I have just got my hands on a 60cm wide JP Slalom V 92 and currently my smallest fin is 34cm. I weigh 90kg. I am looking to buy a smaller fin for GPS speed sailing to be used with my 5.8m race sail. The board is quite a bit wider than full-on speed boards so I wasn't sure how small I should go. I like the look of the KA speed fins (swept back too for weedy places) but they seem too small for my board. I'm thinking that I probably should just get a slalom fin in the 28-30cm range. Does anyone have any words of advice or experience trying to make smallish slalom boards go fast? Thanks
A Time machine 26" would possibly suit this board. Its a great all round speed fin and works well in messy conditions. I use mine on a Kids Pro S and a CA40 with no problems. Its great for high speed jybing as well. Hope this helps
I personally I wouldnt go smaller than a 30cm maybe a 28.
Lots of good fins Brands out there C3, Techtonics, Debs, KA, TM, Vector.
Iv been using the C3 fins and are very happy with them good top end and plenty of control. http://www.c3-fins.com/C3_web/home.html
ta Vando
I have the GenV 92 and it works well with the Select Caspar 29 - 40+. I weigh 110kg and use it with a 6.2 so you shouldn't have any problems. If you use it with a 6.7 a 31 SL7 is perfect, the board doesn't need a big fin and has good directional stability.
I wouldn't rush to go too small. This board and a lot of newer slalom boards still need decent fins to get out of the water to go fast. Martin Van Meurs has run this board almost to 38ish knots with I think a C3 Venom 38.
Would look at C3 Venom 32 or JP Slalom 32 for going quick off the wind. Venom felt nice and the bigger JP's I've used in it feel great for slalom.
You'll love the board though. Easy to go fast on in lots of different wind and water.
Sam.
I got a new JP Slalom 32 and used it in my Fanatic Falcon 90 (60cm wide I think) last Saturday. Wind was off and on 10-25 knots. The fin let go a couple of times but that was user error moreso landing sideways after coming off the top of chop. It certainly felt more secure than what I'd been using (a Techtonics Tomcat 32, possibly a copy
) but it did have a bit of a whistle so will need some tuning. The water was way too choppy to attempt full on speed runs so I'll reserve my full judgement on it till I can but so far I would definately reccommend it, mostly so because of its price compared to some of the other big name fins. Also Micah uses these stock fins to race on, not a bad testimonial!
Personally though I don't think you'd need go any smaller than a 32 unless you were in very flat water and were using a around a 5.0 sail, in which case you'd probably be out on your speed kit anyway!
You've got some pretty fast repliers there but they don't seem to agree. For the same proportions a 32 cm fin has 50% more area than a 26.
You can go too small particularly if you don't go fast enough or deep enough off wind. To generate a given amount of lift at a certain speed a smaller fin has to be run at a higher angle of attack. This directs a bit of the lift in the backward direction - induced drag. Too big and the friction of the water moving over the surface of the foil dominates.
It just so happens that because induced drag decreases with the square of velocity and friction drag increases with the square of velocity, the minimum is when they are both equal. If you are somewhere close to the minimum you're said to be in the drag bucket.
Thus small fins are good provided you're going fast enough and at a deep angle where lateral forces aren't as great.
If you told the speedsters how fast you were planning on going they'd probably get closer to the same length.
But hull drag is significantly greater than fin drag - so if your fin length/footstrap leverage combination allows you to better comfortably trim that big draggy board you'll probably go faster.
That's just the old rule of thumb - " Use a fin as long as the distance between the centres of your front footstraps"
Check that measurement on your JP... and go with a 32cm fin.
Looking at the width of the board I think Sams on the money 32cm for off the wind speed
I have the same board and have been using JP fins.
I asked the same question on the NP Maui forum and recieved replies from Kevin Ozee and Martin Van Meurs. Kevin basically said anything other than 34 is not worth it. He reckons smaller equals not enough lift and bigger was too much drag.
MVM advised that with C3 or JP you can go bigger than normal.
Heavier sailors can get away with bigger fins. Have used 6.7 RSR and 36 Jp to help with planing. Then 6.2 RSR with Gen III JP 34 and as Sam said it felt slippery/nice.
Admittedly this is from your average punter so like everyone else says a 32 for speed would be cool.
Hope this helps.
Thanks guys for all your advice which has been very helpful. The 92 is my smallest slalom board which is doubling as my 'speed' board. I don't have a speed board (I'm drawing the line at 3 slalom boards, 1 freestyle wave & 1 wave board!) but am going out to the Green Island Speed Week next month anyway - hence my posting. I managed 36.9 2sec peak on my first ride on it with a NP RSR 5.8 and my JP III 34cm fin last weekend but felt there was room for improvement. I was starting to lift off at times and felt a smaller fin might allow me to keep the power down a bit longer with that sail and hopefully gain an extra knot or two. I'm happy the 34cm fin will be good for slalom with the 5.8 but from all your advice I'm now thinking I'll get myself another fin in the 31-32cm range for those maxed out 5.8m days on a flat speed strip. Any further advice gratefully received though.
Where are your footstraps?
I use to always go straight to the back but at Sandy Pt last year I moved the rear strap one hole forward and grabbed another 2knots almost straight away. The lifty feeling I was getting disappeared and was able to get the drive out the board and fin that I was looking for.
Sam.
Hello,
I have a fanatic falcon 89 (very similar size to the jp 92) and use a c3 32cm venom fin. Very fast and secure even in 10 - 15 knots with 6.6 it seems to have good bottom end and great top end. Hope this helps.
Cheers,
Carl
