Primitive Archer
Main Discussion Area => Bows => Topic started by: Wooden Spring on September 10, 2015, 10:49:01 am
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So, my copy of "Archery The Technical Side" just came in, and in a 1932 article by Paul E. Klopsteg, he gives his research for what he calls a "high efficiency, rectangular section bow." He goes on to say: "Reviewing the characteristics of the new type of bow, we may recall that its limbs bend in true circular arcs, with uniform stress throughout; that the limbs return from the drawn to the braced position in shorter time than do the limbs of any other shape about which we have information; that there is less wood in the limbs than in a corresponding bow of conventional limb section. The fiber stresses, i.e., the tensile and compressive forces to which the limbs are subjected, in a given weight bow of the new form, are less than in a corresponding bow of the conventional type, which permits the new bow to be made shorter if the archer wishes to have it so."
Also interesting to note were the experiments done to prove that narrow, light nocks are no faster than heavy, fat nocks. There were no appreciable differences in arrow velocity by having narrow, light nocks. (gasp! blasphemy!)
The book goes on to use math to prove the point, but I wanted to put this out there for review by those who know a LOT more about bows than I do. What's your practical experience with a bow like this?
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This is a basic pyramid design if I read it correctly isn't it?
OneBow
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This is a basic pyramid design if I read it correctly isn't it?
OneBow
Pretty much, yeah. The only difference from the traditional pyramid design that I'm familiar with is:
1) the length. This bow's limbs are around 3' long each. Most of us build limbs around 30" long
2) the tips. The tips on this bow are parallel, at around 1/2" wide. The limbs actually come to a point at the nock, and the parallel tips intersect the limbs at around 8-10" down the limb.
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Asymmetrical too....
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Asymmetrical too....
Yeah, I noticed that. I've never built an asymmetrical bow before... I have a hard enough time balancing out limbs that are supposed to be EQUAL!! ::)
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I think it's a good design, pretty basic really. And I think it's quite attractive when the width isn't super high near the handle.
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Pyramid bows should have circular tillers. Most of the bending should happen where most of the wood is to decrease set. So yes the limbs would return faster in a well constructed bow.
In a Meare Heath, style bow, the tiller should be elliptical.
I do not have the book. I am wondering if he compared the 2 styles.
In my experience, narrowing the last ) inces or so and trimming the nicks helps with speed.
Jawge
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Any comments on the length of the bow? The upper, longest limb is nearly 3 feet long...
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One thing I have always found interesting is that their doesn't seem to be a nickels worth of difference in the designs if they are properly executed. I may have designs that work better for me but someone else may have one that works for them. If you are just talking straight bows I find about 170 fps plus or minus a little is about as good as it gets, some exceptions of course. I have seen nearly every design you can imagine hit that number, including bendy handle flat longbows and elbs. I do believe narrowing the tips can add some speed. I don't narrow mine anywhere near what I used to simply because I am willing to give up one or two fps for some durability if I bup to bow on something.
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OK, so let's see what the bow looks like when properly proportioned. For these drawings, the bow is symmetrical.
On the far right, we have the bow as described in the original layout, 1-5/8" wide, tapering to a point at the location of the nocks. The 1/2" wide nocks are parallel, and intersect the bow limb about 10" down. The bow is 78" long, NTN.
In the middle, the bow is kept at 78" long, but the parallel nock is this time drawn at the minimum 8" long. In order to do this, an angle is first drawn from the nock to a point 8" down and 1/4" out. This line is then projected back along the length of the bow. Where the projected line continues back along the limb, a section of parallel limb is required to maintain the nock length.
On the left is the same principle as the previous bow, but at 68" NTN.
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Looks like a stretched out Andaman-holmeggard style bow
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Surely the yew / lemonwood LL is a misprint. A lower limb 4 foot 7 inches long...
Looking at the osage dimensions I'd say it was meant to be 35"
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Surely the yew / lemonwood LL is a misprint. A lower limb 4 foot 7 inches long...
Looking at the osage dimensions I'd say it was meant to be 35"
Yeah, that has GOT to be the case, "35" instead of "55." Hence the existence of future printings. This was a first printing in 1947, so I'm sure that got fixed.
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Those bows look a lot like Tims mojam bow.
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Steve the pecan bow? I will be trying some of these designs with a Arvin twist. They look efficient to me.
