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

While I agree with you that there is way too little sailing and way too much talking about this boat, I disagree with this consideration of yours.

Clearly, this trimaran is very different from a moth - the stability principles are different and the scope is different. So your question is a bit like saying "Why use cars when we have motorbikes? Get a bigger bike and drive 4 people on it".

 

Talking generally implies two or more participants. A single person talking is more often a rant...

I believe the moth reference was in respect of the use of different foil sizes rather than go-go gadget foil extensions proposed by the proponent. Unless I am mistaken it was not a suggestion to change the foil configuration to two inline foils.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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That's sorta funny: the boat already uses in-line(bi-foiler) main and rudder foils. The removable foil tips have potential in opening up top end speed. But there are problems as I mentioned earlier.
Using multiple foil sets is possible but a fairly expensive solution. It's worth spending time on figuring out a system that would work at much less cost.

Fire Arrow and Dan:

 

"Using multiple foil sets is possible but a fairly expensive solution. It's worth spending time on figuring out a system that would work at much less cost."
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It is also limited in changing conditions. Reefing the foils isn't an onboard procedure on a Moth is it?

 

Fire Arrow Foiler / MPX Foil System Testing and Development

No it's not, as far as I know, but the Moth foils aren't retractable. These foils would be able to pulled up far enough that the person or persons on board could access the tips from just forward of the forward cross arm-maybe. Like I said earlier there are problems with this idea in terms of what it does to the main foil configuration but because this would be done in stronger wind, the main foil will unload very quickly so it may not matter.
The ama foils would not be affected other than having their angle of incidence reduced a lot.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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You may not fully understand the fact that I spent 4 years designing and building this boat and that the foil system uses two different altitude control systems for the first time on any trimaran anywhere. It uses a two stage ama for the first time on any trimaran that I am aware of. All that wasn't by accident- it was designed on the basis of tons of research and hours and hours of design and redesign.
On that day in July this 21lb boat foiled in a 5mph wind which on any small foiler would be tremendous but on this boat, because of the radical design,it was much more than tremendous it was incredibly fantastic! The fact is that the ama foils and main foils worked perfectly-that's the only accurate way to describe it. That doesn't mean there weren't problems-there were and I've discussed them. But no problems with the foils or foiling. That doesn't mean that there won't be improvements but for the first time fully foiling it was nothing less than a rousing success for which I am very thankful!!
If you read the thread you'll see the kinds of refinements I'm looking to do-there is a whole list of them. And many experiments....
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Time on the water is critical for development but because of the factors I've repeatedly discussed I'm limited(for now) in how much time I can spend sailing so every minute has to count. We'll start sailing again probably in April or May-it's up to Dan. And NOTHING I said could possibly be reasonably interpreted as "saying that time on the water means nothing"!!! Understanding the time already spent on the water is extremely critical in learning what is happening with the boat. That's why I've done such a thorough
analysis of every aspect of what was learned so far in testing.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Update of a post first published a month ago:
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I've posted a list of the history of the development of this boat with all the related videos on page 120, post 1787 but I'm going to add another list and that is the things the worked the way they were supposed to-or better. The last video showed some major accomplishments of this design so far(updated 2/18/15) :
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A) The boat foiled in a 5 mph wind.There is more to it then that: the wind was so light that the main hull would not have flown without the main and rudder foil working perfectly-no chance!
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B) the boat foiled in a 5mph wind at a weight of 21.13 lbs+ with just the main and jib. That is a major accomplishment because the main and jib have a combined sail area of 3390 sq.in. which is 160 sq.in/lb. The production RC foiler I designed 14+ years ago(F3) also foiled in a 5mph wind but she was 8lb with 1668sq.in. of sail or 208.5 sq.in. per lb.!
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C) This boat foiled using two completely different altitude control systems-for the first time on any size trimaran anywhere, as far as I know:
a. The main hull uses a dual wand controlled flap equipped main foil to help the boat fly in light air(see "A" above!) and to add righting moment in stronger wind,
b. The amas used a refined version of UptiP foils, pioneered by Team New Zealand in AC34, for the very first time on any trimaran anywhere as of July 24th 2014! My design for the Fire Arrow foils attempted to create a foil that would require little or no adjustment while foiling while keeping the ama flying as the main foil unloaded and the boat sped up. There are pictures showing this actually happening-"A" and "B" below illustrate the ama flying before the main hull while keeping the ama at about the same altitude even when the main hull flew-so these UptiP foils worked under two completely different load and speed cases-can't get much better than that. I think that the ama foils may have to have their AOI(angle of incidence) adjusted down during high speed sailing but we'll see down the line. No adjustments were made to the ama foils while making the last video.
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D) The foil configuration used by the Fire Arrow, as mentioned under altitude control systems above, is a one of a kind with tremendous advantages-particularly for an over square platform: thanks to the wand controlled main foil the boat will fly the main hull in very light air which would be impossible if one waited for the sail force from the rig to allow the main hull to fly. The significance of that is that the oversquare beam is not a hindrance to light air performance and adds tremendous righting moment in stronger wind due to the very wide platform. But, the main foil isn't finished yet: as the boat speeds up the main foil is unloaded but as soon as it is required the wand controlled foil will add righting moment to the boat equivalent to half the boats weight or more! It does this because as the apparent wind increases and the boat heels a little more the leeside wand reacts by raising the main foil flap and that causes immediate downforce(righting moment).
a. when the mainfoil is unloaded or creating downforce it "works with" the rudder foil in pitch control giving this platform tremendous resistance to pitch excursions compared to almost any other boat.
b. the main and rudder foil together control the ride angle of the ama foil so that it is incapable of any sort of pitch reaction on its own-either up or down.
This was one of the things so evident in the video and one of the great successes of July 24th.
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This doesn't mean the boat was perfect in the last video-I, as well as a few others, have pointed out areas that need work. We haven't sailed in strong wind with the boat working this well and there is plenty of work to do. But I wanted to take a few minutes and point out the things that were successfully accomplished on July 24th, 2014.

