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

Fire Arrow Foiler / MPX Foil System Testing and Development

More on the new surface piercing main foil(with downforce) : I'm thinking that it could have an application on a racing version of the Fire Arrow even w/o intrinsic downforce because it would drastically reduce the wetted surface of the main foil. And on a racing version, if downforce was wanted you could include a flap on the center section that you would simply "shift" to begin downforce.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

While I'm waiting for my crew to be ready, I'm working on the prototype for the AC 62RC(see the Projects and Proposals forum here or go to rcgroups and the AC 62RC thread).
One of the big successes so far with the Fire Arrow is how well the UptiP foils worked-they required no adjustment while sailing-none-zero.
BUT-when you start to plan how to use them effectively on an rc cat its a whole 'nother story! The UptiP foils on a cat MUST be retractable so you can sail with the windward foil retracted-I took care of that on the Fire Arrow by having high dihedral to the crossarms so the windward foil is just clear of the water with the main hull not flying-and clear of waves when the main hull does fly.
But not only that: you have to have a servo to adjust the angle of incidence of the foils as well. For instance, to take off the foil must be raked about 6+ degrees and right after takeoff the foil AOI must be reduced(raked) to 2-3 degrees.
That's not necessary on the Fire Arrow because of the i-Flap and/or twist added to the uptip portion of the foil.
All this radio adjustment on the cat can be pretty expensive not to mention adding a bunch to the foiling workload. So on my AC 55RC Proto(the AC 45 to the AC 62RC Class!) I'm going to be using wands on the mainfoils and I've decided to use two separate rudders to allow me to experiment with retracting the windward foil. Using a wand system means that retraction is pretty simple(though not real cheap) and a wand based T-foil system is likely to be almost as fast as an UptiP foil system with the windward wand T-foil retracted.
In the meantime the Fire Arrow sits forlornly waiting,waiting.........

 

D4Z AC 62 Prototype / rudder(s)

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Decision: I'm going with two rudders each with a T-foil. The mainfoil will take 80% of the load and the two rudders together 20% of the load. The area of the two rudders together will equal about 33% of the total foil area. So the rudder foil loading will be less than the mainfoil loading.
The deciding factor was my desire to experiment with retracting the windward main foil. If I had a single centered rudder and retracted the windward main foil there would be a new uncontrolled "axis of instability" formed between the central rudder and the lee main foil. With two rudders and the windward main foil retracted the pitch stability is excellent-no new "axis of instability".

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Ordered the sails today from Scott Morgan for the D4Z cat. They will be the same sails used on the Fire Arrow II (48" X 6' wide). Same material used on the Fire Arrow-Dimension Polyant ODL Technora-- 2.2 oz/sq/yd. The sail material is based on the fact that the new boats will do twice windspeed in a 5mph breeze and not normally sail below that.

 

Great stuff Doug.
Your pioneering work is taking model boat sailing into another dimension.
I notice that the rear main rudder foil is raised a little above the level of the main foil. Is that enough for it to avoid the turbulent wake from the main foil ?

 

Fire Arrow Foiler / MPX Foil System Testing and Development

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I crosses mine fingas and hope so! That kinda of wake turbulence can lead to ventilation but it's not so much of a worry on a model-probably something to do with Reynolds numbers. I patterned the mainfoil/rudder foil relationship after what was learned on the Moth and so far so good. When we get in stronger wind and start really moving we're likely to have a problem if we ever are. I'm not really concerned about it....
PS-Paddy, I hope it goes beyond models before its all over.....
PS2- The sail design for the D4Z/Fire Arrow II will use a large sock luff to make up for not having a wingmast-mainly to save money-the Fire Arrow wing mast made by Forte cost $300 and I already had the carbon tubes for this mast. We'll see how it works out.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

The surface piercing mainfoil with downforce(SPuD) needs to have a way to adjust the center upside-down asymmetric section independently of the outboard twisted sections. This is not a "mature" idea yet, but basically the hollow daggerboard will be fixed to the center section so the AOI of the center section can be varied by angling the daggerboard fore and aft(moving the bottom fore and aft for testing. Then the outside , twisted sections will be adjusted when the boat is set up on the table or maybe I can make a jig to allow adjustment at the sailing site. I'm leaning toward refining the concept so that the whole foil is laid up at one time, including the fences and pivot rods.
I think I can do it-we'll see.

click-

 

D4Z proto(AC 55RC)

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And this means I need to understand Ackerman rudder compensation ,specifically when both rudders are turned max for a tack or gybe, what are the degrees of difference between them. If the rudder on the inside of the turn is moved 38 degrees ,how many degrees should the outside rudder be turned? The reason the degrees are important is that each rudder will be hooked up to its own servo and I will program the Ackerman compensation into them both.

 

Next thing you'll be messing with tail/eleven mix? Haha


Barry

 

In car, you point the steering arm to middle of the other axel or in our case the middle point between the bows, just do it with the arms not programing.

 

AC 55RC-the "AC45" of the AC 62RC Class

Thanks, Jim.

 

AC 55RC-the "AC45" of the AC 62RC Class

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Barry, there are all kinds of mixes possible on one of these RC cats-lots of possibilities.

 

D4Z /AC 62RC Prototype

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More on Ackerman here: http://www.boatdesign.net/forums/multihulls/ackerman-steering-set-up-tips-racing-cat-51795.html
I've decided that on my cat the Ackerman will be adjusted on site for the conditions that day-even between races. The super radio I'm using on the Fire Arrow will be used on the cat. Problem is the "touch sensor" is the worst programming interface I've ever run into-I had a Futaba 8 channel "computerized" radio in 1985 that was easier to program! But maybe I'll get the hang of it when I do it more often.....

 

Fire Arrow Foiler / MPX Foil System Testing and Development / D4Z

This is something I learned a long time ago and it works real well on RC monos, in my experience. It is something I'm going to address later on the Fire Arrow-probably with a carbon Hoyt jib boom. I mention it here because I'm working on the D4Z AC 55(proto for the AC 62RC) and am going to incorporate either a sliding jib pivot or a Hoyt jib boom.
Here is a sketch of the idea applied to a cat but the principle is the same for any RC boat and makes a noticeable difference in pointing ability:

 

D4Z /AC 55RC--proto for AC 62RC

Heres the boat with some black paint/primer in selected areas:

UPDATE-11/11/14---Curved Twisted Surface Piercing T-Foil---A potentially significant breakthough in RC model foils happened accidentally when I took a sketch of the new experimental Fire Arrow foil(post 1837 and others) and laid it out on a full size drawing off the D4Z: for use on the cat the foil would not have the fences or downforce section the Fire Arrow version has and I found tonight that if the foil is canted 10 degrees outboard the windward foil will clear the water with about a 6 degree angle of heel. What this means is that instead of using wands or UptiP foils with a retraction and rake servo for each foil, the new foil will automatically "retract" when the boat heels just a little and not need rake adjustment by radio(maybe). The potential is incredible and I will use this system on the cat.

click--