For those who've measured, what wing/stab angles seem to work well (all other things being equal)? Some of the stuff I've read on glissattitude and a post elsewhere here seems to suggest -4 degrees being pretty typical with the objective of stability rather than top end speed. I'm at about -2 presently.https://www.windsurf.boutique/actus/windfoil-calage-des-stabs-en-foil.html (translate with Chrome, Chromium, google translate etc for non French speakers)
The problem is all things aren't equal foil to foil so it's somewhat of a null reference unless you are comparing the same foil; in terms of specific measurements anyway. The only thing you can really say as a general blanket statement, within reason, is the more rear stabiliser trim (raising the rear of the stabiliser relative to the front) the more lift, the more stability but also more drag.
For reference on a Flight:F4 I run it at maximum trim no matter what the sail, what the wind. This is because for course racing you want as much lift and stability as you can get, within reason.
Thanks. Kind of what I was looking for. Other than drag, any other drawbacks? Must confess that I'm not going fast where drag is holding me back. I think with a more stable set up, I could push the speed thing a bit more. Everything is pretty well balanced but it's quite sensitive to trim changes.
At extreme angles of trim you do really start to notice the drag, It probably knocks 2-3kts off the top end on the F4 but I'm talking fairly extreme angles in order to get over the foils deficiencies upwind when racing compared to say the Starboard race foil. I have solved this issue by extending the fuselage so I can get more force (well moment really) out of the rear stab at a lower trim angle = less drag.
The other issue you might encounter is variances in lift with speed, which once again is really foil dependent. The F4 is quite neutral in that the foot pressure front to back doesn't change that much with speed until you get right to the upper limit; i'm talking over 25kts or so.
Some foils tend to keep generating more and more lift in an unbalanced ratio front wing to back wing , needing more front foot pressure the faster you go, this will obviously get worse if you put more rear stabiliser trim in on such a foil.
If you have the option to try it I'd give it a go, you will notice increased pitch stability with more rear stabiliser trim which seems to be what you are after. What foil have you got if I may ask? Some foils are naturally a lot more stable. Anything with a long fuselage, such as the starboard race foil will be much more stable in pitch. It's the one of the reasons why all the race foils are now going long in the fuselage.
Thanks for the explanation. Horue GP with both LW and XLW wings. I've got one washer in it which gives, as best I can measure around -2 degrees differential. Before I got my foil board, I had 2 washers in just to get it to fly right with the conventional board but that was pretty lifty.
