Primitive Archer
Main Discussion Area => Bows => Topic started by: Jan de Bogenman on January 26, 2018, 09:13:24 am
-
Ash selfbow with a hollow back. It has been shot a few dozen times and I expect it to keep up!
The cavity is 11/32" and has been extended over the entire limb.
-
Beautiful tiller and I love the back profile. Very nice work. :OK
-
Fascinating.
-
Weight?
-
Specifications:
Straight pyramid ash selfbow
length: 71" (1,8m)
Width: 2" (5cm)
Width nock: 0,4" (10mm)
Handle and fades: 8" (20 cm)
Handle cross section: 0,9"x1,3" (23x34mm)
Drawweight: 35lb@28"
Set after tillering: less than 1"
Weight 14 oz (398gram)
Speed 10gpp: approx 170fps (linen string 80 grain(5gram))
The aim of this experiment was to find out whether a hollow back can save mass and increase speed.
I think speed is pretty good, but mass is certainly saved.
As for speed, the picture shows the device I use. The finger blocking is on 28" from midd handle.
-
Very nice, this should be telling us something but I'm not sure what it is :D
-
I like your approach to bow making :)
-
You have my undivided attention with this bow! The weight you have achieved for a 71"length bow is simply incredible! The feather light weight coupled with the speed makes this a truly an amazing bow. I have to try one myself, you certainly have set the bar very high!
By the way I also like the device you have set up to Chrony your bow. I would love to have you explain the details for it, I am always struggling with repeatability of my Chrony measurements and sometimes they are all over the place.
Again awesome work!!
-
Hi Jan,
Just as a follow up and I have mentioned that on your previous attempts of this design as well, this design has a good example in nature (nature usually gets its designs right) and that is the bird feather. It has a very similar design with two spars on the tension (back) side of the feather that do not join until close to the tip. It also features a slightly rounded belly. I have made a similar bow on a heavily crowned stave but did not nearly go to the extreme you have in your bow (mine had just a 1/4" slot fading towards the tips on each side). I wanted at the time to resemble a turkey feather. I guess the only difference between your design and the feather is that it has an elastic compound filling the spars so it is really a composite structure.
Here are a couple of turkey feather pics that show the resemblance.
-
I'm curious if you were to flip a stave around and have the back be the belly. If you followed the growth ring it would be concave due to the curvature of the limb/trunk
-
Very well done, Jan.
Hope you can find time to do a force vs. draw test.
-
Beautiful job, Tim Baker has recently taken an interest in these style bows. I will see if I can get him to come over and take a look at it.
-
Badger, are you willing to comment on the mass principle given the specs presented?
-
I would love to see Jan's design compared with the HLD design, with the same dimensions, same wood and shape and see what the cast will be and the corresponding draw weight. My intuition is that Jan's design will outshoot the HLD design. I believe the compression is more pronounced on the belly with Jan's design than in HLD and will result in faster cast.
I also think that this design should provide for a super smooth draw without stacking.
Jan: can you describe how it feels to draw the bow? Could you also measure the increase in draw weight over the length of your draw (every 2")?
-
Very cool looking bow
-
I believe the compression is more pronounced on the belly with Jan's design than in HLD
Philipp, can you explain better about "pronounced"? Spreads it out across the belly better?
-
Hi Willie, I could be wrong but I am assuming that the belly is slightly rounded. My logic would tell me that the belly would get more compression than in the HLD design where the sides of the belly get compressed first before it starts to flatten. In Jan's design the centre of the belly would compress over a wider cross section early in the draw and keep on compressing while flattening out. I might of course be out to lunch on this, but that is one more reason to get the comparison done I was suggesting earlier.
The numbers Jan published are so impressive that there has to be merit to this design. After all nature is usually never wrong, since his design resembles that of a feather which is light weight and can tolerate high cyclical loads.
-
This would be the same as highly trapping a bow, wouldn't it? say a 1 1/4" belly and a 1/2" back. Same loss of wood just the trapped back is split into two strips. Not trying to take anything away from Jan's bow, it's a beauty :D
-
@DC, I think the difference between what your example (if I understood correctly) and Jan's is that in a trapezoid bow with narrow back you would not get any flattening when you draw. I believe Jan tried to measure the flattening on one of his earlier versions of this design and I don't recall what the results were. I also think more wood is engaged in active work than in a trapezoid bow since you end up loosing the wood in the neutral zone in contributing to spring loading the bow. I believe the double spar design with the curvature to the middle engages the entire cross section with little "inactive" wood left in the neutral zone if I make sense to you?
