Fin size for twin

[HaoleKook]

I typically surf 16 to 16.3 sq-in thruster fins (big end of large size fins) and am wondering what size fins to try for a new twin + 1 board. Should I just match the area of 2 thruster fins to the center and one side fin, or does the size not translate like that with twins?

[Geezer]

What kind/size/shape is the board and how big are you?

[HaoleKook]

I guess that kind of info would have helped :/

It’s a 6’10 x 22.5 x 3 "mid length fish" with swallow tail and flattish rocker, but with a little kick in the nose. It will be Twin + 1 fin setup.

I’m 190lbs. So far I’ve surfed 8’6 to 7’6 fun boards and like 16 sq-in thruster fins.

Twin fins seem to range from 18 to 23 sq-in. for upright fins and a little bigger for keels.

I just found a review by a 200 lb guy surfing a 6’4 hybrid twin, saying the Britt Merrick fins are pretty great. I guess they’re a hybrid/modified keel but don’t feel tracky. 23.5 sq-in. There are many good reviews about this fin but good to find someone my size on a bigger board using them.

https://cisurfboards.com/products/britt ... tyiW3IHDPX

[Geezer]

Ok…i I am about your size, a little bigger actually at 210lbs. I have a boy that sounds similar to what you have in a Mark Richards flying fish 7 foot with pin boxes for a 2+ one setup. I forget the rest of the dimensions but it’s something like 21 1/2 x 2 3/4.. anyway, it’s a wing swallow so the tail is a bit pulled in. Fittingly I run Mark Richards, MR Twin Fin’s in that board. I’m not the one to give a detailed review of performance as I’m just bang on average put the fence don’t get in the way, board is pretty quick, hold in the bottom, turn on the backside, and I’ve never had the urge to change them after putting them in. It’s one of my favorite boards.

I have a 6’ 5” CI Twin Pin that I run the Britt Merrick fins in. Those are not 2+1 - just two big modern keels. I use them also in a 6’9” channel bottom pintail twin at 42L that is modeled after the morning of the Earth Twin fin Fiji. I use both of those boards in bigger more hollow surf than I do the Mark Richards; the britts seem to do well with those two boards in those conditions. The two boards are about the same volume have more ricker and nose/tail more pulled in than the MR. Tried the Twin pin with those fins in smaller waves and the board was tracking. This fins come in pairs and like I said they’re pretty big, they were too much fin for me when I combined them with the trailer just playing around, turned the board into a clunker



I have a 2+1 Futures T1 twin set as pretty much the same but with futures tab as the MRs. Can’t go wrong with either one. One of the 2+ one said that I’ve heard about, but haven’t tried for the bigger surfer. Are the larger size Asher Pacey, 2+1 twins. Bigger members of a Twin Fin fan page on Facebook that I belong to rave about them.

Is a general rule of thumb for me I’ll go with a bigger fin the wider to the tail is. You’re big, but you’re not that big if you know what I mean. Even in my size I’ll ride mediums in a thruster pin tail sometimes. Part of the fun of Twin Fin’s is the looseness of the ride. For advice from one big guy to another. I’d say go with the MR 2+1 or the Futures T1 2+1, they are either/or, then ride them first as a 2+1 like you wanted to do then pull out the trailer and ride it like that and see how it goes.

[Geezer]

Last thing, box placement matters. Trying to turn a 2+1 or thruster designed board into a twin just by putting in two fins doesn’t usually work great. Forward fin boxes are too far forward among other things and drive is lost.

Ride the board like the designer imagined first is my suggestion. Then try whatever you want to after experiencing that.

[HaoleKook]

That was super helpful, thank you so much! Yeah I can ride smaller fins on my pintail, too. The 16+ thruster fins just let me set a rail and hold the line in the biggest waves that I typically surf. It's good to know that something like the MR or T1 with the trailer has enough hold. I will probably try something like that at first since it's a twin and also a smaller board than what I'm used to.

This is a custom board and it's being made as a twin + 1. I attached some reference pics. It looks similar to the Flying Fish. I don't know if mine will have the channel, I kind of doubt it but will let the shaper decide.

[Geezer]

Since you’re working together with the shaper, you should ask him what he recommends.