curved joinery

[brocpuffs]

Hi ppl,

I'm getting into curves, not soft & warm (in this group!) but hard, grainy and flammable.

I'm making a heavy chair I call a "sumo chair" because the overall dimensions are somewhat larger than the usual chair.

I'm adding curved edges as I go along. A little bit of oriental feeling

There has to (?) be some way to methodically figure out angles for, say, a mortise thru a piece curved on both sides, different curves. Basically, intersections of curved pieces.

Is this always such a PITA involving a lot of fudging and estimating and jury-rigging?

There's always computer drafting, I do know that, but hell I don't WANNA use computers except to see prototype ideas.

James [e-mail]

[bridger]

chairs are kinda their own thing. people who make lots of custom chairs generally have an adjustable prototype chair that they use to fit the chair to the customer- then from that they can pull angles and dimensions. a lot of knowing what to do comes from experience.

this is an interesting idea for a piece of software- 3d chair design. it would need size data for the customer- those routines might be able to be borrowed from some custom tailoring or haberdashery software. it would need 3d modelling capability- plenty of that around. it would need to be able to export patterns and cut lists.

I bet there would be a market for it.

[brocpuffs]

Makes sense but I do so much like to screw everything around as I go along. Well, it accounts for my (LOW) production rate :-)

All you'd need is a few zillion bucks!!

Since I posted this, I blew the angle on one part of a curved vertical side rail. I wanted the two straight and horizontal side rails (below the seat) to go thru the curved piece. This curved piece is to be the front support for an arm for the chair. The front legs are not long enough to be the front supports, never mind why.

I can patch it with the usual wedges but I am sooo disappointed at not being perfect!

James [e-mail]

[Tom Watson]

Describe the radius of the outer point of the curved section on paper large enough to draw on at full scale.

Draw a line from the origin of the radius to the outside intersection of the two curved pieces.

This will give you the line at which the joining cut should be made.

From this point on it is the same as any other mortise and tenon, with the described line acting as the base from which to begin regular right angle joinery.

Regards, Tom.

"People funny. Life a funny thing." Sonny Liston

Thomas J.Watson - Cabinetmaker (ret.) tjwatson1ATcomcastDOTnet (real email)

[mrmortise]

Hi James, You might try to find a book called "Circular Work in Carpentry and Joinery" by George Collins. 1992, Linden Publishing. Possibly out of print but a local libary system might have it. I would say this ranks as one of the best books on the topic I have seen! Good Luck, Michael

[brocpuffs]

Tom, this just isn't clear enough to do me much good. I'm not even sure we're talking about the same thing :-)

Lemmie try and make my specific problem as clear as I can without ASCII mis-art:

On each side of the chair, there are two horizontal side rails front to back, parallel, both below seat height.

I have a piece meant to serve as a curved, vertical rail. Both horizontal rails are to pass thru the curved surfaces, which face front-to-back.The curves are similar in shape and curvature, but angled re each other so that the bottom of the rail is somewhat thicker (front-to-back) than the top.

I made a drawing in a graphics program and will post it to alt.binaries.pictures.woodworking right after this. The filename is curved joinery.bmp.

The dotted lines (and their perpendiculars) are what I need to get right.

thanks!

James [e-mail]

[brocpuffs]

You know what, I could trace the parts out on paper and go from there!

Always complicating things, that's me-

James [e-mail]

[Tom Watson]

Sorry, I did misunderstand you, but you seem to have happened onto the solution.

Good luck.

Regards, Tom.

"People funny. Life a funny thing." Sonny Liston

Thomas J.Watson - Cabinetmaker (ret.) tjwatson1ATcomcastDOTnet (real email)