circular and eliptial tiller

[blackhawk]

By elementary school most of us are taught and know the difference between a circle and an ellipse, and its as simple as that.....a whole lot of explaining here making it more difficult than it really is...

^--- thank you captain obvious 

[adb]

Some of the new folks need visual aids. Pictures speak a thousand words. 'Seeing' tiller is not easy early on in bow making.
I almost went this route of the obvious difference between a circle and an ellipse, but for some people (obviously) it's not that simple. Or knowing how to apply what where.

[half eye]

Captain Obvious must have slept through his elementary school manners class, eh?

adb: agree with you that the photos are most helpful to those trying learn something.
rich

[George Tsoukalas]

Those bows are all very beautifully tillered bows. I'd say Mitch's first pic shows a circular tiller while the others look pretty elliptical to me.
Jawge

[Badger]

  I like to think of it as tiller logic, using a good logical reason for tillering the bow the way we tiller it.

[PatM]

I really think a bow can be circular in the sense that the whole bow describes an arc of a circle or the working limbs describe two separate arcs of a separated circle.
 That may make the general arc of the whole bow appear to be an ellipse, but it seems that this is still just two arcs and three flat spots creating that illusion.
 There are other more accurate terms to describe an arc with a progressively increasing bend.

[Badger]

   Something I do when making forms for heat treating in reflex is to take a string with a pencil on one end and wrap it around something. As I unwrap it the radius of the circle grows larger giving a nice smooth elipse.

[PatM]

That's what I mean Steve. That is not technically an ellipse.  It is is called an involute curve.
http://en.wikipedia.org/wiki/Involute

[Badger]

  Cool Pat, I think involute better describes a desirable curve. Now we have a new word we can use! Primitive bow builders are the greatest bunch of information sharers on the planet. I bet within a year involute will be shoing up on forums.

[Crogacht]

Mikes explanation on the first page makes the most sense to me, now I have a good understanding of WHY. I kind of had an idea, but now I know exactly. The problem I found was, you'd be reading  about a bow and someone would say it has circular tiller... oh but the handle is a little stiffer and the tips are slightly recurved... then I start getting confused again which of course comes down to lack of experience. This is a great thread for the new people though, like me.

[PEARL DRUMS]

Man! Im glad I have no clue how or why I tiller like I do, this thread hurt my pea brain.

[adb]

I think truly circular tiller is not common. Other than bend thru the handle ELBs (which are not common), warbows, or short paddle bows, etc., a perfectly round tiller is much less common than a typically elliptical (or involute curve  ) tiller. Even the pyramid bows (which I build tons of) end up with more of an elliptical than round final tiller shape, especially with a non-bending riser. We've all learned to avoid whip tillering, and leaving the tips just a bit stiff, to improve performance. Conventional wisdom says to tiller a true pyramid bow (with continuous width profile taper), as round as possible. I just don't think it's possible to make such a bow with a perfectly round tiller.

[Badger]

  Pearl, even if you don't it is kinda fun to think we do!

[adb]

I don't know... when I set out to build a bow, I certainly have a goal in mind. Besides draw weight, draw length, and design, I'm visualising the final tiller shape before I begin. This helps me minimise set. Admittedly, I don't always get there. Sometimes this breeds innovation, but mostly you end up with something less than you want.

[Badger]

  ADB, I know exactly what you are talking about. I have never had the greatest eye in the world so I try to find ways to identify shapes earlier. Biggest problem area I struggle with is the transition are about 10" to 14" inside reflexed tips where it quickly becomes static.