Bench seat

[jack dempsey]

Hello,
I am looking for some advice/guidance. I am planning a bench and want to have a slight concavity to the seat. The seat will be 53" in length and 14" wide. My plan is to give the center 12" a slightly concave surface. I have never done this and I am looking for advice on methods to accomplish this. The bench will be made from red oak. I have contemplated looking for a Stanley Compass plane to do this. Any advice or comments is appreciated.
Thanks,
Jack

[Jim Koepke]

My clarity on this is a bit foggy. Do you want a slightly concave surface to the center for the full length?

If that is the case a Stanley compass plane may not be the best tool. For a little clearing of the confusion, what is often called a compass plane from Stanley is something like their Circular plane in a few variations:

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For a concave curvature for the full length you might want something like a round plane, half of a hollow & round pair:

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The plane on the left was found in a second hand store and the hollow on the right was used to shape the sole to make a matched pair.

For a bench seat it would be like a large scale molding.

jtk

[jack dempsey]

Jim,
Thanks for the reply. Sorry for the confusion, I will need to have a slightly concave surface for the full length of the bench. I may consider looking for a round plane. My thought was to use a circular (what I thought was a compass) plane across the grain then smooth with a scraper and sandpaper.
Thanks,
Jack

[Jim Koepke]

There are some wood body "compass" planes that have curvature from toe to heel and side to side. These were, and still are, used for shaping chair seats and other free hand concave work.

Are you by any chance in the Portland, Oregon area?

There is also what is often called a gutter plane:

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Sorry for the fuzziness of the image. This seems to be my only image of this plane.

If you found an old wood body plane it might be possible to convert it for the job.

jtk

[Prashun Patel]

A compass plane will be slow going. There are a number of faster ways to do this:

(if you're not above it) an angle grinder with a carbide cutting wheel. Then a bench of block plane or spokeshave to smooth.

An adze
A scorp
A pullshave (see Veritas)

I see a ton of chairmakers using the above. I know very few (read, none) using a compass plane. Jim's gutter plane looks like the bees knees in this case. The pullshave is akin to that.

[Ben Ellenberger]

If you are looking for another project before your real project, you could try making a plane. Ron Hock sells curved blades. I got one and made a small round plane that I later converted into a compass plane.

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[jack dempsey]

Jim, Thanks for the additional information. Unfortunately, I am not in the Portland area. I am about 30 miles west of Philadelphia, almost as far from Portland as I could be and still be in the continental U.S. I have never heard of a gutter plane but it seems as though it may be fitting for this job. Jack

Prashun, Thanks for the information. I will do some research into the tools you mention. Jack

Ben, Interesting idea. It may not work for me on this project but food for thought in the future. Jack

[Tom M King]

Maybe you can find a board with some cup to start with. There should be more than a few sawyers around where you live who have a stock of boards.

[Ken Parris]

I have built several Windors chair seats. And one thing that hasn't been mentioned is that the low point of the seat is not at the center. but is more like three quarters of the distance from the front. If you intention is to have this contour the full length of the seat then any of the planes mentioned should work very well. The power tools mention in my experience are more difficult to control.

Ken

[jack dempsey]

Tom, I am hoping to facilitate this with some basic woodworking. It will not be a large concave area, that being said if I come across the right board who knows?

Ken, Thanks for the reply. I expect to have the concave area just as you mentioned with the low point towards the rear of the seat.
have you done this and if so, what tool would you recommend. Jack

[Prashun Patel]

In fact, since the concavity will run the length of the bench, have you considered just coopering your slats? I did this a couple years ago (on a bench that was never completed!).

I ripped my 8/4 flatsawn board into 2" sections, rotated for qs orientation, beveled the sides near the concavity 1-3 degrees and reglued. Stable, and if you keep the boards in order, the grain pattern can be pleasing.

[Jack Frederick]

I did a couple of these benches out of sapele. It would have been a prodigious amount of work with planes as I think I went about 3/8” deep. I carefully laid out the contour and scored the wood with a circ saw or TS. With those cuts I used a scrub plane, Jack and a couple small block planes as seemed to suit the occasion. With the saw cuts I could tilt the plane and work into profile. I ended up smoothing the profile with abrasives. My hands can’t take extensive shave work and that amount with a scraper was beyond me as well. They came out ok.

[jack dempsey]

Prashun, This sounds like it may be one way to do this job. Did you have issues with clamping for glue up after you beveled the sides?

[jack dempsey]

Jack, The bench looks gorgeous. I like the table saw method. If I understand this, you lay out the curvature then repeatedly adjust the table saw and run it through the saw.

[Jack Frederick]

That is correct, Jack. As I recall I made a few cuts at the deepest level and wide enough to get my narrowest plane, my shoulder plane, between the cuts. Once I was down close I could take the Jack on an angle and get a wider cut to the contour. Taht roughed it in and then abrasives…ugh! I guess you could do a lot of saw cuts, but I did not.

[Prashun Patel]

Not that I recall. You can use cauls to keep them from shifting.

[Mark Rainey]

Jack, the convex sole plane from Philly planes is very useful for planing hollows. Mine has a 9" radius.

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[Thomas McCurnin]

The dished-out section keeps one's hindquarters firmly placed in the bench seat. Another way of accomplishing this is to drop the rear portion of the seat slightly, about 1/2" or about 5 degrees. That was the traditional way of handling this issue for some dining room or living room chairs.

[jack dempsey]

Jack, Thanks for the follow up. I think I will do a test on a short piece of red oak to get an idea of what I am facing.

[jack dempsey]

Tom,
Thank you for the tip. I just took a look at the Philly Plane web site. That may be a consideration for a future use. I imagine it would be a while to purchase one with everything going on in the world at this time.
Regards,
Jack

[Tom Bender]

Be sure to start by making a template to measure with. If you can post a pic of it here we can compare it to our experience. Give us the deepest depth you plan. I'll suggest 1/2" as a minimum.

[Tom Bender]

One or more saw cuts will help you get it right. If you want the experience you can certainly do this with a hand saw.

My scrub plane might be up to the task of hollowing.

[Tom Bender]

template, umm the goblins have turned it upside down

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