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

Fire Arrow Foiler / MPX Foil System Testing and Development

Hey Jim- yeah, never considered that.....

 

Doug, with such a small sail plan why bother with a reefing system, why not just have a #2 set of sails made to match the smaller rig. This will ultimately give you a better and more efficient result as you will remove the rather high amount of aerodynamic drag caused by the rolled up sail below the reef point.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

I can't afford a new sail, mast and boom + fittings. I'm not sure the rolled sail is much drag. I used this same system on the F3 and several other models 14+ years ago and it worked perfectly. But the bottom line is money-this isn't a small sail-the rig is 9' off the water and 23 sq.ft.(upwind) 28 sq.ft(light air)-largest, heaviest, and most powered up foiler I've ever built for radio control. If you're suggesting using the same mast, shortened- it would be a real pain because of the way the sail is attached to the mast with a luff wire-and the fact that the mast rotates. But even that's a moot question because of the money involved.
I could probably simplify the attachment but I just can't afford a new sail or sails at this point. In a while I may have Scott make a new jib-the current one is a bit tall for the reefed rig. Thanks for the suggestion.

 

Fire Arrow Foiler / MPX Foil System Testing and Development

MPX Test Model Specifications---latest update: 8/14/14

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= 4087 sq.in.( 28.38 sq.ft. )5/1/14

3. Main + Mast-no jib= 2690 sq.in ( 18.7 sq.ft.)8/14/14

4. Reefed Main + jib= 2796 sq.in ( 19.4 sq.ft.)8/14/14

5. Reefed main + mast= 2096 sq.in.( 14.5 sq.ft.)8/14/14

F) Foils(all foils updated 8/14/14)

1. Main foil area was increased from 50 sq.in. to 84sq.in. which gives it a foil loading of .188lb/sq.in. which is identical to the F3 and equal to about 75% of the total sailing weight. For earliest takeoff the lift from the ama foil is discounted to make sure the main foil alone can lift the boat. Span was increased from 23 to 29" with a 7.6/1 aspect ratio. Initial foiling was done with a mainfoil angle of incidence of 2.5 degrees.

2. Rudder foil area was increased from 26 sq.in to 49.8 sq.in. and is now 59% of mainfoil area with an aspect ratio of 8/1. Span increased from 18.74 in. to 23.25 in.. Rudder foil loading is.106 lb/sq.in. and equal to about 25% of total sailing weight at takeoff. Loading on this foil automatically changes from takeoff to near zero to negative(pulling down). Initial foiling as done with the rudder foil set at 0 degrees angle of incidence.

3. Ama foil(s) area is 68.62 sq.in. which will change as it is refined. The effective area(projected) for vertical lift is 52.9 sq.in. or 77% of total area. One foil is still using the i-flap, described earlier, while the other foil has had the flap removed but retains the same projected area for vertical lift. The idea is to test whether or not the foil can achieve early take off as well as the foil with the i-flap-or at least close enough to justify the reduced drag by the removal of the i-flap. The effective aspect ratio of the foil includes both the horizontal component and the vertical(curved) component and is 6.4/1.
IMPORTANT NOTE- In the last 7+ min foiling video it is clear that it would be ideal to have the model foils retractable and that for sure, as always planned, the full size foils will be retractable. But when they are retractable they will also be about a foot deeper(3.375" on the model) which would help in waves when on the foils. Not possible on the model, at least any time soon.

4. All Foils change their loading as the boat speeds up:

a. Mainfoil begins to unload right after takeoff until it's primary function is pitch control(with the rudder) and maintenance of the main hull altitude(boat angle of heel). If the heeling force causes the main hull to rise past the preset wand altitude set point( that is, if the angle of heel increases), the main foil will develop substantial downforce adding to the righting moment of the boat.This is a particularly important feature of this foil configuration.

b. Rudder foil starts with a maximum vertical lift of 25% of the total load(5.28 lbs) minus the pitching moment created by the rig. It will change loading automatically until it pulls down, if necessary. Rudder foil works with the main foil to control the pitch angle of the boat.

c. Ama foil begins to load up right after takeoff until it carries the majority of the load. Ama foil angle of incidence is preset for the conditions apparent at the time of launch. On the full size boat the ama foil angle of incidence will be adjustable while sailing but such adjustment will be very infrequent. Ama foil angle of attack is controlled by the main foil and rudder foil working together. Ama foil angle of incidence is preset in the range of 0 degrees to +7 degrees. Initial foiling was done with the AOI set at + 7 degrees. From the results of the early foiling, it appears that the AOI may be able to be substantially reduced-depending on the comparison tests of the two ama foils-one with the i-flap and one without. Independent pitching of the ama foil is physically impossible since ride angle is controlled by the main foil and rudder foil, again, together.

d. Angle of incidence of every foil is measured in reference to the static design waterline which is parallel to the flight waterline soon after takeoff.

