Primitive Archer
Main Discussion Area => English Warbow => Topic started by: acker on November 28, 2009, 12:51:00 pm
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What do you think guy´s does the mass theory work on warbows or is that a different kind of story?
Non of my stronger English longbows does fit into the mass theory, they do all have a good bit more weight then they should have if you believe in the theory.
What about your warbows ? Do they fit into the theory?
Thanks , acker
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almost 50te views....no answer
No one here with an idea ???
Or are all your bows to "heavy" as well.
Thanks acker
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Dunno what the 'mass theory' is so I can't comment.
BTW what is the apostrophe there for in the title?
Del
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All my D-bows are heavy. The stiff handles are usually corresponding to mass principle (tbb4 Steve Gardner)
Don't make any heavy warbows though so.. not what your asking about.
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While I was developing the formula I built quite a few arc of the circle tillered english long bows from 35# on up to about 160#. They actually tend to come out a bit lighter than the formula suggests the higher the draw weight goes. The way you tiller the bow has a huge effect on the projected mass. bend through the handle arc of the circle tillers will be the lowest mass of all bows because they will be narrower with a deeper cross section. Past about 80# draw I started taking off an additional 1 oz of mass for every 5# draw weight. The woods I used ranged from pacific coast yew, maple, oak, osage, dog wood, hornbeam, ipe, plum, crepe myrtle, pine, soft maple, just about anything I got my hands on. I judged them on how much set they took and how they performed. Steve
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I'm huge fan of the mass principle, respect!
Really like your chapter in tbb4.
Do you account for any wrapping of the handle on the charts on p 92 tbb4. Or what is normal for a wrapping.
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Handles are something you just have to estimate on a bit, I pretty much based everything on a standard type self bow handle. If the bows are comming in over weight it usually means that the moisture is a bit high. If they are comming in underweight it can mean the moisture is too low.
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@Badger: Thanks for your answer , you made a great work on that chapter impressive :)
my latest Elb:
78" long 100# @30"
Ends are a bit stiff and a less bending handle, tiller more elliptical.
trilam Bo /morado/ bloodwood
Weight 805g but shouldn't the bow weight be something around 700g?
wide to depth ratio 1:1 ~ 1:1,1
no perry reflex
(http://www.bilder-space.de/upload/27.11WL4CfRfUvYCy5UG.jpg)
(http://www.bilder-space.de/upload/27.11ZpqqgkiX7xCjO31.jpg)
(http://www.bilder-space.de/upload/27.11dpVVpY5T9bSJmbv.jpg)
(http://www.bilder-space.de/upload/27.11UJ6ZJdcSgG2HNBT.JPG)
Thanks acker
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The only heavy bows I've managed to come close to Badger's mass target have been laminates and it didn't seem to be too critical (performance wise) as long as they were not overbuilt. However, I think the mass placement is as important as anything as I'm sure he would agree.
Great theory though and I find it really handy when tillering and knowing when your getting close to about the right amount of wood.
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Aker, I consider that the ideal tiller for an elb of heavy weight, very nice bow there. I would calculate that with a 4" stiff handle and a 32" draw for a close mass estimation based on that tiller shape. David Dewey converted my mass theory into a calculator on an excel spread sheet. very handy and easy to use. Simply fill in the blanks and it spits out the answer. I have it on my other computer but will e email it to you if you like. Steve
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Thank you badger :)
A compliment from one off the master bowyers is always a nice thing to hear / read :)
Yes , I heard of the program and i really would love to have it .
I'll send you an Pm with my Email address .
Thanks acker
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Actually all my heavy bows seem to comply rather well with predicted mass, I have made few which are lighter and they also shoot better. These are mostly selfbows.
J.
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I calculated the mass again the way Badger told me to.
Now the mass seems to be allright on that bow.
[attachment deleted by admin]
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If you are working with a dense wood for instance you may find that you can't get the formula to work. When this happens the formula is telling you to redesign the bow. A boo backed ipe would be almost impossible to make at 100# and 76" long unless you made the tiller elyptical, by the same token using a very light weight wood might require that you use an arc of the circle tiller inorder to maintain the elb cross section. Steve
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I have only made a couple of ELB style bows with 7/8 cross section, and they came in under the physical weight projected by Steve's mass theory. They seemed to be just fine for a couple of months, but then they really started to take set. This in spite of the fact that they were exceptional quality wood. One was boo backed Ipe. I for on think that the formula is a great guideline to estimate with.
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Only a photo of the nocks...
(http://www.bilder-space.de/upload/30.11mrZ8wGmAl18PgIo.jpg)
acker