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

MPX Test Model----------------TESTING

One of the tests, after getting most of the video and stills in the "normal" configuration, will be the planing ama with the "normal" ama foil removed. It will be tried naked and with a much smaller ama foil.
From discussions ,in 2011, with a windsurfer guy I know well and a couple of other sailboat designers this is the concensus of what the planform of the planing shape should be. The UptiP foil will be removed and a flat shape with as yet undermined "edge treatment" will be attached removably to the ama. Smaller experimental foils will be tried with the planing surface after sailing with the planing surface alone. The treatment of the edges we don't agree on:

 

I'm Sorry Doug. I am a "Windsurfing Guy" from way back and I can't see why you have to immerse the whole Ama before the planing surfaces take effect.
The very best planing surfaces exist in the shape of water skis.
I had a Piver Frolic and on that TRI the Amas were just water skis with sides.
It would definitely plane the amas at high speed and could beat the S--- out of a Hobie 16 any day.

 

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Paddy, what we have here is a failure to communicate! I don't think, in any way shape or form, that the ama would have to be immersed before the planing surfaces take effect!
In fact, the ama w/o the experimental surface is designed for momentary contact at speed. And my little MPX 12 design(full size) is designed to sail on planing amas, with foil assist(if the foils help).
The purpose of the experiment above is to get the right surface area for this particular boat sailing with no ama foil! Just a planing ama....
I really believe that there is tremendous potential for a small tri that uses foils to get the main hull up in light wind and then sails on its planing ama. Probably wouldn't be faster than a 100% foiler but it sure would be fun!

 

MPX Test Model-------------Testing

Since we're almost ready to begin testing I thought I'd go over some of them.This is one I don't think I've mentioned publically until today: MPX Test Model as
Moth. If I can find a collaborator in the electronics field this would be simpler but even if I can't I may try this manually. The amas would be removed, a smaller rig built and a Trapeze Power Ballast system added like in the pictures of the 36" microMOTH below. That boat was the most difficult boat I have ever sailed and though I got it foiling it crashed shortly thereafter. Several mistakes were made in that boat: 1) it was too small-little mistake, 2) the Trapeze Power Ballast System did not move fore and aft-big mistake, 3) the mainfoil flap was controlled by radio(too much work load-big mistake).
Nothing would be done to the MPX to prevent it being sailed as a trimaran. This type of experiment will be one of the last I use the MPX for.

Pictures-L to R- 1)MPX , 2) MPX as Moth-amas removed,3) & 4) microMOTH:

 

Sorry Doug. My mistake. I was looking at the Ama hull upside down.

 

No worries! It's a topsy-turvy world we're in these days.... I think a small tri
like the little red one would be a blast-I thinking planing or planing with foil assist has tremendous potential especially in small tri's but not necessarily limited to them.

 

MPX Test Model

Geez! This jib/Code Zero attachment has been a real pain. The original idea was to use tubes that simply fit snugly but that didn't work. The new system uses a 2/56 bolt thru the mounting tube that acts as a stop for both the Code Zero bowsprit and the jib tubes(s). Both have a line going to the mast step that holds the tube(s) in position ,tightened with a bowsie.

click--

 

MPX Test Model----------Stand Test

Still too damn much wind for a full rig fitting but I was able to test the stand with the new straps. I used .5" double sided velcro and it worked great-held the weight ok. The new straps allow the stand to open up wider allowing the main foil and wands to clear more easily as well as being more stable with the rig up. Got some different views of the boat as well:
click for MUCH better view_

 

MPX Test Model

When I did the first outside rig test it dawned on me that I could improve the aft angle of the shroud as well as the side to side angle by attaching the shroud all the way out on the curved piece that supports the ama. I guess I didn't realize how good it would be until I saw the whole thing assembled in 3D. Side benefits include reduced load on the shroud and the shroud becomes a backup for the ama retaining line.

Here's a couple of pix:

click---

 

MPX Test Model------Angle of Incidence Indicators

I was moving stuff around today to set up the charging and radio stuff and I found these stickers that I had ordered about four months ago then carefully hid them.(!)
They will make it easier and more accurate to know what the best foil angle of incidence is as testing proceeds. The starting values are in a previous post as well as in the Spec sheet above.

