Author Topic: Research help needed. Short bow stats.  (Read 4950 times)

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Offline Prarie Bowyer

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Research help needed. Short bow stats.
« on: January 10, 2012, 04:35:24 am »
Actualy this may be possible to build a predictive equation for bow length and draw weights.  If enough people weigh in with information on their succesful short bows.

I'd need final draw weight, draw length, tip to tip length, wood type, and backing type (structural only).

Offline ken75

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Re: Research help needed. Short bow stats.
« Reply #1 on: January 10, 2012, 04:00:11 pm »
if you look back there is a really long and good post on short bows from last year . lots of people weighed in with the stats and bows

Offline Pat B

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Re: Research help needed. Short bow stats.
« Reply #2 on: January 10, 2012, 04:48:30 pm »
A bow fully drawn is 9/10ths broken! This relates to a bows length being twice it's draw.

Up until recently a short bow to me was 60"t/t. I've made osage and elm bows of this same style, both were static recurves that bent slightly in the handle and both pulling between 55# and 60# and both were pulled to 28". My normal draw is 26" but I like to go over that for insurance.
  My shortest to date for my 26" draw is the 53" sinew backes osage I recently posted. It pulls about 55#@26"(I haven't weighed it lately)
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline MWirwicki

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Re: Research help needed. Short bow stats.
« Reply #3 on: January 10, 2012, 04:55:04 pm »
50" Osage  55@26
48" Osage  60@25
Both sinew backed.  Bulbous handle bending only in the last inch or two of the full draw.
« Last Edit: January 10, 2012, 04:59:00 pm by MWirwicki »
Matt Wirwicki
Owosso, MI

Offline Qwill

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Re: Research help needed. Short bow stats.
« Reply #4 on: January 10, 2012, 05:15:19 pm »
Sinew-backed yew - 40"  50 lbs@26in draw
Serviceberrry flatbow - 56" 45 lbs@28in draw, (with heat treated belly)
Douglas Maple flatbow - 54" 40 lbs@26in draw (this was before I realized Douglas Maple was different from Vine Maple. I'm adding a bamboo backing to see if I can improve this one.)
Juniper flatbow - 54" 50 lbs@26in draw. (This was a character bow with about 1.5in of set. My dad showed it too a guy who immediately drew it 30 in. It held together, but was never quite the same. I gave it to a guy who let me harvest the Juniper as a wall decoration.)

Offline Matt S.

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Re: Research help needed. Short bow stats.
« Reply #5 on: January 10, 2012, 06:31:09 pm »
Just finished my first short bow.
Hickory 52" ntn, just under 53" tt
50#@25", then retillered to 47#@26"
"Insurance" backing of raw silk due to a pin knot.

Offline Ifrit617

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Re: Research help needed. Short bow stats.
« Reply #6 on: January 10, 2012, 07:44:20 pm »
Sinew-backed yew - 40"  50 lbs@26in draw



do you have any pics of this bow? It seems almost impossible for a bow that short to draw that far at a 50 pound weight... I'm not questioning you I'm just interested ...  ;D ;D

Jon

Offline Prarie Bowyer

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Re: Research help needed. Short bow stats.
« Reply #7 on: January 17, 2012, 02:14:08 am »
I haven't lost the thread here.  Just giving time for more data points to build up. Came across this.

http://www.youtube.com/watch?v=Y4RaTQay0hY&feature=g-all-u&context=G2a4451fFAAAAAAAAAAA

So it would be Length- 40" Core -Yew Backing- Sinew Draw weight- 35# draw length-16"

I wonder if he could take it further?

As I started thinking about this I don't know how I'll construct this.  I need a Axis variable.  I don't think I'll get a significant result if I just say tip to tip length. Because that is irrelevant to draw weight, and backing type.  So my error or residuals would be all over the place.  I think this is going to be for gut analysis only.  I don't think a predictive model can be built to give me the length draw weight at some interval of limb length. I'll try, it could be that it will give some useable result because the focus here is the change in draw length and weight as tip to tip distance shrinks but I think the goodness of fit will be shot to heck.

