Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on January 22, 2018, 11:45:04 am
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This is my attempt at copying one of Marc's bows. I made one out of OS and it worked pretty well so I decided to make a Boo backed Yew one. I spliced in about the same amount of deflex that Marc did(I eyeballed the picture) Everything in the build went well and I glued the backing on after I had tillered it out to 30#@20. The limbs were about 9/16 tapering to 1/2 thick and 1 1/4 tapering to 3/4 wide at the start of the recurve, then tapered to 1/2. The boo was about .20 tapering to .10, in hindsite maybe a bit thick. I pulled some reflex into it at glueup. After the glueup it was like an iron rod. I could floor tiller it about a half inch. It had 3 1/4" of reflex. I figured if that was too much I could cut a bit off the tips. I went ahead tillering and all was well. It gained reflex as I tillered it and went as high as 3 7/8" before it levelled off. I had to do a minor heat correction to line up the string(twist the limb a touch) after I got it to low brace and then it was fine even with the big hooks. I got it to 40#@ 18.5 and then it started to go south. It developed a tiny hinge and I evened that out. Now I was close to done. Then it was like it decided to take a bunch of set all at once. Within a couple or three pulls it was down to 30# or so at 25" or so. I took it off the tree and now the reflex is 2 7/8". The Yew thickness is now 3/8" tapering to 1/4". I don't see any chrysalling. I've made 3 other BooYews and they worked great but they are all skinny bows. I left this one wider so it might not twist and throw the string. Maybe it didn't leave enough Yew. I've got a couple of ideas for rebuilding it(belly lam) or I could strip off the Boo and start over. What I'm wondering about is whether this design is too much for Yew? Any thoughts or ideas would really be appreciated. Thanks
PS The pictures are as it is now. It had more reflex in the limbs before
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From what I can tell Most of Marcs bows are 2-piece spliced, and this gives him the ability to deflex the handle as much as he wants (within reason) Get more deflex in the handle area, and you may have more success.
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DC my advice for failure is just to try new things it's bound to happen.lol
Seriously though I'm afraid I can't give much advice on your boo backed yew. My very uneducated guess would be maybe boo was to thick but you'd know better than me.
Bjrogg
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That's out of my league DC, but I'm buying the first chalk board I can find. That's an awesome idea, room for notes and everything.
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This one is two piece spliced and I went to great pains to copy the amount of deflex that Marc used. For some reason it doesn't show in the picture. This pic shows it better.
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DC...Sounds like you wanted more draw weight??? and you removed too much wood adjusting to your hinge.I would'nt be disappointed though and would'nt call it a complete failure.I don't see where it says the length though too.
It's fun watching that reflex increase while tillering,and from the start your still only looking at 3/8" set from 3 1/4" to 2 7/8".
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It's 58" measured directly and 64" if you follow the curves. About 21-22" working limb. I just measured the OS one and it has 25" or so working limb. Maybe that's it.
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This doesn't help
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This doesn't help
The picture was taken after everything went west. I haven't attempted to correct it yet. You could almost watch as different sections gave up. That was the last part. I had it pulled and the bow kind of jerked and there was a new bend.
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This one is two piece spliced and I went to great pains to copy the amount of deflex that Marc used. For some reason it doesn't show in the picture. This pic shows it better.
Maybe you were trying too hard? :D
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Marc uses less recurve and more reflex in the actual limbs. Just using where the tips are relative to the back is a poor reflection of what's going on with the limbs when you add big hooks.
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There was originally more reflex in the limbs and I have real problems getting that tight a recurve. I was planning on shortening the tips but when the string stayed on I thought,"What the hey."
I braced it this morning and gave it a pull, it's 30#@27 and the limb that Jim pointed out is way weak. I think what I'll do is reduce the Yew thickness to around an eighth and glue on a new belly, in essence making a tri-lam. I'll try to reduce and tighten up the recurves while I'm at it. That will lengthen the working limb too. Maybe shorten the handle a bit. I could strip off the boo and start again(I'm short of Boo) but I think it will be the same amount of work either way.
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This one is two piece spliced and I went to great pains to copy the amount of deflex that Marc used. For some reason it doesn't show in the picture. This pic shows it better.
Maybe you were trying too hard? :D
Too much deflex???
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Seems to me the real lesson here is that plain old yew just can't quite compete with ocean spray ;)
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This one is two piece spliced and I went to great pains to copy the amount of deflex that Marc used. For some reason it doesn't show in the picture. This pic shows it better.
Maybe you were trying too hard? :D
Too much deflex???
