Primitive Archer
Main Discussion Area => Bows => Topic started by: BigWapiti on March 24, 2008, 01:25:13 pm
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I'm currently working a VM stave that has quite a bit of reflex - about 3" on each limb. I have it floor tillered, but its still holding all that reflex. as I've been tillering and setting on my tree - I started to see how that reflex might be working against me.
There is quite a bit of leverage that I'm working against, getting it to bend. I still haven't tillered it down enough to get it to bend past the handle while staying under my desired weight. I'm concerned that I'll finally get it to that point and lose a lot of poundage.
How do you recommend tillering a high reflex stave? Should I have steamed a lot of the reflex out of it first? I'll post a pic as soon as I can. I was excited thinking I'd have quite a slinger with this one - i'd sure hate to take that zing out by actually removing the reflex.
Whatcha say?
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Big, if you can keep about 1 1/2" of that reflex you will be in good shape, if you loose all of it the wood will be crushed pretty go but still make a decent shooter. When I have a highly reflexed stave I either rely on long string tillering till I hit a point I can brace it or just keep floor tillering till it feels about right to brace. A reflexed bow has quite a bit of tension on it just getting it braced and can fool you eye if you are not used to them, just study how it is bending as much as you are studying the shape of the bow as you build it. The shape can look right but it might be bending too much in one area. Steve
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Thanks Steve,
Sounds like my concerns are in the right line of thinking. My worry is that as I tiller her down to brace, using the long string or floor tiller, that I'll reach a point that to get it to brace will then reverse the weight. I really have no way to try to better explain this..... sigh. let me try again...
right now, using the long string on my tree - If i pull just an inch, it quickly gets to my target draw weight. If I keep tillering, it continues to bend more while staying under my desired weight. BUT, I have a feeling that I'll soon reach a point where as the reflex comes out of her, the weight will drop VERY quick, creating a very lightwt draw bow.... man this is hard to explain. I think leverage comes in to play with the reflex. I have a tough time keeping from over drawing during tiller for fear of that break even point hitting fast.
I think I'll give up there :) and see if its making any sense to you.
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Try badgers mass theory, the weight of the bow will help you know what to expect and when.
This is the best way I know of short of experience.
Also pay attention to the limb thickness you've made a few other bows from VM so you should have an idea
of what thickness you need to be at.
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yeah, the thickness is what has me concerned. I started realizing that I'm already below "standard" thickness for a VM of this draw weight. I suppose this is how I could have better explained my delemma. It seems already to a point of limb thickness where it should be bending to draw weight (50#) and I'm not even getting it to bend to brace yet.
Mass theory? I'm all ears!
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http://www.primitivearcher.com/smf/index.php/topic,5127.0.html
Here's a thread badger started explaining it somewhere in there is a excel spreadsheet.
He also has a chapter in TBB Vol 4, good reading.
For instance for a stiff handled 50# @ 26" 68" NTN bow with no initial reflex it should be in the range of 20 to 21 ounces
and that is irregardless of the wood type, you just adjust the width based on the woods ability.
Same bow as above with 3" of reflex and the mass jumps to 22ounces, that much reflex puts more stress on the limbs
therefore more wood is needed.
Its a great tool, a little confusing at first
but stick with it and it gets easier
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I always had problems with highly reflexed steves, tricky they are for sure, easy to go under weight, ...did that before, I have a 6" reflex stave from Gordon, it's worked down quite a bit, but can't find the courage to start bending it,...it scares me.
I will be following this thread to gain some tips from the exerts , for sure ;)
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Vine maple is about as extreme an example of tension wood as they come. It might look straight when you cut it, but some staves will just curl right up during the drying process. 3-6" of reflex is fairly typical . But it is quite managable if you understand the wood. Much of the reflex will pull out during tillering, mostly on the short string. The way I deal with the reflex is try to get the bow on the short string sooner than later. That's because the tension induced reflex will make the bow seem heavier than it really is and when the reflex finally gives way (and it will happen almost all at once) the bow will drop in weight considerably. I try to get the bow on a short string when the tips are moving about 12". Obviously then it is really important then to try to get your tiller as squared away as possible before you subject the bow to the rigors of the short string. I also exercise the crap out of vine maple after every wood removal - my goal is to try to get the wood to give up the reflex while I still have enough wood to hit my target wieght. But don't get carried away and pull too much weight or the bow will eventually take a set. I don't pull more than 5# over target while I still have reflex, and then no more than target when the reflex is largely gone.
Oh, and don't bother trying to steam out tension induced reflex because it will just come back when the wood dries.
Hope this helps.
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Thanks Gordon, it does help. But the issue I'm finding with this particular stave is that 12" of pull seems like a long way off yet. I can't even get a couple inches and my limbs are already way thinner than I would expect. I can't seem to think that I have a stronger piece of wood, I think its more in the reflex. I put this stave in a jig to hold it from taking on too much reflex - not even sure it worked - as you say, VM seems to want to flex to where it wants, no matter what you do to it.
I'm just not sure how to get it to 12" of pull, let alone to flex past the handle. Crazy stuff, but I guess thats why I'm loving it.
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How thick right now is the wood at the start of the fades. Is the bark off or on?
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Bark is off, its been off since just after it was cut, which was this past Fall. I had only split it after taking the bark off and just recently roughed it out and started tillering. I'm not at home, but I believe the thickness at the fades is somewhere around 0.7" - which from my two other VM bows, is about right on for the 50# class wt bow (your thoughts?).
I really need to show some pictures, but having had my home laptop crash - I've not been able to get pictures from my camera.