Pictures-see paragraph "C" above:

 

Here is an updated list of changes made since the first foiling video on July 24th 2014. Mainly minor changes that aren't experimental except for the i-Flap and #9.
So the major experiment for the next test sail is the port ama foil with the i-Flap removed compared to the starboard ama foil still using the i-Flap. There is a possibility that the I-flap can be removed on both foils as well as having total area reduced. Looking forward to foiling in much more wind than so far.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

One of the things that is extremely experimental that will be tested this year is the C-twist Surface Piercing T foil or "batfoil" for short. Initial testing will be on a cat and that will be with the whole foil developing vertical lift with the center section at about +3 degrees AOI and the tips, incorporating the i-Flap at + 6 degrees. The i-Flap portion is bigger than I think I will eventually need but the idea is that the boat takeoff early(5mph wind) and then reduce wetted surface.
One of the cool side effects of the shape for the cat is that the boat only has to heel 4 degrees before the windward mainfoil flies saving the hassle of a servo retracted foil. The cat is nearly finished-maybe another month or two.
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For the Fire Arrow this foil may be a replacement for the wand controlled main foil. A test foil for the Fire Arrow will be a little different than the cat foils: it will have an upside-down asymetrical section separated from the rest of the foil by fences. The point is to allow the new main foil to automatically develop downforce as the boat speeds up-may or may not work and losing the advantages of the wand in terms of angle of heel control, high pitch authority, ama foil ride angle control-may be a step too far. But its worth looking at closely-depending on how the basic foil works on the cat.

click for best view-

 

D4Z /AC 62RC Prototype

D4Z AC 55RC cat sails. Rig is reefable with reefing main and two jib sizes. Sail material is Dimension Polyant 2.2oz ODL. Top of the rig is a "WingTip" for masthead buoyancy and aerodynamic improvement:
click-

 

Refined in which way ? Is it different from the Nacra F20FCS or the Flying Phantom ?

