60'+ or - 20' Ocean Racing Monofoiler Design Discussion

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This thread is for those who are seriously interested in the concept of a 60' + or - 20' Ocean Racing Monofoiler. In this first post I've included the original post from "60' Moth- A Preliminary Design Exploration". As the technology develops I'll include as much from others working on the concept as possible.One thing that could be important as time goes by and that should be part of any discussion here is FOIL ASSIST-a concept already used on some multihulls that can potentially reduce wetted surface and drag without the possible additional complications of a full flying foiler. If you're not interested in discussing the ideas and concepts that could could make this or a full flying foiler work, including methods of developing RM ,rigs, selfighting, aspects of seaworthiness etc. and /or the ramifications of a boat(s) like this on ocean racing please don't post in this thread.
If you have ideas, questions or thoughts to contribute within the subject guidelines please do!
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60' Moth-A Preliminary Detailed Design Exploration
Please read the whole thing if you're interested. I consulted with a naval architect on this and tried to be as detailed a possible. Questions and comments from those interested are encouraged.
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60' MOTH-A Preliminary Detailed Design Exploration
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I've long been convinced that the bi-foil revolution in dinghy design sparked by the Moth Foiler has potential for larger boats as well. The Out 95 guys in the UK and Sean Langman are also exploring this idea-among others. I decided to look at the numbers for a scaled up Moth just for the hell of it. I was surprised by the results.
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I) The base boat: LOA- 12.75', SA- 86 sq.ft.;weight: 60lb.hull + 150 lb. crew =210lb.s all up.
II) Scaling up:
*A) Sail Area-Since sail area varies as the square of length I squared 12.75(162.5) and squared 60(3600). Then I divided 3600 by 162.5 and multiplied the result by 86(Moth SA) . So the scaled up SA=1905sq.ft.----------------------- ****
B) Weight- Weight/displacement varies as the cube of the length. So I cubed 12.75 (2072.67) and cubed 60(216000).Then I divided 216000 by 2072.67 and multiplied the result by 210(Moth sailing weight). So the weight of the scaled up boat is 21,884 lb.'s.----------
III) Analysis/judgement calls- The most surprising thing when I was first doodling with these figures is the weight. At almost 22,000 pounds the scaled up Moth was way heavy by comparison to an ORMA 60 trimaran(12,000lb.'s) and to L'hydroptere(11,975lb.'s). But the defining characteristic of the Moth above all else is that it is a MONOHULL. So to preserve that characteristic at this length I decided that it would be important that the boat was selfrighting like any other(hopefully) 60'monohull. The "weight budget" certainly would allow that.
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So this is what I came up with after playing with the numbers for some time and running the whole thing by a friend who is a naval architect:
60' MONOFOILER-----------------------------
1)LOA-60'-------------------------------------
2) Target Beam 50'-increase from scaled up Moth; about same proportion as aeroSKIFF 14(see post#15 Peoples Foiler Thread)
3)Target SA: 2500 sq.ft.-increase from scaled up
Moth.------------------------------
4)Target Minimum all up sailing weight including 5231 lb.s on an 18' 60° canting strut: 14,731lb.'s.--------------------------------
5) Target boat weight w/o canting keel ballast:
9500lb.'s--------------------
6) Maximum additional ballast: 3771 lb.'s water ballast in a sliding tank-perhaps sliding within forward cross beam or just aft of beam. Tank is filled while over hull to limit weight of plumbing requirements. approx. dimensions: 1.5' X 6' X 6.4'. Possible fore and aft ballast sliding system .----------------------------------------
7) Weight with maximum ballast:18502lb.'s(plus 2-4 crew)
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Summary:
-LOA*60'---------------------------------------
-Beam-50'--------------------------------------
-SA 2500sq.ft.----------------------------------- -Displacement:
14,731lb.'s ; Max: 18502---
-Draft(off foils) max
18'-------------------------
30 sq.ft. main foil; 15 sq.ft rudder
foil-------*
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COMPARISONS--------------------------------
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D/L ratio- 60' Monofoiler: 30.4--------------- D/L ratio- Orma 60/L'hydroptere: 24.8------
Bruce Number-60' Monofoiler: 2.03---------
Bruce Number-ORMA Tri: 2.39--------------
Bruce Number-L'hydroptere:2.65------------
(Bruce number is the sq.rt .of SA divided by the cube root of displacement)----------- --------- For what it's worth, the following comparison is between the 60'Monofoiler and the 60'ORMA trimaran.And I consider it one of the most important comparisons of all. The ORMA trimaran is presumed to have 60% of it's displacement supported by a "banana foil", with 30% of it's weight supported by the ama while flying the main hull. For this comparison the 60'Monofoiler is presumed to be flying on just two foils. The vertical fins of neither boat are included and both sides of the foils are included:
