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

MPX Testing and Development----First Flight!

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Thanks ,Cav! Of course, you're right- but yesterday the scientist in me was out voted by the sailor wanting to fly!

 

MPX Testing and Development----First Flight!

Here is the video again-should be "fixed" now:

UPDATE-6/29/ 1:30PM EDT-music in video changed

https://www.youtube.com/watch?v=LmXCdAlo4mk&feature=youtu.be

 

MPX Testing and Development----First Flight!

Some more thoughts on sailing yesterday:
1) the waves were 2' high for a 19.5' version of the test model or 7.3'(!) for an AC 72 length version of this boat. Yet,other than skipper miss-steps she handled them well.
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2) there is no way the ama foils would allow the ama to fly above those waves-they aren't deep enough to allow that. So in relatively short chop conditions the ama will always go through the bigger waves-and thats what it was designed to do. The ama does that while the main hull flies clear of the waves-when she's tuned up she will fly steady with the main hull clear of the waves. In smoother water(or longer swells) the lee ama will fly clear.
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3) Comparing this performance with my 14 year old F3 foiler is not possible: the F3 would not sail in those waves-she would bottom out. How do I know? Dr. Bradfield, Tom Haman and I took the boat out in significantly calmer conditions in the Indian River and she bottomed out. The MPX foil configuration is capable of handling much rougher conditions than any "normal" foiler would handle.
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MPX Testing and Development----Rudder Induced Dynamic Pitch-up

Somethings been bugging me since I saw the dynamic pitch-ups and especially the one toward the end of the video that Slavi referred to. It's obvious if you study the video* that it was caused directly by a quick turn of the rudder and set up by the boat being so overpowered(well heeled). Skipper malfeasance- nothing whatsoever to do with the foiling system.
But I had seen that before but where? I just figured it out: years ago(16) I built a large RC tri for Dr. Bradfield to use to test the foil arrangement for the 40 foot SKAT. When I brought it over to deliver it to him we sailed it in the little basin in Melbourne.
The boat had a deep, high aspect rudder and daggerboard and if you slammed the stick over to do a quick turn while the boat was heeled the rudder acted like an elevator and caused the boat to pitch way up. We did it for kicks then. I remembered that Dr. Sam had taken a picture-and that's it below-we all thought it was hilarious . The boat would tack smoothly if the skipper did it right . He got the picture below,left, at the moment the rudder was turned max. The other picture is the same boat with the scale foil positions for the 40' SKAT.
My mind is now at ease.......
* you can actually see the rudder move an instant before the pitch-up

 

I fly RC flying plank wings. The elevators movement when setup with a rearward CG is so small you can hardly even see it. The radio allows adjustment so the full throw of the stick hardly moves the servo at all, or I can tune it so I still have full deflection of the elevons but the servos hardly moves under small to medium stick movements. Forgot what the setting is called. Exponential I think?

This might be the go for the rudder if you have not already done it.

 

MPX Testing and Development----First Flight!

Thanks, Dennis. This radio has all kinds of stuff like that. I'd like to see if I can teach myself to do it right, though with the deep rudder I may have to use the radio.

 

Its not cheating. Its just using the correct setup for the application. If you were actually sailing a full scale version you would not have to deal with accidentally making massive rudder angle changes with a twitch of the thumb. It would literally be impossible to fly some of my planes without these settings. Dont make it hard on yourself if a setting can help.

 

MPX Testing and Development----First Flight!

I basically agree with you but I need to do it manually for a bit*. When I first noticed the pitch-ups I tried to control it but with the excitement of the moment it didn't work. So,I'll use it at some point. I'll read the manual to see how to set it up-maybe I can switch it on-off.
* It helps me to get a "feel" for the boat.....
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VIDEO: youtube has finally finished doing their best to eliminate the shakiness and has added the music I picked out from their list.

 

My radio has switches to change the response between 2 settings.

 

MPX Testing and Development

Thanks to a guy on rcgroups who must live in Melbourne ,Fl I found what could be the perfect flatwater test site. It's a small lake /large pond at Wickam Park just a bit north of Melbourne. Some guys were racing RC Solings and the wind seemed steady for trees not too far away. Fairly easy access though the boat will have to be carried at least 50-75' out to get to deep enough water. There is a small dock but the water is too shallow within 20-30' of the dock.

 

Watch for

Maybe use a jon boat.

