Saturday, 4 November 2017

Long String On the Tiller

I'm making a 110# warbow from Austrian Yew that I've had waiting for my attention for some months. It's a tricky stave with reflex at one tip and deflex half way along the other.
On one of the Facebook groups there has been someone having trouble tillering a warbow so I thought I'd take regular pictures (captured from video) to help show the progress.
I also wanted to test an observation from one of the hugely respected guys on Primitive Archer (Steve Gardner aka Badger), which is:-

If you have a "long string" that will just slip onto the bow and only dangle down 6" you can read off draw weight and length from that and it will closely tally to the draw weight and length when braced.

It's too easy to take everything one is told as fact, that would be fine if everyone was reliable, the problem is there are a lot of well meaning armchair experts out there. Of course Steve isn't in that category, but seeing is believing, so I did the test.

The top pic shows the stave with no force on it in the upper image, each subsequent image is at 110# on the string that dangles 6".
The final seperate image is with it at a 5" brace pulled to 110#.

It's an absolute pig to get the bow strung and I was having to winch it back to a full 110# on a very long string to give me room to get it braced, and that's where the confusion can lie as the very long string comes back a huge distance because it is dangling down a foot or so.

Right, so in the composite picture, the lowest image shows it at 110# at 24".
I braced it (slightly low about 5") and with some trepidation pulled it back gradually increasing the weight (video running of course)...
At 110# it came back just under 25" which is pretty damn close and very useful.


The moral of the story is:-
1. Make sure you long string only dangles 6"
2. We are all still learning!

There is a slight caveat here, when you have it braced, don't just heave it back to full weight if the tiller isn't good, as the bow will be flexing a bit more than it was on the long string. If you study the pics, you'll see the tips are coming back about an extra inch.
You'll also see that as it's coming back 15" I only have 5 more inches to get the tiller sorted!
That's the rub with a warbow, by the time it's braced you're almost there!
The final pic showing drawn and unstrung together helps to show how it's bending and where I need to take off a little wood. The deflex area middle of the right limb isn't bending enough and the entire right limb is a bits tiff.

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