Hi There!
I’m looking at making a 7’ quad.
I’m planning to use glass-on fins.
I was thinking of making them from Balsa. I like the look and figure it would be easier to shape than ply.
What do you think? . . . Will they be strong enough? Will 2 layers of 6oz do the job? Or should I stick to ply?
Thanks for your help!
Monty
Balsa varies in weight and density.
If you get a piece of heavy balsa it should work.
Monty,
Density makes a huge difference, in weight but also watersoaking capability.
I had a piece of 3 mm darkbrown heavy balsa immersed in water for 2 days, the inside of the balsa was still dry. The outside did not go fluffy, like you see with low density.
You can always also add carbon and some super stiff epoxy and do partial lay ups like hp fins have nowadays [p.s. i am not old]
Wouter
Denser balsa would work, but don’t think it’s going to be easier to foil. Without the telltale lines of ply it’s
harder to ‘‘read’’ the foil. Softer material may cut easier, but it’s also easier to make a mistake.
Mike Notary made glass-on non-ply wood tri-fins 25+ years ago, and settled on white pine as the best material.
They were widely used in Florida, and they still might be the lightest glass-ons I’ve ever seen (although those
True Ames complites were/are damn light). Notary made the fins slightly undersized, and they were glassed
on with a third piece of rope up the leading edge and over the tip. The razor blade trim after the install went
off had to leave the bead formed by that rope, and also a trailing edge bead. The sander finalized the fin
template on the board. More difficulty at every step, but back then men were men, bla bla bla.
If you do the balsa, a similar technique would work. 2 layers of 6 oz would be good on a keel, just don’t sand
much of it off!
BTW, hi to BalsaBill, he of the wooden boards and iron men. Anybody on the East Coast that’s interested in balsa
and/or history should stop by his shop in Satellite Beach.
side fins with light wieght balsa lam at least 5 layers of glass to the inside of the balsa before cutting and foiling, its easier to layup the glass first lije a normal fin pannel then attach the balso once the resin has set. once foiled at glass as normal.
for center fins add atleast 3 layers of glass to each side before cutting and foiling the fin as above and add more layed once the fins are foiled.
There are light but not as light as the pine fins and are more work they are harder to make as there is more that can go wrong but they do look very nice.
be careful when sanding where the glass meets the balsa, be aware that the balsa will sand qicker so aim to work away from it angleing off the glass, not towards the balsa.
Hi Monty,
Check out the Greenlight for ProBox thread:
It’s for making bamboo fins but you can easily adapt the techiniques for balsa.
You can draw lines on the fin to help visualize the foil since the balsa won’t give you the “telltale lines” Mike Daniel mentioned.
I’d seal the balsa with epoxy first before glassing to help protect them from possible discoloration.
~Brian
These are the first fins I have made, and I made 4 at once and used the best two. They are not completely balsa, but are a balsa-fiberglass sandwich. Still fairly light and strong. I think I used 3 layers of 4-oz after sealing the balsa with epoxy first.
-cmg
Thanks Mike,
I would second that on the pine. Any balsa that would be strong enough would be as dense as pine.
Monty,
I have some balsa planks that are 3/8" roughsawn and 6" wide. These are from the crates that I get my balsa shipped in. You could plane it and laminate some together to get the thickness.
We’ve used it for stringers before.
email me at and I’ll send you a few pieces to experiment with.
Thanks everyone for an outstanding response. Heaps of great info here . . . Much appreciated!
As this is only my second board (the first had FCSs) I think I’d be better keep things simple so I might go down the ply road. The white pine sounds nice but not sure if I can get it here in Aus.
By the way, nice work cmg.
Bill, thanks so much for your generosity and the offer of the balsa planks but I think I’ll leave it for the time being.
Sways is so special!
Monty