MPX-11 Very Small High Power Trimaran

It looks like none of these things can be resolved until you build a boat as it is shown. So, why not build it now? There isn't that much money involved for a boat so small and you will discover many things.

I'm new here and if this has already been suggested, please move on. It does seem to be a good way to discover if what you are thinking can work, can actually work as planned. My friends, who are mostly kayakers and sailors, always make their own boats and modifications in order to find the magic problem solving they seek. It turns out to be the only way that has any value.

 

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Unfortunately, the design is not complete yet. When it is, a prototype may be built. The most expensive part of this little boat are the carbon cross arms, sails, mast and foils-around $5500US. It will be a fun project if it is done. I've got another project ahead of this one so it will be a while in any case.
But first and foremost the design must be worked out.
Thanks for your comments......

 

Version 4 and updates*-start 9/20/10

MPX-12--FLASH TRItm featuring the "Devils Tail(tm)" ama*


--- Version 4 specifications revised and updated from 9/20/10 on.
1. Version 1-top of page 1-estimated production specs.
2. Version 2-top of page 2-one-off specifications reflecting higher weight of the one-off boat while maintaining ratios close to version 1. Refinement of some parameters as the design has progressed.
3. Version 3-top of page 3-continued refinement.

---As stated previously IF this thing is built it will be done as a one off which means it will be heavier that the production(molded) estimate in post #1.
A small conceptual model is being built now-pictures are now posted in this thread and on this page-more to come. Work on the model has been instrumental in helping to refine the one-off design.
And,this is a hot little boat as you'll see in a while.......
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Note #1: the MPX-12 uses planing hulls because at this size displacement hulls carrying this kind of weight can't be "skinny" enough to take advantage of the low resistance characteristics of a high L/B hull-particularly with the main hull. It may be possible to use a skinny (L/B 14/1 or higher) ama hull coupled with a hydrofoil but the SA/ws ratio would be adversely affect and the boat would be slower.
--
Note#2: The MPX-12 uses two lifting hydrofoils-one on the rudder and one on the main foil. These foils are critical to the function of the boat. The system they comprise will be called the Flight Control System(FCS) and its derivation and application is detailed in the first few posts of this thread. See the following for more info:

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The Theory behind the MPX-12(based on proven performance) : (added 10/1/10)
1) The hydrofoils' principal job is pitch control. Pitch control is critical as is a well controlled heel angle for the planing ama to be effective and at the same time to be low to no drag in light air and minimal drag when planing at the most efficient planing angle which is 100% maintained by the hydrofoils(and adjustable as well).
2) The foils are designed to lift the boat off between 6 and 8 knots of boat speed-about 5 knots of wind. With the 16.5' beam without the foils the thing wouldn't fly the main hull until over 15 knots of wind or so. Most people sail in 10 or less so it is essential to have the boat perform exceedingly well in those conditions. In up to 10 knots of wind there is no need for the amas to touch the water-after that the leeward ama gradually loads up until it is carrying most of the weight. As that is happening the foils unload reducing their drag considerably. The reserve "power" of the foils is always there for pitch control. This allows the wetted surface of the main hull to disappear early and the drag of the foils to drastically diminish as speed picks up. The beam is necessary to generate the tremendous righting moment required to sail fast in a breeze.
3) A side benefit of a wand controlled main foil is that not only will it lift vertically but once the boat starts to heel beyond the "set" altitude(heel angle of 10 degrees) the wand causes the flap on the main foil to go up generating downforce(extra RM) as necessary. This allows a very wide crew range since a 120lb kid would be able to sail with the same maximum wind pressure as the heavy crew because of the extra RM from the downforce of the foil.
Response of the altitude control system is virtually instantaneous. Some of the early posts in this thread discuss other boats that use an altitude control system for VERTICAL Lift and DOWNFORCE-like the Rave and Hobie Trifoiler.
4) This system is critical for the performance of the boat-without it in light air or heavy air it would be a dog. All of it works together and is inter-related-without one part of the system the whole thing is useless.

