Why deflex reflex? (composite bows)

[rodlonq]

Hello All,

Looking for some comments on the virtues of D/R longbows. I have been looking at pictures of as many bow designs as I can find and D/R seems quite popular. My question is why?

A lot of the D/R bows seem to have the string nocks roughly in line with the back of the handle, just as a straight laid bow would have. Is the purpose simply to reduce the string angle at full draw to allow longer draw or shorter bow length.

No matter which way I look at it I cant see how the performance of the bow can change much by shaping the limbs i.e. straight vs shallow D/R.

I know the best way to find out is build one of each with the same core thickness, materials etc. just looking for ideas is all. It seems to me straight laid or just reflex is much easier to build, especially with respect to getting the handle section to match the form. Thanks.

Cheers.......Rod

[longbowinfected]

I have found that d/r longbows perform about as well as a longbow of same dimensions and materials but like it had the performance of a bow10 pounds heavier. Having said that they expose poor form and are a little twitchy. Quite significant increase in arrow speed compared to a flat laid bow in the same materials/dimensions.
This is based on d/r longbows that Longbow Steve has made.

Kev

[Stickbow Hunter]

G’day Rod,

No doubt you will get a lot of differing opinions on this one but the answer really depends on wether you wish to incorrectly call semi-recurves longbows. The majority of deflex/reflex designed bows today (not including the working recurves) are semi-recurves and not longbows because the limbs still reflex when strung (they are not straight limbed as in the limb doesn’t continually bend towards the archer as does a longbows limbs). Yeah I know a lot will dispute that but so be it.

This diagram is an example of a deflex/reflex designed longbow.

Bow Designs 7 - longbow.gif (9.1 KiB) Viewed 3093 times

This diagram is an example of a deflex/reflex designed semi-recurve (the string actually only touches at the string nocks).

Bow Designs 8 - semi-recurve.gif (54.32 KiB) Viewed 3093 times

As I give my answers to your questions my comparisons will be to the deflex/reflex longbow as in the fist diagram above and not the semi-recurve.

A lot of the D/R bows seem to have the string nocks roughly in line with the back of the handle, just as a straight laid bow would have. Is the purpose simply to reduce the string angle at full draw to allow longer draw or shorter bow length.

Yes, I believe this to be about their only advantage. This isn’t any huge advantage IMO but the string angle is less because of the different bend in the limbs. This changes depending on where and how much deflex or reflex you put into the limbs.

No matter which way I look at it I cant see how the performance of the bow can change much by shaping the limbs i.e. straight vs shallow D/R.

A mate and I did a lot of testing back in the 1990’s and we got to test quite a few different makes of bows and some of the big name American made bows made at the time included. We did not test one deflex/reflex designed bow that was any faster than our reflex designed bows and most of them were in fact slower. They were faster then the flat laid bows we had tested but not the reflex designed bows.

I also did not find them to be any smoother to draw or have any less hand shock than our reflex designed bows.

Other design factors that can affect a bows performance are core thickness as in wide limb thin core or narrow limb deep core, limb tip mass etc.

In reality there really isn’t any bow designs used today that weren’t used in the past; what has changed is the materials used and these materials have lead to increased performance figures.

In years past a well made longbow was generally slower than a similar draw weight well made semi-recurve which was in turn slower than a well made working recurve.

Looking at the bows made today using hitech materials the relationship between the performance figures of the different bow types doesn’t seem to have really changed. I will use the performance figures given for the bows made by one of the top bow makers in America as an example. These bows use carbon and foam cores etc etc.

His deflex/reflex longbow shoots approx five fps slower than his semi-recurve and his working recurve is approx four fps faster again.

Anyway that is probably more info then you requested but that is my take on things.

All the best with your bow making mate.

