Relative performance of different limb designs

[Eric Garza]

A while back there was a thread here where someone offered data on how well certain limb designs perform relative to others. If memory serves the limb designs that were compared were:

• Normal straight flat bow limbs
• Molly or holmie designs with long rigid tips
• Reflexed limbs
• Deflexed handle and reflexed limbs
• Recurves

I've spent a few evenings searching for this thread, and can't seem to find it. My question is: How much performance (as measured by added fps) do you get by transitioning from one limb design to the next, all else being held constant?

[loon]

something about adam karpowicz saying a bow that's straight at brace can do pretty well in flight archery but reflex is more important with heavier arrows? dunno

i guess energy storage matters more for heavy arrows, energy transfer efficiency more important for light arrows ..

[willie]

How much performance (as measured by added fps) do you get by transitioning from one limb design to the next, all else being held constant?

would a difference in early draw be one of the "constants"? I believe that is where some limb designs outshine others.

there was a discussion last winter something like what you are looking for..does searching the posts of joachimM help?

[Badger]

  Loon, that is pretty much correct, high efficiency will start to trump stored energy at some point. As far as with hunting weight arrows go. The differences are surprisingly small. If I throw out top performers and just consider bows that would say get an A for performace as opposed to an a+.

 Normal straight flat bow limbs about 170 I would call an strong A

Mollie Hommie designs about the same 170

Reflexed limbs about 175 is a strong A 172 is more typical for a nice reflexed bow.

Deflex reflex about 178

Recurves about 180

  You can add about 5 fps for laminated bows. I have seen slightly better than this but not often.

[PatM]

 Don't forget reflexed and recurved. 185

[loefflerchuck]

I have been surprised with heavy arrow flight with highly reflexed bighorn bows. Horn limbs are heavy so the cast with light cedar arrows is not too impressive. What is impressive is that much heavier dogwood arrows with broadheads landed only 5-10 yards shorter as apposed to around 40 yards less with strait limbed bows.

[scp]

I recently had a rude awakening. In about 50 unfinished but shootable self-bows I have made in all kinds of styles, even the better ones just hover around 140 FPS and none of them cannot achieve 165 FPS I believe I have achieved 5 years ago. For that matter several beat-up used fiberglass recurves I purchased for comparison just hover around 150 FPS, just one achieving 160. I even doubted the accuracy of my Chrony F1, but it does register over 200 with a couple of compound bows I have.

I know that my shooting technique is terrible, and I can probably add at least 5 or even 10 FPS to my results. I better reassemble my primitive homemade shooting machine and test all my bows again. Is this because I never actually finish my bows? Not sure how much improvement I would get using the heat box and properly finishing up my bows.

Frankly I'm not interested in making flight bows. What I want to do is to make the regular target bows, mainly to get the benefit of physical exercise from the hobby. Still at least 150 FPS on average is expected and 160 FPS for most of bows would be real nice. Does that mean I should be mostly making reflexed recurves?

[Badger]

I recently had a rude awakening. In about 50 unfinished but shootable self-bows I have made in all kinds of styles, even the better ones just hover around 140 FPS and none of them cannot achieve 165 FPS I believe I have achieved 5 years ago. For that matter several beat-up used fiberglass recurves I purchased for comparison just hover around 150 FPS, just one achieving 160. I even doubted the accuracy of my Chrony F1, but it does register over 200 with a couple of compound bows I have.

I know that my shooting technique is terrible, and I can probably add at least 5 or even 10 FPS to my results. I better reassemble my primitive homemade shooting machine and test all my bows again. Is this because I never actually finish my bows? Not sure how much improvement I would get using the heat box and properly finishing up my bows.

Frankly I'm not interested in making flight bows. What I want to do is to make the regular target bows, mainly to get the benefit of physical exercise from the hobby. Still at least 150 FPS on average is expected and 160 FPS for most of bows would be real nice. Does that mean I should be mostly making reflexed recurves?

  Don't get caught up in the numbers. If your bow does not take too much set and the outer limbs are streamline you will have a good shooter. Your shooting technique is just not good for testing bows I bet.

[scp]

Let's get back to the main issue of the relative merits of different limb designs. If I  remember correctly, according to TBB the most important factor is the position of tips relative to the back of the handle, achieved without damaging limb wood.

IMHO the easiest way to do so, if you don't mind the hassle and use of modern glue, is to get a good flat board with proper width and thickness and cut it to the proper pyramid front profile and then just glue siyahs on it without ever bending it to string it. What matters most would be the angle and length of siyahs. This must be a sure way to get "primitive" out of primitive bow making. Sorry about the digression.

What are the important physical factors relevant to bow performance?

[Del the cat]

I think the question is somewhat flawed as there are too many other variables.
The design has to suit the wood you have, the proposed draw weight and length, then there's the actual quality of the build.
I've see Molle's with levers so thick and deep that they were adding weight not saving it.
At a recent roving shoot I saw a Grozer bow, the levers were awful, way too heavy, maybe it was a cheapo model, but it made me wince.
If you are using the wood to it's limit, you may well not be able to recurve it much.
So much also depends on what you want to do with the bow, bring down a deer, shoot 300 yards or throw a 1/4 pound arrow, do you want accuracy or speed. I made a sweet little boo Yew flight bow... took it to a 3D shoot... oh dear, not much fun, I'd have been better off lobbing bricks at the 3Ds

Back to the question:- 
I have a sneaking suspicion that if you had a supply of absolutely identical staves and made bows of each design, the same length to shoot the same arrow same draw weight and draw length, I don't think there would be much difference. 
Heresy heresy! Off to the tower with him!
Del

[Stick Bender]

Some where along the line I saw some test done recurve vs strait limb reflexed design I think it was Tim Baker or one of the tbb crowd but the crux of it applied to self bows was the recurves looked pretty but the strait limb reflexed design performed as well or better then the recurve like was said keeping the string in front of the handle but dont have any exsperience to back that up.

[Marc St Louis]

The more speed you want out of a bow the more work you have to put into it, a large part of that work being mental.

[Eric Garza]

Thanks for the responses. The numbers Steve offered are what I was looking for. I wrote 'em down this time.

[Aaron H]

Steve are those numbers for a standard 50# @ 28"?

[scp]

To put the question in another way, while keeping all other things equal, what would be the best way to make the tips be in front of the back of the handle when the bow is unstrung, without doing any damage to the bow wood in the process?

It appears that finding a naturally reflexed stave will be the best and easiest way. Then all we have to do is to tiller it, without causing any set, and making its working limbs bend nicely and evenly.

Is this kind of simplification worth anything? Not much for the professional craftsmen, but possibly quite a bit for beginners, I guess. Just tiller without causing any set and no positive string follow at all, and possibly cause some negative one if possible. What would be best limb design to achieve such tillering for beginners, or for each individuals?

For me, who is working mostly with green hickory staves, it would be just using a naturally reflexed stave and pyramid front profile with same thickness in all working limbs.