single fin love

[PaulJensen]

[BarrySnyder]

Zack, I put my boxes at 4 1/2" from tail. (Vee helps for thickness).

Fin sits at about 5-6".

6 1/2"-7 1/2" Fins.

Watch Rusty’s Single Life video.

They look like all boxes are at 6".

Fins jammed as far back as possible.

I think they turn sharper.

[Huck]

http://store.mollusksurfshop.com/collections/surfboards

Single fin surfing is alive and well in the Santa Monica area - I see a lot of singles out at Malibu when I’m there.  And just recently, looking at the Mollusk surfshop website, I found a lot of interesting looking single fins in the catalog.

[ambrose]

don’t own a multi fin,

made a  multi once

then put it away.

a few years later

I took off the three

put in a single box.

I have a lot of boards.

…ambrose…

singles glide

more.Yup.

[gonesurfn]

The flow and ease are always there,…some of us old guys never left or stayed with other designs only for a short time.
DB singles have never let me down…new 8’ for the winter,…Mahalo Lyle she’s sweet.

Aloha, Randy

[gonesurfn]

'72,… 7’3" ,William Dennis, shaped by “Blinkie”,…wish I still had her.

Aloha, Randy

[zackoopman]

Cheers Barry, I think I have been placing my fins way to forward. Been riding my midlengths at 10inches up on 7’6s on 6ft waves and cant control them. Got another glass on for a customer so wanna get it right. I’ve seen geoff McCoy put his at the 7 mark 

[newschoolblue]

The singles I have ridden, I always ended up pushing the fin all the way back and leaving it there.  Even with my 6’0" in-line single I pushed the front fin all the way back (which put it around 8 or 9 inches fom the tail) and used a regular thruster center fin set at around 3.25" behind it.

 

[thrailkill]

The correct way to descride fin position, is the measurement of the distance from the tail to the BASE LEADING EDGE OF THE FIN.   Think about it, do all fins have the same base length?    No?     Well then, if a fin with a 3 inch base, and a fin with a 6 inch base, were both positioned  6 inches from the tail to the back of the fin, the leading edge of one fin is 9 jnches from the tail while the other is 12 inches from the tail.    Do you think there is a difference in the handling of the boards in question, because of fin position?     Duuuhhh!        I know, I know, ‘‘that’s not what everybody does!’’ you say.      Remember, there was once a widespread belief that the earth was flat.      Consensis does not make a thing so.   Now you know something that 99,9% of surfers and board builders don’t know.

[Huck]

@$1

The correct way to descride fin position, is the measurement of the distance from the tail to the BASE LEADING EDGE OF THE FIN…

Sorry, but this is too logical.

[stoneburner]

@$1

If the fin is glass-on, the base is aligned with the mid-line of the board, and then moved fore/aft, until approx. 25% +/- extends beyond the rail line. If a box fin, you align the base that is above the box, with the center line of the board. With a box fin, after the position is determined, set the box so that fin, in the chosen position, is in the center of the box. This will allow max adjustment fore/aft, to fine tune the board to you taste, feel, style. Once I adopted this method of fin placement, I NEVER had to deal with spinouts again. That was 1960. Does this help? 

@$1

Aloha MaraboutSlim, Jim, Bill and others.

The use of the rear of the fin as the zero point for fin measurements happened long before I was able to influence anything in surfboards.

While I understand why other locations seem to make more “design” sense I personally don’t think of the singular rear point of the fin location, as anything more than just a reference point.

Just like we use the center tangent point in the bottom rocker to reference rockers from. There are other ways to measure and duplicate rockers but none simpler or easier to reference from and communicate with others as a standard.

The Rear of the fin as the reference point is fine with me.

Here is why.

1. The gap from rear to rear is easily the most simple to view and grasp.

2. It is the existing standard

3. For multi fins the distance the fin is from the outline matters and since the toe in angle pivots from the rear of the fin it is convenient to use the rear of the fin for both toe in, outline distance… and since we are there already, the distance up from the tail at this point just comes along with it.

I agree that the back of the fin’s connection to the overall design of the fin or performance of the board is not specifically relevant to anything. On the other hand, I don’t think any other point on the fin, like the “leading edge from tail” or the “tip of the fin from the tail” has anymore relevance. Here is why…

In sailing yacht design there is a thing called “Center of Lateral Resistance”. A simple but not perfectly accurate way to visualize and feel this is to take the profile of a large sailboat viewed from the side and shrunken down to a much smaller scale, say 12". Cut out a firm plastic template of everything from the water line down.

Sink this under water. Put your finger somewhere near the center and push it forward under water moving your finger around till you can get the template to balance perfectly on the end of your finger while moving forward.

This point where your finger is, is the “Center of Lateral Resistance”. In yacht design you have to design the mast and sails and locate their “Center of Effort” to work in harmony with the hulls “Center of Lateral Resistance”.

Too keep it simple for a start lets look at a single fin. It also has a center of lateral resistance and it can be determined via the same process described above. It is this center of lateral resistance that one is feeling when one changes to different fins on the same board.

Add a bit more tip to the template and the CLR changes toward the back of the fin. Narrow the tip and the CLR changes down toward the base. Etc, etc.

When the fin is placed on a board and the board is tilted up on its edge in a turn a certain amount of the bottom of the board is being pushed sideways through the water. This part of the board also has a CLR. More rocker in the tail moves the CLR forward. Concave tails move it back. Narrower tails move it forward, etc, etc.

Combining the fin and the boards wetted surface in a turn, creates a composite CLR that is able to resist the sideways drift of the board and if done well, redirect those forces such that they aren’t wasted sliding sideways, but rather generate forward energy and thrust.

