Sunset Strip

DNA A Class Catamaran Classic conversion

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I have a DNA A Class that has been converted to use J Boards.

I have some Exploder C Boards and want to convert it back to a Classic.

Has anyone else done this?

How do you get the board rake angles correct?

Any tips and methods appreciated.

 

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On ‎13‎/‎04‎/‎2018 at 6:57 PM, Sunset Strip said:

I have a DNA A Class that has been converted to use J Boards.

I have some Exploder C Boards and want to convert it back to a Classic.

Has anyone else done this?

How do you get the board rake angles correct?

Any tips and methods appreciated.

 

just get onto the Queensland A class face book page and ask. take photo of what you have and want to do. 

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The original C boards entered and exited  through the hull centreline. The j boards may have changed this. If you use the converted cases check your tips dont go closer than 0.75m from platform centreline.

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On rake, the original C slider had about 12mm travel. The J boards use heaps more rake to create lift to fly.   You wont need the full travel to get skimming.

Too much rake in windy the c will lift out and step sid3ways. Exciting but slow.

Beware that at zero rake in windy the boat can trip even with winglets.

Have fun

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The board slots have been moved out from centreline. Installed the boards  today.  Moved the slider as far  in board as the case allowed. With the board fully inserted it is less than 75 cm to centreline. The boards are quite long, much longer than the J's.

Only way I can see to make 75 cm to centreline, without major mods is to raise the boards up to get 75 cm and chop the top of the board off. This would make them about the same length as the J's.

Thanks for the replies.

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Get dimensions from DNA or someone on their C-boards. Its likely the Exploder boards are longer and the whole trunk is further outboard on the Exploder AD3's with C's to accommodate. The board radius could also be different. I say that as I'm not following how a lower bearing installed further outboard in the hull would cause the board tips to be further inboard on a C (I understand on the slider location having the opposite effect of the above).

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The curve of the exploder c boards must  have a greater radius. 

Does anyone have a standard DNA curved board. Could you please measure the chord distance, the length of board and distance from the chord line to the board at the greatest distance and the position along the chord line the measurement was taken.

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SS, there were 2 different radius and lengths on DNA C boards. Both had success. My take was the shorter more curved boards were better for skimming. Havent got measurements sorry. 

 I reckon your proposed solution of shortening your boards to measure in 0.75 is fine. You could even move top plate outboard a little and shorten more. That should give more horizontal and therefore more lift.

Have fun!

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Have found out that the original DNA boards were 1.2 metres with a radius of 1.2. Projected 690mm under the hull. The longer boards where 1.3 metres with a radius of 1.45. 790 under the hull. 

The exploder boards I have are 1.45 metres with a radius of 1.245. Drawing the radius of the old DNA. Boards and the exploder boards on the ground shows they are pretty much the same in curve. 

The only way to get them to fit without cutting would be to move the bottom slot outboard and move the top inboard. 

Or leave the slot at the bottom and move the top slot In a bit. This would be pretty close to the original boards, then cut the top of the board off about 150 mm. 

Or as sonofagun suggests move the top out a bit and get more curve in under the hulls.

This is the easiest solution without cutting holes in the bottom of the boat.

 

 

 

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Before you cut, I would mark the boards. Get them fit as you think is best, mark the maximum down location and go sailing. As long as you are happy with that in a range of conditions (0-15), then I would cut the boards.

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2 hours ago, samc99us said:

Before you cut, I would mark the boards. Get them fit as you think is best, mark the maximum down location and go sailing. As long as you are happy with that in a range of conditions (0-15), then I would cut the boards.

I've converted two foiling DNA's (not F1's!) back to c boards and they sail fine as long as the cases weren't moved too far forward. Max about 100mm. Cutting a bit off the board to fit the rule is the easiest solution for you and will work if you have the boat I think you have. 

Incidentally the latest Exploder c board platforms were delivered with slightly too long boards. We cut 30mm off and no problem. 

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The cases on this boat where moved forward 50mm. The boards are now fitted and marked. Going to go sailing and try it out, if it's all good will chop them off.

Thanks for the replies, it's been very helpful.

