cutting concave

whats teh most effective way to cut concave? and get double concaves symetrical?

I was told…hand plane and use a surform to taper out to rails. As far as getting doubles symmetrical, not sure about that.

im calling that a sanding block with a layer of sponge stapled to it does a good job for me. use 40grt to scallop in your double- count your strokes, and keep it even each side(obviously) but continuously check with a straitedge from rail to rail for eveness, fade in, fade out etc… then your gauze on that same sponge block to tidy it all up. i make my block stokes mimmic the waterflow path down the board- works real good on bonzer type venturi- concaves… but thats just me!

k cool, I was thinking surform, but sanding block sounds easier

I’ve just shaped a board with single into double concave. I cut it in with the planer (after watching Jim Phillip’s Master Shaper). I was very careful to count my cuts and try and mimic them on each side. Then I finished with a sanding block, once again counting my strokes and using a straight edge between the rails to eyeball the development. It turned out okay.

I use a hand-held circular sander foam pad with 36 grit sandpaper. Pull it along with an angle.

Well I just tried some stuff… came out ok… I used a belt sander, and a sanding block to do most of it, and it came out ok… My double doesen’t look the best though… but I hope I can tell, its a really small board, I couldn’t find anything else to test it with. Dimensions are 3’ by 18" by 2", I made it out of an old chunk of styroam I found lying around, so I don’t know if that would be any diffrent… and I didn’t feel like using a good surf blank to test stuff out on, I don’t have all that much money.

a styrofoam booger with concave ?

Man , I’d glass that with normal resin, that would be the way to do boogers, I reckon…

“nothing against ‘bodyboards but’ chip”

it was an expeirement… didn’t want to waste good clark foam… ive screwed up a few times allready…

I have used differing diameters of tin cans with 40grit glued to them.

pop cans, coffee cans, milk bottles etc…

you can develop different concaves for diferent boards.

as always count yer strokes and check with a straight edge often.


I usually let a 9 in diameter pipe fall on each side of the stringer for the double barrel. For the front concave I grab the blank and hit it against a 3 ft diameter drain pipe.

…somedays I dont take all my medications

as long as you count how many falls and how many hits on each side and check them often[laugh]

meds are cheepr in canada[laugh]