Foiling C-Class

[TTS]

This is the S.A. link to Fed Eaton's new foiling C-Class Cat. He will try to sail it in the ICCC in September and might sail all 3 cats. http://www.sailinganarchy.com/fringe/2007/AC%20Andidote.htm

Tom

[Doug Lord]

I've written Magnus(crew) who I've known for years to see if he will send me some more detail or post it here himself-we'll see.

http://www.sailinganarchy.com/fringe/2007/images/Rocker%20in%20flight.jpg

[Munter]

Holy peoples foiler - I wouldn't want to see them ventilate the front lifting foils and pitchpole that! I image that the solid rig doesn't deal with cartwheels quite as robustly as a moth rig.

Good luck to them.

[high on carbon]

Well we're pretty careful with the boat I can say that much. That having been said it's a lot less lively than Alpha the previous boat.

With 4 foils in the water roll and pitch stability is greatly improved, as is low speed drag. So we take it easy down wind. even when we get the foils clear of the water she comes down pretty slow relative to a moth and the long buoyant bows help cushion the landing, and then we get right back up flying again. (Not to say it doesn't scare the crap out of you when it happens)

We still have a lot to learn and a lot of details to sort out about how to sail the boat near it's potential. We're very happy with our progress so far and it's a testament to Steve Killing who designed it that we had it up and flying on our first outing under power and then our first outing under sail we also go it up and flying nicely.

I've already been asked so I'll give you the basics here on design details.

4 foils in the water, all T-foils.

We extended the tubes off the transom (Our rudder gudgeons) to help extend the wheel base a little bit on the boat.

The front foils have flaps independently controlled from each hull like a prowler moth, this fundamentaly controls ride height. wands with a mechanical linkage.

We also have flaps on the rudders, linked together and adjusted by the rotation of the tiller extensions, this helps to control primary angle of attatck etc.

We fly at about 10 knots boat speed, so 6-7 knots TWS

We can easily have positiove control on the foils by our actions to give the desired effect for heeling etc.

The boat costs more than my house, 2/3's is the wing so we're cautious at times, mostly for the sake of the wing.

From here to the competition in September I will not tell you about the performance of the boat. Period. For fairly obvious reasons, so please don't ask. Nor will I get roped into any extended discussion about how to do it better etc etc. Too distracting right now and we have a development plan that we're following.

Following the race, no problem. I'll talk about all of it.

Until then I encourage you to simply come and see the boats and the racing for yourself if you're interested in very cool boats.

RCYC, spet 17th-23rd, Toronto

Cheers

H.O.C aka Blunted aka the wing man on a C-cat

[eponodyne]

I'm very curious and very interested in the 'flaps' on the rudders, I've often thought that it might be helpful to build these into centerboards to help move things to windward.

[Munter]

I might be wrong but I think the reference to flaps on the rudder was about a flap on the trailing edge of the horizontal lifting foil, not like a trim tab on a keel.

[eponodyne]

o hell, that doesn't do me any good

[yipster]

what would do good to the C class cats ( and my curiosity ) is some more publicity
sites, specs, links and the like as there is very little to google up on.
cant make it to Toronto so please keep me posted

[tspeer]

I'm very curious and very interested in the 'flaps' on the rudders, I've often thought that it might be helpful to build these into centerboards to help move things to windward.

Adding a flap to the centerboard won't move the boat to weather. It rotates the bow more off the wind because the lift on the board is dictated by the sail trim, not the board configuration. This has been covered many times on this board. Look for references to jibing boards and trim tabs.

[Doug Lord]

Check this out. Comments by Rohan Veal on his visit to Toronto AND his sailing of the C Class foiler with "Veal Heel":
www.rohanveal.com
Rohan at the helm:
c_class(2).jpg
http://www.rohanveal.com/photos/c_class/c_class(2).jpg

[Erwan]

Hi Dough, Hi High On Carbon,

I love the rear beam of your C-cat, do you you think the same kind of beam can be used with a boat with a normal rig ? (ie: a main sail with a track on the beam), or is it possible on your C-cat because there is no leech tension on the rear beam ?

Thanks

[Doug Lord]

Hi Erwan, I'm not involved with the foiling C-class presented here other than to hope they do well! I don't see why that type of beam couldn't be used if it was properly engineered for your application.

[Erwan]

Hi Doug,
Sorry I though you were in the loop according to your former comment.
More explicitly, my ideal A-Cat would have curved beams, both of them plugged more or less vertically in the hull.
The target was to reduce the freeboard area of the hulls, while maintaining beams above water especially the aft one for downwind in choppy water. (According to the news A-Cat in the pipe, it is probably a bit obsolet)

A few years ago I asked advices to a composite engineer, (He made one of the first carbon mast for A Cat in 1986).

His answer was, even if the fiber can be curved, the stress and forces involved in the beams will not necesserally follow the curve.

That is why it is a very pleasant surprise to see a C-Cat with such beams.

[Doug Lord]

Extremely interesting pix from SA: "wing tips" on a C-class wing tip:
http://www.sailinganarchy.com/forums/index.php?act=attach&type=post&id=50329
--------
Magnus, if this is your boat is the area of the tips included in the 300 sq.ft. SA?

[Retired Geek]

Doug,
this is just a 10 min quickie to show you how it changes the performance...this was set up simply with no attempt to show real performance or sailing angles...basically it provides an increase in CL, reduced CD, a better span efficiency and LD
RG

[tspeer]

I suspect you could get the the same benefits with less parasite drag by simply extending the span, but that would take you over your allowable area because the winglet does not have any projected area on the wing planform.

