Main Discussion Area > Bows
AVCase design Arvin bow build
bradsmith2010:
when you glue lams together,, it is very different than a self bow,, perry reflex is a good example,, the glue enables the bow to hold a reflex a self bow would not,, and if the backing is too thick it will crush the bow,, the glue lines and lams are different than a self bow, even though wood is wood,, the glue changes that,,
its seems to me if you pull a bow on a pully there is one pressure point on the string,, if you shoot the bow then there are usually three fingers on the string,,, that makes the pressure different on the limbs,,, and the tiller may need to be adjusted for that,, I think thats why when the bottom limb is a bit stiffer it compensates for that and makes good arrow flight easier to achieve,, if the shooter does not have a good release,,,the tiller wont make much difference,, but as the shooter becomes more proficient,, the difference is more clear,, especially on shorter bows,,,
Selfbowman:
--- Quote from: sleek on March 08, 2023, 05:04:34 pm ---Hey Arvin, how wide and long is that bow?
[/quote
1-1/2 to mid limb or there abouts. 67” ntn
--- End quote ---
mmattockx:
--- Quote from: bradsmith2010 on March 09, 2023, 12:05:20 pm ---the glue lines and lams are different than a self bow, even though wood is wood,, the glue changes that,,
--- End quote ---
I keep seeing people say this, but no one has ever convinced me this is correct. Glue lines are very thin and the glue should be as strong and stiff as the wood if the bow is to survive, so why would it change how a limb bends? I agree using lams allows techniques that aren't available with a solid piece of wood, but if you cut strips off a board and then laminate them back together why do you think the properties have changed?
--- Quote from: bradsmith2010 on March 09, 2023, 12:05:20 pm --- its seems to me if you pull a bow on a pully there is one pressure point on the string,, if you shoot the bow then there are usually three fingers on the string,,, that makes the pressure different on the limbs,,,
--- End quote ---
I agree. How a particular archer applies finger pressure can affect the tiller a bit and a bad release really does screw everything up.
Mark
avcase:
The difference between a 50# design and 35# real bow is too great to easily explain away with a typical amount of variation in material properties.
Difference #1: Engineer used wrong material properties (-6 pounds draw weight)
I went back through my tests of various osage material samples, and compared those material properties to the material properties I actually used. Guess what I found? The engineer (me) was not using the same properties in my model as I had measured! This explains a little under 6 pounds draw weight difference.
Difference #2: The real bow had about 2” reflex instead of 2.75” in the design. (-2 pounds draw weight)
This explains about half the discrepancy. I would have expected the real bow to be around 42# at 28” after correcting for these discrepancies.
So, where is the rest of the lost draw weight coming from? We will know more when we measure the material properties of the pieces from Arvin’s stave. I don’t expect this to be a major contributor. I’m sure it would be very noticeable if the stave was significantly sub par.
A couple more pounds may have been lost if the bow took some set. There is still at least 5 pounds missing draw weight to account for.
Alan
PEARL DRUMS:
The missing 5# you are trying to account for is on his shop floor.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version