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

[Doug Lord]

MPX Test Model

Here is a shot of the daggerboard structure that will be installed along with the laminate on each half of the board. Click on the picture esp. the one with red lettering. The board will have two solid carbon rods running full length and one running two thirds the length. The rods will stick out below the bottom of the foil and be inserted and glued into the main foil in addition to other reinforcing of the mainfoil/daggerboard joint. Toward the aft end of the foil is a hollow carbon tube that will house the carbon flap pushrod for the mainfoil. Just forward of the two carbon rods is a 6/32 SS threaded rod that will attach the foil to the adjustable wand retainer(and thereby to the boat).
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[Doug Lord]

MPX Test Model

Daggerboard and two ama foils complete.
UPDATE 6/20/13:
1) daggerboard laid up-will be pulled tomorrow or Saturday.
2) Made tests today with the new resin and cabosil and with glass spheres. Both worked well but the surprise was that cabosil did not cause the resin to heat up beyond luke warm.
3) Starboard ama foil laid up! Pulled Saturday.
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UPDATE 6/21/13:
1) Port ama foil laid up-will pull Sunday or Monday.
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[Doug Lord]

MPX Test Model

This and that: what does what------

click on picture-

 

[Doug Lord]

MPX Test Model

Found the lines* of the extraordinary Victor T designed by the Gougeon Brothers and probably the fastest C Class multihull in 1969.
Quite a coincidence that the ama L/B ratio for the mpxFire Arrow is 13.14/1 and Victor T's ama is 12.8/1 ! See post 503 in the Historical Multihulls thread for some commentary at the time by Jack Knights: http://www.boatdesign.net/forums/multihulls/historical-multihulls-42019-34.html
* turns out these aren't the lines but panel layouts.L/B should still be accurate, I think.

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[Doug Lord]

MPX / SRT Test Model

Pulled the two ama foils and the daggerboard today-all are excellent! The ama foils passed a load test at over three times(50lb) their maximum load(about 14 lb) with very little deflection. This technique has worked pretty well for the curved foils-inexpensive and a quality, one piece carbon foil. I'm very happy with how well it's worked out. Small amount of finish work and then they'll be painted white(with a couple or three red stripes).

NOTE: These foils are just as they came out of the mold except the slight trimming of the inboard tip. They still need to be trimmed but came out remarkably well.
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[Doug Lord]

MPX Test Model

Preparing to trim the ama foils and cut the main foil, rudder foil and wand mount out of dragon plate carbon fiber sheet. And then all, including the rudder, will be cosmetisized and painted.
Also setting up to make the "extruded" wands themselves out of carbon tow. The process involves pulling about 40 "strings" of carbon tow thru a silicone tube after wetting the tow out with epoxy. A strong wire is put thru the loop in one end of the tow and the other ends of the wire are pushed thru the silcone tube that is the same length as the final wand. Using a pair of vice grips in one hand to hold the wires and holding the silicone tube in the other , the wet material is pulled thru, and the silicone tube is then set in a previously made mold to hold the desired shape. This can be done in three D- there are all kinds of possibilities. The water end of the wand will be shaped a bit like a paddle to allow it to plane over the surface-a design invented by Dr. Bradfield for Rave wands.
Mostly assembly after this stuff is complete.....

 

[Doug Lord]

MPX Foil System + MOD 70!

Now this is cool! Discovered it on Fred's "Foilers": some guys are considering putting foils on a Mod 70 and they are considering a system very similar to the MPX system I came up with over three years ago and am building this model to test.
http://www.microsofttranslator.com/...surf/actu/7824-Un-MOD70-a-super-foils-pour-la
They are considering a foil on the daggerboard(same as MPX) and a foil on the rudder(same as MPX) and an ama foil-either "S" or "L"(similar to the MPX system). They also add a rudder on each ama-not used in my system. So far as I know this configuration(MPX) has never been used on any trimaran in the history of mankind and I think it is really cool that some other guys have also recognized the potential of the system!
UPDATE: trying to get more info from Fred on this story-that was originally published on April 1st, 2013(!) Looks like it was an April Fools joke-even though it's a damn good idea.
UPDATE #2- Just heard from Fred who contacted the editor of the publication that posted what I quoted above-and yes ,it was an April Fools joke! Well, I'll have the last laugh when the test model proves that the configuration works!


See the picture below-click:

 

[Doug Lord]

MPX Test Model

There has been some nonsense put out by a couple of very uninformed people on another forum about hand shaping RC model foils vs computer cutting and shaping. The gist of the comments was that it wasn't possible to get exact shapes reproduced by hand. I've been building models using foils since I was 9years old-and I'm older than that now. I can assure you that most RC model foils are hand built at least for one offs used for testing. I produced RC sailboats-about 50 of them and I built all the tooling for the foils from one off hand shaped plugs and they worked exceptionally well-particularly on the F3- the worlds first production RC sailing foiler with hand shaped plugs for all the foils with the main foils assembed by hand.
One reason I'm bringing this up is because the two uninformed( bb&co) individuals on the other forum have dissed model craftsmen everywhere but not only that they simply don't know what they are talking about: I just found the picture below showing Luna Rosa employees hand fairing the main foil on Luna Rosa's 72' Americas Cup Cat! They're using patterns very similar to the ones I use to get the shape I want.
Done carefully with real craftsmen the foil shape can be as precise as desired model or full size:

