Concrete comparison: Twin 50:50 upright vs. half keel on 5.5 fish swallow

General Discussion
1

Hey guys, this is my first post :slight_smile:
I love technical discussions and tried to get answers on FIN shapes the last month on the web. I got conflicting results and hope to get your expertise on this. I also would like to discuss 2 concrete and different fin desings /both twins.

  1. Upright 50:50 foiled, low cant: e.g. Josh Hall Twins
  2. Modern half Keel: flat, more cant, more surfeace area: like Britt Merrick AMT or BFF

I ride a 5.6 fish, 21 1/4, 2 3/8 with quite a big swallow tail. Quite some concave at the bottom. (Banks Pan fried)

Is there any distinct separation to recommend those on wave type, speed, height? I found totally conflicting recommendations.
I then tried to study the single aspects of fin shapes such as rake, base, height, size, foil. Thought I can do my own conclusions. but some aspects are conflicting too. Here my findings.

Fin 1 compared to fin 2:
less cant → + speed, - control , - drag, +release
less surface area → -control - drag +release
less rake → -control? +release/agility
50:50 foil → + control+drag -lift -release

Based on this findings (that might not even be correct) I still dont get when to use what fin. To make things more easy, we could assume Scenario a) is a bigger and faster wave b) smaller, slower wave?

What would you recommend on your experience?
Does my approach make sense at all?

I try to switch fins on trips when I have the chance. The only thing I noticed on both type of fins, that when I am on a faster wave, the board is very hard to turn … is this called tracking? Probably I still need to learn a lot about riding fishes.

Would be cool to get some technical insights. Thanks!
Alex

2

Hello, i have a single fin, a 5.10 hpsb thin with 2 hip breaks and a bottom with a mix of a wing/chime ( its a rusty, bali single fin, look it up if you want)

So, what i want to say is that the recomended or more common sense fin size for this board would be (again…in my opinion) 6 inches .

With that 6 inches fin the board could not surf anything above chest high, would slide on the cutbacks and bottom turns ,and could not hold a steeper take off or ride mid wall on the rail.

Since i didn’ t belive this board with such a nice looking shape would simply not work, one fine overhead day i sticked a 9 inches longboard fin on it, slided it forward so the tip would point tail and went to the beach.

Every one made a comment about my big fin, joked if i got it from a boat etc…but i surfed many times after that day with it and the fin is still there on the surfboard…why?

Well, because now the board turns, holds rail, drops and even got some extra lift on the bottom turns.

My point is, try what is common sense, but if that does not work, try what your feelings say, try as many types of fins as possible.

I for exemple like to surf twin fins with regular shortboard fins ( standard fcs g5)

Cheers and good waves.

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