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hornbow project numpty questions

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stuckinthemud:
Ok, so, when processing horn, you need a strip of horn about 6mm thick, is that measured from the top of the crown, or the edge?. Also, do you run the thicknessing cut right to the end of the horn or do you cut off the tip and save it for other projects? Do you cut a few mm oversize and use abrasives to get to the final thickness?  Finally, some sources advocate a sacrificial jig to mount the horn on before band sawing but is it ok to just use the saw fence? Thanks, Andrew

Pat B:
Just guessing...I think you want the horn "lam" to be even thickness through out when you cut it from the raw horn then grind it to it's glue up shape and size.

stuckinthemud:
Hi Pat, yup, I have back strips to process, each one going from 2mm thickness at the wide end, to full thickness about 6" from the tip. I think I'm supposed to make a second cut?

mikekeswick:
Hot melt glue and a piece of ply are what to use to keep the cut true. Do not use the fence. A 3/8th blade about 10 tpi with a good set to it is what you want and free hand the cut.
Try to envison on what plane the longest, widest, straight strip is.
A horn strip does not need to be 6mm thick. 6mm thick horn would be suitable for a bow of around 100# If you are aiming for something around 50# I wouldn't go any thicker than 4mm. You want to have the core as thick as possible as wood is the most stable and stiff material in a composite. Sinew thickness is more or less set at 2 - 3mm over the center of bending sections so you can really only alter the core to horn ratio. More horn will have less string follow but will be harder to stabalise. Typical core woods will be around 0.65s.g. horn is more like 1.3 s.g.
It is best to cut all the way to the tip, even though it narrows too much to be in the finished bow, it is useful for clamping later when flattening and prepping the strips for grooving.
Yes cut oversize on the bandsaw. Then use, rasps, files then 40 grit to get perfectly flat. At this point you will see that you will have a tapered strip anyway. Once you have it perfectly flat use a very sharp scraper to get them completely smooth. At this point you should not touch the strips with bare hands(important!).Then groove.

stuckinthemud:
Thanks Mike, that's exactly what I need to know. Target weight is between 40 and 50 for my first one as I  shoot 45# max at the moment. Probably look for 70 from the second one but that's a way off yet.

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