Fun stuff to play with though.  My Sr. year in econometrics I developed a predictive model that accurately predicted real gold prices for two months outside the data set used to build the model (then I stopped following it).  You couldn't use it (that one) to make money in markets.  It required GDP as an input on a monthly basis but it's only reported quarterly so you need to do some statistical math wizarding within the model to get monthly estimates.  In life you'd use the last known figure... which means that your monthly error gets bigger till the next release.  Plus I was dealing with monthly averages of prices.  The real value in themodel was in examining the relationship between SP-500, Oil, gold, GDP, and unemployment trends in a broad sense. A real connection was found and quantified . .  . Duh!  :laugh:

Offline Parnell

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Re: Research help needed. Short bow stats.
« Reply #8 on: January 17, 2012, 10:22:37 am »
Just did a Cheyenne style bow, 47" of HHB, no sinew, side nocks.  48# at 24".  I'm shooting 26-27" arrows from it.  Within 15 yards its consistent but going out to 20 you really have to stop and find your zen.  With more practice I think it could be dependable to 20.  Much past that is taking chance, I think.  It'll post sometime. 
1’—>1’

Offline Slackbunny

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Re: Research help needed. Short bow stats.
« Reply #9 on: January 17, 2012, 11:00:01 am »
Do you know how to construct a contour graph? Its a way of plotting more than 2 dimensions on one graph without actually having to draw more than 2 dimensions. The downside is you have to hold your main variable constant for the graph, so it takes multiple graphs to cover multiple values of your main variable.

I see these a lot, in school. I'm taking mechanical engineering, and these pop up all the time, especially in fluid mechanics. These graphs take a lot of data, and a lot of work to produce though, so it would be quite a commitment to formulate them. I can't see them being all that accurate anyway, since there are more variables at work that you had listed. For instance no two staves of the same wood are identical, so even if you had two bows with the same dimensions and wood there would still be a relatively large margin of error.

You would need to include in the model all the dimensions of the bow including all angles of reflex/deflex and taper angles, you would need to quantify the grade of the wood to account for differences between two staves of the same species, and then there is the problem of accounting for defects like knots which you may have had to work around. And even after all this it may not be applicable to the so-called character bows.

All this being said, you probably could generate a model that could roughly predict what you want, but it would be rough estimations at best. 

Offline Prarie Bowyer

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Re: Research help needed. Short bow stats.
« Reply #10 on: January 17, 2012, 01:57:35 pm »
Yea I was thinking of some of this.  I didn't pan on gettign that particular with the model.  I need a fixed variable in the Y.  Like I think Maybee if I include limb width  it might help.  Then I set up Length = limb width + draw weight+draw length+backing type + wood type+ design (recure etc).  As bows get shorter one way to spread the force is to spread it across the limb.. so in that way there is SOME connection to length.

But mostly I think the model won't give much.  Still it could be fun to try.

Offline Dean Marlow

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Re: Research help needed. Short bow stats.
« Reply #11 on: January 17, 2012, 02:39:37 pm »
Getting ready to sinew a 58" osage bow with static recurves and a reflexed handle. It is 50lbs at 28" right now. It was a premium piece of Osage though. Dean

Offline gstoneberg

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Re: Research help needed. Short bow stats.
« Reply #12 on: January 17, 2012, 03:09:53 pm »
I'm curious Dean, if you're already at 28" why are you sinew backing, added protection?

This is a very interesting thread.  My last bow is sinew backed osage, 50" n2n, 7/8" wide, 55lbs@27", 60lbs@28".

George
St Paul, TX

Offline Qwill

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Re: Research help needed. Short bow stats.
« Reply #13 on: January 17, 2012, 03:21:55 pm »
Sinew-backed yew - 40"  50 lbs@26in draw



do you have any pics of this bow? It seems almost impossible for a bow that short to draw that far at a 50 pound weight... I'm not questioning you I'm just interested ...  ;D ;D

Jon

I do not have any photos. I never finished it with a skin backing, and then one of my brother's left the bow in the garage where the dogs could get it. They ate the sinew off.  I'm quoting that draw length from memory,  it may have been 24 inch, but was not less than that. I did heat treat the belly, which improved it quite a bit. I did the heat treating before I put the sinew on the bow. I started with 3 inches of reflex, and after shooting in, I had 0 set and 0 reflex.