Main Discussion Area > Horn Bows
My horn bow build-a-long
Russ:
how many strips of glue will you be gluing on?
DC:
If you mean horn, one on each limb. The horn forms the belly.
bownarra:
That horn may stay stuck but you really should make the pressure strip that Adam shows. You only need a strip of material and some scraps of pine. You also need a clamp every 2 inches max.
When the horn is heated correctly just prior to gluing eg. 45 - 50 deg Celsius it becomes too soft to be clamped correctly when using just a clamp. You have a lot of pressure in one spot and little (because the horn is soft) between the clamps. That is the reason they used the rope method in the past. Perfect pressure everywhere, it is also very quick when you are practised at it. Even clamping pressure is very important.
The good news is that partial delams are fixable but of course they are best avoided in the first place.
I wouldn't use a greater concentration than 30% glue.
The way to get the grooves perfect is to use a scalpel for the initial straight cut. Then a slightly thicker blade. Then use a very sharp scraper with a narrow projecting foot. Once you have done a couple it is pretty easy. The other methods are ok but not as good as the method Adam describes. The 'best' modern way is to get a router cutter made with 2mm equilateral triangles, make a sled for your horn and one for the core...... = perfection :) but not exactly traditional!
DC:
The clamps are spaced right. At least I got something right. I'll make up a pressure strip for the next one.Is your 30% glue quite runny? I watched a bunch of videos and their glue always looked thicker than mine but it's pretty hard to see. I tried the method of grooving with the little guide tooth and it didn't work for me. Possibly it was because my grooving tool wasn't sharp enough. I never had any trouble with grooving the horn or the really dense wood that I practised on but as soon as I tried to do the Maple it would climb out of the grooves. Once it's crossed over it's really hard to get them straight again. I found that just knocking the points off with a stone so that each tooth ended in a sort of chisel shape(very small) it helped a lot. Now that I have the cutter working better I'll go back and try the guide tooth thing again. It seemed like a lot more user friendly method than the guide rail. Have you had a router cutter made? Was it expensive? Thanks for the input. Much appreciated.
DC:
Oh, when I was sizing the horn and core using 10% glue little bit of fiber or whatever would make small lumps and nibs in the sized surface. I dusted thoroughly before sizing and cleaned it with a small wire brush. Do these normally soften and squash down when you glue? I took a quick, very light pass with the groove cutter just to clean them up before I glued. Just wondering if it was necessary.
PS I found a place that custom makes router bits I'll contact them tomorrow.
PPS How long should I leave this clamped up?
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