High Performance MPX Foil/Self-righting Trimaran-The Test Model

High Performance Self-Righting Trimaran: The Test Model

Got to this a bit just now. It is a real pain to temporarily set this thing up! I broke two of the styro notches on the port side doing it. So I just did a half mock up so I'd get some idea of the actual size of this thing. Gigantic(for a model)! No more "playing" at mock ups until I'm ready to assemble the whole thing.
The crossarms will slide down over the vertical pieces on the main hull so the crossarm/ama assembly can be removed for transport.
You probably can't tell in these pictures but the cross arms have some forward sweep.

you may get some sense of the size of the boat in these pictures-over 6' wide and 5' long( the table in the picture is 6' long) :

click on image-

 

High Performance Self-Righting Trimaran: The Test Model

For those of you just tuning in , there are numerous tests that will be completed with this model. The two with the most potential significance are:

1) Self-righting-the target is a self-righting tri in the true sense-it automatically rights from a capsize or pitchpole with no crew assist other than slacking the sheets.
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2) The MPX System. This is the temporary name for a foil system whose design was originally conceived of in this thread: http://www.boatdesign.net/forums/multihulls/mpx-11-very-small-high-power-trimaran-33686-15.html
The system uses a bi-foiler foil arrangement on the main hull-one foil on the daggerboard(with an altitude control system) and one foil on the the rudder.
Additionally, the performance version of the system includes a curved lifting foil on the ama capable of supporting 100% of the boats weight.
The system is the first such system I have seen that can allow a very wide(beam =1.22 length) small trimaran to fly the main hull in relatively light air: target 5-6 knots full size. Most wide ,small trimarans develop so much righting moment that it has to be over 15 knots for any chance of flying the main hull-this system allows the main hull to fly in light air.
The unique part of the system is that the altitude control system wand is set for a nominal flying angle of 10 degrees and as the boats speed increases the main foil loading decreases until the two main hull foils are strictly used for controling the pitch angle of the boat allowing the ama foil to support all the weight. In stronger winds and gusts the altitude control system configures the main foil to pull down for additional RM as necessary.
This system has potentially wide application if it works as well as I think it will.

Original test list:

 

High Performance Self-Righting Trimaran: The Test Model

I went to see Dr. Bradfields new Osprey multifoiler today. http://www.boatdesign.net/forums/multihulls/18-osprey-multifoiler-dr-sam-bradfield-25343.html It uses the same basic foil system as he used on the SKAT and RAVE: two main foils forward with dual independent wands and a rudder foil. Was great to see that he is almost ready to sail-starting his boat over a year before I started this project.
Matt McDonalds Falcon plant has done great work and the boat should be sailed for the first time this Friday-I will be there.
Of course this has started me thinking: what a good test of the MPX system in a race between Sam's boat and this one! Both boats weigh the same-Sams SA for the test Friday will be 300sq.ft. ,my tentative SA is 284 sq.ft.. Depending on testing Sam may go to 350 sq.ft.... Hmmm.....maybe I'll increase SA from 284 to 350???! I have the RM-for that up to 2lb per sq.ft. pressure-at least. I would race with no ballast-not as a self-righting tri. More, if I configure this boat to use crew weight max outboard and the neg lift function of the main foil. Sam's boat has a high L/B displacement main hull(mine is a wider planing hull) so he'd have an advantage in 0-5 knots wind and he may have an advantage in over 2.5lbs/sq.ft. pressure because the dual independent wands allow virtually unlimited RM.
Sounds like it could be a great race! I'll make the SA decision after model testing......

 

Thanks for the update Doug. The boat really seems to be coming along! Keep up the good work!

 

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Thanks, Raps!

 

The Osprey looks like an interesting ride.

Doug, How does the self righting feature work? With such a wide beam I would suspect the probability of capsize to be reduced... but if the boat turned turtle, the wide beam would also make it more difficult to right... right?

