hey guys, I will be foiling my balsa and cedar (south american cedar, is this redwood?) skeg for my 9’6" soon and was just wondering if a surform is ok to use of will it crush and rip the balsa??? see pic below

I also have a 4" grinder with a disc on it with lots of little bits of sandpaper glued to it (name?!) is this good or too harsh??

thanks for any info and tips guys.

Hi Robbo,

The surform will work, though it will cut the balsa so much better/faster than the cedar that I would be kinda careful about how you use it: work across the grain, cedar-balsa-cedar. Light pressure and a new, sharp blade in it so you don’t tear the grain.

The flap-disc wheel ( that’s what it’s called ) attached to your 4" grinder is going to be hard to control, cut very aggressively and maybe mess up all your nice work so far. I’d avoid that - I have one and use it for things like gouging out areas of heavy oak logs to make rough-and-ready anvil-like things for the sister that does silversmithing. Not fine work.

If I was doing it, and I come equipped with a bunch of woodworking tools, I think I would start with a shallow angle block plane or possibly a spokeshave, go on with a cabinetmaker’s wood rasp and finish probably with a random orbital or orbital sander with fairly fine paper in it. You could, however, do a very good job with no more than the rasp and sandpaper, even sandpaper alone if you’re patient.

As shown, clockwise from top left:

a) random orbital sander - badly in need of a new pad

b) orbital sander, 1/4 sheet type

c) spokeshave

d) shallow angle block plane, the ubiquitous Stanley #60 1/2

e) cabinetmaker’s rasp, one side half-rounded, one side flat.

Not shown but necessary. some sort of clamp to hold the fin to your workbench. While none of these shown is really likely to throw the fin across the room, it’ll help your control a lot to be able to work with both hands.

Give or take the power tools, everything can be found at flea markets and yard sales for short money.

hope that’s of use


I agree with Doc (who doesn’t, anyway?) but I would add: be very careful with rasps or surforms or coarse grit sandpaper when working with different densities materials. CUTTING tools (planer, spokeshave…) will cut at the same level hard and soft woods. Rasps, surforms and sandpaper will go deeper where it’s softer unless you feather it (and then it’s gonna be a rather long job). Better do things fast and OK than slow and mean…

How do you manage to go across the grain with a spokeshave on balsa ? ?


Maybe not a spokeshave, but one of these razor-blades planers such as the blue or red ones will do it. (As you know, of course, spokeshaves tend to “catch” easily with the slightest angle change…)

Hi Balsa,

Looking at your planes, I happened to notice that they are (mostly ) relatively steep angled types, so I wondered if you had ever run across the next step in that direction: the scraper planes, with their blades actually leaning in the direction of the cut. shows some of the ( no longer made) Stanleys, is a kit for a wooden version, an article on making a wooden ( and quite clever) version…

and then there’s this beauty: , though you’d want the services of a metal-caster to make one…

What’s the purpose of them? Well, they use a thin piece of tough steel, the edge filed and then burnished so that close up it looks like a J, and that fine hooked-over edge does a really nice job of scraping off very, very fine surface imperfections. They leave a surface that is good enough for cabinet finish, no sanding required. Nor torn grain, if the scraper is sharp enough.

While I am thinking of it… - if you have lots of time to spare…


I use a cabinet scraper to take off the resin bead / tape line on the rails from hotcoating. Works like an absoulte charm without any of the scratching & gouging that you get from sandpaper or surforms.

On wood, especially hard wood, a well-prepared scraper produces a much smoother finish than even the finest sandpaper. I don’t use a holder for it, with a little practice your hand finds the right angle. You can also turn it to either push or pull, working into corners or other tight spots.

I use a French Curve scraper to get in to smooth fillets like with glass on fins. Much more accurate than a dremel or sandpaper wrapped around a dowel…


I use a cabinet scraper to take off the resin bead / tape line on the rails from hotcoating. Works like an absoulte charm without any of the scratching & gouging that you get from sandpaper or surforms.

So do I. With a piece of broken glass. Works great. The trick is to do it when the resin is “just right”.

You’re right, Balsa…but I cheat. With epoxy, that ‘just right’ semi-soft stage is about 10 hours long!


block plane, spokeshave and scraper thats all you need(need a shaving edge on all tools)

although i like the surform alot

I vote for very sharp 36 grit sandpaper !