No not that. If you look on the left under my name it says number of posts and then something under that. That is what you should keep in mind :)
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DC, different things work for different people but this is one of the reasons I started going to full draw weight almost right from the beginning. I don't floor tiller near as much as I used to. If I am making a 50# bow I want the weakest part of that limb to be about 70# when I start. Then I know I can go to my full 50# on every pull even if it only moves a few inches. When you are tillering from a lighter weight than full draw weight there is always that risk of surprises as you increase the draw weight. Especially on high stress designs like this one. You really did do an otherwise real nice job on the bow.
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I do much the same. If it was the 30# I mentioned that's just what it dropped to when everything went west. When I tiller I pull to 40# because that's the weight I want.
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Seems to me the real lesson here is that plain old yew just can't quite compete with ocean spray ;)
Sometimes I wonder. :D
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Designs like that can be challenging I know that sinking feeling you are talking about when you sort of feel like the weight is dropping while you are holding it.
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i think when you made the bow wider it changed alot of things and as the weight got lower,, made the boo to thick relative to the belly,, (-P
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i think when you made the bow wider it changed alot of things and as the weight got lower,, made the boo to thick relative to the belly,, (-P
You are probably right on Brad I didn't even think about the bamboos thickness.
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I considered that but then I considered a lot of things. ::) I'm rebuilding it and I'm making the hooks shorter and sharper, about a 2" radius. That will reduce the amount of twisting that I will have to worry about so I can make it a little narrower. Also the only scrap Yew I had for new belly lams is a little narrower so one way or tother it's going to be narrower. Maybe 1 1/8" instead of 1 1/4".
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One of the things I can't change on the rebuild is the boo thickness, at least not the way I'm doing it. So hopefully making it a little narrower and with a couple more inches of working limb due to the smaller hooks I'll be OK. We'll see. I hope I made the lams thick enough.
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your next one will be great I am sure,, (SH)
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I considered that but then I considered a lot of things. ::) I'm rebuilding it and I'm making the hooks shorter and sharper, about a 2" radius. That will reduce the amount of twisting that I will have to worry about so I can make it a little narrower. Also the only scrap Yew I had for new belly lams is a little narrower so one way or tother it's going to be narrower. Maybe 1 1/8" instead of 1 1/4".
It might take you a few bows to nail it down
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This one is two piece spliced and I went to great pains to copy the amount of deflex that Marc used. For some reason it doesn't show in the picture. This pic shows it better.
Your not kidding, can't tell it from the first pics...:)
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DC, I think you mis-labeled your post. There is no failure here. You're attempting a challenging design that is new to you and your sorting it out. Bravo
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Thanks for sharing your experience, even if you consider it a failure, there's a lot to learn from this bow.
I notice that at full draw, the recurves are still not lifting off the string. Functionally, the bow is 4" shorter than it looks and wheighs. You could cut off 2" from each side, and draw-weight wouldn't change a bit.
This also means you're straining the belly more than you'd expect from the ntn length.
In your next try, I'd also put more reflex mid-limb, and give it shorter or less steep recurves. IMO the ideal is to have lift-off before you're halfway your draw.
Joachim
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To elaborate on the deflex in the handle. I personally find there is no set rule, hence the suggestion to keep it flexible. I have had a few people ask me how many degrees of deflex does my bow have. Well I could never answer that question because I don't measure it and I probably have no 2 deflex bows that are alike anyway. It doesn't seem to make any difference in performance, except for when there's a lot of deflex but that's another story. I've been able to coax high performance out of straight handle recurves as well as deflexed handle bows. The thing with the deflex is that you can make a bow a bit shorter for a given draw length, I also happen to like the looks better now. The highly deflexed bows can be made somewhat shorter but then the bow suffers from other issues that affect performance.
As to the hooks. I used to like big hooks, for looks and I thought performance. My thinking change many years ago, even in so far as liking the looks as well. I now prefer small recurves for looks and they have other benefits. First of all it is much easier to tiller a bow with small hooks and there may be a slight performance benefit, that one would be hard to prove though.
Pity you can't thin the Bamboo, it is too thick. Quite frankly I prefer a wood backing for Yew, Maple or Ash
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To elaborate on the deflex in the handle. I personally find there is no set rule, hence the suggestion to keep it flexible. I have had a few people ask me how many degrees of deflex does my bow have. Well I could never answer that question because I don't measure it and I probably have no 2 deflex bows that are alike anyway. It doesn't seem to make any difference in performance, except for when there's a lot of deflex but that's another story. I've been able to coax high performance out of straight handle recurves as well as deflexed handle bows. The thing with the deflex is that you can make a bow a bit shorter for a given draw length, I also happen to like the looks better now. The highly deflexed bows can be made somewhat shorter but then the bow suffers from other issues that affect performance.
