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-   -   Rio M fin upgrade? (http://www.star-board-windsurfing.com/forum/showthread.php?t=13707)

Bruntoj 10th October 2011 09:21 PM

Rio M fin upgrade?
 
I'm a beginner who's had maybe 5-6 planing days on a Starboard Rio M. It comes with a 16"/41cm Drake fin and I'm looking to size up the fin. The Star-Board Rio tuning page recommends "Drake R13 Race NR 540" but they're hard to find on the web so I have a couple of questions...

1. Do they still make/sell these fins? In the USA?
2. What would be similar to a Drake R13 Race NR 540?
3. Is it true that I can use any Tuttle fin in a Deep Tuttle box?

Rider 93kg
Board Rio M (approx 200l)
Sails: 9.5 (& 7.5)
Typical winds: 8-14 mph Southern California.

Thanks
John

Roger 11th October 2011 09:20 AM

Hi Bruntoj,
They don't make that particular fin in the USA, and Starboard Fins are usually only shipped with
the boards.
There are several aftermarket fin companies that make fins in about that size that would work quite well.
Yes, you can use a std. Tuttle fins in a Deep Tuttle. You will need some fin bolts that are 20 mm longer
(20 mm= approx. 7/8").
The fin root of a std. Tuttle is the same size and has the same angles as a Deep Tuttle fin root, but the
Std. is simply shorter by about 20 mm.
Roger

Bruntoj 11th October 2011 10:27 PM

Hi Roger

Can you suggest a couple of specific fins, or help me out with some keywords? To my beginner eyes I'm seeing fins in Formula, Race, and others that look the same shape to me...

Roger 12th October 2011 07:12 AM

Hi Bruntoj,
Check out the True Ames Sweeper fins;
The curved planform of these fins will make learning to jibe a bit easier.
You have the centerboard for going hard upwind (if required).
The Sweeper can be ordered in Deep Tuttle.
54 cms should give you excellent performance on your Rio M.
What happened to the Drake NR 540 mm that was supposed to be supplied with
your new board?
Any sort of 52-58 cm vertical pointer fins will work well on the Rio M.
Actually, you might want to look in the used fin bins at you local winsurfing retailer.
There are lots of stock 50-60" Tuttle base fins out there that will work to get you
planing better/earlier than the 41 cm Shallow water fin you are using.
Roger

imbrooks 12th October 2011 08:16 AM

Hey Roger, how long is too long for the Rio M? I read on another site where somebody riding the Bic Nova 180L has a 60cm and suggests even going w/ a 70cm formula fin.

Any guidance? I need to finally upgrade from the stock Rio M fin as well.

Thanks -
Brooks

Roger 12th October 2011 10:38 AM

Hi Brooks,
I think the Nova is a bit wider in the tail than the Rio M.
Tail width (actually rear footstrap offset from the centerline) would have alot to do with
how long a fin span you can use and still have control.
I've used the Rio M with a 60 cm and it was quite good.
I would say that 60-65 is probably more fin than you need unless you are trying to get
planing in ultra marginal windspeeds (i.e. < 12 knots on a Rio M).
Back in the day (early 90's) we used various 70 cm fins in the very early 85-95 cm wide
Formula boards (F-155 etc) and they helped with early planing, but got a bit out of control
in windspeeds > 14 knots.
Hope this helps,
Roger

imbrooks 12th October 2011 11:13 AM

Hey Roger:

Found a 58cm fin online for a fair price, so think I'll go w/ that :)

Let me ask, what does it mean to 'lose control' w/ a larger fin at higher windspeeds?
I know small fin/high wind can lead to "spin out". What happens to a large/formula fin at highspeeds? I would think they would be rock-steady. No?

Roger 12th October 2011 11:42 AM

If you have a super wide (100.5 cm wide) formula type board with the footstraps > 40 cm off center on each side, you can control a 70 cm fin pretty well, even in high winds and at high speeds.
When the fin size gets too big, and the footstrap offset does not provide enough leverage to really control the fin's attitude, you get the dreaded "tail walking" (can happen with smaller fins at extreme speeds also).
The board tends to come up off the water slightly and oscillate rail to rail.
You will only understand this phenomenon by experiencing it once or twice I can assure you.
You simply lose the ability to keep the fin at a controllable attiude.
You normally simply change down to a smaller fin with perhaps a less powerful foil profile and things
are good again, even at hgher speeds.
If you want to "experience" tail walking and all it's scary perturbations, get someone with a 40 mph motor boat to give you a tow. Stay inside the wake and at some speed, your fin will reach it's critical control speed and your board will indeed "tailwalk" and dump you in the water at fairly high speed.
The big 70 cm (it's in the rules that 70 cm is the max.) formula fins, on 100 cm wide formula boards, with some of the best formula sailors in the world, can go up around 30 knots in some pretty knarly conditions with 9-11 m2 sails before they get to the tailwalking stage.
On narrower boards, big fins become "out of control" at much lower speeds.
All of the WS speed records have been set with really tiny fins. I have a set of 7"-9.5" True Ames Speed
Serious fins that are wonderful...if you are going fast enough.
But you have to sail a bit off the wind and stay off the fin when getting going as they will spin out in a heartbeat at slower speeds. Get up over 25-30 knots and they are solid as a rock.
Roger
P.S. The 58 cm should work nicely in your Rio M!


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