The guys that build self bows and board bows understand the meaning of the word/words “Tiller” much better than most guys using glass or carbon backing.
Glass limbs are typically laid up with identical pairs of laminations coming out of the same form on a TD bow, or out of a one piece form that has matching limb shapes. The Tiller on the bow , or how and where the limbs bend is pretty much pre determined with the lay up and altered from one bow to the next with wedges, taper rates, and width profile. Of course the the “tiller measurements” from the fades to the string can be adjusted with profile width and sanding glass.
But…. What a lot of guys overlook is how closely the limbs match during the draw cycle….. you can have a bow at dead even tiller measurements that exhibits a buzz or slight vibration that brace height adjustment doesn’t eliminate…. This is where mapping your limbs comes into play.
Tiller adjustments can be made on glass limbs by sanding glass and adjusting the width profile in different portions of the limb a wee bit. Most commonly the width adjustment is done on the belly side by trapping the limbs, so it does not noticeably change the over all width profile.
Some of these fine tuning adjustments are very difficult to see with the naked eye alone on the tiller tree. The use of a short tiller block along the belly side of the limbs is used, and even then, the amount of change will be very small. It’s mostly done by feel at that point….
Once you adjust it and the buzz turns to a dull thud…. You may find your actual “tiller measurements”are off by as much as 1/8”-1/4” top and bottom and can go positive or negative. But…..the bow is “Tillered” properly, even though the tiller measurements are different….
A lot of guys out there just never bother do any fine tuning. Bring her in to even tiller, and call it good. You’ll get some good ones and some bad ones…
I know a lot of you bowyers already know this, but I thought I’d provide this info for guys that don’t……. Kirk