Because of my age, I'm relegated to hunting with 40-45# bows, so I have some familiarity with bows in that range.  Both of your examples are close to 10 gpp, which is my preferred arrow weight for hunting.  I prefer your option that uses a lighter shaft and a heavier point weight to get there, as I understand from reading Dr Ashby and others that that configuration is generally more lethal than having the weight more evenly distributed along the arrow.  However, your example are close enough that I'll go with "moo" point.

For you aluminum shaft guys, I have Eastons for as little as $20 a dozen.. some of them are shafts, others are fletched with feathers and some with vanes that can easily be removed. 

Thank you, BigJim

Quote from: willi on November 29, 2025, 04:44:57 PM

Quote from: Cupcake on November 11, 2025, 04:26:58 PMIn order to get a higher voltage to work for the heat strip a higher resistivity material needs to be used.  The most prevalent materials in SS all have about 9 x 10^-8 ohms per m²/m.  If we wanted to use 12 volts to run the heat strips the material would have to be about 6x higher in resistivity.

I calculate about 0.2 ohms resistance for the SS from Kirk's data.  If you run 12 volts through this strip it would dissipate 7200 watts and require 600 amps.

To get 120 watts at 12 volts requires 1.2 ohms.  One could place 0.5 ohms resistors at each end that bolt to the strip and their temperature would be put into the strip, albeit at the ends, so it is not likely to heat evenly down the strip.

Nichrome has more than 10x the resistivity of the SS so that is why it works so well.

Now that I have spent a bit more time on this problem and did a bit of math and see that we need a higher resistance material I conclude that with SS strips you need very high current and low voltage.  To use a higher voltage and lower current requires a higher resistance. V = I x R

why not calculate and adjust  the width of strip that will let the battery charger (without the voltage controller) work at 10 amps ?
(assuming the charger has enough duty cycle % at 10 amps for the length of the job)

The SS heat strips in the forms are two different widths 1.75" and 1.5" . Two strips are used. One on top, and one on the bottom, and they work as pressure strips too. For TD bows there are two 36" length strips, or 6' total length to heat up. With a one piece bow form there are two strips 6 feet long.... The longer strips need more voltage to heat them than the TD heat strips.   Adjusting width on the strips is not an option.

Kirk

Quote from: Maclean on September 18, 2025, 07:37:39 AMI'm a big fan of the American Leathers Big Shot glove. Good finger protection while giving great string feel and a super clean release.

What he said!!!

Right on, right on, Flemish Twister and Durp.  I've jumped up 1 and 2 spines and they never fly as good when they're the same length, and always end up around 700gr.  They hit like a freight train, and I get to shoot bigger heads, but they just don't seem to ever bareshaft as well.

Joey Tribiani from 'Friends', wasn't the brightest guy and didn't know moot.  Thanks for the rocketry crash course.  I've been leaning towards "moo", or faster is better, as the ft-lbs, in the 3Rivers calculator are near identical, might as well get the speed as long as quiet enough.

Very nice bow!! The riser is really cool, and I love the static tips.  At full draw it's almost like those tips are talkin" back sayin", "you ain't bendin' me over".

Quote from: durp on November 29, 2025, 03:40:20 PMThe one that flies the best 

Right on!  Personally I just start with the arrow I want to shoot and try and build up from there.  11-12 grains per pound as the goal. Example my long bow I shoot a .204 ID arrow that has 6.7 gpi. 80 grain inserts and 150 grain BH gets to 460 +/- grain total. Never bothered figuring foc.  I was looking for lighter faster and these fly like lasers. 

Quote from: Cupcake on November 11, 2025, 04:26:58 PMIn order to get a higher voltage to work for the heat strip a higher resistivity material needs to be used.  The most prevalent materials in SS all have about 9 x 10^-8 ohms per m²/m.  If we wanted to use 12 volts to run the heat strips the material would have to be about 6x higher in resistivity.

I calculate about 0.2 ohms resistance for the SS from Kirk's data.  If you run 12 volts through this strip it would dissipate 7200 watts and require 600 amps.

To get 120 watts at 12 volts requires 1.2 ohms.  One could place 0.5 ohms resistors at each end that bolt to the strip and their temperature would be put into the strip, albeit at the ends, so it is not likely to heat evenly down the strip.

Nichrome has more than 10x the resistivity of the SS so that is why it works so well.

Now that I have spent a bit more time on this problem and did a bit of math and see that we need a higher resistance material I conclude that with SS strips you need very high current and low voltage.  To use a higher voltage and lower current requires a higher resistance. V = I x R

why not calculate and adjust  the width of strip that will let the battery charger (without the voltage controller) work at 10 amps ?
(assuming the charger has enough duty cycle % at 10 amps for the length of the job)

Thanks. On another platform, a few people asked if I had construction plans, so here is a video...
Video