Picture by Pierre Orphanidis---

click and expand, then click again:

 

[tomas]

There has been some nonsense put out by a couple of very uninformed people on another forum about hand shaping RC model foils vs computer cutting and shaping. The gist of the comments was that it wasn't possible to get exact shapes reproduced by hand. I've been building models using foils since I was 9years old-and I'm older than that now. I can assure you that most RC model foils are hand built at least for one offs used for testing. I produced RC sailboats-about 50 of them and I built all the tooling for the foils from one off hand shaped plugs and they worked exceptionally well-particularly on the F3- the worlds first production RC sailing foiler with hand shaped plugs for all the foils with the main foils assembed by hand.
One reason I'm bringing this up is because the two uninformed( bb&co) individuals on the other forum have dissed model craftsmen everywhere but not only that they simply don't know what they are talking about: I just found the picture below showing Luna Rosa employees hand fairing the main foil on Luna Rosa's 72' Americas Cup Cat! They're using patterns very similar to the ones I use to get the shape I want.
Done carefully with real craftsmen the foil shape can be as precise as desired model or full size:

...

Doug, I have been wondering about the dimensional sensitivity when scaling these foil profiles by hand in models such as yours. Would you expect the required accuracy to faithfully represent the selected profile that you use to be, say for example, 0.1 millimeter or ?

Since some of the profiles are thin even at full scale, it made me curious. Surface finish as well is probably important. Good luck and much success to you.

 

[Doug Lord]

MPX Test Model

Doug, I have been wondering about the dimensional sensitivity when scaling these foil profiles by hand in models such as yours. Would you expect the required accuracy to faithfully represent the selected profile that you use to be, say for example, 0.1 millimeter or ?

Since some of the profiles are thin even at full scale, it made me curious. Surface finish as well is probably important. Good luck and much success to you.

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The idea is to precisely(or as precisely as you want to be) match the foil to the pattern. That can lead to great accuracy but I'd say something on the level of .198mm or .0078". However, I don't feel that kind of section accuracy is required on these foils but it's what I think I am getting or a little better.
My mentor, Dr. Bradfield, didn't feel that foil section accuracy was extremely important on models in the following speed ranges for a model testing foil area and placement. He would say that as long as area,planform and T/C ratio are exact, "the section doesn't matter all that much." I try to get as accurate a shape as possible just because I can. Surface finish is very important as well. One other point-these foil sections, and T/C ratio's don't represent a scale foil-both would be much different on the full size boat, but the planform of the foil is exactly scale.
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For your info, the RE#'s of the ama foils(curved + "L") are:
1) 6mph/5.2 knots= 181,500
2) 10mph/8.69 knots= 302,500
3) 15mph/13 knots= 453,750
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PS-thanks for your good wishes!

 

[Doug Lord]

MPX-Test Model

The foils are being sanded using grits from 40 to 600 as required while constantly using the patterns to maintain accuracy. Filling done as required, surfacing with Duratec. Painting white with red stripes added.
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High likelyhood that I will make the ama foils retractable by radio at some point after she initially flies. May also incorporate a servo for each ama foil to adjust the angle of incidence at that point. I'll probably use a servo at some point in testing to manually control the main foil flap instead of wands just to try it-low priority. A servo may be used with the wand setup to allow turning off downforce. With the servo, the main foil flap would be prevented from going up which will allow only vertical lift.

 

[Doug Lord]

MPX Test Model

Here is the rudder with the brass pivot tube installed and ready for final carbonation. The rudder is reinforced with three solid carbon rods and uni over the tubes. Also shown is the rudder head design with the attachment "box" that holds the rudder to the carbon tube portion of the gantry.
The third picture is of the solid carbon main lifting foil and the rudder lifting foil-these foils are thin-9%-but that is thin with such a long narrow(high aspect) foil.

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[Doug Lord]

MPX Test Model

Here is a shot of the most important tool I have in doing these foils-my digital caliper which allows me to get the T/C(Thickness/Chord) ratio exactly right as well as to measure differences in the part and the pattern using a thin shim:
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[Doug Lord]

MPX Test Model

Ama foils and daggerboard have been trimmed and rough sanded and matched closely to the patterns. The rudder has been carbonated ,and rough sanded. Carbonating included reinforcing of the head of the rudder and structurally integrating the rudder pivot tube to the rudder. Filling, final sanding and measuring starting tomorrow or Tuesday-probably will take a couple of days. Then daggerboard, main foil(and flap), rudder and rudderfoil will be assembled before final sanding of the joint area and the bottom center of each foil. The bottom center of the mainfoil and rudderfoil have been left unshaped because they are exactly 90 degrees to the leading edge of each board. That simplifies assembly.
Anyway, making tedious progress.....

 

[Doug Lord]

MPX Test Model / Rig Development/historical

With the recent rig developments in the LAC by the Canadians-the retractable slats-I recalled an experiment I did about 30 years ago with an rc cat. I cme up with a "ribbon jib" with an equal sized very small boom and gaff on thebottom and top of the sail. It was something like 2-2.5" chord and 55-65" luff/leach. The boom and gaff pivoted at the quarter chord point. It made an astonishing difference in light air. These are really old pictures but you may get the idea:

Pictures from left to right:
1-Slat as shown in CA Marchaj's book,2&3-RC cat with the "ribbon jib" :