[Doug Lord]

The owner says the wings "were an end plate experiment gone wrong" and they won't be used in competition. Might also be disinformation...
PS RG, thanks for the sketches!

[DSmith]

What software are you using there RG?

[Retired Geek]

Its called XFLR5, and its free. Its basically XFoil with some extra's added on.
you can get it at http://xflr5.sourceforge.net/xflr5.htm
RG

[Doug Lord]

Just saw on SA that Clive Everest designer of the RS 300, 600, Tek-Kat and the hulls for Invictus is building another C-class -and a foiler at that.

[Doug Lord]

There is an excellent on-going thread about the foiling C class on SA with contributions from Magnus(blunted,Fred Eaton, Steve Clark and others. There is a photo of a foiling 18² tri designed by Dr. Sam Bradfield
looking very much like a mini hydroptere with a wing mast:
Foiling C Class - Sailing Anarchy Forums
Address:http://www.sailinganarchy.com/forums/index.php?showtopic=59168&st=100&

[Doug Lord]

Good luck to everybody but best of luck to the Foiler Dudes in the racing starting tomorrow....

[DSmith]

Its called XFLR5, and its free. Its basically XFoil with some extra's added on.
you can get it at http://xflr5.sourceforge.net/xflr5.htm
RG
Would it be able to handle multi-element wings?

[tspeer]

No. XFLR5 is basically a "2 1/2 D" code. It uses the section properties from XFOIL with a vortex lattice to get the finite span effects. It may be able to handle widely separated interacting surfaces like a board and a rudder, but it won't tell you what's going on in the boundary layer of a multi-element section.

[Doug Lord]

Canada leading with Alpha. Cogito second . Foils not a factor-all displacement sailing with relatively light wind. Foiler "Off Yer Rocker" third or fourth both days against Patient Lady VI
which I think has used "banana
boards"(foil assist).
----------
edit 9/22/07: Well, the Canadians have won with Alpha. Congratulations Fred and Magnus!

[high on carbon]

Hey gang, Magnus here.

a quick summary of the I4C event and how things shook out.

Alpha won, as you all know by now, we were able to squeeze a lot out of the boat and it returned the favour with great performance.

She has assy dagger boards in each hull which are lifted on the windward side on each tack. out rudders are a 64 series section, and as short as we felt we could make them and still be in some modicum of control at low speed.

For the heavy air day we pulled out a new set of rudders which were the same as our short ones but they had some small stabilizer winglets on them 90% of the way down the span. The winglets were about 4" out on either side if the rudder, had about 1.5" chord and were about 1/4" thick. They were set to run neutral in upwind trim. The winglets were simply designed to reduce pitching in the boat in waves, and they work quite well. The boat pitches a lot without them and with them, they added a little extra security donwhill which meant we could push harder.

We did not bother making them adjustable as it would be more weight and one more toy to distrct us in conditions that require a huge amount of focus by the crew and helm. Overall I think they worked quite well.

The foiler, Rocker, was slow, period. Being too narrow it could never get enough intial righting moment to go fast and create apperant wind. It also had basic balance issues to be sorted out, that needs a good deal more work to become as quick as a classic C. In total, Rocker simply had way more drag than Alpha, a huge amount more drag.

[high on carbon]

Hi Dough, Hi High On Carbon,

I love the rear beam of your C-cat, do you you think the same kind of beam can be used with a boat with a normal rig ? (ie: a main sail with a track on the beam), or is it possible on your C-cat because there is no leech tension on the rear beam ?

Thanks

You could try it, but you might have issues, it's really a matter of how much carbon you jam in there. we are able to build the total platform much lighter because we have no leech tension from the main being transmitted into the platform so we can go with less carbon as a result.

Word is that the old C-cats had bloody huge beams to deal with exactly this issue of major loads on the boats from the sails.

[bcv99]

Are there any new conclusions regarding the curved boards or Banana boards on PL6? Looking at the videos of ORMA 60 tris, these (little) boards they use seem to work quite well. Getting good overall performance out of the foil-borne Rocker seems to be very hard in contrast.

Is any research planned on refining this semi-flying apporach?

Anyway, congrats the Canadian team for the I4C title and one of the most exicting sailing event of this year, IMO.

Regards, Bernd

[high on carbon]

We're not pursuing banana boards right now, they were a correction for a problem with the boat in the first place, we'd prefer to have the hulls work correctly out of the box.

They are not bad but they do induce a good deal more drag then the other smaller boards.

As for reducing wetted surface, yes they do, but again at a cost of induced drag. On PL VI they are more for keeping the boat from pitch poling as much as anything.

Research, well right now we're planning on taking a breather for a while, go back to mowing the lawn, running the business etc etc.

[Doug Lord]

Here is a link to the International C Class Rules:
Canadian C Class Cats - Class Rules
http://www.cclass.ca/index.php?option=com_content&task=view&id=12&Itemid=26

[yipster]

some good info on challanger and cogito http://www.highspeedsailing.com/C%20Class%20Cat/Cclass.ppt#1

[Doug Lord]

Great article in the new Seahorse about the development of the foiler C(Rocker).

[Doug Lord]

Follow up article in the April Seahorse by Steve Killing including this:
" After a fairly carefull(close to 1 million dollars on the campaign- dl) experiment in foiling we are comfortable concluding that hydrofoils don't perform in this configuration( 4 foils-dl)on a C Class catamaran. There is no doubt that fine tuning our parameters could increase Rockers speed, but it will take more than fine tuning to make the required leap in performance. We encourage other teams to learn from our mistakes and help push foiling catamarans to the next level."