-
Philipp, thanks for the clarification. It's always good to hear what others are thinking.
I also think more wood is engaged in active work than in a trapezoid bow
I also had the same thoughts as DC about a comparisons to a trapezoid crossection, and I am not sure what might be responsible for any crossection deformation with the hollow back. At first, I suspected Possion effect was at work, but I was never able to find out how that might change for differing crossections. Could deformation be caused by a uneven distribution of forces due to the asymmetry of the crosssection?
BTW,even in a round or rectangular, and most likely trapezoidal section there are possion effecr forces making the limb crossection squish and stretch, not exactly "inactive", but its just enough that you have to look very hard to see much movement, and radiusing the edges of the back of a rectangular limb has been shown to be necessary, because the back does raise an edge enough to lift a splinter.
-
Interesting bow and very nice work finishing your bow.
-
Question for Jan: are only the belly edges or is the entire belly rounded or is it entirely flat? It is hard to see from the pictures.
-
Here are a couple of turkey feather pics that show the resemblance.
Thanks for the picture Philipp. We do not have turkeys overhere. But lots of swans. Their feathers have a groove too, but it is not open as in this picture. This is how turkey feathers are naturally made??
Inspiring!
-
As for the mass, you are well below projected mass and the bow didn't take much set so I would conclude the design does save mass. 17.5 oz is what I would have projected
-
Thanks for feedback Badger. Hopefully the bow will hold up and gets some companions. so we can see if it is viable.
-
Jan: In regards to feathers, i believe the turkey wing feather experiences tremendous loads because of the weight of the bird and their almost vertical take off when flying to a tree. It is unbelievable how much lift they can generate with the shape of their wing and their strong wing muscles. I think it is the perfect design for extreme cyclical loading while saving weight.
I believe your bow design (which comes very close to the turkey feather in style) is a testament to how much weight reduction you can achieve while at the same time storing the energy very efficiently based on the arrow cast you managed to obtain.
Getting back to one of my earlier questions: is the belly rounded?
-
In the picture below is a cross section of the bow. figure B. (in mm.)
As you can see, the belly is nearly flat.
In a 'normal' flatbow (figure 'A') the dark zone in the belly is taking the pressure. My consideration was, to prevent set, one should not reduce this area.
Previous tests did show that there is no flattening out. Moreover, a hollow back tries to curl up. (Untill severe bending forces it to flatten out...very suddenly and with a lot of noise and splinters. But that is far beyond draw length.)
And no flattening out means that there will not be an escape for the pressure like in, for instance, a HLD. So I wanted the belly to be able to take the full load and, on the other hand, the idea was to save mass.
So it became a flat but thin belly. A little less than half the thickness of a normal flatbow, because the outer fibers are doing most of the work. The belly is about 5 mm thick. I hope this thin strip also allows the limb to do some curling and to get rid of the forces involved with that.
No flattening out also means that the ridges on the back need to take the tension all the way. Tests show that reducing these edges too much brings the bow in great danger. I see them as two cables, under high tension, which are holding everything together. If the limb is bending these cables want to get in horizontal line with the belly. But the curling up effect and the high tension gives them no room to move sideways. I made them about 10 mm wide on top and they seem to hold up.
The result is a kind of U-profile. Well known to cunstrutors, engineers, architects and construction workers!
No flattening out would also mean that there will be no extra smooth draw. Moreover, curling up would possibly mean that the draw is more tough. I think this is the case.
-
How does it respond if the belly is hollow? Does it flatten out at all?
-
Hi Jan, thanks for the design clarifications and drawings. Based on your explanations and drawings it appears that the design mostly reduces weight while maintaining performance. Are you maintaining the same thickness of the spars throughout the U profile? In a feather it is both reducing in width and in thickness over the length of the limb to the tip.
-
How does it respond if the belly is hollow? Does it flatten out at all?
I did not make a "grown up" hollow belly myself, Simon Siess is the expert on this I think. As I recall it from his website, in a comment on his atricle he answers that he estimates the flattening out is about 3 mm sideways. Don't know if there are any measurements yet.
Did some testing wih bamboo slats and little bows.
In a hollow belly construction the ridges are like coloms under pressure. They tend to break away sideways.
