I have an 11’.6” a Bic WindSup. I am planning to replace the rear standard fin with a more performing fin, because the Dolphin is too small , both on account of the surface and the length/depth : it does not have enough bite and, even in moderately choppy waters and moderate winds, the directional control of the board is not great. The board tends to side slip and swirl a bit on the top of the chop, unless the water is flat and the winds light.I believe that it is mostly on account of the rear fin, even if my technique could be better.

I am being offered a 2nd hand 33 cm( 30cm) weed fin. Just looking at its length and surface the difference is considerable. I expect more lift and control, but the rake angle is about 40 °. Huge ! I am not used to it and, aside from the weed factor( there are no weeds anyway where I sail) I wonder if, due to this rake angle, the difference from the Dolphin fin is really significant enough to justify the purchase.
I wouldn’t exchange 4 quarters for one dollar bill!..

The plus of such fin is that it would allow me to launch the board in relatively shallow waters with a rocky bottom, where a more vertical fin would be damaged or even broken.

I’d be using it with either a Sailworks Race 5.6 or with an oldish N.P. Garda 6.2., the latter, because of its old longboard-compatible design of the 90’s has much more power in light winds than a conventional modern planing sail of the same size. It actually feels like an 8.5. I know from experience and I’m happy about it.

The same for the Sailworks 5.6, because I modified it by removing the sticky cams to allow full, free rotation and a tight leech. The result is a fuller shape and more power. With only a 5.6, the WindSup sails easily in 12 knts winds , unlike previous shortboards which required much larger sails or stronger winds to take off. .

Under these conditions, I wonder if the above-mentioned weed fin is a good match for these sail sizes and if I should expect a better performance on the WindSup, compared to the Dolphin fin.

Thanks

Francone

The weed fin is about 5cm longer. In theory it should perform better, of course a weed fin doesn't turn as well, perhaps not a concern. The true depth on these 2 fins won't be much different, you would need to go to a smaller weed fin..

bin the 10", get a good fin and use the side boxes to really improve performance PLUS This would give you even better shallow water capability.

the sails you quote.. You removed the cams. .? With all the options available WHY have a sail and remove the cams?


compared to the FCS Dolphin fin ITS PLASTIC right ?, just about anything would improve.

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forceten said..
The true depth on these 2 fins won't be much different, you would need to go to a smaller weed fin..

bin the 10", get a good fin and use the side boxes to really improve performance PLUS This would give you even better shallow water capability.

the sails you quote.. You removed the cams. .? With all the options available WHY have a sail and remove the cams?


compared to the FCS Dolphin fin ITS PLASTIC right ?, just about anything would improve.

Since the true depth on these fins won't be much different, as you say, I suppose you mean I'd have to go to a larger ( longer? fin ), not a smaller one, in order to get a longer depth? Of course, I wouldn't do it, because a longer/larger fin can put too much torque on the Bic fin Box ( US box) and may be pull it off, without counting more risk of damaging or even breaking it in shallow water.

Incidentally, which one is more relevant performance-wise : length or depth? If the depth is the same in these two fins, I suppose what makes the weed fin I mentioned perform better than the Dolphin is its length, in addition, of course to its larger surface. Am I right?

Regarding the cams removal, well, the 5.6 is an older Sailworks Race, a bit tattered, but I didn't want to buy a new one . Its cams were a bit sticky, this is why I removed them. I also shifted the central battens back and away from the mast by about 3-4". This way, the sail rotates perfectly without needing tons of down-haul. The end result is a tighter leech, which injects more power into the sail. I can feel the difference, because without these modifications, I was never ever able to use a 5.6 in 12-15 knts winds, as I do now. A tighter leech means, of course, a stiffer sail tip, but this is not an issue to me, because I normally don't sail in strong winds and gusts. When the kite-surfers are happy, it is time for me to stay home or get back to shore..

The sail has considerably more shape now. Also, the WindSup, akin to a longboard, is considerably longer than a shortboard. This facilitates its forward motion in light winds.
This is why I moved to a WindSup and I am happy about it. Perhaps it won't go as fast as a planing shortboard, but I preferred to trade off speed and planing for better light winds performance, stability and, in the end, for more T.O.W.

