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

Foils

Thanks. What is the percentage of total weight carried by the two main foils?

 

This is foil loading for Skyfall and F3 in both units of measurement for each boat:
Skyfall
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Sailing Weight-4.4kgs(9.24lb)
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Max SA- .9sq.m (1393.2sq.in.)
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T Foil area-one foil + flap- 44sq.cm(6.93sq.in.)
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Foil Loading*-4.2kgsX.8=3.36, 3.36/2=1.68kgs(one main foil),
1.68/44=.0382 kg per sq.cm.(.534 lb per sq.in.)
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CL to CL main foils=118cm(46.46")
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*Both boats figured at 80% of the load on the two main foils. If I get different info for Skyfall I'll correct it.
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F3
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Sailing Weight-8lb(3.6kgs)
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Max SA-1668 sq.in(1.08 sq.m)
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T Foil area-one foil+flap-17 sq. in.(109.68 sq.cm.)
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Foil Loading-8lbX.8=6.4lb,6.4/2=3.2lb(one main foil),
3.2/17=.188lb per sq.in. (.013kgs per sq.cm.)
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CL to CL main foils=60"(158.38cm)

 

Fire Arrow Foiling System Testing and Development

Test Model and Foil System Specifications---latest update: 9/11/15

A) Name- Fire Arrow

B) LOA-79" (6.58')-including bowsprit

1. mainhull-66.19" (5.52') (The reasoning behind and the story of the added hull length can be found in posts 1177,1187-88,1195-1198)4/30/14
2. mainhull+ rudder and gantry(no bowsprit)- 69.125" (5.76')

3.planing portion of ama=34in. (2.83')

4.ama LOA=50.75in.(4.23')

C) Beam-81.6"(6.8')

D) Mast 103in. (1.75"chord wing mast / 8.58')5/1/14
E) Sail Area:
1. Main+ Mast + Jib= 3390.9sq.in.( 23.5 sq.ft.)5/1/14

2. Main+ Mast + Code Zero=4087sq.in.(28.38 sq.ft.)5/1/14

3. Main(reefed) + Jib=2767.4 sq.in.(19.2 sq.ft.- current sailing configuration)9/11/15

F) Foils:

1. Mainfoil(wand controlled flap)-Span=23.75in., Area=79.4sq.in.
a. Daggerboard span-12.625"
b. Daggerboard area-41sq.in

2. Rudder foil-Span=22.75 in., Area=50.6 sq.in.
a. Rudder span-10.75"
b.Rudder area-28.9 sq.in.

3. UptiP ama foil(One used at a time,except at takeoff. Inspired by TNZ with refinements that will allow a wide speed range w/o AOI adjustment. Works with and without leeway coupling)-9/11/15
a. Span(from bottom of ama)=20.625 in.,
b. Area(from bottom of ama)=68 sq.in.
a. Vertical portion-24 sq.in.
b. Uptip portion-44sq.in.
c.Projected lifting area at max loading: 47.5sq. in.

G) Weight- 21.13lb. 5/1/14

H) Foil loading at takeoff*(75%= 15.85)=.199lb/sq.in.9/11/15
* foil loading is actually less: at the early stages of takeoff both ama foils lift a little. Right at takeoff the ama foil
adds about 44 sq.in. with very low loading , reducing overall foil loading slightly.(F3 was .188lb/sq. in.) After takeoff, the main foil begins to unload as pressure builds on the rig reducing mainfoil loading significantly. The ama foil begins to carry the majority of the load(max loading about 85%=17.96lb.=.378lb/sq.in).