Thanks Marc, I found that all very enlightening. It all makes sense to me.
Bjrogg
As to the hooks. I used to like big hooks, for looks and I thought performance. My thinking change many years ago, even in so far as liking the looks as well. I now prefer small recurves for looks and they have other benefits. First of all it is much easier to tiller a bow with small hooks and there may be a slight performance benefit, that one would be hard to prove though.
Pity you can't thin the Bamboo, it is too thick. Quite frankly I prefer a wood backing for Yew, Maple or Ash
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Thanks Marc That clears a few things up. I've only ever used Bamboo as a backing. I've been on the scout for some hard Maple but the two big lumber stores in town don't stock it any more. I'm going to try Windsor plywood but they don't have a big stock here. I've got enough Bamboo for two more tries so I'll be forced to look for something after that. If this one doesn't turn out well I can still cut the boo off and try again. I'm also just about out of Yew heartwood and I can't see myself cutting off perfectly good sapwood to make a backed bow. We'll see how it goes. If this shoots anywhere near 180 all bets are off. :D
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Pity you can't thin the Bamboo, it is too thick.
Can someone clarify something for me? TBB1 says that the outside 10% of the thickness does 50% of the work so on a .500" thick limb .050" is doing 50%. So why does it matter if the boo is a little thick? If the outside is doing all the work isn't the rest of the boo just along for the ride? Why does it matter if that part is Yew or Bamboo?
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I ground the belly down until it was about 1/8" thick and then glued a new 3/8" belly on it. Glued the handle back on and then retillered. I had a bit of the same problem as before. It just seemed to start losing weight very quickly in the last couple of inches. I managed to save it at 35#@27". Lighter than I wanted by a few pounds. It took a bit of set, started out at 3 1/2" reflex and finished at 2". Then I cut an inch off each recurve so it's about 1"reflex now. 64" NTN following the curve. Weighs 359 grams with an 8 strand unserved FF string. Very nice bow to shoot. I'm having trouble finding 350 grain arrows that are stiff enough. I was using a 368 grain 48#bamboo arrow with a 50 grain tip and it broke after hitting the target nock left 3 or 4 times. I found another about the same weight and spine an got a dozen or so shots recorded in about 25 shots. All the recorded shots were in the high 180's. I don't think I got one less than 183. Best of 193 but I couldn't duplicate that today while I had the camera. Success beyond my dreams. I beat my PB by about 12 fps. I really like this design Marc and I will be copying it more. I don't know if the tri lam has much to do with it. I've shot it about 100 times and don't see any chrysals yet.I'm afraid it going to die on me but I'll enjoy it while it lasts. ;D ;D ;D ;D
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Next
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I took this picture before I cut the tips off. It's raining too hard to take another :)
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DC, I believe you are right about the thickness of a backing making no difference--for the reason you mention. I have put thick backings on bows and they worked just the same as thin backings on similar bows. The outside does all the work.
We'll take some flak on this--if anybody reads it.
Jim
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You did a great job on that one!!! I think even Mark will be proud of you.
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DC, I believe you are right about the thickness of a backing making no difference--for the reason you mention. I have put thick backings on bows and they worked just the same as thin backings on similar bows. The outside does all the work.
We'll take some flak on this--if anybody reads it.
Jim
I'll still try a thinner back on the next one. I thought maybe the SG of bamboo was high enough that a thinner piece may lower the mass of the limb but Bamboo ranges from .4 to .8 sg depending on species so that's a guess. I'm also wondering if it affects the sensitivity when tillering although that could be the design or just my ineptness. I'll go even slower next time, especially in the last few inches.
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You did a great job on that one!!! I think even Mark will be proud of you.
Thanks Steve. I was so surprised when I got that speed with a 35# bow. I think luck had a lot to do with it on this one. It's a bit of a dog's breakfast with pieces here and there and some iffy glue lines. I'll make a couple of OS bows like this and then tackle another Boo Yew. I really need some stiff light arrows though.
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This bow reinforces something I have been kind of preaching the last few years. Your bow has about 1 1/2" reflex which is not radical by any stretch, your performance is right there at the top levels. You indicated you backed off when it started to drop weight saving the integrity of the wood. I think this demonstrates that the condition of the wood being fresh is more important than overall reflex and aggressive profiles.
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Bamboo can actually go over 1.0 SG if you only measure the power fiber section.
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Pat, tonkin cane is actually about 1 1/2 times heavier than the heaviest woods
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Glad to see your success with this one Don. The bend looks great and I really dig the looks of that handle!
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I sure wish I knew what I had. It's a 3 1/2" pole I got from a garden center. Like me, I guess, undetermined ancestry.
