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» Trad Gang.com » Main Forums » The Bowyer's Bench » Robin bamboo build along (Page 2)

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Author Topic: Robin bamboo build along
robin
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Hi sam great build along, you really want to be careful at the node area as this species of boo the thickness on the left and right of the node area is normally one side thicker than the other during the growth cycle of boo.
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inksoup
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play it again sam [Smile]

you are good on this...

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these are not the droids you are looking for.

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Sam Harper
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Thanks for the tips, Robin!

Yeah, I guess it would've been better to put a shim in there instead of just filling it up with epoxy. Oh well. Today, I cleaned it up on the belt sander, and this is what it looked like:

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It's got a little bubble in there, but that's okay. i'll fill it with 5 minute epoxy.

I made a mark 1 inch from one end of the splice. That'll be the middle of the bow. That way, when I cut my arrow shelf in about 1.25" above center, none of the splice will be in the site window. it'll all be under the handle.

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Then I put the bamboo on top of it, lining up the center of the bamboo with the center mark on the Osage. I made a mark on the Osage at both ends of the bamboo and cut the Osage to the same length.

Then I decided to do something I've never done before. I wanted to taper the Osage before putting in the curves and gluing it up, and usually I'd use a bandsaw and a belt sander for that, but this time I decided to try the Dean Torges method that he shows on his video, "Hunting the Bamboo Backed Bow." He uses a jointer and makes multiple passes, progressively starting each one closer to the handle, to get an overall taper.

I don't want to go into all the details of the math, so I'll just tell you the bottom line of what I did. I made three marks on either end of the Osage that were 8-3/4" apart. I set the jointer to 1/16", and I made three passes. The first one, I started at the first 8-2/4" mark. The second one, I started at the second 8-3/4" mark, etc. I forgot to take any pictures, so I made an illustration so you could visualize what I did.

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That basically reduced the thickness by 3/16" from about 26" to the end.

I didn't like this method, though. I don't know if the problem is me, the jointer, or the Osage, but it was a bit chippy. Check out this big chip it took out of the end of one end of the Osage.

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It's not a deal breaker, so don't stress out. :-)

My bamboo was just a smidgeon more wide than the Osage, so I made it more narrow, being careful to remove the same amount from each side so the tips would stay lined up. Then I noticed my Osage wasn't straight, so I used the string and squeeze clamp method to make center marks on each ends that lined up with the center of the handle area.

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Then I lined the bamboo up with those end marks and traced a line kind of wide of the bamboo, and I cut that out with the bandsaw. I thought it would be better when I do those recurves if the bamboo is already straight and centered. I don't know if makes a difference or not.

Speaking of doing the recurves, this is the same form I used on the last one, and it worked out, so I'm using it again. I made this out of a 2X6.

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I put an aluminum strip next to the Osage, clamped the tip end to the form, and put another clamp on the other end of the aluminum.

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That way, when I start to bend the Osage, that aluminum will be pressed tight against the Osage, preventing any splinters from lifting. Also, the aluminum stays hot when you heat it up, and it conducts that heat to the Osage, keeping it hot while you're bending.

Some people leave their Osage kind of thick when they do this so if it lifts a splinter, they can just rasp it off, and still have plenty of thickness left. I saw one of J.D. Jones' static recurves at OJAM earlier this year. His Osage was thick, and his bend was almost 90º. It was such a sharp bend, the back of his Osage was wrinkled from the compression. So you can do some crazy stuff. I haven't tried anything that radical.

Anywho, I used my heat gun to heat it up a little at a time and apply clamps until I got the whole thing clamped down. Of course I had to remove that one clamp so I could get it to go down all the way in the end. Since my Osage was pretty thin, it didn't take long. Just a few minutes. I can't explain when it's ready to bend. I just apply a little pressure, and when I feel it begin to loosen up, I apply a clamp. I guess it's the sort of thing you have to do to figure out. I always cringe a little when I'm applying the clamp because I'm afraid of breaking it. That would be such a disappointment!

I got it all down without any cracking noises, though.

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It helps if you have that form nice and rounded with no sharp spots. You can feel them by running your finger along the curve, so just file them away if you feel them.

After I get it all clamped down like that, I put the heat gun on the aluminum a little more in hopes of loosening it up a bit so it'll hold the curve better when I unclamp it. I'd like to have as little spring back as possible. The longer you leave it clamped up, the better. I'll probably unclamp it in a few hours and do the other end even though it would probably be better if I left it over night.

I don't know whether I'll post more tonight or wait until tomorrow.

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There are strange things done in the midnight sun by the men who moil for gold.

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soy
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This is a good one ....thanks [archer]
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Sam Harper
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I decided to leave it clamped up over night, and this morning I barely got any spring back at all. Maybe I'll end up with a recurve this time. I had intended the last bow like this to be a recurve, but so much curve came out by the end that it wasn't really a recurve anymore.

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I just clamped up the other end, so I'm going to wait until the end of the day to unclamp it and continue.

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There are strange things done in the midnight sun by the men who moil for gold.

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Ice Mike
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I have a newb question for you Sam..

Would it have been easier and more prone to keep the shape if you would have heated it---did a preliminary bending run leaving it on for a few minutes--then take if off the form and spread smooth-on on the osage and the boo and then re-heated and immediately clamped them together to the form and let cure?

I'm not sure if this would be better or not, or if this would pose other problems elsewhere..just curious to get you thoughts on my methodology..

