Outdoor bench with bent lamination curved legs

[Alan Lightstone]

A vacuum bag, even at sea level, will not pull enough pressure for that bend. You will need a bunch of clamps to make it happen.

Mike

How about a vacuum bag with a few external clamps around the bend? I've seen that approach online. Never tried it.

[Christopher Charles]

Should be a fun project. Have you considered white oak-good outside wood and should grey nicely if left unfinished?

[John Kananis]

I'm not sure it would work out as well as it does while I'm sitting on the couch thinking about it but (that radius is just so, so tight) I would cut 1/8 inch boards, steam them and then clamp to forms with a polyurethane glue to take advantage of the moisture). Just let them sit there, clamped up, for a day or two.

[Mike King]

How about a vacuum bag with a few external clamps around the bend? I've seen that approach online. Never tried it.

A couple of years ago, a fellow workshop participant used bending with a form and clamps outside the bag in a workshop with Adrian Ferrazutti. Still, you won't be saving anything because you need a lot of clamping pressure to bend the laminates AND close the gaps between them. I don't think that a vacuum bag gets you anything for your application.

First thing to do is make a form that approximates the radius of the bends you are considering. Then, resaw some laminates of whatever species you are thinking of using and see what thickness of laminate you need in order to get them to conform with the form. That will tell you if the species, form, and equipment you have are compatible with your objective.

I still think you might be better off with steam bending. Have you tried double bending? You heat the wood, bend it one way, then bend it the other. This breaks the lignon bonds in the wood. You can put the piece back in the steam box to reheat, then bend the wood more easily.

I've not done this myself, but Michael Fortune has a lot of experience making tight bends like you desire with that method. You will most likely need air dried stock though. And best if it isn't too dry.

Mike

[Mike King]

I'm not sure it would work out as well as it does while I'm sitting on the couch thinking about it but (that radius is just so, so tight) I would cut 1/8 inch boards, steam them and then clamp to forms with a polyurethane glue to take advantage of the moisture). Just let them sit there, clamped up, for a day or two.

First of all, I seriously doubt that 1/8th inch laminates will make those bends. Second, steaming requires significant time to dry -- a day or two wouldn't likely be successful in achieving the shape -- you'd be completely relying on the glue to hold the pieces in shape. Polyurethane glue is a mess to deal with as well and I doubt that even though it is foaming up that the glue would be of sufficient strength to hold the laminates in the proper shape.

Mike

[John Kananis]

Fair statement on clamping time and the glue is messy but I do "think" it would work - just brainstorming though.

[Alan Kalker]

White oak cut into very thin laminations.
Agree that a rigid urea formaldehyde glue will be needed. Wear a good mask.
Also agree you’ll need to do this on a form with clamps.
Stain it.
‘Finish with Epifanes finish (found in marine stores). It’s a pain to use but it’s the only exterior finish I’ve ever seen hold up through tough seasons.

[Alan Lightstone]

I'm working on forms today. Don't have the right wood, though.

I've also thought of making the corners out of solid wood, and dominos or tenons to connect them to the legs. I've also thought of doing the legs in several pieces like that, then laminating one strip of thin laminate on each side to hide the joints. Very thin laminate, I would think, would be very easy to glue to that. Not sure about longevity, though.

Not against white oak. Once grey, SWMBO would probably like that a lot.

I have experience with Epifanes and System 3 Marine varnish. Epifanes was a real pain to apply. The System 3 much easier. But I'll have to see. It's not the initial finishing I'm concerned about. Refinishing could be hell.

I need to get a better resaw blade. My present one is strangely 1" with 2TPI. Thinking a 3TPI blade would make smoother cuts, though at $400 plus shipping for a Lenox Tri-Master Carbide 1" 3TPI blade, I'm thinking I'll make do with my present blade.

[Mike King]

1" 2TPI should be fine. Actually getting a 3TPI blade could result in worse cuts as the gullet space becomes packed and causes friction...

An option is to ebonize whatever wood you pick for the legs...

