extending a gantry

[MK]

A t foil boat should always be sailed with the hull at optimal trim, obviously

So on the most basic of levels, if your boat is at optimum trim, and you aren't stood at the back of the racks, move back, and add more +ve onto the foil

You will tend to use less foil downwind as your extra boat speed will produce more lift for the same angle of attack



The t foil even in positive stops nosediving as it hugely reduces pitching, the boat pivots roughly more around the transom rather than the middle, also, when the boat goes into a nosedive, a serious one, the max of 7 degrees you may have on stops giving lift and starts giving suck as soon as the bow nosedives more than 7 degrees

[Torchy]

Aha...thanks mate, that makes sense

[Phil Alderson]

Thinking about it I have probably applied more balancing to my T-foil rudder stocks than I had on my std rudder stocks. Initially because the design of adjustment I used required it, and more lately because I know how I want it to feel.

[Will_Lee]

Yes - Antidotes last two t foils had the foil tipped down quite a lot so the foil would be further forward, but it would also have affected balance because I moved the stock against the pin rather than the whole stock and pin (because it risked hitting the water)

[roland_trim]

Interesting thoughts on how it is the geometry of the axis of rotation and the foil - not the axis of rotation and the water than is altering the load. After filling a page or 3 with sketches this has some fun implications with flappy panel gantries always having almost the same load with foil +/- or off (there is a slight geometrical change and the load increases with speed due to lift/drag when turning).  
Having sailed both slot and flappy T-foil systems I did notice the foil became lighter with more foil on in Born Slippy (system had a slot and fixed pin) and have not noticed much change in the flappy panel  boats since. Although I have not thought about it much before this thread...

In essence the advice presented her appears to boils down to the suggestion:

"better to ensure the top hole (usually found in the in the tiller) is further from the foil than the bottom hole (i.e. bottom of stock). Especially for flappy gantry systems - but not too far".

[phil_kirk]

It may help if the lifting foil is near the front of the rudder blade and therefore underneath the extension of the pin when on positive and creating lots of lift.   We are tending to keep the lifting foil in this position to make it easier to helm weight over the foil.

[Stuberry]

The T-foils built by Demon Yachts are designed by Kevin to be raked well forward to put the foil as close to the boat as possible. The foil is angled relative to the rudder to give lift when its well forward and the rudder is also very long to help with this and keep the foil in the deepest water.