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

SRT> FireFlyer X18

Well, what a year so far. From this model to the 16' Eagle-too much money, to the Dream Flyer-too hard on me physically after disaster #2 and on to the Crossbow fl(see thread here: http://www.boatdesign.net/forums/sailboats/crossbow-fl-43615.html ) that is highly likely to be built just after the first of the year. And I've just nearly finished the Crossbow model and have taken it to Matt McDonald so he can go over what has to be done on the fullsize build carefully.
So, while I have a little time I've decided to get back to this model albeit with some changes:
1) Initially no longer "self-righting" though the model will be able to be converted later to test that concept just as originally planned.
2) Major focus right now(rest of 2012-and while the Crossbow is being built) will be to PROVE the viability of the MPX foil system beyond a shadow of a doubt.
Elements of the MPX Foil System( Max Power Xperimental):
a. Early takeoff of a very wide trimaran. An 18 foot trimaran 22' wide has a tremendous "natural" righting moment that works against performance in light air by preventing the mainhull from flying. The MPX system uses two lifting foils on the main hull to allow the boat to fly the main hull at 5-6 knots of boat speed drastically reducing drag and allowing great speed. As soon as the main hull lifts off the foils begin to unload as the heeling force contributes more toward flying the main hull. The main foil uses an altitude control system(wand) that automatically keeps the boat flying at a minimum angle of heel. Target range: 10-13 degrees. The wand can also increase RM as required by causing the main foil to pull down for the duration of the gust.
b. Ama foil-the boat uses a retractable curved ama foil on a very small ama(10' for an 18 footer). The curved ama foil gradually carries more of the load as the main foils unload until it carries most of the boats weight. The main foils continue with their primary mission after early takeoff: pitch control. The two foils acting together give the boat tremendous pitch control-much more than any "normal" trimaran-and this keeps the ama foil running at the correct angle of attack. By having most of the load on a single foil the total induced drag is reduced significantly.
3) The new model will have a new main hull because the SRT hull was based on a hull I had(with a modified bow). The new hull will have less light air wetted surface and will be much lighter and quite narrow. This model is designed for one thing: high performance while proving the MPX foil system. I believe strongly in this system and think it can change the way small tri's are designed allowing for significant performance increases while allowing very low crew weight requirements because of the stability and high pitch control of the foil system.
It will allow an 18' tri( or any tri from 11-12' up, for that matter. see http://www.boatdesign.net/forums/multihulls/mpx-11-very-small-high-power-trimaran-33686.html ) to be a beachcat killer with one or two crew sitting on the side of the cockpit with very little movement required.
So you have high performance in an easy to sail boat that is not demanding physically and that is made possible 100% by the foil system.
Stay tuned.

 

Fireflyer X18 Model

This is a concept ,shown in the very rough sketch below , that is inspired by Hydroptere.ch. They use a pivoting bow that creates a step in the planing surface. That(the pivoting bow) allows the hull to have less drag in light air when the step disappears. The idea here is to use a stiff ,thin carbon sheet ,pivoted forward,
to create a step. The flat carbon piece is pivoted back to reduce drag in light air. It would be simple to try and might be worth it...

click for better detail especially on second picture:

 

