# wings and fin positioning

Hi I was hoping to get some help from someone who can explain how fins (quads) and outline wings work together.

I am going to shape a quad fish - I have a good template that I used before BUT I wanted to put double wings (ala Speedialer) on this one to help pull the tail in.

My question is what is (or should be) the relationship between the Fins and these wings ?

I have looked at pictures of Speedialers and the wing seems to be behind the fin

I measured a Brian Bulkley shortboard quad that I have with double wings, and the wing tends to be in the middle to rear third of the fin

I have the fin positions that I used before and they worked good

Any input or suggestions would be greatly appreciated

Thanks

Jim N

Hey, Jim…I’ve attempted a few of these, studying everything I could find on Sway’s, the web, at the surfshop looking (and measuring) Pavel’s work, etc. Basically, the trailing edge of the rear fin is set at one half the distance of the trailing edge of the front fin. On a 6-0, that would be 11.75" trailing edge front fin & 5.875" trailing edge of rear fin. Pavel emphasizes the need to keep about 1.75" of space between the trailing edge of the front fin and the leading edge of the rear fin for to allow water to flow through the fin array. On a double-bump tail, the peak of the leading bump is even with the trailing edge of the front fin (ya with me?) The front fin has about 1/8" toe and an imaginary line extended along its base intersects the peak of the trailing bump at the rail. The rear fin has 1/16th or no toe-in. An imaginary line extended along its base intersects the tip of the wing. The attached picture was scraped from Pavel’s old “Green Room” site. This site has been upgraded, but on the old site there was a page of photos showing boards (mostly fishes) in various stages of completion. In the original, you can see the actual pencil lines that were used to make the alignments, which I have enhanced for clarity. This article was very helpful http://surfermag.com/features/onlineexclusives/pavelintrvu/index4.html particularly his utilization of the double-to-single “afterburner” concave, which works hand-in-glove with the his Turbo Speed Dialer fin design, and the thinned-out tail, plus tapered stringer for increased tail flex (tail rocker on demand?) A very well-thought out design, indeed, certainly worth emulating.

Try again with the picture…

Here’s the link to the pictures I was talking about http://www.allaboutsurf.com/articles/pavel?pg=7 . It wasn’t the Green Room site after all. This is also a very good article about Pavel.

It makes more sense to me to have a break in the rail line behind the fin than in the middle of it, so that’s where I’ve always put my bumps.

When you put a board on a rail, the fin on that side needs to be fully engaged, with water flowing around both sides of the fin evenly in order to create lift. And in this case, lift pulls the rail downward, into the water (assuming you have a single foiled fin) giving more hold. I believe the degree to which the fin is engaged is determined by the rail line. This means that because a fin’s distance from the rail is measured at the trailing edge, if you put a bump in the middle of the fin, or at the leading edge, there will be too much bottom between the fin and the rail at the fin’s leading edge, and the fin won’t be down in the water as much when turning. This can be a problem, particularly for front-footed surfers, on full rail turns or if there’s a lot of foam/turbulance.

Putting the bump at the trailing edge, right where the bump starts, puts the leading edge of the fin closer to the rail, so the fin’s fully in the water when turning.

In terms of fin position, you can tweak that to your liking. But I think there is should be some consistency with the position of the bumps/wings and the trailing edges of the fins.

I think someone (ACE? Deadshaper? Allan Gibbons?) posted something about fin placement not being set in stone. There are a number of variables that will change the way a board behaves if fin placement from board to board is based solely on identical raw numbers. Tail rocker/tail rocker apex, outline curve and rail foil might make more of a difference as to where fins should be placed and none of those factors are being addressed.

Here’s a speed-dialler quad, and the lobes of the wings are right around the trailing edge of the fins. The wings are more of a by-product of the pressure-reducing scalloping inward curves of the rail line. The bottom’s dead flat with a very little lift out the back.

My take on wings in general is that rocker- specifically the apex and break of the rail rocker- developed and refined and eventually took over the chores that wings used to do. But I tend to think of quads as distinctly different from either thrusters or twins, and they get their own particular rocker, bottom and outline, and fin placement has to take all those things into account.

Quote:
The wings are more of a by-product of the pressure-reducing scalloping inward curves of the rail line.

Allan,

Would you mind extrapolating a little about what you mean here?

What is “pressure-reducing scalloping”?

Thanks,

Ian

Quote:
Quote:
The wings are more of a by-product of the pressure-reducing scalloping inward curves of the rail line.

Allan,

Would you mind extrapolating a little about what you mean here?

What is “pressure-reducing scalloping”?

Thanks,

Ian

Ahh, well, Ian, ya got me there, at least in ‘splainin’ it in words, but I’ll give it a shot:

If you think of the bottom planing surface providing lift (pressure) you might want to bleed off a bit of that to create a little reaction- to loosen it up in a specific way. I like to balance it with the fin set-up and the overall shape and the rider’s desires (“fast and loose”, generally, duh).

Wings are a good way to do that (along with accelerating tail rocker, but that’s a different conversation), but I dislike hard-cornered wings (mostly because they inevitably fracture down the road and around the corners- fiberglass doesn’t seem to like those angle, a swallowtail is bad enough). So doing a nice softly abrubt transition is my way of doing it, and it seems like a “scallop” shape.

Now that I think about it, maybe its also a desire to get away from sharp points of any kind on my boards.