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Great bow! It just shows determination pays off!
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Excellent work. That braced profile looks very familiar :)
I think Tonkin doesn't grow much more than about 2" in diameter
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Thanks Marc, I appreciate that. I'm bending the limbs on an OS one at the moment. Then I've got some Cascara and Maple to try. This success has put the lead back in my pencil, I was getting kind of wishy washy about this.
I read somewhere that there is Tonkin Cane and Tonkin Bamboo. I guess it doesn't matter, we're at the mercy of whoever is selling it. Pretty tough to tell one bamboo from the next.
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i think when you made the bow wider it changed alot of things and as the weight got lower,, made the boo to thick relative to the belly,, (-P
I don't like having to bother thinning my bamboo down to paper thin and often leave it thick-ish, but yeah, this seems likely the problem. That bow is darn short for one thing, which will make the bending limb thinner back to front. Then those huge recurves make it super stiff, so.....thinner yet. The backing was a stiff one: bamboo. Then you lost some of the Perry reflexing benefits it seems to me, since the bow's reflex was moving all over as you moved toward starting dimensions, etc. That limb had to be quite thin to even bend.
"After the glueup it was like an iron rod. I could floor tiller it about a half inch." and if I had a dollar for every time I said that as I took a laminated bow off a form.
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Can someone clarify something for me? TBB1 says that the outside 10% of the thickness does 50% of the work so on a .500" thick limb .050" is doing 50%. So why does it matter if the boo is a little thick? If the outside is doing all the work isn't the rest of the boo just along for the ride? Why does it matter if that part is Yew or Bamboo?
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This is my understanding. It isn't that the backing is too thick, like theoretically or in principle. It's that IF the backing is very thick, that necessarily means the belly slat is thinner.
Early on in my bowmaking, I made a lot of bamboo backed boofloo and bamboo backed tropical hardwoods like ipe, jatoba, and bulletwood. I had fewer tools BTW, and frequently glued a 1/8" bamboo backing to a 5/8" or 3/4" thick piece of ipe or whatever AND forced it into a R/D posture. Number one, doing so was probably overstraining the belly slats glue surface in compression DURING glue-up, such that the glue line was a backing glued to over-compressed wood.
But number two, by the time I had worked the bow down from "construction beam" stiffness, I most often had a net limb thickness of 3/8" or less. Now I start with a 1/8" backing and glue on a pre-tapered 3/8" slat. BUT, imagine if you started with bamboo, say a highly crowned piece you want to be wide enough so you left almost 1/4" thick. Now your finished belly is only 1/8" thick. That' just not enough balance to hold the shape of the original form.
This is one benefit of tri-lams, BTW.
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I sure wish I knew what I had. It's a 3 1/2" pole I got from a garden center. Like me, I guess, undetermined ancestry.
Almost certainly moso bamboo if it is thin walled. It's fine stuff, just kind of too thin if the pole is on the smaller diameter size.
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Excellent work. That braced profile looks very familiar :)
I think Tonkin doesn't grow much more than about 2" in diameter
That's a bit of a myth. It tends to be cut much smaller but larger poles are available and a slightly ovalized pole acts just like a similar shaped sapling.
Even a smaller pole will back a narrow bow of Ipe.
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Yes, you new bow is very beautiful. Congrats.
There is some bamboo out there often marketed as "tonkin bamboo" because it comes from the Gulf of Tonkin area. It is NOT the same as ACTUAL tonkin bamboo or tonkin cane. If I remember correctly, it is a larger diameter sub-tropical specie and is similar to Taiwan Bamboo. Most large diameter bamboo you see out there that regular people can afford is moso, which works just fine for me, but some moso gets mistaken for the "fake" tonkin bamboo, too.
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Even a smaller pole will back a narrow bow of Ipe.
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This is very true and under-utilized....
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awesome bow!
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Looks good, and shoots well! Congratulations!
Hawkdancer
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very, very nice!
your profiles are just awesome!
Congrats, its a winner.
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The design credit goes to Marc, I just copied his Maple backed Buckthorn as best as I could.
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The design credit goes to Marc, I just copied his Maple backed Buckthorn as best as I could.
Oh well, now I know how fast mine will shoot (SH)
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Excellent work DC.When making those multiple layered lam bows a few more trys can get a person zeroed in on what they should be thickness and width wise.To keep it fresh I usually record it in a notebook for the future after going on to different types of bows.
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It wasn't intended as a multi lam bow. It was a boo backed yew that came in under weight so I ground off most of the belly, glued on another piece and started again.
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I see and you found that it was too narrow starting out and for the next time to be wider to handle the poundage using same materials is my point.Your persistence paid off again Congrats.