Its quiet clear in the pictures below, In the first picture a hollow belly. The slat is bending towards the camera. Note the spot near the vise, appointed by the round file. The bamboo splits open. Also visible is that the ridges move sideways.
Second foto is taken while bending the same slat the other way, so with a hollow back. The split closes again. The ridges are straightening up.
Considering this, I think a well made HLD will flatten out.
-
Are you maintaining the same thickness of the spars throughout the U profile? In a feather it is both reducing in width and in thickness over the length of the limb to the tip.
Thanks for pushing me to the next level Philipp! So far I mainatained aproxx the same width over the full length of the ridges. Except for the outer limb where everything get's narrow. This was mainly out of laziness. (Somehow I am always in a hurry to see if things will work..)
I was planning for the next to do what you suggest. To taper the ridges down from the handle to the tips. Thanks for reminding me!
And another thing concerning the feather principle. Think I remember a patent for a bow with limbs filled with foam!
-
This is amazing work, of course.... I have so many thoughts and no focus or time to try things out anymore, but the closest I have come to this is a pyramid bow, backed with two slats of bamboo from a small diameter stalk, side by side.
The first thing I wonder is, while you are definitely saving weight throughout the bow, does this save weight where it matters most? Which I still assume is in the outer limbs, toward the tips? Proportionally, I mean.
Jan de Bogenman: regarding your bamboo test piece...., I tried a couple times to make bamboo bows bend like that, but my efforts were half-hearted and did not do my ideas justice. However, I think I now have a way of making a bow of split bamboo with the concave side as the back. I may or may not get around to trying it.
The first possibility is a cable backed bow. Weight management would be an issue depending on the material and amount of cabling. I would split the bamboo, maybe splice at the handle, and taper the thickness for good tiller. By tightly wrapping some spiraling cables (opposite directions) the full length to squeeze it in from the sides. Then a main "backing" cable could ride atop those wraps, secured here and there. Basically, a hollow limb, but with a cable. Biggest problem here is that most bamboo doesn't taper quickly enough, so the whole bow could be super light, but you are saving less weight toward the tips, and again because you have to secure the cable.
-
Cool, I can't wait to see the results of your next progression of this design! In regards to foam filled spars, this has been done in wind turbine rotor blades and other composite structures before as well. It adds stiffness without adding weight. At the end with most of what we do we try to imitate what nature has already designed over millennia before us.
I enjoy the dialogue and like you I love exploring new designs and variations on existing ones. It makes this an infinitely enjoyable hobby and I have yet tons to learn from some of the seasoned experts that regularly post on this forum.
-
but the closest I have come to this is a pyramid bow, backed with two slats of bamboo from a small diameter stalk, side by side.
Thanks Springbuck, I was thinking of such a bow when working hard with chisels, gouges and scrapers on this bow! Would be great to see it, maybe you've got a picture of it?
And that idea partly ties in with your other question. Mass reduction. If one is to glue up a bow, this design can save lots of material.
Concerning the other interpretation of your question about mass: I think saving mass in the outer limbs remains the most important and most simple way to gain speed. I started this experiment to see if a hollow back could add a little more to that. Or to see if other effects, like flattening out or curling up, will influence performance. For now I think it does some. But 'some' could be very important for, for instance, a flight bow.
About bamboo bows. Sounds interesting, but maybe you can do without the cables if the bamboo is thick enough?
-
Hi Jan,
If you want to take the time to replicate the turkey feather, when examining the back of the feather closely you will see that the sides of the spars are undercut (hollowed out when viewed from the centre of the groove) and the belly is rounded towards the thick end of the feather and then gradually flattens towards the tip.
-
Hi Jan,
Interesting observation and this would corroborate the Poisson effect. I have just tried what you did with the bamboo slats with a turkey wing feather (the one I took the picture of). You could very much notice that the undercut side spars on the back were starting to close the gap when putting the feather under load and the gaps were opening back up when unloading it. Maybe undercutting them might be required in order to resemble the full elasticity of a turkey feather?! I will try to take a close up video with my cell phone to show the effect tomorrow (I observed it through a magnifying glass, so not sure whether I can replicate it with my cell phone as a close up).
-
About bamboo bows. Sounds interesting, but maybe you can do without the cables if the bamboo is thick enough?
[/quote]
I'm really bad about pics, because I have ADHD and lose them, break my phone before I store them elsewhere, etc..also, the only place I use a computer is at work and what pics I do have are at home....so...... let me see.