I) SA/Lb(21.13lb displ ) with Code Zero=193.4sq.in.,with main +jib=160sq.in(F3-208.5)(more=better)5/1/14

J) SA(incl Code Zero) per sq.in. of mainfoil group area(89.125sq.in) at takeoff=45.85 sq.in./per sq.in.(F3-49 sq.in/per sq.in)(higher=better)5/1/14

K) SA/WS(with Code Zero)= same as F3 after takeoff--7/1 seahugging, 12/1 foiling(max SA).9/18/15

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FIRE ARROW FOIL SYSTEM
--added #6 below 12/8/13 and modified 12/9/13
--added to #3 below on 12/13/13
--added f.,g.,h. and i., 5/1/14

Here is a brief summary of what makes the Fire Arrow Foil System unique and why that is important:
1) The boat has four foils total. On the fullsize version, only three foils are used at any one time. On the model, since the ama foils will not be retractable(at least initially), they both contribute to vertical lift at take off with the majority of lift coming from the main wand controlled foil and the lee ama foil.
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2) Here are the unique characteristics of the ama foil:


See page 73, post 1090 for much more on the theory that applies to the unique ama UptiP foil. It has just been updated with a link to Dario Valenza's experiments on A Class cats with "uptip" foils where he found that the foil will function w/o leeway coupling for heave stability --using the breaching of the inboard tip for altitude control when leeway is low.


a. The Uptip ama foil is designed to only lift vertically(no downforce) and horizontally,
b. The ama foil is targeted to perform throughout the speed range with no adjustment. It is anticipated that the angle of incidence may have to be changed once, as speed increases, if it is changed at all.
c. The ama foil is designed to carry 80% of the weight of the boat with the rudder foil carrying 20%. The ama foil loads up as the mainfoil unloads.
d. The ride angle of the ama foil is controlled by the action of the main foil and rudder foil together.
e. The ama foil was inspired by the new type of foil designed by Morrelli and Melvin for TNZ except that this foil has a wider range of speed before angle of incidence adjustment might be required.
f. The ama foil angle of incidence of the vertical lifting "L" portion of the foil for the first sail is 3.75 degrees relative to the static waterline.5/1/14
g. The ama foil angle of incidence of the vertical portion of the foil is set at +2.25 degrees, relative to the boat centerline, for the first sail. This will unload the daggerboard and provide leeway coupling to help with altitude control.5/1/14
h. The main foil angle of incidence for the first sail is +2.5 degrees relative to the static waterline.5/1/14
i. The rudder foil angle of incidence for the first sail is zero degrees relative to the static waterline.5/1/14
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3) The main foil has a flap and the flap angle is controlled by a wand*. This allows the boat to fly the main hull in very light air which is a big advantage for an oversquare trimaran-particularly a tri under 20' which would, likely, not be able to fly the main hull in these conditions. As soon as the main hull lifts off, the boat accelerates to roughly twice windspeed in a 5mph wind. As the boat speeds up and heels, the mainfoil unloads as the wand causes the flap to rise. At a certain point the flap causes the main foil to not produce any lift with all the load automatically shifted to the ama foil. If the main hull rises above this point(about 10 degrees angle of heel initially), the flap will continue to rise causing the main foil to create down force(unless this facility is disabled). When the main foil is developing downforce it is also developing lift to weather, similarly to the lift to weather when a Moth is using Veal Heel(except on this boat it is a function of the "normal" heel of the boat and the downforce on the mainfoil). See post 532 for an illustration of how this works.
* The boat actually has dual wands but they act on a single axle acting as a single wand.The reason for that is to allow the wand to work when the boat is heeled. The lee wand is nearly vertical(viewed from forward) when the boat is heeled 10 degrees and acts to maintain an angle of heel of about 10 degrees and an altitude of the main hull of about 3". See the sketch below showing the heeled waterlines. Also see posts 512 and 514 for more on the wand system. See page 40, post 597 for a video of the MPX wand activating the main foil flap.
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4) The rudder foil is a trailing foil that automatically develops 20% of the lift required at takeoff, then gradually unloads until it begins,again automatically, to pull down.
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5) As best I can tell there is no other trimaran in the world using a foil system like the Fire Arrow Foil System. Having a wand controlled mainfoil on the main hull and an ama foil that flies the ama(nominally a few inches above the water) with no control input other than that of the leeway coupling component of the foil and the effect of leeway on the "L" portion of the foil(however small) is a significant development for full flying trimaran foiling systems. The whole foil concept is significant because:
a. it allows an oversquare tri to fly the main hull in light air,
b. it unloads the mainfoil allowing it to become,with the rudder, primarily a pitch control system which controls the running angle of the ama foil.
c. it allows the mainfoil to contribute to righting moment with downforce,
d. it allows the mainfoil to develop lift to weather when it is developing downforce.
e. the deep main foils acting to control pitch prevent the main hull from bottoming out and allow the angle of heel to be varied between approximately 10 degrees and 17 degrees(or a bit more) by adjusting the wand length.5/1/14
f. the planing ama design serves as back up in rough and/or gusty conditions when the foil might be momentarily overpowered.
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6) Speed- Top end speed is NOT the priority of the Fire Arrow Foil System-light air speed resulting from the unique ability to fly the main hull in light air is. The Fire Arrow Foil System's main claim to relevance are the two lifting foils on the main hull which allow an oversquare platform to fly the main hull when a wide trimaran,particularly 20' or under, w/o these foils would not. To make a 1.2-1.3 oversquare tri fly the main hull (without foils) requires excessive sail area(or wind) and impairs the pitch stability of such a boat . The two main foils work together to provide pitch stability way in excess of any "normal" trimaran and control the running angle of the planing ama and ama foil. The system should work well with a planing ama using foil assist and does work well in light air, so far, using an ama foil that allows the ama to fly when the main hull does(the current test model configuration).5/1/14
Top end speed is enhanced by the initial configuration being tested which has the light air advantage intrinsic to the system with the added speed potential in heavy air due to the reduced ama wetted surface and the fact that the main foil will develop downforce adding to the righting moment. Further, the foil that flys the ama is designed to support 100% of the boats weight as the boat speeds up, unloading the mainfoil and reducing drag substantially.

