Main Discussion Area > Horn Bows
hornbow project numpty questions
stuckinthemud:
Any tips on getting the horn plate perfectly true?
mikekeswick:
I always grind away material to get a straight, untwisted strip. You need to stop regularly to give it a good eyeballing for straightness. It is tempting to follow any minor twist to get a longer/wider strip and heat to straighten but unfortunately the twist will come back and lead to a twisted bow.
Again as heat is used for a large part of the tillering this heat will lead to any earlier heat corrections going back to their original twisted shape. Indeed this can happen when the horn is heated for the gluing process. You need to get it to 50 degs Celsius.
These sort of issues show why every step has to be perfect or else the house of cards starts getting unstable!
stuckinthemud:
Yup, this learning curve is huge!
This is where I am, the heat correction was for the curve of the horn rather than twist, still not totally straight though. The photo is deceptive, there isn't any twist as such, should I cut to size then finish grinding? The bottom piece is 40mm wide, the top one is slightly narrower but is a 1/2" longer at the tip end
mikekeswick:
They look pretty good.
I would continue removing horn on this side to remove the concavity totally first. Then start working on the other side to get it completely flat and thicknessed. Then once it is perfect in thickness remove any extra width down to the size you want.
Remember that extra width is no problem. it is actually very useful to have extra width during the glue-up to the core. Once the horn is glued to the core and dry you can then reduce the core/horn for sinewing.
stuckinthemud:
Thanks Mike, will do. Going back to the hollow limb section. If the olden-days buyers hollowed their horn plates, in addition to getting greater length from a given horn, might there also be a mechanical advantage to using this form - flexing tubes is much more difficult than flat plates, so you might get a stiffer/quicker bow.
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