Primitive Archer
Main Discussion Area => Bows => Topic started by: upstatenybowyer on June 04, 2018, 06:46:09 pm
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I'm new to this type of bow and I'm having some problems. Assuming the width runs parallel for half the length of the limbs, then tapers to the tips, here's what I don't understand...
-the amount of wood removal necessary to get the outers bending seems crazy. Am I just feeling way more early weight than with other types of bows? If so, when does it start to give?
-with the inners in deflex from the splice, I don't want them bending much so I leave them thick. Is this correct?
I've broken two so far and I'm starting to get a little frustrated. (--)
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One of the biggest problems with this type of bow is the amount of bend and the degree of the bend put in close to midlimb, it needs to be very gradual and increase as it nears the tips if not it is a nightmare to tiller out. Put your bow on a short longstring and test it to desired target weight study the bend carefully. If you have kind of a sharp bend like I described close to midlimb you just might break the bow trying to make it go away. It will remain part of the profile and give a very high false sense of draw weight. If you are having problems seeing the proper bend just make sure your thickness tapers stay nice and even and don't wind up with a thin spot right in the middle of the bend. Good luck.
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Old Roy that used to post on here did a build along, and he has videos on YouTube as well with them on the tree. Roy Painter. They will help a bunch
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I'm not sure if it will help or if I'm even right but starting on the short long string, before it's braced I tiller it where ever it needs it to get the limbs straight except for the last 4-5 inches. Should have that Egyptian look. Then I proceed as if I was trying for a bit of an elliptical tiller. The first couple I did though I just picked one of the bows that Marc posted that I liked and I printed out the unbraced, braced and full draw pictures and hung them on my tillering board. make your bow look like the pictures :) :)
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Bayou Ben on here has made a lot of really fast D/R wood backed bows , Pig hunting type bows maybe he will chim in , he has done a lot of exspermenting with different profiles !
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Thank you guys so much for chiming in. Badger, you described my problem exactly. Maybe I need to redesign my caul. I think I must have too dramatic a bend midlimb. :-\
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I've been thinking about this and I'm not sure if what I'm doing is right either. I've made about a half dozen of these and have been pleased with the result but I'm not sure I'm doing it "right" for the shape. Am I right in assuming that it should bend the same as a straight bow but allowing for the reflex. Say I took a straight bow, traced the back unbraced and then pulled it to full draw and traced the back again. Then every six inches measured the distance between the two lines. Then do the same thing with a d/r. Should the distances be the same? Should a d/r be elliptical or circular? Why?
On another note, Upstate, are you confident with your backing? Where did it break? In the shop isn't close enough ;D ;D
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Here's a picture of my caul. I can measure it every few inches if you want. All the notches are for lumps and knots on the staves. I use 5 min epoxy and scraps and fill them when there gets to be to many.
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Thanks Ritchie for the mention, but I'm in no way an expert on the subject. I've made maybe a dozen of these styles in the last year. It's just where my bow making journey has taken me... Anyway, I agree with Badger's points. Anything too drastic in one spot is a nightmare, no matter how you intend to tiller it.
If you have a mild reflex deflex, you can more or less tiller it like normal just allowing a little more bend in the deflex area and a little less in the reflex area.
Anytime you add more than a couple inches you are taking a shot in the dark as to what you "expect" the tiller to look like. There's just too many variables to predict what the shape should look like, imo (unless you are very experienced and know what shape you want it to take to meet your requirements; Marc St Louis comes to mind). So you want to make sure your board/stave/lams are bending the way you want it before you induce R/D. I do this by very precisely measuring the thickness taper and making sure my width taper is spot on too. I know that it will bend the way I want it to because my taper is near perfect. If you don't want to precisely measure thickness taper or you are using a stave, you can spend the time at floor tiller and make sure it's bending near perfect before you glue the back on or heat in r/d. It is basically pre tillered before your glue up. Then tillering will consist of evenly taking off material from the entire limb to even it up and reduce to your intended weight, and letting the shape be whatever it wants to be. You did most of the work pre-glue up.
After breaking a few and having a few take a lot of set, this method has worked for me. The less I mess with the thickness taper the better the bow comes out.
I have broken a least a couple trying to get the "stiff" outers bending. Not a game I play anymore.
Oh and a precisely pre-tillered stave/board will bend more evenly when inducing r/d.
Hope this helps.
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What Bayou bend said about precisely building your tapers and the r/d shape will come out right is one of the most important things when making these bows or any bow for that matter that isn't going to be a straight bow.
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That makes a lot of sense. I guess I've been hesitant to bend too much without the backing on. I've used this method with sinew-backed d/r bows, statics, set-back handle bows, ect. and it always works.
So you guys would recommend...
1. preparing the billets with careful attention to thickness and width tapers
2. splicing into slight deflex
3. pre-tillering to get an even bend
4. heating in gradual curves
5. gluing on the backing
6. finishing up the tiller
?
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I think the first thing you do it find out exactly what shape you are going for. If you are unsure about what you have selected post it here and verify it is a good profile. Once you have the shape you want nailed down don't settle for anything less in your form, pretillering the bow will give it the right shape in the form. Unless you are doing recurves you should be able to get the shape you want without heat. You may have to heat the handle area if you are deflexing.
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I glue in r/d, but your method looks good to me. I'm interested in what shape you are looking for as well.
I remember one of the last bows you posted had a great r/d shape and came out really nice. So nice it makes me think you should be giving me advice....
The 1st picture shows what you SHOULD NOT do, if you didn't already get the concept. The reflex was all in one spot and was a nightmare to tiller. I don't know how that bow survived.
The 2nd picture shows the gradual curves that I now look for.
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Ben, I looked at the first pic before reading your comment and was trying to figure out a tactful way of commenting that it was a perfect example of what not to do. Thanks for posting that. This is the number 1 most common mistake made by guys new to backing r/d bows. This is what I imagined he was talking about and what I based my first comment on.
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The reflex in mine wasn't all in one place like that first pic, but it was was more abrupt than the second. I think my main problem was too much reflex in general. I traced the shape of an FG d/r bow to make the caul and FG can do things that wood alone cannot.
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I routinely used to put my tips between 4 1/2 to 5" behind the back of the bow. Now I normally go about 3 1/2.
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Here's a pic of the old caul I was using and the new one I'm making after starting this thread. I really tried to make the curves more gradual and the reflex less dramatic.
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That first caul doesn't really look too bad, I would have extended the straight part of the limb maybe a couple of inches more.
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Yeah, I think you can pull off that 1st one if you follow the steps you mentioned. Having an idea about final thickness of your bow will help too. It's hard to maintain even taper when you have to remove a lot of wood from a curvy r/d bow.
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Interesting. I've gotten pretty good at estimating my final thickness taper prior to tillering when I'm building a self-bow, but I feel like it's a whole other ballgame when making one of these wood-backed numbers.
Is that true?
In other words, do you need less thickness with a wood-backed bow because the back is completely flat and thus tension is perfectly distributed across the surface?
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I think it is but not a lot thinner. I just looked a some of my bows and the backed ones may be 1/32" thinner, maybe a bit more. It's hard to say because some are wider than others and that skews the look.
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Yeah I think you'll have a little less combined thickness than a stave by itself, but I don't think it has to do with the back being flat. A lot of guys that I've seen taper their backs, including me. It's the overall taper that gives you the bend; not where the taper is located assuming your back and core are similar strength woods.
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Just realized what you meant by the back completely flat comment; yeah that seems logical. I never really thought about it as most of the bows I've worked with recently have been backed.