Performance - recurve VS. modern longbow

[Lee Robinson .]

In another post someone mentioned that the recurve has better performance over the longbow. I was not offended by the statement, but I wanted to make a post that addresses my views on this. While at one time that was true, with today's materials I just don't believe that really is the case anymore. With modern materials, the performance gap between the recurve and longbow has been reduced and/or nullified completely. Some of the fastest traditional bows on the market today are indeed well designed modern longbows that are able to utilize modern materials.

With carbon and better glues we are able to close the performance gap between longbows and recurves. Carbon is best utilized on the back of the bow (under thin glass) where it works as a superior tension strength material. In a longbow, where the core is deeper, the carbon has a greater impact on efficiency than it does in a recurve...as it is further from the sheer point (center) of the limb core and therefore does more work. Also, with better glues, we are able to come up with more efficient longbow designs that store more energy.

Check out this video. Ideally, everything would be the same in the comparison, but I just didn't have a "match" set of bows to work with, so here is what I was able to put together. There are a few "less than perfect" things I will point out.

1. The recurve is 4# heavier in draw weight than the longbow, giving a slight advantage to the recurve.
2. The longbow has carbon on the backside (but under 0.030" clear glass and 0.030" bocote veneer. The core of the longbow is edge grain red elm. Ideally the carbon would be directly under the back glass, but it is my daughter's bow and we wanted it to be something she enjoyed looking at, so we used the bocote veneers. The recurve does not have carbon. This would give some advantage to the longbow.
3. The lengths are close, but not identical. The recurve is a 52" bow (a very nice copy of the well known Bear Kodiak Magnum), while the longbow is a 50" Protege Little Hunter (it is actually 49.5" NTN). No real advantage for either.
4. The recurve has an 18" riser while the longbow has an 11" riser, giving an advantage to the recurve.
5. The arrow is 357 grains...which is 13.7 gpp for the longbow and 11.9 gpp for the recurve...giving an advantage to the recurve.
6. Both bows have dynaflight97 bowstrings with the same strand count (9 strands given the light weight of these bows). The recurve has beaver silencers and the longbow has yarn silencers). No real significant difference here...but MAYBE a SLIGHT advantage to the longbow on the silencers if we get really nit picky on every detail.

Other things I notice include...

A. Her 2nd shot (148 fps) with the longbow was a bit overdrawn in comparison to the recurve shots (the longbow is easier for her to draw being 4# lighter)...but we throw that shot out.

B. For the same reason, I will throw her last shot with the recurve out, as it was drawn short (she told me she was getting tired when we were done, as she shot more times than this but due to lighting issues we were getting a lot of errors and had to redo the process a few times before getting several good readings in a row).

Despite this...the average fps for each bow at a ~24.5" draw would be.

Longbow - 25#@24.5" at 13.7 gpp = average of 142.3 fps (after throwing out the faster overdrawn shot...averaging the 3 shots of 141.9, 142.9, & 142.0. There were no noticeably "slow" shots to throw out).

Recurve - 29#@24.5" at 11.9 gpp = average of 143.8 fps (after throwing out the high and low shots...averaging the 3 shots of 142.3, 145.5, & 143.5).

The result...even though the recurve is 4# heavier than the longbow and was shooting 1.8 less gpp, it wasn't even 2 fps faster than the longbow. The bottom line in MY OPINION is shoot what you like...and what you can hit with.

Click the link to watch the video illustrating a performance comparison between a modern longbow and a well known recurve...  

I hope you enjoy the video. Thanks for watching.

Lee Robinson

[Lee Robinson .]

BTW, given the low speeds...please take into consideration both the draw weight and the draw length of these shots. Most of us shoot about twice that weight and draw about 3-4 more inches...which makes a big difference.

This was simply the only recurve I had on hand.

[Stoutstuff]

Great information!

[Night Wing]

Lee,

I love "detailed info" and your post contained lots of it. One thing was missing, the brace height for each bow. Do both bows have the same brace height? Brace height should affect arrow speed with regards to feet per second.

[Lee Robinson .]

This is a good point in some regards and not a good point (IMO) in other regards. When I compare one bow's performance to another bow's performance I try to match things up equally in all regards except brace height. As one can see above, I was not able to do this in all regards, but that was the best match I had. When it comes to brace height though, honestly, I don't think the brace height should be altered to "equalize" things. Instead, I think each bow should be set up with the brace height that the bow is designed to be shot with. That, in my opinion, is the best way to compare them...as that is how the bows will be shot in the field and therefore that is the most "equal" method. This is of course just my opinion, but that opinion is based upon optimal tuning of each bow. Generally, recurves have a higher brace height than a longbow. Of course, I should have mentioned this in the video though...so thanks for pointing that out.

Now, that said, there was about an inch difference in brace height. The recurve is set at 7.5" and the longbow is set at 6.5."

Additionally, you may notice the tight nock fit of the arrows on the string. While my own bows are not so tight, I do think it is best for youth and inexperienced archers to have a fit tight enough to prevent dry fires. This does create some noise, but IMO until they become more experienced it is best to deal with that as it prevents accidents.

