With the tables of http://www.mckeesurf.com/?page_id=267 and the area and weight of the keels, I have drawn the center of gravity for both trifin and cuard.
Careful, not the momentum center of forces on the yaw axis. I am not an engineer and this is costing me, but I have started working with the free program xflr5, which is to make airplane models. I hope that in a few days I can give some more information
But doing it by intuition I think that for a 6.3 we can put the fins to 8 or 9 inches from the tail. These are of a shape centered just between the 4 fins of a cuad. As the mckee table marks a separation between fins of 6 1/2. For a tail of 15 inches wide
what do you think? crazy?
The program xflr5 I have not been able to simulate the keels of surf to subject them to turbulence, I can do it in another program type solidworks but I do not get the halos of stability, so for now this idea I leave
I have to do tests on keel size and distance to tail but if I want to keep distances from this table http://www.mckeesurf.com/wp/wp-content/uploads/2012/10/table_02.jpg
Your hand wringing concern about a possible VENTURI EFFECT, being somehow detrimental, is exactly the effect that I intended to create. A low pressure area, between the fins, helps to sustain water flow during high AoA maneuvers. It is what makes the (my) twin pairing of fins, work so well. Test your own theory/beliefs in the water! Step away from the keyboard, and into the shaping room! Better yet, start your own thread to discuss your theory/beliefs, and experiences in the water. Iām sure youāll draw more attention to your subject, and concerns.
Just want to bring this thread back to life. I didnāt believe the fin setup when I first saw it years ago, but I gave it a try and I canāt find anything negative about it. other than needing 2 boxes and 2 fins. Iāve tried 3 or 4 different size and shapes of fins and I havenāt had a bad experience using it yet.
Took my old Thrailkill twin single fin out again and had a lot of fun. I last rode the board as a single and it was a lot of fun too, but I hit a rock and popped the fin box up. When I fixed the board, I removed the center box, so itās now just a ātwingleā.
The best part of making your boards is being able do anything you want. Experimenting with very unusual designs has made surfing so much more fun. Best part is when you get compliments on the boards you make and especially when you get compliments on riding them.
Mahalo Nui Loa to Bill Thraikill for sharing his Manaāo and opening our eyes.
Howzit sharkcountry,
Just curious, are you just using regular double-foiled fins or asymmetric/single-foiled ones?
Many thanks,
Andrew
I use both. I made 3 sets of fins a few years ago, 5" 6" and 7". The smallest are double foiled and the other 2 are single foiled fins. I have 2 boards with Bill Thrailkillās ātwingleā and Iāve made 2 NPJr Duos.
The first time I used this board I had two 9" standard cutaway fins that I had been riding in my 8ā eggs. The board worked fine, but I think the fins were too long. I used single foiled fins with the flat side out and it felt really good, but the board is very flat through the middle and tail. Because of the low rocker, I didnāt use it much, but it is a vey good board for smaller weaker waves, and it works great in waves from head high down. I used the small set of double foiled fins yesterday and it was a lot of fun. For a board with very little tail rocker, it turns easily.
Iāll try to take some photos of the board as it is now. This is the original board I made years ago, but it had a massive delam. I made the mistake of leaving it in the sun too long. The hump on the deck is a 1/2" high delam. It was also just a bit too wide for me to comfortably carry, so I cut it open to fix the delam and narrow it a bit. I was able to change the outline a bit. The bottom is the same except I took out the middle box. Funny thing is I didnāt put a leash plug in this board and have never ridden it with a leash, but it works well and I havenāt had to swim much when Iāve used it.
Did Bill ever give anyone a new board as requested?
Hereās the board as it is now, it is 7-2. I stripped the deck skin off and used balsa as the new deck skin. The outline was pulled in a little, and the center box was replaced with balsa. I must have had a leak where the boxes were for a while because the skin shows water damage. These are the fins I made for the twin single boxes. The blue fins have a foam core and they are about a 1/2" thick. The small fins are made from g10 and I layed up the yellow fins myself. I have the yellow fins in another ātwingleā.
Bill gave me a template for his 8ā x 21" Hawaii gun. Iāve made about 4 boards using the rocker, and 2 using the outline. I used of of those boards last summer during a hurricane swell and had an intense barrel on it, but got eaten up. There was a photog out shooting 5 young pros that day, the Moniz brothers and others I donāt know. He was right there when I got that wave and I asked him if he shot it, but he didnāt. He did say he watched it, and a couple others saw it so I was stoked.
Good for you. You just inspired me to ride my twingle again. I really want to try the twingle setup on a longboard. For some reason I feel it would help hold the wave during nose rides.
So Iām about to take my first step into shaping boards. Well reshaping since I live in Taiwan and the cost of blanks here is a bit out my price range at the moment.
And Iāve actually decided on making a ātwingleā for my first board.
So Iāve been poring through all the posts on swaylocks on twingles and I just want to make sure I understand the design properly.
Two single fin boxes spaced 2ā apart, straight no toe in no cant. I know the recommended fins are single foiled.
But would using any single fin be ok as well?
Also how far up from the tail should the fin boxes be placed?
My plan is a 7ā6 x 21.5 x 2 5/8 egg. Low rockered and flat bottom.