((which, btw, is why I haven't finished publishing your hazelnut build-along yet.... the laptop crash took all that work away - I'm working to recreate it though - pout))
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Yes, that should be about a 50# bow. You might try hanging a 50# wieght on it for a few hours - you have to pull that reflex out before you take off much more wood.
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Thanks for the idea Gordon.
I like it - I'll give it a try. I might start with hanging a little lighter weight since my target is 50# - or do you think I should be worrying that?
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50# should be fine, but put a stop under it so the limbs are not overstressed when the reflex begins pulling out.
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Will do - I'll post back to let you know how it works out.
hmm, any thoughts on how much reflex I should try to pull out? That is, how far should I let the weights go before stopping them? If I want, say, 2" of reflex out, would you double the distance to drop? or make it 2"?
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Put the weight on and see how far it goes down. I'm surmising from your description that the limbs will be about straight or slightly deflexed. Then put a stop a couple of inches below the weight and see what happens.
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You have 3 inches of reflex. I would long string tiller out to 13 inches ( I usually go to 10 inches) of string movement looking to get 5# over target weight. Good tiller, of course. Then I would string it up with the short string. Remember that reflexed staves show high early draw weight when strung and tillered. If at any time you feel the stave is getting to thin then begin to remove wood from the width. See Bow Making Directions on my site. Jawge
http://mysite.verizon.net/georgeandjoni/archer.html
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Well, I had time to give this a try today - put a strap on each limb about 18" up from the handle and hung 50# from it for 3 hours. No change. Then hung it again for another 3 hours. No change.
Hanging 50# on it doesn't seem to bend it into position at all. Strong wood!
First pic is the bow just sitting in the tree.
Second pic is my rig for hanging the 50# weight (were you thinking something different?)
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Mike, Your dog just told me he thinks you got 6-7" of reflex. ;D That is a bit of a challenge as getting this to come around might make it lighter than you want. It would have an interesting braced profile. I'm sure Gordon will tell you which method will reduce the reflex best.
Rich-
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yeah, no kidding - I'm thinking of turning this one around and just stringing it up backward. It seems to want to bend that way no matter what I try. :)
I think I need to try strapping these to a board after splitting the log w/ the bandsaw. They hold a lot of reflex.
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Try hanging the weight from the tips. If that doesn't help then just start taking off only a little wood at a time (with a scraper) and exercise the h*ll out of it between each session.
These highly tensioned vine maple staves have a lot of spirit - you gotta break 'em before they start coming around...
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Thanks Gordon - I'll put on the spurs and give it a bunch of 8 second rides to try to tame the beast (sorry, no coffee yet this morning -heh)
Having the weight on the tips had it trying to 'break' at mid limb instead of across the board -- I suppose that means I have a nasty hinge that'll show its face once I do get some of that reflex out of it. - but I do have another idea, using your 'break it slowly' suggestion.
Actually, another question - any suggestion on how to prevent so much reflex on VM staves? Have you had much luck strapping them down after roughing them out? Seems that no matter what, that reflex just starts up as soon as its removed from the jig. Thinking 'out loud' here, maybe I need to have a little more patience and keep them strapped longer.
Whats life without a little challenge.
-m
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Big Wapiti, looks like youv'e been given some sound advice. Another alernative might be to consider what I did with the syringa gull wing bow. It had almost the exact same start. I just heat deflexed the limbs right at the fades. Here are a few pics. Keenan
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any suggestion on how to prevent so much reflex on VM staves
Avoid harvesting vine maple that is leaning heavily without support. If you tie it down to prevent it from reflexing, it will just curl up when you untie it.
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Thanks Gordon - you caught me. The VMs I've been harvesting were of the 'bush' type and having a lot of lean to them, there must be quite an amount of tension in the wood. Especially to hold that heavy trunk up, particularly under snows. The point you make is a good one - of the two VM bows that I've completed successfully, those were cut from more upright standing trees. Thanks for that - good advice.
Keenan, thanks too for the advice - I'm going to give it another try - but I've not had much luck steaming or heating reflex out of vine maple. Its worth another American try though; not like its going to hurt anything, except my pride. My neck and shoulders are already sore from making shavings. :)
Thanks again guys.
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One more thing. Be very mindful of limb thickness while you are removing wood. That's because it is hard to detect hinges in a heavily reflexed stave until it is too late.
Good luck!
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Keenan has it right, work on the fades...
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Keenan,
You say you heat deflexed it. I'm going to build a jig as you show and give that a try. I've always just put the handle in a vice and hung a weight off the limb, using heat until the weight hit a stop. But maybe forcing it via clamps is a better way to go.
Do you heat it up first, then work quickly to get it into the jig? Or are you applying heat while its in the jig?
Last question is - when I use my heat/vice/weight method - I don't use weights that are heavier than my desired draw. Thinking that more weight is like over drawing when its on the tree. When clamping, how do you know if you're putting too much stress (compression) on the wood?
Come to think of it, I'm hanging 50# off my limb, because my bow is to be 50# -- BUT, that still means my limb is getting 2x the weight it would get a desired draw wt.
Am I completely overthinking this???
But if I am, why is it so important then, not to draw over weight while tillering?
Oooh, soo much thinking for a monday. :)
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Mike,
If you are going to try to bend out the reflex at the fades I would steam the area first and then clamp it to a form. I've not had much success using dry heat to bend vine maple wood a good deal - it tends to crack. That said, I expect that the reflex will reappear within a week. At least that has been my experience. But give it a go - you've got nothing to lose...