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Re: any updates on new 20 ft cat designs -classes [Re: Wouter] #97974
09/12/07 06:15 AM
09/12/07 06:15 AM
Joined: Sep 2007
Posts: 33
Hong Kong, NYC, NZ
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Hong Kong, NYC, NZ
Ahh Wouter, we bow to thee and your onimpotent knowledge of all....what happened to sanity and admitting that some posts in the other groups might actually be true?
Q

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Re: any updates on new 20 ft cat designs -classes [Re: Wouter] #97975
09/14/07 07:12 PM
09/14/07 07:12 PM
Joined: Sep 2006
Posts: 613
New Hampshire, USA
windswept Offline
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New Hampshire, USA
Wouter,

You just do not let up do you?


Tom Siders
A-Cat USA-79
Tornado US775
Re: any updates on new 20 ft cat designs -classes [Re: windswept] #97976
09/19/07 03:50 PM
09/19/07 03:50 PM
Joined: Dec 2001
Posts: 5,590
Naples, FL
waterbug_wpb Offline
Carpal Tunnel
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Naples, FL
Since we're on designs, I saw the picture of that C class cat with foils..

Why are the foils so far back (the forward foils). And why are the rudder foils that far back as well?

Couldn't they move all of that forward instead of having those bows tilt so far upward?


Jay

Re: any updates on new 20 ft cat designs -classes [Re: waterbug_wpb] #97977
09/19/07 04:32 PM
09/19/07 04:32 PM
Joined: May 2003
Posts: 4,451
West coast of Norway
Rolf_Nilsen Offline
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West coast of Norway
You dont just want to balance the boat on the foils over the water, but balance the side forces from the rig as well. Pulling the mast back lets you push the boat harder downwind as you have more bouyancy forward. Hence you want the rig pretty far aft.

Re: any updates on new 20 ft cat designs -classes [Re: Rolf_Nilsen] #97978
09/20/07 10:55 AM
09/20/07 10:55 AM
Joined: Dec 2001
Posts: 5,590
Naples, FL
waterbug_wpb Offline
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I see.

I must have flunked "Foil" class. Good thing I went into microbiology instead of engineering.


Jay

Re: any updates on new 20 ft cat designs -classes [Re: Rolf_Nilsen] #97979
09/21/07 10:51 AM
09/21/07 10:51 AM
Joined: Nov 2005
Posts: 96
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Carl Offline OP
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It great to see some making efforts on new designs and 20 classes . thanks so much .

Agree Rolf , what surprises me is that we still use the basic Marconi rig configuration developed 100 += years ago .

Why don't we have multihull specific rig configurations using its wide platform and more advanced tech we see in boardsails ie . carbon fibre masts with a huge range of shapes placed on more aft raked adjustable rig configurations .

With the exception of expensive fragile C Class wings there has been relatively little progress .

Cognito ie

http://www.youtube.com/watch?v=JGihC_0eC1w

Wings aren't practical but we can make advances in rig configurations along with foils .

If I could just win the lotto I,d try to develop some ---take care --have fun

Re: any updates on new 20 ft cat designs -classes [Re: Carl] #97980
09/22/07 02:53 AM
09/22/07 02:53 AM
Joined: May 2003
Posts: 4,451
West coast of Norway
Rolf_Nilsen Offline
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Carl,

there have been lots of testing done with other rig configurations. The AYRS annals are full of them. None have been as good as the "marconi" rig upwind and downwind with spi. "Good" in this context means speed, ease of handling, reability, cost etc. etc. etc. Unless there is a significant breaktrough somewere, which I think is unlikely, I think the "marconi" rig of today will stay for a very long time. The only development I see coming is increased chord for wingmasts.

I noticed that there is a winged A-class to come very soon. It will be very interesting to see both the performance and the reaction within the A-class.. How many think it will be banned in no time? I know I do..

Re: any updates on new 20 ft cat designs -classes [Re: Rolf_Nilsen] #97981
09/22/07 01:02 PM
09/22/07 01:02 PM
Joined: Nov 2005
Posts: 96
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Carl Offline OP
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Thanks for the info Rolf.

