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Bending wood question

1K views 13 replies 8 participants last post by  unclearthur 
#1 · (Edited by Moderator)
I recently bought a cheap globe, and I'd like to make a wooden stand for it, something like:
World Map Globe Gas Astronomical object


The glove is 12" diameter.

I'm trying to figure out the best way to make the curved piece that directly supports the globe. I could cut it out of a large piece on a bandsaw ….but I don't think the grain direction would look very nice on it, and perhaps it wouldn't be very strong either.

It seems to me the nicest way of doing this would be bending some strips of wood, but I've never done that before, have no special gear, no special woods or any idea if it is reasonable radius to achieve etc…...

Any thoughts on how to do it, or alternatives would be appreciated.

Thanks
 

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#2 · (Edited by Moderator)
If it's a 12" globe, I would get my compass set up for 12 1/4"OD. get a board 10" wide x 14" long. Find center on the 14" length. On the 10" side, mark 2" up from the bottom crossing the center line creating your start point for making the yoke? for the globe. Mark the 12 1/4" half circle, starting at the 2" mark, in this case, the inner diameter of the yoke. Whatever thickness you want the yoke to be, adjust the compass to allow for the thickness of the yoke. Save that dimension. Make the second mark for the outer diameter of the yoke.

When you have all marks done, use a square where the the circles intersect with the 2" line. That's your start point for cutting. Take the wood to your band saw, and as carefully as possible, cut along the lines not deviating or wandering. Cut on both lines. Discard the thin strip.

Whatever you came up with on the difference between the inner and outer compass setting, you will need to cut strips that will make up that distance. Stay at or under 1/8" for the strips to be able to bend under clamp pressure.

If you want a 3/4" wide yoke, cut your strips from 7/8" material or wider. Cut the length about 14-16" long. The half circle jigs should be the same thickness or pretty close. Glue it up, using 3 clamps, clamp from the center, and draw the inner circle into the outer circle. If you cut the lines cleanly, the jig will pretty much self center as you are drawing it together.. Twenty four hours later, release it from the clamps, strike it on a table surface a couple times. If it doesn't come apart, you did good…...... Wood is your choice, but stay away from well figured woods. ........... Jerry (in Tucson)
 
#3 ·
I've made a couple of projects with steam bent parts. I just used a wallpaper steamer and a 6" metal duct for the steam chamber. The biggest problem is dealing with spring back. No matter what you do, you will get some spring back so you have account for that in the design. A glue lamination with thins strips requires less equipment and spring back is usually less but you will still have some.

Another option would be to glue up multiple straight segments with angled bridle joints to form a rough arc and then cut the final semi circle bracket on the bandsaw.
 
#5 · (Edited by Moderator)
Wow, thanks all, thats very helpful. Great explanation Jerry. I've done small projects with splines sort of like that before, just on a much smaller scale, but I hadn't made the mental connection with the curved "yolk".

On the glue, I have the West System 105 epoxy .... would that be OK? I've mostly used it for filling cracks before? Curious, though, as to why normal (Titebond) glue won't work well ….. its all long grain to long grain …?
 
#7 · (Edited by Moderator)
On the glue, I have the "West System 105 epoxy…. would that be OK?
- unclearthur
West system works very well… I use it to laminate sailboat tillers. I also add 403 microfibers, as it is an excellent gap filler - but for a small project shaped like yours, you should be fine without any additional fillers.

Cheers,
Brad
 
#8 ·
This is sort of a strange question, but how best to spread the epoxy over so much surface area?

ie - layering the strips with 100% glue coverage is a fair bit of surface area, and I would think you need 100% coverage or it might de-laminate. It would be easy to cover with white glue, just spreading out with a finger, but epoxy is sort of a different (and more expensive) animal …...
 
#11 · (Edited by Moderator)
Normal white & yellow wood glues will not hold the shape over time.
- rcs47

Damn….ya mean I ve been doing it wrong for nearly 30 years?

- Tony_S
I did my first bend with Titebond back in '78. It was a stool back that I set up for Rattan. I used 8 strips of 1/8×1 1/8" wide Red Oak. Today, that stool is just as sound as it was the day it came out of the jig and clamps.

The problems I had later was trying to use some 1/16" strips that I completely covered with glue. The water in it caused the wood to wrinkle, twist, and other things wood does when wet, but when clamping. it leveled out and looked pretty good when done.

Unclearthur, you could also do this using a circle 12 1/4" OD and use a good ratchet strap as your clamp. Forgot to mention that in my first reply. The only precision this way is the circle…......... Jerry (in Tucson)
 
#12 ·
I've used TBII successfully for some fairly tight curves. I bring the maple laminates down to around 5/32. No steam required. Dry bent around the form and glued. Ended up with a 3/4" X 1" X 18" piece.
 
#13 ·
BTW, in general air dried wood is easier to bend if you can get it. The heat used in kiln drying sets the lignon and makes it stiffer, though the thinner the strips, the less of an issue it is. Kiln dried wood is also more likely to spring back.
 
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