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MPX-12 Specs

-- LOA-12' 7" - changed 9/15/10
-- LWL-12' 7" - changed 9/15/10
-- Main hull beam-5.29'- changed 9/15/10
-- Main hull beam at the waterline 3' (correction 8/7/10)
-- L/B-mainhull at waterline-4.19/1(planing hull/planing threshold: 5.3knots-1.5 SLR / 7knots-2 SLR ) (change 9/15/10)
-- Overall beam- 16.5'(15' cl ama to cl ama) updated and corrected 8/19/10--NOTE: approx the same overall Beam/overall Length as Hydroptere.(not including gantry on MPX-12)
-- LOA- ama-10
-- Ama LWL-6'
-- Ama beam- 1.5'(max and max at waterline)
-- Ama L/B- 4/1(planing hull/planing threshold-4.89 knots(aspect ratio of planing surface varies between 2/1 and 1/1)
-- Ama Buoyancy - 3.25 cu.ft/ 208lb / 53% of sailing weight / RM just due to buoyancy= 1560ft.lb.(HM in 10 knot breeze=960 ft.lb)
-- Sail Area- 163 sq.ft /23.5' mast length. Slightly taller than a scaled down A Class Cat. updated 8/19/10
-- Main foil planform area-1.6 sq.ft.updated 8/19/10
-- Daggerboard immersed planform area(boat @ 10 degrees)- 1.195 sq.ft.
-- Rudder immersed planform area(boat @ 10 degrees) - .8 sq.ft.
-- Rudder foil planform area-1.3 sq.ft.
-- Draft(max) -3.5'
-- Draft @ 10 degrees -2.39'
-- Weight-155lb all up,ready to fly minus crew updated 8/13/10(Compare with the Baigent designed "Flash Harry 19.7' by 19.7' with 190+ sq.ft on a wingmast at 150lb! Post #104 this thread)
-- Total sailing weight(displacement)- 395lb- updated and corrected 8/19/10
-- Max crew weight-240lb updated 8/7/10 ( note this gives a little wiggle room for hull weight)
-- Minimum crew weight(at max power)-120lb (boat can sail in same windstrength with minimum or maximum crew weight(!)
-- Max Mainfoil loading - 157.5 lb/sq.ft. in .3lb wind pressure @ takeoff @ 80% total load. NOTE: this is LESS mainfoil loading than a Moth with Veal(very light) updated and corrected 8/19/10---Loading DECREASES as speed increases.
-- Wand- altitude control system used in combination with the lifting hydrofoils on the daggerboard and rudder. Can be used to control sailing heel angle and compensate for different crew weights. Allows the boat to fly the main hull much earlier than it otherwise would.
-- Max Pressure/w/o reefing 1.8 lb/sq.ft( 1.8 for F18 and 18 tri) The boat should be reefed(or the sail twisted off) in these conditions to prevent potential structural damage. After testing a warning label similar to the one installed in the Rave cockpit would probably refer to max speed or max apparent wind.
-- Designed Sailing Angle- 10 degrees from 5 knot wind. Maintained by wand surface sensor in conjunction with main hydrofoil and rudder hydrofoil.
System allows hydrofoil to lift up or pull down automatically-regardless of wind(up to 1.8lb. per sq.ft) or crew weight(120-240lb.)
-- SA/WS:
a. not flying main hull-5/1
b. flying main hull-13.8/1(moth on foils=13.65/1) updated 8/4/10
-- SA/D= 47.47/1( updated 8/13/10 )
-- W/SA= 2.42 (240lb crew-better than Moth w/Veal or Payne!) (Weight/ Sail Area="sail loading"-quick and dirty comparative ratio for low resistance boats-particularly foilers. 26' Mirabaud and 11' Moth about the same)-updated 8/13/10
-- SCP/total weight*= 72.9% updated 8/13/10 -see note below
-- MAX RM-3322 ft.lb.+(37lb. foil downforce X 7.5)=3600 ft.lb. updated and corrected 8/19/10
-- MAX HM(before reefing/depowering)-3600ft.lb updated 8/13/10
Notes:
---The crew will sit on a very comfortable sliding seat with a backrest.
---The seat will slide a maximum of 2' .
---The boat will have a simple robust folding system-nothing to take apart-ready to go in 5 min.
--- See Wand above: this boat uses just two lifting hydrofoils which are critical to its operation.
---Ideas under consideration:
a. jib pivot point traveler( see bottom of page 2)
b. small "ballestron"/rotating whole rig with "ribbon square top jib"( see bottom of page 2)
c. "mini ama foils"-see post #34

These are all targets albeit very realistic targets and the potential is just flat wild.