 

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Well, the design is intended to prevent turtling-with masthead floatation and a rig designed for the purpose. Of course, this boat is not intended for ocean cruising ,racing or sailing-just bays, lakes, intercoastal(for the singlehanded, self-righting version).
The dihedral, "curved pieces", and ama position are all elements of the system along with a lead bulb integrated into the junction of the mainfoil and daggerboard. The design philosophy is that this boat is designed as a two person boat w/o the self-righting feature and a singlehander with self-righting. The self-righting version puts the second crew in the keel bulb.....
Pitchpole is probably more likely than capsize( however, neither are very likely) and the buoyancy of the ama and the curved piece are less than the total weight-so the boat could never each a position on its side with the main hull out of the water. The combination of design elements should allow the boat to right itself but that is one of the main things I'll be testing(but not the only thing). Most people think having a keel bulb is slow-not true-especially one like this in the position its in at the juncture of the main foil and daggerboard-see the unballasted Mirabaud "bulb" below as well as the unballasted bulbs on many Moths-this one is bigger but the drag from it is fairly insignificant.

Pictures: Mirabaud "bulb" and revised(284sq.ft.) sailplan with masthead floatation.

click on image--

 

High Performance Self-Righting Trimaran: The Test Model

Pretty much have decided to make a modification to the ama/"curved piece" attachment to allow for powered up sailing with a greater than 10 degree angle of heel. Probably won't be used on the full size version of this boat-applies better to the MPX-12. Need to test it now though. More on whether I'll incorporate the pivot or not Thursday.

See the last post here: http://www.boatdesign.net/forums/multihulls/mpx-11-very-small-high-power-trimaran-33686-15.html

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UPDATE: Friday, 9-23-11--still haven't decided on incorporating the pivot attachment or not.

 

High Performance Self-Righting Trimaran: The Test Model

I've mentioned earlier about the F3 RC model that was my first multifoiler design using everything I had learned working one summer with Dr. Bradfield. He converted one of my trimaran platforms into a test model for the 40' SKAT and taught me the specific details of the foil system that he used in designing a platform like the Rave or Skat and now the fantastic Osprey(see the thread ).
Anyway, the F3 of which several were built came in between 7-8lbs. with between 1300 and 1900 sq.in. of sail. The new boat will weigh 16.8lb(with 3.8
of ballast) with between 21.4sq.ft(3081 sq. in.) and 26.37(3797 sq.in.) sq.ft. of sail area. SA/wetted surface is better on the new boat.
Wht is very interesting(and hard to believe) is that these two boats are almost the same size-in terms of length and beam.
The F3 performed like a charm on its very first sail-I can wait to see what the ballasted SRT will do! Especially since the foil systems are entirely different with the SRT(MPX) system a real breakthru if it works.
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Development Target: One of the most significant developments in foiler design may be a curved foil that uses a flap on the portion that lifts vertically(flat section at the end of the foil, probably) that can be connected to a wand surface sensor rather than a Hobie trifoiler "feeler". The aspect ratio advantages of the curved foil(Greg Ketterman) would then be able to be easily adaptable to a retracting curved foil instead of using the "feeler" surface sensors on the non retractable, all moving Hobie Trifoiler foils. If anyone comes up with a good idea how to do it I will try it on the model.........

 

CC / JJ Foil Configuration-T-foil Eliminator ?