[overbo]

I would question,how much of the recurve tip is actually working at a 24.5'' draw?Being a copy of a adult bow.I would think the design would be more efficent at a draw legnth closer to 28''.
If modern materails can improve longbow performance.Why can't it do the same for a recurve?

[RLA]

Very good points Overbo, I was thinking the same thing!

[Lee Robinson .]

They will improve the recurve as well...absolutely.

But, being the longbow generally has more total core I believe modern materials have made a bigger impact on the longbow's performance than they have in the recurve...for as one get's further from the sheer point of the core, the more pronounced the improvements in tension and compression forces become. As a result of newer materials and better understanding of limb designs and then reversing the trapazoid cross section, many of today's modern r/d longbows are now able to use designs that get the same pull weight with less core than they needed in the past (but still more than most recurves) which has resulted in a lighter limb in the longbow (when compared to older designs). This also has resulted in a smoother draw than the older longbows which means more stored energy...as these bows tend to put more work closer to the fade out as is done with a recurve or even static design bow, but without having to put more mass at the tips.

At least that is my belief anyway. Maybe I am wrong as to "WHY" the longbow has closed the gap, but that theory holds the most water for MY OPINION and experiences...and one can see that some of the better r/d longbow today are indeed keeping up with the recurves today much more so than they were just 10 or 20 years ago.

[Sixby]

Modern materials do more to enhance the performance of the longbow design than they do the recurve. Recurve limbs are inherently lighter to begin with than longbow limbs are. They are much thinner and therefor carbon and or addition of foam core does not improve the speed of the recurve limb nearly as much as it does the longbow limb. The thinner recurve limb has to have special treatment with a bias carbon instead of the linial laid up carbon we can use in longbow limbs. If not then you lose too much stability in the recurve as the limb gets too thin. A 45 degree layup or 90 degree layup works but then does not add the dame degree of performance a linial layup adds. Everything is a give and take so we have to make judgment calls to work to the plus side.
I certainly do agree on questioning whether the recurve in this test is working the limb properly. The test would be cleaner if both bow designs were being drawn 28 inches or if we knew both were designed to draw and work at a lower draw length.
 

God bless you All, Steve

[KyStickbow]

I enjoyed the comparison...thanks for sharing!!

[copperhead95]

pretty cool, i have seen that modern r/d longbows are basically the same as recurves when shooting them

[LONGSTYKES]

Lee, Good video. Not much difference in modern Bows. Thanks

[Sixby]

D and rs do retain string angle better than a longbow but not nearly as well as a good recurve and not even close to a static. Static recurves are so sweet and you haven't lived until you pull a 62 or 64 in static curve. They are unbelieveably smooth pulling.

God bless you all, Steve

[Lee Robinson .]

Thanks. It was my pleasure to produce the video. I look forward to more tests in the future with the adult bows.

Sixby, I find the statics to be very nice bows in many regards. The only reason I personally haven't pursued them either as a customer or a bowyer is because I have GENERALLY (please note I am talking about generalities here and I am not referring to all of them) found them to be more sensitive by design to form issues (specifically torque) and more prone to limb twist...and require more awareness of care during both use and even during storage. I know of a few that were made by a very well known and highly respected bowyer that have actually delaminated when due to excess twisting in the hard curve used in the static design. I don't use a bow for a walking stick on purpose, but climbing a river mud bank or something I don't have to be concerned about a longbow regardless of if I am carrying it or if I have to toss it up the enbankment...and I like that type of durability.

Of course, a well designed static limb bow can certainly be very smooth, store a great deal of energy, and be very efficient. I haven't studied flight records, so I am curious how well have they done performance wise when compared to full working recurves or the Adcock r/d longbow?

Since I brought up the Adcock cross section bow...I would like to mention that I believe a reverse trapazoided cross section with a carbon on the back can accomplish much of the same beam strength:limb mass ratio but do so with more limb stability.

[Sixby]

You brought it up. I was building Adcock cross section limbs way before Adcock came out with them. My first set of forms i was using a rubber liner on the form. I was also suing high pressure on my hose and the space was a little deep. Guess what,. Adcock cross section. Accidently but non the less just as effective.Trouble was it took me a long time to figure out why those bows were so hot. LOL.

I agree on the trap. Trapping to the back with carbon and deep core narrow limb is not a bad way to go. Its a formula that produces an extremely stable, light , fast limb. May be something there in aerodynamics too. Not sure how much wind resistance enters into it but it has to to some degree.
God bless you all, Steve
God bless you all, Steve

[LimBender]

Similar to what you guys were saying, I previously found a page on Morrison's site that said carbon/foam produced greater increases in efficiency (a/k/a speed) in his testing with longbows than recurves.  Not sure if the page is still there or only on google.

But there always seems to be a variable that throws simple comparisons out of whack as there is a lot of variation in riser and limb design.  One extra consideration is some carbon and foam limbs are more rigid and allow for more pre-loading of limbs.  Some may not like that kind of draw, but it stores more energy, and is one more thing to think about in all of this.