1)Orma 60-estimated ama wetted surface 124 sq.ft; estimated foil wetted surface 32 sq.ft.(both sides) Total 156 sq.ft. Now this figure is divided into SA(3000sq.ft.) giving 19 sq.ft. of SA per sq.ft.of wetted surface.
2) 60'Monofoiler Mainfoil area(both sides): 60sq.ft..Rudder foil area(both sides) 30sq.ft.. Total is 90 sq.ft . Dividing SA(2500sq.ft.) by this figure gives 27.7 sq.ft. of SA per sq.ft. of wetted surface.
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**Notes and Design Considerations
( see below for "More notes..." including lift calculations, foil
loading and more)
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A) The number one design consideration for this boat was that it was self righting and that it would qualify as a monohull under any rule. Therefore it does not have buoyancy pods that in any way resemble or that could function like a hull-simple rectangular spaces at the maximum beam supported by carbon cross tubes. These buoyancy tanks in combination with the 18' 5000+lb. 60° canting bulb would prevent capsize and or right the boat from a knockdown. The weight in the bulb was specifically chosen to be 1.5 times what would be required to right the boat from a pitchpole. The canting keel could be explored a lot since it is relatively light for a 60 footer(5200+lb.'s). It would be ideal for it to be clear of the water when the boat is foiling-at least above 20 knots.
B) When an Orma tri fly's the main hull it does so with about 2lb. per sq.ft. of windpressure on 3000 sq.ft. of sail. The 60'Monofoiler with max ballast can sail with it's maximum SA in about the same pressure. And in lighter conditions it can ditch up to 3700+ lb.'s of water ballast facilitating relatively light air take off in an 9-12 knot wind.------------------------------
(see Righting Moment below)
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Preliminary conclusions:
It appears to me that the 60' monofoiler could be built but right at the top end of available technology.It would be likely to equal a multi of it's own size that did not use foils and appears to have more SA per sq.ft. of wetted surface than even an ORMA tri though especially in light air the ORMA would be faster since it can retract it's hydrofoil . The concept of an extremely fast selfrighting hydrofoil holds a lot of promise.
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More notes and references:
1) Righting Moment---------------------------
When off the foils the heeling arm (CE-CLR) is 43'. When on foils it is 51.75' . Hull bottom clearance to water is 10.75'. On foils max draft ,level,is 5'.
This boat is a monofoiler and as such will be sailed heeled to weather 15° at maximum righting moment.
Elements of Righting Moment:
A) rig CG is approximately at the
CE; 1460lb. @ 14.5' to weather= 21,170ft.lb.
B)canting bulb- 5,231lb.'s at 60°( 15.6') +
3' weather heel =5231 X 18.6'= 97,296 ft. lb.'s.
C)Hull 8040 X 5'to weather= 40,200ft.lb.
D)rack(deck) ballast 23' = 6' to weather
=29 X 3771= 109,359 ft. pounds
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MAXIMUM RIGHTING MOMENT= 268,025 ft. lb.'s (A+B+C+D above)
MAXIMUM PRESSURE WITH 2500sq.ft.(268,025 divided by 51.75=5179. Divide 5179 by 2500(SA) = 2.07 lb.
================================================
2) The 50' beam could be one "wing" but would probably work better as two beams supporting a fixed empty "tank" at each end for buoyancy. A small tank containing up to 3770 pounds of water will also slide across the forward beam or just behind it. For the sake of getting the boat defined as a monohull based on whatever rule the buoyancy would not look like or function like a hull while normally sailing. In the event of a knockdown it would help to right the boat. I've talked with Alex of the OUT 95 project and he says their solution(ultra narrow hull with very wide wings on a 32 footer) is legal under the rules. Exactly which rules he was referring to I'm not exacly sure.
********The hydrofoils on this 60' monofoiler are in the hull : one mounted on the daggerboard and one mounted on the rudder.They might be partially retractable in non foiling conditions. No foils on the end of the wings.The canting keel strut would be behind the daggerboard.(Like Maximus among others)
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3) The canting strut is right on the edge of feasibility. But it probably can work: its half the weight of a VO 70 bulb but half again as long.Based on the fact that the load is 81% of the load on a Vo70 the engine hp required is likely to be about 23hp(vs 29 for the Volvo).
The Volvo 70 has a max speed so far of 40.6 knots according to Sail mag-just 5 knots short of the top end(so far) of a G Class cat(100+')-same source. And ,as I understand it, they peg the keel max out in fast conditions.
The Farr design #550 Volvo 70 has a strut approximately 12-13' long with 9920 pounds in the bulb with a variable displacement from 27,558 to 30,865lb.'s. The monofoiler as stated above needs 5200+lb.'s at 18' to be self rightng.
