Correct tiller shape

[bradsmith2010]

if you are not matching the front profile with your tiller, it will start to take too much set in some areas,,so if your bow is coming nicely and maintaining a good unbraced profile, you are probably doing the correct tiller for that front profile,,,

[Kidder]

if you are not matching the front profile with your tiller, it will start to take too much set in some areas,,so if your bow is coming nicely and maintaining a good unbraced profile, you are probably doing the correct tiller for that front profile,,,

So is the theory behind this what del mentioned earlier - that thin wood bends further, safely? Would that mean that a bow with entirely straight limbs be tillered extremely whip tillered, and the opposite, a true pyramid would be as close to a perfect circle? And combinations of front profile would be tillered off of this principle? I’m really just trying to understand what my end goal should be in relation to front profile. Certainly easier to consider with board bows or board like staves rather than bows with significant character. Good discussion and thanks for helping me understand.

[scp]

If I am not mistaken, Del's position appears to be that the side thickness profile matters much more than the front width profile in dictating the proper tillering. I happen to like to keep the thickness same all through the working limb. That means the side thickness profile should dictate the front width profile. Historically it might be true that most bow makers fixed the front width profile first, hence it usually dictated the side thickness profile for proper tillering. But it does not have to be that way. We are free to start with whichever profile first; front width profile, side thickness profile, or side bend profile like reflex, deflex, or recurve, etc. I am with Del in that we are free to do whatever we want, at least as for the selection of the bow profile to fix first. Enjoy the freedom.

Some advanced bow makers, like professional laminated bow designers, might even try to fix all three profiles all together at once to achieve maximum performance. But my "primitive" brain simply cannot manage such a feat.

[Del the cat]

Thanks SCP, nice post , and just to clarify
1. If limbs are constant thickness, the width profile determines the tiller and a true pyramid (tapering to a point gives an arc of a circle).
2. If limbs are constant thickness and a non pyramid width profile is chosen, then the thickness must be adjusted to achieve the desired tiller. I fail to see how this can be described as "the front profile dictating the tiller!" Unless, no adjustment of thickness is made, in which case the bow will likely break, have a really weird tiller or chrysal!
3. Most bows are tillered by removing wood from the belly (thickness) with minor adjustment in width for adjustment of string line, aesthetics, mass removal etc.

The following post from my blog showing constant thickness profiles illustrates these points very well:-
https://bowyersdiary.blogspot.com/2014/12/pyramid-taper-test.html
Del

[RyanY]

Sounds like this is more of a difference in language than anything. Both width and thickness are adjusted for efficient tiller shapes but at the end of the day for any given width profile there will be a most efficient tiller shape. Say for example you have an American style flat bow with parallel limbs to mid limb and then tapers to the tips. One could choose to tiller that bow with a lot of bend in the inner limbs like a mollegabet style bow (parallel thickness taper) or with a very whip tillered shape (straight thickness taper)and it could possibly survive. Both would likely take more set and shoot more slowly than if the tiller is a gentle elliptical shape (gradual thickness taper to mid limb and then parallel to the tips). Yes, the tiller is determined by shaping the thickness but the only reason we know where to take off thickness is by monitoring set and an understanding that generally the most efficient shapes correspond to the width taper. It’s possible to tiller a bow inefficiently with low set and that would be an overbuilt bow.

[Del the cat]

Sounds like this is more of a difference in language than anything. Both width and thickness are adjusted for efficient tiller shapes but at the end of the day for any given width profile there will be a most efficient tiller shape. Say for example you have an American style flat bow with parallel limbs to mid limb and then tapers to the tips. One could choose to tiller that bow with a lot of bend in the inner limbs like a mollegabet style bow (parallel thickness taper) or with a very whip tillered shape (straight thickness taper)and it could possibly survive. Both would likely take more set and shoot more slowly than if the tiller is a gentle elliptical shape (gradual thickness taper to mid limb and then parallel to the tips). Yes, the tiller is determined by shaping the thickness but the only reason we know where to take off thickness is by monitoring set and an understanding that generally the most efficient shapes correspond to the width taper. It’s possible to tiller a bow inefficiently with low set and that would be an overbuilt bow.

A couple of points about the above post... then I'll quit, as I feel I'm probably flogging a dead horse.
1. A Mollegabet does NOT have a "parallel thickness taper" over the short working limb, it needs some taper, it's just not visually obvious over a short working limb.
2. If the curve of the bow was determined by the front proflie... Then on a Mollegabet which has a very abrupt change in the front profile, the tillered curve should display an abrupt change. It does not, the tillered curve sweeps off at a tangent to the curve of the working limb. It is impossible to have a less abrupt change. The smoothness of that transition is simply due to the change in thickness.
Examples:- You can tiller a bow with stiff outer levers regardless of it's front profile.
Similarly you can make a bow with a Molle front profile that has some flex in the levers.
So how does one decide/prove what the ideal tiller is for the Molle front profile? Bearing in mind the levers will always bend a tiny bit 
Is the horse dead yet? (maybe we need an "unsubscribe" button?)
Del

[RyanY]

My point was misunderstood Del. I wasn’t suggesting that mollegabet bows have a parallel thickness taper but that the bend of that specific imaginary bow with an ALB profile WITH a parallel thickness would have a similar tiller profile to a mollegabet style bow. As such, it would perform poorly because it doesn’t have the inner limb width to account for that bend (would take set) and/or the wider outer limbs would be too massive.
To your second point, abrupt is relative. Going from bending to stiff is an abrupt change in my mind. How much more abrupt could it be? The mollegabet maybe isn’t a good example because the issue isn’t that the stiff outer limbs aren’t the correct tiller shape, being stiff/rigid, but that the inner limb often isn’t doing enough work just prior to the transition.

