Determining Bow Efficiency
"... kinetic energy (KE in foot-pounds) = ((arrow weight in grains) x (velocity in fps squared)) / 450,240
...
to get the efficiency, just divide the arrow KE by the limbs PE (potential energy in foot pounds) and multiply by 100 to get it in a percent."
Bow Efficiency | Archery Talk Forum
dryadbows.com/wp-content/uploads/2021/04/connie-Defining-Bow-Performance-Dryad.pdf
According to BackyardBowyer (regarding the 40# fiberglass PVC bow)
It delivers a 10GPP arrow with 18.5 foot pounds of energy. As for actual efficiency, it's around 45% efficient. Most flattened PVC bows of the same weight are about 55% efficient. The most efficient traditional bow I've used was a bamboo horse bow by Mead Longbows at 76% efficient.
I asked ChatGPT to help identify information, and it lied pretty much immediately, even while finding interesting sources. So I'll start with the sources and summarize what I find.
- 37-38% efficiency for the guy's PVC bows
Backyard Bowyer - 72% efficiency for 3/4" PVC flattened bow
- 53% efficiency for a 1" flattened bow
Takeaway: Adding mass to the bow decreases efficiency.
What could we do with this information?
- Experiment with a 1/2" bow with fiberglass rods
- Flatten the limbs and then shave off some PVC in equal amounts on both limbs?
- Shave off sounds interesting, like using that wood-shaving implement