Primitive Archer
Main Discussion Area => Bows => Topic started by: Jakesnyder on June 06, 2020, 08:21:56 pm
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So I was wondering what are the benefits of recurves vs. The entire bow being reflexed(weather natural or heated in). is there benefits of one over the other? would one have more performance than the other one if everything else was identical?
I'm guessing the one with the reflex would have more early energy stored? Then would recurves win at full draw?
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I am interested in this question too. Also interested in recurves vs reflex vs deflex/reflex profiles, if they all have the nocks the same distance ahead of the handle when unbraced. People say that a deflex/reflex profile will deliver the best cast, but for the life of me I cannot understand why.
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just my 2cents Eric: d/r profile allows to get the bend closer to the handle which provides better energy storage and string angle (without overtressig the wood)
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I think the Badger makes the same claim, but don't quote me on that. I would like to hear Pat M"s opinion on that since flight shooters seem to lean to sharp recurves with straight limbs sorta, and short bows. May be that design works best with super light arrows, and the other designs work best with longer bows,and longer heavier arrows.That is just a giant guess on my part, and I could be totally wrong.
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Non working recruved selfbow has no advantages over a plain reflexed selfbow thatI have ever shot or hunted with. None. Not in accuracy or in speed.
Sure a short bow with less limb mass at a predetermined draw weight and length restriction will shoot faster and harder but it comes at a cost!! How many shoots do get out of it before it degrades severly?
Arvin can tell you more Pyramid vs slatbow vs round/oval belly better than I.
Hedge~
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This thread may shed some light but I haven't read it for a while.
https://www.primitivearcher.com/smf/index.php/topic,66666.0.html
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No one has yet mentioned that recurves improve the string angle at full draw and this helps prevent stacking. R/D bows tend to allow higher string tension at brace without overstressing the wood at full draw, along with the better string angles that the recurve tips bring.
Mark
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......... flight shooters seem to lean to sharp recurves with straight limbs sorta, and short bows. May be that design works best with super light arrows, and the other designs work best with longer bows,and longer heavier arrows...........
If this is true, then the radius of the recurve matters?
If sharp statics do better with lighter arrows, do they also do better with all arrow weights?
Or do larger radius recurves actually do better with heavier arrows?
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as far as working recurves vs reflex goes, Tim Baker corrects himself from earlier volumes in TBB4, where he says that, actually, only tip position in relation to the handle matters - setback, reflex or recurve has the same effect. He also states that stack is dependent mainly on the angle between handle, bow tip and arrow nock - not the angle between the string and the bow limb close to the tip.
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as far as working recurves vs reflex goes, Tim Baker corrects himself from earlier volumes in TBB4, where he says that, actually, only tip position in relation to the handle matters - setback, reflex or recurve has the same effect. He also states that stack is dependent mainly on the angle between handle, bow tip and arrow nock - not the angle between the string and the bow limb close to the tip.
Tip position--This tends to follow what I've noticed when examining my bows. The thing that stands out is the more reflex there is, the faster it is. Unfortunately all my bows are roughly the same style(RD) so I don't know if that holds with all styles.
String angle--One of the things I learned in school was that the shape of a lever doesn't matter, it's the distance between the fulcrum and the effort that does so I've always thought that the string angle should be measured as Baker says. That said there might be something to the fact that the lever is bending all the time. If you imagine string angle is just the triangle that Baker talks about it would seem that a recurve should stack exactly the same as a straight bow. But, as the tip comes back it does lengthen the lever a bit. That may reduce stack. Sorry I'm think out loud here. I'll think to myself for a while. :D
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I think a well built ,, reflexed through the whole bow, would shoot as well as a recurve with the tips same amount in front of handle,, Im just guessing,, but I think it would be pretty close,,
the tips could be so narrow and light on the reflexed bow,, it seems they would be lighter than the recurves,,
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as far as working recurves vs reflex goes, Tim Baker corrects himself from earlier volumes in TBB4, where he says that, actually, only tip position in relation to the handle matters - setback, reflex or recurve has the same effect.
I haven't read V4 yet, is this referring to unbraced tip position?