Jeff

[kimall]

Jeff I would love to see the test results of those tests as I just have not found my findings to be anywhere near what you have found.I have bows here you would call Semi curve I spose I dont care what they are called as I just shoot them but I have yet to find ANY bow design that shoots pound per pound as fast.This includes top end US bows that guys have brought around here to shoot through the chrony.I am not set on any pacticular design just the one that is the best performing and WILL change the way I make my bows as soon as I find a better design.As a note though some of the biggest name bows have been the slowest............
Cheers KIM

[Stickbow Hunter]

Jeff I would love to see the test results of those tests as I just have not found my findings to be anywhere near what you have found.I have bows here you would call Semi curve I spose I dont care what they are called as I just shoot them but I have yet to find ANY bow design that shoots pound per pound as fast.

Kim,

I think you may have misread my post as I clearly said those tests we did had nothing whatsoever to do with semi-recurves so I fail to see how my findings conflict with yours.

Jeff

[kimall]

Yer I see your point mate I didnt read it right to much of a hurry sorry.I do think that there is still a lot of confusion about what the differant bow shapes are called.
So to answer the original post forget the R/D bows and go straight to the semi recurve. and enjoy the best of all worlds.
Cheers KIM

[Stickbow Hunter]

go straight to the semi recurve. and enjoy the best of all worlds.

Nah, I'll just keep on enjoying shooting my old dinosaur bows.

Jeff

[longbowinfected]

nothing wrong with flat laid. The bow is normally better than me and pretty forgiving for mine.

Kev

[Dennis La Varenne]

Rod,

I would like to add a 'me too' here as well.

I have played around with the deflex-reflex design too. I have two in my posession now and have tested three or maybe four others through my chrony at home here. I am blowed if I can detect any advantage at all over the standard slightly reflexed Howard Hill design. Shifting the traditional 10gns per pound of bow draw weight to keep different draw weights comparable, there is simply nothing in it. There is actually more variation across the range of bows than within or between each group. They all shoot pretty much of a muchness to me with individual bows being superior possibly because of quirks of their construction rather than because of their design.

The bottom line is what they do through the chronograph - the only really objective criterion we have for assessing performance. A more efficient bow design by definition should shoot any given arrow mass faster.

I would not like to be put on a witness stand and have to swear to the relative advantage of either. Deflex-reflex designs look to me to disadvantage themselves by destressing themselves as the limbs leave the handle riser and then try to make up that loss by reversing direction to re-stress themselves.

To me, that begs the question of why do it in the first place. Sometimes I get the dark thought that the design arose more from marketing and the need for increased product range than any genuine benefit. Spin can be a thing of wonder.

I have been told quite emphatically that the deflex-reflex bow confers a benefit in terms of 'smoothness of draw' which is a dead loss on me because I have never been able to feel that in any bow of any design. I can only feel the heavier-lighter effect of different draw weights, but 'smoothness' has always been beyond me.

Any bow which has a force-draw graph in which the early draw weigh increases at a rate greater than later in its curve (what Tim Baker refers to as a 'plumped out f/d curve') will obviously be a more efficient bow because the area under the curve represents the stored energy in the limbs. A plumped out f/d curve, pound for pound of draw weight should be able to move a given arrow at higher velocity than a bow which has a straight or reverse plumped curve because the amount of limb-stored energy is obviously less for the same draw weight and draw length.

Anyway, I just haven't been able to detect even this indication of superior performance in the three d/r bows I have plotted so far, so I am at a bit of a loss for evidence for the supposed benefits of the design. But very many people will swear by the benefits of the design without ever seriously testing their equipment.

If I am wrong in my findings, I would like it explained to me in a way that I can test myself to get a corroborating result, and also to find out why the design works.

[GrahameA]

Morning All.

... A more efficient bow design by definition should shoot any given arrow mass faster.

A comment. Efficiency is a measure of the "Energy In" compared to the "Energy Out". For two bow with identical F/D curves shooting the same the more efficient bow will shoot the arrow faster. i.e. the kinetic energy of the arrow will be greater and will be a greater proportion of the energy that was stored in the bow.

"Effectiveness" and "Efficiency" are often interchanged they are however, different.

