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

[David Cooper]

You're just trying to play games with words to try to have your cake and eat it. Downforce is not a little bit less lift. Downforce is only a valid description of something generating a force downwards. I've just checked half a dozen dictionaries to make sure and not a single one of them agrees with the way you're trying to use the word. All of them very specifically talk about generating a force downwards.

 

[Doug Lord]

If the windward foil is operating at its designed flight altitude with the flap in neutral(neither up or down) and the rig is hit with a small gust the flap on the windward foil will go up slightly as a response to that gust. When it goes up it generates a small amount of downforce to restore the windward hull to its designed flight altitude.
Similarly, the leeward foil flap goes down slightly to generate a small increase in the amount of lift on the lee foil to restore the lee hull to its designed flight altitude.
--
That's what happens, those are the facts-accept it or not.........

 

[Doug Lord]

Fire Arrow Foiling System Testing and Development

Post 2251 How the Fire Arrow works:

Probably the most significant feature of the Fire Arrow is that it uses two completely independent altitude control systems for the first time on any trimaran:
1) UptiP ama foils(also a first for any size trimaran*) that control the height of the ama above the water,
*used on this boat way before they were used on any other tri.
2) Wand controlled mainfoil on the daggerboard-controls main hull height above the water which, in turn, sets the angle of heel for the whole boat.The mainfoil also allows the main hull to fly in very light air.(5mph)
But its the interrelationship between the main and rudder T-foil with the ama foil that makes the system so significant. The rudder T-foil is a trailing foil and "follows" the main foil. Altitude and angle of heel for the whole boat are set by adjusting the wand length. The boat is extremely stable in pitch because of the bi-foil arrangement on the main hull-the daggerboard foil and rudder foil always work together to control pitch. But they also control the ride angle and pitch of the ama foil which can't pitch on its own-in other words the ama foil can't all of a sudden "go negative" and cause a pitch pole.
In an early test before the ama foils were the right size and the wands were set incorrectly the boat did a wannabe pitch pole caused by being overpowered and attempting a gybe in those conditions when off the foils. She recovered very quickly and sailed on.
So while the system is unique and has many advantages common sense sailing is still important as I learned(again) in that incident.
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The Fire Arrow advantages would work very well on almost any size small tri and possibly work well on much larger tri's as well. Hopefully, I'll be able to get the help I need to build a 19.5' version of the Test Model which would be a very cool trimaran and would illustrate well why this system is such an advance in small trimaran design.
In the meantime, I'm planning on get more video with the reefed rig and shorter mainfoil and rudder foil.

===========================================
In the post above, I neglected to mention a major advantage of the wand controlled foil on the main hull: that is the ability of the wand to cause the foil to create downforce which can add significantly to the righting moment of the boat. It is an automatic response to the boat heeling even a slight amount-the wand will cause the flap to go up as much as is necessary to restore the main hull to its designed flight altitude. That can add a large amount of righting moment to the boat.
It's been well proven on the Trifoiler ,Rave, and Osprey that the drag caused by doing this is not as much a disadvantage as the extra RM is an advantage.
These boats have dual independent altitude control systems and their foils can produce all the righting moment required by the boat.

From 7/24/14-the first day the foil system worked perfectly:

 

[Munter]

I forgot the other regularly deployed tactics which are to:

1. Attempt to redefine what is being disagreed about to something where there is no disagreement to take attention away from the actual problem. Note post 2282 does not attempt to address the core issue which is the definition of downforce but puts up a strawman argument about the working of wands and flaps on a topic that is not under dispute.
2. Repost pictures and extensively requote himself to push posts which he finds challenging into the background – see post 2283 as an example. Often this is done concurrently with editing past posts without acknowledgement so that the endless repetition is not as obvious to those who aren’t aware of the full thread history. Most people have the humility to be able acknowledge when they make changes, particularly if they are anything more than the correction of typos.

 

[OzFred]

Some videos to compare Doug's foiler with one that has gone through a test and development program guided by real–world experience. PerthMini40man has worked through various foil configurations and sail plans, the result is a pretty stock looking foiler that works very well.

Turn the sound off first.

Doug video short version (1 min 51 sec): http://www.youtube.com/watch?v=7Mok3d4KiMI
Doug video long version (7 min 47 sec): http://www.youtube.com/watch?v=4YBOEolFqiE

PerthMini40man video (7 min 5 sec): http://www.youtube.com/watch?v=nzTf9pedWdE

 

[redreuben]

Fred it's all been said before, the only thing that seems to matter to Doug is word count.

