I think that I can fly.

[Clive Everest]

Without it the centre of lift of the main foil would move aft as the speed increases due to the fact that it is a cambered section.
This would put too much force on the push rod.
The phenomenon would be familiar to anyone old enough to have sailed an original windsurfer regatta.
In a gust the load would all go to the back hand and the front would be positively pushing up.
modern sailboard sails are flat and gutless but easy to handle.
The tailplane creates a down force that increases with speed as its AoA becomes more negative taking load off the push-rod allowing the wand control to work.
I think that the control issues that I had were due to the AoA of the tailplane being modified by the main foil in front of it resulting in insufficient load on the push rod and a sluggish reduction in lift as the boat rose.
It is difficult to see exactly what is happening when looking for a clear flight path through the rigging.
 

[simon_jones]

Looks awesome Clive. Will we see it at QMSC?

[Clive Everest]

Thanks Simon,
Unfortunately we have a family commitment that weekend.
The pictures do not show how much of the time it was not flying.

[Phil Alderson]

Best of luck with this, interested to see how it turns out. The warning about posts could be because you made several posts in a short period of time.

[Neil C.]

The tailplane creates a down force that increases with speed as its AoA becomes more negative

Thanks, I think I get it now. A much smaller foil, but on a longer lever so able to increasingly counteract lift from the main foil as speed increases. So in theory, could this be the basis for a completely automatic system which finds it's own equilibrium without any wand controls at all, other than just a spring on top of the push rod to put some angle into the main foil at low speed?

[ade white]

Bloody good so far. Well done. Lots of really interesting stuff going on here. Do you think the foil could even be fixed with the tailplane on a parallelogram fixing that could effectively reduce lift as speed increased. Maybe more drag but early days... The boat looks good in the still photos. How easy is righting after a capsize? Any thoughts on a dihedral foil working in this set up if height is a worry?
Joe has hidden my jig saw!!!!!

[Clive Everest]

Close Neil, it is not counteracting the lift from the main foil but counteracting the pitching moment.
It means that the combination remain balanced at different angles of attack.

If you had a symmetrical section it would not be needed but you would not be able to generate that much lift. Symmetrical sections have minimal pitching moment.

You will always need a wand, the foil itself does not know how far it is below the surface.

[Clive Everest]

Hi Ade,
Tell Joe to speak to Alex.
I think that a dihedral foil is only going to help if it is surface piercing so that the amount of lift reduces as it comes out of the water.
This is how the flying cats are getting stable flight.
The changes in lift with a change in height is not that great compared with what can been done with a wand. They also suffer from changes in pitch causing significant changes in lift.
I am sure that the wand is the better system. look at how well the Moths fly.
I just need to make it work.
The static pictures give a better impression than the reality at this stage.
Righting from a capsize did not seem to be a problem. You have a ladder to climb and with my weight the boat pops up easily. I had several chances to test this.
Dan and Rog made the trailing edges sharper than I would have liked.

[Neil C.]

I see (I think!), the extra wing is counteracting the rotation of the main wing and taking a lot of load off the pushrod, but there is still a load of lift being directed through the main axle and up the daggerboard.

Also, a system which trims out the main foil with increasing speed is not the same thing as a system which trims out lift with increasing height off the water, hence why the wand system needs to be attached to the boat, and not directly to the main foil I suppose.

[Clive Everest]

That's it.
I think that at the moment the tail plane is taking to much load off the push rod and the main foil is not following the wand. I think that this is because I have not properly allowed for the deflection of the flow over the tail plane from the main foil..

I have also not allowed for the hydrodynamic torque that is generated when trying to trim the foil.
Fortunately it is easy to adjust the aoa of the tail plane and not a big task to make a bigger one.
Hopefully there is no problem putting bigger forces through the push rod.


If the weather is cooperative We will try again this weekend.

[Tim Noyce]

I await with baited breath. It's so wonderful to have a thread about foiling which is backed up with substance and a good serving of 'doing'!

[HighwaytoHelm]

Hi Clive,

The boat looks awesome, and personally I think that it flew first time out is a massive achievement. I also really like the twin booms on the tailplane,  very reminiscent of a p-38. It will be great to see the progress made over the next few months.

Mike

[Torchy]

Nice one Clive...maybe I'll start getting my act together!

[paul_croote]

Been looking at the tailplane on your main foil and thinking about the effect on stability. If the boat drops suddenly wouldn’t the upward flowing water increase the angle of attack on the tail pushing main foil to decrease its angle that then makes it drop quicker? (assuming any slack in the system allows it)

[Clive Everest]

The tail plane should be doing much the same job as the tailplane on an aircraft.
It controls the position of the total center of lift.
An aircraft does not suddenly pitch down if it drops slightly.

I am not claiming to have all the answers. certainly it was not controlling in a way that I would like.