******I don't think that the bulb/strut being offset will have too much negative effect when you consider that L'hydroptere maintains control at over 40 knots with most of the drag coming from a foil 20' to leeward using a centerline rudder. I think that it would be important on the monofoiler to figure out a way to get the canting strut and bulb out of the water over 20 knots-keeping in mind that it will probably be sailed upwind with windward heel like the Moth. The Volvo has a max cant angle of 40°, the Schock 40 and Max Z86's 55° and a 26 footer from Bethwaite 60°.
**This area would need plenty of research and testing. It is ripe for some sort of unique solution....
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4) Bruce numbers- I calculated the Bruce number for L'hydroptere from information on Sail Area given in Sail mag.. But looking at the head-on picture and using a scale ruler I'll bet they can't carry that area(3700sq.ft.) in the same pressure that an Orma tri can carry it's 3000sq. ft. The monofoiler can carry it's maximum sail area in the same pressure an Orma tri can carry it's maximum sail area. Regardless of it's actual SA for a given pressure a well designed multifoiler will be faster than the 60 monofoiler any day. But the monofoiler and ORMA even using "foil assist" will be closer.And a "conventional" multi sailing only on it's hulls(even flying the main hull with no foil assist) would be still closer in speed to the monofoiler-with the monofoiler probably having a significant edge.
**I 'm leaning toward believing that the Bruce Number or Bethwaites "SCP Divided By Total Weight Ratio" may not be good comparitive numbers when comparing an all out foiler to a "foil assist" boat like the Orma. **When you look at these Bruce Numbers you may see what I mean: Moth 1.56 ; A Class Cat 1.82 ; 49er 1.76 ; IC 1.58 . All the boats shown show a Bruce number indicating they should be faster than a Moth-and they are when it is not foiling. But when on foils the Moth beats every one of these boats. So I'm leaning toward SA/wetted surface as a possible way to compare the boats when at least one of them is a foiler. In my comparison of the 60' monofoiler to the ORMA I showed that even though the foiler was heavier it had more power applied to less wetted area than did the ORMA. Of course ,this is simplistic: it didn't take into account induced drag of the foils, the vertical fins or the wavemakng resistance of the partially submerged ORMA ama. Nonetheless, it seems like a good indicator....
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5) Foil Loading- The 60' monofoiler will have foil loadings with and with out the sliding deck ballast. For takefoff(see #5 for lift/speed calculations) it has a foil loading of 392.8 pounds per sq.ft . That is based on 80% of the total dispacement of 14731 which equals 11784 divided by 30 sq.ft.. Above 20 knots ,at some point, it will add additional ballast and have a foil loading of 493 pounds at a displacement of 18502lb.. Most foilers are designed with about 80%(or so) of the load on the forward foil and loading is calculated based on the area of one side.
****For comparision the foil loading of the ORMA tri with and estimated banana foil area of 16sq.ft. is 450lb. per sq.ft. at a displacement of .6 X 12000=7200. A Rave foiler sailing in 2lb. of pressure has a mainfoil(2) loading of 356lb. per sq. ft. (develops RM using the foils increasing loading well past this number at max pressure). A Moth has a mainfoil loading of 169 lb.per sq.ft.-and only changes with different crew weight. And the first two person monofoiler to fly-David Lugg's I14 had an approx. mainfoil loading of over 500 pounds per sq.ft. (small "high speed" foils), if I remember correctly.
L'hydroptere has surface piercing foils and basically starts out with low loading and high wetted surface(56 sq.ft.est.) and ends up with high loading and low wetted surface(14 sq.ft.est.). The picture of L'hydroptere in Sail shows it sailing on one of two main foils at an area I estimate to be 7 sq.ft. for a loading of 1368lb per sq.ft.(.8 X 11975 divided by 7). I'm guestimating that that picture was taken when the boat momentarily flew a foil and that a more realistic loading would be based on 14 sq.ft.(7sq. ft. per main foil) for a realistic loading of 684 lb.'s per sq.ft. At takeoff with 56 sq. ft. of foil area loading is 171lb.sq. ft. but the loading rapidly increases whereas it does not change on a monofoiler unless ballast is added.
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Additional Notes: Using this formula for lift: Area=Weight divided by(the factor 2.09 X speed in mph² X Cl(coeficient of lift) along with my copy of Theory of Wing Sections and the information there on the 63412 section(p522 &523) I came up with the following for the monofoiler:
Light displacement =14731 .8=11784------
Heavy Displacement=18502 X .8=
14802--
Mainfoil area 30 sq.ft.--------------------------
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1) The boat will lift off at a boat speed of 12 mph(10.4 knots) with a CL of 1.3. This is outside the drag bucket(but way below stall) but ,of course ,as soon as the boat lifts off it will accelerate.Moths, using this foil, lift off at even higher CL's.--------------------------------
2) At a boat speed of 16mph(13.9 knots) the CL drops to .73-just inside the "drag bucket" for this foil.-----------------------------
3)At 23 mph(20 knots) after the additional ballast is added the CL is .44-well within the drag bucket. The additional ballast may not all be added at once but I checked it at the minimum speed for which some ballast would be added.
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A personal note: I'm not at all convinced that sailing foilers are a good idea for ocean racing until the electronic systems are developed to spot partially submerged objects in time to avoid them. L'hydroptere was stopped by just this kind of thing. I think all high performance boats would benefit from this kind of equipment and I imagine it's not too far away or may be already available for all I know. Equipment like that would make a venture like this much more attractive to potential sponsors...
__________________

