"Perfect Tiller"

[DC]

Let's say I make a recurved bow and tiller it "perfectly". Then I cut it in half and splice it back together with some deflex and then heat in some reflex. Will the tiller still be "perfect" or does tiller requirement depend on side profile?

[Badger]

  I think just using tiller logic would answer your question. The thickness determines how far something can bend before it takes set. The width determines how much it will bend with X amount of force applied to it. Another bit of tiller logic, the entire limb corresponds to it's particular angle with the string at any given moment. So if you have a limb with curves in it the parts of the limb that have the highest string angle will feel the effects of force more than parts of the limb with lower string angles. You can apply that any way you choose.

[bradsmith2010]

so many variables, it will need some adjustment,,

[DC]

I was thinking about thickness taper when I wondered about this. Shouldn't the thickness taper stay constant even though the limb is starting out at a different spot?

   the entire limb corresponds to it's particular angle with the string at any given moment. So if you have a limb with curves in it the parts of the limb that have the highest string angle will feel the effects of force more than parts of the limb with lower string angles.

Didn't we decide in the "parts of the limb bending first or last" threads that the whole limb bends at once. I can't see how one portion of the limb would feel the force more than another.

[druid]

DC, how much reflex (to what point) and in what place of the limb?

[DC]

It's theoretical but I usually reflex the whole limb, increasing the curve as I go out so it kind of blends into the recurve.

[Badger]

I wasn't talking about the timing of the bend. Think of it this way, your braced profile shows reflex in the mid to out limb, it is point upward at that point and has a lower angle to the string. You weaken that area a little to get it bending and suddenly it is bending too much because the string angle increased and it is feeling more leverage on itself.

[DC]

I wasn't talking about the timing of the bend. Think of it this way, your braced profile shows reflex in the mid to out limb, it is point upward at that point and has a lower angle to the string. You weaken that area a little to get it bending and suddenly it is bending too much because the string angle increased and it is feeling more leverage on itself.

OK gotcha but back to the original question, if it bent nicely when it was straight shouldn't it still bend nicely? I'm talking about deflexing and reflexing the limb with out any scraping or tillering of any kind. Just taking a well tillered bow and changing the side profile. The draw weight will change probably, depending on how much deflex and/or reflex.

[Selfbowman]

I think I understand DC what you want. It’s easier to perfect tiller a straight bow vs recurve. It’s a pain for me to understand where to watch and when to watch for limb bending during tiler. I haven’t done many recurves though. I also think there are to many variables to take a perfect tiller straight bow and change it to a recurve with out re tillering. If I am understanding your thoughts. Arvin

[bradsmith2010]

if it was fiberglass maybe

[DC]

I think I understand DC what you want. It’s easier to perfect tiller a straight bow vs recurve. It’s a pain for me to understand where to watch and when to watch for limb bending during tiler. I haven’t done many recurves though. I also think there are to many variables to take a perfect tiller straight bow and change it to a recurve with out re tillering. If I am understanding your thoughts. Arvin

Yeah, that's it, almost. Take a straight bow and turn it into a R/D.

[Allyn T]

Maybe if the top 1/3 didn't work on the straight bow at all then the non working part would be the recurve and everything else would work fine?

[sleek]

Yes it will change drastically. As you deflex, you decrease your leverage at the tips, reducing strain in the outer limbs, forcing the inner limbs to take more strain than the outer. Deflex limbs require thicker limbs to counter this. Actually, ANY and ALL deflexed portions of a limb will REQUIRE the deflex to be thicker or it will hinge due to increase leverage over that area. This is why deflex bows, in my experience, are more efficient than reflexed bows, even if slower. They store less energy due to lower string tension, but that energy is more efficiently used because the thicker inner limbs are less likely to take set, combined with the reduced radius they bend to store a set amount of energy.

[bownarra]

No.

[DC]

Maybe if the top 1/3 didn't work on the straight bow at all then the non working part would be the recurve and everything else would work fine?

In a lot of cases people leave the outer 8-9" stiff which is just about how much it takes to bend a recurve so it seems like it would be OK