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working details for higher poundages

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Del the cat:
Yes, you are correct.... BUT
It's not supposed to be a an exact analysis of a specific example (the exact figure would presumably depend on the bow), more an illustration of the general point that there is string tension, but virtually no draw weight at brace.
Thus the figures aren't correct, but I can't be bothered to make up a rig that allows me to put a scale in line with the string at brace, but trust me I did look to see if it could be easily done.
I just read my blog entry. Initially I say "probably about 40#" which is IMO reasonable.
Later where I say 40# of tension I've amended it to read "substantial tension"

OK... So I caved in and used two bow strings and my cheapo scale to measure brace tension. I got it to a low brace and was turning the scle in the manner of a tourniquet to twist up the strings and increase the height, when it went BANG!
Frankly I no longer care what the exact figures are ::)... there is plenty of tension in a bow string.
For the record, this part tillered bow is about 50# @ 21" and needs 35# on a long string (short as possible to just slip on) to brace it.
Dunno why the scale exploded, it should go up to 50# and was only up at about 15# at about 4" brace... maybe twisting it up unscrewed something.... just done an autopsy. The twisting load broke the plastic housing
Maybe someone else would like to do the experiment >:D?
Del

willie:
Del- thanks for the link,  some good reading at your place.

Colin-  your input is appreciated. I guess it would be easy for someone reading those two threads to think that I was a new guy trying to figure it out by the numbers, and overthinking everything. I have made a few bows out of  staves and a few board bows years back. I suppose that I kind of got carried away in the experimental mode with this one. I started out building this first elb as a practice bow for a bigger one that is on the list, and then I thought , why not use some wood I have never used before, then I thought that I would try tillering a regimen ( badgers no set) that I have never used before, and of course had to learn the mass principle along the way. I have never really tillered a bow out just to see how much the wood could take.... and on and on. In fact if I could learn a new way to approach every single operation with this bow, I would try it. For instance I have ditched my belt sander for a spokeshave, and I like it better, but I must say that it took quite a while to modify the off the shelf tool to make it useful....

this bow showed me that I need a new way to floor tiller If I am going to build an actual warbow. It was not too clear in the other post, but I laid the stave horizontal between two boxes supporting the tips, about 16 inches off the floor. A bathroom scale on each box, to weigh how hard I was pushing down to deflect the bow,  while taking a measurement from the bow hand to the floor. I like the ease  of method and consistency of measurement, but I then realized that I was doing the same thing as I would on the tree with a very very long string, and of course the scale weight only bears a slight resemblance to draw weight, but it should be proportional.
I have the bow up to about  14" draw, and have some tiller adjustments to make. After lowering my goal and thinning yesterday, am pulling about 2.5 lbs per inch with a low brace. I will try to post a pic later, but my camera is not much

Bob

meanewood:
Hi Willie

Just another point about the long string.
I only use linen strings now and I make one up to suit the bow as a long string and then it becomes the short one when needed.
The advantage of this is the tillering process stretches the string out and by the time the bow is ready, the string has done most of its stretching so any adjustments are done by twisting.
This will happen even if using Fast-Flight on the higher poundages.
Its like Colin, said, the long string is only long enough to fit on the nocks!

WillS:
Just to add one minor thing - I've found using side nocks makes life much easier at all stages of bow making, but especially tillering heavy bows.  A single groove on one side of the bow tip makes bracing very easy, doesn't affect the back of the bow and supports the string nicely.

I use horn sidenocks on all my bows now, but even if you don't want to use them at the end of the process and put a more modern nock on, the side nock you cut at the tillering stage disappears instantly once you shape the tips to fit the horn. 

They're not for everyone, but its worth trying a few times to see if you can get them to work.  I've never looked back since using them for tillering nocks!

willie:
Thanks Meanwood

I do have some linen  twine I bought a while back. Its probably not the best as is came bleached even though it was not advertised as such. but I need to get it out as to stay in keeping with "everything  is an experiment" with this bow. I was having trouble with the dyneema I was using as it kept slipping, and no two braces were alike.


Colin
I made a pull to 17" when I had the tiller looking better, but the same uneveness between limbs came back. Need to work on the left limb and maybe reduce poundage some as the bow just took some set at midlimb. each outer limb droops about a 1/4"  more than before I made the pull. Middle half of the bow is has not taken near as much set. bow is now 70" ntn.

Will
I got some really ugly temporary nocks that are held on with hot melt glue. (so ugly that the camera refused to let them in the picture), but it seems like a good idea. Do you need quite a thick string when using softwood with high poundage designs?

willie

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