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Change, 8/4/10: Definitely will add 2' gantry to boat. Will be adjustable in overhang and facillitate rudder hydrofoil angle of incidence change.

Change, 8/13/10: Beam to increase to 15' CL ama to cl ama, 16.5' overall all. Allows nominal 9" clearance of main hull at a 10 degree angle of heel with amas at a 10 degree cant(bottom outboard with boat vertical). RM does NOT change.

Change, 8/13/10: Boat to use gybing/canting daggerboard +mainfoil. Eliminates leeward component of hydrofoil at designed sailing angle of 10 degrees. Gybing board(F18 Capricorn and several dinghies) improves windward performance. As noted above the boat uses a sliding seat that moves a maximum of 2' and can be used to move the canting/gybing board from tack to tack(8/19/10)

Change , 9/15/10: Seven inches added to overall length. Main hull beam slightly increased.

Change , 9/19/10: Angle of cross arms changed for model and prototype. Angle of ama increased 3.6 degrees on model only(probably).This will change set angle of heel of boat as set by the wand if it is maintained for prototype.

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More Power, Much more Comfortable, Much easier to sail than ANY similarly powered up boat!

--More Power: more sail area than almost any current 12' trimaran. Much more beam and power to carry sail than any 12' trimaran-in fact more than any 12' sailboat period. The only 12' design I know of capable of automatically adding righting moment as it is needed and which maintains maximum righting moment regardless of crew weight in the range of 120 to 240 pounds. Usable power: the only 12' trimaran design that matches the numbers for the Moth in Power to Weight(W/SA) and Sail Area to Wetted Surface ratios.

--Much more comfortable: sumptuous seating with 3" cushions w/backrests-nothing like it in any current boat with this much power at this length. Seats slide easily up to 2' athwartship.

--Much easier to sail: the design of the boat limits required crew movement to 2'-no running across a tramp-just a small cockpit. No hiking or trapezing required. Much less physically demanding than any other small boat with this much sail area. Sheet leads from forward-not aft like on some cats. Amas fold for easy and quick transport. Easy to reduce sail area(or increase sail area).Daggerboard and rudder(and ama foils,if used) retract for beach launching. Weta type dolly(SC version)-the best I've seen for a small tri. Gantry(extension that holds rudder) retracts to shorten overall length.
Difficult to capsize or pitchpole but will have a simple righting system in that event. Buoyancy at masthead will prevent turning turtle.
updated 9/24/10



More later.....

*Devils Tail was from a comment by Gary Baigent in post # 40
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--*SCP(sail carrying power)= the RM in ft.lbs divided by the distance in feet between the CE and CLR.
SCP/total weight-To get Bethwaites ratio SCP is then divided by the total weight in pounds.SCP/Total Weight- A ratio of 30% or better permits upwind planing.
IMPORTANT NOTE: this ratio was mis-written and has been corrected as of 10/1/10. The word "into" was somehow substituted for the word "by" in the formula-my humble apologies!


Previous Revision of this page complete 10pm, 8/19/10 .

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Important Stats-see below

This is an update of post 19,p2 reflecting the changes to the specifications:


The changes to the boat to facilitate a one off(and on which the model is based) shown in the post above reflect a very high SA/ws and a low W/SA.
A) The Sail Area/wetted surface ratio:
--
Wetted Surface, main hull flying-------------
--
Main foil-(1.6 sq.ft. planform area)--------------3.2 sq.ft.
Rudder foil-(1.3 sq.ft planform area)------------ 2.6 sq.ft.
Vertical Fin/dggrbd(2' immersion)----------------2.39 sq.ft.
Rudder----------------------------------------1.6 sq.ft.
planing surface(ama)--------------------------2 sq.ft.
____________
TOTAL WETTED SURFACE---------------------11.79sq.ft.
MXP-11(12) SA=163sq.ft.

SA/ws= 163/11.59= 13.83/1


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Comparison to Moth:
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Main foil (planform area 1.1 sq.ft.)-------------2.2 sq.ft.
Rudder foil( planform area .88 sq.ft.)-----------1.76 sq.ft.
Vertical Fin/dggrbd(18" immersion)-------------1.17 sq.ft.
Rudder---------------------------------------1.17sq.ft.
_________
TOTAL WETTED SURFACE-------------------- 6.3 sq.ft.
Moth SA= 86 sq.ft.