The stage is set- with the dominance of canting keel boats in the 2006 Sydney-Hobart- to see the next level of technology brought into monohull ocean racing development: canting systems combined with on-deck movable ballast and hydrofoils. It's
going to bring monohulls right up to multihull speed-just a matter of time...

[Chris Ostlind]

Originally Posted by Doug Lord

... to see the next level of technology brought into monohull ocean racing development: canting systems combined with on-deck movable ballast and hydrofoils. It's going to bring monohulls right up to multihull speed-just a matter of time...

And Doug... will that new stuff be handled by yet another constantly running, internal combustion engine or will the existing engine just get bigger to handle the extra hydraulic load? Will mid-flight, helicopter refueling be a part of the new, Around the World, boats with these systems? I can't see skippers being willing to accept the additional weight penalties of all that extra fuel. Check that... they already do accept the extra weight. How lazy of me to overlook that fact.

Frankly, I find it amusing that the process of adding yet more weight to a boat is the answer to making it, potentially, go as fast as a type of boat that is all about its inherent lightness. Old Man Herreshoff has got to be doing the Funky Chicken in his box right about now.

There's a little known, technology shortcut if "getting up to Multihull Speed" is really what you are shooting for... It's called a propeller. Wonderful new invention, sure to sweep the boating world as the coming revolution... Then, of course, there's the Hunt for Red October technology, the Caterpillar Drive, which has apparently slipped below the monohull design radar for the moment. Soon enough, it'll be dressed-up as another, high tech solution, stealth technology and it too will show-up on this bi-tweaker at 60'.

The issue is said rather effectively in this quote, "Simplicate, then add lightness" ... Colin Chapman, seven time Formula One Champion designer and Lotus F1 team owner.

