Author Topic: Advice on tillering a reflexed stave  (Read 8971 times)

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SimonUK

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Advice on tillering a reflexed stave
« on: May 24, 2007, 07:54:09 pm »
Sorry no photos yet... but I have a stave of wych elm that is set back natrually at one spot close to the handle. The degree of reflex is quite significant and the tips are about 4 inches forward of the handle. How should I tiller it?

I'm thinking along the lines of tillering the handle first, to make it come straight when pulled to the desired draw weight. Then to tiller the limbs. It's going to look a bit like a Victorian bow when finished I'm sure.

Thanks, Simon

Offline Yeomanbowman

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Re: Advice on tillering a reflexed stave
« Reply #1 on: May 25, 2007, 06:22:03 am »
Hello Simon,
I'll look forward to seeing that bow.
One thing about reflexed staves is that the early draw-weight is really high, pro-rata.  Keep this in mind, as it is easy to under shoot the desired weight.  I've found getting a low brace early on is a big help.  Good luck.
J

Offline Kviljo

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Re: Advice on tillering a reflexed stave
« Reply #2 on: May 25, 2007, 07:34:18 am »
If you've got a "template" - a similar finished bow, you could simply transfer the dimensions of that bow onto the reflexed one. That way you should give it a good tiller right away, and be able to draw it more than 4" the first draw, so that it won't flip on the tiller.

Offline Marc St Louis

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Re: Advice on tillering a reflexed stave
« Reply #3 on: May 25, 2007, 08:07:50 am »
Simon
I would tiller the bow out normally but leave the handle a bit stiff. If you tiller the handle out first then you will just have to play catch up with the rest of the limbs after, not good practice IMO. What draw weigth are you going for?
Home of heat-treating, Corbeil, On.  Canada

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SimonUK

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Re: Advice on tillering a reflexed stave
« Reply #4 on: May 25, 2007, 08:33:21 am »
Thanks guys.

Good idea Kviljo - I'm basing it on a recently made ash bow of the same length and draw weight.

Marc, I'm aiming for 65 or maybe 70 lbs at 31 inches.

Offline markinengland

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Re: Advice on tillering a reflexed stave
« Reply #5 on: May 27, 2007, 05:03:00 pm »
I would agree that getting it braced as soon as you can is a good idea as this is the only way you'll get an idea of the shape. Personally I'd brace it to maybe 5 inches and work at getting the braced shape right, exercising it just a few inches. Once the shape looks reasonable forget about the reflex and go for the shape you want it to be at increasing draw length, checking for set to see if you are over straining any areas like the reflexed bit.

SimonUK

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Re: Advice on tillering a reflexed stave
« Reply #6 on: May 27, 2007, 05:22:41 pm »
Thanks Mark. I haven't done anything with it yet... I just keep looking at it in a slightly worried way  :)

If I forget about the deflexed area, won't I run the risk of over-bending it and creating set?

Offline markinengland

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Re: Advice on tillering a reflexed stave
« Reply #7 on: May 28, 2007, 07:13:51 am »
Simon,
A lot depends on how localised and pronounced the reflex or deflex is, how strong the stave is now and how strong you want it to end up. If stringing the bow to a lowish brace height now is acheivable and won't overstrain the wood (go over final draw weight) then perhaps the best thing to do is do that now so you have a good idea of what you really have. It is very easy to end up whip tillered or underweight with too much floor tillering or tillering on a long string.I learnt this the hard way. With reflex it is easy to go to weak as the early brace strength is higher than normal. I think it works well to keep at or very near and never over desired poundage, working the wood to this weight well after every wood removal, working the draw length back, keeping good shape and within draw weight.
Yes, you would have to live with and and make allowance for a pronounced localised reflex or deflex.  Keeping an eye on where any set is developing shows where the wood is being stressed too much and so wood needs taking off every where else. If you aim for spreading even stress over as much of the limb as possible you won't go far wrong.

SimonUK

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Re: Advice on tillering a reflexed stave
« Reply #8 on: May 28, 2007, 10:06:44 am »
Thanks Mark, very good advice. Sorry I meat to say 'reflexed' in my last post.

I'll let you know how it goes.

SimonUK

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Re: Advice on tillering a reflexed stave
« Reply #9 on: July 02, 2007, 07:35:51 pm »
A quick update - it was a disaster. I tried to get an early brace but did a bit too much floor tillering as mark warned. The tips and midlimbs developed a lot of set and it was way underweight. I probably should have made the handle area bend a bit more. I could still get a lightweight bow out of it, but I'd rather move on to a more normal stave! The wood had very narrow rings which makes it weak I understand.

Here are the before and after pics. The back is to the right.

Before: http://s166.photobucket.com/albums/u118/simon2468/?action=view&current=HPIM0074.jpg
After: http://s166.photobucket.com/albums/u118/simon2468/?action=view&current=HPIM0075.jpg