... Any bow which has a force-draw graph in which the early draw weigh increases at a rate greater than later in its curve (what Tim Baker refers to as a 'plumped out f/d curve') will obviously be a more efficient bow because the area under the curve represents the stored energy in the limbs.

No necessarily true. Whilst it may have stored more energy it may not be more efficient. As an example, excess limb mass will result in lower arrow speed and thus a lower efficiency when compared to a bow with lighter limbs. The better the bow can transfer that energy to the arrow the more efficient it will be.

A plumped out f/d curve, pound for pound of draw weight should be able to move a given arrow at higher velocity than a bow which has a straight or reverse plumped curve because the amount of limb-stored energy is obviously less for the same draw weight and draw length.

The operative words here are, "should be able". The design has the potential to store more energy. The execution of the design into a final product will determine how well that potential is realised.

[longbowinfected]

I will say this that the best scores are being shot in distance archery by the best archers in ASNSW and they have all changed up to d/r longbows except for a few of us and their scores have lifted demonstrably. This is not merely because of competition or increased practice but they have practised to maintain form. It isalso not just because of the bows.
Most have dropped back from a higher poundage and ge the same or enhanced performance. This is with gap shooting. We discuss our gaps and bow performance.

Where it really counts is at the longer distances, 60m and 50 metres. Prety nearly every state and a number of national records have been shot using d/r longbows. These guys have all used chronys to assist them in their choice/movement to d/r bows.

Regina Bohler has for instance after 5 years suddenly improved her scores by 20% using a d/r bow and is giving many of the boys a spanking......especially those of us still using flat laid bows.

Come up to the AA Nats this year at SQAS and put the bows used there through a chrony.
I know if I ask Mr Amy he will investigate further. Personally I like my flat laid boo bows with timbers.....they feel right and speed is not everything to me and I am still improving even though I am going through chemo. I am simply not as talented as the top boys and girls.

Kev

[Gringa Bows]

Thanks for your reply Jeff,until i saw those diagrams i really did'nt know the difference between the two styles of bows....D\R & semi recurve.

[Stickbow Hunter]

I will say this that the best scores are being shot in distance archery by the best archers in ASNSW and they have all changed up to d/r longbows except for a few of us and their scores have lifted demonstrably. This is not merely because of competition or increased practice but they have practised to maintain form. It isalso not just because of the bows.
Most have dropped back from a higher poundage and ge the same or enhanced performance. This is with gap shooting. We discuss our gaps and bow performance.

It's the same old question Kevin, have they moved up to deflex/reflex longbows or to semi-recurves? It's easy to tell as if the limbs still reflex when strung then, no, they are not using longbows at all - even if the rules they shoot under allow such bows in that section.

Jeff

[GrahameA]

Morning Kevin.

I will say this that the best scores are being shot in distance archery by the best archers in ASNSW and they have all changed up to d/r longbows except for a few of us and their scores have lifted demonstrably. This is not merely because of competition or increased practice but they have practised to maintain form. It isalso not just because of the bows.

Most have dropped back from a higher poundage and ge the same or enhanced performance. This is with gap shooting. We discuss our gaps and bow performance.

D/R bows have the potential to store more energy. Thus, if the finished product is well executed, it is possible to get the same arrow speed with a lower holding weight bow or a faster arrow at the same holding weight. Faster arrows, all things being equal spend less time in the air and thus less drift and less offset is needed at the maximum distance.

All that aside, I would suggest that the improvement is more related to "practice/coaching/information sharing" than it is to bow performance.

Where it really counts is at the longer distances, 60m and 50 metres. Prety nearly every state and a number of national records have been shot using d/r longbows. These guys have all used chronys to assist them in their choice/movement to d/r bows.

Regina Bohler has for instance after 5 years suddenly improved her scores by 20% using a d/r bow and is giving many of the boys a spanking......especially those of us still using flat laid bows.