The point on the fin template that one uses to measure the placement of the fins is pretty much meaningless for design reference. If all fin templates had a dot where the CLR was, that would make a good point of reference that would connect to something “design” related. But as long as you know your fins and how they work it is no problem to use the front, rear or tip as a point of reference for where to locate them on the board. Say a fin has a 6" base and you put the fin 6" up. Fine… use the front of the fin and put it up 12". It is just a point in space that doesn’t signal any particular design or performance issues.

Now lets talk briefly about Multi Fins. Some points to consider.

Each fin has a CLR.

The whole group of fins has a CLR. Move the group closer together and the CLR will get taller and more oval. Move them farther apart and the CLR will get more elongated and wider. Move the whole group forward and the CLR moves forward. Move them back and the CLR moves back. Tilt the fins over more and the CLR moves down toward the base more. Straighten them up or hook them in at the tip and the CLR moves up the fin. Change foils and even more variables jump into the mix! Go slow, go fast and it all changes again.

Continuing with the Sailboat analogy, the surfer is kind of like the Mast and Sails. He can move his CE (center of effort) forward or back, sideways and angle the board more or less. All will work good or bad in conjunction with the boards CLR. If the surfer is like the Ho brothers who surf off the tail they will need something a little different than someone like Shaun Tomson who surfed much more off the center of the board. Good shapers know this stuff and have the ability to shape it as planned.

Neither is good or bad, all is good as long as everything is in balance and harmony. As long as your measurement system is easy to use, allows you to quantify the necessary details and universally communicable, the measurement system will be fine.

What one does with all those measurements is the real issue that matters. Most don’t collect the measurements because they don’t know what to do with them nor are they skillful enough to replicate them or make the small specific changes needed while keeping other parameters the same. Shaping machines have done wonders in advancing this as it has removed much of the necessity in having the actual hand skills to do the job. The downside is that it has opened up the same benefits to those making boards in foreign countries where it is much more advantageous to locate the other aspects of surfboard construction. And while everyone’s job got easier here, it handed over the ability to shape good boards to those who will now take the jobs of those who’s jobs got easier.

In the end, unless you know your fin templates well from actual experience, no point of reference is really any better then another.

 

[sharkcountry]

I like to use a visual check first. Hold the fin on the board and see how it looks. If it’s too far back or too far forward I’ll know. That’s the starting point. Then I place the box so the fin is as far back as I want it leaving room to move it forward.

You need to be sure about the fins cause some have the screw in the back and some have it in the front. If it is in the back, the box will need to be further back than if the screw is in the front, so you should check the fins you might want to use to make sure you leave some wiggle room.

Also, I like 9" fins, but I also have a couple of 7.5" fins. They sit in the box in different spots, so you need to add that to the equation.

Back in the day, when all boards were single fins, we only had the fin size and position to plat with to loosen or stiffen up a board. Most of the time we only had one fin, typically a Brewer style fin, and moving it back or forward was all we could do. Bigger day, move the fin back, smaller day move it up.

[drzoidberg]

Here’s the board I’m considering converting to a single. It’s 6’4" and about 22" wide and probably 2.75 to 3" thick, never really measured it precisely. I believe it’s about 15" nose and tail too. Bottom is flat all the way through. But I can’t see why it needs to be a thruster, it’s not like I’m pumping it hpsb style or looking to make my own speed. I’m a small person, and this thing cruises for me. Might as well use less fins and cruise more. What do you people think? I’ve never owned or ridden a single before (Product of this generation) and I want to try one.

[thrailkill]

Are the existing fins glass-ons, or box?      A fin 7.5 to 8.0 inches deep will be plenty of fin for that board.    Put in an FU box, and set the leading edge of your fin at 11 inches up from the tail as your starting point.    You’ll be ‘‘in the ballpark.’’      You may want to adjust the fin 1/2 inch or 1 inch in either direction to get the best feel for you.  The shape is well suited for a single fin.

[drzoidberg]

Futures boxes, looks to be a standard thruster arrangement. I’m gonna see what greenlight can do, because I’m router-less, nor am I master of the router. Any fin suggestions? I’m clueless about this stuff.  But I was gonna try the standard, dolhpin looing fin like this

[thrailkill]

@$1

Futures boxes, looks to be a standard thruster arrangement. I’m gonna see what greenlight can do, because I’m router-less, nor am I master of the router. Any fin suggestions? I’m clueless about this stuff.  But I was gonna try the standard, dolhpin looing fin like this

The subject fin appears to be an 8 or 9 inch Greenough fin.     Don’t go more than 8 inches deep.     A flex fin would not be my first choice.

[sharkcountry]

Greenough 4A, my favorite single. I use the 9" in boards from 6’ to 8’. For boards with narrower tails, I have a 7.5" version.

[drzoidberg]

Oh yeah I just grabbed that image, definitely not using a huge fin. That’s a greenough 4a though. Which seems to be a decent starting point. I’m gonna do some reading and such to see what’s out there.

[beerfan]

I used to like dolphin find, but now really like the greenough 4a style flex. I have a 9" and a hand made 7 1/2"er. I like the 7 1/2 even in my 9’ longboard, way back in the box. Enough drive, and plenty loose. Still haven’t tried it in my 6’6" egg, which I got it for, but it’s winter here and I’m way out of fitness. Might throw the egg in the car tomorrow anyway. 

Absolutely do it mate, I think you will really like it. Just go with the flow!

[oneula]

been tripping on greg wild’s inline single 

in his honor thinking of trying something like this on a firewire

with and without the sides