Doing without cables.....I know one can flatten the inside of bamboo following the fibers and use the inside surface of the bamboo as the back, as in the Bhutanese bows, but those are made from a very specific specie, very heavy with thick, and they are more like a flatbow in cross section.
It seems that to make either a concave OR hollow bow, you would want to start with bamboo about 3-4 cm diameter, maybe 5 cm max, so you can split it in half and have that "C" shaped cross section. The engineering problem I see is that most 3 cm dia bamboo (at the handle) is going to be something like 3.4 cm on the fat end and 2.7 cm on the thin end. Not enough taper, so unless you want all the bend in the middle of the bow (and fat-looking tips) you have to taper the bamboo. Right?
So how do you do that? You have to taper both front/back and side to side at the same time (because it is round). Because of this, the "C will be a half circle at the handle, but only a quarter circle at the tips, or something like that. A shallower "C", anyway. Maybe the limb will be 3 cm across and 1.5 cm "thick" at the handle, but if the bamboo starts out 3 cm dia. at the tip, the tip could be only .4 cm thick and 1.7 cm wide, roughly. To me, that is too wide and not thick enough. I want it more like 1 cm wide and 3/4 cm thick at the tips.
Either way, you HAVE to cut across the exposed fibers at the sides of the bamboo to tiller it. A large diameter bamboo then becomes NOT a hollow or concave bow, and a small diameter bamboo loses stiffness but maintains weight out toward the ends.
-
Philipp
Emulating nature seems like a good idea. I looked thru all my turkey feathers( two wings worth from a florida bird). I see a groove on the underside that is a bit more pronounced than feathers from other species, but I do not see any thing filling the groove. Are you dissecting the feather or looking at internal structure? Perhaps you could sketch the crossection? The "undercuts" you mention are not apparent or understood.
thanks
-
Hi Willie, the groove is not filled but the spar is. Just take a knife and cut through the spar lengthwise and you will find the gummy substance that fills it.
In regards to the undercut I mean, that the groove is hollowed out so the top of the spar has an overhang like a snow drift. Take a magnifying glass and you should see it well. I would not imagine that there is a difference between Florida and Canadian turkeys but who knows.....
-
Wow Jan that looks very promising! The weight reduction really shows. I wonder what would happen if you scale it up to 50@28 with a proper heat treat and without rushing the tiller;-)
-
Jan, thanks for doing this testing.
First, I haven't read all the comments on this post.
Here some thoughts:
Your design is a mass saving design, which is ok with tension strong wood (like BL or others). But you can do a lot easier going with a trapped profile or a high crown sapling. The only difference I see is your design is more problematic for torque.
You have made a stiff handled bow. Not good with the excessive grain run out at the fade area. It is probably better to go with a bendy handle bow with no narrowed grip.
Your sketch with the tension and compresssion forces doesn't show the real forces. The farther from the neutral plane the higher is the stress. In other words: the forces are not equal in the compression area (black) or the tension (white) area. Will say the more you can save the (unnecessary) mass near the neutral plane – the greater is the total effect of mass saving. Hope you can follow my bad English. Think on an extreme profile of your design, which will put the neutral plane in the real middle of an U.
At least: To bad your not working on real HLD bows, sorry to say that – but I believe your skills would be better invested in turning the bows back into the belly. But thank you anyway!
-
"Hope you can follow my bad English."
Brother Simson, there is NOTHING wrong with your English.
-
Just as a column can buckle when loaded too heavy, a beam can twist under load if not cross braced adequately.
I think many of us have experienced this when making a tip too narrow. Maybe tip lightening can be accomplished better with a well designed U section? Are the physics behind these unusual crossections related to lateral torsional buckling?
https://www.infograph.eu/en/steel-construction
-
Just as a column can buckle when loaded too heavy, a beam can twist under load if not cross braced adequately.
I think many of us have experienced this when making a tip too narrow. Maybe tip lightening can be accomplished better with a well designed U section? Are the physics behind these unusual crossections related to lateral torsional buckling?
I fully agree. The hollow tip design allows you to make a broader tip with a lighter mass. The broader tip will be less prone to torsion or sideway bending.
You can even make the tip entirely in the shape of an I-beam, but rotated 90° relative to how it is normally positioned.
-
Jan, thanks for doing this testing.
First, I haven't read all the comments on this post.
Here some thoughts:
Your design is a mass saving design, which is ok with tension strong wood (like BL or others). But you can do a lot easier going with a trapped profile or a high crown sapling. The only difference I see is your design is more problematic for torque.