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Note: you can find all the test videos so far here: https://www.youtube.com/channel/UC6S7JPG1d2uZ91lqt7ObyIw
Here is the short video again-the boat had a tacking problem this day because of my overdoing it with Dual Rate and Expo. The transmitter has been re-programmed to allow me to switch off DR/Expo.
https://www.youtube.com/watch?v=7Mok3d4KiMI

 

Sweet! It's up and running!

 

Fire Arrow Foiler / MPX Foil System Testing and Development

You betcha! Thanks....

 

Fire Arrow Foiler / MPX Foil System Testing and Development

The reefed rig is surely smaller and to change from the normal rig to this one is quick. The cool thing is that the normal jib works with no forestay adjustments and the same shrouds work with a bowsie used to adjust them. They are marked now so it won't be necessary to guess in the future-move the bowsie to the mark and go.

 

RC Foilers

Here is a video by Ian Holt and the following is the description that goes with the video:
2 Mini40s sailing at Austin Lakes. 74 is an rcsails Firedragon, using a C rig from Frank Russell, foils from Mike Dann and rudder from Dave Creed. This is now the fastest Mini40 that we have in West Australia. 58 is my design, with an A rig from Mike Dann. Rudder form Dave Creed, the foils are my own design.

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https://www.youtube.com/watch?v=96pgkObm_10&feature=youtu.be

 

Fire Arrow Foiler / MPX Foil System Testing and Development---Drag Reduction

I'm concentrating now on reducing drag without compromising the early takeoff of the boat. In studying Bill Beaver's paper on the Moth I was impressed with the very large aerodynamic drag associated with the boat. In the Moth class now a lot of attention is being paid to reducing aero drag.
On the Fire Arrow one huge contribution to aerodynamic drag has been fixed-the over twisted rig.
The next biggest aero drag on this boat is the cross arm tubes. I consider, a long time ago, adding fairings to the tubes but discarded that idea after considering cost and time -and also the fact that they would most likely be fragile.
Now I've come up with the idea of using a single removable plate-a "splitter plate" in Hoerners terminology. On one table below, it is shown that a splitter plate can reduce drag by 43% compared to a cylinder with no plate. Sounds like a gain worth having.
I'd respectfully ask all you guys that have been following this project faithfully to please make any and all suggestions that occur to you to help me reduce aero or hydro drag on this boat. Thanks in advance!

Check out the tables and my sketch below. The splitter plate attached at an angle to the tube would be the simplest-the other is a splitter plate as shown in the tables:

 

On a boat with a round tubular mast ,(like the stock B24,28,33 etc: ), the sail it's self acts as a splitter.
Most people won't make the tubular mast pivoting since it is not elliptical.
Nevertheless if it was pivoting it would still improve the airflow, as seen in the variation in the above pics.
On a multi with tubular cross arms the side nets perform the same role.

 

Fire Arrow Foiler / MPX Foil System Testing and Development---Drag Reduction

Thanks for the answer ,Paddy! I was thinking about that but it seemed that an unnecessary(on this boat-full size:no tramp) tramp could increase frictional drag more than the benefit from its role as a splitter plate-and would only affect the forward tube?

 

Yes Doug, that has to be taken into account.
It will depend on the construction of the side nets and whether they are net, woven tape or solid sheet. I know two of my past multis had ply side decks with streamlined fore beams. I do feel the aft beams are a different and more difficult problem because of the turbulent air they are in. Remember the AC catamarans had a streamlined "Tail" on their aft beams.

 

This was all solved in the sixties by Hedley Nicol- aero wing decks to take off and fly. Since he didn't have foils he detuned the wings on designs after the Vagabond 1 28 knot barrel roll....

 

Yes, and Norm Cross had solid wing decks with an upside down airfoil shape to provide "Negative lift", on the basis that the windward deck would have more down force than the leeward one. Don't know how effective that was though.
I do know that his 31R was a lovely Tri to sail.

 

The float on the mast must be very draggy as I have already said. I doubt its doing you any aerodynamic favors even though I know you think it is based on the fact that span is always good. In this case, I don't think its good. Its not a sail or a foil its a block.