Bill Thrailkill, you owe me a new surfboard

[sharkcountry]

I’ve had a chance to ride the Duo fin board in waves up to 10’+ faces. For my size, the board is a bit too thick for performance surfing, but it catches waves really well. It works really well from under head high to just a little overhead. It’s about 6’ 7" x 20.5" x 3" and made for easy paddling.

We had a really good south swell a week ago and some waves were just hitting the size where Courts will break between the normal take off and Big Lefts. I’ve seen 3x OH sets when that happens, but it wasn’t that big. Used the blue duo that day and I had a lot of fun, but I wouldn’t say that I was real comfortable. I used a thinner board the next day and I was feeling much more in control. Trade off was not catching as many waves.

When I made the board I planned to add side fins and make it a quad if I didn’t like it. I may add the side boxes and smaller fins and see how that works on the bigger days. With all that foam it has, I have to push real hard to sink the tail in the hard turns. I think the side fins will add bite and I won’t have to think about things as much when I ride the board.

[oneula]

don’t screw around with it

leave it be and give it to me

being 20 lbs heavier than you

I thought it felt pretty good

paddled pretty well too

thought it’s feel “chunky” but it didn’t cause it “scooted”

plus it didn’t bog down

you know I don’t compliment your stuff that much

but that one is a keeper in my opinion one of the best of all th emany dozens you’ve hacked in the dirt under your house

I’d ride that in much bigger stuff for sure maybe kauai next week

who’d thought two singles would feel like that and not track or bog

bill’s a damn genius

but then again i was born and raised some 50 years ago on singles and BK/TerryF/Hakman style surfing

[Huck]

For what it’s worth I will say that I find with my higher volume boards it’s a hard transition at first from lower  volume boards. At first I felt uncomfortable. They seemed bulky and kinda sketchy.  

But after riding them consistently in a variety of conditions, I’m enjoying them much more. I can’t explain it very well, but they respond differently, and have to be ridden differently. At first different feels wrong, but gradually now it’s starting to feel right, and I’m getting a lot more comfortable / confident after fighting the learning curve. Of course waves here pretty tame compared to there. 

I’m hoping to get my twinglefin fun gun back in water soon, after adding retrofit rail channels. Was even thinking of adding quad fins so I could make comparison. It needs a bit of size or at least a bit of push. I’m old school too, never got used to thrusters. Singles and quads are pretty much all I ride .

[Monkstar1]

Burn throughs and all. With the size of my fins (7.5") I feel I can experiment with pushing them all the way up in the box. However, where they are now (mid box) they work great.

[thrailkill]

Aloha Monkstar,
What are the dim’s, on the subject surfboard? Quite a bit of surface area, in the tail. Are your fins single foiled, or double foiled?

[CassS]

Here are a couple of photos of the twingle fins I’ve been making for my Phoenix board. Thanks Bill for your advice throughout the process. I just need to drill the holes and instal the hardware and they’ll be ready for action.

Single-foiled marine ply on strips of fibreglass panel, reinforced with five layers of 4oz glass on each side plus a layer of batik print cotton left over from an inlay I did last year - no wait, it was the year before that. Still getting used to it being 2017.

When drilling the fibreglass, do I need any special bits, or should I just use a standard bit and take it slow?

[RDM]

Standard drill bit is fine.
I normally clamp the fin screw tab when I drill to prevent the possibility of splitting the tab as you drill.

[thrailkill]

RDM has provided sound advice. I do the same thing now, after having split a screw tab, years ago. Learn from the mistakes of others.

[CassS]

Nice one, thanks RDM & Bill.

[Monkstar1]

The board is a 5’8" Fox thruster from late 80’s/early 90’s; similar to the left one in this pic.

It was all dinged up so I sanded down to cloth and reglassed it with a twingle in mind. Between the two fin boxes and glass is the original fin box, covered now. I haven’t measured the tail dimensions but it is fairly wide and thick all around. The fins are el cheapos from amazon that I reshaped as well, single foiled. The ride (to me) feels like a single fin with more hold and drive, that’s why I feel I can move them up in the box. Very excited with how it turned out. I am having some problem areas with my glass job on that board that I need to repair. A few sections bubbled up and I had to cut those away. I’m not too sure why it bubbled up though, it’s been out of the water and in my house for the entire time I’ve had the board (7 years) so I doubt it was moisture related. Now, I’m not sure how to match the color with my repairs or to simply say ‘screw it’ and glass it clear, exposing the flaws.

