MPX Test Model
Here is the working drawing of the main foil.
1)-39sq.in.
2)-30% flap/offset*
3)-23.375" span
4)-9% T/C(thickness/chord) ratio(tapering to about 12% at tips)
This is a successful design that I used on the F3 RC foiler, my 16' monofoiler and the RC microFoiler. It was inspired by Dr. Bradfield and Graham Bantock.
This is a fairly thin foil and if the flap was hinged full span as "normal" there is a good chance that it would not work freely-binding between up and down when the foil is under load. I tested an early full span Moth foil and found that it did bind a bit under load. By laying the foil out like this the flap is in the strongest area of the foil and is unlikely to bend under load(will be tested to ensure this). Bradfield used full span flaps but had to make a special attachment that gave clearance to the rod used to retain the flap. His foils were 15% T/C . At any rate, I tried this first on the 16 footer and it worked(better than the boat did) and next on the F3 where it worked perfectly.
PS- what isn't shown is a small projection sticking out forward reflecting a "bulb" that is used to give more bonding area and probably has other hydrodynamic benefits.
PS-2 the rudder planform will be similar, without the flap.
===================
Here are some more foil details: ( compare with mainfoil details below)
1) Rudder hydrofoil- this foil has an area of 29.5 sq. in. which is half the area of the main foil+ immersed part of the lee ama foil. It has one half the loading per sq.in. of the two forward foils. The T/C(thickness/chord ratio) is the same as the main foil-9%- and the section the same-both symetrical foils. The rudder foil does not use a flap since the whole rudder can be adjusted for angle of incidence. The set-up starting out is an angle of incidence of zero degrees(with reference to the static waterline)
--
2) Ama foil(see working drawing below)- inspired by the refined TNZ AC 72 main foils that use a combination of the curved portion of the foil(acting as a surface piercing foil) and the "L/J" on the bottom of the foil. On this boat, the ama foils have a bit more radius to the curved portion of the foil, to allow a wider speed range before there might have to be adjustment of the angle of incidence of the foil. The immersed area is nominally 20 sq. in., the T/C
9% and the section a modified version of the Speer H105. If this system works as expected the ama foil will take nearly 100% of the load as compared to about 70% of the load on a MOD 70 ama foil, allowing the main foil to be unloaded and allowing the main and rudder foil to control pitch and heave only-no other "work" for them. This should reduce drag dramatically compared to other 3 foil foilers. It will also allow the main + rudder foil to ensure that the boat sails at a specific angle of heel(controlled and set by the wand(s)).
--
3) Daggerboard-overall length 20.5" with 17.5" under the boat and a 3" chord, section something like a NACA-65-009, T/C the same as the others.
--
4) Rudder-overall length 20.5", 17" from the waterline to the rudder foil with a 2.5" chord, same section as daggerboard. The rudder is mounted to a pivotable(in two axis) part of the rudder gantry so the the area of the leading edge of the rudder ahead of the vertical pivot axis is 18.75 %. The horizontal axis of the rudder mount is used to facillitate rudder angle of incidence adjustment ,should it be required(unlikely).
--a. The rudder hydrofoil is slightly higher than the main hydrofoil(87% of main foil depth) to avoid interference between the foils.
---------
More to come.....
