Primitive Archer
Main Discussion Area => Bows => Topic started by: gfugal on February 17, 2018, 11:55:12 am
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Okay, so I have seen people say they use a metal strip to keep splinters down when they steam bend recurves. So my question is how do you set that up? How do you get tension in the strip so it is pressing down on the wood to keep the splinters down. Is there a set up where you can use a turnbuckle or something to pull it tight, Like what is shown in this video? We can't do it exactly like them, since a bow is long and has a bulging handle so can't fit it across the entire belly like they did. How do you do it?
https://youtu.be/qQKNOTMAe4w (https://youtu.be/qQKNOTMAe4w)
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Attach the strap to the form and then quickly clamp the strap to the bow limb with appropriate padding to avoid denting. The strap will tighten as the wood is bent.
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For most bends you don't have to get it that tight although it would be nice. The band tightens as you bend it. I just clamp the band to the limb. Make sure to use blocking under the clamps. The free end will get clamped when I clamp it to the form. Assemble it and then boil/steam the whole thing. This will save a bunch of time. On the video it took them over a minute to set up. The pictures are just a mock-up.
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wow, those guys are pretensioning, and waiting to bend a long time.
How do you get tension in the strip so it is pressing down on the wood
don't know if the strip is pressing down so much. think of building a steel/wood laminate such that the neutral plane location is so close to the back, that all the wood is in compression when you bend it.
your job is to clamp up the laminate so that there is no slippage when bending.
if you assemble a laminate that can be boiled together and bent hot, there does not need to be so much force applied
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So it sounds like it doesn't need to be tensioned, only flat on the back. Thanks yall, this has always baffled me.
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Greg, you don't need the steel strap with 'normal' wood which is well prepared.
I have some steel straps, but use it only on problem staves were I do expect splinter lift off otherwise.
Prepare your stave:
1. make the cross section rectangular, this spreads the forces over the whole belly and back.
2. round the corners, this prevents splinter lift of from the edges
3. go with nearly worked down size, let's say a thickness of about max 18 mm.
Btw. the strap makes only sense when it lays surface to surface on the belly (must be flat).
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I never used a strap. But, I may have made 10-12 statics, not exactly a huge test number. All the same the mechanical/engineering aspect of it makes no sense to me and I doubt I will ever try one or feel I need to. Im bullheaded like that.
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Recurves I have never been my thing, I make them now and then but I don't consider myself very good at them. The strap does force the entire limb into compression which does make the process much more fool proof. I just have never been able to get everything set up in place fast enough with a strapping system. I like the one shown here where the strap hooks around the end of the limb, it only leaves one clamping point on the other end. I might try that.
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My solution is to just bend Elm. Nine times out of ten it won't even lift a splinter when bent in a sharp curve.
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I like the one shown here where the strap hooks around the end of the limb, it only leaves one clamping point on the other end. I might try that.
If you're talking about my picture it still has to be clamped. That hook just pulls right out if it's not. Even if it's captured down in a slot it will pull around the end of the bow somewhat.
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My solution is to just bend Elm. Nine times out of ten it won't even lift a splinter when bent in a sharp curve.
Elm, hickory, maple, ash all bend easily. For some reason I tend to get splinters on osage which should be one of the easiest, I usually leave a full uninterupted growth ring above the final thickness that I can scrape away if it lifts splinters.
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My solution is to just bend Elm. Nine times out of ten it won't even lift a splinter when bent in a sharp curve.
I've HAD elm give up a splinter before, but you have to be REALLY pushing it. >:D Elm gives me almost no trouble here, unless I have had the cross section really lopsided, thick on one side, thin on the other.
When I tried this originally, I just arranged tiny C-lamps and a short strap, etc, where I could boil the whole thing in a tall pot I have. Eventually, I just started doing recurves other ways, like belly overlays, and found them easier. Not to mention most of my real recurves are backed or laminated, anyway.
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I tried a few different ways to hold or clamp my tip and metal backer strip. HHB is pretty tough to bend without lifting splinters on belly. This is what I came up with and I love it. It's like having another set of hands when you really need them. I'll let the pictures do the talking
Bjrogg
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How is the strap anchored in the slot?
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DC nothing is "anchored" in slot. The tip has to be thin enough to fit in the slot along with the metal strip. I take limb from steam slide it and metal strip in slot and with leather gloves on slowly bend everything on the caul. The tip of limb pinches the metal strip against angled slot and keeps it from sliding out. I clamp on the steel strip and sandwich the tip between the strip and the caul. It is very fast and simple. My only problem is the end of the caul has split the grain and popped off and I had to glue it back on. I might drill a hole from top to bottom and put a bolt in it. One other thing I'm not sure how it would work for dry heat.
Bjrogg
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Nice technique, BJ.
I, and likely many others, have had same split along that longitudinal grain at end of caul. I have not tried it, but maybe glued plywood scab on both sides spanning split?
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Nice technique, BJ.
I, and likely many others, have had same split along that longitudinal grain at end of caul. I have not tried it, but maybe glued plywood scab on both sides spanning split?
Knoll I'm sure that would be the best. I think a bolt would possibly work to and not be as wide.
Bjrogg
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The strap is self tightening the way I do it
(https://i.imgur.com/yWu23yq.jpg)
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Marc, do you boil/steam the strap and the bow tip?
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Yes both are steamed together
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Marc do you just bend it by hand and hold it? That's a very nice bend.
Bjrogg
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That is really cool mark and simple! In the future that is how I will do it.
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My sentiments exactly :D
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The strap is self tightening the way I do it
(https://i.imgur.com/yWu23yq.jpg)
I'm having a hard time figuring out which way is up and down haha. But I like this method, if only I had a Vice. Do you secure the curved form to the vice before you tighten it, if not I imagine you need a third hand i the allotted time to keep everything in position as you tighten it.
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Now that is a mystery pic. What is on the other end of that bow? I guess a rope tied to a truck bumper.
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I've only built about 4-5 but I have always used dry heat in the process. You have to be careful and patient though or you will get a splinter or a crack across the grain. Arvin
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I have a bigger problem with my curves not being smooth than lifting splinters. Marks method looks pretty fool proof.
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The recurve form is screwed into the vise so it doesn't move. After steaming the tip plus strap for about 15 minutes per each 1/4" of thickness, it's inserted into the opening between the vise and form, set before-hand to be just the right size, and clamped down snug and then the curve is bent in. This of course is done in as little time as possible, which is very little since my steamer is right next to the vise. The other end of the bow, billet in this case, is supported by a stand, of which you can only see the base in that pic, and tied off so I don't have to sit there and hold it till it cools. Also the support is at the same height as the tip so no twist is introduced
As to prepping the recurve before steaming. I work the tip to one growth ring and also into a very shallow D section on the belly side, plus I sand the edges. I find that by doing it this way there is less likely hood of splinters lifting
Now that is a mystery pic. What is on the other end of that bow? I guess a rope tied to a truck bumper.
If you need a truck to hold your steamed bow/billet then you are doing something wrong.
P.S. In case anyone can't figure it out, this picture is taken from above
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(https://i.imgur.com/yWu23yq.jpg)
Often good good solutions are simple ones. Or seem simple in retrospect.
Thanks for the picture!
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I see him, he's up in the top left hand corner!! ;D ;D
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Mystery solved. Thanks Marc.
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I copied Marc's bending jig. I tried it on a rough cut piece of Ocean Spray 1/2" thick x 3/4" wide. No prep, 1 1/2" radius. I got a very usable bend even though there was a knot right in the middle of the bend. I would have had to kerf this using my methods. I think my strap was slipping before and Marc's jig holds tight. So I went ahead on the bow I'm making. Black Locust 3/8" thick X 3'4" wide. Went slicker than owl excrement. It's cooling now. here's a pic of the OS
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I copied Marc's bending jig. I tried it on a rough cut piece of Ocean Spray 1/2" thick x 3/4" wide. No prep, 1 1/2" radius. I got a very usable bend even though there was a knot right in the middle of the bend. I would have had to kerf this using my methods. I think my strap was slipping before and Marc's jig holds tight. So I went ahead on the bow I'm making. Black Locust 3/8" thick X 3'4" wide. Went slicker than owl excrement. It's cooling now. here's a pic of the OS
Wow that's impressive. Glad I asked
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Oh, well. As much as I hate thinking ahead and being prepared, I guess I'll have to build a similar set-up, or at least improve the one I have..
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Here's the recurve. One little splinter lifted on the edge because I took it off the form to soon. A drop of CA took care of that. With the wood sandwiched between the form and the strap it takes a while to dry.