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

MPX / SRT Test Model

Here is the crossarm jig. It will allow me to carbonate the centers of both crossarms at the same time and that will make assembly in the "master jig" much easier.(Note tubes in more or less the correct position)

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MPX / SRT Test Model

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Most of the above post is still correct for the building of the foils, except the part about curved foils is omitted because the new shape, inspired by TNZ's AC 72 main foils, is sort of a combination of an "L" foil and a curved foil. It has some of the advantages of a surface piercing foil in that its area will automatically reduce as speed increases. All foils will have their angle of incidence adjustable on the beach and the main foil uses a flap that is adjusted automatically with a wand(surface sensor). The main foil will be set at +2.5 degrees, the ama foils at about +4 degrees, and the rudder foil at 0 degress -all relative to the design waterline.
There is a relatively big difference between the model and the full size boat in terms of how it is sailed. When the full size boat is launched both ama foils will be retracted with the lee foil being lowered as speed builds. But on the model, both ama foils will be down to start with. This gives extra foil area to get the main hull up but as soon as it flies it will heel a bit, begining to load the lee ama foil and main foil only-the windward foil clears the water at this point and that drops 33% of the foil wetted surface right off the bat. Next, the main foil begins to unload as the speed picks up, reducing induced drag until, at about 10mph, the ama foil has most of the weight on it. The boat will be, essentially, sailing on one foil with far less drag than a Rave or Trifoiler configuration. This foil system will help enormously in light to moderate wind getting the mainhull flying early-much earlier than possible with any oversquare tri and earlier than possible with most trimarans period.
That is, if the system works like I think it will.

Pictures,L to R,1-4-The foil loading info from the F3 in pictures 1 & 2 served as the basis for the design of the model MPX foils. The main foil will have a partial span flap as shown in pictures 2 and 4 as well as an almost identical planform. The rudder foil will appear similar but w/o the flap since the angle of incidence is adjusted on the beach(not while sailing) by moving the whole rudder +foil. Should there be a need to adjust the rudder foil underway it will require adding a servo but it will be very simple.
The ama foil in picture 3 can be set at almost any depth-the depth shown is what appears to be ideal for full flying. With the foil retracted it loses some vertical lift and can be sailed with some ama contact with the water. Normally, the ama is designed for intermittent contact. That brings up another difference between the model and the full size boat: there is no movable ballast on the model as there is on the full size boat so the model will likely heel over a bit as it gets started getting the ama wet.

 

SRT / MPX Test Model

Crossarms finally carbonated. Tomorrow the Giant Jig......

 

SRT /MPX Test Model

Here is the "Master Jig" designed to give multiple frames of reference for aligning the crossarms for bonding to the boat and to the ama/curved piece(s). Has a notch cut thru the middle for a straight edge(red) so that the main hull can be set up accurately. I can reach everything from the aft side so it looks like it is going to work well:

 

MPX/SRT Test Model

I've lost five days of work on the boat this week so haven't gotten a lot done.
These pictures show the main hull locked in to the jig. Very tedious to get it properly set up! I used 1/8th" balsa "plates" to allow me to use cyano and baking soda to attach the support structure to the jig. The balsa plates were glued in place with epoxy.
Next step is placing the amas so they can't move during the carbonation of the cross tubes to them and to the main hull.

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Great find from the "Radio Control Multihulls" thread on SA Multihulls:
http://www.i-gotu.com/
A little gps device that can record your speed etc. Chris from Germany uses it on his RC trimaran.
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Just ordered one for the test model! 4/15/13

 

MPX-SRT Test Model

Here are the first shots of the boat completely mocked up. The amas and main hull are in their exact positons with the crossarms taped in place. Should have the whole thing locked together shortly.
This pictures give a good look at what the final boat will look like. Let me tell you this thing is huge!
click for larger size:

 

I haven't been making noise in the thread for a while, Doug. But I'm still keeping track of it, and I'm still fascinated by what you're doing.

 

Doug, do I understand correctly that this is a one-third scale of full size?
Apologies if this has been answered already.
I have not read the entire thread.

Best of luck and hope that the model testing provides lots of helpful results.

 

SRT / MPX Test Model

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Thank you Troy-getting closer. As soon as the crosses are all bonded, I'll take it apart and down to the water for a float test. The cross arms simply(!) pull apart....

 

SRT /MPX Test Model

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Hi, Tomas-the scale is: 3.33" to the foot..... which means the full size boat is 3.56 times the length of the model.

 

MPX / SRT Test Model

Locked in!(I hope) Had a problem with the scale(actually, the scale operator) when mixing this ultra light weight epoxy putty from Aircraft Spruce that I've used to bond the cross arms to the amas. I had to estimate the ratio by eye since I left the "lock" on the scale. Luckily for me(I hope) the ratio is the same by weight or volume. Another problem was that the stuff ran-guess I exceeded it's no-run capability-damn it. Had to wrap the corners with peel ply and masking tape. High likelyhood of having to grind a lot tomorrow. Not so bad except the damn thing is in my house so I have to take the time and cover everything.
Oh, well-it's been going fairly smoothly. I hope I got the ratio right or I could have a big mess!
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UPDATE-4/18/13- The putty set up perfectly so it appears I still have my "eye" for mixtures if I get caught in a jam! The runniness of the putty didn't hurt a thing since I was able to fold over the peel ply and tape it. Instead of creases in the putty the joints turned out relatively smoothly-I still had to cover up the inside of the house and lightly grind but that's ok. Next step: carbonation -and then water!

 

MPX/SRT Test Model------ Historic Day #1

What a great day! I got the crossarms glassed on to the boat-it is now a trimaran. Worked hard on this for a long time.....Feels good to have created an actual boat after all this time.
(thanks to anonymous for the rep!)
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MPX-SRT Test Model Historic Day #2, Part 1

I can't tell you how incredibly happy I am to have reached this stage! All the design effort, all the work and the thing looks tremendous to me. It's amazing how small it seems after getting it out of the house. And it was a real excercise to get it in my Hyundai Elantra-but it did go in. No way that it will fit in with foils I don't think-and the rig may be too tall to go in even with the back seat down. I've been considering getting a small enclosed trailer...

Click twice for a much better view:

 

MPX / SRT Test Model Historic Day #2, Part 2

She floats!! And not only that she floats well- even with 5lb extra on board so no weight problem(haven't weighed the components yet so that may be revised). At this point any extra weight will only affect how early the boat takes off. It's probably too late to increase SA. But based on how she floats I'd say she's ok-in fact I'd say she's fantastic!
Note: The wind was about 20k offshore and it was very, very difficult to get floating pictures without having the boat blow out of reach! Just barely caught it a couple of times. Hell, shes fast with no sail!

Click twice for better view:
Note-Pictures,L to R 1-5 The can sitting on the boat is 3lb which represents what is still to be added to the boat. Picture 5 is a close up of the bow showing a slight overhang-just perfect. Boat is stitting with about a 1 degree pitch up which is ideal.