Tillering technique

[SimonUK]

I just read Robert Hardy's book 'Warbow' and there is a bit at the back where the bowyer Roy King explains how he tillered an oregon yew warbow. I hope I'm not miss quoting him, but it seems he left the bow drawn to something like 26 inches on the tiller for a few hours.  Presumably this was to exercise the wood.

Does anyone else do this?  I was surprised the wood could take this without developing a lot of set.

[Justin Snyder]

  And all this time I thought it was better to never leave it drawn unless you absolutely have to.  I will stick with the pull and let off method of exercising thanks. Justin

[SimonUK]

Exactly!  I'm wondering whether I understood it correctly.

[markinengland]

Simon,
I would have thought it would be very damaging. I do like to leave a bow strung overnight as I think this can help sink the string in, and is is a passive way of exercising the bow without huge risk.
Mark

[Badger]

If a bow is left drawn for a prolonged period of time and the mc of the wood has gone up and down while the bow is braced it will do extreme damage. If a bow is really designed very well and not drawn into the woods plastic state, well inside the elastic boundaries of the wood it should have little effect. I am assuming this is a bow designed to draw about 32". I needed to drop the weight on a flight bow once by about 3# due to a drier climate. I put it on a tiller stick drawn to 28" and left it in the car for thirty minutes with the heater on. No measurable effect. If a bow is slightly underbuilt they will take set almost certainly, but they would overtime anyway. I think this just stablizes the bow a little quicker. Steve

[markinengland]

Steve,
I guess that leaving a bow strung for a length of time would be a very brave way of finding out if you have made a really well designed bow! How would you know if you were getting into the bows "plastic state"? Is this the point where the bow starts to drop in weight and gain set due to over stressing? Is there a point at which this stops? The passage in "Longbow" suggests that Roy King was deliberately leaving ther bow strung so that it would be stressed (but not too much) so that weight would drop during tillering rather than after. Interesting idea.
Mark

[Badger]

mark, for most of my bow making time I was always careful not to overstress or keep them at full draw too long. Looking back all it did was guarantee a bow that would take set later on and be less poundage that I had intended. I am using a lot more mass in my bows now, just trying to make sure it is working where the mass is. Getting better long term results. Steve

[markinengland]

Steve,
You going to write a book one of these days? Seems not too long ago we were chatting and enthusiastic about finding out about making bows. You sure have made a lot since then! It would be good if you could writer about your journey as a bowyer, the things you have learnt. The things you have then had to unlearn as you found out something else!
So what is your basic tillering method now?
Mark

[Badger]

Mark, I will have a chapter in the next bowyers bible comming out TB4. LOL. I still hope at some point we can continue the conversation we started a few years back. Steve

[markinengland]

Steve,
I've been thinking about what leaving a bow drawn does.
Is it any different to pulling the bow many times? If I pull a bow to a certain number of inches and draw weight fifity times, leaving it there for a second or two and letting down and repeating, is that really any different to pulling it to that number of inches and draw weght and leaving it there for the same time or somewhat longer?
I am guessing that doing so is safe for the bow if no one part is being stressed too much. If the stresses are evenly balanced and the total stress is within the limits of the bow and the limits of the final weight wanted. You are really only putting in the stresses that would result in the use of a bow over the weeks and months it would be used. By putting this work inot the bow while it is being made any drop in draw weight happens during the making not after.
Yes another reversal of the dos and don'ts of bow making!
Mark

[Marc St Louis]

Not something I would recommend doing.