Twinzer fun shape - Comparing notes

rajon's picture
rajon started the topic in Wednesday, 7 Aug 2019 at 7:21am

I have an 8'4" fun shape that's using a Twinzer fin setup, and I'm fairly happy with it, although, there's some room for improvement - So I'm in the process of making a new one and it's shaped already and ready to glass.
I'll refer to my original one as my prototype
The prototype is 8'4" long and 21" wide with a 13-1/2" tail with 3-1/2" tail rocker. The fins are 5-1/2" high and 5" at the base and located with the trailing edge 9" from the tail. These are toed in 3/8" on each side, measured from the stringer.
There's a small wakeboard fin that is located 1" outside of the main fin and overlapping the leading edge of the main fin by 3/4"

I am 150 lb and 65 yo so I have been surfing large boards for a while now.
I'm happy with this prototype, but always looking to improve, so I have shaped a replacement.
The new board will have 4"TR And it will be slightly wider as well, to allow more outline curve.

I am thinking that It might be good to reduce the toe in of the fins, to accomodate the 1/2" increase in tail rocker

Does anyone have any design experience with boards like this?

Feel free to ask questions. I am willing to contribute to other guys' projects as well.

I'm not seeing that it's possible to post pics here - Am I missing something?

Thanks - Bert

thermalben's picture
thermalben's picture
thermalben commented Wednesday, 7 Aug 2019 at 7:45pm

Bert, you can post pics via Imgur.com. Let me know if you need instructions. Love to see ‘em!

rajon's picture
rajon's picture
rajon commented Thursday, 8 Aug 2019 at 6:47am

Please do - Explain instructions
I have Imgur acct that I've never used
Thank You Very Much

I'm interested in sharing
Surfing Twinzers and C-5s has improved my surfing. The channeling action of the fins creates speed the way concaves do, only better in some cases. Also there is no added lift, and they can be removable in situations where the wave's energy makes manufacturing speed unnessecary.

thermalben's picture
thermalben's picture
thermalben commented Thursday, 8 Aug 2019 at 6:52am

There are some instructions here: https://www.swellnet.com/forums/wax/41251

rajon's picture
rajon's picture
rajon commented Thursday, 8 Aug 2019 at 10:19am

prototype & upcoming shape



rajon's picture
rajon's picture
rajon commented Thursday, 8 Aug 2019 at 10:26am

So anyhow
It's not hard to tell which is the used board and which is the freshly shaped blank.
They both have some v in the back 1/3 but the older one has more.
That used board is a frankenstein that I made from a broken longboard that was given to me. That's why it has a longboard finbox, also, It's heavy!
I'm thinking that I'll put the fins 8-1/2" from the tail on the new shape.

I'm not sure that i like the stingers. They create a tracky section of the rail that tends to stick in the face when I'm backside.

Any input or questions appreciated

surfstarved's picture
surfstarved's picture
surfstarved commented Thursday, 8 Aug 2019 at 12:08pm

Interesting to see that the twinzer setup is working on a board of that size. I'm more used to seeing it on boards of the sub-six region and I've heard tell that it's a helluvalotta fun.

I'd have thought the wings would have more influence or interact more tangibly with the fins if you brought them closer together. That way, the water moving over the outside foil of the fins would be released in a bulk lot with the water releasing off the rail, emphasising the enhanced manoeuvrability that the wing design is supposed to be facilitating. Does that make sense, or am I talking gobbledegook?

I think having the fins so far back would be contributing to the board's trackiness as well. I can see why you've done it. You want a certain amount of track - it just suits the style of surfing you'd be doing on a board of that length - but moving them forwards an inch or two might allow a bit more pivot in your turns, interact more actively with the wings and reduce the trackiness on your backside.

I've never tried twinzers myself, but I have a busted up old 6' quad with broken fin plugs out in the shed that I'm thinking of converting to a twinzer, just to see what all the fuss is about.

