Main Discussion Area > Flight Bows
Arvins 62" osage design
Selfbowman:
Ok this is where I get lost and y’all get frustrated with me.🤠if the bow has over a hundred % efficacy why does the arrow go slow? Do we need to change arrow weight?
sleek:
How fast is it with a 450gr arrow? Also with a 150 gr?
--- Quote from: willie on December 28, 2024, 11:51:44 pm ---more...
hmm the projected arrow velocity with 190gr arrow seems low. Should we look to tweak it up, Arvin?
--- End quote ---
sleek:
--- Quote from: Selfbowman on December 29, 2024, 12:51:28 am ---Ok this is where I get lost and y’all get frustrated with me.🤠if the bow has over a hundred % efficacy why does the arrow go slow? Do we need to change arrow weight?
--- End quote ---
A bow can store all the energy it wants, statically. Its dynamic efficiency is what puts speed to the arrow. It seems that the dynamic efficiency and static efficiency are on opposite sides of a sea saw. Its hard to make them play well with each other.
willie:
--- Quote from: Selfbowman on December 29, 2024, 12:51:28 am ---Ok this is where I get lost and y’all get frustrated with me.🤠if the bow has over a hundred % efficacy why does the arrow go slow? Do we need to change arrow weight?
--- End quote ---
you must be looking at the 109 energy storage factor on the charateristics page?
According to the manual
--- Quote ---• Energy storage factor: This value indicates how good the shape of the draw curve is in
terms of energy storage. It is defined as the energy stored by the bow in relation to the
energy that would have been stored with a linear draw curve. The energy storage
factor increases the "more convex" the shape of the draw curve is.
• Factor < 1: The draw curve stores less energy than a linear draw curve
• Factor = 1: The draw curve stores as much energy as a linear draw curve
• Factor > 1: The draw curve stores more energy than a linear draw curve
--- End quote ---
a way of quantifying the "hump" in the force draw curve I think
--- Quote from: Bob Barnes on December 29, 2024, 12:19:19 am ---so you went from carrying the 2.6" to 35% of the limb length to a Pyramid? Is it more efficient?
--- End quote ---
I am not sure why the original plan included the straight section. Maybe as a precaution to handle the extra stress trpically induced by a recurved tip?
I asked arvin if we should compare two designs with and without the straight section. The elimination of the straight section seemed to reduce stress a small amount if the ramp down in thickness just past the fade was made a bit less abrupt, and it definately makes for a less complicated limb taper for the builder.
about the arrow speed:
Stressing the limb more will make the arrow go faster, all other things being equal, stressing the limb less will avoid the possibility of set or unseen damage from compression. Determining a working stress for the materiel thats not too high or low seems to be the trick. but determining what that ideal stress level is, comes from experience and the quality of the wood.
willie:
--- 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 comment about other observations of the accuracy of dynamic functions.
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