Designing to Steve Clark's proposed new rules

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Phil Stevenson
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Post by Phil Stevenson » Fri Aug 04, 2006 5:34 am

Paul,
That sounds a lot like the makings of a tri-foiler, aka Brett Burville's yr 2000 "Windrush", and yr 2002 "Sideshow Bob" Moths.

My reading of the IC rules would allow it, but my reading of the IC culture is that most IC stalwarts would be against it.

My own preference is to leave the foiling to the moths.
Phil S
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
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Steve Clark
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Post by Steve Clark » Fri Aug 04, 2006 5:21 pm

Paul:
The seat has to be separate from the hull or it is part of the hull.
The seat and everything attached to the seat has to weigh less than 12 kg.
So your seat and foils would have to weigh less than 12 kg.
A pretty tall order.
Also the tips of any foils would have to be within the 4080 tip to tip beam because they would be considered part of the sliding seat and are restricted by the seat extension rule.
I guess if you engineered very well and built very carefully you could stay light enough and have something that wouldn't break very often, but I'm not sure I get the point.
RANT ON
What is so terribly wrong with the parameters as described that you have to break the box before it is even built? These are supposed to be Sailing Canoes. Not Sailboards. Not Trimarans. Not Trifoilers. I don't understand what is so bad about that or what is so hard to understand?
RANT OFF
SHC
Beatings will continue until morale improves

jimc
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Post by jimc » Fri Aug 04, 2006 8:13 pm

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"> you have to break the box before it is even built? These are supposed to be Sailing Canoes.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Its always tempting to think that you have to be in a class framework. Its really not true. Worse still if you try cramming a manifestly different concept into a class framework you risk two things. The first is that the cramming spoils your concept so that you don't even get to try your ideas out properly anyway, and the second is that the class will disapprove of your ideas and change the framework so that your boat doesn't fit it anyway.

What you've got in mind sounds like a kind of foil assisted version of Bethwaite's later HSPs. This is certainly a very interesting beast, but really its going to work best with more beam and a much bigger rig than the IC has. No reason why you shouldn't use an IC hull form for the first iteration of your prototype, but I wouldn't get stuck on the IC rule set.

People will tell you you're crazy to go down the one off boat route, but they're pretty much invariably people who haven't done it. Kinda like the non sailor who tells their kids not to take up sailing because they'll be wet, uncomfortable and sea sick. I have done a one off project, and its a rewarding experience. And at least you know the issues in the design are genuine ones, not forced on you by trying to stuff the craft into an inappropriate rule set...

Paul Scott
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Post by Paul Scott » Sat Aug 05, 2006 9:45 pm

Hey all-

I'm NOT trying to do a hydrofoil. Seattle is known mainly for 5K and under conditions. Or BIG chop when there is wind. What I'm trying to do is figure out a way to move the CE around while I'm sailing, and if a daggerboard is up while going downwind, a moving seat carraige is going to bang into it, and break something, esp if I'm trying to move everything forward to get a flat planing stern out of the water in light conditions. Or back in the water, for that matter. I'm visualizing the leeboards close to the hull, and the leeboards canted out a little so one is vertical if I'm heeled 3-5 degrees or so. The other leeboard would be up, as I reckon 2 leeboards down at the same time is way too much wetted area. A centerboard needs a lot of material for the centreboard case, and all that slot always messes up the flow, esp. when the flaps start ripping off. Jim, as much as I slobber over Franks HSP's, that's not what I want here. Ideally, I want to exploit the ability to move the CLR and CE around to match the hull and rig to sailing conditions as fluidly as possible- like Windsurfers used to. That's why leeboards look interesting, even given the problems with them at the gravity interface. Ideally, I'd also like to be able to move the leeboards for and aft, perhaps with the seat. Which is why I want to know if they would be part of the hull, or part of the seat, because if they are to be part of the hull, I might figure out a way to have them go through the inside of the hull near the sides and be legal, although if they are part of the seat that might solve a lot of problems, although weight will be an issue. I don't want an illegal boat. I'm asking what may seem naive questions so I'll know what I can do.

It does sound like the 12Kg limit on seat weight is going to obviate what I understood to be a legal seat configuration, i.e. the symmetrical seat. (?)

Paul
"Exuberance is better than good taste" -Flaubert

sfrosh
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Post by sfrosh » Sun Aug 06, 2006 1:05 am

Paul, without going into all the hydrodynamics here, there is plenty of published material indicating that leeboards are much less efficient than a daggerboard coming out of the centre (lateral) of the hull. It is mostly due to end-plate effect and non-cavitation in the normal set up.

Paul Scott
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Post by Paul Scott » Sun Aug 06, 2006 5:56 pm

sfrosh-

That said, how well does the Vortex go up wind (for any of the UK guys out there), given that as I understand it, the windward foil is for verical upwind (centreboard) lift, and the lee foil is for hydrofoil lift of the platform?

