an actual draw force curve

[simk]

I rarely do this, as to me they all look similar. But in this one I was interested somehow. This is another Horn Wood Bamboo Composite. 65" longbow. minimal deflex. 4" net reflex. Stiff but light outers, basically a lever type principle. Cannot test fps because my chrono is broken. 195-200 @ 8 gpp is only my guess. And my sheet does not calculate the "energy storage factor" like virtual bow does. So I asked gemini AI to calculate and it said it was 120% which I do not believe myself  but its an intersting curve.

[Badger]

 I see 99.9 % not 120%. It is 120% of the line below your force draw, what does that represent?

[Selfbowman]

Looks like a great force draw to me.

[superdav95]

Nice curves on the bow.  Draw curve looks smooth

[simk]

Badger, I have not written that excel sheet and only understand Kinetic Energy and Dynamic Efficiency here. But the 99.9 you see must something different than "energy storage factor". This Energy storage factor to my undertstanding is the comparison to a linear straight longbow curve. In this case it must be above 100% because the curve has that hump and no stacking.

but this this is now leading me to the following question....

Please:

How do we draw the curve of that hypothetic linear comparison bow? It ends at 50@28. But where do we start it? What is the drawweight at 10" of draw? Why?




 

[superdav95]

Doesn’t that just mean that you have better early draw weight then typical longbow?   That’s a good thing. 

[Badger]

It is usually expressed as stored energy per draw force (sepdf). I see what you are talking about now. You are 120% of a straight longbow, that makes sense, just not what I am used to seeing. At 10 grains per pound I would expect between 184 to 186 from that bow which is excellent. A very well made straight longbow with a straight profile will usually hit about 167 to 170.

[Selfbowman]

What is the brace from back of bow???

[Tuomo]

The draw weight curve should start from brace height, otherwise you don't get meaningful numbers.

[Hamish]

I don't know much about FD curves, but the curves of those limbs look damn cool.

[simk]

The draw weight curve should start from brace height, otherwise you don't get meaningful numbers.

OK, lets  say brace is 6.5". And whats drawweight then at 6.5"? I need a number but cant measure dw at brace.

In virtual bow  I see the graph going towards 0/0.

Then Tuomo, how is that hypothetical linear comparison bow in virtual bow defined? Referring to the "energy storage factor"

I'm still not through with my theory....

Thanks

[superdav95]

Simk.  I think what tuomo was trying to say is that you should show 0 value at 6.5 if that is your brace height. Then every inch from there.  I guess every two inches would be fine too but starting from brace gives the early draw curve which can also be a predictor of good bow with good energy storage.  I’m just basing this on what little I know of force draw cures and the few that I’ve done on my own bows. 

[Tuomo]

Just like “superdav95” said: brace height = 0, and then measure draw weight at every (full) inch. If brace height is 6.5", then measure draw weight at 7", 8", 9", etc., up to 28" or whatever the maximum is.

I will write more about the draw-weight curve, stored energy, and the “energy storage factor” later, when I have more time. There are many things that can go wrong if we don’t define all parameters and issues clearly and exactly. It is interesting topic! And clearly needs more discussion.