jspr, another thread for you on thick single fins:
“Is this mainly to keep the drag low?”
Not sure why ~1/4" seems to be the defacto thickness for most fins (in context of shortboards).
Hot-take on why it’s that way for injection-molded fins, there’s a point where injection molding has a max wall thickness before you get “sink marks”. My guess is this was a limiting factor?
And they seem to work just fine, there’s so much variability in surfing, even if you could quantify a 15-20% improvement in drag, in the real world that probably isn’t noticeable.
I think of the aerodynamics of a flat plate vs. an airfoil. It’s very counter-intuitive that a flat plate has significantly more drag than an airfoil that is multiple times thicker.
Mostly it just matters to us on the fringe who like to tinker around with this stuff.
In my mind the benefits would seem even greater for a single fin longboard though. There are a lots of threads buried in the archives of people making thick fins.
Also, what stoneburner said plays into it… in theory a thicker foiled fin should generate a bit more lift so you could reduce the surface area (ie: reduce the overall template size).
Thanks!
Really appreciate the input!
Started to reply yesterday , but couldn’t finish , and later found that my thoughts had gone in circles.
Like you said , there seems to be a consensus that side fins work well just the way they are , I’ll make thicker ones and see what happens.
Does anybody know what happend to Blakstahs system? I couldn’t find any trace of the surf trucks…
What’s your take on clustered fins?
Bill Thrailkills twingle setup seems to incorporate a radically different idea - stabilizing a protected low pressure zone between two fins - ( which in my mind offsets the idea of the importance of area of fin in the water ) .
Am I just tripping here with my understanding of the setup?
My only metaphor for understanding this has nothing to do with surfing. What I feel in the pool when swimming laps together with good and/ or bad swimmers , or what happens when drafting on a bike in a group translates more into my concept than surfing.
I should stop reading psychedelic fin threads at night…
@Railwaysurfer
Making the moulds is actually a spin of of trying to print fins in a variety of sizes and foils.
I couldn’t get to work what others showed here on sways, printing the core and then glass over.
If I print the fin to it’s exact size I end up having the same trouble like lawless , it’s difficult to get the dimensions for the box right without compromising the strength of the glass.
The moulds are a bit of a dead end though, it’s time consuming to make them , but they allow to play with the layup of fibers which is cool.
The next thing I will try is to print the fins with a slot and insert a base of g10 . I have yet to find out which material prints best and glues best. Comes in handy to have a fat foil;)
You could spend your whole life messing with fins. And if you do, post the results.
The twingle setup allows for a smaller set of fins. How much is up to experimentation. The twingle setup is heavy with traditional boxes/fins, so smaller fin size is good.
You can build fins and postulate up to a point. The best test will be in the water.
Ooh that’s got the wheels turning!!! You could get a base machined out of light weight aluminium and use a machine screw to fix different fin templates over the base. You could do the same with solid fibreglass I guess?!
What would stop you glassing a solid base onto a board and having a “cover” fin slip over the base? You’d have the advantage of glassed on security with the interchangeable aspect of boxes?
The old Morey-Doyle closed-cell foam boards had an embedded FG tab that rose out of the board. The fin slipped over the tab and was held in place with 2, 2-piece screws.
Hey Stoneburner , thanks for helping out!
Took some time to read through.
I’m not sure if I understand the below regarding the distance between the fins:
“this shows indeed that fins close to each other should have roughly the same size as the single fin. While a twin fin on the rails can reduce the fin size to almost half the size.”
Below the quote from the OG post…
Oh interesting, just goes to show that just about everything has been trialed by someone, somewhere at some point!!! I wonder why it never took off, seems like a good system? Manufacturing ease maybe a reason the current system took precedent?
I need to read the Twingle thread, still going on the Thick vs Thin!!!
I’ve trialed the Duo set up and really like it, just a case of bringing them in a bit closer!
I feel the same. I asked him , to understand his answer more homework on my side is required;)
My problem is that Im not sure if I understand the vocabulary in the first place.
I’m a retired scientist. While I have some decent understanding of the most basic concepts, for me, fluid mechanics gets very abstract fast.
Here is some more of Hans’ input about the Thrailkill Twingle.
I was wondering after the fact of developing a fin that really works and is like a night and day change how would you begin to get it out there or into one of the lineups for these fin companies. who would know of a contact for this, its a twin fin design. Ive been running it on my hollow wood surfboard 7/0 performance shape. Its so good I would like to have an actual fin maker look at making some. or at least try it. Ive tested it against all sorts, power twins, keels, it has something over them all
You might want an NDA agreement and non-disclosure contract before showing your design to a manufacturer.
The business world can be ruthless/shameless.
Hi again. Thanks guys, i agree. I really want to show you guys a pic but it will be gone in a second. its a real game changer, honestly on every board it somehow makes drawn out turns and sharp turns in the pocket feel buttery smooth and controllable, it definetly something no one has come up with before and unique, and works. I just wont surf another fin now, and these are twins of all things
Would be cool if you keep us posted on the developments.
I was thinking of NVS too, if your fin can be cut from a standard panel. They offer a lot specialty and shaper cooperation fins.
If your fin is somehow different in the 3 dimension and would require a very thick panel to cut it out you should probably look for somebody who is also moulding fins. Hanalei fins/Robin Mair would be a company that comes to my mind …
Will keep you informed. NVS have responded positively. I think I will dial in my programs and files and get together half a dozen clean sets in alloy as the fin developed in alloy after iterations may be dependant on alloy in terms of its flex and design. or i have come up with a twin fin design that works in both. Will get clean ones and try getting some made with arrangements by NVS next year perhaps. for now I only use them since they are so much better so there will be alot of time for durability and anything else that may happen in the mean time. Will keep you all posted. One day you might actually see them, sorry about that in the mean time!!
