Quad set-up logic

General Discussion
1

As a complete novice about quads, I’d like to ask a question to Swaylock’s fin gurus or whoever with enough experience in this field.

I have noticed that the fins with the more rake went in front and those that are more “vertical” in the back. I would naïvely think that the opposite (rake in the back and “vertical” in front) would mean manoeuverability under the back foot where it belongs, while having drive from the tail?

Can someone explain? Did anyone try it the other way? If so, what were the results? Thanks, guys.

2

good question , billy !

I look forward to reading people’s findings …

cheers

ben

3

Pavel started the recent trend. There is an article floating around somewhere that explains he took a keel fin, and basically cut it in two, so that the front fin had a reasonable normal “dolphin” shape, the leftover is the upright trailer, this configuration is variously called speeddialers or canard quads.

from the interview

PAVEL: So I did something really simple, I just took that Fish-fin concept and started plotting around the cord length, the cord length just being defined as the distance between the leading and the trailing edge and I would divide it in half, I would change the ratio up, I would shift it back and shift it forward. And in doing that, just take this one low-aspect ratio fin and come up with two high-aspect ratio fins in place of it. So you went from having a two-fin keel to having really in some respects the same fin but just set up in this different way. And then all of a sudden, you haven’t really changed the concept, all you’ve done is you’ve made high-aspect ratio fins out of what was a low-aspect ratio fin.

SURFERMAG.COM: Can you talk a little bit about the placement of the fins?

RICH PAVEL: In doing that you would leave the trailer-fin the very same place that the Fish-fin goes. The back fin just sits in the very same place. And then you move this one [the other high-aspect ratio fin] out toward the rail. And you put a little breathing room there. And in some ways, that whole thinking was influenced by the Campbells, you know, you need a certain amount of breathing room between the fins. Very, very simple. It’s in fact so simple, it’s like, how come nobody thought of that before? And you don’t really think you thought up anything, you feel like you discovered something, like it was revealed to you. You hear people talk about intuiting stuff in and out of the universe, it’s probably one of those, you just channeled it. Bling, it just came to you.

http://surfermag.com/features/onlineexclusives/pavelintrvu/index4.html

4

thanks for that article , Dave !

…interesting …

So, the question [I previously asked in other “quad” threads ] remains… [for me at least …]

the advantages of the canard are … ?

versus

having a more raky / ‘conventional’ back fin ?

… Having ridden both [and a few other setups besides] , I am still unsure / not fully sold , one way or the other , so I meanwhile will [try to] enjoy riding both kinds of setups from time to time …roll on , winter waves !

of course , I also realise that what suits someone’s waves and style, may not be the same for someone somewhere else .

(…THAT is the beauty of experimentation , though , of course !)

cheers !

ben
5

Yeah, Blakestah, thanks for posting that.

OK, that’s Rich PAVEL’s explanation of what he did, but, with due respect to Mr PAVEL, it doesn’t explain much. He started with a big keel fish fin and basically cut it in half, then moved the back half to the rail some. I do understand that. What I don’t understand, however, is the “WHY”.

I’d like to know what you, Blakestah, think about it, for instance. Have you tried a different set-up and what were the results?

Am I right to say that drive belongs to the tail and manoeuverability to the back foot area? Doesn’t it make sense to have more rake far back and less rake in front? What about a quad (or thruster) set-up with lots of drive (surface, rake, base length…) in the rear fin(s) and lots of looseness (finger-type fins for instance) in front?

6

I’ve been meditating alot about the bonzer lately (my next project) and I think the bonzer 5 fin is kind of the same concept as the speed dialer, where they took the single, long runner and split it into two, the total fin area being about equal. I’ve never found an explanation of why, but here’s my guess-

Having the same fin area means having about the same “holding” power. By splitting it into two you allow the fins to pivot in a smaller arc without cavitating. Everyone says the bonzer5 is looser that the 3 fin version and yet I’ve never heard anyone complain about spinning out. I would imagine you would lose a bit of drive though. Someone with experience on both boards would have to bear this out.

I’m no expert. This is an idea.

7

I think your idea has merit. I’ve not ridden the boards you cite, but your logic is sound.

8

Hey Balsa,

Plusoneshaper had his own explination. I’ll paste it below.

I do think that experimenting with your question is very valid.

I’d like to try it myself.

From George:

Note two things:

The rear fins have no curved rake, just a little straight rake. Since this keeps them from twisting

at the tip, the rear fins maintain a more constant Angle-of-Attack, and release when pushed at

lower speeds in disturbed flow (as with a lip hit). This fixed the releasing problem and made

the board quite loose in this kind of situation. During sustained turns the four fins hold really

well, I almost think the rears hold better than the fronts (at higher speeds and less direction change).

The rear fins are moved in from the rail quite a bit compared to the fronts. On the earlier versions

I had them all the same distance in from the rail. A wierd thing was happenning as the waves got

bigger. During those long, sustained turns, both shore-side fins would emerge from the water at

nearly the same time causing a very noticible wobble. At times I had to check my turn and re-set.

With the rears further off the rail, the fins release more sequentially, like a thruster but the quad

fins seem to fight one-another a lot less.

Overall, there is definitely more speed and sprinting acceleration which is great to cover distances.

The looseness off-the-top is much better, which in the past kept me away from the concept.

I even think it paddles with a little less resistance.

Hope this helps,

George

9

Hi Balsa,

Quote:

He started with a big keel fish fin and basically cut it in half, then moved the back half to the rail some.

I could be wrong here but I also think he toed-in the front fins as well in addition to splitting them. I think that this would alleviate the tracking that occurs with huge keel fins. The theory that I always thought was the reason behind the splitting of the keels was to increase turnability with the split and toed-in front fins yet keeping the drive of a large base fin.

I’m no expert though. Halcyon? Blakestah? any thoughts?

Cheers,

Rio

10

“What about a quad (or thruster) set-up with lots of drive (surface, rake, base length…) in the rear fin(s) and lots of looseness (finger-type fins for instance) in front?”

…" paging Herb Spitzer " …

11

I set up a 6’3" quad last winter. It was about 16" nose, 21 1/2" with a 15 1/2" tail, and 2 5/8’ thick.

The board had a single concave out to a little bit of V in the tail. I tried a couple of things with the fins including adding a middle fin to ride as a thruster.

The board was set up with FCS G5000 in the front with the little sidebite back fins. When I tried the GAM (front) with a lot more rake, the board had even more drive but didn’t pivit at all. On this board in particular I felt like I was really surfing on the fins, riding really high on the wave riding faster than any other board I’ve owned. The raked out fins were to much to ride as a quad. They were great when I added the middle fin as a thruster (as they were designed to be ridden). And they worked well as Twin fins in the back slots in smaller waves. To me it seems that you don’t really need too much rake in either fin for the quad.

12

Jeez…talk about "intuiting stuff in and out of the universe "…this morning I put in the fins on da new Pavel quad, and stood for about 10 minutes at the nose, spacing out on the why of the fin placement. Checking out the other quads at Mollusk (S.F.) earlier, lots of shapers have their own ideas (of course) on placement/size/shape,etc. No easy task ,I know, but are there some generalizations one can make on quad fin placement/size/shape ???

13
Quote:

I’m no expert though. Halcyon? Blakestah? any thoughts?

I am not “one” with the quad…and lack enough time on them to even comment on the subtle differences that occur as fins are moved fore-aft, in toe-in, and in cant relative to each other. There are others reading this who have tried dozens of configurations and should comment.