Never mind, I found it, but if any one has any other recommendations for the fin placement then I am all ears.
Blast from the past!
I was olphart shaper years ago…
Now just plain old mattwho…
Ditch the McKee and the hanalei stuff.
icc’s advise is a great place to start.
“OK - here’s how the fins are placed on the 9’0 I posted a picture of. Was a bit off on fin placement. The board, which has a 13 3/4” tail, measures at:
Fronts at 16", front of box 2.5" from rail, rear of box at 1"
Rears at 8.5", front of box at 3.5", rear of box at 1.75"
This set-up obviously different from the McKee set-up, who sets his rear fins much closer to the stringer and much straighter. The shaper of this board, Art Coyler, former production and team shaper at Rusty (now shapes in Oregon and Japan), uses the Rusty formulas with his own tweaks. And that’s the thing about quads, so many ways to skin the same cat.
As stated earlier, I really like my fins forward. An eye opener for me 20 years ago was when Rusty shaped me a step-up and a semi for OB ( my paddle out for decades), in which the fin sets were both pushed and widened, which provided a much larger sweet spot for turning and driving, became the basis for all subsequent boards, from the mid length 5 fins I mostly ride to my HPLB’s. (on 2+1 HPLB’s, running the side fins at least 16" up really ‘shortens’ the rail line, gets me off the tail, and actually proivdes more leverage for turns and cut-back. When I ride an HPLB with the side fins closer to the tail, I feel like I’m now pivoting turns vs. the railing them that I prefer).
Here’s some words from Rusty on fin placement:
"Early on I took a fairly simplistic approach to it.
Early quads were an attempt to add drive and control to twins. In 1980/81, Twins were de rigueur. Since 1982/83, tri-fins were most surfers’ experiential basis. In my mind, I’m starting with a tri-fin. So I took the rear fin on a tri, and was theoretically splitting it in half. The more the rider wants the feel of a tri, the further back and closer together I’d keep the fins. If a rider was after more of a twin-fin feel, I’d move the rears towards the rail and the front fins.
My common middle ground: for argument’s sake, 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.
Fin size: Fronts are similar to tri-fins, perhaps slightly smaller. Rears: profiles similar to fronts reduced approximately 10% in overall area. You can adjust drive by swapping out rears with different aspect ratios. More upright fins for tighter arcs. More rake to add length and draw to turns.
Foils: Your preference on fronts…your favorite tri fin fronts are a good starting point. If you are a fan of cambered fins – stay with them. If you prefer flat-sided fronts, you will probably like them in the trailers as well. Smaller, weaker surf; flats are probably the go as they react a little quicker and provide instant feedback. Bigger, more powerful surf – most prefer cambered or dual (full) foil trailers. Less prone to cavitate and let go. Some prefer full-foil trailers in everyday surf, citing more “feel”…smoother, cleaner, etc. Not as fast.
Cant on rears: Typically, I halve the angle of the fronts. It can vary according to intended use. Smaller softer surf; a little more cant will add some lift and looseness. Conversely, less tilt will increase speed, hold, and drive.
Nose vector (line towards nose): I typically point all four fins to approximately the same place, which depends on board length and type of surf the board is intended for."
The board I made back then worked better than I thought.
Huck got a chance to ride that board.
For a HPLB, I’ll give it a Bingo…
I also endorse Robin Mair. He shaped a 9’4" quad longboard for me. It is by far the fastest Longboard I have ever been on. Even when the cost of shipping from Hawaii to Florida was factored in the Board was a littel less then what you would pay for one of the Big name builders.
Check out his Gearbox Fin system he has some very good info on quads for Longboards. Robin has been building quad Longboards for a longtime.