In all fairness here Sandy is still using a more conventional designed bow and doing very well thank you. If it was the bow then we would expect to see a step increase in the score. So the question to check would be did the scores undergo a step increase when the swap to a different design occurred or did they slowly increase as more practice was done? I would also ask the question could the increase be attributed in part to the use of better bow - ie the bow is inherently more stable or suits the archer better? It is my opinion that at this point there are too many unknowns to attribute any change to a bow shape alone.

Prety nearly every state and a number of national records have been shot using d/r longbows.

Cannot speak for NSW. However, without doing a thorough check I would suggest that in SQAS that would not be true and Nationally I would suggest that the majority of records have been shot with conventional bows and probably the total new Longbow records shot in the last 12 months have been shot with conventional designs. (Just did a superficial check and that appears to hold true.)

[longbowinfected]

Grahame I think it is a combination of things.
One of te features for some of these archers with the faster bows is the consequence that they do not need monster draw weights for competitions for distance with heaps of arrows being shot at longer distances. Another is that the gaps are based around a point related to the target butt. Say 60 metres being point on top of the target or on the gold with say for 50 metres the point being on the bottom of the target and then the others further down the leg. Admittedly with lower pound or slower flatbows you can use lighter arrows but at most of the major target courses wind affects the lighter arrows if you try to use them with the same gap points. The gapsare also much further apart too.

Whilst many here do not gap shoot it is pretty hard to consistently shoot instinctively for say 100 arows all up at 60, 50 and 40 metres. i admit it is fun to instinctively shoot at the shorter 30 metres. Shooting long distance target using a lower poundage flatlaid bow with woods is more difficult at 60 metres.....really notice when wind plays with your darts.

For someone shooting shorter field or hunting distances there would be little difference in using flatlaid or d/r or other longbows.

I prefer my flat laid and woods. The others are shooting longbow as much as we are all really shooting modern longbow.

Kev

[Steven J]

I find it interesting what Dennis says about smoothness. I have always thought this was a bit of a joke myself. I think that there are some people that like to give names to nebulous concepts that they claim to feel so that others seem smaller in their presence. I think smoothness is more about the man than the bow.

I think that the performance of a bamboo limb is questionable also. I have found no evidence through the chronograph. I do find that I need to increase the limb thickness when using bamboo, and think that any advantage of the lower mass is off-set. It is a good material though as it is homogenous and therefore predictable.

My experience only extends to flat laid bows at this stage. When I finally finish of my workshop, I will have a bit more room for testing.

Steve

[Stickbow Hunter]

I think that the performance of a bamboo limb is questionable also. I have found no evidence through the chronograph. I do find that I need to increase the limb thickness when using bamboo, and think that any advantage of the lower mass is off-set. It is a good material though as it is homogenous and therefore predictable.

Steven,

I'm not sure of what bamboo you have experience with but from my experiences there can be big performance differences between the types of bamboo used as a limb core just the same as there is between the different species of woods. From my experience good quality natural bamboo is by far the best natural limb core material there is, at least for a narrow limbed deep cored longbow. The bamboo flooring is not as good as quality natural bamboo but is better then poor quality natural stuff.

Jeff

[Dennis La Varenne]

Through Rod,

Grahame, thank you for pointing out my loose use of terms. You are quite correct of course.

All the same, I am still unconvinced of the superiority of the d/r design based on my own testing related above. Where I wrote in relation to 'plumped out f/d curves' as indicators of efficiency - meaning that a more efficient bow will be able to move an arrow of given mass faster than another with a straight line f/d curve or a concave f/d curve, I should have inserted the four words 'WHERE ALL ELSE IS EQUAL'.

Of course the difficulty of the 'where all else is equal' precept is that it is difficult to compare like with like across bow designs unless total bow mass and mass distribution throughout the bow are also the same with the only difference being the side profile alone.

I am still inclined to believe that there is so little in it that it is hardly worth bothering with in the case of conventionally made commercial bows. Perhaps the only way in which to achieve equal total and distributed mass through a bow is to have each made from completely synthetic materials where both the mechanical properties and mass of the materials used will be 'consistently consistent'. There is far too much variability within the largely natural materials used to be definitive about any claims of superiority of design without large scale 'epidemiological-style' studies being done.

