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

[Chris Ostlind]

Since engines for sailing systems (steering, sail control and righting moment) seem to be OK with some, I propose that this, so-called, necessary boat, be equipped with turbofan propulsion units on the ends of structural appendages.

I see compact, but extremely powerful enclosed units that are very much like the tail rotor setups one sees on the Coast Guard models. They'd be mounted in geared gimbaled rigs for multi-directional thrust. There would be several positioned along each side of the boat as well as a triple setup at the stern.

The power source?... Why, a dedicated diesel engine driving a fairly hefty hydraulic pump with lines run to the fans within the structural stalks, of course. The engine, itself, would be mounted in the hull in such a way as to allow fore and aft movement along a set of precision rails. That fore/aft slide system would, in turn, be set in a larger carriage allowing the whole power source to slide port and starboard.

All the engine sliding and moving motions, as well as the vectored fan systems would be controlled by a series of gyro sensors. fed through a sealed, computer which will issue instantaneous movement commands at the rate of 30 times a second from state of the art dynamic balance software that I will write in my spare time.

Doug's last minute, genius inclusion of a sliding weight on the canting keel would be further modified to include forward-looking SONAR sensors to detect the size and mass of oncoming objects. Large fish would be dealt with by rapidly deployed lances which could be set to either, slice the fish into non-threatening chunks, OR skewer said fish while the lance detaches from the keel strut and trails the fish aft on a Kevlar line for easy retrieval. It's nice to have fresh fish while sailing so fast in desolate places.

The keel bulb could be set to varying depths according to the types of fish desired, so it becomes a veritable, order as you go, fish catching system with totally unexpected potential. Imagine the spiking of a fresh swordfish or Dorado, while underway? (waters dependent, of course) As you pass the raw flesh about among the crew; Fresher, I might add, than any sushi ever eaten, the crew will rejoice with a quaff of a wonderful, perfectly chilled Chardonnay (which will be air dropped from our favorite vintner, saving the bottle weight) from their omnipresent, thermally correct, backpack and auto-sip system.

Life is good, ain't it fellas?

I'm not concerned about the weight, or the complexity of the various systems, as the boat is large, it's essentially irrelevant and we're all just wanking our way through this dream scheme anyway.

Right?

 

[Doug Lord]

Doug , i read the first post entirely , but i must say the moment i see the sailboat needs an engine to function, i lose interest. Kind of defeats the purpose, kind of like putting ballast on a flying foiler.

I think that the entire premise of a large fully flying bifoiler is pretty nebulous, and is an exercise in overcomplexity and uncontrolability.

============================
Well, I'm glad you read it. You would have noticed that the potential for this monohull is to be as fast or faster than an ORMA tri flying the main hull and sailing with foil assist. Puts the concept in pretty fast company -and that is a conservative estimate.
As to engines: almost every racing monohull 60' and up uses an engine for movable
ballast- so does Hydroptere and it seems to work well most of the time.
It doesn't bother me too much and opens up huge potential in monohull sailboats that wouldn't be possible otherwise.
The sliding bulb MAY be able to partially replace a canting keel. More experimenting will be done to see if it is worth while and determine where the shortfall from eliminating the canting keel can come from.

 

[Tcubed]

<<<<<<<As to engines: almost every racing monohull 60' and up uses an engine for movable
ballast->>>>>>>> Doug

I am aware of that and have never been happy about that development within sailboat racing. It means those boats are not wind powered . They are wind and fuel powered, a definitional change.

Yes of course the concept is guaranteed to be fast but there gets to be a point where the cost , complexity and probability of failure get too high to make the extra few knots worthwhile.

Myself, i would say since these boats already depend on an engine might as well scrap the whole rig and everything else associated with it , make the engine a little bit bigger and go fast as hell 24/7 across the oceans regardless of wind, without having to wrestle sails on spray lashed heaving deck in the middle of a pitch black night, etc. I know , i've done a lot of that stuff.

Just picture a VSV on foils effortlessly flying over the waves with a minimum engine, you get the picture.

To me the magic of sailing (and what might motivate one to endure all hardships associated with it) is killed by the necessity of an engine and fuel.

Anyways .... Don't you think a non flying foiler is a promising concept for seaworthiness and speed (and fairly simple) on the ocean?

