Fins etc.

[Admin]

Was over at the Nelson factory with Bill Foote today looking over Bill's and Greg's (CAD tech Guru) shoulders as they made the final computer mods on the next gen 14's.  These are some upsized and modded versions of Jeremy's board that has it's own thread going (at last weigh in, the deck and rails were on his board in full carbon and it had just cracked 13 lbs and already felt strong!).

While there, I talked to Mark Nelson, and he ordered us (Chan and I) some of his new Stand Up race specific G-10 fins for these new Foote shapes.  They are eliptical, thinly foiled 20 cm fins that he has been working on.  I asked if it would be possible to do them in Powerbox (through the deck to reduce all of the underwater sloppiness) and he said no problem.   Powerboxes are fixed position, but that should be no problem as we have the spot dialed in now from my current 14, which we all have a bunch of days on. 

I'll let you know how it goes.

[Dwight (DW)]

 Powerboxes are fixed position, but that should be no problem as we have the spot dialed in now from my current 14, which we all have a bunch of days on. 

What happens when a fin is too far forward, or too far backwards with a 14 ft board?

I located my fin just guessing, based off photos seen here. Any tips on where to put the fin on my next garage built board?

I'm using Chinook boxes. Way stronger, and shorter than normal surfboard boxes.

Thanks

[Dwight (DW)]

Was over at the Nelson factory with Bill Foote today looking over Bill's and Greg's (CAD tech Guru) shoulders as they made the final computer mods on the next gen 14's.  These are some upsized and modded versions of Jeremy's board that has it's own thread going (at last weigh in, the deck and rails were on his board in full carbon and it had just cracked 13 lbs and already felt strong!).

While there, I talked to Mark Nelson, and he ordered us (Chan and I) some of his new Stand Up race specific G-10 fins for these new Foote shapes.  They are eliptical, thinly foiled 20 cm fins that he has been working on.  I asked if it would be possible to do them in Powerbox (through the deck to reduce all of the underwater sloppiness) and he said no problem.   Powerboxes are fixed position, but that should be no problem as we have the spot dialed in now from my current 14, which we all have a bunch of days on. 

I'll let you know how it goes.

Another cool source for fins, for you lucky Maui guys, is Maui CNC, part of Maui Fins. They made some custom kitesurfing race fins for me to Ken Winner's specs. You can tech out with them and the prices are reasonable too.

[Admin]

What happens when a fin is too far forward, or too far backwards with a 14 ft board?  I located my fin just guessing, based off photos seen here. Any tips on where to put the fin on my next garage built board?  I'm using Chinook boxes. Way stronger, and shorter than normal surfboard boxes.

Hi DW,
I am no fin expert, but this is something that even I could notice.  When the fin is too big, too far back (or worst of all, both) the board can get REALLY unmanageable.  I think a really low rocker parallel railed board can make this even worse.  It will want to hold a line no matter how hard you sweep stroke, or try to body English it.  You basically are going where the swell an wind want you to.  I had that on both my C4 and my Foote with the original fins and positions that I tried.  A smaller fin and a forward position made all the difference.  I am not sure that we are going to get the same fin advantage as on high speed planing sports like windsurfing, but I think the wrong set up is a crippler.  I heard that some of the prone paddleboarders are using flat fins (no foil at all).  The idea of a really thin foil sounds smart to me.  I really like the clean powerbox setup for downwinders.  Sometimes it seems like the difference in making or not making a swell is so small.  That is likely just me, though 

PS:  The leading edge is at 21 inches.

[DavidJohn]

Just a thought...

It's my understanding that correct fin foils are...

Thin for fast.. (really fast).

... and thicker for slow (us).

Using a thin foil for a slow board might result in cavitation (drag) and even spin-outs.

I think thicker foils might be the way to go.. even if it seems that there may be more drag from them.

Any fin experts on board?.. I think Stuey's new fins are a pretty thick foil.

DJ

[Admin]

Here is what I remember from the chat about the prone paddle guys:

Fins with heavier forward foils give more lift at lower speeds but drag more.  Thinner fins provide less lift but drag less.  For guys paddling with their hands or relatively small paddles, it was theorized that the drag is more of a downer than the lift is an upper, as we don't have huge sails, forceful waves, or similar power to overcome the drag, but we do have big, glidey, high volume boards to do some of the work.  That is how I remember it, but someone please jump in if I butchered the concept.

[noa]

very good thread. fins are of utmost importance and we have yet to really understand what works and why for downwind boards.
i always thought that thin foils would work best for us. since we are pushed by the wind and waves, and our paddling mainly gives forward propulsion, we don't have so much side loading of the fin. so a thick foil would not really get the chance to work in creating lift. it would on the other hand produce drag.
however, recently i read something from Mark Raaphorst saying that thin foils could cavitate and for the speeds we're going thicker foils worked best. how would a downwind board cavitate ?
all i now know is that i'm kind of lost on this subject.

[shapeshifter]

we are sometimes dealing with water flowing in reverse... the same direction we are heading on a downwinder as the bumps swell up from behind to push us along. could be totally wrong but i'm thinking that this may be when the cavitation may occur in the case of the thin foil concept.

[footemaui]

All I know is Jeremy's fin is going on crooked on his new board.. It's called a handicap... Not

[Dwight (DW)]

Regardless of the foil we choose, it's probably best just to make sure you have a good foil. Avoid a sloppy hand shaped one and get a CNC cut fin.

[stuey c]

Regardless of the foil we choose, it's probably best just to make sure you have a good foil. Avoid a sloppy hand shaped one and get a CNC cut fin.
[/

  "Sloppy hand shaped"?  I can still hand foil a fin as well as or better than any computer cut one I've ever seen. It's called knowing what you are doing..........quote]

[DavidJohn]

Hey Stuey.. What's your thoughts about all this fin stuff?

I know these modern 'pointer style' fins are all the go now and I know they are very low drag.. But...

I'm thinking that they might be trying to create lift and make the board want to 'rail up' when on a runner.

I'm thinking that something with more rake or maybe wider in the base might work better.

What do you think?.. Have you tested fins much in the Pene?

DJ

[Admin]

Picked up the finished product today, and they are ready for their new 14 foot homes.

[DavidJohn]

Very nice.. They look like 10" pointer fins to me.. I love that classic Spitfire wing shape.

Are they both the same size.. and what size are they?

DJ

[Admin]

These are the same (one for me one for Chan).  They are 20 cm (just under 8 inches), narrow and very thin, so if they will hold a direction, they should be pretty slick.