Author Topic: Tiller shape vs front profile  (Read 17735 times)

0 Members and 1 Guest are viewing this topic.

Offline Del the cat

  • Member
  • Posts: 8,301
    • Derek Hutchison Native Wood Self Bows
Re: Tiller shape vs front profile
« Reply #15 on: June 24, 2021, 04:44:18 am »
IMO.
All good in theory, but for the average bloke making a bow the difference in those front profiles and tiller shapes is all but negligible. (And at a casual glance it's hard to spot the difference)
Especially if you start to factor in something like deliberately favouring stiff tips.
I've just spent ages helping a guy on an FB forum who was making 20# bows with a hinge in each limb. Finally got him to make one over 40# with no hinges... the front profile was 100% irrelevant.
Del
« Last Edit: June 24, 2021, 09:03:59 am by Del the cat »
Health warning, these posts may contain traces of nut.

Offline BowEd

  • Member
  • Posts: 9,390
  • BowEd
Re: Tiller shape vs front profile
« Reply #16 on: June 24, 2021, 08:11:17 am »
Your student thickness tapered too quickly or unevenly in areas to have hinges.Hard to spot with pictures and not actually being there.Some students take longer to get the hang of this tapering than others.
BowEd
You got to stand for something or you'll fall for anything.
Ed

Offline Pappy

  • Global Moderator
  • Member
  • Posts: 31,942
  • if you have to ask you wouldn't understand ,Tenn.
Re: Tiller shape vs front profile
« Reply #17 on: June 24, 2021, 08:53:06 am »
I pay little attention to the backs profile , I just try and spread the wealth over the whole limb, starting in the mid 2/3 then closer to the finish toward the fads and out toward the tips, I usually  leave the last 6 inches or so stiff, to much bend to start off at the fads usually causes me problems because that is where it wants to bend anyway and if I get the tip moving to much to early I will get a whip tiller, either one not good. I am usually using wood with some knots or  in prefections so what yall call the prefect tiller is not always achieved but works for me. :)
 Pappy
Clarksville,Tennessee
TwinOaks Bowhunters
Life is Good

Offline PatM

  • Member
  • Posts: 6,737
Re: Tiller shape vs front profile
« Reply #18 on: June 24, 2021, 02:08:19 pm »
IMO.
All good in theory, but for the average bloke making a bow the difference in those front profiles and tiller shapes is all but negligible. (And at a casual glance it's hard to spot the difference)
Especially if you start to factor in something like deliberately favouring stiff tips.
I've just spent ages helping a guy on an FB forum who was making 20# bows with a hinge in each limb. Finally got him to make one over 40# with no hinges... the front profile was 100% irrelevant.
Del

 Agreed. 


bownarra

  • Guest
Re: Tiller shape vs front profile
« Reply #19 on: June 25, 2021, 03:04:31 am »
IMO.
All good in theory, but for the average bloke making a bow the difference in those front profiles and tiller shapes is all but negligible. (And at a casual glance it's hard to spot the difference)
Especially if you start to factor in something like deliberately favouring stiff tips.
I've just spent ages helping a guy on an FB forum who was making 20# bows with a hinge in each limb. Finally got him to make one over 40# with no hinges... the front profile was 100% irrelevant.
Del

No Del it is also very good in practise!
If you don't practise it you will get excessive set and over/under strained wood :)

Every piece of wood can bend a cewrtain distance before taking set.
Make it thinner it can bend further.
Thicker it can bend less before damage.
That is 'tiller logic' in a nutshell.

straight thickness taper eg. a pyramid, minimal thickness taper = no (or minimal!) change in bend radius.
parallel width limbs tave to taper in thickness = elliptical tiller. As you progress along the limb.....it gets thinner....right???? Therefore the limb that is getting progressively thinner must also progressively bend further as it gets thinner.
Stiff tips etc don't alter the fact that wood takes set at a certain bend radius :)
Maybe the difference is subtle but that doesn't matter the difference is there :)
Just like the difference between a balanced car wheel. Take a couple of those weights off and see how well it works :)

Front profile dictates tiller because of the above!
Front profile by definition cannot be irrelavent to tiller shape - the two are interrelated.
The wood doesn't think front view is 100% irrelavent.

Offline PatM

  • Member
  • Posts: 6,737
Re: Tiller shape vs front profile
« Reply #20 on: June 25, 2021, 08:47:40 am »
    Most guys can't even detect an even curve so going beyond that and trying to see an involute type of curve is a step too far.

  Looking for a "nice even curve" is a good goal.

 I still agree with Del.

Offline Don W

  • Member
  • Posts: 402
    • diy.timetestedtools.net/
Re: Tiller shape vs front profile
« Reply #21 on: June 25, 2021, 09:32:50 am »
Maybe somebody can give good examples of the different curves on bows so new guys can see the images side by side. That would certainly help everyone.

Maybe a thread with "here is the front profile" and "Here is the tiller shape" and why is it right or wrong.
Don

bownarra

  • Guest
Re: Tiller shape vs front profile
« Reply #22 on: June 25, 2021, 09:55:39 am »
    Most guys can't even detect an even curve so going beyond that and trying to see an involute type of curve is a step too far.

  Looking for a "nice even curve" is a good goal.

 I still agree with Del.

