Main Discussion Area > Flight Bows
Arvins 62" osage design
sleek:
--- Quote from: willie on December 29, 2024, 03:05:22 am ---
--- Quote from: sleek on December 29, 2024, 02:06:02 am ---How fast is it with a 450gr arrow? Also with a 150 gr?
--- End quote ---
150 gr 237 fps
450 gr 178 fps
the 50# draweight is at 25" from the back of the bow and with a brace height of 7"
when the bow is built we plan to offer feedback to Stefan, the developer of the program. Hopefully he will feed back with some other observations concerning the accuracy of some of the dynamic functions.
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Make it a 26 inch draw from the back of the bow if you can. 450 grains us a benchmark I use, and if it doesnt hit 185fps minimum i wont shoot flight with it. But I also pull 26. So I need 26 to see a good comparison.
mmattockx:
--- Quote from: willie on December 28, 2024, 11:23:59 pm ---Hi Mark,
if you dont mind trying the calculator in autocad that would be nice.
The limb crossection at the fade the time looks like a segment of a circle who's radius is 3.5" on top of a rectangle, both elements being 2.6" wide. (my sketch here shows the heigth of the segment to be about .28" and the "equivelent' rectangular section from Virtualbow is 2.6" wide by .42" thick, but that thickness is still tentative and may not work further down the limb as there is a gentle thickness taper in spite of the bow being a pryamid back, thus It would be interesting to see if that composite section can be compressed in the vertical direction without the radius of gyration changing.
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I will try to get a look at this in the next couple days and let you know.
Mark
Selfbowman:
What spine do we need on a 24” 150gr arrow for this bow. Flight arrow. Also if we where to shorten the working part of the Limb to 24” from center of bow. I think I use a 5”-6” brace or 6-1/2 -7” from back of bow.where did you measure brace from? I think in this scenario measure to back of the bow will be best.
willie:
the program inputs brace from the back at the handle to the string, So with a 2" thick handle, 5" "inside to inside"
I will try to anwser the part of the question that I think you were asking me, maybe the arrow part was for sleek?
--- Quote from: Selfbowman on December 29, 2024, 02:40:42 pm ---Also if we where to shorten the working part of the Limb to 24” from center of bow.
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Shortening the working part of the limb means some other part of the limb has to work harder if you want to keep the the draweight at 50#. Kinda like playing whack-a-mole if you are concerned about stresses getting too high someplace else.
right now, the limb is bending significantly 5" out from center and is fully working 6" out from center.
the limb starts getting thicker 22 inches out from center but is still working.
the first screenshot below shows the stress at brace, and the red line is drawn at the maximum stress (just under 10,000 PSI as read on the scale on the left hand side.
the same line is shown in the second screenshot of the limb at full draw. The maximum stress has risen to 16,000 PSI and the area above the red line represents some of the area where the limb is doing the work that will be returned to the arrow upon release. If I could over lay one pic on the other you would see a better representation.
The green line shows how much the stress has risen out at 24 inches from the center, but the limb is only an inch wide there, so the work contributed at 24 inches out will be just over a third of the work done at the fade which is 2.6 times wider.
Normally, when one tillers a bow and starts to see set or loose early draw weight, one just reduces the weight goal and calls it another 35 pounder for the ladies.
what do you think about if you can come in at 50# without set, or said another way, the bow is basically overbuilt.....
putting some more hook into the recurves and taking a few scrapes to get back don to 50#, untill the arrow speed comes up?
I dunno how many times you can rebend the tips but you are our master osage bender......
Selfbowman:
Willie I have not reached the full recurve design and yes I can heat it up a few more times to get there. I’m waiting to see the final design thickness to proceed in that recurve section. Right now we have 56 in thickness 26” from center of bow . that is the thinnest part of the limb.
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