Hi, I want to make a chair seat that will be curved from side to side. One continuous smooth curve. Would it be wise to try to cooper the seat out of 8/4 stock like barrel staves rather then to glue up 10/4 or 12/4 stock and just chop out all the wood that isn’t needed? About 3/4 of an inch would have to be removed from the middle/deepest part of the concave side of the seat. And 3/4 from each side on the convex side of the seat. I have tried to cooper the seat as you can see in the photos. For now this is just a dry clamp. But some of the joints are not completely tight. I can slip a piece of paper into a joint about a half inch as can be seen in the first photo. Each of the middle boards and the inside of the outer boards all have two degree cuts on the edges. So when matched with the next board the joint is four degrees. Putting the c clamp on (see second photo) with very little clamping pressure really tightens up all of the joints. Would this work? Or would the joints break apart after many years? The only reason I thought to cooper the seat rather then to chop the seat out of a thicker glued up piece is to save some wood, time, and money. But now I think the chair seat will be better made if I chop it out of one large glued up piece. Any thoughts are deeply appreciated. Thanks. Pete
Replies
I don't think it really matters. It sounds more like a design issue than a technical issue. As far as the open joint though, just run a jointer plane over the edges and it should be nice and tight.
Hi Ben, Thanks for your thoughts. I did run all of the edges thru my jointer before I dry clamped them. So they do have nice smooth surfaces. Pete
Pete:
Most seats that I have seen are sculped from a thick parallel glueup. I would seem that the flat underside would make the fitting of the legs much easier.
Just a thought,since chairmaking is not my greatest skill.
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Pete, if you are doing just one or two, it wouldn't make much difference if you used 12/4 and chopped out the waste. But, if you are in any kind of production, coopering the seat from 8/4 staves would be way less expensive. 10/4 and 12/4 tend to run a fair amount more per bd ft than does 8/4, plus there is less wood to "waste". As far as clamping, it would help to close up the gap if you had the Bessey or bar clamps top and bottom. This would achieve the same thing as the C clamp, but would be spread out across the entire length. Once the gaps have been spotted, you can loosen the clamps on the opposite side of the gap and tighten the ones on the same side as the gap.When I'm doing a coopered glue up I use biscuits to help align everything. I set them 1/2" from the bottom so as to stay out of the scoop. I like to leave 7/8" at the thinnest point, which I try to locate 5" or 6" forward of the tailbone. Another trick on coopering a seat, the two outside boards can be beveled so that they return to level. In the attachment, the red lines are the bevel cuts. You may not need the outside boards level, but I have found it helps in joining the seat to the legs.
Bill Lindau
Thanks Pat and Bill for your suggestions. At this time I am just trying to get one chair made. However, I think I would like to do more in the future if I could figure out how to make them and then sell them. Selling is something to work on in the future. Although I forgot to mention it in the first post, I also want to taper the seat toward the back. Bill, the drawing that you posted is similiar to the Maloof style seat right? I have his video and it seems the same. The seat I am after is like the one in this photo of a chair by Michael Fortune. This seat looks to be quite thin. Maybe one inch. I think I would go a bit thicker. Maybe 1 and 1/2 inches thick. I think it would go better with the rest of my chair design. I also don't think the radius of the curve would be as small as this one. I am thinking of a gentle curve. Thats why I am debating which way to do it. Anymore thoughts or ideas are appreciated. Thanks for all of your help. Pete
Pete, you are correct, the bevel configuration I posted in the attachment is straight out of the Maloof video. Are you wanting to make the seat 1 1/2" for strength as well as proportions? The brace between the front legs (Fortune pic) that carries the seat would allow you to go as thin as you wanted. But now more than ever I would cooper with 8/4. Gluing up a thick block of 10/4 or 12/4 would leave you with a 1/2 day of getting down to the shape and thickness you want. Once you get the clamping format down, you could dress the 8/4 down to 5/4 before the glue up. If you are shooting for a tapered seat, you could either cut the taper from a square blank or you would need to use a taper jig as you were cutting the bevels. Using the taper jig would keep the grain from running out at the sides and would look the best.
