hello all, i’m shaping a board now, something between a stubby, a fish, and an egg. i borrowed a template of a mike eaton bonzer and modified it.
it will be 6’3", 20 1/2", 3", 16" tail and nose just a bit less than that, wide point at center. 4 1/4 nose rocker and 2 1/4 tail. it is a volumous board, but it may go thinner, towards 2 3/4".
i placed a concave of about 3/16" in the front third of the board, blending into a brief flat spot before i began an 1/8" deep double concave near the fins. flat off the tail.
i’m going to go with chipfish’s advice here and put in lots of fin options. i’ll use an 8" finbox for the single fin, along with two sets of side fins. so i can ride it as a single, widow, quad, twin, you get the idea.
question one: does it matter if my fin plugs are in the slope of the concave? should the concave reach a flat spot before the fins? how does one place a double concave in relation to fins?
question two: is lokbox a good system to go with or do they all offer very similar results for my particular needs?
thanks to everyone, i look forward to reading. i’ll post pics when i’m done.
cheers, nicholas
Answer to Q1 is; no but I would measure the cant from a straight edge laid across the concave(s), no you don’t have to reach a flat spot before the fins and it varies, double concaves can be deep, shallow running from just behind centre or just around the fin area, running out of the tail or fading to flat before the tail and thats just on my boards. Check out boards that people reckon work. Generally longer deeper double concaves give more drive but its only one ingredient, (and not really a major one), dictating how a board will work. Personally I like a single concave under my front foot which develops into a double under my back foot no flat spots in between. I also like to blend the concaves to flat around the back of the rear fin and a bit of reverse vee in front of the single concave.
Q2; Never used lokbox, but yes all systems offer similar results ie get you fins on your board.
I’ve used lokbox allot and I prefer it. Its just real easy to set the boxes level and flat. I found it more difficult to get perfect cant with FCS or futures when dealing with a severe concave. Thats my humble opinion.
I prefer to have no flat spots in my concave transitions… but that’s another thread.
It’s not going to matter if you put your plugs in on the slope of a concave, as there’s enough margin for adjustment in the plug. Keep in mind your cant angle, though… bottom contours play with that. You’ll need to compensate for the 1/8" double concave by adding some cant.
On a standard single to double, I like my doubles to start at the tucked edge and go all the way to the stringer, with no flat spot along the rail. Don’t forget your lap will build up the space between your rail fins and edge, so it could end up flat if you started the concave really gradually.
That being said, I like my concave to flow around the fins. Except for bonzers, I keep my concaves flowing pretty much parallel to the stringer. I think this lets you feel the effects of the toe-in better. If you angle the concave away from the stinger, single foiled fins don’t create the same lift as if your force the water to flow into the outside, foiled surface of the fin, rather than straight at the leading edge, parallel to the inside, flat surface of the fin.
So… the fin sits inside the concave, the concave flows parallel to the stringer, the fin is canted a bit more in relation to the bottom of the board, and toed in as normal (at an angle to the stringer and the concave).