I think there is room for improvement , what I tryed a while back was a one third height A frame support using the wider cat platform. A better rig might be a sailboard type sail that could be hung from the A connection and provide a wide range of full or flat shapes and rig heeling angles to help provide lift . I drew this concept out years ago but have never been able to develop the ideas .

A wing was put on an 18 sq some time ago {Wild Turkey} as you know -
http://www.catsailor.com/forums/showflat.php?Cat=0&Number=53650&an=0&page=78

I think the weight of the wing and its lesser upwind performance on an A class cat might render it uncompetative as the sailing techniques and rigs of A s are so developed nowdays.

Wings are potentially much faster downwind and can work at higher angles , Wild Turkey if set at too high an angle would just create so much power it dove or flipped , A class cats have less beam and very narrow low volume hulls , so there are the basic trade-offs .

Good to read your posts Rolf , I and many enjoy reading them . take care .

Re: any updates on new 20 ft cat designs -classes [Re: Carl] #97982
10/04/07 10:16 AM
10/04/07 10:16 AM
Joined: Oct 2007
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Erwankerauzen Offline
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Hi Everybody,

As many catsailors, I am primarily interested in high performance boats, I have been sailing A-Cat for 15 years, still involved in, but more as potential home design, home made boat.
Investigating A Cat project I realized that B-Cat is probably the best trade-off for many reasons, as long as you can find crew easily.

A-Cat main issues issues are:
1-Storage of the boat
Usually, at least in France, your A-Cat is not welcomed on a traditional Cat parking because each time you have a tempest, the old laser or Hobie 14 recklessly hooked on the ground, flies across the parking and usually land on your carbon toy. As a result to avoid insurance problems, most of sailing club avoid ACat or is is at your own risk.
So if you don't have a garden/parking to keep your boat safe on the trailor at home, you sail winsurf or F18.

2- Relative cost of carbon laminate (DIY perspective)
For a Acat you will buy 220g/ square meter laminate, which is only 30% cheaper than 440g you will use for B-Cat hulls.
and it is nearly the same amout of work.
As a benchmark just compare the M 20 price with the new Marström A Cat price.
Everything else equal, the 500g laminate used for the M20 is probably more forgiving than the 300g used for the A-cat,
and will probably last longer, which makes the M20 even cheaper if in addition, you consider both boat life's expectancy.
As a result a M 20 using foam instead of honeycomb would be perfect and probably cheaper.

Remarks about width, weight and sail area are very interesting, and to be consistent with the "aging sailor's population" argument, I woul notice that A -Cat is easy compared to F18 which is easier than Tornado.
Physical requirements for heavy , overwidth, combined with hudge sail area is out of reach for most of the over 45 sailors but former Tornado champions.
I would love to have a 140 kg F20 I could sail with a 55 kg girl friend so with a 145 kg crew fully dressed.
I would prefer a single mainsail without jib for simplicity weigh, cost and aerodynamic efficiency.
No jib means much less stress on the fore parts of the hulls, as you don't need to maintain hudge tension on your jib's leading edge, and overall lead to a lighter boat.
According to my experience with A-Cat the higher centre of sail area for uni-rig is not an issue as long as you have less parasit & induced drag and as long as the top of the sail can be twisted enough with downhaul, pre-bend and ....
Lighter boat means less sail area and less stress on the crew, especially for the spinnaker's slave.

3- The F20 Class issue.
Reference to a customized B- Class rule is probably the solutions.
In order to adress the crew weight issue, we could consider sail area combined with max weight corrector (5kg).
Lighter crew will have a smaller mainsail with lower sail center, higher aspect ration lower induced drag winward and lower max lift downwind.
According to the number of rocket scientists, engineers and PhD on sailing forums I feel confident that this issue will find a smart solution.
In addition, sailing area adjustment could be applied for old Nacra 20 or Tornado, in order to start a fleet with all existing 20.
If the 20 Class favors a not too exclusive boat concept, affordable on a $$ perspective, and not exhausting for the crew, especially if DIY solutions are developped, it could take off.
Easy to fold and unfold the boat is also part of the cost, as for ACat, overall cost is also related to storage issue, at least for some of the potential owners, and a 2 parts mast will be optimum.

