new stuff in the a-class

interesting stuff out of the Netherlands - http://www.dnacat.bl...3-update_5.html - less curve than the mayfly, so that might solve the problems of the mayfly going sideways. How does the sailor control the height of the boat? Hopefully they can do some boards that works straight out of the box, so they don’t repeat the problems with their first generation boards and rudders..

And perhaps we should change the rules within the class, so a 20-25 m2 gennaker is allowed - it would give more power downwind so flying is easier + it could make the design of a rigid wing more simple because its only need to do the job upwind?

all the best

Lars

IMG-20130105-WA0000.jpg

alcassworlds2011mayflyfoils470.jpg

 
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juniordave nz

Member
355
1
Auckland
How do they get that little tip on the foil in from above? In the article they talk about the need to be able to do this, but it looks very tight. Be interesting to see it fly.

If you want gennakers, go sail f18's or the like.

I do wonder whether the rule should open up the 750mm measurement though. Maybe make it 500. Still restrictive, but would allow a lot more variation.

 

AClass USA 230

Anarchist
961
52
Louisiana
Do the "tiplets" act like end plates at the end of the foil and reduce induced drag? This would be similar to the "winglets" you see on airplanes and I believe the practical result is that it makes the water "think" the span of the foil is longer. I also cannot figure out how you get the board up and down the trunk with that tip. Cool stuff.

 

Doug Lord

Super Anarchist
11,483
21
Cocoa Beach, FL
interesting stuff out of the Netherlands - http://www.dnacat.bl...3-update_5.html - less curve than the mayfly, so that might solve the problems of the mayfly going sideways. How does the sailor control the height of the boat? Hopefully they can do some boards that works straight out of the box, so they don’t repeat the problems with their first generation boards and rudders..

And perhaps we should change the rules within the class, so a 20-25 m2 gennaker is allowed - it would give more power downwind so flying is easier + it could make the design of a rigid wing more simple because its only need to do the job upwind?

all the best

Lars
=======================

Thanks for the info! Are they using rudder T-foils like Landy or rudder "J" foils like the Mayfly?

UPDATE-answered my own question:

"Winglets are available for sale now and can be retrofitted to the old rudders. Winglets are identical to ones Mischa used at The Worlds, which are almost identical to Landy's."

Landy pix:

A Class rudder foils--landyRudder-s.jpg

 
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See the dna blog http://www.dnacat.blogspot.de for more detailed information on their etnz-style foils testing. Looking at the photos I think that is not exactly the etnz approach since the s-bend in the top of the boards is missing. with the s-bend you can reduce dihedral of the foils sailing upwind (beside to the canting of the complete board). this could reduce the drag upwind, which was the major setup of the test trials by dna. Would be interesting what the experience of the paradox-guys are with the s-bending.

 
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Do the "tiplets" act like end plates at the end of the foil and reduce induced drag? This would be similar to the "winglets" you see on airplanes and I believe the practical result is that it makes the water "think" the span of the foil is longer. I also cannot figure out how you get the board up and down the trunk with that tip. Cool stuff.
The sharp radius of the J-board tips would require an enormously wide board case to fully withdraw the boards from the top. A close reading of the rule shows that the boards only need to "be capable of being fully retractable into the hull."

Rule 8.2 states: Movable and retractable hull appendages shall be inserted from the top

or be capable of being fully retractable into the hull.

From the photos it looks as though there may be a hull recess into which the tips can retract to be flush to the hull bottom. Can anyone confirm that?

If so, the boards will still need to be loaded from the bottom, similar to a moth. That would seem to somewhat defeat the intention of the rules which I believe were written to make the A-cat simple to sail off the beach, unlike the moth. Is that a good thing? :(

 

pieterjan

Member
55
6
holland
Hi Guys ,

The new J-board with wingtip can be inserted from the top, just like the standard daggerboards.

New cases have such a shape, that in combination with the tapered J-boards it works . The top and bottom slots are exactly the same as on standard boards .