I am of course not arguing that you can’t tiller a bow to any shape regardless of profile but there is an optimal shape for best performance. Would you agree?

[Del the cat]

... but there is an optimal shape for best performance. Would you agree?

No I don't agree, because for every archer or bowyer that says a whip tiller is better for a specific bow style there is some ones else saying that stiff lever outers are better on that same style.
There may be an optimum shape for even stress on the wood along the limb, but that doesn't mean it will be the best performing and I don't think there is any solidly demonstrated evidence for an optimum tiller. (and anyway... optimum for what?)
If you look at ELB flight bows for example, there have been record breaking bows that were whip tillered and ones with stiff outers.
Bottom line is most bows have a front profile that is somewhere between parallel and lightly tapered, and small variations makes little practical difference. The only real significant deviation from that is the extreme paddle bows, very wide pyramids or Molle's, and I think I've explained how a Molle's tiller doesn't reflect it's front profile.
Del

[RyanY]

I would disagree that it makes little practical difference as there are noticeable differences in the amount of set taken by bows with similar width profiles and differing tiller shapes. If this weren't the case then why are we telling new bowyers that their bows bend too much in the fades?

Your evidence from the flight record isn't specific enough to strengthen your argument. Knowing how much goes into those bows, I have no doubt that they are all optimally designed, tillered, and built within their own right and it's possible that many different designs, or even similar designs, if built to maximum efficiency, can achieve similar results. If you asked a bowyer who made a record breaking whip tillered bow that they could have won with any other tiller shape in that same bow, they'll find it preposterous.

Edit: what it comes down to is, if one wants to get the best performance out of any given bow, they should be tillered to take the least amount of set possible. If tillering to a different shape will result in more set then that will most likely lead to less performance than could have been achieved.

Edit2: where that guideline fails is when a bow doesn’t take set but is over-built. So how do you tell the difference between a bow with low set because of correct tiller or because it was over-built? Could test speed but it can be easy to tell based off of the width profile.

[bradsmith2010]

Kidder, Im not sure how to answer your question,,

[Del the cat]

...
Your evidence from the flight record isn't specific enough to strengthen your argument.
... If you asked a bowyer who made a record breaking whip tillered bow that they could have won with any other tiller shape in that same bow, they'll find it preposterous.
...

My evidence isn't specific enough? Errr, it realtes to ELB which is clearly defined.
I believe the same bowyer has held ELB record with both whip ended and stiff ended ELB's but I'm not about to do as search for the relative post.
We'll have to agree to disagree... maybe we are just arguing over semantic...
I real am out now.
Del

[RyanY]

...
Your evidence from the flight record isn't specific enough to strengthen your argument.
... If you asked a bowyer who made a record breaking whip tillered bow that they could have won with any other tiller shape in that same bow, they'll find it preposterous.
...

My evidence isn't specific enough? Errr, it realtes to ELB which is clearly defined.
I believe the same bowyer has held ELB record with both whip ended and stiff ended ELB's but I'm not about to do as search for the relative post.
We'll have to agree to disagree... maybe we are just arguing over semantic...
I real am out now.
Del

Seems like you pick parts of my argument while ignoring others AKA straw man. I would be interested to hear that bowyers input. I could be wrong but I’d bet he agrees that both bows were optimally tillered for whatever differences in design.

[willie]

still looking at pics of some more hill bows. is this too elliptical? A review of this makers bows stated.. "I believe that this may be the smoothest longbow that i have ever shot.  There simply isn’t any hand shock." The bowyer is Dave Johnson.  The pic is most likely not the bow reviewed, but I have no reason to believe the reviewed bow was any different in tiller.

[bradsmith2010]

    kinda  hard to tell with the bow canted for me,, but when a bow shoots great, ,and holds a profile,, the tiller is good,, and design,,is good,, I dont really pay much attention to reviews, cause so many people have different ideas about what is good or not,, beauty is in the eye of the beholder,, I think its just hard to measure,, what is good, or best,, what is best for me, maybe be worst for someone with different requirements,,,,

[Kidder]

I would guess the bow in the picture has no hand shock because it doesn’t start bending until we’ll outside the fades (although as previously noted it’s hard to tell with it canted). I think the take away from this thread is, watch for set, which really equates to don’t have any hinges or flat spots. I can handle that...the reality of doing to may be something else 😉