[Steven J]

Jeff,

We might be getting of topic here, but...

I have not used any bamboo that I have harvested and ground to laminations in my laminated fiberglass skinned bows. The only bamboo that I have used in these bows has been cut into laminations by John Clarke. As you suggest, maybe this is a problem.

I generally use 4 laminations in my longbows. The inner two are almost always vertical bamboo flooring. I find that when I use bamboo in the outer laminations also that I need to increase the core thickness by about 10% to maintain the draw weight compared to bows with, say Tasmanian Blackwood for the outer laminations.

I do not chronograph every bow that I make. Firstly some are just too heavy for my spindly little arms . Secondly, I think a shooting machine is needed to reduce the variation experienced when shooting with the body.

I don't build a lot of all bamboo limbs. Out of those built and chronographed I have 4 bows that I can use to make a weight for weight comparison against those with only the inner two laminations of bamboo. I have found that there is more variation in my shooting ability than there is between bows with different core compositions.

When I have the new workshop done (that is my current excuse for everything) I will also build a shooting machine and gather the data in a scientifically valid manner. Maybe then I will be able to make a better comparison. For the moment I am reserved.

The other major goal that I am to achieve is having the space and a workshop not attached to the house so that I can grind laminations without fear of choking the family. Maybe then I will have a little more control over production.

I would be interested to know what bamboo you use, and how you have verified the benefits. I would also be interested to know how you assess the quality of the bamboo that you harvest / purchase. Maybe this could be moved to another thread.

Steve

[GrahameA]

Hi Dennis.

Grahame, thank you for pointing out my loose use of terms. You are quite correct of course.

IMHO In this case I hold the view that we should use the correct terms - perhaps it would be better to approach it from an Engineering/Scientific viewpoint. This is one of those topics where I see/hear also sorts of claims that are not backed up by rigorous evidence (i.e. Numbers)

All the same, I am still unconvinced of the superiority of the d/r design based on my own testing related above. Where I wrote in relation to 'plumped out f/d curves' as indicators of efficiency - meaning that a more efficient bow will be able to move an arrow of given mass faster than another with a straight line f/d curve or a concave f/d curve, I should have inserted the four words 'WHERE ALL ELSE IS EQUAL'.

Personally, "I would like to see the numbers" - I tend to be very cautious with regard to unsubstantiated claims. Plus experience suggest that like most "Swings and Roundabouts" what you gain in one area you lose in another. 2nd Law of Thermodynamics - there is no such thing as a Free Lunch, there will be a cost somewhere.

Of course the difficulty of the 'where all else is equal' precept is that it is difficult to compare like with like across bow designs unless total bow mass and mass distribution throughout the bow are also the same with the only difference being the side profile alone.

Yes, so immediately it becomes hard to show that any particular design has a real advantage as distinct to a theoretical one.

I am still inclined to believe that there is so little in it that it is hardly worth bothering with in the case of conventionally made commercial bows. Perhaps the only way in ....

I am open on this one - i.e. I want to see a bit of testing before I would go either way. Perhaps a bit of 'Finite Analysis' would give some good predictive values.

For the moment I would tend to put a lot of the value of the design down to the end-user having more faith in their tools. If you believe it shoots better it probably will. The again there is the aspect that a well made bow from a small manufacturer will probably shoot better as they have optimised the bow during its manufacture. Commercial manufactures are unlikely to put in the time per bow to optimise their product.

[rodlonq]

Thank you to you all for your replies. I would have chimed in a bit earlier but I didn't want to detract from the discussion - it is all very good information. Many of the issues below have already been addressed in some form, just looking for a bit more clarity.

My intention is to try and keep my first few bows within the rules for a "Traditional Longbow" as per the ABA. According to the ABA rule the limit of the reflex is that if you run a string line along the back of a braced bow (from inside the overlay to the fadeout) there should be no gaps underneath the string. If a gap can be seen, the bow falls into the "Modern Longbow Division" up to a point where the string touches the belly other than at the nock, then it becomes a "Recurve". This is my interpretation of the ABA rules and I am open for correction.

