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

Well it depends a bit on the batten design in the square head, but the reason for squareheads is more than just trying to get unrated sail area. They are really more of an effort to get an elliptical tip shape so as to reduce spanwise flow as well as to move sail area up into stronger and more stable air flow.

True and untacked batten is slow - in fact 49ers take advantage of this on starting lines by intentionally inverting the battens in their main to essentially "heave to".

but as you said, that has to do with a bad loading of the batten tensions. Yes they are a bit harder to design, but all a gaff is, is an external batten that generates more drag and puts more weight aloft. And its not so much that they help keep shape "in breeze" - rather what they allow a sailmaker to do is to cut a fuller shape that has the power necessary for lighter wind, butt which relies on the battens to keep the shape in bigger breeze.


Take a look at the size of Doug's sail. its the size of a small windsurfer sail. and none of the modern windsurfer sails are battenless. So in the case of the MpX tri, this isn't a small sail. This is a full on dinghy sail. Note also that Doug's design expectation is that it will liftoff and double its AWS in 6 knots of breeze. So assuming that the boat is already moving at atleast 2 knots of hull speed at takeoff, the AWS after takeoff will be 1 knots. that's well within the "in breeze" range you are talking about. In fact assuming doug's boat performs as he intends, that fast switch from a 7knot AWS to a 15 knot AWS is exactly what full length battens are good for: stabilizing a sail shape across a wide range of wind speed.

To my eye, looking at the sails in the photos you link, #49 seems to have draft too deep and too far aft once it starts flying two hulls.... your last two photos have full batten sails looking quite good . Which speaks to exactly the phenomenon of sail range I'm invoking

 

Ian also check out the last post here for more info.

 

MPX Test Model / Sails/ Rig

May be able to make up the jib and Code Zero shortly. Both will be attached to the spectra strop by snaps so they can be easily changed out. Each will have an integral wire forestay and their own boom with an adjustable outhaul and adjustable boom pivot point(located at 20% of foot length aft of jib/CZ tack). The Code Zero will be attached to a removable(may change) bow sprit. And the sheet will be the same for both(I hope).
The aluminum mast step will be installed directly to the deck and should be long enough for sailing with the mast at the forward end to allow sailing w/o
the Code Zero and jib.
The jib uses a modern version of a gaff to support the "peaked-up" squared off jib head. The gaff will allow for an upper outhaul which, like on the main, allows for much greater control of sail shape than otherwise possible. No full length battens(improves performance throughout the wind range but particularly in light air). See post 926, page 62 for a whole series of RC designs of mine -all using modern versions of a gaff. Extensive testing with and without the gaff was done(same sail areas) with the gaff proven conclusively to be superior in the tested boats.
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I'll tell you: since finishing the main+mast and taking it out in a light wind I'm extremely impressed with the power of the thing. And despite the extensive calculations I've done I wouldn't be surprised if this thing foiled on the main alone-even in relatively light air!

 

My T foil rudder is the same size as one main foil.

 

RC Foiler Stats

Thanks, Jim. Can you come up with the SA/ws foiling and not foiling when you get a chance.

 

RC Foiler Stats

I want to thank Curtis Luxton publically for his inspiration to do these stats and for his help as I got bogged down! Thanks, Mr. Luxton!

 

MPX Test Model-Review of Wand System

On this test model wand system is virtually self-contained on a single carbon plate. There are two wands, one on each side, designed to allow only one wand to be in the water(most of the time). The lee wand is more or less vertical when the boat is at it's sailing angle of heel(between 10 and 17 degrees). For sailing at more angle than 10 degrees the wands need to be extended-originally they were going to be adjustable but I decided to test at 10 degrees first.
The dual wand axle is retained with delrin washers on each side and carbon tubes act as mounts. The bellcrank/rocker arm for operating the main foil flap pushrod is glued to the center of the axle. The short end connects to the pushrod; the long end connects to a spring which is used to hold the wand against the surface of the water-tension is adjustable. The whole wand mount plate also serves as the attachment point for the main foil. The wand plate retaining bolts allow the plate to slide fore and aft making adjustment of the angle of incidence of the main foil a piece of cake.
Each of the wands has a small "paddle" on the end-the basic idea was invented by Dr. Sam Bradfield to facilitate planing which acts as a way to dampen wand movement and improve response. Many modern Moths have adopted something like a paddle on their single wands.
A fairly detailed description of how the wand controlled main foil fits in as part of the MPX system under "MPX Foil System" on page 64, post 946.

click for better view:

 

doug, something is only considered an "invention" if it is not "obvious". making a paddle wider to increase the force that the arm can convey is "obvious" - and evidence of this can be seen in how that approach is "re-invented" many times over

 

MPX Test Model-Review of Rudder and Rudder Gantry

The rudder on the test model is mounted(adjustably) to a tube that slides into the rudder gantry mount. The gantry mount is well carbonated to the aft deck and transom. The rudder tube is held to the tube removably by a 6/32 bolt which allows the rudder to be removed for transport. The rudder pushrod comes directly from the radio box and may be removed for transport then easily and quickly re-attached for sailing. The attachment point for the pushrod on the rudder is made of carbon sheet carbonated to the rudder -very strong.
The purpose of the gantry assembly is to allow movement of the rudder hydrofoil as far aft as possible which can help with pitch stability. It is designed so that it can be adjusted to any point within the range for testing.