 

MPX Testing and Development

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We've got them in the river too-just kick em in the nose and move on(riiight)!
Did you hear about the shark that was found in a pond just south of here? It was caught and released into the Indian River.....

 

Yeah, not just a shark; a bull shark(pound for pound more dangerous than a great white) named Sushi!

 

MPX Testing and Development----Control Issues

I've figured out the other control issues in addition to the "pitch-ups" that I discussed in post 1414:

1) Vang--the gooseneck slides on a vertical rod. I tied the downhaul to the gooseneck so as the vang was tightened the gooseneck tightened the downhaul. Unfortunately, the power of the vang stretched/loosened the line dissipating the vang power-so when it was tightened to de-twist the sail it may have done that for 10 minutes but then nothing. Solution: decouple the downhaul from the gooseneck and fix the gooseneck so that it can't move down(or up for that matter). Maybe add a cunningham grommet if there is not room around the gooseneck for the downhaul to work. Use a drill bit or suitable rod to tighten vang better.
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2) Peak Halyard and GCD-Gaff Control Device is the thing sticking up above the gaff to which the peak halyard is attached-line stretched. Solution: convert to spectra and /or increase purchase. I may change the position of the bowsie in order to make it easier to adjust when the Wing Tip is in place.
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3) Sheeting system-line from the jib side of the drum jumped off because, under a lot of load, the sheet induces slack at the drum. This actually makes me happy-I was afraid I might have stripped the $380 winch! Solution: add a block with a spring to that side of the drum so slack never happens. Never subject the winch to loads outside its design range-reef, switch rigs or don't sail!
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4) Rig slack. This happened because I didn't tighten the shrouds enough for those conditions which allowed the rig to go fore and aft a lot which allowed the top of the main to have undue influence on the pitch stability of the boat as well as screwing up the set of the jib. Will discuss the matter with the crew to see to it that the shrouds are always tightened.(geez)
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5) Being overpowered:
a. I dodged a bullet this time by not ruining the sail winch-it is NOT set up for the load found with a 10 knot breeze+boat speed+ waves. Will go with the SA limits I know and use the windmeter to make sure I've got it right.
b. Will design and build a new #2 rig instead of reefing the original main*. The reefing system I used on previous boats won't work with the rotating wing mast.
I was mighty impressed with the way the boat handled the fact that it was overpowered and sailing in big waves so I want a rig that will hopefully allow sailing in almost any condition. Removing the jib in those conditions wouldn't help-too much wind for the main only.
* This will be expensive and take some time. In the meantime I have an old rig for a much smaller boat that I may use. Will at least have entertainment value when the mast snaps like a twig......
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6) I've pretty much come to the conclusion that the beam could be increased. You wouldn't do this on a "normal" trimaran like this because the full size version as is would not fly the main hull before the wind blows 15+ but with the mainfoil capable of lifting the main hull at a boat speed of around 5 mph it seems to me that an increase would be beneficial in both light and heavy air.
In light air, the loading of the ama foils would be reduced a bit, in heavy air the RM would be greater. I may do it on the model but not for a while and the practical limitations, from an engineering perspective, on the full size boat would have to be carefully looked at. But from strictly a performance perspective it would work.
--main hull LOA = 5.5' (19.5 ')
--beam now=6.8'(24.5'), proposed increase to model 1'=7.8'=28'
--Current beam=1.24 X Length; proposed=1.42 X length

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Next test sail will be in wind between 5 and 7 mph*. The designer says the foils should work in those conditions and the boat crew has been warned to not repeat the joyriding in unscripted conditions!
*I tend to use mph and not knots because the wind pressure table I have is in mph and the foil lift formula uses mph(ft/per second). If you want knots divide mph by 1.15.
Stay Tuned........
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Wish list:
1) a better camera,
2) an onboard camera to replace my gone pro,
3) somebody flying a drone to take aerial video. I met a guy a few months ago at Kelly Park and he said he would do it for free-hasn't responded to my e-mails.
4) a damn trailer so the boat can be left assembled in the garage-it is such a pain to assemble and disassemble each time in 95 degree sun.
--I'm going to work on getting this stuff over the next 6 months or so, with "or so" being definitive.....

 

MPX Testing and Development

A germ of an idea has begun after the last sail. I'm beginning to believe that it may be possible to sail this thing thru a tack or gybe on the main foils with no other part of the boat touching the water-except the ama foils. Maybe. If that can be done at this weight it would be nothing short of remarkable. We'll see.......