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>Preliminary testing has encompassed testing all foils to 3 times their calculated maximum load(estimated 150% reserve above that before breaking).

> Boat was originally designed as a scale test model of an 18 footer based on a full size hull I used to have(donated to a friend).Since the stern extention it is longer.4/30/14

>See post 1242 that confirms the ability of my first foiler design(F3), about 15 years ago, to do foiling tacks and gybes!5/9/14

 

Ian, some idea's that may help.
1. set the flap so that lift (wand up) has 2 degrees and wand all the way down, has -4 degrees to allow for the 2 degree fixed in the strut for a starting point.
2. the wand "may" be too short to develop enough leverage force at the foil, although your gearing looks about right.

Congratulations, you are probably 90% there already!!

 

Jim, the foil with flap neutral should be set for +2.5 degrees AOI. At takeoff the wand tip should be max back and up with the flap at 30 degrees down. For downforce, max flap up(wand tip down and forward should be) 20 degrees.
The spring or shockcord should be set up to apply more force to the wand via the rocker arm when the flap is max up since , at that point, it is the only force resisting water pressure. W/o the right tension there will be no downforce....
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How are you coming with your boat?

 

Thanks Doug, I was trying to show an example of the theory if you have +2 degrees in the strut you will need an extra -2 degrees in the flap to compensate for the strut setting.
But in your example above, you are using 10 degrees less up flap for RM anyway. Is that because shock cord limitations? That is one of the areas I am trying to address with my incidence controlled foils as opposed to flaps.

I have discovered that fleet racing model sailboats is just as dangerous as racing the full size ones. while walking along the shore following the boats (Solings) in a 12 boat heat I stepped in a hole and twisted my left knee badly. For the next two weeks I tried to keep moving as much as possible compensating with my right knee
and shoulder muscles. BIG MISTAKE! The right knee and both shoulders locked up!
and resulted in hospital visit and so far 2 months limited to walking no more than 20' at a time.
The boat was supposed to be sailing by now, it has been assembled for fit and is now disassembled for paint.
Hopefully I will be able get paint on it before the weather turns really bad here so I will be ready to go in early spring.

