Bending strap

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Bending strap

Postby warrenee » Tue Oct 18, 2011 2:18 pm

Hi,

Can anyone give me any ideas for best materials to make a bending strap and where to acquire them please (say, for a standard bow or arm, for example)? Can't find much in the usual literature that's very convincing.

And here's a question: how on earth might you apply a bending strap to a continuous bow that bends in several different planes? Or would you have to fix this in your former without a strap?

Thanks

Warren
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Re: Bending strap

Postby gavin » Wed Oct 19, 2011 4:43 am

Jim Steele did a course with Charlie Whinney http://www.steambentwood.com - clearly there is a good deal of knowledge there!

I have seen the strap made by Mike Abbott from both seat-belt webbing and stainless steel. I guess steel is superior as it won't stretch. See a local sheetmetal works for scrap strap.
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Re: Bending strap

Postby Emyr Parry » Wed Oct 19, 2011 7:56 pm

I made my strap out of an old bandsaw blade (about 1" wide). I ground the teeth off with an angle grinder, and attached a couple of home made ash handles on the ends, long enough to give a reasonable purchase for bending the arm.
The steel was *really* hard to drill for attaching the handles !

After a few ash arms - I tried an oak arm, bending was OK, but the steel of the old blade reacted with the oak and stained it black - no problem really, but I have now covered the strap with gaffa tape.

edit _ I've just checked out the Charlie Whinney website - wow!

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Re: Bending strap

Postby steve tomlin » Wed Oct 19, 2011 8:46 pm

I've been working with Charlie Whinney over the past year or so. For bending straps, we use lengths of sheet steel that we cut into strips with a plasma cutter. They do stretch and deform over time, especially when we're working with heavy timber. Jim Steele brought a special strap that he'd built specially for bending continuous arms, he'd your man for this.
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Re: Bending strap

Postby warrenee » Thu Oct 20, 2011 1:10 pm

Steel it is then. Will pay a visit to the local forge. Thanks for the replies. Will also maybe contact Jim to see if he'd be willing to share a trade secret or two.

Cheers

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Re: Bending strap

Postby Darrell » Fri Oct 21, 2011 1:06 am

late to the fray, as usual...

I use steel bands that shippers use on large cartons or pallets. The heavy ones are an inch wide and fairly heavy gauge, make good straps for smaller work, and they are *free*. If you are bending stuff bigger than an inch you may have to actually buy steel for your strap.

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Re: Bending strap

Postby AKI » Sat Oct 22, 2011 2:42 pm

Hi

For what it is worth I have used a thin strip of ash say 3-4 mm thick clamped to the arm blank as soon as it comes out of the steamer. Making the arm slightly longer than you need gives a bit more leverage for bending. This is how John Brown the Welsh stick chair maker did it. I have never done a continous arm but I would think you could add strips of ash to the second bends if you took this into account when making the bending former. I am certainly no expert at steam bending but I have made my fair share of arms using a metal strap as per Mike Abbots book & John Browns ash strip & have a slight preferencefor the ash strip, the inner curve of the bend does not compress as much & the outer can stretch but the fibres remain contained. Still requires carefull blank selection & preperation, green wood works a lot better than dry every time. Good luck.

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Re: Bending strap

Postby simon » Mon Oct 24, 2011 9:45 am

Lots of inspiration on Charlie Whinney's site.
My personal favorite in steam bent chairs is here http://www.danhussey.co.uk/
Make it, mend it, wear it out,
Make it do or do without.
FB Simon Lamb Green woodwork
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Re: Bending strap

Postby warrenee » Mon Oct 24, 2011 4:57 pm

For what it is worth I have used a thin strip of ash say 3-4 mm thick clamped to the arm blank as soon as it comes out of the steamer.


Interesting... so you mean sort of like a secondary/sacrificial blank? Along the entire length of your proper blank, or just strips at the points of most stress/curvature?
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Re: Bending strap

Postby AKI » Tue Oct 25, 2011 6:22 pm

Yes the full length of the blank with a small G clamp at each end holding it on, being thin it bends to the shape of a bow really easy before you even clamp it on. I usually re use the strips several times so its not too sacrificial & is not green wood as it dries out so quicly being thin. It just helps support & contain the outer fibres, if its a poor blank it still goes pear shaped.

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Re: Bending strap

Postby warrenee » Wed Oct 26, 2011 1:38 pm

marvellous thanks. One question (perhaps a silly one?) - would there be benefit in steaming that thin blank too? Presumably this might help you bend it a bit easier/quicker, and avoid splitting itself once it goes in the former? Or would it somehow lose it's backing/supportive strength if you did that?
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Re: Bending strap

Postby AKI » Thu Oct 27, 2011 9:28 pm

I have never had the thin strip split out & it will take the shape of the bow & more as it is. You could try steaming it with the blank but I do not think it is necessary. It may be to soft to take the pressure from the small g clamp pad if steamed.

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