Laying Up Radius-Curve Door Panels
From contributor B:
A more aesthetically pleasing method is coopering. It will require good planning and some jigs, but no specialized equipment.
Make a full-scale drawing of your curve. Now rip relatively narrow battens (strips) to approximate the curve. They will be like strips for a glued-up solid panel except that they will have beveled rather than square edges. Dimensions and bevel will be determined by your curve. Determine a curve that will fit the inside of your battens when they are joined. Cut a few of these curves out of MDF or particleboard to build a form. It doesn't have to be super strong. Wax it. Now glue up your battens. You can lend out your bar clamps for the day because they will be useless to you. Use band clamps to hold the battens tight to your form and either pinch dogs or notches cut at the ends of the battens for lightweight clamps to bring the ends together. Two beefy hardwood strips screwed in appropriate locations on the form will allow you to use wedges to apply pressure in the middle. When the glue is fully dried, whip out your planes and shaves and get to work fairing the curve. The convex side will be easier than the concave side (if you are a lucky dog, your job will not require fairing the concave side).
When the curve is fair, it's time to cut to length and field the panel. Use a vertical panel raiser so that you can safely raise the ends. This step will require jigging and a slow approach to material removal in order to make the side and top/bottom profiles match up. Be prepared to sand.
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From contributor C:
Donít mess around - get a vacuum bag.
From contributor D:
I was taught and have used the system you described. It was very effective but I have found a faster way. Instead of making the form to clamp the strips up on I use the miter fold technique.
After you have made your beveled cooper strips place them narrow face down on a very flat surface (I use a torsion box on top of saw horses). The sharp edge of the beveled strips should line up next to each other just touching. Next, I align the bottom end of all the staves by screwing down a straight edge to the work surface and butting all the staves against the straight edge (a strip of scrap plywood works well for this). You should be looking at your panel lying face up in front of you, only flat. Now is the time to make sure all the strips are straight and color and grain match is acceptable. Clean the face of the panel thoroughly with lacquer thinner. This will prep the wood for the tape. I use the band packing tape (3/4" wide, the type with the little strings running through it), going across the grain every 2 to 4 inches. Then, with the grain, I lay wide clear packing tape over the joints, the type you use on moving boxes. Now flip the assembly over. It will be a lot like a tambour door. All you need to do is lay the glue in the joints, roll the panel so the joints close, glue squeeze out stays on the in side, and put a few strips of tape across the convex side of the panel to keep it closed. Finally, lay the end grain on a cross section plan view of your door and make sure the assembly glues up exactly as your curved rail so they fit together well.
You must make sure that your staves are perfectly straight. you do not want to put excessive tension on the panel, the tape may give, however, the cleaning of the panel with thinner helps the tape adhere and creates a very strong assembly. If you have a problem getting straight stave send me an e mail, I'll let you know what works for me in that area.
After the glue dries just peel of the tape and hand plane the high points. I like to cut a rabbet on the inside edge of the panel, and leave the inside beveled. It makes a really interesting contrast between the smooth outside of the panel and the faceted inside. If you do this and you are staining the wood, make sure you lay blue tape over the inside face of the panel, or pre-seal that side so glue squeeze out does not become a problem for you.
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