Bow design article

[PatM]

Here's a bow design article by Dick Baugh that stunned the Paleoplanet crowd into silence.
 Thoughts?
http://paleoplanet69529.yuku.com/topic/61607/Stickbow-Design-Rules

[Eric Garza]

Thanks for posting this. I don't think the article stunned the PP crowd into silence. Those forums have been all but dead for months. Not sure why though.

I have to say I feel a bit put off by Baugh's confrontational tone. The information he provided from his computer simulations was interesting though, albeit not particularly earth shattering. One can probably sum it up as following:

• Design bows with long, rigid handles
• Make most of the rest of the limbs bend
• Make tips narrow and light

 

[RyanY]

I think Dick's interpretation of the Mantra was incorrect and some of his claims of bow design are detached from reality. His first assumption that the Mantra bow's inner limbs are stiff is completely different than the actual meaning of making them wider for low set and less strain. We do this because this is where the bow can afford extra mass for less set and where set would be the most detrimental. The extra strain mid limb for a little set is ideal and here's why. Set is the tool we use to assess strain in real world bows. Mass becomes a significant factor as we move away from the handle to mid limb and thus set shows us that this part of the limb is being strained somewhat for lowest mass. His claim of Mantra bowyer's make outer limbs thicker and heavier to reduce speed is outrageous. Obviously its meant that they are made narrow and, although thicker, have far less mass than normal bending tips. The mantra also includes the idea of getting these stiff outer limbs bending slightly for lowest possible mass. I think where he truly loses touch is his comparison of bows where the width at the riser fixed with increasing riser length. His computer model shows that the long riser bows perform better because "you are making the outer part of the limbs store more energy per unit mass and work harder." Unless there's some magic going on here, I don't know of any way you can simply make wood store more energy per unit mass just by changing dimensions. Surely attempting to do so would make firewood.

[PatM]

 The interesting thing is that Tim and Dick apparently corresponded regularly so it seems odd that these ideas are presented now.

[SLIMBOB]

Interesting read.  I too agree with ryoon's assessment.  The mantra did not recommend making tips narrow and "heavy" but instead narrow and "light".  Something I struggle to achieve personally, but that has always been the goal.  Food for thought in lot's of ways.

[blackhawk]

Computers don't lie or make errors....but humans do,and when erroneous numbers are input computer models won't tell you the whole truth. Its easy to prove lever bows are slower than a normal flatbow and vice versa....all ya gotta do is put in garbage numbers and voilą,you can prove anything ya want. Its clear that he input grave errors for his molly computer model bow by making the tips 50% thicker than the near riser wood. This is WAAAAAAAAAAAAAAAY OFF!!!! Ive made and tested so many of these type bows to know. I always check with calipers when I'm done,and in always weigh the bow before and after my tip reduction before I'm ready to start shooting the bow in. His numbers will give this bows tips an ounce heavier in each tip totalling 2 more ounces in the bows total mass. And when bows are weighed in ounces,and having these ounces out in the tips where its most detrimental is HUGE!!!! There's a big difference. So his results and conclusions aren't quite right because of one input mistake. So he's half right and half wrong.

Funny thing is: is that he's basically saying the same thing as what Tim preached. If made correctly its the same dang thing. And like Ryan said he's just misinterpreted what a mantra bow is. Its not jus one style and design bow....its to be applied to ALL types and designs.

[Buckeye Guy]

My thoughts too Chris
Garbage ii garbage out
He even says easier to comp. model than to measure , so if its hard to measure how do you get good numbers to program the computer with to start the modeling
 
The only thing I need to know about a computer is How to get on PA's forums . 
I am done
you folks go ahead

[Badger]

  Two things that are very hard to pin down when accounting for looses in bow efficiency are limb distorsion ( vibration) and histerisis. A computer model could esily and more accurately predict best designs for energy storage, it could also accurately predict where the strains were greatest. The relationship between momentum and mass in the limbs and distorsion I doubt we could ever give enough good input to ever get meaningful output. I am convinced that the shorter the area of working limb th less potential for vibration and distortion. This also puts more stresses on the bow and aggravates the histerisis. I doubt computer modeling alone could ever produce anything of great value but I do believe it to be a potential useful tool when working out theory. Personally I can't make heads or tails out of it but those who can will likley put it to good use.

[George Tsoukalas]

That was a very interesting article.

Some comments:

-To me there is a lot of difference between staves of the same species. Finding osage staves with the same properties is probably impossible.

-I've always fit the design to the stave. I don't pay attention to mantras or computer models. If it is too wide to bend I narrow it. Bending starts at the end of the fades and increases outward.

-Mr Baugh seems to favor the Holmie design. Doesn't that have wide inner limbs?

-As ryoon pointed out he doesn't seem to fully understand the mantra bow. He seems to think it is a whip tillered bow.

-Only 2 of the bows in his a-e examples have the same weights. Different weights, different materials and one material ?.

-What model? Did he write a program? Did he know what the model would yield before he wrote it which would make it suspect. He just states the computer will be used. I'm using the computer right now to write my gibberish. LOL.

- The actual test of his model is for him or anyone  to build an osage bow that shoots 185 fps at 28". Straight up. No reflexing or heat treating. Draw length independently verified.

-Mr Baugh  fails to mention that hard science is done through controlled experimentation...one experiment building upon the other. That is, for example, Einstein's speed of light has been experimentally verified. Newton's Laws have been experimentally verified, as well.

In short, show me...just don't tell me.

Jawge

[JoJoDapyro]

Garbage in, garbage out. I maintain a database for work work orders for the city I work for. My biggest complaint is that people leave off little things because they are little. Incomplete or flawed data makes everything wrong. Why bother using information that isn't 100% correct? 

[Dan Perry]

Paleo P. is down right now, so I wasn't able to read the post talked about here.

I was curious, as I have studied and sold bows with extended non working center sections, back in the 80's. I shared the idea with Tim back before TBBIII came out. Is that what this was talking about? Because the narrow, short working outer limbs idea is one I have experimented with in the past. The sorter working tips may have less deformation "what some call vibration" but the bows break down faster and lose their performance fairly fast, in my experiments. Low mass tips, with longer overall length from the stiff center section, keeping the string angle of a shorter stiffer tipped bow, make them a little faster than some designs for flight, but it is far from the fastest design for flight. Actually the reverse, like a Holmie, did better for me as well.

When I extended the limbs farther apart with a stiff center section, I put traditional working limbs from the beginning of the working limb to the tip.
Tip third was a little stiffer in tiller.