what are some of you folks,out there,using to make concaves? I know that stan pleskunas had some concave rasps a while ago…I’ve even heard of guys using varying sized (halved and formed) pieces of pvc with sand papers adhered to 'em. What are some of your methods? (thanks - in advance!!).
what are some of you folks,out there,using to make concaves? What are some of your methods? I use a small surform (5"). I lightly use a pencil to outline the shape/perimeter, then tape off that line to make sure the concave doesn’t spread beyond the line. I decide how deep I want it, then start carving, measuring frequently. I stop short of my final depth and blend/finish with 40-grit (no block, just the folded/glued paper). Hope this helps…deeb…
I use a small surform (5"). I lightly use a pencil to outline the > shape/perimeter, then tape off that line to make sure the concave doesn’t > spread beyond the line. I decide how deep I want it, then start carving, > measuring frequently. I stop short of my final depth and blend/finish with > 40-grit (no block, just the folded/glued paper). Hope this > helps…deeb… I outline the concave with a template I made; then take a few shallow passes with my planer going from zero at the beginning of the concave moving the blade down to the depth of the concave in the middle then tapering off back to zero depth towards the back end of the concave till I almost reach the desired depth (about 3/16" for my liking), I then shape the sides of the concave using a small radiused sureform I found at the hardware store using the deepest part of the cut from my planer as the starting point working my way out towards the rail, using curved strokes nose to tail, I follow this with a radiused shaped piece of foam 2" wide x 6" long that has a piece of 100 grit sandpaper glued to it to smooth out the sureform marks, a convex blade spokeshave is used to get the stringer flush with the foam.
I use a small surform (5"). I lightly use a pencil to outline the > shape/perimeter, then tape off that line to make sure the concave doesn’t > spread beyond the line. I decide how deep I want it, then start carving, > measuring frequently. I stop short of my final depth and blend/finish with > 40-grit (no block, just the folded/glued paper). Hope this > helps…deeb… What shape of concave do you use, running the length od the board is it elliptical with the long axis running the length or the short axis running the length, or is it a perfect circle?
…half round surform…36 grit contact cemented to 4" ABS pipe…Screen over sponge…
It’s an elongated teardrop shape. It runs from the tip of the nose to about the board’s mid point. The narrowest end of the “teardrop” fades out in the middle of the board. So, the long axis of the “semi-elliptical” shape comes to a “point” at the board’s center. The widest point is 12 inches from the tip of the nose, where the concave begins (width-wise) about 1 inch from rail’s edge.
Deeb and Paul… thanks, very much! Exactly what I was looking for! T.
Deeb and Paul… thanks, very much! Exactly what I was looking for! T. Pencil in the desired outline, tape it off just less than an 1/8" outside the line, carve the concave with your planer to as close as to finish as possible. I have a series of concave sanding blocks, some deep, some shallower that I use to finish off the contour with. Pull the tape, dust off the line and your done. http://www.JimtheGenius@aol.com