He also states that stack is dependent mainly on the angle between handle, bow tip and arrow nock - not the angle between the string and the bow limb close to the tip.
I would agree with that, I wasn't talking about the angle between the tip and the string but the angle you describe.
Tip position--This tends to follow what I've noticed when examining my bows. The thing that stands out is the more reflex there is, the faster it is.
Near as I can tell that is because reflex just stresses the limb more, leading to higher energy storage. The big trick with reflex is having a material that will withstand the stresses and getting it strung without throwing the string.
String angle--One of the things I learned in school was that the shape of a lever doesn't matter, it's the distance between the fulcrum and the effort that does
That is correct. The shape of the lever affects the internal stresses it sees, but not the forces seen at the fulcrum or ends. Stacking starts when the the distance from the handle perpendicular to the string starts to go down after reaching whatever its maximum is based on the bow geometry.
If you imagine string angle is just the triangle that Baker talks about it would seem that a recurve should stack exactly the same as a straight bow.
Recurve tips don't follow the same path as those of a flat bow and don't end up in the same place when drawn so there is no reason for them to share the same draw characteristics with a flat bow. For those that like to play with software such as super tiller or virtual bow you can see when stack starts in a graph of string tension as it drops from the maximum at brace height, then eventually starts climbing again once stacking begins.
Mark
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Between this thread and DC's string angle thread I had to do more looking at this.
Using Super Tiller I designed a basic flat pyramid bow. I chose this because it is what my current bow project is so I have all the dimensions at hand and it is as good of a flat bow design as there is in terms of performance and pleasant shooting characteristics. S65" NTN, 40lb@28", material is maple. The back profile is 2" wide out of the fades for 3", then a straight taper to 5/16" at the nocks. Limb thickness is constant out of the fades, 0.370" to get my draw weight and length (as predicted by Super Tiller). Brace height is 7.5", measured from the back of the bow (this is how Super Tiller geometry is set, nothing significant about it), which is more like 6" when measured conventionally from the belly side of the grip.
Once I had this bow analyzed I then made two more bows based on it. The back profiles are the same for all 3 bows, limb thickness is kept constant but was adjusted to get 40lb@28" for each bow. On one bow I recurved the outer 6" of the limb tips in a smooth arc to 2" forward of the handle. On the other bow I reflexed the entire limb out of the fades in a smooth arc to the same 2" forward of the handle.
I did not adjust the thickness taper to minimize stresses, which really needs to be done to maximize the recurved limb design. This is more a comparison of what happens when you take a simple flat bow and then either reflex it or flip the tips. The recurved version did not have big enough hooks to shorten the effective string length at brace, so it was very representative of many of the bows I see here. Here is a summary of the results. Excuse the funky formatting, the forum doesn't make that very user friendly. Note that the stresses are somewhat arbitrary and it is the changes between the designs that are important, not the absolute magnitude of the numbers.
Bow Version String Tension @ Brace (lb) Energy Stored (ft-lb) Energy Stored % Change Maximum Stress (psi) Max. Stress % Change
Flat 57.4 36.1 --- 22,009 ---
Recurved Tips 71.8 38.4 6.37 24,068 9.36
Reflexed Limb 63.4 37.2 3.05 23,923 8.70
IMO, the things to take away are that the recurved tips increase the early string tension, energy stored and stresses the most and that both recurving and reflexing increased the stresses more than they increased stored energy, which seems like a poor trade to me. I have done similar studies with R/D bows and they tend to increase energy stored more than stresses, so they would appear to be a better way to design a bow if you have the opportunity to do it that way from the start.
Mark
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If I'm following you the recurves were more of a flipped tip than a recurve. Did the string lay on the bow at brace? I'm just wondering where the increased string tension came from.
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Statics just seem to have an edge. Of course there's no reason you can't combine the D/R with static tips, which is exactly what you do.
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Did the string lay on the bow at brace? I'm just wondering where the increased string tension came from.
No, the string never touches the recurve, it is very much a flipped tip type of recurve. The extra tension comes from bending the limbs farther to reach brace. Compared to the flat bow version the recurve showed a maximum stress at brace 19.5% higher.