 

 

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Can you tell us your results, on moving trunks only 50mm?  I have an 2014 A14 eXploder that came with Jz boards.  The Florida and East coast foiler guys say these trunks are way too far aft, although Matt Struble won the 2015 North Americans with this boat as is on Jz boards.  I don't do well on this rig at all, re foiling too intermittently.  Before I go 100% to my Hall C-boards, I woul like to stick in some  Z10s now on hand.  I see from the above that others also suggest moving the Z10 position forward a lot- like 50 cm.  These A14 trunks are pretty far aft, and just about correct as is for C-boards.  BUT- My sidestay shroud connections are very close to the existing trunks --like just 7 cm (70mm/ 2 inches) forward:  Thus moving my trunks more than 7 cm to help make Z10 boards work would be a bloody nuisance!  ( I know that several A14 and A15 boats have been so modified, but understand that these have front crossbars also moved forward). Comments on these choices would be very welcome.  I want to go at least as fast as my first A-cat Woody foiler in the little thumbnail ^  with aluminum lifters in 2001, dammit.  .see  www.catcobbler.com 

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Dave,

  You are asking the right questions but I think looking for an answer you aren't prepared to hear. The A14 with the original trunk positions is not stable at all, you can watch Nathan and Ashby at Takupana worlds and see that for yourself. Board design of the J/Z's is certainly a big reason for that but the pitch stability is not forgiving. Matt Struble is a world class sailor who made it work and at a time when foiling was very new in the U.S, and the class for that matter.

I think you are best off putting C-boards back into that boat as the beam and trunk position should be fine for that. The hull shape is fine if you want to do a complete mod, but it is a lot of work (I have done it) and I only did the trunks as my beam is in the same spot as the new boats (just not as stiff, which could be a real issue). Moving a beam is not something I would advise, especially with the re-surgence of the classic fleet, you can sell the boat as a classic for good money and buy a solid foiler for a fair bit less. Or sail the boat as a floater, racing a foiler is demanding but rewarding.

-Sam

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Two thinks can help the A14 that are very easy to improve foiling:

1) Pull the JZ boards up a couple of inches if you aren't already.  This makes them more progressive. You will need a little more rake to foil but will have more stable flight.

2) Put larger horizontals on the rudders.  Emmanuel has these I believe.  I was amazed how much these help and wonder about putting some even larger ones on a boat like yours.

It still will not foil like a new D3, but it will be improved with minimal effort and expense. 

 

I know Daniel converted his A15 boat from JZ to Z10 at the same case position as yours and has seen a significant improvement.  He just moved the sliders inboard at the top to fit the different geometry and did a little fairing underneath.  

 

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Thanks, Sam & Lost.  You have both reinforced the likely best options.  I have been jamming my XJ's Hall C-boards down the stock A14 trunks set for Jz boards for a year now: Messy results- with poor boat speed, slower than Jz!

A year ago OH had started "The Caveats" for an eXploder A14: if/then statements- except not for computer code.  We agreed that proper Z conversion pretty much meant drastic trunk movement forward for lift to be in the correct place for proper stability: I even bought a $40 led-lit video camera to be operated thru my PC or iphone to look thru a hole in the trunk at existing A14 shroud attachment. (video works ok).  OH widened his Z10 boards a bit for stability instead.   

1) Understand lifting Jzs a bit:  not tried yet.  2) Larger horizontals- I put then on a year ago, after the manatee attack which broke one off at the Rudder Club dock!  Rudder angles/ setup experiments have been frustrating.  Matt's rudder setup was for different sail and all that entails.  Foiling is great, but fleeting-- after long intervals of floating.  3) Which Daniel?

 

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2) The rudder winglets available a year ago are not the big ones. The new ones are 25% bigger. Whatever foils you are running I think the big winglets make a big difference!

C-boards need to be setup properly as well, which your trunk without shimming isn't. Foiling rudders are also too big.

Since you have the Z10's I would fit them in the existing trunk location. If that plus the big winglets don't get you foiling properly I would go back to C's.

For more help, you have our email addresses!!!

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Don't forget to make sure the boards don't also go outside the 2.3m width at any time during their operation as well, not just the .75m tip distance.  As the bottom slot is further outboard than the top slot, it could throw them out wider too.

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