SRT: The Test Model

Well, I'm back on the model for a while. Before I go further, I've changed again and post 226 ,about a different main hull, is wrong. Going to use the main hull originally designed for this purpose. Main emphasis initially is, as stated in post 226, to test the MPX system. Sometime in the next few months I'll have to stop again for about a month or two. I'm working with a very reduced capacity for standing or sanding so the boat will continue to make slow progress.
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Today, I ordered the radio and servos from Radio South(see pdf below) in Georgia. I've known Tony, the owner, since the 80's in my video piloted helicopter project. The radio is basically a programmable helicopter transmitter and receiver on 2.4 ghz. It transmitts using "frequency hopping spread spectrum"(FHSS) which which eliminates interference caused by my transmitter or by someone else on another frequency.
It eliminates the difference between "surface frequencies" and aircraft frequencies" and can be used to fly in air or on water.
Each channel has servo reverse and end point adjustments which makes set up very simple. I'll have enough channels to set up manual foil control if I need or want it, mast rotation for the wing mast, and camera control if it works out.
Tomorrow, I'm going to get the rest of the supplies I need for the final carbonation of the curved pieces, assembly and foils.
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I've found a carbon section made by Offshore Spars in Detroit that is a perfect wing mast section with a 2" chord. They aren't sure they can make it as long as I need it-even in two pieces. I should find out tomorrow. If they can't do it I'll probably try Forte and/or just use a .75" carbon tube 84" long.
I'll post the model sail plan(a little different than full size-equivalent to 216 sq.ft on an 18 footer) in a couple of days. It is reefable and matched to the boats RM up to 2lb per sq.ft.pressure.
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The ama foils ,initially will be a variation on a T-foil but with no altitude control system. More shortly. The main foil will be an altitude controlled T -foil that will control main hull altitude and therefore the sailing angle of heel of the boat. The system will use two carbon planing wands ,first pioneered by Dr. Bradfield.
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I hope to update frequently and I want to get as much done as possible in the next few weeks.

click for larger picture:

 

MPX-test model

Working to try to use a carbon wing mast, but thats a lot harder then it sounds because there is almost nothing that works at this scale. It occurred to me that several companies offer carbon spreaders and if the section was constant it might work. Got one quote so far-$370 with 14" of the top section being tapered-but the wrong way: the front of the section is straight and the back side is tapered. Would be a 7% wing mast. I may still be able to use it. But the money is stretching a point. I can get a round carbon mast for $100.
One other company is going to get back to me in the next day or two-we'll see.
Have to have the mast before I can order the sails.....
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SRT-MPX test model

Well, I got lucky! The first place could make the mast but it would have been in three pieces which I would have to join for 370 + shipping. Forte Composites will make the mast(from a spreader tool) in one piece for $300 plus about $50 for shipping. Forte-Clint and Tony-are a pleasure to deal with. These guys always go the extra mile to help the customer.
Wall thix will be about .035--.04" for a weight of .8-.9lbs. which is perfect. The wing mast chord will be about 7% of the mast+ sail chord.
I'm so glad that this worked out.

Sketch: this is the actual section shown with its "normal" wall thickness of .12(about 1/8") and weight of .367Lbs/ft. Forte will make it much thinner(as above) with a weight of about .122lb. per foot or about .87lb for my mast:

 

Mpx-srt

I've redesigned the ama foil to move the center of lift closer to the ama so that it would be as outboard as possible and retractable. I originally was going to use just a curved lifting foil but the center of lift was too far inboard. The ideal configuration, to take full advantage of the beam of the boat, is a t-foil but there is an additional requirement of the foil: it cannot use an altitude control system(wand).
So, having been inspired by the design of Team New Zealands foil on their 72, I have basically done a variation on a T-foil( "bent T-foil" ) but designed so that speed will control altitude within several ranges that are adjustable by raking the foil top fore and aft. I'll be able to do this with the radio but I'm going to try setting it up manually at first. I'm also going to look at designs that maintain this function but will be simpler to build. Depending on the tradeoffs the design could change but I'm satisfied that this is fairly close to right.
One other thing: most foiler main foils lift about 80 % of the weight of the boat, but this ama foil(which acts like a main foil when fully loaded) will carry nearly 100% of the load with the two foils on the main hull mostly unloaded except that they will control the pitch of the whole boat.

