is not advisable. You want long untouched sinew fibers on that outer layer covering the whole sal and kasan eye area. Fill in any voids rather than sanding down to remove them.
Reduce the horn to get a perfect taper before bending.
Good question with the teplics To be honest I don't use them anymore. I prefer to open the bow with the notched stick(name?) initially. to check for twist balance, bend etc. Then once it looks good I use a pegboard to get to brace. For the heavier bows that are too strong for the pegboard I made a bow press with a boat winch to do the pulling haha. Stringing your first hornbows for the first time is quite a heartrate raiser....
The pegboard is made from glued up ply at 2 inch thick. The posts are high density plastic rod 1 inch diameter, with soft leather wrapped around. A 4 inch section of ply to act as a saddle for the handle. Multiple holes drilled so the bow can be bent progressively.

[DC]

You can sand the sinew lightly to flatten it but anything more is not advisable. You want long untouched sinew fibers on that outer layer covering the whole sal and kasan eye area. Fill in any voids rather than sanding down to remove them.
Reduce the horn to get a perfect taper before bending.

OK, might be a problem here. I know the sinew is thicker on one limb than the other. I'm not sure by how much, can't remember right now. Should I reduce the sinew to an even thickness(a little thinner than finished) and apply a final continuous layer? Probably use the Korean method.