I've seen Up-tips adjusted on the large 72's with complex hydrolics moving the foil case in the hull, but are they usually adjustable on these 20 footers as well ?

This confuses me - if the leeward wand is pushed up due to increased heel on that side, wouldn't that cause the main flap to generate an upward force, and isn't it an upward force on the main hull that would add to RM ?

Or, is it because the COE is to the lee of the center line thus a downward force on the main hull would be equivalent to a downward force on the windward side thus increasing RM?

Also, do main hull foils always need a wand to either side ?
And are these two wands controlling a single flap ?
And if so, don't they at times compete for control over that one flap ?

You're not saying that, when the mainfoil is creating an upward instead of a downward force that it is no longer "working with" the rudder foil to produce pitch control, are you ?

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By the way, how did your experiment with a single wand on the mainfoil work out ?

 

I tried to answer all your questions-if you don't understand something ask away.......

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Pictures, L to R, 1) Nacra UptiP main foil, 2) Flying Phantom UptiP main foil,3) Dario Valenza's sketch of TNZ UptiP foil,4) Illustration of two main C Class Catamaran UptiP foils used in the Last Little America's Cup in 2013. Generally ,the more "UP" the inboard tip the smaller the amount of adjustment. Hydros was actually a faster boat but their relatively "flat " foil was difficult to control and Groupama used that fact to help win the LAC, 5-7) Fire Arrow UptiP foils with curved inboard tip and "wash in"(as opposed to washout)-the inboard portion of the foil is twisted to help with light air/slow speed takeoff. To understand more about the experimental(but proven to work) i-Flap read post 1943 and check out the pages you'll be referred to:
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click for best view-

 

My mistake, it was the port side i-flap you removed.
By the way, why is it called (i)-flap ?

Thanks for your in-depth explanations.
Hope you don't mind, but i have another tough question - How did you calculate the placement geometry of the boat's four foils relative to the boat's center of gravity and center of effort ?

 

i-Flap=intrinsic flap. Refer to the pages above.
The boat only uses three foils at a time- this is the positioning process and the important thing is that one of those unloads so most of the load when flying is carried by just two foils.
1) Determine the final boat fore and aft CG,
2) Place the quarter chord of the main foil so that it will take 75-80% of the load and the rudder 20-25%,
3) Place the ama quarter chord about 2.3-3% of main hull length forward of the mainfoil quarter chord point,
4) As a check, the quarter chord of the main foil should be around 62% of main hull length forward of the rudder quarter chord point
5) The rudder hydrofoil quarter chord point and mainfoil quarter chord point should be slightly ahead of the rudder and daggerboard quarter chord points.
see pictures below
6) Once this is done place the rig on the boat. Generally, I use 25% of the chord of the main and wingmast balanced(for a rectangular planform) with the jib geometric center to determine the CE ,which on this type of boat I line up with the daggerboard quarter chord. I've used this method for more than 50 years and it usually turns out a well balanced boat.
You wouldn't use this method on a leadbelly. And finally, I look at the sail plan and its position on the boat and see if it "looks" right. Any questions I have may cause the rig to have a greater range of adjustment.

 

Thanks Doug, i appreciate your clear explanations.
i like the logic of your foil set-up and how that main foil/t-rudder interaction increases pitch control.

i'm finishing my boat shed, and will soon start an 8 meter wood/epoxy trimaran build based on Gary Baigent's 3 Devils design.
check; post #959, page 63 of the 'Alternative to the Marvelous Buccaneer 24 thread.

Do you think your foil set-up would get Gary's 3 Devils to at least fly the main hull without too much heel ?

Since my waters stretch from the semi-shelter of the Puget Sound to the wide open off Cape Flatterly, i'm not sure how practical a wing mast would be.

Is your foil set-up dependent on a wing-mast ?