If Class development is not supported by a boat factory, it could be by carbon fiber manufacterers, and by the Class Association which has a good bargaining power compared to lonely home builders.
Nothing precludes the Class Association to rise fees in order to develop a mast mould with a mast builders, and keep costs as low as possible.Todays a new Nacra F18 alloy mast is not really cheaper than a Marstrôm Tornado carbon mast??? market driving force probably?? marketing ??
The same for the crossbeam, in addition with a fixed width it is possible to create pierce-wave beams (see link:http://18ht.free.fr/Avancement/V016/Calculs/Images/ImgRDMPoutre.gif) which allow less free-board for the hulls and
hence less weight. The link does not provide a true picture of the crossbeam. It is a 100 mm circle under the mast and it moves gradually to a flat ellipse at the gunwhale, does not require dolphin-striker, and are plug in the hulls with some "conical" adjustment, so no metal, no bolt no screw, and easy to fold and unfold especially without jib.

Carbon mast and crossbeam would be available for home-build projects as long as they pay association's fees.

Look forward reading your comments, in the meantime I have to go back to my A Cat problems.

Cheers everybody

EK

Re: any updates on new 20 ft cat designs -classes [Re: Erwankerauzen] #97983
10/06/07 01:51 AM
10/06/07 01:51 AM
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Erwankerauzen,
Are there any particular numbers that you are considering other than weight.
Beam width?
SailArea?
Mast height?
I think 140kg would be achieveable with no jib for a home builder even when building from ply. However I think the jib is an assett that would be sadly missed when doing distance races or courses other than windward leeward.
Regards,
Phill


I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!

Re: any updates on new 20 ft cat designs -classes [Re: phill] #97984
10/06/07 08:43 AM
10/06/07 08:43 AM
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Erwankerauzen Offline
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Phill,
Yes, of course, I consider other number, basically customized B Class numbers:
For the sail area, as the boat is quite light,we have a virtuous circle, not too much sailing area is required and it becomes physically affordable for seniors, even in long distance race. So 21/22 square meters seems to be reasonnable for a 140 kg (310 lbs)crew, and bigger sail area for heavier crew, until 24.5 square meters for instance)
For mast height, I target something about 10.5 meters in 2 parts with the junction at the spreader level, in order to have a 6.4 meters parts + a 4 meters parts, for easy storage purpose, also it means the hound will be at 8 meters height.
For the crossbeam width B Class rules are OK, around 3.1 meters.
About the jib, I agree with your argument, but I think the heavier the boat, the more this argument holds.
Long talks with the HOBIE TIGER designer, MR J Valer have provided me another view, the lighter the boat more the relative importance of aerodynamic drag increase, and therefore a split rig (jib+ main) providing hight lift seems not optimum for light boats.
A Cat are quite fast in long distance races, as long as spinnaker is not required.

Thank you to mention that 140kg is achievable for home builders with a single main sail plan, also it is cheaper.

The basic idea is to concentrate the technology where it is most efficient ( mast for obvious reasons) and curved pierce-wave croosbeams because it will provide additional degree of freedom for hull design(ie: curved means that the middle of the crossbeam is higher than at the hull junction, so for the same freeboard the hull designer can move the rear crossbeam aft, and get the same clearance above the water.
Or lower the freeboard or a mix of both.
If the crossbeam is piercewave with an elliptical section at the hull junction( 3.5 / 1 lenght/height ratio)the drag coef can be 1/20th of the basic circle section), so you can lower the freeboard significantly and save weight, or use a cheaper technology for the same weight, or put more stuff per square meter and build longer lasting hulls.
Also no jib means fast preparation between the road trailer and the water.
In fact I seek a big A Cat for my light girl friend and me.