Quote:

Hey, Jim…I’ve attempted a few of these, studying everything I could find on Sway’s, the web, at the surfshop looking (and measuring) Pavel’s work, etc. Basically, the trailing edge of the rear fin is set at one half the distance of the trailing edge of the front fin. On a 6-0, that would be 11.75" trailing edge front fin & 5.875" trailing edge of rear fin. Pavel emphasizes the need to keep about 1.75" of space between the trailing edge of the front fin and the leading edge of the rear fin for to allow water to flow through the fin array. On a double-bump tail, the peak of the leading bump is even with the trailing edge of the front fin (ya with me?) The front fin has about 1/8" toe and an imaginary line extended along its base intersects the peak of the trailing bump at the rail. The rear fin has 1/16th or no toe-in. An imaginary line extended along its base intersects the tip of the wing. The attached picture was scraped from Pavel’s old “Green Room” site. This site has been upgraded, but on the old site there was a page of photos showing boards (mostly fishes) in various stages of completion. In the original, you can see the actual pencil lines that were used to make the alignments, which I have enhanced for clarity. This article was very helpful http://surfermag.com/…elintrvu/index4.html particularly his utilization of the double-to-single “afterburner” concave, which works hand-in-glove with the his Turbo Speed Dialer fin design, and the thinned-out tail, plus tapered stringer for increased tail flex (tail rocker on demand?) A very well-thought out design, indeed, certainly worth emulating.

Hey NoMas … how goes it old mate ??? Hope all is well !!

First of all, many thanx for the comprehensive feed back and links on this thread… lovin it !!!

One thing I would like to know, (if you have the spec’s), how far the fins, (front and rear ) come in off the rails

Take care look forward to hearing from you.

W

Hey, Foamie…things would be better here in So Cal if the East Pac storms would stay north of L.A. where they belong. I think the front fins are set first. This placement determines the location of the front bump, the back bump and the trailing edge of the rear fin (see picture in my thread above). My guess is that the trailing edge of the front fin is placed a common 1.25"-1.5" from the rail. The front bump is at or just behind the trailing edge of the front fin. The location of the wing-pin tip helps to determine the location of the the trailing edge of the rear fin set. Set with zero or near-zero toe and at half the distance of the front fin trailing edge from the tail, the symmetrically foiled rear fins point to the wing-pin tips. This would make sense in that a greater distance between wing-pin tips suggests a wider tail and spreads the rear fins out from the stringer accordingly. In the photo in my thread above, the front fin rear trailing edge is about 1.5" from the rail and the rear fin trailing edge is about 2.75" from the rail. The front fin trailing edge is 11" from the tail, while the rear fin trailing edge is half that or 5.5" from the tail.

On my Pavel, front fin is about 1.25 from rail, and back fin is 1.75 from rail. Measurements are trailing edge of fin to rail.

Back fins are the same distance apart as the tail is wide.

“NoMas Tomas” and “Obproud” … many many thanxxxxxx

Takes all the trial and error / guess work out of a simple mans life

We don’t see any of Pavel’s work over here and it’s hard, (impossible) to gather any intelligence on his work

Happy Dayzzzzzzzzzzzz

Thanks for all help guys that give me plenty to go on, doubt I can match Toby’s or Allans work but hopefully I can make it work

Thanks

Jim N

While we’re talking about the speed dialler,um …

I’ve got the bug now and I’m starting to plan my next project which will be a speed dialler influenced quad,very slightly longer and a bit ‘finer’ than the fish I just made.

So… what about bottom shape ? I’ve tried the archives several times and there’s nothing too definite there- just a few hints really.

While I was away I met a travelling Californian who had a genuine Rainbow SD which I scoped out , naturally , although of course I didn’t have any straight edges or rulers at hand.(I’m turning into such a design geek I should probably take some everywhere heh heh).

But, to my layman’s eye, it had a rolled nose , to single concave, to double inside the single between the fins, starting to flatten off as it exits the tail.Nose rocker looked about normal for a fish, but tail rocker noticeably more, gradually accelerating to the tail.Everything was pretty subtle of course.

Sound about right ?

Thanks in advance Tomas and anyone else.

Hey, fishin’…Next to a bonzer, I think the Pavel SD is one of the most technical shapes to attempt. Rail bumps, quad fins, concaves…there’s a lot going on here. It is the quintessential example of a “retro shape” renewed by contemporary design concepts applied through the hands of a master shaper, in this case Rich Pavel. If nothing else you’ll acquire a keen appreciation for elegance of this well-thought out design. It ain’t just a fish with four sexy fins instead of two.

Like you, I eyeballed several of these before I took planer to foam. Then I went back with tape and straight edge…a couple of times. Remember these are all handmade, so measurements will vary. Even the CNC shapes are “finished” by hand, glassed by hand and fin boxes set by hand, all introducing some variability. So, here’s how I do my interpretation of the Pavel SD:

Thanks for the reply , Tomas.

Good to be reminded of the terms variation and interpretation.

Quite by chance I found some posts by EntropyFletch and obproud just before which also answered my question.

What they described was slightly different from what you’ve said , and different again from the board I saw , but variation , interpretation.All certainly in the same ballpark.

It’s obviously that double to single that’s the secret sauce behind the SD being such a cult classic.

I think I understand it now.

No doubt I’ll fall a bit short in my interpretation, but now I’ve got a much better idea of what I’m aiming for.

All good, thanks again.