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Bows / Re: Bamboo-maple-horn, 98#@28"
« Last post by Badger on Today at 01:15:23 am »
  There is no debate because we don't know how much energy the bow stores; we can only guess at this point. Using virtual mass to predict arrow speed is not debatable; it has been used for decades. Now, just for fun, if he shot, say a 700-grain arrow and then let us guess the speed of the 320 it would be fun. I thought you said 350, I will go back and figure it at 320 with 160 grains VM and see what it comes to.

 Ok my official guess is 292
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Bows / Re: Bamboo-maple-horn, 98#@28"
« Last post by sleek on Today at 12:13:33 am »
Quote from: Tuomo on December 27, 2025, 05:17:46 pm
I chronoed this bow. With a light 463 grain arrow (about 5 gn/#) the result was 256 fps. Quite ok, I am happy. Shot with a shooting machine, witnessed by my friend.

Do you mind solving a debate and making a 320 grain arrow to chronograph?
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Bows / Re: Bamboo-maple-horn, 98#@28"
« Last post by Badger on Today at 12:05:59 am »
      You are wrong the best predictor of speed over an assortment of different weight arrows is virtual mass, which is based on stored energy and efficiency. The lower the virtual mass the less drop in ke as arrows get lighter.

   I would guess that this bow probably stores about 93% or in that area. In that case his virtual mass would be lower and his arrow speed might be closer to 300.
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Bows / Re: Bamboo-maple-horn, 98#@28"
« Last post by mmattockx on December 28, 2025, 11:56:48 pm »
Quote from: Badger on December 28, 2025, 01:39:06 pm
If he is storing 100% of draw force it would put his virtual mass at about 200 grains. Giving him around 285 for 350 grains. If he is storing less energy he would have a lower VM and have a higher speed.

It doesn't matter how much energy is stored because it is the same for both arrows. To get the velocity for the 320gr arrow you simply equate the kinetic energy of both arrows and solve for the velocity of the lighter arrow. That assumes the efficiency stays constant, which it likely doesn't, so the lighter arrow won't quite get to the calculated speed.


Mark
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Bows / Re: Bamboo-maple-horn, 98#@28"
« Last post by Badger on December 28, 2025, 01:39:06 pm »
If he is storing 100% of draw force it would put his virtual mass at about 200 grains. Giving him around 285 for 350 grains. If he is storing less energy he would have a lower VM and have a higher speed.
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Bows / Re: Bamboo-maple-horn, 98#@28"
« Last post by mmattockx on December 28, 2025, 01:22:19 pm »
Quote from: sleek on December 27, 2025, 05:30:53 pm
256fps is certainly on the HOT side of things. Thats fast! Especially with a 460 grain arrow. Id like to see what it will do with a 320 grain arrow.
Based off of energy storage the 320gr arrow will go ~308fps if the bow efficiency stays the same. It will likely drop a bit with the lighter arrow, so figure on a bit less.


Mark
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Bows / Re: Birch bark backing
« Last post by Chumash on December 28, 2025, 06:47:02 am »
Thanks Sleek,

I made all the bark objects myself, except for the John Strunk Bow  ;)

I based my work on an article in PA from Dr. Grayson and on construction techniques for storage containers made from birch bark.
There are also some interesting weaving techniques using bark—but weaving always ties too many knots in my brain  8)

Birch bark and cherry bark are excellent moisture protection, either as storage containers, backing, or quivers.



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Bows / Re: Bow Testing 2023 / 2025
« Last post by Tuomo on December 28, 2025, 02:51:52 am »
I tested one of my bamboo-backed, horn-bellied bows. It’s similar to the 98# @ 28" version, but this one is only 70# @ 28", with the same materials and measurements. The arrow weight was 586 grains (8.37 grains per pound), and the speed was 197 fps! The bow was still fresh, but even so, I really like that kind of arrow speed! Shot with a shooting machine, witnessed by my friend.
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Bows / Re: Birch bark backing
« Last post by sleek on December 27, 2025, 08:03:19 pm »
Quote from: Chumash on December 23, 2025, 09:52:37 pm
Some bark projects.

The birchbark for the quivers is very thick (1,5 - 3 mm)
Birchbark for backing or wrapping a bow has to be thin as sheet of paper. The shavings on one of the bark pieces appear right thickness.

Thats some very nice work, did you make those?
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Bows / Re: Simple Hickory Recurve for 3D selfbow class
« Last post by sleek on December 27, 2025, 08:00:53 pm »
Absolutely good looking bow! Id certainly shoot that at any event. It looks fast too.
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