Appreciate the testing Lee.  I think it's safe to say hybrid longbows are closing the gap with recurves, but whether as a general rule hybrid lbs will ever completely close the gap may be an open question.

[Sixby]

This kind of discussion I love. Since most of us believe that recurves are the fastest I just wonder how many and which ones will shoot over 200 fps with a 10 gpp arrow drawn by machine and shot with a mechanical release.
I know at least three D and R longbows that will do that. Centaur, Sasquatch and Ken Rolloffs Whippenstick. I don't know of any recurves that will do that. Perhaps you do. If so let us know . I would really like to know if any will beat those hot D and Rs shooting 10 gppound arrows.

God bless you all, Steve

[jhg]

Originally posted by Sixby:
 ...Trapping to the back with carbon and deep core narrow limb is not a bad way to go. Its a formula that produces an extremely stable, light , fast limb. May be something there in aerodynamics too. Not sure how much wind resistance enters into it but it has to to some degree.

It makes sense strictly on a weight vs power equation, even without the core materials adding performance, since trapping to the back removes weight without a power penalty. Bows get their power from the compression side of the limb, not  the tension side, as I understand it.
Foam makes the limb even lighter, while the carbon gives it back the needed torsional strength, without adding weight, right?

J-

[Lee Robinson .]

jhg,

Tension strengths are generally higher than are compression strength when it comes to the modern materials used in laminated bows. I am not a self bowyer, but I believe the standard trapazoid method with older self bows came about because the back of a self bow was prone to split/lift, which resulted in failure. I suspect self bowyers generally rounded the belly and used a wider back to spread the tension over a wider area...as that would reduce the stress on the back and I imagine helped to prevent the backing from lifting. Since the D shape cross section/trapazoid was done for centuries that way, I believe this remained the standard trapazoid method for a long time...and people just didn't consider changing when new materials (that didn't lift) and better glues (that didn't slip) were produced.

Since a bow works by producing tension and compression, it should be noted that these forces will equal one another in any given bow regardless of how we shape a cross section. ("For every action there is an equal and opposite reaction that occurs at the same time," Issac Newton). With today's materials, we don't have to follow old rules. Fiberglass and carbon have very high tension strengths...and they obviously don't have grain that lifts...so we are now able to reverse the trapazoid cross section to capitalize on this tension strength by narrowing the back to stress this stronger material at a greater level. This results in less mass producing the same pull weight, enabling us to PULL OUT the extreme tension strengths of modern materials. Narrowing the back of the bow concentrates the tension forces and allows us to capitalize on the efficiency of these materials.

With tension strengths of carbon and fiberglass being greater than the compression strengths, I believe it is best to reverse the trapazoid in such a manner that the tension/compression forces are distributed in the materials at proportions equal to their strengths.

For example...say we were going to use material X on both the back and the belly of a bow...and let's say it has a tension strength of 10 units and a compression strength of 8 units...then I would want the back to be somewhere in the ballpark of ~8/10ths the width of the belly...so the back would have the same gross strength as the belly in order to optimally produce a dynamic balance of tension and compression with close to the lightest limb possible.

In summary, I go back to the old statement that a chain is only as strong as its weakest link. (With today's materials...with the tension being stronger than compression, we don't need a backing as wide as the belly (or wider). When we use a traditional trapazoid, the sheer point (neutral zone) moves closer to the back...which causes an overload of stress on the weaker compression forces on a narrower belly...so I believe that is the wrong way to trap a limb (again if we are using glass laminates). Instead, I believe it we need to strengthen the weak link...widen the belly...so I believe the belly should be the wider of the two.

[hybridbow hunter]

I tested myself my "modern longbows" or better hybrid bows.
I was using a 704 gr arrow: Gold Tip Big Game full lenght, Beman Vibrake 24gr insert, 3X5" feather and Wrap (20 gr) and 300 gr point.
I was shooting through my prochrono at 1 yard to a target at 7 yards. In order to make a "tru shot" and not a chrono shot i was shooting the ear of my deer and accept the speed only if my arrow hit the spot.
I have a very long drawlenght @ 31,5" but very reliable. I took several valid measures with each bows and speed was within 1 fps (if different).
My bow:
- ACS CX 12" riser/64" AMO (special order) weighted 57# @ 31"
- Caribow Peregrine 62" AMO weighted 59# @ 31"
- Fedora Xtrem 12" riser/64" AMO weighted 56# @ 31"
The brace height was set in the average  for the ACS and the Fedora (7") and to the maximum for the Peregrine 7,5". i built out the window on the ACS in order to shoot properly the same arrow.
All bows have a bamboo core even on the ACS (optional).
I was using the 12 strands stock string: flemish on the ACS and endless on the Fedora and the 10 strands stock flemish string on the caribow. (All modern strings).

Results
 ACS: 184 fps
Caribow 182 fps
Fedora 180 fps

If we adjust the draw force and brace height all bows are within 3 to 4 fps with that same arrow and even at a same gpp arrow. And those bows outperform most of recurve bow out there i tested myself.