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

MPX Test Model

After having been inspired by my friend Michi's new 30' DSS mono's light air geny a couple of days ago and having it sort of nag at me, I hung the sail plan up in front of me yesterday so I could think about it while trying some ideas. Tonight it hit me: go with a gigantic geny* for the test model because the conditions here at this time of year are frequently very, very light 2-4mph breeze(1.7-3.5 knots) or so. I looked around at the big geny's used by the decision cats and again, my friends super fast mono, and I laid out a light air geny for this boat. See the "working" sail plan below-red line is the geny.
The way it will work is that the geny,jib or no jib as the wind warrants will simply clip on-changes less than one minute! I want power regardless of conditions and this sail does the trick for those light summer mornings.
* geny or big jib-(more like a Code Zero)-it will use a jib boom and the same sheeting system the smaller jib uses-clip on clip off-very simple sail changes! Overlap like a "real" geny is too complicated on a model like this.......

Pictures: 1) the working sail plan with the geny outlined in red, 2) the Alinghi AC cat with a geny/code zero/jib with about the same proportions as the new one of the test model, 3) my friend Michi's Quant 30 DSS(foil assist) just launched with light air geny:

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MPX Test Model

Saw the sailmaker this morning to go over the new Code Zero*. We decided to try to go with the Dimension Polyant .77oz code zero material: http://www.dimension-polyant.com/en/Spinnaker_2_6_2_Specs.php
Should be just about perfect.
Surprise,surprise. While I was there Scott asked if I'd like to see the main-I thought he was kidding but I'll be damned if he didn't have it laid out on the floor with all the panels ready for assembly. Boy, that thing looked good-going to be quite an engine! May have a picture later today......

* Code 0 The code 0 asymmetric is a tight reaching sail, the most upwind capable of the asymmetrics. The luff is as straight as possible, and the sail is flatter than other spinnakers. Due to the flatness of the code 0, it is usually made with a wire luff for strength, and of a heavier, less stretchy fabric than normal for a spinnaker. Due to the tight luff and flat cut, the code 0 can be fitted for roller furling.

 

MPX Test Model

18 years ago I designed and built the production RC foiler, the F3-it was the world's first production RC sailing foiler. The boat would take off in a 5 knot breeze. But one of the coolest things about it was that it would foil upwind-not yet possible on most foilers today except the Moth! When she'd tack she'd come real close to making it while foiling-only touching down- for less than one second and then popping up on the new tack. I've learned since that that was fantastic performance for a multihull foiler.
And what I'm hoping is that the new boat may finally complete that tack on foils! We'll see before too long...
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There are always little nitpicking things that cause delays: the .020 and .033"
dragon plate(carbon sheet) that I had for battens didn't work so I just had to order carbon rods from Goodwinds-won't be here until next Friday-drat!

 

MPX Test Model

Just a bit of trivia for America's Cup fans: if you wanted to build an exact scale model of an AC 72 the same length as the MPX test model(5'), it would have to be designed to weigh no more than 4.84lb(includes 11 crew)! In other words, it is not possible-an ultra light 5' model would be around 7-9 pounds.(the ultralight all carbon F3 model was about 7.5lb at 56"LOA)
The target weight for this exact scale model(reflecting the full size 18 footer at 750lb) is 16.688lb.

 

MPX Test Model

Since almost the begining of this project I have racked my brain to simplify the main foil by eliminating the altitude sensors(wands). I want a solution with no moving parts -one that does not have to be constantly adjusted.
I have come up with a solution that I will surely test on the model: the idea was right in front of me every time I looked at the main foil on my 16' foiler. It was designed with two dihedral tips that would break the surface, reducing lift before the foil would flyout of the water. Since the limited testing I did showed that the foil system worked(the hull didn't) AND in a few hours of foiling the main foil never broached the surface I think it worked-the control system definitely worked though somewhat sluggishly because of a bending control rod.
Nevertheless, the idea will be to test this foil for the main foil on the MPX-it may work since it is only needed in light air and for pitch control. At this point the wand system seems like it will provide more instantaneous response but the germ of an idea has been planted-and it will be tested after the current system flies.
Here is the actual main foil off the 16-I still have it-notice the outboard foil tips, and next to it the F3 main foil which is nearly identical to the MPX main foil-both with partial span wand controlled 30% flaps:

 

