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

MPX Testing and Development

Last video, once again:

 

MPX Testing and Development

Most of the day I've been sanding and filling but tonight I decided to watch the latest video again. And I discovered something about the wand system that had totally escaped me. The system should be set up with water pressure against the wand paddles the primary force that holds the flap down for take off: water pressure moves the wand back which pushes the flap down.
But, in the video in light air, the wand was not going all the way back and it finally dawned on me that the way I have it set up the spring attached to the lever applies the same force whether up or down. That's wrong because if it is set up that way the spring force can pull the wand down in light air when the boat is not too fast-in fact as best I could tell the wand had been pulled down so that the flap was in ,approximately, the neutral position. Good for light air but terrible for takeoff! The spring has to have maximum force exerted when the flap is up because that is when the boat needs downforce and there is nothing holding the flap up but the spring force(water pressure on the wands holds the flap down for takeoff). But the way I have it rigged, it has the same spring force whether the flap is up or down so the spring force is working against take off!
Something did not seem right to me but I couldn't put my finger on it until I noticed the wand in that video-just fantastic that I discovered it tonight-very simple to fix.
See the sketch(click for better view) :

 

MPX Testing and Development----Completed Foil Mods

Here are some shots of the modified foils. See the previous page,post 1575, for the tech stuff on the main and rudder foils. And post 1561 on the ama foils and the i-flap.You should read that to understand more about picture 3(top, far right below)
All is ready for tomorrows test-except the weather-not looking good but still a chance.
click for best view-

 

Doug. In my post 1552 I postulated that increasing S is the best way to ensure more lift with less detrimental effects.
Therefore it is my HO that you should increase the area of your main foil before anything else.

 

MPX Testing and Development

Paddy, you may have missed this post. All the foils have had an area increase and the main foil slightly more than shown below because of the additional flap area being added today since I can't go sailing. Pictures of the finished foils in my previous post. I increased the areas based on what worked on the F3 plus a little extra
on the rudder foil. The ama foils are very experimental and most likely will have to be reduced a bit in area:
NOTE-the mainfoil portion of the quoted post below is corrected in the next post.

 

MPX Testing and Development

This is a summary of the changes /fixes made since the first video: (Next sail Thursday 7/24-I hope.)
1) AOI of mainfoil reset at +2.5 degrees,
2) AOI of each ama foil doubled from 3.75 to 7.5 degrees(should be too much),
3) Sheeting system travel reduced which should allow the main and jib to luff at the same time as opposed to the jib luffing early as shown in the video about 4:10 in. If this fix isn't good enough may need to add a separate jib winch,
4) Vang and downhaul decoupled and now separately adjustable. Downhaul now 8/1,
5) "Peak halyard"/ gaff control line changed to spectra and purchase increased to 4/1,
6) Wands shortened 5". Wand now adjustable between 7.25 and 11.75". Made adjustable,clip on wand paddle extensions to allow wand length increase of 2"-just in case. Wand paddle widened 7/22/14,
7) Wand plate attachment system changed-eliminated flexible washers,
8) Wing Tip installed and subsequently cut down slightly,
9) Rudder(ail/cyclic) channel on radio programmed to reduce the incidence of dynamic pitch-ups(and/or pitchpole) caused by abrupt rudder movement.
10) Shore crew properly chastised for allowing boat to be sailed with loose shrouds(resulting in a saggy forestay).
11) Added clear Super Lube grease to both wand axle retainers: last time salt water got into the tubes and slowed the movement of the wand axle-had to take the boat out front and use the hose and spray nozzle to clean out the salt-was hard to get to 100% again.Salt water also got into the jib outhaul adjuster and the jib pivot adjuster. Both are froxen up and need to be sprayed with fresh water.
12) See foil mods below(and pictures in previous posts)
13) Expect to increase beam from 6.7' to 7.7' down the line.
14) See post 1426 for the best analysis of the foil assist video.
15) Wand paddle widened.
16) Reefing system figured out ,see post 1527.
================================
Foil Modifications since last sail:
The mods allow the foils to meet or exceed the benchmark of the F3:
Note-these are corrected from the quote above(post 1580) :
1) Main foil:
a. increase of area from 50 to 84.22 sq.in.
b. span increased 23" to 29"
c. foil loading= .188 lb/sq.in(F3=.188)
d. aspect ratio=7.6/1
e. partial span flap increased from 11.125" to 15.125"/35% more area / 23.7% of mainfoil area
---
2) Rudder foil:
a. increase of area from 26 to 49.8sq.in
b. span increased from 18.75" to 23.25"
c. foil loading= .106 lb/sq.in.(F3=.118)
d. aspect ratio= 8/1
---
3) Sail Area/Wetted Surface(on foils) with completed mods: 11/1 (F3=10/1)
-
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Paddle and flap mods done today. Main foil and rudder foil at start of mods last week(finished pictures in a previous post) you can clearly see the outline of the original foil within the new foil:
click for best view-

