Main Discussion Area > Horn Bows
My horn bow build-a-long
DC:
I'm curious about something. You put on 5 or so coats of thin glue letting it dry between coats. Are you then depending on the thick wet coat to reactivate the dry coats? It just seems like a bit of redundancy. Why not put on a sizing coat and let it gel then immediately put on the thick wet coat. Wouldn't that accomplish the same thing without the waiting and maybe even better because you don't have to hope that all five layers get reactivated. I know this is the way it's done, I'm just wondering why.
DC:
Here's the test bow glued up. I'm going to modify the form to put more angle in the tip kasan bend. I may try to put a little more bend it these with dry heat just to kill a little more time :)
bownarra:
The reasoning behind letting the coats dry is so you cannot get a dry spot in the joint.
Applying glue, letting it gel then applying fresh glue would mean that the first just gelled layer could be removed (or part of it) when fitting the parts together. The dried layers of glue cannot 'come off'. All the layers do not need to be reactivated just the surface. This method of sizing with many coats of thin glue, drying inbetween and then applying the thicker final layer works perfectly.
Collagen glues contract as they dry and therefore wood to wood joints do not need high clamping pressure in fact it is counter productive. The key is close fitting, smooth surfaces to start with. Roughened surfaces trap air bubbles reducing glue saturation of the surface.
I like to test all these things for myself and it doesn't take long to glue up some test pieces. Try scraped smooth surfaces, 60 grit roughened surfaces, no sizing, thin glue, thick glue, clamps no clamps etc and then break them all. All in the name of experimentation and a bit of fun :)
It is well worth experimenting with the horn to core joint before going for the actual glue-up.
Yes you want to increase that angle in the tip bend or else the bow will stack early and not store as much energy as it could.
DC:
I just noticed something(I can be a bit slow at times). With self or backed bows I avoid putting a splice in a bending area of the limb. The grip/sal splice extends well into the bending limb. Is this not an issue when the splice is sandwiched between the sinew and horn?
DC:
Here it is at the end of today. Dry heat wouldn't cut it so I steamed the tip/sal bend to look much like I hope it will. There is a little reflex bend just at the end of the sal/grip splice on the left side. I'll have to watch for that kind of thing on the real one. No twist in this one. the centerline is nice and straight. Does this look more like what I should be trying for?
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