SA/ws-86/6.3= 13.65/1

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B) Main foil loading(assuming that the main foil supports 80% of the weight/load). On the MPX-12 the foil lifts both up and down.

---Because of the nature of the foil system on this boat the highest foil loading occurs in the lightest air(.3lb. per sq.ft. wind pressure) at takeoff. In this case the main foil loading is 252lb. of vertical lift( 157.5 lbs. per sq.ft. main foil area).
The next highest loading is with the minimum weight crew in maximum conditions(1.8lb. per sq.ft. SA pressure) where the the load is 187 lb. down force ( 116.8 lb. per sq.ft. main foil area).
Summary:
Heavy Crew-Max vertical lift: 252lb(157.5 lbs per sq.ft.)
Lite Crew-Max downforce: 187lb( 116.8 lbs per sq.ft.)
----------------

---Comparison to a Moth(vertical lift only-main foil @ 80% only) :
Lite crew(154lb)=160 lb/per sq.ft.
Heavy crew(180lb)=178.9 lb. per sq.ft.
===========================
C) W/SA=weight in pounds divided by sail area in sq.ft.( sail loading-smaller=better )

--MPX-12=all revised:
a. Heavy=395/163= 2.42
b. Lite= 275/160= 1.69

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--Moth=
a. Heavy= 246/86= 2.86
b. Lite= 220/86 = 2.56

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Interesting A Class & C Class Cat comparisons with Moth and MPX-12--ALL WITH 175 lb* crew:
*(2 X 175lb. for C Class)

1) W/SA(weight in pounds divided by sail area in sq.ft.) smaller better :
a. Moth(66+175=241lb) 241/86= 2.8
b. A Class Cat( 150+175= 325) 325/150= 2.16
c. MPX-12( 155+175= 330) 330/163= 2.02
d. C Class Cat(approx.)-680/300= 2.27


2) SA/WS(sail area in sq.ft. divided by wetted surface in sq.ft.)
Note: A Class calculated with one board, one rudder and flying one hull. In addition 10% of its wetted surface is deducted to account for lift from the new curved boards.

A) FLYING:
a. Moth(from above) SA/ws= 13.65/1
b. A Class Cat(wetted surface=21.53 sq.ft) SA/ws= 6.96/1(corrected)
c. MPX-12(from above) SA/ws= 13.83/1
d. C Class Cat (wetted surface incl 1 board,1 rudder=35.63sq.ft./approx.) SA/ws= 8.42/1

B) NOT FLYING :
a. Moth- SA/ws= 3.51/1
b. A Class- SA/ws= 5.56/1
c. MPX-12- SA/ws= 6.17/1
d. C Class Cat(approx.)- SA/ws= 7.5/1


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*page updated and corrected 8/19/10 Updated 9/28/10,
page updated 10/8/10
----

Gino Morrelli(famed multihull designer with Morrelli and Melvin):
"Foils are definitely the way to go: it's an instant turbo".

----

click on image then again on resulting image: (rig is short rig-actual rig is taller)

 

My apologies, then. From the material you are posting here, it seemed to me that you had worked-out the design. At least it sounds that way. Since this type of boat has never been done, how do you know that the design has any merit unless you test it as a full-sized boat? That is the risk and the joy of flying off into the unknown with anything that has never before been built.

If you don't mind telling, what is the project that takes precedence over this one?

 

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No need to apologize-there are many details yet to finalize. When the design is complete I will make a decision as to whether or not I still think it is worth the investment in time and money. Right now it looks real good. A proto should be built if the design still has merit after it is complete. And it would be a very enjoyable project since, as you say, something like this has never been done before. Details first.....
The number one project for me now is this: http://www.boatdesign.net/forums/sailboats/design-challenge-trapwing-deck-ballast-12-22-a-29610.html

PS- don't hesitate to read the whole thread.....