Don't let the bastards grind you down

rajon's picture
rajon's picture
rajon commented Friday, 9 Aug 2019 at 2:50am

Something I read was, trailing edge 1" from the tail for each foot of board length.
I forget the source
I hadn't tried Twinzers til a friend wanted me to shape him a 9'0" Twinzer and I shaped a squash longboard with about a 14-1/2" tail... I followed the 1" per foot formula. The guy was stoked! He told me, "This is a true high performance longboard" ... Later, I shaped his son a Twinzer 5'6" fish and 5-1/2" from the tail placement seemed wrong so I put the fins @ 7" from the tail.
Since then, I've placed them as much as 14" from the tail for a 7'10" just to find out how it would react. It ended up working better with a small trailing fin, for stability.
Twinzers like a lot of tail rocker.
If the tail rocker is flat-ish it will connect sections like it's motorized...but when you get into a juicy section it will be hard to hold it back.
On that frankenstein long board, pictured, it has 3-1/2" TR and a lot of V by todays standards.
The V doesn't slow it down it helps it go rail to rail super easy.
My new shape will have less V and more tail rocker (4" TR)
The prototype had 5-1/2 deep fins toed in 3/8" from the stringer on each side
I'm pretty sure that I won't toe them in that much on the new shape.

If you glass on or use boxes on that 6'0" that you mentioned, just set them up similar to the pics and have the leading fin toed out a bit more to channel water against the main fin

rajon's picture
rajon's picture
rajon commented Wednesday, 14 Aug 2019 at 6:07am

Unfortunately, When using Twinzers, it's really difficult to use fin boxes to make changes in the fin cluster, for purposes of comparison.
Twinzers are set far enough back that a tri fin cluster in that position just wouldn't work.
Something that is more practical, if someone feels like swapping is a C-5 cluster.
C-5 is almost like Twinzer in terms of creating speed. Somewhat stiffer and more stable, but that depends on the trailing fin too.
I'm just throwing this in.
I know a few guys who went through numerous seasons experimenting with tri fins and quads, then found that that little fin channeling water against the rail fin is the answer.
Eliminating sideslip is key. Sideslip vectors reduce forward drive exponentially.
The trick is to eliminate sideslip without stiffening the turning characteristics.
Twinzers or C-5s can do that.

Do I sound like an infocommercial?

Another thing; Twinzers or C-5s can be too fast in critical conditions, where you want to control speed instead of create it.

udo's picture
udo's picture
udo commented Wednesday, 9 Oct 2019 at 2:25pm

Bryan Bates twinzer fin setups -Fins are Routed into the blank...no fillet around fin base..

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velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Wednesday, 9 Oct 2019 at 4:00pm

A very good thread rajon. Thanks for all the musings on placement, tail rocker etc

Always wanted to try a twinzer. I wonder how tall/how much base the little fins are. You mentioned big ones are 5 1/2 tall 5 base.

stunet's picture
stunet's picture
stunet commented Wednesday, 9 Oct 2019 at 4:23pm

Hey Rajon,

Here's a li'l info plus photos that you could use by way of comparison:

https://www.swellnet.com/news/design-outline/2014/12/05/twinzers-the-forgotten-four-fin-design

In 1990 I had a Pottz Twinzer set up the same as the Pottz in the article, and it was a great board. Perhaps the first great board of my surfing life. When it snapped I tried to get it replicated without much luck, but because of that first board I've got a real soft spot for Twinzers.

Also, I saw a photo the other day with Pat Rawson holding a four fin that was a Twinzer by any other name. Which isn't that interesting except for the date the photos was taken - 1987. Not sure exactly when Wil Jobson came up with the idea, I've heard '88, but maybe it was earlier. If not, it's possible Rawson did it first.

An academic argument, but I don't discriminate, I like all kinds of arguments.

topgeer's picture
topgeer's picture
topgeer commented Saturday, 26 Oct 2019 at 12:10pm

Hey Rajon,
best person to talk to for modern Twinzer fin placement would have to be Bryan Bates in Byron...he has been making them for years, sold heaps. I have one, my son has one, both in the sub 6ft range. Bryan knows exactly how and where to place fins.... cheers

udo's picture
udo's picture
udo commented Saturday, 26 Oct 2019 at 3:07pm

Swaylocks - put Twinzer into there search function and theres pages of info

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