Bill
Hi Bill, Thanks for the quick reply. I do want to go with the thicker seat for strength as well as for looks. The chair seat will not have a support under it as the Fortune chair shows. I also plan on going with the Maloof style joints to attach the legs to the chair seat. I would like to taper each "stave" of the seat, I think it would look better also. I figure that each of the three middle staves would all be the exact same measurements and bevel cuts. 3 and 3/4 in. across the back, centered on a center line, 4 and 1/4 across the front, centered on a center line, and 22 inches deep. With a 2 degree bevel cut on each side. The two end staves would have the same over all measurements and the 2 degree bevel cut on the inside. But they would have to have a bevel cut on the outside that would make them parallel to each other and perpendicual to a straight edge that is laid across the top of the seat. I hope I am explaining this correctly. I think I need to do this for making the leg/seat joints easier. The overall measurement of the seat would be 18 and 3/4 by 21 and 1/4 by 22. As for now, I have been using poplar, in order to save money while I figure this out. I haven't yet tried to dry clamp the seat using your suggestion of one clamp on top and two under. Or the loosening and re tightening of the clamps until all the joints are tight. You see this was my big concern. Am I good enough to get all the joints really tight with all of this tapering and bevel cutting. Or should I just glue up a big thick block of wood that has all 90 degree edges and start chopping wood until I get the curve I want. I will continue with your advice to cooper the seat in order to save time and money. It will be interesting to see if I can figure out how to dress down each individual stave before the glue up. That should save time also. Well thanks again Bill for your knowledgeable advice. Pete
Pete, I follow the outside edges being parallel ( I think that would take a 8deg bevel) and these same edges being square to the straight edge laid across the top. But since the top of your outside board isn't square to the edge, how will you notch and rabbet this piece so that it will join the leg? I guess you could shim the base of the router so that it was square with the edge.
Bill
Hi Bill, I planned on notching and rabbeting the two outside boards the same way that is shown in the video. I will keep them flat (unshaped) until after I cut the joints. In the video it shows that Sam Maloof glues up the three inside boards first. He then cuts the joints in the outer boards. I guess he shapes the outer boards before he glues them to the inner boards. I will have to watch the video again, but I think this is how he did it. Another thing I have noticed is that on the top of Maloof's seat there is a flat border of maybe an inch that goes around the outside of the seat. The seat isn't sculpted right up to the edge. Maybe I'll have to do something like this. But I don't know now. Anyway thats the plan. Do you think it will work for me? Pete
Pete, there is something I don't understand. Referring to the Maloof video, the front legs join the seat at right angles.Even if you do the notch and rabbet the side boards of the seat before the glue up, because the sides depart from level by 8 deg (2+2=4, 4+4=8), your legs will be canted out by 8deg. This is why Sam configured the bevels (ie my first attachment) so that the side "staves" or boards returned to level. I will try to illustrate what I'm trying to explain.
Bill
Hi Bill, You may have pointed out a problem with my plan. Let me say now that you are more knowledgable then I about chair making. Maybe I didn't explain my thinking as well as I should have in the previous posts. This is what I "thought" would work. For the two end boards. I would first cut them into the tapered shape that they need to be with a 2 degree bevel on the inside edge and the 8 degree bevel on the outside edge. The top and bottom of each of these boards would still be unshaped and parallel to each other. I would now cut the notches and rabbit them. That was the plan. Now that I have written this I might be able to see the problem that you point out. When laid on a flat surface, the top plane of the board is farther out then the lower plane of the board. What will happen to the attitude of the legs as a result of the way I rout the upper and lower rabbets? No matter what angle the legs take on, will the joint be tight on the top and bottom? Will I have to shave some of the inside tenon to be an angle? If the leg joint is a tight fit on both sides of the board and it does make the legs cant out,what bevel angle would the edge of the boards need to be to have the legs cant out at 5 degrees? The 5 degrees comes from the video. Sam Maloof has his back rocker posts cant out at 5 degrees. This is all I can think of now Bill, your thoughts have me thinking and confused. I guess it is try things and see what happens. Thanks for your expertise and your time. Pete
Pete, in the Maloof rocker, the rear leg cants out at 5 deg. But the notch in the seat is in the back corner and it only has two faces (a simple inside corner). One of these faces is beveled at 5 deg and when the rabbets are routed in that face they are done with the special 5 deg rabbeting bits, one for the top and one for the bottom. The other face of that notch is square to the top surface and is rabbeted with a standard 1/4" rabbeting bit. The front legs are joined by rabbeted notches as well but these notches are set back an inch or so from the front of the seat so that they have three sides. It would be difficult to have the middle face beveled at 8 deg and the other two square to the top. These things are hard to talk about without some visual aids. What I did when I was first getting in to this style of woodworking was to make samples or test joints out of scraps. Let me know how things go. If you want to contact me directly, my e-mail is [email protected]
Bill
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