FCS fin manufacturing - Chinese factory video

[Marc]

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.

[Railwaysurfer]

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?

[stoneburner]

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.

[jspr]

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…

@hans

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.

However, the further the fins apart, the less the positive effect of the inside fin (~ upper wing) on the stall angle of the outside fin.

The statement that you can use more upright fins also makes sense. Sweep in single fins soften the stall by twisting and therefore reducing the AOA at the tip. And since the Thraikill fin setup softens the stall angle by the fin interaction, less sweep is needed. The more upright shape may result in a looser feeling.

This fin setup makes perfect sense to me. However I’d go for double foiled fins since the inside fin (~ top wing) is responsible for more than half the lift generated.

[Railwaysurfer]

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!

[stoneburner]

@jspr

I’m not sure if I understand the below regarding the distance between the fins:

Wish I could answer. But I’m not an engineer in fluid mechanics.
However, Hans is an engineer.
And I have respect for Hans’ knowledge and insights.

[jspr]

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.

[stoneburner]

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.

Thrailkill's Twingle Flow Visualizations

I’m late to the party, but please allow me to give my input. Below I’ll talk about top and bottom fin as if those are biplane wings, it just simplifies the explanation and corresponds to how the image is laid out. [[{“fid”:“116958”,“view_mode”:“default”,“fields”:{“format”:“default”,“alignment”:“”,“field_file_image_alt_text[und][0][value]”:false,“field_file_image_title_text[und][0][value]”:false},“type”:“media”,“field_deltas”:{“2”:{“format”:“default”,“alignment”:“”,“field_file_image_alt_text[un…