Hi Fast Foiler's

I had a session in Georges river at SGSC with Jules a few days ago. it was Fun, difficult and expensive.
F4 375cm2 tiny speed foil 590mm wide on 100+3 cm fuselage with 190cm2 small tail, no shim.

Patrik 5.0 SF crossover sail (slightly loose draft)

SB 76cm wide foil board 125L

The 375 foil on 76 board felt really wobbly side to side and not as comfortable as the 400 wing, despite the similarities. Note the last 2 times I had the 400 on my FMX 91 wide with stable CHS sails
Was it the foil or the sail or the board or the alcohol at lunch?
I Managed some good speeds, ~30 knot peak2s and 100m and ~20 knot alpha.

I'd be interested to hear what causes side to side wobble? turned out to be an expensive day after I had a few catapults around 25kt or maybe more!

I'm familiar with nose to tail instability and wrote a lot about this in the 30 knot thread!

Berowne, is it roll or yaw instability or a combination of both? Yaw is rotation in the horizontal plane and roll is side to side rotation

Have you considered changing the stabiliser? Wing tips effect yaw stability. Dihedral angle effects roll stability.

Definitely the lunch time alcohol

Select to expand quote

John340 said..
Berowne, is it roll or yaw instability or a combination of both? Yaw is rotation in the horizontal plane and roll is side to side rotation

Have you considered changing the stabiliser? Wing tips effect yaw stability. Dihedral angle effects roll stability.

I'll have to clean up any new scratches and try again. but I do t think it was yaw. felt more like roll instability and a new sensation that was unfamiliar. That could have been yaw. I'll try and pay more attention next time I'm above 28 knots!

Not on the speed wobbles

But what is that huge crack next to the watch?

Elmo, just a shadow on the watch!

I wonder if it might be to do with the mast base position?

Base closer to the foil, particularly with the narrower span of the small foil will give a more sensitive feel on the side to side as well as pitch, maybe try moving the base 1 or 2 cm forward and see if that makes any difference?

Dave

Nasty crease on the trusty SB Freeride. Must of being a huge catapult!
In the last few years I have started using smaller foils in the search of extra speed, Starboard SLR foils a year ago and recently a full switch to Phantom Iris R. Currently have the 430cm2/ 200 tail combo, it definitely is sensitive rail to rail (obviously gets worse the higher you get out of the water!)
When doing speed runs I bear off smoothly a few feet above the water, then when comfortable with my angle and the gear is settled - that's when I play with fire and try get higher above the water to get that extra knot or two. Bloody scarey but it seems to work.... most of the time
*Make sure the footstraps are snug on your feet (important for small twitchy foils) sometimes a wobbly board is also just nerves and "jelly leg syndrome"
P.S You need to beat my speed Berowne Sitting above you on the GPS rankings, can't let a Kiwi beat you lol.
I have just got the smaller 350cm2/175 combo which I hope to get on the water on the next 30ish knot offshore windy day.

I have also been using a 91 wide Starboard with the small Phantom 430 / 200, not the ideal combo. I take my rear foot out of the strap on speed runs as way out on the rail feels wrong.
*I have nearly finished my own design 79 wide foil board (very similar to Starboard X15) just needs, a little more paint and then non-skid added.
Hopefully this will give me a bit more speed and control.