My horn bow build-a-long

[DC]

Yeah, they use strange methods to arrive at final tiller so because of that I'm not sure how this would be solved. They use heat to adjust the kasan(the stiffer outer limb) but they use scraping, not heat, to adjust the working limb. Hope I've got that right.

[DC]

I didn't get the sinew nicely wrapped around the edge of the bow. How soon can I add more? Right away or do I have to wait until it's somewhat dry?

[DC]

It was getting worse as the sinew dried, I guess. So I modified the rack I sinewed it on to hold it a bit better. I don't know if I'm doing the right thing but I feel i have to do something. I might fiddle with it a bit more.

[sleek]

It sucks, but it's not too late to pull the sinew off and redo it. The time it takes to build it right is small in comparison to the time you will enjoy a week crafted bow, even smaller compared to how long you will wish you had just redone it.

[sleek]

You could wrap it in clear plas9to stop the drying process until you figure what to do.

[DC]

I think I'm alright. At least enough to not tear it apart. This one is just a learning experience although I have to keep telling myself that. It's not the first mistake. What amazed me is the thinness of the wood. There's hardly any in there.

[gorazd]

I would wait two weeks for sinew layer to dry then take measurement down to 0,1mm  and sand the sinew layers -  to equalise on both sides before starting with new layer.

Then next layer.
Try it korean style - put on layers in gelled state - then wet the layer and heat it with hair dryer - to get them in semi liquid state when they are on the bow already . You have more control how much sinew is added on each side.

[DC]

It looks a lot better this morning. I think clamping it to the frame let the sinew settle into the position I wanted rather than just any old place. We got hit with cold(ish) dry air from the interior so the shop, once it's heated, is 25-30%RH. It was 50°f and 35%RH in there this morning. I'll boil a kettle or two in there to moisten it up a bit but that doesn't last. It is what it is, I guess. It's freezing outside right now so I don't want to put it out there. The sinew is drying amazingly fast but I'll still wait a few weeks before I do the next layer.

[MattZA]

That's looking really great, DC!

Amazing how clamping it to the form like that has just convinced the sinew to do as it's told. It really is like a living backing.

[bownarra]

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?

No they need to be the same it won't balance out when you draw it.

[bownarra]

Don't bother trying to alter the shape now. Heat/tillering will take care of it later. It may actually be counter productive trying to force it into a different shape.
This is why it is worth bending the bow backwards before sinewing but don't stress it isn't bad. I've had worse and corrected it later.
Just because the sinew looks dry only means the surface is dry The bonds take time to form.
You should separate the sinew bundles further and weigh each bundle to 0.1g accuracy. My bundle weights vary between 0.5g and 2g. Slightly more sinew on one side of the limb will cause twist that is very difficult to cure later.

[DC]

It's pretty much settled into it's shape now. It doesn't move when I take it off the form so that's done whether it's good or bad. I will reverse tiller the next one. I was a little hesitant this time but now i have a better idea of what to look for. I realise the sinew isn't dry, I was just surprised how fast it went from gelled to "hard to press with a fingernail" stage. I weighed it right after sinewing and it was 372 grams. This morning it's 312.

You should separate the sinew bundles further and weigh each bundle to 0.1g accuracy. My bundle weights vary between 0.5g and 2g. Slightly more sinew on one side of the limb will cause twist that is very difficult to cure later.

I did weigh my bundles to .1g so I'm OK there. I wish I'd known about bundle weight being .5 to 2 gram. That would have been a big help. I think my bundles were 6.5.

[bownarra]

Yes I like to use small bundles to begin with and get the finished shape with them and then use the full width bundles for the last layers.
The bigger bundles are much easier to handle when you use the Korean method like Gorazd mentioned.

[DC]

Second layer of sinew today. Sorry no pictures. Pretty much the same as the first layer except I don't feel as good about this one. Not sure why. A gut thing. See how it looks in a day or so.

[DC]

I'm new to sinewing so I'm not sure what to expect. I'm surprised how crummy the sinew can look when you apply it and the next day it can look quite nice. That's the case with this layer. I'm quite happy with it this morning. The light spots on the pictures are still wet so it should get better still. The fourth picture is an older one to show how much reflex it's gained. It weighed 440grams right after sinewing and it's 404 this morning. I measured the thickness of the first layer before I put on this one and it was in the 2-3mm range so this one may be the last one. I would like to put on a thin smoothing layer after I sand/ rasp this one a bit. Brings up a question, how much sinew can you remove? I can imagine that rasping  the layers cuts the sinew a shortens the fibers. Is this a problem? How much can I shape the sinew? I'm thinking I should level/even out the sinew before I start tillering so the thickness taper is OK. Kind of using the rasp to fix up my less than perfect sinewing.

PS Found the answer in Adams book. After 3 months I can shape the sinew.