How to bend wood like this - Outdoor furniture project

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Originally Posted by Maurice Mcmurry

Here are some forms with access to both sides. I will try to dig the round window form out of the shed. It is set up like a BBQ rotisserie.

Attachment 518947 Attachment 518948

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Interesting, Maurice. I could have done it that way, but I was building to mimic the setup that Australian guy had on YouTube that he removed right as I needed to see it.

I thought that the winch approach would work, and it still might, but straps I think will work better for my particular bend. And I agree, a caul is a must. Plus clamps (probably going to use a couple of parallel clamps with wood boards) to help hold the straight parts.

Would have been tremendously easier just making the making the curved part on the jig, and attaching it to straight sides. Might have to go with that.

You might be able to use shorter "lifting straps" with your existing winch to do the deed in the same way as with just heavy ratchet straps.

I learned some about the forces required to make bent laminations from the video about the making of Stienway pianos. "Work around from the center outwards" . The bending and clamping is shown right at the begining.

https://youtu.be/jAInt7hIZlU?si=WUKDhI0Opvke4C8A

The Steinway factory tour was one of the best things I ever did in NYC. It's too bad that they have now eliminated it. My wife and I tried for years to get tickets to the tour on one of our trips to the city, and when we finally were successful, it was a big day! I'd love to go back...

Where do you get lifting straps? I use chains on the machines and they are great as you can lock on any place and adjust lengths and more. Only negative is the weight of a number of 3/8" chains.

Excellent you tube, very interesting how they jigged up for different operations.

I used boat winches with seatbelt style webbing. Even with two 2 inch straps and a ton of pull on each, clamps and cauls were still required to flatten the layers.

https://sawmillcreek.org/attachment....6&d=1711847387

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Originally Posted by Maurice Mcmurry

I used boat winches with seatbelt style webbing. Even with two 2 inch straps and a ton of pull on each, clamps and cauls were still required to flatten the layers.

https://sawmillcreek.org/attachment....6&d=1711847387

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I'm coming to that realization. This bending stuff - not easy to do.

My next test will be with two 3" straps and clamps. Then I'll make some cauls for the straight parts. If that doesn't work.....

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Originally Posted by Warren Lake

Where do you get lifting straps? I use chains on the machines and they are great as you can lock on any place and adjust lengths and more. Only negative is the weight of a number of 3/8" chains.

Excellent you tube, very interesting how they jigged up for different operations.

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You can get lifting slings here. https://www.mcmaster.com/products/slings/slings~/

OK. Some steps forward, some steps back.

1.) Clearly the cauls on the straight part of the jig work very well. Clearly make the gaps disappear or get very small.

2.) I opened up the Amazon package and took out the 3" wide ratchet straps. OMG are they heavy and the metal ratchet is way too wide. No way I can use two of these at the same time (could use two straps, but don't know a way to keep the ratchets from getting in each other's way. Kinda looks way too heavy duty for the task, but that may just be by virtue of them being 3" wide straps.
Attachment 519041
Now the strap did do a very good job tightening the laminates against the jig, at least on the curved part. The straight part clearly needs cauls added to the outside and clamped. That's easy.

But trying to use the winch (which is great for pulling the laminates around the jig), at least how I have it attached with eye bolts gets in the way of the ratchet straps.

So kinda stuck thinking of a game plan going forward.

Go back and look at the caul and padding photo from Michael Fortune I posted. If you make a similar caul, use sufficient flexible padding, and increase the number of clamps, you will be fine. Michael has bent laminated tighter curves than you are attempting.

So going to try gluing some laminations together, then putting them in the jig. Clearly I need the winch, as I don't have the physical strength to pull the parts together by myself. I'm narrowing down some ratchet straps to help. Clearly this will be a test piece, with yet more modifications to come.

A quick question. For glue, my choices are Ultra-CAT Powdered Pre-Cat Resin, or West Systems Epoxy. I clearly need a very rigid joint to avoid any springback. The pieces will live outdoors in Florida, so heat, humidity, moisture etc... will be a part of their life. I was thinking that the high clamping pressure might make epoxy a great choice, but may be mistaken there for this application.

Any suggestions as to which of these will be better to use?

I would use epoxy resin both for the long working time and the bond. West Systems, Total Boat, etc.

I agree with Jim. However when you say "I was thinking that the high clamping pressure might make epoxy a great choice, but may be mistaken there for this application.", remember that epoxy doesn't need a lot of clamp pressure to work. In fact, too much and it is not a good idea. Epoxy has gap filling properties which may help you here on minor variances.

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Originally Posted by Michael Burnside

I agree with Jim. However when you say "I was thinking that the high clamping pressure might make epoxy a great choice, but may be mistaken there for this application.", remember that epoxy doesn't need a lot of clamp pressure to work. In fact, too much and it is not a good idea. Epoxy has gap filling properties which may help you here on minor variances.

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Whoops. I typed that backwards. What I meant to say was that I was worried that high clamping pressure would make epoxy a POOR choice. I corrected it above.

For a really rigid glue line, I'd use Unbound 800. It is ok in exterior applications as long as it isn't continually exposed to water.