RealSurf Surfers' Forum

I made myself a twin keel fish. 5' 3 1/2" x 19 7/8" x 2.4" about 30 litres (flat deck adds a lot of volume) Glassed on keels. Keels are 6" base x 5" high.
Bottom is a subtle double concaved vee. Low to medium volume HPSB rails




Ok first couple of surfs on it were perplexing - it would bog and times and then take off like a rocket at others. I thought this was probably due to the fact I'd used a more HPSB tail rocker. Because the fins are at 7" this put curve too far in front of the fins so rail drag in turns and fin lift were tipping back and forth, rather than working together.
I solved this problem by adding small twinzer canards in front of the keels. This bought the fin lift in line with rocker curve and the design was suddenly amazeballs.

I'm keen to keep iterating the design PM me if you want the Shape 3d file - I've updated it to move the tail rocker lift back. If you look at the pic from tulla tub you'll see the lift from the fins + canards is making the board plane in the back third. I think the nose would catch without the canards so I've lifted the nose rocker a pinch so you could run the board with just keels. Although I think the canards make the ride a little more civilised,

You can definitely see the water squirting out off the canards in the last photo. Nice looking fish.

I like the last shot.

but the hull still looks under-powered - ie not attaining the speed necessary to fully engage the canards.

steve shearer wrote: ↑

Sun Jan 10, 2021 5:49 pm

I like the last shot.

but the hull still looks under-powered - ie not attaining the speed necessary to fully engage the canards.

Yes I'm thinking the vee is exaggerating the problem with the rocker curve in front of the fins. I think flattening the rocker curve slightly will fix that so I'll probably do a version 2 (theres only so much you can do with fins to fix a fundamental problem) I haven't ridden a vee bottom before, it feels buttery smooth going rail to rail though, so I'll keep that.

new rocker:

Looks good Pinny.
How tall are you?

Nice pinny.
How cool is the pattern of the wave on the last pic with you saying ooooft! into it?

That's because Pinny has just ripped the top off the wave with his canard cutback.
So basically the canards are doing what a normal quad setup on a fish would do more or less?

I'm 175 cm. Most people will tell you canards direct water flow around the big fins. I think on a surfboard they do that but also move the fin engagement forward slightly and tame a twitchy twin by extending the turn side base.

This board feels nothing like a quad BTW

buddy wrote: ↑

Sun Jan 10, 2021 10:02 pm

Nice pinny.
How cool is the pattern of the wave on the last pic with you saying ooooft! into it?

People could hear me saying "ooooft" from the shore

pinhead wrote: ↑

Sun Jan 10, 2021 4:41 pm

What's the best pool setting? I've tried intermediate but possibly there next week so was going to give advanced a crack. Is it significantly harder?

Great looking twinzer