Pictures,L to R--1) mainfoil incidence markers, 2) Port ama foil marker, 3) Stb ama foil marker, 4) improved mainfoil incidence markers:

 

MPX Test Model------LiFe batteries

At last and finally I got to the charging of the lithium iron(LiFe) batteries today. Really wild charging system where you not only hook the positive and negative to the charger but you hook into the "balance" harness-something that I don't quite get yet but absolutely required of LiPo and LiFe lithium batteries. It all worked well. The batteries retain a charge far longer than the nicads I used to use for RC boats. In fact, it's been about a year since I bought the 2 2200mah batteries and it took about 10 minutes to charge each one! I'm about to power the thing up in the next couple of days.....
click-

 

Lithium batteries do self discharge very slowly, but they still do discharge eventually. And once they have fully discharged and are left in the condition for a long time it will ruin them. EG using them until they are flat, then leaving them for a year without charging them first. So I hope they had a good charge before they were left for a year.

 

Doesn't sound good, Doug. As DennisRB said, Lithium-ion batteries should never be left discharged for such a long time. A recommended practice for long-term storage is to charge them to about 40% and then top up from time to time to keep the charge between 30-50%.

Another thing which shouldn't be done is to quick-charge them with various devices which promise miracles. In general, a charging time of less than 1 hour is not recommended, especially if the battery was not specifically designed for ultra high-speed charging. In your case, you have charged it with a 21 A current (10C). A repeated charging (or discharging) of your battery at that current level will quickly degrade the maximum battery capacity. It won't be long before you will notice in horror that your 2100 mAh pack has become a 1500 mAh pack, and then a 1100 mAh pack. But then, you could have installed a 1100 mAh pack right from the beginning, and save 50% weight!
So, by properly maintaining and charging/discharging your battery pack you actually save weight, which is imo a pretty important point in your case.

Cheers

(and put the damn thing in water, man!!! )

 

MPX Test Model--------------batteries

Thanks for your concern guys but everything is ok with the batteries -at least according to Tony Stillman of Radio South where I bought them. I've done business with Tony for about 20 years and he's never steered me wrong yet. It was Tony that pointed out how much safer LiFe batteries are than LiPo.
As to charging: these batteries were nearly fully charged before I stuck them on the new charger at under .5 C-not 10C! They are 2100mah so one C=2.1
and they were topped off at a 1 amp charge rate as per Tony's recommendation. Final voltage on these 6.6v batteries was 7v on one and 6.9 on the other. I have an infrared thermometer that uses a laser for non-contact temperature measurement-and the batteries never exceeded 87F during charging. Never exceed temperature is 140 degrees F. The maximum charge rate on these batteries is 3C, but the manufacturer recommends 1C for better battery life. The charger is specifically made to charge LiPo or LiFe batteries-you have to select which one. If you select the wrong one the machine automatically senses it and won't work. With all the sophistication of the charger, it does not automatically shut down when full charge is reached -it just sets off an alarm which is very loud. But thats ok because I would never walk away from a lithium battery under charge!
I have a neat little switch from RMG(Guyatt-that made the sail winch) that includes a votage regulator to send 5 volts to the reciever and the full battery voltage to the winch.
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When I built production RC models, I used nicads and toward the end, nimh(nickel metal hydride)batteries. On the F3 foiler, the battery was twice as big as these batteries for something like 1100MAH. It was big enough to use as F& A adjustable ballast and was attached outside the hull on a carbon tube slide.
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Thanks again for your concern ---and for telling me about it!
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Note: this battery is rated 10C which means it can deliver a maximum current of 10 times the "C" value of the battery. For this battery that means 10X 2.1=21A. 13 Wh means: 2.1 amps at 6.19v for one hour,or 1.97 amps @ 6.6 v for one hour.

click for better view-

 

MPX Test model-------switch test

Just completed a test of the RMG switch-worked perfectly. I was a little nervous about it because the switch itself is mounted on the board in such a way that it can move around. I e-mailed Rob about it a few months ago and he assured me it was fine. And he was right. The button for the switch fits right into the hole its supposed to. Then when you put the waterproof sticker over it the set screw adjuster sticks to the sticker and prevents any movement but up and down-excellent system!
And the sticker is made with a clear patch just below the switch button cover, for the "ON" LED to shine thru. I was concerned the LED might be hard to see but I was wrong-it is very bright-easily visible in sunlight.
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UPDATE: Guyatt winches now has a new version of the switch -very cool: https://www.rmgsailwinch.com.au/rmg/categories/RMGSwitch/