MPX Test Model

This is a sort of experimental "foil study" of the ama foil. The idea is to show the various immersed configurations possible with small amounts of retraction-little canting. The red line is the waterline. The hull is at the position of the yellow line. All pictures reflect an 8-10 degree angle of heel. The TNZ foil inspired this design, but if I'm right, this foil has a wider range of effective altitude control before it needs manual angle of incidence adjustment. The "V" in the TNZ foil creates a good deal of leeway-with this foil that won't be a problem because the boat has a daggerboard AND the foil can be adjusted to reduce the leeway:

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Left to right-NOTE-wind would be left to right: 1) Hull approx 4.5" above waterline, minimum altitude control, no "V",experimental for upwind, 2) Hull about 3.5" above waterline, some altitude control, little "V" probably best upwind, 3) Hull about 2.5" above waterline, maximum altitude control, maximum "V", probably best downwind. 4) rough sketch of Team New Zealand foil.

 

Come on Dougie Boy,

I've read half of this stuff over at S.A. Just get the bloody thing in the water and prove to us all that you really do know everything there is to know about foiling!!!!
B

 

Right hand picture .... foils have a nasty side effect that is handled much better by an angled wing ....

Add water and enjoy.

Them dang Ruskies! It is amazing how far ahead they were in foil technology in 1990 ....

 

MPX Test Model

Here are two shots of the just assembled stand. It's all carbon because I had the tubes left over. The stand supports the boat on the beach as it is assembled for sailing and also during first assembly of the daggerboard/mainfoil and the rudder/rudderfoil and set up of the running angles of the foils relative to the static waterline. I'll use left over line to support the hull instead of strap and will use vinyl caps on the bottom of the legs and the ends of the main tubes. More with the boat tomorrow:

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MPX Test Model

Stand still needs caps on the tube ends and maybe strap instead of line, though the line works ok. It is very light and seems rugged enough to handle the boat-as long as the sails aren't full(!).....

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MPX Test Model

Going to make a slight mod to the head of the sail. Instead of a fixed full length diagonal batten, the sailmaker will add a diagonal batten pocket so I can experiment with different batten material. Most importantly he is going to add a grommet at the "peak"(intersection of leach and head) to facilitate my experimenting with a carbon "gaff" which worked very well in all conditions on my previous RC foiler and on numerous other rc sailboats. The mast rotates and the inboard end of the gaff rotates inside the mast. The outboard end of the gaff will have an adjustment range for the peak-- basically an upper outhaul which gives tremendous control to the shaping of the upper third of the sail. It also allows the sail to not require full length battens anywhere which works particularly well on RC boats.
At least with the new setup I can experiment with the gaff and the diagonal batten....

Pictures: both the Flyer 3 trimaran(left below) and F3 foiler used rotating gaffs but of different types. The F3 gaff was vertical and curved, whereas the Flyer 3 used, in essence, a conventional gaff hidden within the white masthead floatation. Both worked well. Never needed the masthead floatation so didn't incorporate it on the F3(Flyer 3 built first). The illustration below shows the new diagonal batten pocket which will have a removable batten and the removable rotating gaff with upper outhaul.

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MPX Test Model

I mentioned in the last post about making the gaff support out of "extruded carbon" using a method I had mentioned earlier in regard to making "bent" or curved carbon wands. Thought I'd explain the method:
1) First you get a board as long as the thing you're making and as wide as it has to be for the amount of bend. In addition, this can be done in three dimensions so you build that up on the same board.
2) Second, you get a length of thick wall flexible silicone tube as long as you need it, and then build a balsa shape that will hold the tube in the shape you want, then,
3) You get something like .020" fishing wire(fairly stiff) and you bend it in half so the the half length is a bit longer than the silicone tube. Then you bend the ends of the wire over about 1" so that both ends can be pushed thru the silicone tube w/o snagging.
4) Making the part: place two nails in your building board a little further apart then the silicone tube is long. Then take 6k tow and wind it 44 times around the nails(for a 1/4" diameter solid carbon/epoxy rod). Use this same proportional density for any diameter rod. Next, take one end of the wire and pass it thru the loop made by the tow as it goes around the nails and pull it thru until the bent center of the wire is at the tow loop and you have two equal lengths of wire.
Mix the epoxy and coat the tow-make sure to saturate the tow. Pass the two wire loop ends thru the silicone tube and grip them with vice grips. Use your left hand to hold the silicone tube and use the vice grips to pull the saturated tow thru the silicone tube. The tube will squeeze out excess resin.
One you have about an inch of tow sticking out of the silicone tube remove the wire and cut the excess tow flush with the ends of the silicone tube. Then lay the silcone tube in the balsa mold you made and make sure it stays there.
When I make the wands I want the ends to be like a paddle so I'll set it up so I can compress the silicone tube so that the result is a flattened, paddle-like rod.
And thats all there is to it except cutting off the silicone tube once the epoxy cures.
--Some Notes:
1) Using the silicone tube creates an exceptional, high gloss finish.
2) If a straight tube is created w/o twisting the fibers a rod with exceptional torsional "softness) can be created: with one end fixed the other end will rotate a lot.
3) Twisting the fibers before pulling them into the silicone tube creates a torsionally stiff rod.