Mark
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ok what does all that mean,, :)
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I have only built a couple recurves and found no advantage in cast or speed.recurves require more mass in the outer limbs and rob cast. Also for me 2-2-1/2” reflex is about all I have managed to keep-in the limbs with out excess set. That makes a 67”-69” pyramid the winner in the broadhead class. Not so in flight arrows. At least I have not found the right flight arrow for that bow yet. Reflex in the inner limb seems to cause more shock than on the outer . Don’t know this is the best design but it’s breaking records currently. Arvin
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Super tiller aint very primitive is it.
Close werks for me every time.
Hedge~
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ok what does all that mean,, :)
Probably much of what you already know through experience. Taking a flat bow and recurving the tips or reflexing the limbs adds energy storage at the expense of higher stresses in the wood. Stresses go up faster than energy storage, so it is a game of diminishing returns as long as your wood is up to the higher stresses or else you get a bunch of set or a broken bow.
And, as you pointed out, there is more to how a bow shoots than just energy storage. It still has to be able to get that extra energy into the arrow for any useful gains and those may come at the expense of user friendliness, longevity or other desirable characteristics.
Super tiller aint very primitive is it.
It's just another tool in making a bow, depends on if you think a primitive bow needs to be made using primitive tools/methods or not. I like to use everything I have available to me to learn and improve my results.
Mark
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Hedge if I understood the math I would use Super Tiller. Since I am math challenged I go with what makes since and performs after the build. More work and guessing but sometimes I get lucky. Arvin
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Also that caul at pappys must work it’s been there forever. Don’t know if it was designed with Super Tiller. I doubt it though. Arvin
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Hedge if I understood the math I would use Super Tiller. Since I am math challenged I go with what makes since and performs after the build. More work and guessing but sometimes I get lucky. Arvin
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Got a few of em. I see ya when ya get here Arvin. Pyramids are where it at for sure but wood has to real clean to make em thin enough to keep limb mass down.
For all round shootin its hard to beat the American flat selfbow with a shelf.
Hedge~
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So one of the take home messages from reading this for me is that the R/D profile is a very good option for getting the best out of a wooden bow. Now because technically the definition of a “longbow” is that the string doesn’t touch the tips once it leaves the nocks and an “English Longbow” is defined by its cross section - can one make a R/D ELB and have it still considered an ELB?!
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Not by IFAA rules I believe.
R & D selfbows that are not backed and lamed up are not easy to make unless you have a piece of wood that kinds has those characeristics. Can be accomplished but to hold that profile like you see with a lam bow its just not that simple.
HH~
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I wouldn't say that's true. A heat treated limb holds reflex in a regular bow so it's just a matter of deflexing the handle or fades with steam and reflexing the limb. No lamination needed.
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RD Elm self-bow
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Asymetrical?
Just barely behind handle. They can be done as I said. I have made full partial working recurves outta elm not easy. Prefer it to a minimal R & D unbacked selfie any day.
This is early on with a winged elm full recurve where the curves actually flexed out about 1/2". Got gifted away to a fella down by Hendersonville, TN. This one was out if a very very nice section of old winged elm. A true dart slinger.
HH~
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Marc that’s a good design. I know they don’t take set or string follow. Now I know where Lonnie got his design. His is not as radical in reflex. Arvin
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This one we did for Gil. Came it at 60-65lbs@28". Elm very quick bow and dead in hand after shot.
HH~
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Shawn what’s the force draw look like ? Does it stack? Arvin
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That elm tree came off a bluff sitting on top of a gray limestone. Not a place you would normally find one. Surrounded by HHB.
Made limbs 1 5/8th way out then just narrowed tips. Had early string weight and felt about the same out to Gils full 28+ draw.
Fact that you need a bunch limb mass to keep That kind of weight.
Gil can shoot very heavy bows rather routinely. This bow was flipped a tad if i remember right it was pulling about 2.5lbs last inch or two.
Hedge
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That bow is symmetrical and was made quite a few years ago for a young man in Ontario