This may be a bit of a breakthru for me since I've been trying for well over a year to eliminate the T-foil from the MPX System.
First, for any new visitors the MPX system is foil system I came up with for the MPX-12. The point of the system is to allow a wide trimaran to fly the main hull early- 5-7 knots of wind or so. Without the foil system a tri that is square or over square would not fly the main hull until at least a 15-17 knot breeze. There are many advantages to this from a high performance standpoint.
The biggest problem with the system has been the use of a t-foil to lift the main hull. Thanks to Greg Ketterman I learned how much more efficient a curved lifting foil can be than a T-foil. That is doubly true with the MPX system where the main hull can heel up to 10 degrees or so during the period from initial takeoff to 100% unloading(see earlier posts on the MPX system and the MPX -11 thread) which is approximately from 5 to 15 knots windspeed. When a t-foil is on a boat that heels to leeward it becomes very inefficient with part of the lift contributing to leeway. Now there are various ways to solve this but this new concept may be the best.
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C Foils
The idea is to use two "C" foils(curved lifting foils) arranged much differently than they have been on any boat I've seen so far(see rough sketch below).
Two C foils are used in place of a single daggerboard and lifting hydrofoil. In the sketch below the windward foil is deployed. At no time does this foil create leeway like the T-foil and it is so much more efficient that the total area(daggerboard + hydrofoil) can probably be reduced. A by-product of the C foil system is that the foils can be 100% retracted as opposed to the daggerboard/hydrofoil combination.
Downsides:
--A downside that I haven't solved yet is that the T-foil can be tied into a "wand" altitude sensor and can be set for a particular altitude. I'm working on this problem.
--Another downside is that instead of one trunk ,there will have to be two curved trunks. This may add a bit of weight unless the downsizing of the foil area makes up for all or part of that.
-- Slightly more complex but no more so than the twin boards used on most cats.
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Double J Rudder
Well, the disadvantages of a t-foil rudder follow along with those of the daggerboard/ foil. So, illustrated in the rough sketch below is a very preliminary(as is all of this) solution where two rudder's are part of one unitized rudder where each half can be raised or lowered from the cockpit allowing the most efficient rudder in the water at all times.
Downsides:
--the obvious one-more weight and a bit more complication-but, again, cats use twin rudders and this may be superior to just a single t-foil rudder.
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Note: I just came up with these configurations today. I will learn a whole lot more about them over time. It looks good but the biggest problem standing in the way of the twin C foils is having a viable ,automatic altitude control. As I said earlier I'm working on it. This-if it proves out from a design standpoint- will be tested on the SRT model and then incorporated on the full size boat. One major problem as far as the SRT goes is that there is no place for ballast. So it is highly likely that the SRT will still have to use a t-foil. But this could potentially improve the MPX-System a lot-we'll see.
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Picture: The rough sketch shows a more "normal" main hull configuration than the SRT (which is being used on a hunch and because I have it) . An altitude control system is the biggest problem with the dual C foils. But the rewards could be great so its worth pursuing. There is a lot of design latitude when using curved foils and these are only rough, preliminary sketches. For instance, the radius doesn't have to be constant. Lots of design (and building) room....

click on image-----

 

Without toooooooooo much detail in reply, why have you chosen C boards with the complication of AOA and wands etc when 2 surface piercing boards in the same position will give automatic ride height without the weight penalties.

 

High Performance Self-Righting Trimaran: The Test Model

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What I need is for the main hull main foil to lift up and down as required, automatically. A curved foil with a viable connection to a wand would do that job best but is very, very, difficult to achieve.
Because of the nature of the system, the main foils unload the faster the boat goes and can be required to develop negative(down) lift.
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And: the system is designed to maintain a set angle of heel. Surface piercing foils would change the angle of heel with speed and would not be able to automatically pull down when required.

 

I'm not going to claim I understand everything Doug has posted here; a lot of what he's into is so far outside my personal knowledge and experience that I get more than a little lost.

But I keep coming back anyway. Why? Because Doug's enthusiasm is infectious. Sometimes I enjoy hitching a free ride on the back of the trolley called "people who are totally into what they're doing".....

 

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Troy, I'm glad you stop by now and again-thanks!

 

High Performance Self-Righting Trimaran: The Test Model

Just an update: I have not yet solved the problem preventing the twin curved foils from replacing the main t-foil. For self-righting purposes the T-foil can't be replaced anyway. For a non-self-righting tri the MPX system using "J" foil rudders and twin curved main foils is absolutely ideal provided the twin curved foils can be equipped with a dual(or twin separate) wand(s). If not it won't work. My understanding of the potential benefits has led me to mind-numbing hours trying to solve the problem of adding a viable altitude control system to a curved foil while still maintaining all the benefits of a curved foil.
Serious brain pain with no real results so far.
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I've been bogged down as well with Real Life but that should ease up shortly and I'll be able to pour the coals on to get this thing knocked out. My styrofoam lady will cut curved "plugs" and a "stand" for the ama curved foil mold. This will vastly simplify the process. The daggerboard with lead ballast will be built with no mold-the main foil, rudder and rudder foil will be built from quicky molds.
The biggest pain left is the actual assembly of the crossarms to the main hull(removably) ,curved pieces and amas. Looks like the dining room table will again volunteer as the space required is so huge. The whole boat will be set up in a jig with angles, forward sweep etc controlled very precisely. Still have not made the decision on being able to rotate the ama but am leaning against it. Rotation might help performance at sailing angles from 10-20 degrees.
I'll keep in touch.....