"Just a matter of time" indeed.

Please give this topic a rest... this is nothing more than a cut and paste, Junior College art class assignment to see how many crazy hunks of accoutrement you can stick on a totally bewildered sailing craft and say it will work effectively. Something akin to dressing-up a cow in a plastic horsehead and saddle and riding it in a rodeo as a horse.

Please, buddy, do you not have better stuff to do?

The potential with a well designed ocean going monofoiler is for high speed-at least equivalent to an ORMA tri in foiling conditions-with the added benefit of being self-righting.
The propensity of some multihulls to pitchpole should be virtually eliminated with a good monofoiler design.
A monofoiler is not the only modern high speed vessel to rely on ballast-see the Spitfire thread under "Multihulls" and note that ORMA tri's utilize or are allowed to utilize(by the class rule)
water ballast. Modern applications of movable ballast have barely been tried-canting keels are just one form. In fact, while a few desgners have considered on-deck movable ballast the last boat to utilize it was a long time ago(as far as I know ); one of (a) Herreshoff's favorite boats as I recall.
I'm putting my money and effort into exploring this system which I have used on several rc boats and I will incorporate the canting keel/on-deck system into my experimental X18T. This combination allows awesome power to carry sail with very high speed potential. This technology can be applied in such a way that even on the 18 the ballast is moved electrically allowing disabled,older or infirm people to sail safely at speeds not possible now.
The 60' monofoiler above uses a combination of canting keel and movable water ballast to develop extraordinary righting moment. Smaller and larger versions of this type of monofoiler will benefit greatly from this innovative application of movable ballast-without it they could not perform...

[Chris Ostlind]

Originally Posted by Doug Lord

This technology can be applied in such a way that even on the 18 the ballast is moved electrically allowing disabled,older or infirm people to sail safely at speeds not possible now.

So, tell us, Doug... What does an older, infirm, disabled person do when a plastic bag gets snagged on the foils as it did to Rohan Veal at the last World Championship for Mothies?

Do they just slither over the side with the boat inverted and dust-off the foils so they can get going again at those claimed amazing speeds?

Nope, they have to bring that bad boy back down to the surface, drag all the underwater forms back to the dock at a great speed penalty and get a handy young person down there to help them out. Then and only then, will they be able to continue in their quest to be the quickest wheelchair granny on the planet.

Since you have lots of old people in Florida, why not get your butt out and about to many of the senior citizen developments and put the full evidence on the table for the gathered old folks? Let's hear their take on the possibilities of spending a good chunk of their retirement funds on a complicated pile of stuff that will continue to give them fits.

Doug, my friend, you have totally missed the mark.... once again. Though it is your money.... Money? You've always moaned about not having any money.

Mr. Ostlind, I'm afraid you're incorrect. Here is an expert opinion by a designer of hydrofoils:
(From "Moth on Foils" post 194)

Originally Posted by Rick Loheed

Not all foil proponents for a particular purpose are 'rabid', but there are many specific applications that work, and work well with foils despite the danger of impacts with objects. Most of todays 'wave piercing' catamarans have foils and other effectors simply for motion control in case you weren't aware of it.
I actually prefer SES vessels for high speed ferries partially because they don't have much in the water and have one of the highest transport efficiencies, but it's a bit hard to do with a sailboat- although we have pictures of a Norwegian built Cirrus 120P with a spinnaker- a long story in itself!

Any boat hitting a deadhead or other hard object in the water at high speed is bound to suffer damage, particularly to props and rudders and other such appendages. I applaud the efforts of the Moth sailors and the I14 sailors, as well as Doug's continued work despite the harsh criticisms, which I think have gone into the realm of 'rabid' if anything has. Experimental work in general has a tendency to be not very forgiving, we must learn from results of the experiments or they wouldn't be called 'experimental'- and many may fail entirely if we don't do adequate homework first. During my years at the 'Rocket Labs' (TSPC, or now the Maurice J. Zucrow Laboratories at Purdue) there were many, many movies of failed rocket motor firings over the years- in fact, most of them failed in the '40's, '50's and '60's due to attempts to achieve high pressure and develop cooling methods that worked.