I have made some sketches of two concepts which I would like to discuss further. Referring to the two pictures below (solid lines are straight, dotted lines are uniform arcs) and trying to compare apples with apples;

The first is a comparison of the profile (back of bow) for two bows 68" NTN, one straight laid the other with shallow D/R (1.5" deflex followed by 1.5" reflex). I think both bows would be classified as "Traditional Longbows" when braced. What I cant see is why the D/R model would perform any better than its counterpart straight bow.

Straight Vs Shallow 1.5%22D-1.5R.png (8.54 KiB) Viewed 2952 times

The second is a comparison of the profile (back of bow) for two bows 68" NTN, one reflex only (1.5" reflex) the other with shallow deflex and pronounced reflex (1.5" deflex followed by 3" reflex). I think the reflex only bow would be classified as a "Traditional Longbow" when braced. I think the D/R bow would be classified as a "Modern Longbow". Again, what I cant see is why the D/R model would perform any better than its counterpart reflex only bow.

1.5%22Reflex Vs 1.5%22D-3%22R.png (11.46 KiB) Viewed 2952 times

The way I understand it, both of the bows in the second picture should outperform both of the bows in the first picture, because with the net reflex (both have 1.5" net reflex??) you can lighten the limbs a little to get the same draw weight and so they will shoot quicker. Given this, and that I would like to shoot in the "Traditional" category, it appears to me the reflex only design would be easier to build, is more compact for transport (maybe) and should shoot as well as any other design within the "Traditional" category.

Fellas, let me say that even though the words above sound like I am telling you all how it is, that is just how I have expressed my reflections from research. I reckon I could have bought a really good custom bow with the money I have spent on research materials alone, however I would have even less idea of how it all works. I am completely open to correction on any points made above and look forward to it.

Cheers...Rod

[Dennis La Varenne]

Through Rod,

Grahame,

IMHO In this case I hold the view that we should use the correct terms - perhaps it would be better to approach it from an Engineering/Scientific viewpoint. This is one of those topics where I see/hear also sorts of claims that are not backed up by rigorous evidence (i.e. Numbers)

I agree entirely, but I haven't got the science background I wish I had to be always able to do so, so I try to be as consistent and understandable as I am able when I post opinions on Ozbow. But I have no objection if you point out correct scientific terminology certainly.

2nd Law of Thermodynamics

- Agree entirely.

it becomes hard to show that any particular design has a real advantage as distinct to a theoretical one.

- Agree again.

I would tend to put a lot of the value of the design down to the end-user having more faith in their tools

- That is what it seems to be to me rather than any measurable benefit.

Rod,
What you are saying in your diagrams about the designs in your post immediately above explains my quandary exactly.

[Stickbow Hunter]

My intention is to try and keep my first few bows within the rules for a "Traditional Longbow" as per the ABA. According to the ABA rule the limit of the reflex is that if you run a string line along the back of a braced bow (from inside the overlay to the fadeout) there should be no gaps underneath the string. If a gap can be seen, the bow falls into the "Modern Longbow Division" up to a point where the string touches the belly other than at the nock, then it becomes a "Recurve". This is my interpretation of the ABA rules and I am open for correction.

So ABA has caved into the masses as well hey. How silly as by design a bow is either a longbow or it isn't.

IMHO In this case I hold the view that we should use the correct terms

Yeah and in a lot of other cases as well.

Fellas, let me say that even though the words above sound like I am telling you all how it is, that is just how I have expressed my reflections from research. I reckon I could have bought a really good custom bow with the money I have spent on research materials alone, however I would have even less idea of how it all works. I am completely open to correction on any points made above and look forward to it.

Yeah mate but look at the fun you have already had.
In relation to your diagrams I say that I also have difficulty in seeing any advantage other then what I posted above.

Maybe this could be moved to another thread.

PM sent.

Jeff