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Sail V Fin Size

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Created by skebstebamal Monday, 13 Jan 2020
skebstebamal
QLD, 571 posts
Monday , 13 Jan 2020 5:25PM
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Hello breezers,

I'm hoping someone can shed some light on fin sizing. I'm back sailing after a 20 year hiatus and it appears people run bigger sails and smaller fins these days; I currently run the following;
2009 120l JP xcite ride std epoxy (only board atm) I'm 100kg. generally lake sailing conditions. (flattish)
- 7.8m loft sails Switchblade sail. I run a black project 47.5 dragon freeride in lighter airs to get through lulls and a 42cm tectonics Raptor for constant winds.
- 6.4m NP EVO IV, I run the 42cm Raptor when its on and off again to get through lulls, or a 38cm black projects race when its constant. If it gets really hectic I drop to a small weed fin I have that has less lift than the BP. . .not sure of its size.

Does this sound reasonable? I've sailed enough to know that if I'm tail walking and can't keep the board in the water I will fin down if the sail feels ok, or drop down both.

ATM I feel like I get overpowered by the sail more so than the fin. I'm a bit lost as everyone seems to hold massive sails down compared to me, and I am typically substantially heavier than the comparison sailor. I may be just not getting the speed needed to let the sails breath in the gusts hence the sail feels too large. .ie I am a slow kook.

Thanks in advance : )

Subsonic
WA, 1857 posts
Monday , 13 Jan 2020 4:12PM
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With the sails you've mentioned, the biggest fin i would ever consider is the 42. But even thats a bit big.


what width is the excite ride? Thats a factor too. But if i were you i would try going a smaller fin to sail combo than you currently are. Try the 38 with the 7.8.
the problem might not be isolated to fin/sail combo's either. Theres plenty of rig tuning problems that may make the difference.

Tardy
3286 posts
Monday , 13 Jan 2020 4:34PM
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I don't like telling people ,hey you have the wrong gear ....but this is what works for me @ 95 kg .on the east side ,

8,5 &45 fin 140 litre board

7,8 & 42 fin 125 litre Tabou rocket

6,4 & 36 or 38 fin ,115 litre slalom board .

this can vary if its a pointer or swept back fin ,hope this helped .

skebstebamal
QLD, 571 posts
Monday , 13 Jan 2020 7:18PM
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Thank you subsonic and Tardy.

Good to know. I might drop to the 38 as biggest for the 6.4 and try running the 42 AND 38 on the 7.8... will bench the 47.5.

I think its too slow anyway, feels like has a lot of drag.. is a little raked and whistles as soon as it gets hooking... sooo annoying.

Thanks!!

powersloshin
NSW, 1071 posts
Monday , 13 Jan 2020 9:26PM
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Are you sure that you give the sail enough downhaul? it is possible that it feels heavy if you don't have enough. The leach should be floppy, the third batten from the top should point into the mast, not under, if you get a gust it should accelerate without overpowering you. Try and compare how the others are rigging.
I use a 44 carbon on 125 slalom board, but your board should have a narrower tail

forceten
875 posts
Tuesday , 14 Jan 2020 12:36AM
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Size, 34 smallest 42 by far the largest.
Then I did this which , only considers the sail size and math, ignoring , board, weight of sailor , sea state, experience etc etc.

sail size 7.8 x number 5 ( 5 being a constant ) = 39 plus the number 3 = 42cm size for 7.8 sail. Three can be changed to alter the list of factors, some of which are listed above.
sail size 6.4 X 5= 32 plus 3 = 35cm fin .
Fin area is always a consideration, the same length can have have a different area, weed fins are weird also.

this also assumes that you aren't putting a 6.0 m sail on a 83 liter board. so this formula has no brain, you need to supply one.

skebstebamal
QLD, 571 posts
Thursday , 16 Jan 2020 12:56PM
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Select to expand quote
forceten said..
Size, 34 smallest 42 by far the largest.
Then I did this which , only considers the sail size and math, ignoring , board, weight of sailor , sea state, experience etc etc.

sail size 7.8 x number 5 ( 5 being a constant ) = 39 plus the number 3 = 42cm size for 7.8 sail. Three can be changed to alter the list of factors, some of which are listed above.
sail size 6.4 X 5= 32 plus 3 = 35cm fin .
Fin area is always a consideration, the same length can have have a different area, weed fins are weird also.

this also assumes that you aren't putting a 6.0 m sail on a 83 liter board. so this formula has no brain, you need to supply one.


classic. Do you need to be able to get planning to use that equation? or do you just change the constant to 69.



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