The new sliders have more range, up to 4 degrees in AoA on the boards .

The whole idea is that anticipating on developments in boards, we designed a smart daggerboard case , in which a wide range of board shapes will fit : the standard 1200 mm short radius , the standard 1400 mm wide radius , the J board, but also boards like the 1300 mm radius Nikita boards and even possible S boards , so customers of new boats don't have the risk the have to refit their boat the coming years .

If the J boards -or what ever boards- are giving big advantages,don't worry too much,we plan to supply new daggerboard case kits which can be fitted in existing stanadrd daggerboard-boats reasonable easy .

Our tests with the "TNZ" foils are just for fun and to learn what works and were the bounderies are . The S on the top is missing as remarked , thats'because our "TNZ" foil was based on an existing 1400 mm radius standard daggerboard .

It felt draggy upwind, but we only spend a few hours on the water with 11/12 knts max breeze sofar .

Plenty of room to fine tune it .

As soon we test again, we will report on the blog with pics and video.

As we look at things now , we have good believe in our J boards being the best allround setup.

It is not making a whole lot of difference compared to the already very good standard configuration , but just small steps forward , learning every time a bit more .,.

Stay tuned, good sailing !

 

Lost in Translation

Super Anarchist
1,265
67
Atlanta, GA
Thanks for the report. PJD, do you have to change anything on the transoms to support the rudder vertical loads? Are the plastic clips on the DNA sufficient to keep the rudders down still?

 

dacarls

Anarchist
602
10
FL
It will be interesting to see how the ARC winglets sell for do it your selfers. Apparently, rudders fitted with them "go down" into position well. As opposed to 2013 World participant Oliver's which did not. One cannot see rudders in the posted pix, but Oliver's C-shaped wnglets were placed on the bottom of the "rather-long" rudders, requiring more leverage to get them down. Once the boat is moving much at all, there is terrific drag and it is very difficult to overcome this drag.

<- Learned in the A-cat foiling at speed in the adjacent thumbnail. Once these rudders are down, they do not have a problem staying down.

 
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pieterjan

Member
55
6
holland
Thanks for the report. PJD, do you have to change anything on the transoms to support the rudder vertical loads? Are the plastic clips on the DNA sufficient to keep the rudders down still?
The new boats are fitted with a strong SS rudder clip ( Nacra style )

for existing boats with plastic clips , these can be replaced by the stronger ones , or, as a more simple solution ; just add some spacer and pin or ring through the small hole in the rudder pintle to avoid the rudder coming up.

i'll make some pics to show some details soon .

PJ

 

Bang Zoom

Member
56
0
Canton Ma
I use a 2/1 on my rudder pull downs and if one is quick can get them down up to 10 knots. My bottom pintle is a ss bolt with a delrin washer and lock nut.

/monthly_06_2012/post-45504-070528500%201340397014_thumb.jpg

 

NZL255

Member
I'm interested in putting a set of winglets onto my rudders. One question that I would like to ask - is there a formula for positioning the winglets onto the blade?

 

juniordave nz

Member
355
1
Auckland
Yeh I thinking about it as well. Hoping it will help keep the rudders in the water downwind. Any one have any details on what they have put on, be interesting as a start point

 
Junior Dave, go and talk to the R Class boys. If they can make a 12 foot skiff foil with two on the wire the A should be a good challenge for them. Might show them the error of their ways.

 

juniordave nz

Member
355
1
Auckland
They've already worked on a foiling A http://www.trademe.co.nz/motors/boats-marine/yachts-sail-boats/small-sailboats/auction-551342134.htm, no where near class legal though.

Yeh I might have a chat to Dan next time I see him and see what foil sections he's been using.

Question (thoughts), I could put the winglets at the bottom of the rudder and that would mean I get a little end plate effect and would mean that downwind it stays in the water for as long as pos when the nose digs in, but on the other hand will add extra drag when going up wind. So I could put the winglets near the middle of the rudder and that would keep them out of the water up wind (on windward rudder any way).

Have any thoughts on position?

 

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