You have made a stiff handled bow. Not good with the excessive grain run out at the fade area. It is probably better to go with a bendy handle bow with no narrowed grip.
Your sketch with the tension and compresssion forces doesn't show the real forces. The farther from the neutral plane the higher is the stress. In other words: the forces are not equal in the compression area (black) or the tension (white) area. Will say the more you can save the (unnecessary) mass near the neutral plane – the greater is the total effect of mass saving. Hope you can follow my bad English. Think on an extreme profile of your design, which will put the neutral plane in the real middle of an U.
At least: To bad your not working on real HLD bows, sorry to say that – but I believe your skills would be better invested in turning the bows back into the belly. But thank you anyway!
Simon, thank you for your thoughts. I must admit that I doubted for some time whether I should respond. That you do not agree, okay. But the tone of your posts in particular surprised me. But maybe, because I am a little sensitive on this subject, I'm mistaken. So, I will try to explain properly why I can not agree with some of your thoughts. It is also a good opportunity to sharpen my thoughts and exchange more information.
I am afraid it became quite a story....
-Tension strong wood: To me every type of wood seems suitable, because even now you can adapt the design to the wood type. For example, an 80lb ash bow in this configuration does not seem like a good idea, but design (width) or wood type (stronger) can be adjusted.
-Trapped design or high crown sapling. Very unlikely to achieve the same amount of mass saving in a (massive) high crown sapling. Opinion is based on several high crown bows I made, better examples or proof very welcome! I do think this mass saving is possible in an extreme form of a trapped back, with hollow edges, a so called T-profile. Do not know if that's less work .... nice experiment though...let's try it? The curling effect may then expire and maybe it is less stable?
-Torque. See the two pictures above in my answer to Badger. The edges straighten out in a hollow back design. In four bows, so far, torque was not an issue. I have experienced it as a stable design.
-Stiff handle bow and grain: Design for outer form and handle was fixed for this experiment. I tried to make a bow that can be compared to 'normal' pyramid straight flatbows that I have made from similar board staves. Comparison, for the experiment, was therefore the most important, not the optimal shape or wood selection (btw, it is a straight grained bias ringed board stave). I will keep your suggestion in mind when I am going for the optimum.
-The sketch. Yes, that's just what it is, a sketch. A simplified representation to support the story. The pressure zone is a suggestion to represent the train of thought. To avoid confusion I had better omitted the measurements, old habit, sorry.
- Removing mass from Neutral plane and make Extreme U-profile. I'm not sure if I exactly understand the shape you discribe, but it sounds very interesting !! Could you please upload a sketch?
- Finally, why not a 'real' HLD? Simply because I wanted to see what a hollow back does. And sorry Simon, and with all respect, but to me, this sounds like you think anything outside of your version of hollow limbs is nonsense. That would be a shame.
I know HLD is your baby. And I love that beautiful baby. But there are other babies and they also deserve attention and respect. (And maybe one of them will grow up to be a real big bow).
Maybe it's not good to make a comparison with HLD here, because this topic is about hollow back. And both have their own characteristics and charms. But if we are talking about it.....
Actually, a few weeks ago I did a 'turn around test'. With a scale model of a bamboo stick bow, about 60 cm long. And frankly the results were not such that I continued with the hollow belly in my quest for saving mass.
See pictures below for the model.
With hollow back this bow draws 7 kg when the string is pulled 21 cm.
When turned around (hollow belly) it dropped to 6 kg. And tiller changed in the high stress sections.
My conclusion was that a hollow back can take more draw weight per bow-mass.
Now, of course, it is all about whether that also results in higher arrow speed. Draw weight, or f-d curves, in it self mean nothing. I shot a normal 400 grain arrow through both sides. Not a very good test, I know. But the hollow back performed noticably better.
Further tests with bamboo, also with adapted cross sections according to HLD, make me come to the following provisional comparison:
- Hollow back: more load per mass, tough draw, stable, rounding of the high edges is dangerous, curling up until sudden flattening and collapse.
- Hollow belly: sweet draw, potential unstable, rounding of the edges creates sweeter draw and more control in tillering, flattening out untill soft collapse.
So if you look for less mass per lb drawweight, hollow back seems to be preferable.
But I suspect two major benefits of hollow belly, please let the experts judge:
- The flattening out ensures that the pressure has a way to escape. Lateral movement instead of being pressed together. Result: little chance of pressure failures and probably little set. That would mean durable, high performance.