[WideAWAKE]

Monk - I’ve got the set up in about 5 personal boards.

three boards run the same template and I’ve found that the bigger the board the farther forward my find are. My 5’10 was at 12.5 in - my 6’4 are at 13 and my 6’10 are up around 14.5. These are leAding edge numbers.

They also all have identical fins.

If put you find at the top of your box and see the extreme. Adjust back if needed.

I’ve found that there is always tons of hold and that adjusting towards and back is dialing on loose you want your tuns to feel. Flow like a single of skate like twin fin. The hold remains… At least in all my boards.

[Monkstar1]

Awesome, that’s good to hear. Where’s the pics?

[WideAWAKE]

Monk - here you go

[Monkstar1]

Nice. Love the sidecuts. Somewhere floating around here there is a twingle set up with the tail dug out, almost like a giant concave. I want to say Huck shaped/posted it. He posted a shot of a guy riding it too. I wish I could find it now. Huck?

[Huck]

…doesn’t ring a bell. There have been several posted over the years, and I’ve built a couple, but nothing that matches your description comes to mind.

[Monkstar1]

After I posted that I thought, “maybe it was LeeV”. I don’t know. I’ll look for it. It was a beautiful board whoever made it.

[asier_esnal]

Is the first time I write in this forum, the first thing I want to thank the thousands of messages so instructibos that you have written. Thanks to this, nowadays I can do my own surfboards, My english is terrible, I beg your pardon

I’ve been looking for a table feel I’ve never gotten, with single, twin, 3 or 4, I want a good parec grip for my boards around 6.0 to 8, but they have a very crazy tail, easy to cross, Similar to a skate tech slide

To see this configuration I have lit the sky, I can put 2 parallel keels, something ahead to get this grip but I will stay very crazy tail ul

I’m not an engineer, but I’ve been investigating on the subject, especially the separation of the keels, I think you put them together, then found the surfboards of Neal Purchase Jr. (NPJ) duo. That seemed more logical, but with my concern, I decided to design and analyze fluids

I have been studying the separation of the wings in the biplane planes, this is minimum the width of the wing.

Translated to surf, if we have a keel of 120mm of base (4.72"), the parallel would have to be at 120mm separated as a minimum, so that the turbulences do not collide, otherwise we can have an opposite effect to the desired one, something like ejector venturi

I attach a photo of the analysis I have done. A keel of 123mm (4.84") of base separated to 75mm (2.95") of the other, you can see how it ajecta the turbulence against each other

he estado mirando tambien tablas de windsurf, usan muy a menudo esta configuracion, con la suerte que he encontrado estas quillas http://www.k4fins.com/product-category/fins/

I think the http://www.k4fins.com/product-category/fins/ can be very valid and economic, what do you think? What size do i have to put to a short table type the hipto crypto hayden shape in 6.2? Separation between keels 150mm (5.9"). But how much of the tail to loose? I will put lanes us box of 10 inches

Thanks a lot for everything

[asier_esnal]

I have taken this very interesting page for the singlefin assembly and multisistem, could you do something similar to calculate the position of the duo?

Fin Placement - Single-fins

http://www.mckeesurf.com/?page_id=267

[Huck]

I’m sure I don’t have an answer for you, but happy to keep the conversation going in the hopes of further insights showing up.

Fin placement interests me, but I’m not too savvy on the subject.

For a Thrailkill type twin-gle setup (placed 2" apart center to center) I believe placement is the same as it would be for a standard single.

For a Neil Purchase Jr. type twin, I dont know, but my gut feeling is that he is placing them a little further forward.

If you use single fin boxes you can allow yourself some adjustment room.

Since you’re going in a little different direction, with your own research, the thing to do is probably start a new thread with an explanatory title. It would be nice to include some pictures of the twin fin boards you have, and are working on. Just a suggestion.

[Monkstar1]

I placed my twingle boxes a little farther up the board than normal with the idea that the fins would still be able to hold. And I was right. No measurements now but I’m guessing 6" from the tail?