Thickness sander.

Double sided carpet tape?

Obviously have to clean off any residue afterwards.

Grooving is needed for the horn.

I think you need to have the outer curve flattened, before you can put the horn stripe trough that machine. Horn is curved, not straight like board...

Intresting looking machine, it is possible that it could be of use for horn bow maker.

Umm double sided carpet tape sounds like a plan. I'll look into that.
jkekoni - yes I know the inner side of the curve needs to be grooved. What I meant was using a belt sander as normal to reduce the outside of the horn, remove the grooves/dips/cracks etc . Then reduce the thickness until they are ready to be steamed straight. Steam them straight and then glue them to a board by the flat outer side (future belly). Once they are stuck to a board I can run them through and reduce to final sal thickness. The beauty of doing it on this machine is that it leaves totally flat and parallel surfaces so there would be no errors at all in the thickness of horn thus eliminating another potential problem (if it is stuck down properly!)
I found the final thicknessing before grooving to be one of the tricky parts of the whole construction. I found that because I hadn't got the thickness of the horn spot on using the belt sander the thinner more flexible areas raised up when the horn was clamped by the ends.

The carpet tape I have used have been a little soft, which would perhaps make the process less exact.

Doesn't it seem like the bellies of the original bows usually are rounded? If aming for a flat belly, the idea is probably good, but I would rather spend the time getting the feel for the dimentions doing it manually. That is needed for the rest of the bow anyways.

Technically it is probably not optimal to have a parallel thickness even throughout the sal. Doesn't Adam suggest a taper of about 1mm?

Looks like a brilliant machine, however :)

I think it will be a waste of time to mechanize production, unless you make many strips at a time. Even then, flattening horn perfectly with heat will be difficult. If it is really not perfect, then the sander will cut through the wave in horn and make it look great, but once the finished strip is heated again for gluing, the horn will relax to the wavy shape, which may be hard to clamp. Plus you will be doing the taper by hand anyway. Making parallel thickness strips first is wasteful, since the horn tapers naturally.

I use an upside down beltsander and start with 36 grit, which goes very fast (even too fast sometimes...). Then switch to 80 for a few passes over the sander before scraping the inside etc. I bet the heating/flattening, sticking to a board, sanding parallel on the machine then tapered by hand will prove to be a longer process than that.

Adam

Yes, flattening horn perfectly cannot be done, or it'll be more complex than making strips.

However if the outer curve is made ok, it may be possible to feed the strip trough to make the inner curve, this depends how the machine works.

I am thinking that one could perhaps use such a machine instead of belt sander, I mean without the thickness setting...

The lower flat wide belt fitted with fine grit paper is a feed belt. This is controlled seperately to the main drum - the drum is what does the actual sanding. I think if you look at the close up pictures on the link page you can see the drum itself. So the workpiece sits on the lower feed belt and is driven past the spinning drum. The height of the drum is finely adjustable thus giving sanding to a certain thickness.
It is possible to cut tapers with it by first making a tapered sled for the workpiece to 'sit on' whilst going past the drum. The taper on the sled is automatically ground in the workpiece. This is what I do to make tapered laminations for English longbows. Once you work out the correct tapers you basically have a finished bow right after glue up.
However I wouldn't be thinking about tapering the horn at all - I don't have anywhere near enough experience with horn bows yet.
I just want to ensure the horn is the same thickness through the sal section. As Adam says the horn is tapered anyway, so where the horn starts its taper eg. where the inner concave section starts will not be sanded anyway. As the horn needs to be steamed to a lesser curve than the core anyway I would simply be doing this step slightly earlier to enable easy gluing to a flat board.
I will be experimenting with it tomorrow maybe and i'll post some pictures to show how it went. Fingers crossed I won't ruin a set of horns!

I have used such a procedure (board and hot melt glue) to fix horn for grooving using a router. It worked nicely.
Before glueing to the board, the horn was made roughly parallel on the belt sander and then more or less thickness sanded using the belt sander. I used a belt sander similar to this one: http://p.gzhls.at/311268.jpg
For improvised thickness sanding, a frame with a horizontal rod is mounted in front of the sander, leaving a gap of the desired horn thickness. The horn is held vertically and moved through the gap until it is evenly sanded to the desired thickness. On my belt sander, this requires several runs because the roll that transports the sanding belt is supported by a spring, which will give in somewhat. Because of the small contact area between the sanding belt on the apex of the roll and the rod, this can be done on a curved horn. The outer side of the horn is sanded.
With this luxury thickness sander of yours, I would probably heat the horn in the oven before clamping it flat on a board. Would be nice to have one!

Daniel