Would 9x5 twin keels, single foiled with rake work on a 7’ - 8’ mini mal with a wide squash tail?
has anyone tried and did it work?
I had a 6’ 10" squash tail quad that worked with a 16" tail in the late 80s. I thought it might be possible with the keels to go 17"-17.5" wide with the tail.
I’ll take a stab. First off, if you are building it yourself, stick a fin system on the rails, put some keels in there and check it out. I’ve never tried riding or building a board like you are talking about but a guy named Bob Simmons did back in the 50’s and liked them. His fins though, if I remember right, were not very deep. Some of the comments I remember were that they tended to track on the forehand…but in those days you kinda set a course and went, so tracking was not the problem it might be for you.
I’ve made few boards with fairly wide tails and found that if you stand near the tail, they will overplane (if that is a real term) and they spin out. So you had to turn them from more of the middle of the board. If you want to turn them from the tail you need to reduce the planing efficiancy by putting in lots of rocker or a swallow tail. I’m guessing now, but that is probably why those old twins died and were replaced by swallow tailed fish or variations on the fish.
My guess is that your design will tend to track or the fins will stall out and you’ll spin…But who am I to dispute Bob Simmons? Go for it…your options in fin systems are almost limitless and don’t really add that much weight to your board. Put in side fin boxes and a center. You can always tape over the outside ones if you don’t like them and ride it as a single…
Since everyone surfs differently, of course you should consider trying it.
If you like sharp, quick pivot turns, forget keels.
If you like Point Right running down the line, it works fine.
For the sake of efficientcy, a keel, for it’s drag, is the LEAST efficient fin shape possible (well, almost). But it has great low end, is stable, and if big enough, since you need at least two, will hold the tail in, but cause drag.
Thanks to both of you for your comments, the 16" squash quad would have had the same sort of fin area as the keels and it actually surfed really well. This quad had a 8" tail end and was 6’8" and also built a 6’10" clone that worked almost identically, the bottom contours on these where a slight rolled vee moving into a fairly heavey tail vee in the last 3rd and flattend out in the last 3". I suppose if I had a go and it was spinny I could make a small raked keel as a stabliser. I though it might make a fun skatey type board.