Replies

1. 
   Floss | Jul 21, 2007 05:49am | #1

   Have you ever used a vacuum bag?

   http://www.vacupress.com/vacuumveneering.htm#curvedwork

   If you build a form to match the existing radius then you can laminate bending ply and veneer to get what you need.

   Too bad you didn't build the whole project from the start.

   May be tough to match the existing radius.

   How much room do you have to fudge a piece in?

   J.P.

2. 
   hammer1 | Jul 21, 2007 06:18am | #2

   You didn't say if the job was painted or natural, or how tight the bend will be. Painted would be much easier. You can use bendable plywood for the arch. There are many different brands and types, some call it 'whacky wood'. There are also flexible moldings but I haven't seen them in natural wood. A cleaver finisher can make it look like real wood using stains and a graining tool. It might be wise to use a corner block so the bent crown doesn't have to match straight crown in the corners. If it's not too tight a bend, you may be able to make ordinary crown conform. These are the most sensible ways in terms of labor and cost. Once you start having to laminate up your own stock, make a form, do the glue up, sand it out, you are talking a lot of work and it doesn't always come out well the first time.

   http://www.marineply.com/stagflex.htm
   http://www.trimster.com/flexcat.asp?category=Crown&option=popular

   Beat it to fit / Paint it to match

1. 
   stainslinger | Jul 21, 2007 08:38pm | #6

   It's a 56" radius. The material is Walnut. Building the flat underside of the arch is going to be fairly easy once we get the form built. It's the inside and outside crown that has us a little stumped. Right now we're thinking to create a blank that follows the shape and then having my carver shape it by hand. We're just not sure how to get the wood to bend in two plains.

1. 
   hammer1 | Jul 21, 2007 10:58pm | #8

   First thing, go find the designer and kick his/her *&%*. You will have to take a two pronged approach with the crown. The key stone will be a big help. The first part is making the arch. I think I would make it in segments and think about it as solid all the way through, not hollow in the back like an ordinary crown. You can saw out the segments for a flat arch. You may only need 1/4" or less thickness. This will serve as the base to work from. After that, it would be a matter of building up with small pieces that are flexible enough to make the bend. I think you would be able to bend 3/8" x 3/8" in two planes without steam. Steaming would require clamping in a form and allowing to dry. The small bending pieces will have to be held temporarily with ? nails, pins, screws and blocks, until the glue dried. You wouldn't want any hardware where you will have to shape things. Some of the pieces could be shaped ahead of time to come close to the profile you want. The traditional S curve of crown moldings is difficult enough with straight pieces, let alone a compound curve. Hand shaping will probably be required. A variety of scratch stock scrapers would come in handy as would a reverse profile template. At least walnut works easily. It's not too different than what is required for scroll type bonet pediments. I have a couple of old pictures of a flat arch in segments and one of a build up for a crown like shape. Not exactly what you will face but I think you will get the idea. I don't know how the radius of the arch will be effected as it bends in both the concave and convex directions. Someone with Auto cad may be able to plot it out for you. It's certainly a complicated shape and it may not be very uniform as framed and sheetrocked. I think I would try to build it in place rather than make a duplicate form. Hope this helps with your head scratching.
   Beat it to fit / Paint it to match

   
3. 
   sapwood | Jul 21, 2007 07:50pm | #3

   I've tried to imagine the form you are trying to build, but cannot. Your description is confusing me. Can you attach a drawing? Perhaps you can make a rough model from a cardboard tube and photograph that.

1. 
   stainslinger | Jul 21, 2007 08:26pm | #4

   I will photo the space on Mon. and attach that afternoon

2. 
   stainslinger | Jul 22, 2007 12:01am | #9

   Hi everyone,I found these pics, sorry I don't have a full front elevation. This might help clear up some confusion.Thank you for all the input. I'm going to doc this project very closely, I'll post pics to show the progress.stainslinger

   
1. 
   KeithNewton | Jul 22, 2007 05:59am | #10

   I am still having trouble visualizing what you are wanting to do also. Are you talking about two semi-domed ends on the ends of a semi-cylinder, with a molding trim that travels down the straight sides, then around the curved ends? Have you given any thought to turning these end parts on a large lathe, something like a large bowl with a moulded edge, which is cut in half. Then joining those parts to the semi-cylinder, and matching the molding? Of course, the molding could come first, then matching it while turning would be possible also going back that way. Do you follow this line of thought. I have a lathe which I built that can handle work up to seven feed in diameter, so don't discount this option by thinking only in terms of what most small shops have to work with.

1. 
   stainslinger | Jul 26, 2007 03:38am | #11

   Hi Keith,We went to the job site and made a cardboard template of the arch.Then refined the radius with trammel points we cut out masonite and duplicated the arch in the shop.Attached are the pics of the form. I'll post pics to show the progress. To date this is one of the most difficult projects my shop has ever built. It's very exciting to see it come into shape.Paul

   
1. 
   KeithNewton | Jul 26, 2007 05:03am | #14

   So, Now I see what you are talking about. I am sure this is upside-down. Are you still needing to make a crown for both sides of this arch as it meets the ceiling, or are you needing to make a trim that follows the arch cut into the cylinder?If yes to both, do you have the size and profile for each?

