Ventral fins are hideous on downwinders, for the same reason that centerboards are--they make the board unpredictable and cause it to round up violently in big swells. Moves the center of resistance forward of the paddler and makes a big, nasty pivot point. I get what Pierre is talking about, having a small classic centerboard that you can kick up in mid-stroke would be pretty cool, and if you could make it deeper in crosswind that would be fine too. He's not talking about being able to flip the board over and swap the fin, he's talking about a true centerboard--or more accurately, a daggerboard.

But yeah, for the most part, that complexity has been eliminated from board sports as technique refined. You won't find windsurfers relying on centerboards to go upwind anymore, even though they made it very easy and efficient.  My first windsurfer had a centerboard I could kick down. It could point like a sailboat with the centerboard down, but it was a sissy thing to use, so I left it on the beach, dug in my rail, and struggled to make way. Such is the force of ego over reason. The mechanisms were minimal drag. They had retracting covers over the slot that were flush to the bottom. Probably less drag than an empty ventral slot.

My ancient 12'2" Starboard has a Tuttle box for a daggerboard--currently filled with a blank and waxed over. the old 12'6" starboards came with either a Tuttle centerboard or a foot-operated daggerboard. How soon you guys forget. Those were intended for sailing the boards, but I experimented with little ventral Tuttle fins a back when I first got my 12'2". When rocks were new, paddles were wood, and paddlers were iron. Arrggh.

Burchas--SIC did it wrong. Mark has a remarkable willingness to develop something to a remarkable degree before he tests it. He makes these gorgeous, perfect, incredible mechanisms and then puts them in the wrong place because he didn't try ten quick and dirty designs before he did the beautiful one. He did his front and back steering rudders with the front rudder too far forward--ahead of the start of the nose rocker. So when the nose came up in a swell, the rudder went high and dry. If you made some steering correction while it was in the air, guess what happened when it dropped back into the water. I think the only person who could ride that thing was Livio, and he hated it. Move the front rudder back behind the nose rocker so it always stays engaged and you have effortless linked turns with minimal rudder action. Minimal rudder = less drag.

Same thing with the switchblade ventral fin (not a daggerboard). Gorgeous execution--I nearly fainted with lust when I saw the mechanism. Little to no testing. I think Mark just lost interest.

Don't get me wrong, I'm not saying ventral fins don't make sense, I like them. But when you move from the upwind or crosswind leg of a course to the downwind leg, you're likely to wish you didn't have one. If you could step on a handle and make it disappear--you'd do it in a heartbeat. And when you go to turn around a buoy you better not have anyone outside you--this truck makes wide turns.

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I think this video will help some!

Been thinking about re inventing th wheel today and then maybe later on - I'll come out with the automobile

Jesus! 

Hey! I really liked those canard fins! But they were glass over a foam core and couldn't handle my bashing.

And yeah, I know, they were making good on my shitty jump landings, but they did a great job of it.

Cool video Larry.

Again, don't get me wrong, I'm sold on three fins for flatwater. Not quite so much for downwinding, though it might just be my rudder addiction. And I like Ventral fins for flatwater, upwind and crosswind. But they suck toads downwinding. And yeah, I know, if you get half the board out of the water so the fin clears they will pivot turn. But that's one more thing to deal with in a race. My turns aren't that good, and my crappy balance rules my decision-making. For other people, it might not be a big deal at all and could be totally worth it. I can't speak to that, I just give information about what I find to be true for me.

Henrick--might be partly a board difference. My four-fin board is a 2015 Blackfish, which has very straight rails and a square tail. Pushing on the rails does nothing to steer it. I wanted to use it for downwinding, so I did a lot of painful experimenting. The only thing that worked for me was a single Squirrel fin and a similar design tip-weighted fin that Larry sent me. I can steer with those, but it's still not quick enough for Columbia River downwinders with me as the pilot. Alyson Fromm absolutely rocks on hers, but she's using a single fin as well for downwind.

Thaks for reminding me of that switchblade ventral fin. I need to beg Mark to give me one. I'm sure he has all the stuff to make them, and he might have a prototype or two hanging around.

This has me thinking about front steering again. I'd like to perfect that. I think Mark was on the right track but the failure of the first try discouraged him. It was a gorgeous mechanism and he did the front rudder right for sizing, using an FCS fin box to make it replaceable. Front steering rudders can be very small. The best way to do it would be an RC rudder with separate servos for the front and back rudders. You could then set trim, control proportion and expo independently, switch between front, back, both and/or counter steering, and probably even change proportion and trim on the fly. A lot to screw with, but with a microcontroller I could use some simple commands to do complex things.

Rear rudders are drag pigs, but front rudders actually reduce drag because they take turning and course-maintaining load off the rails and don't follow the snake trail that upwind/crosswind generally causes with foot steering. I did a wind vane-steered front rudder on an old Glide 14 long ago. It was wonderful upwind and crosswind--felt like it had a motor helping me. Downwind it was a horror. It tossed Rod Parmenter all over the river and he has the reflexes of a cat. Hilarious to watch for me, not so funny for Rod.

  It isn't. Cross bow draws require a little more effort but are still easy enough. Pivot turns aren't effected once the front of the board is up a few inches. It doesn't have to be 45degrees out. Even given any problems turning, which I don't have, the rocket ship starts make up a lot more of a difference.

Yeah when I used that Eradicator with ventral it turned slow with a cross bow but fast stepping back and lifting it out of the water for zero drag.

DW ventral is no no around here.  No one we know uses one.  Lifting or tipping it up like a daggerboard might work somehow tho.

I am going to have to agree with Warmuth and Burchas on the cross bow pivot turn with a forward ventral fin on board.

I find the cross bow turn on my 2017 Blackfish running with the single 6in Allison Stinger to be quite easy and relatively fast, with no step back and elevation of the nose. It is my go to type of turn for the same reasons documented by several in this thread.

What I do believe can make the difference is a cross bow pivot turn, properly executed.

Crucial for fast execution for me is lowing my center of gravity significantly and rather exacting placement/movement of the paddle. With you're lower half planted very low, and quick reversal of the paddle upon completion of the turn can save precious seconds, and avoid balance errors when making a series of quick, short paddle strokes to get back up to speed.

I rarely see the cross bow pivot turn executed with confidence and speed. It's a practiced skill, much as one would expect to do trying to perfect the step back, error prone, pivot turn.

The cross bow pivot turn just hasn't been deemed "sexy" by the elites.