Tillering horn bow?

[lauderw55]

Hi I am new to horn bows and was interested in making my first one but have a few questions. I have made self bows and wooden bows and know how to tiller those but not real sure how to tiller horn bows. Everywhere I look (Internet/traditional bowyers bible) it says it is done by heat and pressure and not by removing the horn on the belly. So I guess my question is is there a more detailed description on how to tiller the horn now? Or there any videos on the Internet that show this process? Any info would be appreciated thanks!

[loon]

From what I've read online: sometimes you do have to scrape horn in the belly to help tiller it, or to balance it. An even tiller isn't as necessary with horn bows because it can take a lot more stress than wood.

[ChristopherHwll]

It depends on the construction of the horn bow itself.  Horn bows are not all alike, so the way they are built determines the number of options one has to tiller.  You can tiller by heat and pressure in order to not remove any material which is usually ideal as the horn is the most work and least available material.  You can add or remove sinew on the back as well, or you can remove horn on the belly. Most horn bows are pre-tillered in some fashion before the main sinew application in order to minimize the final necessary tillering after sinew is added. If this is the case it is useful to add a single layer of sinew in order to protect the back and not risk breaking the bow during this step.  If the bow's core/belly is a uniform thickness or very thin as with Korean horn bows then you want to try not to remove from the belly at all.  If you are building a solid horn (no wood core) and sinew bow then it is possible to use all three methods of tillering to your liking.  I would say choose a style that you would like to build and that should help you with what options you have.

[lauderw55]

Ok thanks for the help. But when you say heat and pressure are u mean you just hear it up and bend it the way you want?

[ChristopherHwll]

Yes but go slow and do not try to get all of it at once.  Too much heat can cook the glue and sinew weakening it. Only just enough heat to help it along is needed.  Most horn bows are "worked" up to their draw lengths with numerous small increasing pulls.  Some of the middle eastern bows use forms for their limbs to be bent over while stringing.  If you pre-tiller your limbs, before you evenly sinew back, you should already be close to an even tiller.  So the amount of heating would be minimal.  Heat tillering is uniquely different for every horn bow but that is the basic idea. 

[lauderw55]

Sorry if I am asking dumb questions I am just new to horn bow making. So when you say tiller it before the sinew is applied. Basically are u just pulling the horn/core on tillering setup and using heat to correct the tiller that way.

[ChristopherHwll]

No need to be sorry.  I've never learned anything without asking questions so ask away!    Yes but to all only you want to reduce the horn by material removal before sinew backing.  So everything you just said only not by heating but by scraping.. Just like a wood bow. The heating is usually for after sinew backing. Once the sinew cures, start pulling the bow  on your tillering setup.  At that point it will be close to tiller so a little heating of the stiffer limb will relax it to match the less stiff limb. Then you should be done tillering.
If it is a horn and sinew only bow (no wooden core) I would recommend scraping horn from the back of the bow not the belly like wood bows. The back will get sinew so establish a perfectly flat belly early on and then tiller by scraping the back. Be careful and don't pull to much on the unbacked horn.  I've had them break.  You can get it close this way and then lay a single layer of sinew on the back. Let it cure.  Then tiller more, about 2/3 the final draw length.  If it looks good add the rest of your sinew, cure, and then if needed even the tiller with heat.

[Tc]

Very often the limbs bend differently during pre-tillering, and this is due to the different stiffness of the horn stripes (Assuming that the horn stripes and the core have the same thickness on both limbs). At this point it is better to scrap from the wooden core (if there is) and not from the horn. Leave the horn for the final tillering.

[loefflerchuck]

Anyone who wants to make a hornbow should have Adam Karpowicz book. Almost all your answers are there.

A perfect tiller is for a bows performance and long life, so I think it's important. Heat in the early tillering. Then once it is uniform, scrape or sand till the tiller is perfect.

[Tc]

Pre-tiller is done when horn is glued and the core is shaped (no sinew). I do not know "early" tiller, probably you mean the opening procedure when you use the asa gezi. Yes, this time heat is used to maintain symmetry.