I have 2 of the Thrailkill twingle style boards. One is 7-2 the other is 8ā. I ride them with single side foils and with the flat side out. Havenāt had any issues with them, but I havenāt ridden them for over a year. I would ride the 8ā in waves up to about 10ā faces and the 7-2 in smaller waves.
I have quite a few boards and ride a different board almost every time I surf. It keeps things fresh and challenging, but I would probably be better off riding one board a lot instead of changing it out all the time.
I also have 2 NPJr duo type boards, but I added side fins and usually ride them with the side fins and the single side foiled fins in the center slots.
Billās design feels like a single fin, the duo is different. Billās design will be OK with normal single fins. I rode it with cutaway fins and regular wide base fins before I scored the single foiled fins for the big center boxes.
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Yeah, I like the feel of singles but where I live in Taiwan the waves get really mellow and fat more longboard friendly. So less energy from the wave and as Iāve been reading up on the twingle with its increased drive and speed through turns it got me really excited to try it out here.
But we also get typhoon swells so added bonus of increased hold for the bigger days.
Iām not sure where to get single foiled single fins so Iāll probably be running with normal single fins that I can get my hands on.
To me the difference is very subtle, but I donāt tend to think much once Iām on a wave. I canāt say there is more hold or drive, but I also canāt say anything bad about them. I originally made my twingle to be able to say itās BS, but to my surprise I couldnāt say that. I didnāt find any negative in the design and it works with standard fins, it works with cutaway fins, and it works with single foiled fins. I was lucky to find someone who had ordered a couple of sets of single foiled fins from Larry Allison for an experiment. Once he was done, he didnāt need them and I saw an ad on our local Craigslist.
I didnāt get the response I thought Iād get with the NPJr Duo, so in those boards I added side fins and that made those boards work better for me. Canāt beat the drive that fins on the rail do for the board. Iām riding an assortment of twins from 7ā down to 5-9, and singles from 7ā up. I should add that I tend to stand further up than todayās surfers with their back foot almost on the end of the board. It is something that goes back to learning in the late 60s and riding single fin boards. I tend to move back and forth on the board the way we did back then.
Iāve been making my fins for several years now and I am having fun making different shapes than the status quo. Iām currently playing the designs Cheyne Horan uses. Very up right airplane wing shapes. Iām also trying inverted cant, where the fins are canted toward the center instead of the rail like most boards. I think Bill mentioned this years ago as well. Cheyne says he goes up to 5 degrees in. I have this on a McCoy Nugget style of board with a quad setup.
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They look like really interesting fins. The reverse cant sounds interesting too. With your NPJ Duo are you running additional fins near the rail or ONLY fins near the rail and leaving the Duo fins out?
Sharkcountry thatās awesome being able to try out so many boards and designs. Thatās originally what got me wanting to shape my own boards, to be able to experiment, try out alternative shapes, and dial in surfboards for my style and my local break.
The surf culture and community in Taiwan is still quite young comparatively but growing a lot these past few years. But most Taiwanese surfers are still drawn to buying name brand models and the new popular thing. Plus there are only a few local shapers here. So access to alternative board designs is quite difficult since the second hand market is mainly saturated with a bunch of name brand hpsb. And getting an alternative board might run you up an easy 1.5-2 grand!
I think in all my years here Iāve only seen one 5 fin bonzer, one twinzer, and one asym. Thatās it!
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I started making my boards again because the shaper I was getting boards from didnāt want to change his design. I wanted to alter a shape he was making, and I thought it would make the board better. It took me a while, but I finally made that board and it did work better. Iāve used the opportunity to make all kinds of boards, flat rocker, too much rocker, rolled bottoms, concaves, triple plane flat bottoms, big fat rails, thin pinched rails, etc. I often go too far, but Iāve learned a lot of the things the old guys had to learn and why they do what they do today. My thinking is that I can go to someone here and get a very specific type of board that will be great, so if I want that I have that option. We also have a big factory here that makes all kinds of good boards. I can make a board myself for less, it might not be the same quality as what the factory makes, but no one makes the crazy boards I make.
Riding a board I shaped, glassed, with fins I made, and having a blast is what keeps me going. I also make blanks by recycling foam. For me that is priceless.
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What was your experience riding the NPJr Duo fin setup. I was reading a few things of him discussing the setup. He said it was the best of both worlds (twin fin and single fin).
He also mentioned needing a wider tail to make it work and the waves needing some push to them.
Did you find that to be true riding his Duo setup? How did his setup compare to a twin fin or keel fin feel?
But I also saw Thrailkill mentioning that the spacing of his fin setup would likely induce more tracking.
It didnāt have the drive I hoped for until I added the side fins. I used the single sided center about 6" tall, with smaller side bites the last time I used it. I plan on using it this summer, along with a bunch of old boards I had wrapped up and in storage.
Twins are looser, with a lot of drive, keels have even more. I like twins now that I understand how to ride them without breaking the tail loose. I like the free feel without the back fin, and the drive. I like quads too, Keels, then twins, then quads. Singles are fun and very neutral. I like mid length singles and sometimes I add small sidebites. Iām an old surfer, so those tend to work best for me and where I surf. Thrusters have more control, better for the radical styles, the young rippers.
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