Cheers

Erwan

Re: any updates on new 20 ft cat designs -classes [Re: Erwankerauzen] #97985
10/06/07 09:20 AM
10/06/07 09:20 AM
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phill Offline
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Erwan,
Thankyou for your answers.
I was just wondering if there was much in the way of common ground between our ideas.

It seems like you are thinking more along the lines of the M20 type specs but a little heavier.

It will be interesting to see your project unfold.

Regards,
Phill

Last edited by phill; 10/06/07 09:21 AM.

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!

Re: any updates on new 20 ft cat designs -classes [Re: phill] #97986
10/06/07 04:47 PM
10/06/07 04:47 PM
Joined: Oct 2007
Posts: 23
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Erwankerauzen Offline
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Phill,
You are right a M 20 a with more investment in the design than in the pure construction technology. So I would prefer foam instead of honeycomb, and achieve heavier hulls in order to have a cheaper and more friendly-user boat.

It is and will be a project, nothing is scheduled unless the beam issue can be solved.
Cheers

Erwan

Re: any updates on new 20 ft cat designs -classes [Re: Erwankerauzen] #97987
10/07/07 01:07 AM
10/07/07 01:07 AM
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phill Offline
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Erwan,
I have concerns regarding the structal integrity, weight and platform rigidity of your beam design along with the increased setup time.
I am not saying it would not work because I have not tried it and would be very interested in seeing how things work out for you.
I will look at trying wings to increase righting moment without having to run a tilt trailer or increase setup time.
The wings stay on the boat and just fold up when being trailed.
I know there are many who believe what I'm planning will either not work or not be practical. But still think I can make it practical and also make it work well.
But like you I'll never know unless I give it a go.

Good luck, I hope your concept all works out.

Regards,
Phill

[Linked Image]

Attached Files
120586-BLADE20_WINGS.jpg (378 downloads)

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!

Re: any updates on new 20 ft cat designs -classes [Re: phill] #97988
10/08/07 06:20 AM
10/08/07 06:20 AM
Joined: Oct 2007
Posts: 23
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Erwankerauzen Offline
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Erwankerauzen  Offline
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Joined: Oct 2007
Posts: 23
Your remarks target the actual issue, my only benchmark is the TomCat F18 HT project.
The curved crossbeam has been engineered by Mr Guillaume Verdier who is actually in charge of Safran a racing monohull.
For the F18 HT they have not used prepeg just basic epoxy in mould abd they achieved 10 kg and it is stiff enough to avoid a dolfin-striker.
As far as I know the prototype seems very stiff. The crossbeams are plugged into conical housing on the hull's deck, a bit like for centerboard.
The max height of the hull is 46 centimeters, because crossbeam section at the deck level generate very little drag.
Their boat seems to be very stiff, but it is also a consequence of the hull's stifness.
Of course set up process will be 15 minutes longer, but the only alternative is to make the bet that your carbon platform is not at risk when you are working 600 km from your sailing club. For a Hobie 14 no brainer, but for a 20 000 + € toy, I prefer to be organized accordingly, and the cost is to unfold completly the boat for storage, I will have the same issue with a A-Cat, so 3.10M width is OK;
I think your project makes sense, the only issue is a "legal" one: If you want the same leverage and righting moment, your overall width would have to be highter than 3.10, unless you fold the leeward wing to meet max width class rules, otherwise you give up righting moment.
The next step is to find a cheap tool/ construction process in order to use prepeg&autoclave for the first crossbeams.

Cheers

EK

Re: any updates on new 20 ft cat designs -classes [Re: Erwankerauzen] #97989
10/08/07 06:50 AM
10/08/07 06:50 AM
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Posts: 1,449
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phill Offline
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Erwan,
The leeward wing folds up when you tack but you can deploy it partially if you need to put the crew on it to lift the windward hull in light air to cut the wetted surface drag.
The way the bouyancy is distributed in the vertical plane the hull shape benefits greatly from lifting the windward hull.

Please keep us / me informed, it would be great to see your system work.
Regards,
Phill


I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!

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