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Sam Harper
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I definitely would've held its shape better if I had glued the bamboo to it at the same time I was bending it, but then what about the other end? You have to do the glue up all at once because if you try to glue it up in parts, it's not all going to lay down smoothly because the smooth on that gets pushed out of the joints will harden, leaving a bumpy area that you can't smooth out.

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There are strange things done in the midnight sun by the men who moil for gold.

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Sam Harper
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After heat bending both ends of the Osage, I heat bent the bamboo the same way. The last time I made one of these, I didn't heat bend the bamboo (at least I don't think I did), and during glue up, some of the curve came out. I'm guessing part of the reason was that the stiffness of the bamboo pushed it out. So this time I pre-bent the bamboo.

You have to be careful with bamboo if there are nodes anywhere in the bend because the node will be stiff, and that'll cause it to want to hinge on either side of the node and possibly lift a splinter. One way to deal with that problem is to put shims between the nodes. Another way is to put clamps on both sides of the nodes where you expect it to hinge. Just be careful.

I didn't have that problem because my nodes were far enough back from the tips that they weren't part of the curve. (Thanks Robin!)

Another problem I've had with heat bending bamboo is that it'll warp a little, and the flattened part will no longer be flat. I reckon my bamboo wasn't dry enough when that happened. One way to deal with that is not to flatten it all the way before bending it. Then, after you bend it, you can flatten it some more, and if it's bowed a little, that'll take care of it.

I also pre-bent my wedges. I'm using wedges 7.5" long on the tips because I want them to be kind of stiff. I don't like working curves in all wood/grass bows because over time they work themselves out. The last time I made one of these, I used walnut between the bamboo and Osage for contrast.

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This time I used Osage just because I had already made them and they were ready to go. I'm lazy that way.

I didn't leave the bamboo or the wedges clamped up nearly as long as I left the Osage, and you can see the difference in how well they held their bend. The bamboo barely held any bend at all.

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It's too late to do a glue up. Maybe I'll do it in the morning. It's ready to glue up, though.

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There are strange things done in the midnight sun by the men who moil for gold.

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J.F. Miller
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you might consider bending all three pieces together. and boiling them instead of dry heating. they will retain their shape better, but the downside is that you have to let them dry out again before gluing.

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"It is easier to fool people than to convince them they have been fooled." Mark Twain

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Ice Mike
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quote:
Originally posted by Sam Harper:
I definitely would've held its shape better if I had glued the bamboo to it at the same time I was bending it, but then what about the other end? You have to do the glue up all at once because if you try to glue it up in parts, it's not all going to lay down smoothly because the smooth on that gets pushed out of the joints will harden, leaving a bumpy area that you can't smooth out.

Thanks for the insight Sam and pardon the dumb question!

Carry on sir! Looking great!

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Sam Harper
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I went back and forth on whether I should have a power lam or not. On the last one-like-this, I used a power lam, but it turned out to be unnecessary. Look how much the Osage tapers from the handle to the end of the power lam here.

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I think I could've gotten away without a power lam. But the starting Osage is slightly thinner on this one than on the last one, so I figured it's better to have a power lam and not need it than to need it and not have it. Besides, it looks good, and going with tradition, I decided to make one out of walnut this time, too.

The original power lam was 15", but I made this one 13.5" because it fit more neatly between the blade and the throat of my bandsaw. I'm going to make the glued on handle part 9", so that power lam will extend 2.25" past the handle on either end.

Here's the power lam all nice and tapered so you can see how thin I got those ends.

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As usual, I didn't take any pictures of the glue up because I had glue on my hands and didn't want to handle my iphone. But basically, I used Smooth On and put glue over all the surfaces, wrapped it in plastic wrap, put masking tape around it in a few places to keep it from sliding around, then put squeeze clamps on it.

I'm not using a form. It's resting on a couple of pieces of wood near the middle, and I'm letting gravity give it a little bit of deflex. Having some deflex will make it more stable. By "stable," I mean less likely to have the tips twist one way or the other when it's under tension, which is harder to prevent with recurves than with longbows because recurves are inherently less stable than longbows, and by "stable," I mean. . . whoa, deja vous.

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Can you see that string? I thought maybe if I put a little c-clamp on each tip and tie a string between them, I could keep more of my curve than on the last bow. Here's a close up of the c-clamp.

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I used a broken arrow piece as a tourniquet to tighten the string.

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I put that in the hot box, and I'm going to leave it on for 4 hours and probably not take it out until tomorrow or late tonight.

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There are strange things done in the midnight sun by the men who moil for gold.

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Sam Harper
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All I did today was clean it up a bit with the bandsaw and belt sander. Check how much curve it retained compared to the last one.

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I'm pretty pleased with that. Now, if only the tips line up. I'll leave you in suspense about that for now. [Razz]

I also went over the back and pealed off all the glue from the bamboo with a pocket knife.

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It comes off pretty easy because the rind is waxy. I'm going to take the rind off after I glue on the handle.

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There are strange things done in the midnight sun by the men who moil for gold.

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Sam Harper
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Oh, here's one more picture to show it has a slight amount of deflex. Gravity probably wouldn't given it more deflex if not for the string. But it'll probably gain some deflex during tillering.

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There are strange things done in the midnight sun by the men who moil for gold.

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takefive
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Looking good Sam! Your bow's going to have some sexy curves, too [Smile] I'm always thrilled when reflexed tips hold as well, especially after the bow has been shot in.

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It's hard to make a wooden bow which isn't beautiful, even if it's ugly.
-Tim Baker

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bigbob2
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Watching with great interest Sam, looks great
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