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

There was (and I think still is) a boy scout merit badge for knot tying, it has an image of a square knot on it. I proudly earned mine when I was eleven by passing the knot tying test from memory the first time, the taught-line hitch was one of them.

I guess you never got that one. too bad, I find all of those knots still handy and useful to this day over 40 years later.

 

It's been 50 years for me.

 

42 years as best I can figure based on my memory how old I was when I passed that test.

And yes, much of what was required to get to first class was some of the best training I ever got.

"Be prepared", and "leave it better than you found it" were also pretty good things to learn.

 

Good point, now that I think about it, Scouting laid the foundation for many useful skills and lifestyle philosophy: first aid, knots, survival, self sufficiency, responsibility, hygiene, cooperation, team work, loyalty, respect, duty, honor.

Perhaps if more youngsters had been introduced to Scouting in more recent years they would be much better adults, and this country would not be in the condition it is now.

 

Thread drift?

Maybe another thread on scouting?

 

An important part of scouting is the Sea Scout program.

 

Done.
http://www.boatdesign.net/forums/education/sea-scouting-48782.html#post660783

 

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Thanks, Hoyt!

 

http://www.boyscouttrail.com/i/w_badge_images/salute.gif

 

MPX Test Model

The sides, front and back of the balsa/carbon radio box are laid out. The box is being built with .125" balsa with .020" carbon "dragon plate" glued to each side of each piece. The box will be carboned to the deck. Inside a piece of .031" epoxy/glass sheet is being used as the servo mounting board for the smaller servos with the big sheet winch mounted directly to the stb side of the box. Another piece of balsa/dragon plate will be used for the sealed top of the box. Having a bit of a problem working out the main sheet with the Harken traveler. The traveler is the smallest full size Harken traveller with a ball bearing car.
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Note: I was convinced, after the previous water testing I did, that I could not possibly get the whole boat and rig in my Hyundai Elantra. But when I made the final pre-sailing water test the other day I found the keys to the puzzle that allows the two ama's with foils installed , the main hull, separate main and rudder foils, stand and 8.75' rig to fit in the car!
I was going to have a box built(can't do it here) but it was too costly.

 

MPX Test Model

I wanted to post some facts about the ama foil determined during its design.
These numbers are based on the distance below the ama of the flight waterline. The percentage of total lifting area that changes with immersion and/or flight is the main number here:

1) Distance below ama= 1.375", Total lifting area=11", nominal area that changes lift with immersion/flight= 4" or 36%.
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2) Distance below ama= 3"(nominal flight waterline), Total lifting area=10.5", nominal area that changes lift with immersion/flight= 3.5" or33%.
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3) Distance below ama= 4", Total lifting area= 9.69",nominal area that changes with immersion/flight= 2.69" or28%.
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4) Distance below ama= 5", Total lifting area= 8.22", nominal area that
changes with immersion/flight= 1.72" or 21%.*
* tip has breached the surface at this flight waterline and makes the whole lifting area a foil whose lift changes as the foil is immersed or flies higher. In other words, at this flight waterline the whole lifting area is a surface piercing foil. It is also likely to be subject to ventilation at this flight waterline. Ventilation of the foil is unlikely to be much of a problem since the pitch angle (running angle/angle of incidence) of the foil is controlled by the main+ rudder foil acting together.
The foil will only reach this flight waterline at high speed if the angle of incidence of the foil is too great. There are ways that the foil can be modified so that it has high lift at low speed and a low angle of incidence at high speed. I'm hoping that any modification won't be required. The key ,for me, is to have an ama foil that, if anything, requires only one adjustment of the angle of incidence throughout the speed range. Best is zero adjustment required.
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NOTE: As the ama foil flys higher-particularly with more cant(head of foil to leeward), leeway may have an affect on the lift generated by the "L" portion of the foil. Since the boat has a daggerboard as well as this foil, I don't expect that the leeway affect on lift will be very great- at least not until the flight waterline has passed the #4 position going toward #5.Leeway had a great affect on lift on the AC 72's but this boat doesn't work like the 72. We shall see.........

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This picture shows the ama foil at the nominal flight waterline(3" below the bottom of the ama) with neutal cant(athwartship position of head centered).

 

MPX Test Model

My thanks to Jeff for giving this thread back to me and all those who have been following progress! And thanks for all the support ,guys! Good stuff coming up, I promise.....

 

<Thread drift posts have been split to http://www.boatdesign.net/forums/multihulls/split-off-topic-posts-mpx-thread-48872.html so hopefully this thread can remain peaceful and on topic and those who are interested in following the details of the model can do so, or not, as they desire>

 

Could you refresh my memory please. Is the boat 2.000 metres square?
And what is the intended full size boats length/beam?

Thanks
Bas

 

Sorry,
Just checked the first page and found the information there. On the first page you quote the draft with dagger board at 1.400 metres. Yet the dagger board in the scaled model would indicate that figure would be far greater than 1.400 metres. Of course I'm sure to be wrong as I can find no pictures side on to scale it from. One other point if the full size craft is to be 6.7metres wide how will the dagger board be installed? Even laying the boat on its side it will be 3.2 metres off the ground. And once installed how would one get it into the water?