My horn bow build-a-long

[Deerhunter21]

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?

[gorazd]

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.


I did the same to clean the grooves ...
I used heat gun (gently) to speed up the drying of the sizing coats....



PS  I found a place that custom makes router bits I'll contact them tomorrow.

PPS How long should I leave this clamped up?

[DC]

Thanks for the post gorazd.

Here's a pic of my clamping belt. 2"x 1 1/2" plywood glued to seatbelt material with Shoe Goo. Handy stuff

[bownarra]

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.

If you make the glue thicker you will have less time before it gels. The sizing coats eliminate the chance of there not being 'enough' glue in there once it is dry.
The way to know for sure with your glue is to start with dried, hard glue. Weigh the amount you intend to use. Say you have 30 grams of glue add 70 grams of water to make up a 30% glue.
Yes you can use a new, sharp triangular file to straighten any wiggles. As vyou say a very sharp scraper is key, that combined with a narrow footing and the scalpel, followed by a slightly wider blade for cutting the groove on core.
No I didn't bother getting a cutter made but have seen it done and know from doing a lot of router work that is would be quite easy to get them absolutely perfectly straight and matching. You just need to make the right sleds to hold horn and core. The fact that it would take about 5 mins once you have the sleds made is quite attractive but not exactly traditional! However at the end of it all matching grooves aren't even necessary! If you use two slightly different scrapers one for the horn one for the core the job doesn't take so long and there is little chance of messing anything up.

[bownarra]

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?

Ideally it should be a perfect even layer everywhere and glossy. If the sizing isn't right it is usually best to wash it off and start again. I like to use very thin glue (5% max) and about 20 -25 coats is usually sufficient. The thinner glue wets the dense surface of the horn better. and naturally dries a bit quicker. The sizing coats shouldn't be dried warm just use patience! It's better to be patient now than have a bow that delaminates later.
The 'bits' might be in the glue? Try straining it. The horn should have no loose bits on it at all. The last pass with the scraper should leave it shiny. Any areas that need a clean up can be sorted out with a scalpel blade with a triangular end used like a scraper.

[bownarra]

Pressure strip looks good

[DC]

Thanks for the posts bownarra. Filtering the glue is a good idea, it's probably gotten a little mungy. It went on real nice and glossy, it just had a few nibs. How long do you let it dry before you unclamp it? I need the clamps for the other side but I may buy some today.

[gorazd]

Thanks for the posts bownarra. Filtering the glue is a good idea, it's probably gotten a little mungy. It went on real nice and glossy, it just had a few nibs. How long do you let it dry before you unclamp it? I need the clamps for the other side but I may buy some today.

I used the rope and waited couple of days ... just to be sure 

[DC]

More questions. in the book Adam says to use very hot glue. Everything I've read says the optimum temperature for hide glue is 140°f. Is that what he means by very hot?

[bownarra]

Yes that is correct. It will start to degrade  once you hit 65 - 70 Celsius. I judge the temperature with my fingers now I have the feel for it. A simple test without a thermomenter is to get a very fine piece of sinew and dip it in the glue. Too hot and it will shrivel up.
I also leave it a couple of days to be sure. I once had a strip with matching grooves misalign when clamping. The first clamps were only on long enough for it to gel.....you wouldn't believe how hard it was to get off even after that short a time. I would think that one day is plenty but....

[DC]

Thanks. One more thing cleared up