 

I am away cruising right now. But even at home I rarely look at your thread as it is so repetitive, sorry

However two things: The title includes the words "self righting" is that just the masthead float/top of mainsail or something else?

Have you considered towing the model without the rig so you have a steady, repeatable, power source to refine the foils?

I haven't looked at your videos, just the still shots you posted, but it does seem that the boat is very unstable in flight, too much for a human crew

Richard Woods

 

MPX Testing and Development

Thanks Richard. The self-righting portion of the original concept is on hold while the MPX foil system is developed. The masthead buoyancy is so she doesn't turn turtle in the event of a complete pitchpole. There was a pitchpole caused by the rudder(and the guy moving it) but that, like the major "pitch ups", was caused by an overly sensitive rudder now fixed(I think) via the programmable radio. Anyway, she recovered by herself from that pitchpole wannabe. There have been problems with the foils but instability wasn't one of them. The area has been increased on all four foils to bring it to the foil loading of the F3. Towing is always an option but I don't think it is necessary at this point.
Next sail Thursday.
PS-hope you're having a great cruise....

 

Doug, take a breath, leaving your silly fargo trucking toy alone - right now there are important and evil things occurring in Israel and Ukraine. Ever check out the political sites, like Counterpunch, Truthdig, Tomdispatch and many others? This fixation with yer bloody childish model boat .... is really pissing me off (and I'm sure, many others).

 

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Thanks for the advice, Gary.

 

MPX Testing and Development

Here a a couple of photo's, one of the new wand "paddle"(same each side) and one showing the new flap-35% more span than previously, and the old flap just before the mods.
Tomorrow is probably the last chance to sail with Dan until next year and the weather looks poor. We're going to go early so we may be alright....

click-

 

Doug.
I work with organisations all day, every day - that are trying to make this world better. I work every day (as unpaid voluntar) to get money to organisations for helping the homeless. Most of my friends are peace-activists in one way or another. And I enjoy to read about you designing just that kind of boat that Is as close to the boat of my dreams as I ever could come. I am looking forward to see more updates in this project.
Keep up the good work.

 

MPX Testing and Development

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Peter, thank you very much for the encouragement-it means a lot! Your work sounds like you are really making a difference in peoples lives!
Again, your post has made my day!

 

Fire Arrow on Foils!!!!!!!

For some damn reason there is a problem on youtube with the video-they say its in the que and will be processesed as soon as possible so I'm posting the pictures that tell the story and the "mov" version of the video. The boat was simply spectacular today. The wind was 3-5mph max but was 4-6 at my house from the south when we left. By the time we got to the Port it had switched to the SW and died to 3-5. But the waves left over from the 20 mile fetch south were still "bending around" thru the bridge. I would have preferred flat calm -no waves-just wind. But as it turned out-well, it could not have turned out better. First thing we noticed was that the lee ama popped up-it was then we knew this was going to be a great day. Shortly after the ama popped up the whole boat did and we got a couple of stretches of extremely stable, fast foiling. Perfect pitch stability, perfect ama foil altitude control-man, she couldn't have done any better. And all this in a 5MPH breeze! I couldn't be happier and more satisfied that the step by step analysis I did after the first three videos was right on target.
Enjoy:
Be sure to click on the foiling pictures they are just great at the right size--
PS-the"mov" file was too big-so we'll have to wait till I get youtube sorted

 

It looks like your perseverance is starting to pay off for you now Doug