Should Power Assited Systems be Allowed?

RHough: Its time for me to give it rest, my preaching won't get you to see the folly of tilting against windmills. Your blind devotion to new gadgets to solve simple problems won't get me to accept powered boats in sailing races.

Catch you later my friend.

Lorsail: I think it's just as well Randy. A discussion of sailboat technology where one advocate claims another's position is "morally wrong" and that the other position is the same as advocating the use of steroids by athletes has gone way too far.
I do believe, however, that having to use such tactics speaks volumes regarding the bankruptcy of the point you advocate regardless of whether the "majority" agrees or not.

Just to clear up a couple of these late jabs before "ending" the conversation: I was going to comment on the "morals" issue, then stopped because Randy was handling it, but I see it's still not resolved. I'm not going to take one side here, I agree with Doug that the word "morals" is a little strong, usually implying VERY serious matters. I would have used a phrase like "competitive ethics", which I think was Randy's point. My guess is that Randy, much like many other people on this forum, is neither a lawyer nor an English professor, so I think the main issue with "morals" is just a matter of the language being too strong. The whole point that most people have been making is that in the sporting world, it's considered unethical---as Randy said, it's cheating---to claim to have broken an unpowered-sailing record on a powered boat. I don't see anything unreasonable about that, and I don't see Randy using unfair "tactics". All I see on his part is slight inaccuracies in his language.

For the time being, I'll hold off on several other points I've been wanting to make. All I'll say is that I don't think the discussion has accelerated to the point of being useless, because I think it started out that way. You guys continue to reason with Doug as though he's honestly ignorant of the subject or capable of thinking about it clearly. That's your business. But as far as I'm concerned, Doug has not shown any such willingness or ability, and I really don't think you'll get anywhere by treating him politely. That's just my opinion, but I think it's very important to the debate. Thanks to everyone else for respecting other people's views and trying to discuss the subject reasonably.

 

MAXISKIFF - the numbers just don't add up

Hi Lorsail,

You threw me a curve ball with ballast on Moths - and I wasn't quick enough to realise what was happening! Sorry for misunderstanding.

I quote some stability numbers below that show that MAXISKIFF is completely outclassed by conventional multis.

I go on to show that it continues to be outclassed if foils are brought into the equation.

I also show how MAXISKIFF would have to be changed to develop similar numbers by altering beam, draft and ballast ratio and show how such a boat has dimensions that are difficult to sustain.

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If the maxiskiff has foils added we are talking a different beast. It is easy then to add foils to a multi too.

So you are talking foilers - so in some ways the mono/multi question fades away. But if both are fitted with foils the multi platform will whop MAXISKIFF in its current form. As I will show below.
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THIS IS BASED ON THE ASSUMPTION THAT FOILERS CAN BE SCALED INTO LARGER BOATS SUCCESSFULLY - IT HASN'T BEEN SHOWN YET - PARTICULARLY FOR OCEAN WORK. SO IT MAY NOT BE RELEVANT AT ALL FOR EITHER MONO OR MULTI.
(I know about Williwaw - the ocean going tri on foils but it is a world away from the speeds that we are talking about here and has a very complex ladder foil system to get sufficient lift) - old (but important) technology.
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You assert that MAXISKIFF will be faster than a multi - but the numbers just don't stack up.

Once you move to a relatively slender hullform whether multi or maxiskiff the main speed producing factor is stability.

More stability means more sail and/or more power to carry full sail.

Stability is appoximately proportional to the distance between the CG (Centre of gravity) and CB (Centre of Buoyancy) - squared.

So if you double the beam of a boat - the stability goes up 4 times.

a/ MAXISKIFF can move its lead a few feet to windward. - about 10% of LOA
b/ MAXISKIFF can move its crew or water ballast to the outrigger - about 30% of LOA

The maxiskiff gets almost all its stability from its lead and its crew/water ballast. The hull and rig are just along for the ride - they make little or no contribution to stability (hull form stability slightly positive - rig slightly negative)

a/ A Cat's centre of gravity is the middle of the hull - with boat beam sitting around the 75% of LOA mark that means the Centre of Gravity for the WHOLE BOAT is 32% of LOA to windward.
b/ A Cat can move its crew or water ballast the full width of the beam to windward - 75% of LOA

This looks bad enough - but when we SQUARE the distance it is a ridiculous comparison EVEN WITHOUT TAKING INTO ACCOUNT THAT THE CATS FULL DISPLACEMENT IS GIVING YOU STABIILITY - NOT JUST KEEL AND CREW AS WITH MAXISKIFF.

So
Righting moment is proportional to
MAXISKIFF Keel - 10 squared = 100 x keel weight
MAXISKIFF outrigger ballast (water/people) - 30 squared = 900

CAT - from displacement - 32 squared = 1024 x full displacement
Cat - from outrigger ballast 75 squared = 5625

Bring foils into the scenario and the righting moment scenario is not changed - the cat will still develop the same RM numbers. The MAXISKIFF will develop the same numbers too

The only way to counter this argument is to build MAXISKIFF wider. As all moments are around A central hull, rather than the leeward hull ...
MAXISKIFF HAS TO BE TWICE AS WIDE AS THE COMPARABLE MULTIHULL TO GENERATE SIMILAR RIGHTING MOMENT NUMBERS FROM CREW OR WATER BALLAST

EVEN IF THE HULL/RIG STRUCTURE WAS WEIGHTLESS AND THE WHOLE DISPLACEMENT WAS IN THE KEEL - THE KEEL WOULD HAVE TO EXTEND 35% OF THE BOATS LOA TO WINDWARD TO MATCH THE RM OF A CAT.

(and then you would have excessive wetted surface and substantial drag from the immersed appendage)

With such a wide boat the outriggers will contact the water very easily - so you need nicely shaped hulls out there to take the high speed immersion with no dramas. Hey a trimaran.

