I want to fit thruster fins to my 85lt Fanatic Freewave. Though I have the fin spec's, I don't know where to put them. Can anybody give me the position dimensions relative to the central fin box?

just buy the new one, they go off !!

If you get no better advice try :

For the distance from the tail put the back of the front fin boxes level with the front of the centre box, or slightly overlapping

For offset from the centre as far out on the rail as you can get them without the box sticking through the deck, or the fin tip being outside of the rail. The fin should be 100% under the board, which is usually the deciding factor. Depends what size fins you plan on using.

For angle / toe-in then parallel to centre box / stringer, or toed in very slightly (front no more than 5mm closer to centre of board over the length of an 8" US box)

For vertiacality - then vertical to slightly toed out - tip closer to the rail than the box - but not so the fin tip moves outside of the rail (fin to be fully underneath the board still)

- once you have that the centre of the area of the three fins should also be just about centred under the back footstrap


In the past when I have done the same I sort of err of the side of caution and go :

8" US boxes so there is plenty of tuning available
lap the back of the front boxes slightly over the front of the centre box, you can always push the fins forward in an 8" box, but can't push them back beyond the end of the box
mark the cut out and try set the boxes with about 2mm of toe-in, so atleast if I mess up they are toed in or parallel, not toed out excessively
rake the boxes so they are about 3mm further apart when ,measeured fin tip to fin tip than the same dimension on the boxes, so again if I mess up they are raked out of vertical, not raked in.
Make sure at least a 24cm fin stays atleast 10mm inside the rail, so when I put an 18cm or 15cm fin on, it is definitely inside the rail


But - I have never really experimented with anything different, this is what I assume everyone else does (and where surfbaords used to be). It has never resulted in a board worse than before (other than my poor quality workmanship), but I am sure there is a first for everything.

Sorry - if you meant the boxes are already there and you just want to put some fins in them then - put the fins anywhere in the boxes.

Closer to the back fin looser, further away more directional.

The middle is always a good guess.

Try also a true thruster, instead of big rear, smaller fronts. Maybe 3 x 15cm / 16cm in an 85ltr ?

K4s are cheap and just as good as G10 in that size

Thanks so much for all that info. you've obviously been there before. Hav'nt installed the forward boxes yet. Fanatic specify 6" but your idea of 8" boxes to allow for adjustment sounds good to me. Love to buy the new board but the rule in my house is "Can't have a new one till you break your old one". But I guess thats why trees have forks. Cheers!

Do the little side fins make all that much difference?

Supposed to be better for onshore conditions? Speed?

I did it. Have a look in my profile for pics. It was a great project but the issue was matching strength of carbon. Couldn't believe how little carbon was in the Jp and I used higher grade mat. Did eventually get a crack where there was some flex. Made it looser but heavier and tail heavy compared to the quad that I moved onto. I got some great help off crew on SB.

If you want any details PM me. Good luck.

On an hourly rate a second hand quad does make sense

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K Dog said...
Do the little side fins make all that much difference?

Supposed to be better for onshore conditions? Speed?

only good if they are in the right spot

I one who think this thruster setup needs a thruster shapes. I could be wrong.

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h20 said...
I did it. Have a look in my profile for pics. It was a great project but the issue was matching strength of carbon. Couldn't believe how little carbon was in the Jp and I used higher grade mat. Did eventually get a crack where there was some flex. Made it looser but heavier and tail heavy compared to the quad that I moved onto. I got some great help off crew on SB.

If you want any details PM me. Good luck.

On an hourly rate a second hand quad does make sense

The dedicated wave board is seeming like a good idea, rather than potentially screwing up a perfectly good freewave board.