Pictures: 1)-2) show rudder angle of incidence adjustment range, rudder tube and gantry mount, 3) plan of gantry rudder box attached adjustably to the rudder tube-together they comprise the gantry which is adjustable fore and aft,4)-5)-finished system minus push rod:
click-

 

Please stop using the slly term "carbonated". it means nothing and frankly sounds ignorant

 

Carbonated means liquids (water) charged under pressure with CO2, to form soda water. (ie: Whisky and soda)

For our purpose-----Carbon composite,
ie: Carbon/epoxy, as in, perhaps---- foam/carbon/ epoxy sandwhich.

 

But that's the point. There are already perfectly adequate and industry standard terms for this: as in

See that's actually a meaningful description of a construction process. "carbonated - which as you point out means liquid charged under pressure with CO₂ is meaningless in the context of building boats or models or using carbon fiber.

It conveys nothing other than perhaps a desire to try and force a new usage.

 

I thought carbonated was a light hearted amusing little term.

But then my mission in life isn't to follow Doug around forum to forum relentlessly looking for fault.

 

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Paddy, my stalker knows exactly what I'm saying. I've used the term for three years or more in this thread and for 20 years in "real life".
Used to do a lot of glass work and when you finished the job you said it was "glassed". When I started using carbon, I used "glassed" until I realized that another term would be better so my version of the carbon/epoxy word for "glassed" is carbonated or carboned. I prefer and will continue to use carbonated. I've heard others in the business use it as well.......
Has a nice "ring" to it......

 

RC Master Stats

Ians boat is actually sailing, Curtis's boat will sail soon, the F3 sailed for years(and a couple or more are still sailing) starting 13 years ago, Jims boat is not too far off, and the MPX Test Model may not be too far off:
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Some stats for comparison with other RC foilers:
F3 (sail area to wetted surface corrected 2/6/14)
1) SA/lb.-208.5 sq.in/lb.
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2) SA per sq.in. of main foil area-49sq.in per sq.in.

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3) Foil Loading-main foils at takeoff=.188lb/sq.in.
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4) Foil areas:
--main each 17 sq.in., total 34 sq.in.
--rudder 17 sq.in
--Bradfield wand altitude control system
5) Specs:
--LOA-56" / 1.42m
--Beam 72" / 1.83m
--Weight 8lb. / 3.64kg
--Sail Area 1668 sq./ 1.08sq.m
--SA/ws not foiling=7/1, foiling 13.6/1
==========================
MPX- (sail area to wetted surface corrected 2/6/14)
1) SA/lb--235sq.in/lb. (with the Code Zero)
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2) SA per sq.in of main foil(s) area = 45.6 sq.in per sq.in foil area.
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3) Foil Loading at takeoff= .189lb/sq.in. (18lb displ.)
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4) Foil Areas:
-- --mainfoil+ama foils at takeoff-95 sq.in(at least initially, model windward foil will not be retracted at takeoff-on full size it will be)
/combination wand and Hybrid "L" + curved foil altitude control.
--main foil 39 sq.in
--ama foil,each 36 sq.in. (to bottom of ama)
--rudder foil 29 sq.in.
5) Specs:
--LOA-72"(main hull 60.75") / 1.83m(1.54m)
--Beam -81.6" / 2.07m
--Weight 18lb.est / 8.18kg
--Sail Area 4244sq.in.(code zero)/ 2.74sq.m
--SA/ws (not foiling)=6.59/1 ; foiling=16.5/1

==============
Curtis Luxtons foiler: updated 1/2/14
1) SA/lb--213.5 sq.in./lb.
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2) SA per sq.in of main foils area = 36.21 sq.in per sq.in main foil area.
--mainfoil+ama foil(s) area at takeoff=37 sq.in.
/combination manual and surface piercing(?) altitude control
--------
3) Foil Loading at takeoff=
a. Mainfoil=.065lb./sq.in.
b. ama foil(s?)=.06lb./sq.in
-------
4) Foil Areas:
--mainfoil +ama foils at takeoff-37sq.in./ combination manual and surface piercing altitude control
--rudder?
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5) Specs:
--LOA-90cm / 35.4"
--Beam -1.1m / 43.3"
--Weight -2.75lb / 1.25 kg
--Sail Area - .38sq.m /587 sq.in
--SA/ws- foiling:7.5/1, not foiling: 2.2/1
==============
Ians Foiler(PM40m) :
1) SA/lb--175sq.in/lb.
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2) SA per sq.in of main foils (at takeoff-changes after takeoff)= 29 sq.in. SA per sq.in foil area.
--------
3) Foil Loading at takeoff= .166lb/sq.in.(both foils immersed)
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4) Foil Areas
--main 24 sq. in. each-surface piercing altitude control
--rudder ?
5) Specs:
--LOA-48"(1.22m)
--Beam - 48"(1.22m)
--Weight -7.96lb / 3.62kg
--Sail Area- 1394 sq.in /.9 sq.m.
--SA/ws (not foiling)=? ; foiling=?
===============
Jims Foiler:
1) SA/lb--231.6 sq.in. per lb.
--------
2) SA per sq.in of main foils (at takeoff-changes after takeoff)= 38.6 sq.in SA per sq.in foil area.
--------
3) Foil Loading at takeoff= .167 lb/sq.in.
-------
4) Foil Areas
--mainfoils-18 sq.in each(initially) 36 total./ Bradfield fully submerged altitude control system.
--rudder- 18 sq.in.
-------
5) Specs:
--LOA-48"/1.22m
--Beam -48"/ 1.22m
--Weight -6lb.
--Sail Area-1397 sq.in /.9 sq.m
--SA/ws (not foiling)=? ; foiling=?

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Anybody want something added or deleted just let me know.
Still need foiling and non-foiling wetted surface stats from Ian and Jim. Also please check your information to be sure that I entered it correctly. Thanks for the help.