MAXISKIFF if it can be handled will be a very fast mono - but will be outclassed by a multi.

MAXISKIFF is what monohull orthodoxy will ALLOW - it is not an optimum solution to the open question of ultimate speed on water.

And the multi will go around the course with little drame - the MAXISKIFF ...?

CAVEAT - as foilers develop into bigger sizes (again assuming the technology scales up OK) there will be new developments in hulls and rigs - maybe cat and MAXISKIFF platforms will be irrelevant to large offshore boats intended to foil most of the time.

Michael Storer
my boat page

 

Maxi Skiff

Michael, it seems that following your theory it would be physically impossible for an 11 foot Moth on foils with one crew on a rack to beat a 20' Tornado with two people on trapezes and an asymetric spinnaker set, am I right? ( Tornado has about 9 times the Moth RM and 6.7 times the SA offwind)
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I haven't looked at the numbers for either maxi skiff because none have been published that I am aware of. He was talking about moving lead ballast on-deck sliding across the whole beam of the boat.(Langman's "skiff" used a canting keel and waterballast) Bethwaite did make the comment that he had looked at the numbers and he was convinced such a boat could beat a conventional foil assisted multihull. He made no claim as to the speed of the maxi skiff type as compared to a full flying multifoiler.
I have looked at the numbers for an 18' and two smaller SDB's and all three are capable of foiling and have SCP divided by total displacement ratio's at or above 30%.But as to their potential speed I have no idea-yet.
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Maybe we should start a separate topic?

 

No - I am not comparing a non foiling boat to a foiling boat. It is a useless comparison.

If the non foiling MAXISKIFF in the form you showed is compared to a NON FOILING CAT. The cat will win. The cat has much more righting moment (RM).

If you add foils to both - the cat will still come out on top because its huge advantage in righting moment is retained.

But canting keel monohulls are slow compared to multis because of the restricted RM available from the keel

As I showed, the MAXISKIFF has to be twice as wide as a cat of the same length to develop the same sort of RM numbers from the crew/water ballast and the canting keel has only a tiny influence on stability relative to the major gains putting the same weight into a second hull.

Canting keels are irrelevant to high speed sailing. Much better like moths to have the ballast above the water.

Michael Storer

By the way - I am highly interested in the moth developments, but haven't heard about burning off tornados. Was that two boats that just happened to come together which is impressive. Was it around a course which would be astounding. Full range performance is what counts in the end. Remember the races between C-class cats, 18ft skiffs and Tornados on the harbour? And the unexpected result.

 

I'd like that.

From my quick look at Cheyenne, she has a SCP/Total Displacement of about 44%

No wonder she's fast.

 

Power ballast systems and the future

Matt, the two instances that I know about:
1) Foiler Moth vs a fleet of A Class cats-Moth won 5 of 6 races around a course.(rohanveal.com)
2) Foiler Moth vs Tornado cat downwind Moth matched Tornado speed(correction as per edit).(Phil Stevensen on SA)
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Sail Carrying Power divided by Total displacement:
1) Tornado- 60%
2) A Class - 58%
3) Foiler Moth-39%
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Bethwaite ratio
1) SCP = RM divided by distance between CLR and CE
2)Ratio=SCP/Total displacement expressed as a percentage

 

Phil said he was matching speeds with his moth against the Tornados, not definitely faster. Also a foiling boat is not comparable to a non-foiling boat, no matter how many hulls.

 

Correction

2, you're right; my mistake.
Phil said:" But no matter how you end up in races, sailing a foil Moth is something out of this world, especially when you can match speed with a spinnaker borne Tornado down wind." "...and I came in 6th out of 7 Moths."

 

And quite old too. Imagine what a new boat would be like. My point of view is that I dont object to movable ballast ; I object to using a diesel engine to move it.IMHO in a sailboat race, all the systems related to sailing the boat should be powered by wind, water, or the crew. If the practise of motorized, push-button sailing is carried to it's extreme, we will see remote controlled powerboats racing across Bass strait. (They will still be exclusively monohulls though)

 

So in principle, we are all in line except for our friend Doug, who for one or another reason cannot see the point.

It be so.

Now, thinking about this issue, is there no possibility to use the forces that are working on the keel & keelplate/strut to lift it upward, so that only little energy is required to swing the keel from board to board?

In way of foils? like ailerons of aeroplanes?

I have nothing against canters as long as no combustion engines are used for power.

That's all.

 

Do you suppose that before each tack/gybe the boat could drop the keel to the wrong side and have some sort of manual pump system hooked up to coffe grinders that would pin the keel to the leeward side, and then they could tack the boat?

 

No, not really, I thought of a way that the forward speed of the boat - which is quite substantial most of the time, can be used so that by way of a wing, aileron, the keel swings through the dead point and than will be lifted up by some kind of a foil....an idea that sprung just into my mind...maybe with some manual help, or maybe not. See the keel as a pendulum and than when it sinks by own weight to the centerline, put the foil into action so that vwery little force is required to bring it to the required angle.

Just an idea...

 

would the weight of the bulb be too much for the foil to overcome? Maybe if the boat was traveling at a fast enough rate than a trimtab on the keel strut would be sufficient to produce the required lift. The trim tab could be something like a spoiler on an aircraft wing, except it would be there to make lift more efficient. The tab would slide fore and aft into the fin, and you would be able to adjust the amount of surface area for the amount of lift you want based on the boats speed.

 

The only power assist any proper sailing yacht should have is 100% pure Corinthian spirit! ;-)

 

Your wording is better than mine, yes along that line my thoughts were running.

In such a case I do not see any objection. Than it is an advance rather than a ship driven by an auxiliary engine.....