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Quad Fin Sizing & Setup
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Waterat Pat



Joined: 10 Apr 2000
Posts: 133

PostPosted: Fri Nov 09, 2012 7:00 pm    Post subject: Quad Fin Sizing & Setup Reply with quote

Okay so I finally got a Quad a very nice RRD 92l. It comes with 9cm fins up front and 16cm fins in the back. These work fine with my 5.2m sail but seem a bit sticky. I will keep them for my 6.2m sail but I am thinking of getting something smaller for my other sails. People have nice things to say about K4 fins so I am looking at 8cm shark tooth up front and a 15or 14cm Flex for the rear.
So whaddya think I weigh 200lbs and am curious what other sailors run on their Quads. Please include your weight and board size too. Thanx!


Last edited by Waterat Pat on Fri Nov 23, 2012 11:01 pm; edited 1 time in total
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U2U2U2



Joined: 06 Jul 2001
Posts: 3049
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Fri Nov 09, 2012 8:56 pm    Post subject: Reply with quote

Before I lose you with finmania I would say go all stubbie if doing the K4 thing in 15/8.

The sticky part of your description I wonder if that is the normal for this RRD and most quads compared to a single, slower to plane, so it could very well be you aren't used to it yet.

my RRD 74 Liter wave twin now a quad is too small for a comparison.So will leave that off. My weight is 155lb. 15.5 & 10 stable starting point



My Exocet 104Liter again quad conversion, is closer in size . 17//10cm K4s and 16/8cm the small ones are stubbies.

Several people rode this and 17/10 K4s worked to suit everyone, 5.0--5.5m. I used BlackProject Multi fins on this as well 17/13 or 15/13, these are rather small in area, but the BPFs are very good.

The K4s are noticeably looser , which you may are not prefer.
Of note the size of the shark is considerably smaller in area than the stubbie, the 9cm Shark has 45cm2, where the 10cm Stubbie has 66cm2.
K4 is coming out with asymmetrical fins , with built in toe of either 1 or 2 degree, 8 10 12 14 in size.

Considering the cost of K4, you maybe can afford to try several sizes.

I also used Makani 15/10, weed waves, they were too small at least that day.

Iam considering a 90liter quad convertible conversion, and would start with 15/11.5

you will notice I have a few K4s.



_________________
K4 fins
4Boards....May the fours be with you

http://www.k4fins.com/fins.html
http://4boards.co.uk/
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xander.arch



Joined: 23 Apr 2009
Posts: 169

PostPosted: Sat Nov 10, 2012 10:32 am    Post subject: Reply with quote

I swapped out the 16cm backs only on my tabou dacurve 74 for the smaller 14cm flexies. They made a great board even better. I also saved a bit by not getting the k4 fronts and at $75 I saved about 3 bills over a full g10 quad set.

In my opinion, if you are using 7-9cm fronts they are there for bite and not lift. So for me its important that the fronts have a thin low drag section like the tabou stocks do. I'm probably not really a good enough sailor to really know what is going on, but it feels like the flexy k4s coupled with the stiff g10 fronts create a dynamic where the fronts feel like they are part of board and the rears are like an extension of my feet.

Anyway, I really like how the k4s flex back on your top turn.

If you go for a more balanced quad with fronts and backs of about the same size then its probably much more important that the fins be the same.
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Waterat Pat



Joined: 10 Apr 2000
Posts: 133

PostPosted: Sat Nov 10, 2012 10:56 am    Post subject: Reply with quote

Impressive collection of fins U2. I heard about the toed in style K4 and am not sure that would work for me. Will probably make the board even tougher to plane while gaining some turning potential. I checked my RRD and it has no toe in at all the boxes are straight.
You seem pretty stoked on the stubbies and as you say they are bigger in area but I am looking to go smaller and it would be nice if the fins shed eel grass which is abundant on the West coast.
Where do you buy your K4 fins? I didn't see any distributor in the US.

Lastly are you making the slot boxes for your conversions or buying them?
I have some old boards lying around......

Xander I agree flexy fins for wave riding work because you can load up the fin in the bottom turn and the pop off the top when it releases. Thats why I want to try the K4 flex. My MFC fins are very stiff and feel it when sailing. How big a sail can you go with on your 14cm fins?

Thanks again for the replys!
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U2U2U2



Joined: 06 Jul 2001
Posts: 3049
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sat Nov 10, 2012 11:24 am    Post subject: Reply with quote

xander.arch wrote:
I swapped out the 16cm backs only on my tabou dacurve 74 for the smaller 14cm flexies. They made a great board even better. I also saved a bit by not getting the k4 fronts and at $75 I saved about 3 bills over a full g10 quad set.

In my opinion, if you are using 7-9cm fronts they are there for bite and not lift. So for me its important that the fronts have a thin low drag section like the tabou stocks do. I'm probably not really a good enough sailor to really know what is going on, but it feels like the flexy k4s coupled with the stiff g10 fronts create a dynamic where the fronts feel like they are part of board and the rears are like an extension of my feet.

Anyway, I really like how the k4s flex back on your top turn.

If you go for a more balanced quad with fronts and backs of about the same size then its probably much more important that the fins be the same.


you are probably a good enough sailor to know what works & what you like, in my case I suck as a sailor and can tell straight off if its an improvement.

On my RRD, Fanatic and Exocet Quads I have used different fin compositions between front and rear, nothing dramatic in feel between fiberglass, plastic .. K4s , but plastic is non flattering to what they actually are, RTM molded surf fins and G10.