 

[Doug Lord]

Tcubed
To get a foil to hold a multihull foiler's windward platform assembly down requires a very serious amount of negative angle of incidence, like at least 10-15 degrees and probably a lot more. Sure you'll be able to hold a windward platform area down ...... but only at a huge amount of drag increase, not worth it, spells very slow, the boat would end up crabbing and dragging along always wanting to turn up into the wind. That is only my opinion of course, someone could prove me wrong. However in early foiling days in Auckland there were a number of people who believed a 3-5 degree or so positive angle of incidence on both float/foils would lift the leeward one and hold the windward one down at the same time. Again IMO, the belief in the windward one (at near zero angle of attack) does absolutely nothing, it pops out of the water as if it is just floating there. which it is.
L'hydroptere's innovative scientists (a fairly rare species) would have done the negative thing long ago otherwise, but they have settled for windward (and after end) water ballast.

====================
Gary, Bradfields Rave and my F3 are set up with both main foils at +2.5 degrees angle of incidence and, along with Greg Kettermans Long Shot and Hobie trifoiler, have virtually unlimited RM-limited only by the structure of the
boat.
I would think that variable(effective) angle of attack(like on wand or feeler equiped fully submerged foilers) would be awfully difficult to implement on a surface piercing foiler-what do you think?
submerged foilers)

 

[Doug Lord]

Anyways .... Don't you think a non flying foiler is a promising concept for seaworthiness and speed (and fairly simple) on the ocean?

=========
Sure I do-the foil assist Ormas and G class tris and the application of the DSS
to monohulls are good examples of technology using foils to increase speed w/o fully flying.
============
PS-- T, the concept of a self-righting monohull foiler isn't limited to just 60'-it could be larger or much smaller-a Sportboat version would beat any boat its own length-mono or multi except, possibly, a very well designed multihull foiler. And engine powered ballast is not required on many versions of the concept. http://www.boatdesign.net/forums/sailboats/sportboats-design-flight-14606.html
-------
DSS foil:

 

[Gary Baigent]

"Bradfields Rave and my F3 are set up with both main foils at +2.5 degrees angle of incidence and, along with Greg Kettermans Long Shot and Hobie trifoiler, have virtually unlimited RM-limited only by the structure of the
boat.
I would think that variable (effective) angle of attack(like on wand or feeler equipped fully submerged foilers) would be awfully difficult to implement on a surface piercing foiler-what do you think?
submerged foilers)"

Doug, sure Long Shot and co have huge righting moments, as do my own boats, but that comes from the powerful lift of the leeward foil - and has nothing to do with the windward foil "hooking" (a fantasy IMO) itself into the water and holding the platform down.
Variable angle of attack surface piercers would be near impossible to design, build and implement - only my opinion though and maybe someone could do it. My preference is to forget all this wand waving stuff with deeply submerged foils and just design a decent, clean, no flaps, no draggy connection flap/foil - with an angle of incidence around 2 - 3 degrees.

 

[Doug Lord]

Gary, the max RM of the Rave(with 160lb crew) -without considering the windward foil pulling down- is about 3200 ft. lbs which is enough for about 1.4 lbs of pressure. But the boat is routinely sailed in 2lb-2.5lbs pressure. According to Dr. Sam the extra RM comes from the windward foil pulling down....
By the way, according to Bradfield the early Rave's had a warning in the cockpit that went something like this:"Do not sail in wind above 30 knots-structural failure could result." And ,in fact, that actually happened to a boat sailing in about 35 knots..-the cross arm broke.
---
wind pressure of 1.4 lbs is roughly equivalent to a wind speed of 19 mph(16.5 knots)
------------- of 2lb is roughly equivalent to a wind speed of 22.6 mph(19.6 knots)
------------- of 2.5lb is roughly equivalent to a wind speed of 25mph(21.7 knots)
=============================================
1/29/09-See the NEW R Class TV video here: http://www.boatdesign.net/forums/sailboats/new-high-performance-monofoilers-25366-6.html

 

[Gary Baigent]

Doug, I grant you there is some slowing of the lifting moment with an inverted T type windward float foil - but it is not much. The boat will hold steady if the design has both windward and leeward foils immersed (with the inverted T section rushing along it is naturally going to hold a steady grip onto water) - but it is also wanting to lift and is not going to hold the windward section of the platform down, doubtful hooking affect, sorry Doctor Sam Bradfield, this kiwi disagrees.
My two foilers have dihedral and the windward float and foil flies out of the water, only the winglet tip touches, so there is no righting moment there, but something like Long Shot with its flat or anhedral beam, will grip with its immersed L shaped windward foil. But for all round performance, such multihull foiler designs lose out badly in light airs because of extra wetted surface and drag. Same thing applies to l'hydroptere, that boat is an absolute dog in such conditions - different story however when enough wind is there for the boat to lift off.

