grom fish fin placement

allright so i shaped a grom fish 4 all the little aspiring kelly slaters at my home break the sebastian inlet fla…

it’s a 4’4 x 18 1/4" x 2" swallow tail fish… the spread on the swallow tail is 6in… it all looks really groovie but i have little to know idea about fin placement on such a small board.

any ideas would be great…

Good question. For my small boards, I start the rear center fin at 3.5" from the tail and the two side fins at 10.75 inches from the tail. (I mean the rear of the FCS template.) You will have to adjust for the rocker and base size of the fin.


sorry i may be misunderstanding you… your measuring from the tail end of the board to the back end of the fins correct. i only say this because i use future boxes not fcs so im a little lost in translation…


a pic of the board would be a great help

more detail



Is this a twin, 4-fin, or 3-fin fish?

i was thinking a twin or a thruster i was thinking if i make it a twin i will just use the front fins for a thruster board my size

heres the only picture i have

Hi Willionarie,

If you go to the FCS website (, you can click on “knowledge” and then on “fin characteristics” in order to have a clue about what how fins work.

I’m glad you posted the pic. That’s not really what I’d call a ‘‘fish’’, closer to a late '70s twin (or even

single) than anything else. You might want to move the fins up a little compared to a fish placement.

Got to get a little space between those fins. If you go 10’’ up and 1 1/8’’ off the rail. what distance does

that yield between the rear fin marks?

The fins really should be back about 8 1/2’‘-9’', but on that tail they’d be very close together.

ok so heres the deal if the fins are 10in up and 1 1/8" in from the rail (as you said) the distance between the rear fin marks is 9 1/2"… dose that sound groovie? this may help 2 the width at 10 in up is 12 in and the distance @ 1ft from the tail the with is 12 3/4in. also do you think i should put a box in for a trailer fin to make it a thruster…and if so how far from the tail should i make it?

oh and on i side note it is like a retro twin fin thats what i figured the groms needed, some soul in their surfing…

thanks for all your help,


Yeah, that sounds OK. I’d throw in the third box too, why not? Makes the toy more versatile.

Do some little trailer fins for the twin-with-a-stabilizer setup and have fun!

I am measuring from the tail of the board to the tail end of the FCS tracing templet which is just about the end of the fin.