Paul
"Exuberance is better than good taste" -Flaubert

Steve Clark
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Post by Steve Clark » Sun Aug 06, 2006 11:57 pm

Paul:
Sorry for ranting.
I think I understand where you are going and wonder if it wouldn't be better to stay with a single daggerboard but link it to the seat carriage so that it moves fore and aft within an extended trunk.
It may even be possible to have the trunk do the nmajor portion of the structural work of keeping the seat connected to the boat.
The down side would be some extended gasket strips or other clever way of keeping the slot clean on the bottom. but I would bet this is still easier than dealling with two leeboards.
I saileed the Vortex before Laser started marketing them. I wasn't very impressed. A noble attempt to cross the steams, but I think Jo missed a few tricks.
SHC
Beatings will continue until morale improves

sfrosh
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Post by sfrosh » Mon Aug 07, 2006 1:00 am

Paul, I have checked out the Vortex on the web and essentially it is a narrow catamaran. The daggerboards emerge from the centre of each hull, and therefore do not constitute leeboards.
Years ago Moths in Australia had an extended daggerboard case perhaps 50% longer than the chord of the daggerboard within which sat an alloy box which could swivel about 30 degrees. The daggerboard itself moved up and down within this alloy box where it was a fairly close fit. This both moved the CLR rearward and reduced heeling effect of the rig in strong conditions.

Phil Stevenson
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Post by Phil Stevenson » Mon Aug 07, 2006 2:43 am

Paul,
I also appologise for my misinterpretaion. But in case anyone else is inspired to build seat mounted hydrofoils, be aware the two Burville Moths mentions have been hugely outdated by the present foiling moths at least partially due to the drag from surface cutting foils as mentioned by SFROSH. It was hardly necessary for the moth class to interpret the configuration as a multihull and ban it.
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

Paul Scott
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Post by Paul Scott » Mon Aug 07, 2006 4:59 pm

Steve, Phil, JimC, & sfrosh-

Some kind and thoughtful replies- I truely appreciate you guys taking the time to read my subsequent (above) post and convey your comments about my concept. Sometimes it's hard for me to express complex ideas succinctly, and it did occur to me as I wrote the origional post that hydrfoils might seem to lurk therein.... I should have posted a disclaimer there.

Paul
"Exuberance is better than good taste" -Flaubert

Paul Scott
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Post by Paul Scott » Mon Aug 07, 2006 5:13 pm

Steve (& sfrosh)-

When I have seen pics of the Vortex sailing, it seems that since the weather hull is flying a bit, and since the weather foil is the one that is providing upwind lift, that it is essentially a surface piercing foil like a leeboard, which is what lead to my question. So the daggerboard setup doesn't work as advertised? I can only imagine what the decalage interactions might be.

Paul
"Exuberance is better than good taste" -Flaubert

Paul Scott
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Post by Paul Scott » Mon Aug 07, 2006 7:17 pm

Has anybody done a horizontally sliding/rotating/retracting daggerboard in a shaped daggerboard cassett? (I don't know the official name of it.) This was done a bit in Div 1 & Div 2 boards in the late 70's, and showed some promise. The foil basically was pulled up and forward at the same time above the hull, the leading edge of the foil sliding on the front part of the case which was angled forward and radiused, the aft part of the case was vertical and the tip rotated some towards the stern under the water as the foil was retracted. The forward top sides of the foil had two dowls that stuck out the sides at right angles that slid in enclosed tracks on either side of the top of the foil, and parallel to and in or on the top deck of the hull. It did move the CE back some, gave controllable lift upwind in big winds, and didn't roll (or 'vang') the hull to windward as much as a fully immersed foil would at higher speeds. The setup also kept the top of the foil from messing with the foot of the sail as it would with the usual vertical daggerboard setup. It did require for geometrical reasons that the planform at the trailing tip of the foil to be fairly elliptical. There was one board where the foil when fully retracted lay totally exposed lying on it's leading edge on top of the board in a trench in the hull mostly forward of the slot. Although when you fell or stepped on the trailing edge of the foil sticking up in the air...... Kind of like the Finn centerboard when retracted all the way. Except more like falling on your sword than falling on your Finn's dagger.

Also,anybody know where can I look at some numbers on the drag from a long foil slot & flaps, and the drag inherent in leeboards and see if I can compare the two somehow?? The Boat Design Forum?

Paul
"Exuberance is better than good taste" -Flaubert

sfrosh
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Post by sfrosh » Tue Aug 08, 2006 1:04 am

Hi Paul, I never saw the daggerboard set up you described even though I got seriously into sailboards in 1980. Therefore I won't comment on whether it is worth the trouble. Re the Vortex, even though the basic theory of the two boards is reasonable, maybe in practice it did not perform as well as expected. The windward board is definitely developing reduced lift and more turbulence if the root is clear of the water surface. The board responsible for Lateral Resistance should be on the leeward hull. There are some good theory guys on http://boatdesign.net/forums/ to get some technical info.
In summary it strikes me that in less than fully powered conditions you want the deepest most efficient shaped board in a vertical position, on the wind. In fully powered up conditions on a new narrow DC you surely have your hands full to stay upright and maximise boat speed so you may not be able to mess very much with the board, except raise it a bit. Another option is to build another smaller high wind daggerboard.

jimc
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Post by jimc » Tue Aug 08, 2006 8:12 am

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Paul Scott</i>
The foil basically was pulled up and forward at the same time above the hull, the leading edge of the foil sliding on the front part of the case which was angled forward and radiused, <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

This was done a lot in Cherubs in the UK at the time. You willnote that I said *was* done...

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Christian AUS
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Post by Christian AUS » Sun Aug 13, 2006 1:49 pm

The Brass Monkey Regatta just happened in NSW, where we saw Phils new DC racing against current National Champion Seth Dunbar (and me when I borrowed Seths boat). In the light conditions, the still 'raw' DC cleaned up everything including some A class cats. But there were some chinks in the armour when the wind came up over 10 knots on the upwind legs.
Image

Regatta Report and Pictures: http://www.internationalcanoe.yachting. ... Page=24493

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