Mike

[Alan Lightstone]

So, did some trials. 1/8" white oak and cypress both can't remotely bend around that 1" radius curve (both kiln dried, my local supplier laughed at the concept of getting air dried).

The thinnest I was able to make was 1/32". Both the 1/32" white oak and cypress both can make that 1" radius curve, with some difficulty.

Really not worth the effort for me to make 1/32" veneer in the shop. I'll likely buy some, and try laminating that. But using solid wood pieces and joining them together, perhaps with a veneer piece on the outside layer to hide the joint is sounding more and more appealing by the minute.

I wonder how they made that bench in the photo?

[Alan Lightstone]

So now that I've decided to go with solid wood pieces for the curved portion of the legs of the bench, I've got a problem that I'm having trouble getting my head around.

This is what I am looking to make for the curved portions of the legs. They'll be attached (probably via loose tenons) to straight 1" thick, 3" wide white oak boards.
Curved leg piece for bench 1.jpg
Curved leg piece for bench 2.jpg

Those are from a test piece I just made. The inside curve was made with a 2" Forstner bit, and the outside curve initially on a bandsaw, and refined on a disc sander. My 1/8" bandsaw blade clearly has too many TPI and burns every cut of these, but if refined with a router and/or sanded, that shouldn't be an issue.

I can't imagine I could make 6 of these per bench and have them be identical using this method. The outside curves will certainly be inconsistent, and the flat sections I had to cut on the bandsaw as my table saw can't accommodate 3" thick boards clearly won't be perfectly perpendicular. I don't have a CNC machine.

I'm thinking somehow to use my router table and a template, though I don't have bits pattern bits with 3" cutting length (I do have some 2'1/2" ones). But how do I make repeatable pieces that are this small with these small radius curves? Whoever made that original bench did a tough job beautifully:
Outdoor bench idea with curved legs.jpeg

Totally open to good suggestions.

[Mike King]

Option 1 -- it's handmade, and the curved pieces are separated by a lot of real estate, meaning that the slight variations you get won't likely be noticeable...

Option 2 -- scribe it and work to the scribe line with a rasp and sandpaper.

Option 3 -- you've always wanted a shaper, right? Pattern shape the piece with a spiral helix cutter.

Mike

[Alan Lightstone]

Option 1 -- it's handmade, and the curved pieces are separated by a lot of real estate, meaning that the slight variations you get won't likely be noticeable...

Probably true, but I'm concerned about the ends of the corners not being at exactly 90 degrees, so the piece would rock.

Option 2 -- scribe it and work to the scribe line with a rasp and sandpaper.

Basically did that with the sample piece, although with a disc sander and an oscillating spindle sander.

Option 3 -- you've always wanted a shaper, right? Pattern shape the piece with a spiral helix cutter.

Yes, but frankly, for whatever reason, they kind of scare me. Plus, no room unless I replace my automated router table with it.


I'm trying a M-Power Router Jig with the small circle attachment next. Kinda bulky, especially with my large Festool router, but started to make a template last night and I'll see how that goes. The interior angle I can repeatedly make with a Forstner bit, so it's really the outside angle (which I agree, I bet no one would notice) and most importantly how to get the ends to be perfectly perpendicular to each other that I'm fighting with now. Trying to figure out how to cut out these pieces on a tablesaw with a sled instead of the bandsaw.

[Kevin Jenness]

Glue up the leg assemblies with the inside radius cut in otherwise square blocks. Do the outside curves afterward with a template and flush cutter.

[Jim Becker]

Glue up the leg assemblies with the inside radius cut in otherwise square blocks. Do the outside curves afterward with a template and flush cutter.

I agree with this technique.

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My concern here would be weak grain structure on a piece cut from a solid block unless the inside radius is kept to a minimum so there is a lot of "meat" to the component. A bent lamination is a lot more complicated, but it doesn't have that potential problem in addition to joinery that can fail. Doing the joinery version requires stout components to withstand normal seating stresses as well as the effects of weather.