Centerboards, keels and a rudders are also 'hydrofoils', and as you've pointed out already are susceptible to debris as well, the odds might be slightly in their favor since they are mostly vertical other than when heeled, but only slightly with currents swaying weeds and kelp to and fro.

After 5 years of operating our hybrid hydrofoil testcraft with both 'regular' foils and lifting bodies, I will admit we hit objects twice. We are in the Chesapeake- once it was a crab pot line in the channel where they are not supposed to be (which only slowed us from 32 Knots down to around 22 before breaking the line) and once in grass we accidentally strayed into, which thankfully only arrested the boat and caused it to 'land' without damage. Something hard would not have been so kind, but luckily it never happened. Fortunately I built the foils really strong.

The vessel shown here weighs about 6 tons, is 44.5 Ft long, and has a fully computerized flight control system and a fully submerged foil system in an airplane layout like the 'monofoilers', albeit with more struts. It is roughly a 1/4 scale model of a 56M design design by Rune Odegard of Norway. Both the forward foil and the aft foil are flapped. The concept is designed to fly only a certain 'lift fraction' of the vessel, allowing the centerhull to contribute bouyancy and planing lift. This allows the craft to be scaled up slightly more than a 'conventional' all flying foiler. the math is the required foil area goes up as the square while displacement goes up as a cubic function- so there is a limit to how big you can build a fully flying hydrofoil. The 'can' on the bow is a radar height sensor.

This vessel is superior to any other 44.5 Ft boat I know of (on the Chesapeake at least) at one thing in particular- seakeeping. It is also very efficient, though this picture is with the lifting bodies, which have higher drag than conventional foils but add more lifting capacity and vertical damping like a SWATH vessel. The 1/3rd octave plot enclosed here is data acquired from this vessel in scale seas of 2-3M, or .5m-.75M (1.6-2.5 Ft) model scale. with normal foils. While this may not seem to impressive to you, in 4-5 Ft seas on a delivery voyage I could have had a cup of coffee without fear- any 45 Ft deadrise vessel would have been pitching and rolling tremendously. We thought we were in a limit sea state, athough we never even took spray on the windscreen!

But motion control systems is what we do....Sorry to inject a powerboat into the sailing forum, it's to illustrate the point that each technology has it's applications, and I think foils can live in harmony along side other sailing vessels even with the inherent weaknesses of the technology such as debris and occaisional breakage.

[Chris Ostlind]

From Doug Lord's previous post:
"... I will admit we hit objects twice. We are in the Chesapeake- once it was a crab pot line... and once in grass we accidentally strayed into, which thankfully only arrested the boat and caused it to 'land' without damage. Something hard would not have been so kind..."

Really Doug, as a former baseball player, I've just got to say thanks for the big fat hanging curveball over the middle of the plate with your last excursion into higher thought.

Not only does the guy make my argument about the issues surrounding the use of foilborne boat for , how did you say it, "allowing disabled, older or infirm people to sail safely at speeds not possible now." but you proceeded to offer not one whimper of an explanation as to how an old dude, a wheel chair dude or an infirm dude actually will get themsleves going again once they do have a mishap such as this.

You need to explain how older folks of this classification group are going to extract themselves from what amounts to a death sentence on the water if they attempt to clear the foils unaided and away from the instant help of a suitable group of knowledgable attendents. Does the responsibility fall on the Coast Guard to find the body, or what?

This is a clear demonstration of your complete lack of compassion for the elderly of this world. Man,that's pitiful... pickin' on the Grannies of this world. How low can you get?

So, answer the dilemma, Doug. Obviously, you're having trouble getting someone else to speak for your off-track idea. I couldn't imagine why anyone in their right mind would actually post a quote that actually firms-up the other guys position in the argument. Or are you going to just sit there and toss out more tired epithets?

[bobothehobo]

Originally Posted by Doug Lord

The propensity of some multihulls to pitchpole should be virtually eliminated with a good monofoiler design.
.

The propensity of some multihulls to pitchpole can be virtually eliminated with good multihull design.

Originally Posted by bobothehobo

The propensity of some multihulls to pitchpole can be virtually eliminated with good multihull design.

