Thank you for the numerous PM’s with phone numbers. It’s going to be less time consuming to answer your questions this way than a series of phone calls. Hope you understand. So, imagine a board with a single fin, center mounted, that is 3/4’’ thick and hydronamically foiled. Surf the board, and it will feel both positive and somewhat loose in its’ response to the rider. The board will also carry speed well through its’ turns. Now imagine the same fin cut in half down its’ centerline, producing two asymmetrical fins 3/8’’ thick. Next move each fin 1’’ off center, and surf the board. Surprisingly there will be very little difference in the ride, compared to the thick single fin. Now continue to move each fin in incriments toward each rail. What you will experience is that as the fins move farther apart, the turning response will stiffen, requireing more effort to produce a given maneuver. The farther apart the fins get, the worse the condition becomes. I have just described an experimental path that I have traveled, and have reported my experience and observations. I would invite any doubting reader to do the same experiment and reach a different conclusion, or prove me wrong. I hope this makes my statements about fin position a little more clear, and note that it is based on direct experience, and not theory.
thanks for going to the trouble of sharing that mr thrailkill. very enlightening.
So, imagine a board with a single fin, center mounted, that is 3/4’’ thick and hydronamically foiled. Surf the board, and it will feel both positive and somewhat loose in its’ response to the rider. The board will also carry speed well through its’ turns. Now imagine the same fin cut in half down its’ centerline, producing two asymmetrical fins 3/8’’ thick. Next move each fin 1’’ off center, and surf the board. Surprisingly there will be very little difference in the ride, compared to the thick single fin. Now continue to move each fin in incriments toward each rail. What you will experience is that as the fins move farther apart, the turning response will stiffen, requireing more effort to produce a given maneuver. The farther apart the fins get, the worse the condition becomes.
Isn’t it obvious that as the fins get closer to the rail they don’t need to be as deep as the singlefin?. . . so just splitting the fin down the middle and then moving the halves towards the rails isn’t a fair test. . . whoever uses twinfins as deep as a single ? I suppose that I should be bowing and scraping in front of “The voice of experience” along with the others because it makes sense socially. . . . however my bent is towards the truth not social status. . .
Try turning a longboard from a forward riding position, yep, it doesn’t turn, it’s tracking. I suppose the same happens on a fish but I am not totally sure this is what your mean.
As for fins on fish, I am very interested in this thread 'cuz I am close to completing my first one a 6-6x22 and I have simply foiled some 7x6 inch keels but I am still unsure of position, toe and cant. My board has very little tail rocker and I am thinking of 6 inch butt-crack. Our waves are seldom powerful and rarely hollow so it will be more about developing speed and moving around sections. Any advice from our venerable swaylockers (and any youngun’s too of course!) would be much appreciated.
The stupidity of your comment does not warrant a serious response. You wouldn’t know the truth if it bit you in the ass. (which it has on many occasions) It is obvious that if I said a color was white, you would say it was black. The foregoing IS intended as a personal insult to you. You fail to grasp so many things, I thought I’d help you understand that, at least.
If I may interject, that kind of blasting ad hominem attack doesn’t do anything for you or anyone else. If you had handled the (somewhat rudely-phrased) objection’s implications, we could have wrapped one up for the archive.
But since you didn’t, Roy’s remark and your blast of acidic dismissal should actually make us examine your original post and ask, or in your case, answer, the implied questions, which would be along the lines of,
“How tall was that single fin you split in half? How wide was the tail? Was there any vee? How big were the fins area-wise?”
I think Roy’s objection actually does shed light if you split a tall single fin and moved the halves outward to positions we would mount shorter fins at. It would seem likely to track as the height of the fins (would seem to) compound the lack of leverage at those positions.
I just wondered if overall, given keel fins, the board would be looser with said fins mounted inward 2 inches rather than 1.
I think the answer is yes, due to leverage, and your experiment seems to have implications toward that finding, but you could be more specific about the fins, and less vitriolic toward people that have the temerity to differ with your assessments.
I know I know, they’re facts. But nobody’s dying here. You have no right to act that way. You have at least cloak your personal insults in some veneer of civility.
You are asking a legitimate question and getting way more than you bargained for. Being from the Point Loma area and having ridden fish “back in the day” one of the first things i did was to get rid of the long keel fins. Long fins, flat rocker, no v, wide split tails all a recipe for “tracking”. The fins on the board I posted earlier are 2" from the rail, slight toe, cant etc, Yes it worked. In the “old days” fish were pumped and flown, the new fish shapers tell me they want em to ride like longboards, settling for stiff? If you are really set on the keel fins tweak em a little and find out. You can always take em off. follow your instincts, break the rules.
I’ll buy into what you’re saying. However, at what point does a single fin spin out? I’d say (simplifying it) it’s when the rider has weighted too much rail so that the fin leaves the water, no? Therefore, since a twin fin or thruster doesn’t normally use fins the size of a singlefin, I maintain that the best place for the side fins is near the rail for more hold, especially if the rider is good enough to break the outside fin out for tighter arcs.
The question in your opening post was with respect to fin PLACEMENT, not fin SIZE. That is, after all, a different question. There are many variables that can be played with, when setting up the fin/fins for a surfboard. My answer addressed that narrow question in the opening post. FYI: The original tests were done with several boards, and fin sizes ranged from 7’‘, to 8 1/2’'. Tail width does not enter into the question. Narrow, or wide, the closer the fins are to the centerline of the board, the less the tendancy to track, and the subject surfboards are easier to turn.
All righty then. Good info–same boards, same fin template, only variable placement relative to centerline. Good to know, for twins and all boards with rail fins, seems like.
Regards, Roy