howdy Swayfam,
i have a 6’8 single fin I built. 20 3/4 wide at a few inches ahead of center with 14.5 inch tail. tried an upright 7.5 template fin that I wasn’t a fan of in the board. I have a 8” greenough 4a in the board now which I like but I feel like 8” of fin is too much. Do y’all think a 7” greenough would be better or is that too small? I want it to hold and have a lot of drive. I am getting these two things with the 8” fin but it feels a tad slow. Any suggestions?
The fin is feels slow/mushy because it’s flexing. You want a stiffer fin that will hold better and be more responsive. It looks like the trailing edge of your fin is at least 6" forward of the tail block. If you lay a fin on its side so the base chord is on the stringer at that position, you need about 30% of the fin to overhang the rail so that the fin will stick when you need it most.
With a 12" width just ahead of your leash string that means that 6" to the rail + 30% = ~8". If you go too short the fin will let loose when you make that big bottom turn. If you use a flex fin it will let loose on most anything above head high.
An early 70’s design deserves a 70s fin, like the Parish fin.
https://www.trueames.com/products/tom-parrish-single-fin
My opinion only
I wouldn’t think the board would feel slow from a 8" Greenough 4A. If you have anything else try it, and also try moving the fin up or back too. I’ll use a smaller Brewer (same as the Parish/Smith) style fin to replace the 4A. Like replace the 8" 4A with a 7" Brewer.
That’s a really good looking board.
Thanks guys. I appreciate the help. I only rode the board once on 1 good day. I liked the way everything went I am just curious if there would be a dramatic difference in speed if I went with a smaller fin. I just dont have enough experience to know if a 1" or .5" reduction in fin depth would make a noticable difference in speed. But i definately dont want to sacrifice hold or drive because I hate spinning out on hard bottom turns. the upright 7.5" fin definately spun out a few times on hard bottom turns. I moved it back 1/4 of an inch and it held but then felt too stuff. it was the Futures Machado single fin. The 8" did not spin out once. So was just curious about others experiences on similar boards and what fins they have used. It looks like I need to try a real deal 70’s style fin. I’m gonna try and get my hands on a Parrish Fin. Thanks yall!
When I was younger all boards had one fin. When the adjustable fin box started being used, we’d move the fin back to make the board stiffer and hold better on stronger waves, or move it forward to loosen the board up for smaller weaker waves. I usually will not place the tip of the fin past the tail edge, anything between that and all the way up would be used. A longer fin with more rake can be moved further up. Larry Bertleman, Mark Liddel and Buttons would have boards like that. This is a board I bought around 1977 or 1978, I think it was a 6-6. The fin had a lot of rake and could be placed way up.
Harry, that is an awesome board! I will move the fin around a bit and see how that changes the performance of the board. Thanks! Any good waves at Diamond Head recently?
In all fairness, it’s a nice board but if you’re comparing performance to a modern thruster, you may be experiencing the reason why the thruster ‘took over’ like it did. By giving a standard board a wider tail and by placing two fins on the rail along with the smaller center fin, a faster board that still maintained control and maneuverability was born.
I’m not knocking single fin boards but… in all fairness, a modern thruster design inherently solves some of those problems you’re having. Having the same or even more fin area placed in strategic positions closer to the rails might be a cure. If you havent yet tried it, you might consider placing a set of plugs and sidebites on each rail. A small center box fin might complete the transformation.
If you still don’t like it, pull the sidebites/small center fin and carry on with the single fin experiment… the side plugs aren’t going to hurt anything.
A single 7.5 inch deep, THICK foiled fin, will most likely make your concerns vanish. I’ve had that experience, more than once.
What Bill said…
We had a couple of months of good surf with overhead waves and swells almost every week, then it stopped. We’re in our flat spot, so I haven’t surfed for over a week, maybe surfed once in the last 2 weeks.
This summer the wind has been blowing stronger than I like for Diamond Head, so I’ve been surfing at Tennis Courts in Ala Moana Park again. It’s been a real treat to go back there where the water is always smooth and the waves are good. Best part is I’m seeing friends I surfed with out there over 30 years ago.
Hope you get that board figured out, it’s a beauty.
I’ve found what John says to be true, but I also still ride the singles and I love them.
I think older surfers who lived through the single fin era have an easier time riding singles. But many of my friends are riding modern long boards with 3 fins. They like the extra drive the side fins have. With single fin boards, I tend to ride further forward, except when I want to make a sharp turn. When I go back to boards with multiple fins I have to force myself to keep my back foot over the fins.
Owen here’s a few photos of fins for you. The photo with the 3 fins are from a talk Bill Thraillkill did. My Sways friend Les Waddel sent it to me.
I have all of these shapes. I’ve only used the Bonzer fin in a 6-6 Bonzer 5 I made a while ago, and I haven’t used it for years.
I really enjoy riding single fin shortboards. This is not my first one. I like thrusters too! What Bill said made me remember that the other single fin shortboard I built does have a glassed on thick foiled fin and I really like the feel of that. I should have thought of that! It also has a lot less rocker which might relate to the speed thing too. I havn’t riden that board in a while. I appreciate all the help and I will consider all of the advice/suggestions when building another board that is similar to this one. I am having a lot of fun on this board and have been getting some great rides but I always like to hear what others have to say so that I can make more informed decisions when buying/building fins and/or building boards. So I appreciate the insights!
The Rainbow Andrenni “A-Flex is what I recommend for that board. Based on your initial comments and your desired effect of more drive; The Andrenni will do the trick. Thick upright fins create a “pivot” effect. Doesn’t sound like that is what you are after. The A-Flex will snap out of a turn. The turn itself will give you necessary speed and drive.
Thanks for the suggestion McDing! I will check that fin out.
I started seriously revisiting single fins a few years ago. I wanted a “modern” ride with just one fin. I tried LOTS of different fins. Some too big, was riding the fin more than the board. Some too flexy wangy dangy. The just did not have the positive respnse and release I wanted. I finally dug out some golden oldies. These did the trick. Only problem no one made em. Fortunaly Bahne is willing to make small runs for me. Fin placement is super important. Yes too far up the do not have the drive I wanted and become more of a pivot turn fin. BUT moved back they did everything I was after. So in your board I would recommend a 7.25 inch fin like the picture at about 6" from tail.
This 7 1/2" has been working well
It features a forward foil , something from the mid 70’s.
NPR Jr has become a fan of this type of foil .
Those Are some nice looking fins guys! I think I am def going to try and get my hands on a fin that is closer to those templates. The True AMes Parrish fin might be the easiest to get my hands on on but I will be keeping an eye out for other fins that might fit the bill. Thanks for all the help!
Pardon my ignorance, what’s a forward foil?