- The high thin edges in the belly are very suitable to heat-treating. Like the point of an all wooden arrow. Heat-treating a hollow belly might contribute a lot to better performance.
And there is another thing: These tests were done with straight bows and full-length cavities. In a bow with strong recurve and short working parts, it might certainly becomes another game...
Okay, I'm trotting on, right? ... all that comparising and suggestions might be something for another topic.
-
With hollow back this bow draws 7 kg when the string is pulled 21 cm.
When turned around (hollow belly) it dropped to 6 kg.......My conclusion was that a hollow back can take more draw weight per bow-mass.
+1
The broader (and lighter) tip will be less prone to torsion or sideway bending.
In a bow with strong recurve and short working parts, it might certainly becomes another game...
or possibly a long working recurve? http://www.primitivearcher.com/smf/index.php/topic,5717.0.html
-
....
Simon, thank you for your thoughts. I must admit that I doubted for some time whether I should respond. That you do not agree, okay. But the tone of your posts in particular surprised me. But maybe, because I am a little sensitive on this subject, I'm mistaken. So, I will try to explain properly why I can not agree with some of your thoughts. It is also a good opportunity to sharpen my thoughts and exchange more information.
I am afraid it became quite a story....
....
Jan, it wasn't my intention to affect you, or anybody else here.
After rereading my post (reply 40), I personally cannot see any harsh words.
Sorry you understood it so, perhaps my bad English.
All the best and good luck on your projects!
-
Thanks for your reaction Simon. Plain text is always a little tricky when emotions come in. Also takes some time to understand each other. Hope to hear from you again.
-
or possibly a long working recurve? http://www.primitivearcher.com/smf/index.php/topic,5717.0.html
[/quote]
Willie, I think that should work! Such limbs are somewhat wide for stability. Seems perfect for hollowing out. And on a spot to be pefered most, the outer limb.
Oh man, so many ideas, so little time.
But a glue up can be done relatively easy? And one can save on materials too.
-
Hi Jan and Willie, when looking at the feather profile it is actually recurved for the full length. With a deflex handle one could definitely get close to that design. I think it is a good idea. A glue up would definitely be faster for a proof of concept than to carve this thing out of a stave.
-
OK, here I go again, lots of talking and not as much doing........sorry.
But, I have several designs in mind I have never seen or tried to make a super lightweight but stable recurve. They mostly involve the wood or bamboo of the recurve being very thin back to front, maybe even thinner than the rest of the limb at any point. Maybe even a shallower "C" shaped bamboo limb up to the recurve. The recurve itself is FLAT, not "C' shaped, and holds it's recurve with a cable.
Several small sections of bamboo or rattan could be used as bridges to allow binding of the cable to the limb while keeping the main of the cable raised. The recurve portion of the limb is thus maybe 60% air. The bridges can be held in place basically by the wraps that bind down the main cable, and by use of some thoughtful zig-zag wrappings the lateral or torsional stability of the recurve can be mproved.
The other type I have seen attempted here before is a recurve that is actually thickened with a wedge under the backing or belly overlays until it becomes NON-bending, and then has material removed down the middle to reduce mass.
-
Also, I do have a lot of luck with crowned or trapped bows, but in my own experience, simply due to the reduction of width toward the tips, the bow becomes less "trapped" by default. I believe a lighter overall limb is beneficial, but I also believe that the most benefit is derived from reducing the tip weight, say the outer 1/3 of the limb length.
I could be wrong. But Baker's design in the TBB's where he uses flax fiber to prevent lateral flex on a bow with a very narrow outer limb half still has me thinking a lot.
One thing I would like to try is making a backed bow with a belly slat that originates as two narrower slats which warp symmetrically away from each other just a bit. During glue-up, the two halves could be drawn together at the tip of each limb, creating an effect similar to Perry reflex, but laterally, and then the backing applied in side profile. I expect that would create a very stable outer limb, regardless of design. Possibly most beneficial in a R/D with skinny tips.
And I want to see what you do with that bamboo, next.
-
Interesting thoughts and ideas Springbuck. I am afraid one lifetime will not be long enough to make them all come alive!
But let's do our best.
-
Wow, lovely bow, interesting engineering.
I need to study this thread in some detail.
I shall refrain from comment, because one of my key skills is recognising when I don't know what I'm talking about ;D
Del
-
That's a really good skill to have :D