 

[Doug Lord]

Some videos to compare Doug's foiler with one that has gone through a test and development program guided by real–world experience. PerthMini40man has worked through various foil configurations and sail plans, the result is a pretty stock looking foiler that works very well.

Turn the sound off first.

Doug video short version (1 min 51 sec): http://www.youtube.com/watch?v=7Mok3d4KiMI
Doug video long version (7 min 47 sec): http://www.youtube.com/watch?v=4YBOEolFqiE

PerthMini40man video (7 min 5 sec): http://www.youtube.com/watch?v=nzTf9pedWdE

============
Ian Holts trimaran foilers are excellent! But there is a big difference between the types of foiler: his are race boats with an excellent foil system and multiple rigs.
The Fire Arrow is an exact SCALE model using an experimental foil system that has been designed, built and developed over several years. In the last video, where the hydrofoil system worked the way it was supposed to for the first time, there was still a problem with the rudder directly related to the radio set up.
The Fire Arrow uses an experimental foil system-never before used on another trimaran ever- that worked perfectly in its last test sail, July 24, 2014 in very light air and relatively big waves(for the wind speed).
Oh, and my first production rc sailing foiler-the F3*- was done over 20 years ago......
*worlds first production RC sailing foiler

 

[David Cooper]

If the windward foil is operating at its designed flight altitude with the flap in neutral(neither up or down) and the rig is hit with a small gust the flap on the windward foil will go up slightly as a response to that gust. When it goes up it generates a small amount of downforce to restore the windward hull to its designed flight altitude.
Similarly, the leeward foil flap goes down slightly to generate a small increase in the amount of lift on the lee foil to restore the lee hull to its designed flight altitude.
--
That's what happens, those are the facts-accept it or not.........

A reduced positive = a negative: that is now a fact because the Lord says so (a foil generating reduced positive lift = a foil generating downforce [which to everyone else on this planet means negative lift]). We must now rewrite all books on math and physics to take this into account.

 

[Doug Lord]

"...or not...", I guess. That's unfortunate David....

 

[OzFred]

It seems you had a different opinion when discussing this recently on Sailing Anarchy with statements like:

I've always said that if(and when) the windward foil pulls down creating downforce …

14' Stunt S9 Foiling Cat.

I don't think anyone can interpret that as anything other than "down force" is pulling down. And apparently you always said that, until now.

 

[Doug Lord]

What? I don't understand your comment at all. The windward foil on most dual, independent wand systems can do anything from pull down at max downforce or generate just a tiny amount of downforce-whatever it takes to restore the hull to its design flight altitude-totally controlled by the wand.
On the Fire Arrow downforce can be almost as much as the weight of the boat in extra RM. It's a potentially great advantage on a boat like the Fire Arrow that allows instantaneous response to gusts and allows the full size version to be sailed with a very small amount of movable ballast. A single crew could sail this boat in the same general wind range as a crew of two because the mainfoil downforce will make up for the difference in crew weight.
--
On the oversquare Fire Arrow full size version the crew always sits to one side of the cockpit or the other-there is no running out to the ama because there is no need for the extra righting moment that would provide. That's because of the innate RM provided by the 22' wide platform backed up by mainfoil downforce whenever required.

 

[Doug Lord]

Full size tri on foils!

Gitana Mod 70 flying like no other full size tri ever-except for Hydroptere-and this boat is longer:
http://www.boatdesign.net/forums/mu...ing-revolution-gitana-53061-5.html#post772385 post75
She has an UptiP foil and rudder T-foil on each ama.

 

[PerthMini40man]

Foils etc

We had three tris on the water on Sunday - a Mini40 testing outboard foils, and two One Metre tris. Some good fun! The outboard foils produce immense power but are currently slow. Need to reduce drag

https://www.youtube.com/watch?v=byIymlNi9IE&feature=em-uploademail

 

[Doug Lord]

RC Foilers

Good stuff-thanks Ian!

 

[Doug Lord]

Outward pointing foils

This picture is just to illustrate how Hugh Welbourn handles his outward pointing foils on the Q 23. His foils are designed to not develop lateral resistance when flying-he uses the keel for that. Greg Ketterman tested outward pointing foils on the Trifoiler and he also found them slow. But his outward pointing foils still had to develop all the lateral resistance for the boat. He explained to me that they were high drag due to having high and low pressure on the same side.
So make sure the outward pointing foils are just generating vertical lift and no lateral resistance. Add a daggerboard. Might be a good trade off for substantially increased RM.

This section is the exact opposite of a section designed for lateral resistance-it's worth careful study.On a "normal" boat with dual foils the flatter part of the asymmetric section would be on the outboard side of the trunk. The TOP of the picture is the lee side of the boat: