Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on June 04, 2017, 12:09:23 pm
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I spent another day trying to get a nice recurves in an Ocean Spray stave. I used green wood this time. Up til now I've tried dry wood with and without a strap, green wood with and without a strap. Dry wood that I soaked for a few days. Thin wood(1/2"). The belly always fails. I'm trying for about a 3 1/2" radius. OS is very dense wood(SG 1.1 or so). I've found conflicting reports on the web about bending dense wood. I haven't tried different woods to test my methods. Anyone have any experience bending dense wood, Ipe maybe, or any ideas about what I might try. I can fall back on kerfing if I have to but a nice solid curve would be nice.
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I also made this device to help localize the bend to where I want it. I stole this Idea from an episode of "How It's Made" on bending French Horns
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A strip of thin steel sheet on the outside of the bend will help pull it round without splintering, also need to get it from steam to jig double quick, or ideally steam it in situ on the jig. 5L plastic containers are good for allowing you to do that, they keep the steam in, but can bend round the jig like a mini disposable, flexible steam chest :)
Del
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That's the strap I mentioned. I clamp the strap to the wood and then steam the whole assembly. I doubt there is much more than 5 seconds from steam to bend. I tried putting the whole thing in a bag so that it was steaming while I was bending. It was a bit cumbersome and the results weren't any different.
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Your last option might be boiling and using a strap that can be tensioned before bending. THe TBB shows a way to do this with a small turnbuckle.
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Is there a possibility that this wood is just too dense/ hard/ whatever to bend or will anything bend if you do it right?
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I don't think density has much to do with it. Osage is very dense and bends like butter. HHB is less dense than osage and is one of the worst to bend in my experience.
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Osage is.76-.86 SG, OS is 1.1-1.2 but you're right it may not count. After hearing how well Osage bends I've been wondering if it's the soft early wood giving. If there was a little give between layers it would bend a lot easier.
Anyway I kerfed a piece of OS into a 3/16" and a 5/16" layer and it bent fairly easily so that may be the way I have to go. At least I can do that with dry wood. Steaming green wood means clamping it in the bent shape until its dry, maybe 6 months. It makes storing staves very cumbersome.
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Interesting idea about the early wood giving. I thought maybe it had to do with oil content within the wood. Osage is the "oiliest" wood I know of.
BTW I've steam bent green wood and removed it from the caul 24 hrs later and it held it's shape fine. Of course I clamped it down to avoid warping, but the steam bends didn't budge.
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I have had no problem using TBB method of boiling 1/4" of wood per half hour. Metal strap on belly of bow. Start with room temp water and bring wood to boil then start timer. Be ready to bend and have clamps ready, will cool quickly. John
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I sure wish I could send you guys a sample of OS so you could try it. So far nobody has mentioned anything I haven't tried. I'll have to come up with a piece of yew or maple and see how they bend.
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Is boiling an option?
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I haven't tried boiling. I boil splices but not tips because I can clamp splices in the kitchen. I don't have a way to boil in the shop and the kitchen is 5 -10 seconds away. I'll have to figure something out. Thanks
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just boil in pot on stove 30 minutes per 1/4 inch, use metal strap ,will bend like a noodle..must work quickly..I mean get the bend done within 30 seconds of removing wood..I do this and have not had any issues...gut
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It is all about the wood type (assuming perfect prep and technique!). I've never had any experience with oceanspray but have tried steam bending a lot of different types. Most dense tropical woods are a waste of time trying to steam bend. Kerfing is the only option with woods that don't like steam. whereas the best steam bending woods bend like wet noodles when treated correctly. Your set-up and methods will all work on the better steam bending woods. Reserve the strap and boiling for very tight bends.My favourite woods for steam bending are - mountain maple, European ash, cherry (prunus avium) and wych/small leaved elm. Mountain maple being the best :)
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From what I can see you are leaving your tips rectangular. Try rounding the belly into a shallow D section and sanding the edges. I found this helps a lot, along with a metal strap, with HHB. Also follow one growth ring from the tip to well past where the bend will end
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. So far nobody has mentioned anything I haven't tried.
Hey! I mentioned boiling! lol
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Wow, thanks for the tip Marc, especially for bending HHB. I've had the hardest time bending that stuff.
I just got done bending yellow birch for the first time and it was very cooperative. Just thought I'd throw that out there. :)
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. So far nobody has mentioned anything I haven't tried.
Hey! I mentioned boiling! lol
Sorry Pat :D
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I tried Marc's suggestion. Got it all set up and bent the dern thing backwards >:( >:( >:( Try again tomorrow. Meanwhile, I remeasured(more accurately) the radius on my bending jig. It's 2 1/2" not 3 1/2" like I said at the begining. Is that too tight?
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Have you tried different temperatures? Each wood has some temperature that is too high or low. Expirement and see if steam is the right temperature. If the wood gets too hot it will fail in tension because the chemical bonds are decayed. Also there is a radius to thickness ratio that is at the limit of what you can do. This varies according to species. You might make a note of the radius at which the wood pops and design accordingly.
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DC I'm gonna see if I can look back in my pictures and post a couple that might help. HHB acts the same way and I had a lot of trouble at first bending it. Like Marc said round of the edge on belly side to a D profile. Speed getting it ready is so important don't waste a split second. I like how I have the end of my caul now I don't need a clamp and that speeds things up so much. I also like my lid for my kettle. It's just a old aluminum kettle. I cut two slits in the top and bent them straight. I can Stick limb tip in opening belly down. I usually have to steam my HHB at least a hour and even then I really turn the heat up to a good roiling boil the last 15min. I always have my clean leather gloves, clamps, pads and if possible another set of hands right ready. I don't force it I have done it enough now I can tell when it's going to bend and when I have to put it back in the steam. I also use the metal strap. Good Luck
Bjrogg
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The picture on the caul is before I used metal strip but I just slide it in place with the limb. The wood in the kettle isn't really a bow limb it's just a piece of wood for demonstrating maybe this might help made a world of difference for me
Bjrogg
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I purchased a earlax steam generator from Amazon. Works 10 times better than pots and pans and aluminum foil. All woods I've bent with it was like butter
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Success!! Green wood, increased the radius from 2.5 to 4", thinned the limb to 7/16", steamed for an hour and followed Marc's "D" shape. I increased the radius when I found that part of the curve was 2.5". Now that it's all actually circular at 4" it doesn't look that much different. Next will be dry but soaked wood but I'll boil it for an hour instead of steam. I'll let this one dry for a while and then see if I think that 7/16" is thick enough to be static. It wouldn't break my heart if it works a bit. :D
Now I can start going the other way, start tightening the radius to find the actual limits of this wood
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A good source for discussion on this is forums or books regarding making curved handled canes and walking sticks. Those guys really know their stuff.
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I purchased a earlax steam generator from Amazon. Works 10 times better than pots and pans and aluminum foil. All woods I've bent with it was like butter
+1 on that Paul .... :) ;)
DBar
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I have a similar thing. Mine is a clothes steamer but it makes lots of steam.
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That should work well DC what type of steaming chamber do you use?
DBar
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I have a little box made out of 1x4 that I'm using for this bit most of the time I use bread bags or some newspaper bags that I got from my grandaughter when she quit her route. I like the bags because you can bend stuff while it's still steaming and leave it steam for a while after it's bent.
I tried boiling one this afternoon and it failed. I'm going to quit for a while before I start breaking important stuff. I think what I've learned is that if I want 90 degree bends in OS I'm going to have to kerf them.