Picture shows a carbon handle I made for this daggerboard using this technique:

 

MPX Test Model-Final Assembly

Cleared the work table today to start the final round of assembly, starting with the full size layout of the wand and flap movement.
A short bit on the dual wands: there will be a wand on each side of the boat so that one wand is always in the water even with the boat heeling. The wand is an altitude sensor and accomplishes this by having it's lower tip held against the water by a spring. So, as the boat rises the wand changes its angle and therefore causes it's mounting axle to rotate. That causes the rockerarm and push rod to come up which raises the flap. When the flap hits neutral on a "normal" wand equipped foiler that means the boat has reached its nominal flight altitude and in neutral the flap + foil is at a +2.5 degree angle of incidence with reference to the static waterline. On this boat the flap comes up a bit more until the main foil is not producing any lift because the boat is being supported by the lee ama foil. This occurs automatically. The flap can rise to the point that it is creating downforce as well.
So, as a summary: the boat starts off floating on the main hull and the spring attached to a rocker arm on the axle holds the wand against the water. The flap starts off down at a 30 degree angle. As speed rises and the boat rises the flap approaches neutral and slightly above neutral(zero lift) and can go to negative lift. For racing applications the angle of incidence of the main foil would be shifted to zero degrees from +2.5 after the main foil is nearly unloaded-just above neutral.
The main point of having the wand/flap system is that it allows the mainhull to fly in very light air which would be impossible for this boat without it.
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So here are the elements of the final wand/ flap design for this boat:
1) flap max up: 20 degrees, max down: 30 degrees,
2) wand 16.75" long(adjustable)
3) initial designed nominal angle of heel will be 10.5 degrees( as the main foil is unloaded except for its role in pitch control)-fully adjustable,
4) Bottom of the boat 6" clear of the water(again, this is adjustable up to 11" with the adjustable wand)
5) neutral wand(cruise) is 45 degrees to the static waterline,
6) max lift wand is 27.25 degrees above neutral for takeoff,
7) zero lift wand at about 5 degrees below neutral.
8) negative lift wand begins from 5 degrees below to a max at 18 degrees below neutral.
9) when the main hull is floating, the main foil is 19.5" deep; at the intial set up of 10.5 degrees angle of heel(unloaded main foil) the foil is 12" deep below the flight waterline. At max angle of heel(nominally 17 degrees-only occuring with a fully unloaded main foil) the foil would be submerged about 7"(2.3 times the chord of the main foil-except windward tip is much closer to the surface.

Pictures-show the full size layout of the wand system and flap angle and the table cleared and ready for final assembly. Note the boat on the stand which allows everything to be double checked for fit and performance.
L to R-1) initial rough sketch of wand movement,2) final full size drawing of wand movement and flap movement(lower left),3) table set up for final assembly:
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MPX Test Model

Here are some shots of the rudder +rudder box on the retractable gantry tube. You can see the variable angle-not adjustable while sailing(at first)-the angle change of the rudder changes the angle of incidence of the rudder lifting foil. Normally set at zero degrees relative to the design waterline(not static waterline in this case). The rudder mounting box pivots on the gantry tube.
Also shown are the pieces of the wand mounting plate and, the wand axle, mounting tubes and the rockerarm that moves the push rod in response to the altitude of the main hull.

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Looking good Doug.
I see that Hobbyking are offering a new RC sailing Trimaran.
Sorry, that should read Catamaran.