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I thought Tim's bow was much more willow leaf shaped in the limbs.
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Tim called it the Eifel tower I think.
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ive made semi bend through the handle bows like in your picture. they were short but very powerful. and i didnt always tiller them flat either. tried to match the natural curve of the back ring with the tiller on the belly. for a short powerful bow thats my favorite style for osage or locust.Tony
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All my drawings of bows work perfectly >:D
Del
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All my drawings of bows work perfectly >:D
Del
All species of Human-kind are inferior to the Brits in one clear regard if none other, ...this being the innate aptitude for dry and sometimes biting witticisms.
OneBow
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Brits....cough splutter......English,Scottish,Irish or Welsh are the correct terms! Not of us call ourselves Brits..... ;)
I do agree with your sentiment though!!
I agree with Badger once you get a straight bow design wired they all shoot about the same. Pyramids are easier to achieve this with in my opinion. Easier to judge tiller. Engineering-wise they do have a point. 170fps is what you should aim for with a straight selfbow. I've had my laminate elbs scrape 180fps. A couple of recurves have made 185fps.
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I agree with Badger once you get a straight bow design wired they all shoot about the same. Pyramids are easier to achieve this with in my opinion. Easier to judge tiller. Engineering-wise they do have a point. 170fps is what you should aim for with a straight selfbow. I've had my laminate elbs scrape 180fps. A couple of recurves have made 185fps.
Is this with a 10 gpp arrow?
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Anyone know what the fastest wooden bows ever measured were? Lam and selfbows separately.And maybe *****glass too.
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DC, I have measured my fastest at 188 fps, Mark St Louis bow I measured at 190 fps I believe with 10 grains. These are backed bows. fastest self bow I have measured is 184 which was mine and a bow of Marks at about the same. How a bow is tested and what type of string it has all make a big difference so accurate testing is really hard to come by. I tested an experimental bow a few months back that cracked the 200 mark but within a dozen shots it had broken down to about 157. Unless a bow is actually tested through a machine using identical strings and strictly measured arrow weights and bow weights test results cannot be taken as gospel.
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Thanks Steve. I wasn't really after accurate figures. I just wanted ballpark figures. Have you ever heard(rumours) of any in the 225 or 250 range or is that compound area?
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Shooting light arrows I have a bow right now that will hit 300 fps. That same bow shooting 10 grains per pound shoots in the low 170's. I think a few modern recurves may be exceeding 200 fps at 10 grins per pound but to my knowledge no modern long bows or primitive bows have gotten there yet. A few modern longbows have hit the 200fps but didn't last long enough to be considered a viable design. I think they will get there before too long.
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Klopsteag notes elsewhere in the text that since the limb tips are parallel for a ways, some of that length needs to taper in thickness, unlike the main part of the limbs. He also points out that the tips should never be narrower than their thickness.
"Pyramid" bows are addictive. Once a person sees how they are nearly tillered as soon as they are sawn out, it begins to seem like that's the only sensible way to make a bow. I have made nothing but pyramid bows for the last 15 years. I have no interest in any other design.
Jim Davis
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Klopsteag notes elsewhere in the text that since the limb tips are parallel for a ways, some of that length needs to taper in thickness, unlike the main part of the limbs. He also points out that the tips should never be narrower than their thickness.
"Pyramid" bows are addictive. Once a person sees how they are nearly tillered as soon as they are sawn out, it begins to seem like that's the only sensible way to make a bow. I have made nothing but pyramid bows for the last 15 years. I have no interest in any other design.
Jim Davis
Most people can nearly have a bow tillered after it is roughed out anyway once they have made a few bows.
The concept of easier doesn't generally cross the mind of most wood bowyers.
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I am sure pyramid bows are a good design,,I like Native style bows and havent made a pyramid bow in 20 years,, you can glue a fiberglass bow up and it is tillered,,I like to carve a bow from a stave and enjoy the variation,,I know I am not sensible,,, hope to never be :)
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I'm with Bradsmith, pyramid bows are great but I find them ugly. I prefer narrower bows like the AFL or Eastern Woodland.
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I'm with Bradsmith, pyramid bows are great but I find them ugly. I prefer narrower bows like the AFL or Eastern Woodland.
Pyramid bows don't have to be wide if made of Osage or yew.