Just finished shaping a 6’6" high volume “big guy” short board for east coast swells and i cant make my mind up where to place fins…i am new here and tried to search achives cuz sure there is something on this and found couple articles… but just not real sure where to put them… i have done 5 fin w/ quad being the predominate set up on last several boards but i want this 5 fin set up to favor thruster set up… w/ option of quad on slower mushy days…i have been placing the front fins up at like 12" from tail and it seams that that may be to far forward??? new at this so not real sure??? I have another short board Firewire spitfire that has fins placed at 3 3/4" center and 11" side front fins…
i read in other thread that for THRUSTER you want 3.5 to center fin and 10.5 to side fins, 1 1/4" from rail w/ 1/4" toe in…
*also for small swells if i move the CLUSTER up a half inch or so would the board come around better… or would it loose to much drive then…??? needs to react quick in small face waves…most swell we get it is 2-4’ on average… beach breaks
*i have futures fin boxes to work w/…
*also i have been using 1/8" TOE IN thinking this would make boards faster in small surf but was wondering if 1/4" toe would make board turn easier? but dont want that “bogged out” “draggy” feeling of a slow board either…mushy surf most of time…
***THANKS FOR INPUT, KINDA STUCK BEING A NEWER BUILDER…
Hey Major. The last 2 Roberts boards I’ve had, a White Diamond and a White Dump Truck had the following thruster set up. Fronts are 11" from tail toed in 1/4" and 1-1/4" from the rail, the center is 3-3/8". Both are high volume wide tailed boards, you can adjust with different fins if it’s too loose or too tracky. I’ve used similar nubers on some of my boards and it works well for me.
states that for a 6’6" board front fins should be at 11 15/16 up from tail and center fin 3 7/16 …
from the looks of his charts as board length goes up the fins progressively move forward up the board to compensate for overall length… so for example, a 6’3" he has 11 1/16 front fins and 3 3/8 center fin.
Not sure if i should stick w/ 1/8 toe in or go up to 1/4? any thoughts on the increased drag this would cause?
The rule of thumb for thruster layout has been pretty consistent for years as stated in posts below.
"Not sure if i should stick w/ 1/8 toe in or go up to 1/4? any thoughts on the increased drag this would cause?"
You'll maybe notice a bit of additional drag with the increasedtoe-inspecs but subtle things like fatter/blunter leading edges or an '80/20' foil can make up for it. The more you drift away from parallel, the more you will dragging the fins sideways when on the flats and in trim.
“a 6’2” tri-fin has fronts at 11" and rears at 3 1/4". A lot of designers
go half the distance on a quad, so that would put the rears at 5 1/2"
and the same distance from the rail, about 1 1/8". In my humble opinion,
I feel this is a little on the neutral side. I split the difference on
distance from the tail (tri vs. quad: 2 1/4"), which would be 3 1/4"
plus 1 1/8"…or 4 3/8". Easier math: 7’ board. Fins at 12" and 4" on a
tri. Half the distance is 6". Split the difference, 5" for a quad. On
average, I try to keep my rears about 2" in from the rail. That’s a
generalization. It becomes a more complicated depending on tail width
and board length."
I had my latest tri/quad made with FCS Fusion boxes, like the ability to adjust the fins around, look for that sweet spot with the fins being used. this one is 7’6, fins at 12 and 4. Really like this ride. The shaper used to shape for Rusty, pretty much follows his fin set-up on quads…surf walled up waves mostly, so tend to leave it as a quad, put a Nubster in the back box if waves aren’t so haul ass…
Sorry - I meant posts above. The basic 11"/3" / 1 1/4" off the rail / 1/4" toe-in. (All +/- a bit to suit tastes - the previous posts, including your own, were close enough)
Bear in mind that any numbers may not apply from board to board unless ALL else is equal. A bit of change in tail rocker, outline, foil and/or fin size/shape/flex can easily offset any specific changes in fin placement and layout. My experience tells me that the rear fin size and placement is most critical. I've made several boards for myself with glassed on sidebites and a small F/U (Bahne) type center box. The center box gives me more fore/aft adjustment than any of the plug type boxes.