 

Jim, that's a drag! Its tough getting older. My projects have all been delayed by health related trouble several times. Good luck recovering!
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Flap up 20 degrees for downforce is what Bradfield used and what I used on the F3 and Fire Arrow. I haven't tried more "up" because it hasn't been needed-and would increase the force requirement on the spring. You can increase downforce with the 20 degree up flap by "shifting gears" to remove the +2.5 degrees AOI from the foil. But that adds unnecessary complication on an "automatic" rc system but might be worth setting up on a race boat. The only potential limitation I see with incidence controlled foils is altitude. The Hobie trifoiler flys really low and even then has gigantic "feelers" sticking out forward. If the flight altitude is too high it probably affects the control system much more than would be the case with just flaps.

 

Fire Arrow Foiling System Testing and Development

Fire Arrow planing ama: (STB UptiP foil still has iFlap-removed from port ama foil)

 

Fire Arrow Foiler / MPX Foil System Testing and Development

Fire Arrow foils with a little D4Z Batfoil thrown in:

 

Fire Arrow, "Z" and now a foiling keelboat

For the time being the Fire Arrow and D4Z are awaiting further testing so I've decided to build an RC foiling keelboat based loosely on the Quant 23. You can follow progress on rcgroups starting with post 19 : http://www.rcgroups.com/forums/showthread.php?t=2434531&page=2
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The Fire Arrow remains the number one priority but so far I haven't found the help I need to sail her. The D4Z is the second priority and while I'd like help for the video I can take the "Z" out myself which I will as it cools off.
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One more thing: I've talked to some people about going ahead with a crowdfunding campaign to build a fullsize version of the Fire Arrow-two of them have committed to help! But first we need THE VIDEO with much more foiling than on the first flying video. Hopefully, that problem will be solved soon........
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The fullsize Q23-the first foiling keelboat in history:

 

Hydroptere Test Models and more...

There is only a short glimpse but you can see an early RC Test Model(2:06 in) of Hydroptere in this video plus their 1/3 scale model and more great Hydroptere video:
https://www.youtube.com/watch?t=35&v=36PRnNBuN9I

 

Interesting model on Youtube

https://www.youtube.com/watch?v=6m3AMOKnCkI

 

RC Multihull

Yeah, it is. Just wish the guy had some video shot from outside the boat.

 

SNAKEfOIL for tri's or cats

Steve Clark came up with a new kind of foil or should I say a new application for an old kind of foil. Surface piercing foils have been around forever but have always been used in pairs with a single rudder T-foil. Steves idea for a cat is to use a single surface piercing foil on the lee side with the windward foil retracted in combination with two rudder t-foils. His initial version was also designed to fly the boat relatively close to the water-but it doesn't have to work that way. The difference between this configuration and an UptiP foil configuration is that the surface piercer controls altitude by speed and can always operate at the optimum foil area where an UptiP foil controls altitude with leeway coupling(with a sort of back up from the inboard foil tip). A properly designed UptiP foil will maintain a steady altitude, for the most part, and a SnakeFoil will change altitude with speed automatically. The UptiP foil will have the center of lift a little more outboard than the SNAKEfOIL.
Using a snake foil has the potential of real gains to windward since a component of it's lift is always to weather so it is definitely worth experimenting with in the AC 4.8(50?)RC wannabe class or on the Fire Arrow down the line.

 

Model Testing

There has been some discussion of the value of test models being used in the development programs of fullsize boats. Interesting to see Oracle and BMW doing model testing in a windtunnel.See post 300 here: http://www.boatdesign.net/forums/multihulls/35th-americas-cup-foiling-multihulls-48428-20.html