Fin Placement and symmetry

Hey Lads :slight_smile:


My first post here on Swaylocks!


Ok, so I’ve been searching a bit and havent found what im looking for in the archives, but I believe it has been done in the past, and certainly someone as some insight on this.I’ve recently build 4 boards, and the last one was a twinny with a stabelizer, I’ve never had ridden a twinny before, and realized how we turn the surfboard, and how the Fin is a pivot point.

So why do we always make the fins closer to the rails on wider tail boards? Doesn’t it stiffen up the board? makes it harder to turn? What does happen if we put the fins 5.5 inches from the stringer on a wide tail board? Also, im also thinking of asymetric fin placement based on stringer distance and your foot size, like placing the frontside fin 5.5 inches from stringer and the backside fin 5inches from stringer as an example to make it easier to turn on the backside, this as a twin fin arround 10" off tail both of them or something along those lines depending on the design.

Does anyone have experimented any of these things? Im really curious, I was gonna build a surfboard with some asym fin postion and weird fin placement, but came here first just to hear some opinions :slight_smile:

Sorry If I am wrong about anything, I am new at this and I’ve built only 4 boards, also English is not my main language.

Fin placement is based on what others have found to work.

Try something different and see what happens, you may be pleasently surprised to find something that works for you. I’ve been putting fins in different places and with different tow and cant with mixed results. There are a lot of people using asymetric fin placement, I don’t. I do use boxes that allow for 1/2" of travel, so I could have them almost an inch off, but I just haven’t bothered trying that. My last board has a wide round tail with twin long boxes about 2" in from the rail. I think I could have been up to 3", but I won’t know if that is better until I try. My current build has Neil Purchase Jrs Duo setup plus a thruster setup.

I will! :slight_smile:


What did you experience moving the fin 2" inches off rail on your build?

Yes I’ve checked that fin setup before I posted this, and even watched the video of Neil Purchase Jrs Duo, how does the fin setup feel on your build in your opinion?

I wasn’t conviced by that fin setup, I thought it was too centered, rather space them an inch more and put some twin fins, that’s what I would do, but I haven’t tried anything similar, so… I might be wrong… 

With the twin boxes placed 2" in there isn’t much difference. I think placing the fins further from the rail helps stiffen the board more, so the further in you go the more it will feel like a single fin.

The duo is like riding a single fin, but the tail can be much wider. I’ve made 2 of them and I like them. The board I’m working on now has a different rocker than the other duos, and it could have been setup as a tri or quad, but I decided to do a duo and tri instead. In the past, I’d add fin boxes after I’ve used the board for a while and usually to add fins along the rail for added drive. I decided to put FCS Fusion boxes in this time, so I did it before the lamination.

My brother has 2 asym boards with fins that are not lined up and off center, we found that it seemed like the board moved through the water faster. Something about the way the distrubed water wasn’t hitting the rear fin the same way it does in a thruster. I also have made several boards using Bill Thrailkill’s double single fin.


If you really want to test your ideas , buy some cheap glass on fins and hot glue them wherever you want them , test , if you are not happy just cut them off and reglue them to your next favorite location   , test , repeat .

Is hot glue strong enough? In the past people would just glass fins on and grind them off if they wanted to change the location. In the 70s, we used the stick on small tri-fins and the double sided tape it came with never held them in strong enough.

I like using Proboxes because I get about a 1/2" fore-aft movement and I also get cant changes. Moving one side bite up all the way and the other all the way back would be about a 1 inch difference.

That’s a really nice ideia, im so used to router fin boxes that this haven’t even crossed my mind!

I wonder how does it hold tho for a couple sessions before i glass them on the permanent position…

I used those cheap plastic fins that you can buy from Fibre glass Hawaii , about $16 for a thruster set , cut off the fcs tabs and hot glue to the board , worked for me .

I use those too, but I use them in FCS compatible boxes. In some boards they feel a little too flexy, but in other boards, I really like them. I use the Stretch quad set a lot.