What was the main effect of moving the center fin forward or back? And how sensitive is it? say if i move center fin 1/4" will that be huge change or minor? and does moving fin forward make board turn quicker?
Good info on quad placement math… Also never eard of FCS fusion boxes can you adjust them after they are glassed in? and whats adjustable? cant and frotn to back ?
Hi - Moving the center fin forward tends to loosen the board up. Switching to a smaller center fin will do the same. Moving a smaller center fin up in the box until you start having spin out/control issues is a good way to explore the limits. A larger center fin all the way back in the box will increase the size range of the board considerably. With stationary sidebites, a center box and 2 center fins - one about 4" and one about 6" you can cover a good range of wave size with a single board.
Gotcha that makes sense. I am thinking about doing at or close to 12" maybe 11 7/8 to front fins 1 1/2" off rails w/ 1/8 toe in and back fins at 6" 1 1/4" off rail w/ 1/16" toe in and the center fin 3.5" up … debating on moving center to 4" to make for a tighter fin cluster and arch…but dont want to spin out in hard cut backs … the tail on the this board is 17" at 1’ so its wider than a standard short board but im 6’3" and 220 lbs. built board earlier this year w/ 17" tail and loved the lift of wide tail…
FCS Fusion plugs have slightly elongated fin slots, offers a bit of front to back adjustment for fin placement. Smaller waves, condense the quad set-up by moving front fins back and rear fins forward for shorter arcs…bigger waves, open the spread for longer arcs.
Sum adjustment for front and rear combined is about 3/8", which is enough to make a noticeable difference.
I’ve found that setting the rear fins of the quad further in from the rail will give you a thruster like feel, but some of the advantages of the quad. Stiffer, but it will also run through turns better and not bog at the end. With the rear fins closer to the rail like 1" you get a looser board, but it can get squirrely if you crank a really hard turn.
I have a couple of quads with the rear fins centered between the rail and stringer and without toe or cant. Others have a slight bit of toe and adjustible cant (pro-boxes). I like the way this setup feels… very solid in overhead waves. You won’t need the single center box with this setup. Most of my boards have 1/8" or 3/16" toe in the front, and 1/8" to none in the back.
As general rule, I start with the guides on Robin Mair’s website. I use his quad layout for boards that I use his hammer fins in.
I also use the fin placement from my Griffin 5-fin boards for the distance between front and back fins on my shorter but wider tailed boards. It’s more like McKee, and Rusty, and I use more conventional fins with this setup. Griffin has all 3 rear fins in line and I really like those boards.
FYI… the probox has a lot of adjustment for both forward-backward movement and cant angle. You can get so much variety from that system. They can use FCS fins, but there’s also an assortment of probox fins that are very different from anything you’ll see from FCS or Futures.
The board in the photo is 6-6 and the front edge of the front fin is set to 16" from the tail. I have at least 1/2" of play if I move the front’s all the way up and the backs all the way back.
Good deal thanks for all this info and measurement!! So many varieables… i have been using futures for past couple years but those proboxes sound great w/ all the adjustablity… i think thats what i will use next time so a can get the “feel” for fin placement better…
Futures FCS fusion are good once you have it all figured out and don’t want to play with different setups. They go under the lam, so they are pretty solid in your board. I don’t have any boards with futures, so probox is good for me. I still use the older FCS plugs if I’m lazy. On quads it’s good to have the flexibility that probox gives you, and the wide range of fins you can use.
The setup in the photo with the long box does it all. I don’t like to use the FCS adapter so I made a couple of smaller fins to fit into the box to ride it as a thruster. I use the left over cloth from laminating boards to make the fin sheets. I try to make the initial sheet as close to the size fin I want, starting with maybe 10 layers, and squashing that down with a lot of weight. Then I can make the following layers smaller since they will be foiled. Less waste and less work sanding.
thats a great set up w/ option to adjust, expecially while dailing in a particular shape/board design…definately an advantage. On making your own fins you use a grinder to foil the fins once cut out? And how do you know how much foil etc to use? I understand rake, fin base, fin height and flex but the foil ? I know it has lifting effect … but how does that effect ride w/ thicker foil vs thiner foil or more thickness forward vs in mid templet?
THANKS! Im going to look into the pro box on next build. Sounds like what i need to deal in my set up…