 

MPX-12-----short rig

I was anxious to take a look at the boat with a rig on it so I borrowed one with about the right area-just about three inches shorter than the rig I'll probably go with. Also, the forward third of the actual main will come right down to the deck. The "ribbon" jib will have a boom whose pivot point is attached to a traveller molded into the deck about on the centerline. When the boat tacks the jib pivot sides over to the point that the leading edge is about on the centerline.
See post #30....

click on image and then again on resulting image:

 

MPX-12-------------wing rig

It seems to me that a boat like this would be an ideal candidate, should it be produced, for a molded 2 element wing rig. My preliminary work on a molded wing shows that it is very close to being feasible.
With the large RM and robust pitch control this little speed machine might benefit if the weight doesn't go up too much.

 

The first rig will use a square head jib which I have been experimenting with for years. I have heard rumors that a square head jib has also been tried on a Mini-now I've found a picture. The head of the jib uses a diagonal batten to support the "peak" as you see on many square top mains. Mine, on the other hand doesn't and instead has an upper gaff that supports the "throat" and the "peak" while allowing the peak to be adjusted with an "upper outhaul". The halyard is attached to the gaff about a third of the way aft and the attachment point is adjustable.

Pictures of both:

(click on mini image then click on resulting image for best clarity)

 

MPX-12-wild idea

As I've explained earlier I want a solution to the leeway possible if the daggerboard t-foil is installed on the centerline of the boat when the hydrofoil is lifting vertically. This foil will also develop negative lift(down) depending on the conditions and crew weight. In the case of negative lift there is no need for a canting board since a portion of the foil lift willl be to windward,which is good.
However, the probability is that the boat will be sailed most of the time with positive lift(up) particularly in light to moderate air.
Now this idea has a lot against it-weight and cost for two but just for the heck of it I will include it here.
The idea is to possibly have two daggerboard t-foils with only one submerged
at a time. That would allow the hydrofoil to do no harm upwind and maybe even help without having to cant the board. Which is simpler? Which would be easier to use? Which would be more effective?

 

The only time you would get negative lift is when the crew shift way forward. In waves, in my experience, but in larger platforms, you have to be at a very acute bow down angle to get negative lift - there always seems to be positive lift .... unless you're at the point of no return carrying too much sail area ... and then you're eating defecation whatever you're sailing. So you don't need the unnecessary weight, clutter and complexity of two foils, one up. the other down. And how are/were you going to seal/bed the up T board against the hull? Just more drag.

 

Mpx-12

Thanks Gary, I think you're right about the two boards. But you're not right about negative lift . This boat is designed to use negative lift in much the same way a Rave,Skat, Osprey or Trifoiler uses it. It is one of the features of the design that allows an extremely wide crew range and, further, allows a 120lb crew to sail with the same maximum RM as a 240lb crew. It is a critical feature of the design and is controlled by the wand setting not by crew weight shift-which has nothing whatsoever to do with it on this design.

 

MPX-12-board system-bingo maybe..

This is an idea that needs a bit of refinement but in essence it uses dual struts to support a single main hydrofoil. The struts are attached to each end of the foil in a pivotable manner streamlined in a "bulb" similar in appearance to the Mirabaud bulb or to the bulbs used on Moth foils ,for that matter. The struts pass thru specially designed trunks that allow free movement when the "parallelogram" structure is pivoted. And/or the "Vee" shaped upper connecting rod can slightly expand or contract. This connecting rod is pulled up to retract the foil and the center is clipped into a lock and pinned for sailing. When locked the structure will allow the foil to pivot in such a way that the foil not only lifts but adds to the windward ability of the boat by unloading the two very narrow struts. The dual wands are connected to the structure by "no-play" push pull cable.
I kind of like the idea-its not all that much more complicated that the dual kickup rudders on a catamaran. It doesn't have to be fragile if designed properly and would be easily changed tack to tack.
So, what do you think?

very rough sketch-click on image and then again on resulting image:

 

One word: Kinematics

Learn it. Know it. Live it.

 

Doug -your design is already burdened with excessive complexity, well beyond a level where you could realisticly expect to be able to build, use or maintain it. I think you need a simple solution to the leeway problem rather than additional components, movements and controls requiring input from the helmsman.

 

I disagree emphatically-that is simply not true when this boat is compared to other high performance boats. The basic functions are simple and/or automatic. Further, the design of the boat simplifies the requirements to sail the boat: drastically reducing the physical requirements including reducing the crew movement to less than that required on ANY OTHER similarly powered up boat. The comfort level of the crew is greater than on any other similarly powered up boat.

From the spec sheet: