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Working on a giant bow to beat Allen Case!

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avcase:

--- Quote ---In your extreme example  where efficiency increased before dropping, were your arrow velocities obtained from a chrono, or were bow and arrow considered together, using velocities assumed from actual arrow distances?

--- End quote ---

I was bench test shooting a real bow using a shooting machine fixture and two chronographs. The shooting machine fixture precisely releases the arrow at a pre-determined draw length. I also have a paper holder for the arrow to pass through so I can determine the quality of the arrow Flight based on the shape of the hole it makes in the paper.

I don’t think it is necessarily a good thing to see efficiency jumps like this. I’d prefer that it behaves much more predictably over a very wide range of arrow weights. I think what I am seeing has to do with a couple of natural frequencies cancelling each other out at certain arrow weights and shot speeds.

Alan

avcase:

--- Quote from: Badger on March 30, 2018, 09:13:30 pm ---  Willie, because of the lower acceleration rate I thing the 6# arrow would be the better choice which would be based on peek draw force as opposed to stored energy which I originally allowed for. I also think the bow would need to be scaled up from a flight bow type bow, not so much in reflex but in the limb shape. All the dynamics of it would respond much better using draw force instead of stored energy for the arrows.

--- End quote ---

Shooting a 6-lb arrow out of the giant bow would be the equivalent of shooting about a 1/2 ggp arrow out of a 50# bow!  This will be a dry fire situation!

Selfbowman:
Guys you know I am not a math guy! I think the problem is in the material not the mass. The wood is not 10 times as dense. It's just bigger and heavier. I also reserve the right to be wrong cause I don't know. I have said before that mass is mass but maybe not with giant bows of the same material. Arvin

Badger:

--- Quote from: Selfbowman on April 03, 2018, 02:36:52 am ---Guys you know I am not a math guy! I think the problem is in the material not the mass. The wood is not 10 times as dense. It's just bigger and heavier. I also reserve the right to be wrong cause I don't know. I have said before that mass is mass but maybe not with giant bows of the same material. Arvin

--- End quote ---

  Arvin, scaling up the composition of the material is tricky. My thinking is that it should be much less dense to be ideal. Not even sure why i think that. Maybe in my head I am thinking if I scaled up the cell structure in the wood it would be lighter.

DC:
Sometimes scaling things up or down just flat doesn't work. That model schooner that I posted a while back is scaled down exactly from the original and it won't float upright by itself. It needs 5 pounds of ballast hung 18" below the boat or the slightest breeze knocks it over. Sails have (basically)2 dimensions(square0 and hulls have 3(cube) and they have to be of the original design or it won't work.

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