Hornbow force/draw curves for Sleek

[bownarra]

Sleek your inbox is full....so I though i'd put these here for you. For everybody else these are the force/draw numbers for a couple of my hornbows.
Thanks for the reminder! Finally got around to it for you.
This bow is that red/black one.
10" - 11.5
11" - 15
12" - 19
13" - 21
14" - 25
15" - 27
16" - 30
17" - 32
18" - 35
19" - 37.5
20" - 40
21" - 42.5
22" - 45
23" - 47.5
24" - 50
25" - 53
26" - 56
27" - 59
28" - 62

This bow is a Turkish design, i've posted it before I think, blue and black decoration, 48".
8" - 10.5
9" - 17.5
10" - 22.6
11" - 26.8
12" - 31.1
13" - 34
14" - 35.9
15" - 37.7
16" - 39.2
17" - 40.8
18" - 42.9
19" - 44.9
20" - 47
21" - 48.9
22" - 50.8
23" - 53
24" - 56.5
25" - 60.1
26" - 63
27" - 68
28" - 72

Hope this helps The first bows graph is interesting and the Turkish bow shows the normal characteristics of Turk warbows.

[sleek]

Thanks VERY much, it will help me a lot!

[sleek]

That first one is like its a flight if stairs lol. How strange. Could you tell me what speeds do you get on them with what arrow weights?

[sleek]

So that Turkish bow, its energy storage is phenomenal by wood bow standards. If you don't already have speeds and arrow stats on that bow, id really like them.

The First bow as well if its not too much trouble.

[bownarra]

No problem, I will try and get a few shots over the chrono with them. It's been snowing here for a while now, will have to wait for a break in it.

[Tuomo]

Thank you!

Could you please link to topics, where these bows are, just to be sure.

After calculating these bows store about 126 % of energy compared to theoretical straight and linear force draw curve. Basic, straight wooden bow stores about 105 % of energy compared to straight and linear draw force curve. So, this kind of horn bow stores about 20 % more energy than straight wooden bow.

[sleek]

Thank you!

Could you please link to topics, where these bows are, just to be sure.

After calculating these bows store about 126 % of energy compared to theoretical straight and linear force draw curve. Basic, straight wooden bow stores about 105 % of energy compared to straight and linear draw force curve. So, this kind of horn bow stores about 20 % more energy than straight wooden bow.

How did you calculate that?

[Tuomo]

Stored energy is area under the draw force curve, so very simple.

[sleek]

Stored energy is area under the draw force curve, so very simple.

I know what it is, im asking how you did it  because I got different answers.

[Tuomo]

Oh, sorry... And thanks for asking, I found a minor mistake from straight draw force calculations (I had wrong brace height... and brace height is really important parameter).

I suppose that brace height was 9 inch for the first bow and 7 inch for the second bow.

Then,

first bow: stored energy 76,6 J (straight draw force curve 66,6 J).
second bow: stored energy 98,0 J (straight draw force curve 85,4 J).

I calculated the stored energy with Excel and numerical integration using so called "Trapezoid rule".

So, these horn bows stores about 15 % more energy compared to straight draw force curve bow. And, basic, straight wooden bow stores about 5 % more energy compared to straight draw force curve. So, these horn bows stores about 10 % energy than straight wooden bow.

Summary:
-Straight, linear draw force (perfectly straight) stores 100 % of energy (we compare other bows to this, so that is why I use 100 %). We could also use for example value 0,5, because it stores half of the theoretical maximum of stored energy.
-These horn bows stores 115 % of energy compared to straight draw force curve.
-Straight wooden bows stores on average 105 % of energy compared to straight draw force curve.

Hopefully I am not too confusing...

[bownarra]

Brace heights are 6 1/2 for the Turkish bow and the the other is braced at around 8 "

[sleek]

For the second bow I got 93.45 joules, storing 95.74% of its drawn energy. Straight curve bows do give close enough to 100% so no arguments there. But I see this bow is 5% under the energy storage of a linear curve, not over it.
 Your numbers seem high. I added up all the numbers, to get inch pounds, then divided by 12 to get foot pounds to compare directly to his draw weight. I think perhaps a conversion discrepancy to joules may have contributed to an error for you?

[Tuomo]

For the second bow I got 93.45 joules, storing 95.74% of its drawn energy. Straight curve bows do give close enough to 100% so no arguments there. But I see this bow is 5% under the energy storage of a linear curve, not over it.
 Your numbers seem high. I added up all the numbers, to get inch pounds, then divided by 12 to get foot pounds to compare directly to his draw weight. I think perhaps a conversion discrepancy to joules may have contributed to an error for you?

I am not sure if I understand what you mean. I think that it is the US way to compare stored energy to bow's maximum draw weight, which is a bit vague way.

You get straight draw force "curve", when you draw straight line from zero to maximum draw weight. When compared to this "curve", these horn bows have much fatter curves. Straight draw force "curve" is very close to real straight bow's draw force curve, so that is why I compare other bow's stored energy to that. So, I define that straight draw force "curve" means 100 % or 0,5 or 1,0 or whatever, it is just a relative value to which I compare other values. I think that you compare stored energy to bow's maximum draw weight. And I do not understand, how it is meaningful to compare different units (joules to newtons, if using SI-units, or foot-pounds to pounds, if using imperial units). And, that is why I get readings like 110 %, because these horn bow stores more energy than straight bow to which I compare these horn bows.

Great bows, would like to try them, so maybe I have to make some! I have made just one Turkish horn bow, so not much experience yet. But measuring (and calculating...) is always fun!

[sleek]

We compare how much energy is stored in a bow to the draw weight of the bow to determine how efficient the bow is at storing the energy we put into the bow by drawing it back. Its important because a bow that stores more energy compared to its draw weight has the potential to be a higher performance bow. The last half if that being it needs to also deliver its stored energy into its arrow as efficiently as possible as well. Both of those require knowing the ratio or the percentage ( your preference ) of the bows drawn weight to its stored energy.

I dont understand how you are doing it, or what information you gather thats valuable to you if you don't do it for comparison to the bows draw weight. Can you elaborate on your method and why?

[Tuomo]

I got it. I am just comparing the stored energy to some kind of reference value, as you are also doing. You compare stored energy to bow's draw weight (SE/PDF), I compare it to stored energy under straight and linear draw force "curve" (then the stored energy is half of the theoretical maximum value). From the reference value it is easy to see, if the bow stores more or less energy than normal straight bow - the maximum draw weight does not matter. Of course, stored energy as joules is needed for efficiency calculations. So, stored energy can be presented as a reference value (percentage) or real value (joules).

I know that the reference value may be a bit confusing but it is still quite obvious when you are used to it.