FIN experimental work

In order to obtain a better finished work for the leading edge and for the trailing edge I have integrated a Carbon rod in the front and an Aluminium sheet of 4/10 mm at the rear as visible in the pictures below :

The trailing edge can be very sharp like a rasor blade - need some care during handling !!! One may chose instead to give a sharp cut…

Claudio -

I’m not sure about anyone else here - but I want you to know that I really enjoy, appreciate and learn from your posts and technical photos.

While I consider myself to be an above average builder, your insight and abilities to share new ideas are always educational. I wanted you to know that the time you spend posting is so well done and informational. Thanks for being a member of this discussion board.

OK - now with that being said, it’s time for all of us to post a collective “Awwwww!” :sly:


Well said Dick. I agree completely.

Claudio - I’m building a second set of sails using your “gadget” at present.

Touché ! by yours nice words .
The story is not yet finished since I started the laminating operations using this time an Unidirectional Carbon of 160g/m². ( +45°/-45°/90°)
This is a close look for the carbon :

This is the tool I used :

This is what I got after 24 hours being the last layer at 90° (the previous being flatten with epoxy mastic) :

This is my explanation : under the pressure induced by the soft rubber, the woven carbon wires are squeezed down and melting with the resin “except” the white wires (here in Red) that apparently “do not” melt leaving a sort of stripes across the fin surface as visible in the photos.
This sketch try to explain my understandig, unless I got wrong…
I also understood, by a local friend, that some woven “unidirectional” carbon uses melting wires …

Actually, I’m not sure if let the surface as is or …
What is your opinion ?

Do you have trouble shaping the balsa “blank” with the carbon laminations between the balsa peices?Is it differcult to sand both materials together accurately?
Nice fin you have there,thanks for sharing.

No problems Brett so far, I was afraid to at the start, but finally, was OK.
I have to said that the balsa was some what “hardened” having previously impregnated with nitrocelulose warnish. I used also Prestige type balsa that is the harder quality.
Finally, I believe that the resin did some “impregnation” work being the sheets only 1.5 mm thick.
Look to de profile view, no sign of irregularities, probably lucky !!!
I have another idea behind that, but I need a sketch…

As complement to my previous answer, one possibility, may reside in the fact that the hard carbon layer, “once reached” , may acts as a rocking point as depicted in the drawing.

It is my beliewe that in this manner, the sanding plate, if carefully controlled “tangentially” , is rotating around this hard point, and the remaning material, before and after, do not suffer anymore as was the case with my fin.

for my fins (am makin 2 assymetric canards) for my canting keel boat, i am using 2 layers of foam with a layer of glass (various weights to test) to create a “hard” trailing edge & a pointish leading edge.


For stiff fins, a straight uni directional cloth is much better than a woven type.

See diagrams below (straight and woven uni directional)

Photos of both sides of straight uni directional carbon - showing glue lines that hold fibres together.

You need at least two layers of unidirectional fibres at a bias of about 30 degrees to each other, otherwise the fin will allow too much twist when sailing in waves. Three layers is preferable - two biased and the outer layer in line. Best made in a mould.

Sorry so long getting photos organised, Jon

thanks for the suggestion