 

[Tcubed]

The lee foil on the monohull is more like it (referring to picture few posts up), but it does not look all that efficient.

It would be interesting to see some data on the l/d polars of such high aspect planing surfaces or freely ventilating foils , however you want to call it, especially when taking into account it is operating on a highly uneven fluid interface.

Myself i would be more inclined to use a pair of fully submerged foils set at a big moment from the hull.

I return now to the question of windward foils pulling down.

Monohulls and multihulls both obtain righting moments from the same mechanism, namely disp * moment arm . Multihulls by vastly increasing the moment arm increase the righting moment per mass, and since in these boats resistance is intimately connected to displacement, create a much better thrust/resistance ratio. Canting keels are the same in that they increase the moment arm.

The above is gravity dependant method of maintaining stability. A foiler where the foils only lift is also gravity dependant, so its only advantage is that of reducing overall resistance by trading buoyant hull wetted surface resistance + hull wave making resistance + spray drag +parasitic resistance for foil wetted surface (much less) + foil wave making (very little) + induced drag (significant) + spray drag + parasitic drag. There is no increase in available thrust due to more powerful righting moments.

So this foiler is also gravity dependant, and its power to weight ratio is constrained just like the mono or multi above.

Now however if the windward foil is to provide a downward force , the weight of the machine is no longer necessary and the power to weight ratio is unbounded. Big difference.

It is true that in light winds this ceases to be an advantage because there comes a point where it is not possible to fit enough sail area on the craft in order to take advantage of this dynamic stability. At that point, it is better to revert to a gravity dependent system and indeed to remove the windward foil. In any thing stronger than that the foiler that is not gravity dependent will have an increasingly great advantage, because its only limit will be that imposed by structural considerations.

 

[Doug Lord]

60' Moth+?= AC contender?

Well there are lots of people who don't like the use of engines to move anything on racing sailboats BUT it is LEGAL for the next Americas Cup which means a version of the 60' Moth(not self-righting) could probably be designed to whup both the multihulls now getting ready for the next Cup race.
Now that would be an exciting race especially since both of them are using foil assist....and maybe movable ballast.

 

[Gary Baigent]

No doubt about a 60 foot Moth being a potent (and potentially tricky) high performance boat - but to date, I don't know of any work in this field. I mean we're not talking filthy motors to cheat are we here Doug - just an honest sail boat. However you're dreaming if you think such a design is going to be superior to the multihulls and foilers. The Moth is an outstanding thing, poetic to watch .... but actually they are not in the raw speed performance bracket of a tricked out multihull.
About stinkers - they're here because of Judge Judy not understanding sailing - but they are not going to last - the backlash is going to be savage ..... and this will be the first and last time that motors will be in AC.

 

[Doug Lord]

No doubt about a 60 foot Moth being a potent (and potentially tricky) high performance boat - but to date, I don't know of any work in this field. I mean we're not talking filthy motors to cheat are we here Doug - just an honest sail boat. However you're dreaming if you think such a design is going to be superior to the multihulls and foilers. The Moth is an outstanding thing, poetic to watch .... but actually they are not in the raw speed performance bracket of a tricked out multihull.
About stinkers - they're here because of Judge Judy not understanding sailing - but they are not going to last - the backlash is going to be savage ..... and this will be the first and last time that motors will be in AC.

---------------------------------
I think the concept is potentially faster than a "foil-assist" multihull-particularly around an AC course but not faster than a full flying multifoiler.

 

[bistros]

No doubt about a 60 foot Moth being a potent (and potentially tricky) high performance boat - but to date, I don't know of any work in this field. I mean we're not talking filthy motors to cheat are we here Doug - just an honest sail boat. However you're dreaming if you think such a design is going to be superior to the multihulls and foilers. The Moth is an outstanding thing, poetic to watch .... but actually they are not in the raw speed performance bracket of a tricked out multihull.
About stinkers - they're here because of Judge Judy not understanding sailing - but they are not going to last - the backlash is going to be savage ..... and this will be the first and last time that motors will be in AC.