You're pretty much right BBTH- but most(if not all) multihulls will not selfright IF they do pitchpole(or capsize) and the monofoiler will..
That's one of the great advantages of this concept-"multihull" speed with selfrighting.

[Chris Ostlind]

What's the matter, Doug. No witty repartee on the problem of old people being able to reach down and clean their foils on this wonder boat of yours?

Can't answer CT's questions, blows smoke regarding all of Hough's questions and hasn't a clue as to how to solve a self-described problem for the elderly who he professes to serve.

Yes, I'd say you're pretty much done as a visionary, Doug. You have successfully painted yourself into a corner of your own device.

Nice.

[RHough]

Originally Posted by Doug Lord

Mr. Ostlind, I'm afraid you're incorrect. Here is an expert opinion by a designer of hydrofoils:
(From "Moth on Foils" post 194)

Originally Posted by Rick Loheed :

"This allows the craft to be scaled up slightly more than a 'conventional' all flying foiler. the math is the required foil area goes up as the square while displacement goes up as a cubic function- so there is a limit to how big you can build a fully flying hydrofoil."

Has he offered an opinion on what that limit might be?

The one he was talking about was a prelude to a 150' foiler, apparently.
Did you catch the radar altitude control system?
Beats the wand if it works in all conditions.

Interesting to find out that Hydroptere can carry 1760lb. of waterballast in each mini ama(presumably only one at a time) plus additional water ballast in her main hull.
Hydroptere is 59'LOA but 80'(!) wide giving lots of RM when the windward tank is full.
On the other hand the original conception(post #1) of the 60' bi-foil monofoiler shows ballast of 5231 lb. on a canting strut capable of clearing the waters surface at max cant as well as 3771 lbs of waterballast originally conceived of as sliding in a tank athwhartship. But apparently, Hydroptere fills it's three ballast tanks from an intake on the rudder and has sufficient power to pump forward and then out 40' to the mini ama. That MIGHT work better than the sliding tank if it was fast enough.
Also the 60' monofoiler could extend it's beam to reduce the amount of ballast required. Certainly, the new details about and the success of the Hydroptere team in early 2007 seems to show that a boat such as a 60' monofoiler is not far from being a practical to build and engineer speedboat.

[wet feet]

I can't see why the arrangement of Hydroptere would be bettered by a movable ballast monofoiler,supposing that such a machine were possible at this size.The inclined foils of Hydroptere lift themselves further out of the water at higher speeds,reducing drag,and do the reverse if immersed to greater depth by a gust.No tonnage of ballast hurtling about,no power required to move the ballast and with three lifting foils an inherently stable platform.I wonder whether the monofoil hull would exist in any class were it not for rules prohibiting other arrangements?

I don't think that a 60' monofoiler will be faster than Hydroptere; my reason for bringing it up was to illustrate that Hydroptere uses movable ballast and, apparently, has the power on board to pump it where needed. Again, Hydroptere has one extra foil than the monofoiler , ALSO uses movable ballast and has 30' more beam than the monofoiler. In my opinion, that can serve to show that the monofoiler is not too far out from a building and engineering perspective. The monofoiler would definitely be state of the art in monohulls but based on the parallels to Hydroptere I think that it could be built. In the original thread it was shown that IF it could be built it would be quite fast.
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There is no reason whatsoever that a multihull using just two foils on the main hull with buoyancy pods for sailing off the foils couldn't be very, very fast perhaps faster than Hydroptere.It would require movable ballast(which could be 100% water ballast) and it would give away the biggest advantage of a monofoiler which is being selfrighting-but would be very, very fast.
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In the Moth class the surface piercing foiler built by Brett Burvill and the first foiler Moth(I think) to win a race was no match for the bi-foiler upwind from what I've read. Reducing the number of foils from three to two has proved very fast particulary upwind and I think that a large monofoiler would be spectacular upwind as well.
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edit: I searched for the reference to a match up between Brett's Moth(surface piercing foils-three foils) and one of Johns(fully submerged foils-two foils) and couldn't find it anywhere so I wrote to Brett Burvil. His comment was that the two boats were similar in speed. He said that with his original surface piercing foil configuration (small rudder t-foil) he did 25 knots(approx) the first time out. He changed to a bit larger rudder foil for better control.
He said the boat did quite well upwind.