2. 
   stainslinger | Jul 26, 2007 05:46am | #15

   The crown has to follow the arch cut into the cylinder both inside and out. We are going to bend and glue 3/8" x 3/8" walnut strips along the radius one at a time and slowly build up a rough profile. Then carve the profile by hand. I have a carver on my staff that's been at it for 25 yrs.Check out my work at quailhillinteriors.comTomarrow we are laminating up the curved underside of the arch. I'll keep you updated with pics.Paul

3. 
   KeithNewton | Jul 26, 2007 06:55am | #16

   It sounds as if you have already chosen your path to the end. I thought you were asking for advice. While I am happy to hear there is a carver out there earning a living at it for 25 years, I don't think that is a very efficient way to do what you have described, and I shure would not laminate 3/8" one layer at a time to get a blank for carving. Good luck though. K

4. 
   stainslinger | Jul 26, 2007 03:49pm | #17

   Hi Keith,I am sorry if I sounded like all decisions were made. To date we can't come up with a better way to form the crown. I don't want to form it with segments. I want it to appear as if it has been bent from a single piece of wood.I am still looking for advice. Please, if you have any suggestions for a more efficient way, I would love to here it.regards,Paul

5. 
   colebearanimals | Jul 26, 2007 06:54pm | #18

   Paul,

           I've been thinking about your project. Besides keeping your strips in consecutive order to keep color and grain match ( I'm sure you already know this ) you might have to experiment with the size of your walnut strips. I think when you attempt to bend those around they're going to want to twist and, at some point, want to pull away from the form.

           To help this situation, could you glue up both sides at once? That would allow you to pull things together. Looking at the form you might want to put in more blocking, closer together making it as close to solid as possible. With a sloooooow setting glue and 3 or 4 sets of hands you should have it.      Just an idea.

                                                        Paul

6. 
   acornw | Jul 27, 2007 11:15pm | #19

   We do compound curves all the time. We seem to be the only ones around that can even visualize it, much less build it. We just did a 10 segment domed ceiling with pie shaped arched crown assemblies that had compounded molds at the perimeter, joined to single arched molds as the "rays" of the ceiling. Your form looks good, but difficult to clamp to. We build a radius "stud" type wall for the vertical curve - or cylinder. Looks like 56" radius in your example. Then we point out the vertical points from site measurements onto the stud wall. Connect the dots and you have the 3d curve. Then surface out a bunch of Walnut to whatever thickness you want for the tighter of the two radii, and bend into that curve with rigid glue. Then bandsaw the longer radius into the face of the multi-ply assembly, and then curve the back. You can roughly pre saw the second curve once you establish that with hardboard or equal, saving on material quite a bit. Duplicate the short radius on your shaper vertical fence, and the long radius on the shaper table (if that will work with your knife grind and rotation), power feed on thru and enjoy the scent of lotsa Walnut in the air. There will be lots of waste and lots of resawing, but it is the best look for the finish you can get short of hewing out of a large tree. Dave S
   http://www.acornwoodworks.com

4. 
   colebearanimals | Jul 21, 2007 08:30pm | #5

   Hi stainslinger,

          I can't quite see what you're up against by your description. If it's possible, could you post a picture of the opening or a drawing? Does the molding have a profile detail or is it flat? Getting a glued up blank with a compound curve past a molding head is near impossible. You might be able to break it up into manageable sections for shaping. Don't forget , also, that when the curved molding miters into straight molding the miter will have a slight arch to it to match the profiles.

          Check this out. It is the best book on the subject I've ever seen and will be well worth the time to find a copy. It will take some time to digest it but very informative.

           It's    " Circular Work in Carpentry and Joinery "    by George Collins

                                                  Paul

1. 
   stainslinger | Jul 21, 2007 08:48pm | #7

   Yes, I have it. We're using it to aid in building the form for the soffet portion. The convex and concave crown is the challenge. We have to bend the wood to the shape. Forming it in sections and butt joining together is not acceptable. There will be a key stone at the apex. This will be the only seam.I will post a pic on Mon. That might clear up some of the confusion.

2. 
   stainslinger | Jul 26, 2007 03:43am | #12

   Hi colebearanimals,Here are some pics of the arch we are duplicating in the shop to form the walnut to.Paul

   
1. 
   colebearanimals | Jul 26, 2007 04:16am | #13

   Hi Paul

              That looks really fun. I love those kind of projects where you have to think and scratch your head a little. Looks like a good approach. If in doubt, make a template.

              I've done plenty of curved work but nothing with a twist in it like you're doing. I'm envious.

              Thanks for the pictures and update. I would be very interested in your progress. Keep me updated if you have the time.

                                                           Paul