The original Starboard Quads had fins that were as close to the same size,instead of rx 16 & 9, a lot of people liked that feel, but the FCS boxes on the rear were IMO a bad mistake. My friend has changed his rears to mini tuttle along with the fronts, and performed some other surgery, like toe in, rode this in April and it is one of the best ever.

The feeling from 4 the same size I feel is too planted , the quad is already stuck to the water, so I want something looser.

Since I have so many K4s I must like the loose feeling of them.

_________________
K4 fins
4Boards....May the fours be with you

http://www.k4fins.com/fins.html
http://4boards.co.uk/
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U2U2U2



Joined: 06 Jul 2001
Posts: 3049
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sat Nov 10, 2012 11:34 am    Post subject: Reply with quote

Waterat Pat wrote:
Impressive collection of fins U2. I heard about the toed in style K4 and am not sure that would work for me. Will probably make the board even tougher to plane while gaining some turning potential. I checked my RRD and it has no toe in at all the boxes are straight.
You seem pretty stoked on the stubbies and as you say they are bigger in area but I am looking to go smaller and it would be nice if the fins shed eel grass which is abundant on the West coast.
Where do you buy your K4 fins? I didn't see any distributor in the US.

Lastly are you making the slot boxes for your conversions or buying them?
I have some old boards lying around......

Xander I agree flexy fins for wave riding work because you can load up the fin in the bottom turn and the pop off the top when it releases. Thats why I want to try the K4 flex. My MFC fins are very stiff and feel it when sailing. How big a sail can you go with on your 14cm fins?

Thanks again for the replys!


BOYLOS in the UK I have used for purchase, helpful and reliable.
Contact :
Ellie at

boylos K4s(info@boylos.co.uk)

Steve Thorpe at the K4 site is the man, write him at
(bigyellow@k4fins.com)
IS the offical K4 site, and they only sell through dealers.
http://www.k4fins.com/

Their are several Canadian companies making slot box WEED fins

Makani has these for your weed problem::

http://www.makanifins.com/Windsurfing_Fins_Weed_Wave_Multi_Fin_p/wa001_w_quad.htm

or these from WIND NC ::
http://wind-nc.enstore.com/browse/fin,freestyleweed,windsurf/1

_________________
K4 fins
4Boards....May the fours be with you

http://www.k4fins.com/fins.html
http://4boards.co.uk/
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xander.arch



Joined: 23 Apr 2009
Posts: 169

PostPosted: Sat Nov 10, 2012 11:42 am    Post subject: Reply with quote

I've sailed this combo 80% with a 4.7 which is perfect. I've only tried it once with my 5.3 and it was surf and slog, but the fins felt maybe a bit small for the 5.3. I'm also a bit of a lightweight at 155 lbs.
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U2U2U2



Joined: 06 Jul 2001
Posts: 3049
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sat Nov 10, 2012 11:53 am    Post subject: Reply with quote

I get slot boxes which are Cobra made from Matt Prichard.

matt prichard(matt@pritchardwindsurfing.com)

tell him " Catpain" sent you.


I have been attempting unsuccessful to get some from Slovenia,

they make them for their boards and are really strong looking with inserts in the hole for additional strength and a internal hex head on the screws.

http://www.flikkaboards.com/

I thought about the possibility of making the slot boxes, but not pursued it any further, I don't see it as particularly difficult .

Compared to the ProBox surf boxes I install the slots are more difficult to get right, I made a guide to line up while being set in. I have set 8 so far, and pleased with results.
But if just doing sides to make a 3 fined board or adding 2 to make a quad from a twin I would prefer the ProBoxes, much easier way cheaper, and lots of fin choices, with FCS surf fins dropping right in, and K4s being soft , compared to G10, I can modify them to fit. Top left in the photo. A bit too time consuming but doable none the less.

Ref the toe in on the new K4s, I feel we are going to see much more activity in the area of toe, the Fanatic Quad,the production one has toe on the fronts, not a lot but .844 , with that little toe in 50/50 or dual fins are still probably best, but a 2 degree toed fin along with that would be noticeable.

Your observations on slower to plane have some merit, but with the right toe and inside foil on the fins, it improves greatly.

these are ProBox on the RRD wave twin or now quad, Very small fronts 9cm in fiberglass and toed boxes around 2 degrees.

_________________
K4 fins
4Boards....May the fours be with you

http://www.k4fins.com/fins.html
http://4boards.co.uk/
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U2U2U2



Joined: 06 Jul 2001
Posts: 3049
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sat Nov 10, 2012 12:04 pm    Post subject: Reply with quote



these Witchcraft fins are really cutting edge, light weight, and fronts with toe built in, inside foil shape very sophisticated and they HAVE TWIST.

US box and the side are mini tuttle.

new ones yet to try them out.

_________________
K4 fins
4Boards....May the fours be with you

http://www.k4fins.com/fins.html
http://4boards.co.uk/
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U2U2U2



Joined: 06 Jul 2001
Posts: 3049
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sat Nov 10, 2012 12:05 pm    Post subject: Reply with quote

xander.arch wrote:
I've sailed this combo 80% with a 4.7 which is perfect. I've only tried it once with my 5.3 and it was surf and slog, but the fins felt maybe a bit small for the 5.3. I'm also a bit of a lightweight at 155 lbs.


What year is your Da Curve ?

I sailed the 85L and it was sweet

_________________
K4 fins
4Boards....May the fours be with you

http://www.k4fins.com/fins.html
http://4boards.co.uk/
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