Francone

www.makanifins.com/pages/windsurfing-fin-selector

may help some. Because the length , weed fins don't seem to be measured quite the same, the areas are seldom posted, so from a visual perspective ya can't say a fin has more or less, without measuring.

if you draw a line the length of the Dolyphin fin, and the same for the weed fin you are considering at the approximate angle the depth
should be similar, depth in this case is the point where the fin would touch the ground.
why not use the side boxes , use say a 18cm with 12cm thrusters ? Using some nice fins this should give you more area and solve the issues...
hey what ?


sounds like Bruce Peterson should consult you on sail design.LOL

Anyway, us box, you cannot go longer than 33-34cm depth, then the torque will but the box in trouble...though not in light winds. Find a standard G10 free ride fin of about 30cm and you should be ok, I guess. when looking at weed find, the importance is the surface, not the depth.

note that I have no clue what is the windsup bic, nor its std fins.

The BIC WINDSUP, IS 11'6",

the supplied center fin is a USBOX, 25.4cm FCS fin, of extremely basic nature.
the board has the option to use FCS side fins, so thruster set up. They don't come with.
the board also has a retractable centerboard/ dagger.

for windsups it's a decent board, not on a par with the premium products.
in Sweden they have K4s..?

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forceten said..

why not use the side boxes , use say a 18cm with 12cm thrusters ? Using some nice fins this should give you more area and solve the issues...
hey what ?


Yes, I have been considering the two side-thrusters option, too, but somebody pointed out that they are made for surfing, not windsurfing. Also, the planes of the two side fins are not quite parallel, but converge slightly , a sort of toe-in, and this may brake a bit the board. Besides, I thought that the soft plastic material and their shallow depth may not be as good as a real, long and stiff fin.

Francone

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forceten said..

if you draw a line the length of the Dolyphin fin, and the same for the weed fin you are considering at the approximate angle the depth
should be similar.

You are absolutely right. The Dolphin looks so much smaller, but in reality its length is just about the same as the weed fin I am talking about, only 3 cm shorter ( 30 cm instead of 33 cm).
I guess what makes the difference is its surface : the weed fin is about 3 cm wider than the Dolphin at the fin- box insertion point and even if it is tapering down, it is visibly larger all along than the Dolphin.

May be, just for the fun, there is a way to calculate the area of each by using calculus ( indeed calculus is exquisitely designed to find the area of irregular geometrical shapes) but it would be too complicated . I reckon the weed fin is about 1/3rd larger in surface than the Dolphin.
Why, I wonder, don't the manufacturers indicate the fin surface in the specs?

Francone

That board probably has quite a bit of tail rocker which could be a lot of your problem trying to blast around in flat water. And you really don't want to use weed fins unless absolutely necessary.

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trace outline as shown.
draw parallel lines from starting point of fin to bottom, 1/2 cm apart.
Mark the length across each line in cm.
add total of all lines, divide by 2 = the area in square cm, or cm2.
to convert to inches multiple the area that have in cm, by 2.54

mauiultrafins.com/faq/

same as above, but uses 1/2 cm then 1 cm lines, the above is more accurate.

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Beaglebuddy said..
That board probably has quite a bit of tail rocker which could be a lot of your problem trying to blast around in flat water. And you really don't want to use weed fins unless absolutely necessary.

Could you explain why I shouldn't I use a weed fin ?
Regarding the tail rocker:
1. what is the connection or interaction( if there is one) with the weed fin issue?
2. Indeed, my WindSup has a tail rocker,( if by this you mean that, with the board lying flat in the central part, the tail starts to rise a little) , but why is tail rocker a problem in flat water?

Thanks

Francone

The fin boxes have toe in, and cant , cant means they angle outwards towards the rail.

Pray at tell why Simmer Fanatic Witchcraft Patrick RRD JP Tabou Starboard Naish Goya Quatro all production boards have toe in?

and don't use long fins, rather 3 or 4 small on wave or FSW

multi ti fins have been popular since 2007 and continue to expand.


i wonder how much time the development riders have windsurfing on windsups...