I’m shaping another fish and want to use keel fins. Two questions. One, do I use my 9" by 5" keel or my 7" by 5" keel? And, how far from each tip and the stringer do I place the fins? The board is 6’ 10", 15.5", 21" 15.5." The tips are 10" apart with a 5" butt crack.
Generally, the bigger the fish the further up the fins can go. As they get pushed further up (an 8’0" ‘Whale Fish’ will run keels up about 9-1/2") the length of the base can get reduced. For the 6’10" it’s my opinion that the 7x5’s will do the trick. You’d be even more stoked if the back edges of the keels were SLIGHTLY curved rather than dead straight. With that said, 7-3/4" to 8-1/4" up from the tail tips should look about right. The rear dot for the rear edge of the fin works well about 1" in from the outermost part of the rail. Keel fins running parallel is the traditional setup but a tad pointed in to the nose can loosen and still maintain the glide. Lastly, mock the whole thing up. Use a dot of hotmelt glue to hold it together while you look at your creation from all angles. When it makes the most sense, go for it. (Hey, you can always get the grinder later like I’ve done so many times over the years and move the fins… [wink] Good luck.
In your experience, does it make much difference if they are tilted out vs straight up? Which is better?
I’ve found noticeable differences in the fin positioning. I must admit that I have not tried every possible combination of distance from tail, caster (toe-in), and camber (tilting out) for the keel-finned fish but definitely have done a lot of R&D. Mostly just what “seemed right” and interesting at the time. With that said, for the traditional, parallel-finned fish about 5’10" with VERTICAL fins the board will have a more “tracking” feel to it; that is, the board will keep going straight when the rider doesn’t necessarily want to… This was found especially true if there was any lifting type bottom contour in the fin area like a subtle concave (deep cons actually have potential to relieve the tracking “lock up” at high speeds). Tilting the fins out only 2 or 3 degrees (looks like 1/8" at the tip) reduces tracking even when still using the parallel setup. On the other hand, vert/parallel keels on fish (plural for fish is “fish”) can make for some INSANE down-the-line speed; I guess it depends upon what one is trying to achieve. Keep in mind these opinions do not reflect all the other important factors that can influence tracking and generation of speed, ie. rocker, outline, bottom contour, rail volume, foil flow, etc.
Hey thanks… A friend’s kid won the fish blank at S.A. 2003 raffle and I’m trying to help him make a decent board out of it. We’ve worked out a template but I’m pretty clueless on fish design. It will be very different from what he’s been riding (6’1" Rusty thruster) so I’m not sure he’ll be that sensitive to details but I’d like it to be functional.
I used to shape a lot of fishes in SoCal. back in the early times.Seems to me that by adding an elongated Vee in the bottom rear third of the board resulted in in a looser board.The fins were naturally canted due to the bottom configuration.The fins had no toe in.Bear in mind that these boards were shaped out of old blanks that were thick with low rocker glassed heavy.They were fast as hell down the line in hollow surf but not very good in mushy onditions.David Nuhiiwa was unreal on these type of boards with a low wide stance.I like Steve Brom’s fishes,they look right on. R.B.
Cleanlines/John: I agree on the elongated V , I’ve been doing them for a while probably from early conversations with Herb. It just made sense to me with a 17" tail to put some bottom contours to help get the thing up on edge. I just did a 6’8" this afternoon. 17x21x17, kinda of thick rails for a heavy/tall rider. I like to toe my 5x7 keels slightly, say 1/8" off stringer with the cant at 3-4 degrees. Most are 1 1/4" off the rail line at the rear of the fin base and 8 1/2"-8 3/4" off the tips. I use some of my longboard pintail templates to shape the swallows, I like 'em deep at 6.75" or so. I try to leave room in my outline for my round sureform file to get the bulk of the shaping done in the V of the swallow. No matter how you do these, with a relaxed rocker in the tail it’s going to be fast and fun. Tom S.
Thanks for the input on keel fin placement. Has anyone used 9x5 keel fins on a bigger(6’10") fish? I have 7x5’s and 9x5’s.
Hey Plusoneshaper, you mentioned something about moving the fixed keel fins on your fish. Do the keels get ruined when you grind them off or are they still usable again. thanks SR
hey ResinHead, Yeah, when they get taken out properly they get re-used. Back in the 70’s we were trippin’ on how much influence the fins’ positioning had on the fate of a board. I was moving the fins as much as FIVE times on a single hull (either REALLY curious or not very bright). You’re probably wondering how this can be done. The best tool is a pneumatic die grinder with a 3" disk but electric 5" or even an 8" but it has to be a rigid disk in all cases and coarse grits (40,36,or 24 with resin-backed disks). The technique is to “drop sand” a series of scallops to get rid of the rope, careful not to nick the fin. Just have the edge of the disk against the fin (holding disk flat and level) and drop straight down. Watch the heat. Work several scallops at once. Eventually you will reach the glass of the board; stop. Connect scallops with other scallops, finally starting to use a side-to-side motion to clear the areas in between. Got it down pretty good back in the day when I knew I was testing fin placements: gluing the fins in with “Hotmelt Glue” so the heat from grinding would liquify the glue (normally I use resin (UV now) to tack fins)and make removing the fins easier w/o damaging the lam. Also, grind the fin itself so the build up is minimized. Do this while the fins are still in the board. Hope this helps…