To each their own :)

But to play devils advocate.....how do you judge your nice even curve???

bownarra

  • Guest
Re: Tiller shape vs front profile
« Reply #23 on: June 25, 2021, 10:00:20 am »
Maybe somebody can give good examples of the different curves on bows so new guys can see the images side by side. That would certainly help everyone.

Maybe a thread with "here is the front profile" and "Here is the tiller shape" and why is it right or wrong.

That is a good idea.
I'm tillering a few elbs at the moment. They are a great example of elliptical/circular tiller. If you tiller an elb to have an arc of a circle 'even' curve it will be handshocky. However if you tiller one with the correct, quite prononced elliptical tiller you will get less set and a totally shockfree bow. I'll try and take some photos for an example of elliptical tiller.
The differences may be subtle but they matter.

Offline Del the cat

  • Member
  • Posts: 8,301
    • Derek Hutchison Native Wood Self Bows
Re: Tiller shape vs front profile
« Reply #24 on: June 25, 2021, 10:08:50 am »
Maybe somebody can give good examples of the different curves on bows so new guys can see the images side by side. That would certainly help everyone.

Maybe a thread with "here is the front profile" and "Here is the tiller shape" and why is it right or wrong.
Here you are just to clarify ;)
Top pic is a 110# Yew character warbow tillered "arc of a circle" but with some character. Natural deflex in the lower/left limb, and a big knot and dip just right of the grip.
bottom pic is a 75# Yew ELB which at a casual glance looks to have elliptical tiller... but does it really? It just has a slightly stiff grip section where the billets are spliced. Or is each individual limb is "arc of a circle" ?
The front profile of both is roughly parallel for about 3/4 of each limb, then a smooth curve to a point at the tip with horn nocks.
Anyone is welcomed to try and critique the tiller, but it is far more a response to the actual wood than it is to the front profile!
IMO. The real case which disproves the "front profile" theory is a Mollegabet, from the front, you can see the outer limbs are narrowed... but they can be either stiff levers or working limbs, or somewhere in-between!
NOTE:- I'm not saying front profile is irrelevant, just that it's relevance is often heavily masked or outweighed by other factors when using staves.
Del
« Last Edit: June 25, 2021, 10:17:36 am by Del the cat »
Health warning, these posts may contain traces of nut.

Offline PatM

  • Member
  • Posts: 6,737
Re: Tiller shape vs front profile
« Reply #25 on: June 25, 2021, 10:23:43 am »
    Most guys can't even detect an even curve so going beyond that and trying to see an involute type of curve is a step too far.

  Looking for a "nice even curve" is a good goal.

 I still agree with Del.

To each their own :)

But to play devils advocate.....how do you judge your nice even curve???

   The typical  circle held against a bent limb orc a gizmo will do that.

Offline George Tsoukalas

  • Member
  • Posts: 9,425
    • Traditional and Primitive Archers
Re: Tiller shape vs front profile
« Reply #26 on: June 25, 2021, 11:03:00 am »
I agree Meare Heath bows with parallel limbs should be tillered elliptically. Pyramid bows should be tillered with a circular tiller where a good part of the bending occurs  near the handle where most of the wood is.

But there are exceptions. I prefer the Meare Heath style but if the limbs get too thin I begin to narrow them to bring the tiller home

Jawge
Set Happens!
If you ain't breakin' you ain't makin!

Offline willie

  • Member
  • Posts: 3,201
Re: Tiller shape vs front profile
« Reply #27 on: June 25, 2021, 03:27:21 pm »

That is a good idea.
I'm tillering a few elbs at the moment. They are a great example of elliptical/circular tiller. If you tiller an elb to have an arc of a circle 'even' curve it will be handshocky. However if you tiller one with the correct, quite prononced elliptical tiller you will get less set and a totally shockfree bow. I'll try and take some photos for an example of elliptical tiller.
The differences may be subtle but they matter.
Looking foreward to the pics. :)



IMO. The real case which disproves the "front profile" theory is a Mollegabet, from the front, you can see the outer limbs are narrowed... but they can be either stiff levers or working limbs, or somewhere in-between!

Del

As a basic principle of tillering a simple bow, the bowyer strives to strain the wood equally. this results in a bend appropiate for the thickness taper.

presuming the bowyer is doing a good job and the bow has enough nock to nock length to be drawn to its desired drawlength, then a longer stave can yeild a design with more features.  For instance, a nonworking handle or stiffer tips or levers. 

I am not sure a bow with additional features that incorporated lesser strained tips or handles would "disprove" basic tillering principle, it's just a matter of applying the basics to the parts of the limb that work.

Offline RyanY

  • Member
  • Posts: 1,997
Re: Tiller shape vs front profile
« Reply #28 on: June 25, 2021, 03:46:31 pm »
Itís not possible to tiller every bow the same way and get low set. Different shapes need to be tillered differently just because of that. How much of a difference that makes or how it needs to be done is up for debate but low set and then speed will tell the truth.

I do agree for the average bowyer that this might not matter but many of us strive for an ideal which can be part of the fun.

Offline Del the cat

  • Member
  • Posts: 8,301
    • Derek Hutchison Native Wood Self Bows
Re: Tiller shape vs front profile
« Reply #29 on: June 25, 2021, 07:24:54 pm »
"I am not sure a bow with additional features that incorporated lesser strained tips or handles would "disprove" basic tillering principle, it's just a matter of applying the basics to the parts of the limb that work."
A principle that is applied selectively and only when it suits is hardly a principle is it?
Del
Health warning, these posts may contain traces of nut.