I'd have to agreed with Gary. Watching the recent Moth Worlds at the Gorge it is quickly apparent that fast and finely controlled crew movement is a major component to sailing. Just as noticeable is the violence of mistakes. Broken bones, bruises and equipment failures were a big factor in results. Multiply the mass involved by a factor of ten (conservatively) to arrive at 60', and the carnage expected will reach WMD proportions.

Crashing Moths at $16-20 thousand dollars per unit is "affordable", but a 60' version would be astronomical in both money and broken bodies.

Sometimes wild theoretical ideas are better kept in the realm of theory and dreams.

I also agree with the conclusion that this will be the last diesel-belching, motorized America's Cup. I won't watch this one, and many sponsors will find out quickly that sailors as a rule appreciate the purity of wind power when racing.

--
Bill

 

[Doug Lord]

60' Moth+20 for AC

Gary, this is from our friend Hough-he doesn't believe it could be built but if it was it would be potentially faster than an Open 60 using foil assist. Note that he is referring to the self-righting version using a canting keel whereas the AC version would not be so equipped:
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Doug, I'm impressed.

I'll be the first to say when my knee jerk reaction is in error.

I still feel that SA/WSA is too simple to be of much value. Although Doug is correct that a boat with a higher SA/WSA ratio should be faster.

I took the liberty of generating some drag and power curves for Doug's 60' CKSDBMF and an ORMA 60' Trimaran. I considered both wetted surface (skin friction) drag and induced drag fom the foils on both boats. I did not consider wavemaking drag, spray drag, or foil profile drag. Both boats will probably have similar additional drag in these areas.

Bottom Line:

Doug is absolutely right. The 60'MF is potentially faster than a displacement multi-hull.

I used Doug's Figures for foil sizes and weights. The 60'MF rig ends up being about 100' tall, which just happens to be the limit for an ORMA 60.

The ORMA 60 has only a 151% advantage in Sail Carrying Power over the 60'MF

My calcs show that the 60MF should be able to lift and foil just over 10 knots of boat speed. The drag polar peaks at lift off, then goes down until the boat speed is 25 knots or so. The negative slope of the drag curve (pink) is due to fact that the CL required of the foils goes down faster than the drag due to skin friction goes up. I used an AR of 7.5:1 (15x2) for both the main foil and the rudder foil and a max CL of 1.3.

The drag curve for the Tri (blue) has a flat area from about 10 knots to 20 knots for the same reason. The foil produces the needed lift at lower CL values as speed increases.

Somewhere between 20 and 25 knots the MF has lower drag than the Tri and the MF enjoys a drag advantage at all speeds above 25.

I added a line (yellow) to show the relative drag of the two boats.

The violet line shows the 151% power advantage for the Tri.

Right about 35 knots boat speed the Power Advantage curve meets the Drag Penalty Curve and above that point the MF should be faster.

I did some basic rig efficiency calculations to get a feel for the total drag vs power available for the two boats. These curves are purple for the MF and brown for the Tri. It is interesting to note that below about 15 knots boat speed the MF has very little power to spare. From 15 to 30 knots the percentage of available power required to equal drag is almost the same, and above 35 knots the Tri has more spare power than the MF.

These very basic calculations show that at 50 knots both boats have power to spare. This cannot be true, since ORMA Tri's have not hit 50 knots. I made no attempt to estimate parasite drag for either of the boats. At boat speeds over 15 knots or so, the aerodynamic drag of the hull and rig start eating into that extra available power and in practice all the extra power seems to be used somewhere in the 40-45 knot range.

I still don't think that a 60'CKSDBMF can be built that will foil reliably if at all. However, if it could be built it has the potential to compete with ORMA 60's.

 

[Gary Baigent]

Houghy and you agree??? - holy ****! But it is theoretical stuff and yes, very impressive. Reality!!! - sorry - but sailing the MF (guess my reaction to those letters?) - and you're talking about no canter on the dreamland AC super Moth - sailing that thing would also be super tricky. But looking ahead, it is the only way to go for a monohull to catch the multi foilers. But a very dangerous thing - would get even more abuse from the rear guard than what multihulls got in the early days.