Here is the rough sketch made to test out the concept. The red line is the nominal flight waterline at 10mph and a .3 Cl(Coefficient of Lift) :

 

SRT/MPX Test Model-Sail Area

The final sail area for the model will be 17.83 sq.ft(2567.5 sq.in). Max pressure for that SA is .5lbs/p-sqft. That means that a wind that cause a half a pound of pressure per sq.ft will require the maximum RM(Righting Moment) of the boat which is 36 ft.lbs.
Even though this area is reduced from the full size about 24% thre is no way to sail throughout a wind range to 20 knots w/o either multiple rigs or a reefing system. Many expensive racing model sailboats have up to 5 separate rigs. I solved the problem on the boats I used to produce by having a reefing system.
Summary:
A-Total SA=17.83 sq.ft.(2567sq.in), Max Pressure .5lb per sq.ft., CE 4'
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B- Reef Configuration 1- remove the jib and move mast forward slightly.
17.83-5.2sq.ft(jib) for a reduced area of 12.63 sq.ft..(1818 sq.in),
Max Pressure= .63 lb. per sq.ft., CE 4.5'(CE goes up when jib removed)
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C- Reef Configuration 2- remove jib and roll lower panel of main.
17.83-( 5.2jib + 2.72 lower panel)=9.91 sq.ft(1427 sq.in),
Max Pressure= .95lbs per sq.ft., CE 3.83'
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D- Reef Configuration 3-remove jib and roll both lower panels of the main.
17.83-(5.2jib + 2.72 + 2.72)= 7.19(1035sq.in.),
Max Pressure= 2.07 lbs per sq.ft., CE 2.42'
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The reefing system is pretty simple. The sail is held on to the mast by very small plastic tubes. A wire runs down the aft side of the mast thru the tubes with velcro strips holding the sail to the wire. The luff pocket is cut away for the two lower panels so the sail can be rolled. Round velcro patches are put on the sail for the second and third reef configurations. To reef the main the lower panel or panels are rolled so that the round velcro patches retain the sail . Then the "halyard" clip is undone and the sail is lowered after the upper velcro strips are loosened. When the halyard is at the lowered position the small strips holding the wire to the sail are refastened .This can be done pretty quickly and allows the boat to sail in a wide range of wind with just one rig.

---The picture below shows the velcro patches(see white arrow) that hold the rolled sail. The boat in the picture had only two reef configurations:

 

How is your testing of the 14' going?

 

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The Crossbow fl is indefinitely delayed due to my back injury. Should have the operation in 2-3 months and then a long recovery. Unlikely anything will get done on the boat this year. I will try to get as much done on the tri as time- and my back- permit. Thanks for asking.
See post 86 in the Crossbow thread. http://www.boatdesign.net/forums/sailboats/crossbow-fl-43615-6.html

 

Doug,

I am confused. I thought in a different thread, now closed and hence my asking here, you had mentioned near term testing 6 or 8 years ago?

Sorry about the back injury. Recovery depends upon many variables. Some people go golfing within a week of fusion. So, don't let it scare you too much. Remember, all the anti pain meds cause severe constipation in most people - take a lot of fiber and water.

Recovery is usually better with heat than with physical therapy .... been there with many people. Not what the medical community will usually tell you.

If you are over about 55, the surgery is much more risky, your body does not heal very well.

I will pray for you.

PS .... if you need the surgery, sooner than 3 weeks is better than 3 months. The longer you wait the more permanent damage is done while waiting.

 

6 or 8 years ago I had finished testing a 16' foiler. But the only 14 I've worked on in the last couple of years has been the Crossbow. Surgery is out of my hands-I go when the surgeon is ready within the framework of Florida Voacational Rehab.
Whats the name of the closed thread?

 

I don't remember the thread.

VocRehab is always a pain.

How did the 16' foiler test out?

 

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It foiled but poorly with some control system issues. The bow produced a lot of drag in short intercoastal waves delaying takeoff. The rig worked well. I learned a lot from the boat. The hull is being used on the test model(the subject of this thread)-with an altered bow.

 

Interesting.

Are you wave riding, or wave piercing with your bow?

 

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Which bow:

Pictures L to R starting at top: 1) Test model bow-in air most of time, 2) test model amas-planing and wave piercing-designed for incidental contact-not sailed "on" on a regular basis, 3) Test model at earlier stage-illustrates shape well, 4) 16' foiler hull-same hull as model except bow changed and boat lengthened, 5) 16' foiler,
6) 16' foiler-no foiling pictures.
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Test model will fly the main hull in 4knots of wind(full size 5-6 knots wind)