F4Foils Tuning Tips - Towards 30 knots!

I've been looking back at the Tiberias races... exciting stuff!

This is what i meant about board angle to windward to control the lift at speed...

So I had an epic session yesterday... looked light, about 10kts so rigged a Phantom 9.0 IRIS sail and 620cm2 large slalom F4 front wing and 210 rear on 100cm fueslage with no shims.

A couple of pumps and it was up easily enogh. I was flying around stalled windwings and other foilers on large wings and smaller sails (which felt annoyingly good. . . !).

Now that I've found "the sweet spot" for the mast base and each fueslage/wing set, 20 knots has become relaxing, 24 knots seems to be a natural peak for crusing (maybe when lift and drag match?), and 25 knots and above, while not 'comfortable' certainly is much more managable.

Yesterday I was hooked in and riding both footstraps in smooth offshore waters with the gap closed riding in a slalom style stance for the moderate gusts (pushing both front and back legs really driving the foil - felt great!) and monkey man hanging off the boom with bent knees for the overpowered runs, balancing board pitch and roll and still trying to keep the power on. Gap closed, foot of the sail on the centreline or there abouts. Felt pretty good actually!

2 Second Peak (kts):26.824
Top 10 sec speeds: 25.078

Should I have changed down a sail size? or Front Wing?

But the real question is... should I have changed down a sail size? Or front wing? As the wind built getting going was less of an issue, and controlling the sail forces was becoming harder. I finally came in when I couldn't sheet in (30 degrees open) and was in survival mode on a reach. I swapped down to a 5.8 slalom sail I found lying on the beach and could just keep it sheeted in on the 2nd or 3rd run after getting used to the new feel.

Lesson Learnt: Phantom Foiling Race sails are AWESOME! The stability in that rig was amazing, felt almost like a fixed wing.

So I finally did it! 30knots on the GPS.


Just not for 2s. But hey this was the first time out on a new foil in gusty 10-30knots.

The wind turned it on yesterday so I rigged my foil for speed.... much to the amusement of a few Fin loyalists.

F4 337 cm2 area , 560mm span - 100cm fuselage, ~2.7 degree mast angle and 170cm2 tail wing later with 1mm shim
S2 5.0 4 cam slalom sail - originally rigged with high clew hole - firm leech foil style
FMX 91cm Hyperion foil board. I don't think I need an 80cm board just yet as the 91 get fine.



The feel of the new wing was LOOSE! It is so small, it is really easy to ride, much like a wave board. It flies surprisingly early, minimum board speed to fly was about 15kts (I was expecting 20).... and mid-gybe I think it was still flying at 11kts once.

But it does need POWER to fly. Plenty of lulls I was left waiting for the wind.

But I'm not after a good time, I'm after a fast time, so I headed off in search of some flat water. With the wind gusting over 30kts there wasn't a lot to be had. Everywhere I looked had swell over 15cm and in the middle of George's River it was almost a metre! There were a few breaches and unintended arials while I got used to the new wing, and the power at speed. The ride is very much rear foot oriented at 20kts and front foot oriented as you accelerate.

After a break I tried the slalom clew setting since the wind was quite heavy and also added a small shim to the rear wing. This made the board flight a bit more controlled, but also tended to be a little too rear foot oriented and I needed to move the mast back as I kept tapping the waves on a speed run with trim just a little too tricky to balance above 25kts this first time out. This is actually the scariest part of foiling over 25kts... tapping the wave tops is like a handbreak, so balancing flight so you glide above the wave peaks, but don't foil out of the troughs.

Only managed 29.6kts for 2Sec peak on first outing with the wing. More to come, this thing is fast!

I need to try a few more trim options to balance lift above 25kts better. Oh and commit to both footstraps!

Oh and this wing was LOUD! The whistle above 27kts is inspirational... helps to push as the volume increases! Hopefully the video captures it.... pending!

www.ka72.com/Track/t/483557

Sheeting in for power.

Scared sheetless (sheeting out, so "less sheet")

Gotta use rear strap for triangulation, and this allows more weight forward to handle unexpected gusts.

What foil is AA riding these days. Looks like partnership with F4 no longer exists. It looks like a carbon NP race foil... which doesn't official exist right now (2021). Any ideas?

I assume NP SLR foil (coming soon).

berowne, I love your noises and talking during flight. I could put together some really cool memes. Too funny, love it.

@berowne love the video, not sure which sound is better the AC75 style whistling or the voice over

So it's official! Full 30kt recording for 2 seconds on GW60 (www.ka72.com/Track/t/484541)
And 30.6 off the Garmin which is obviously more inaccurate! (www.ka72.com/Track/t/484547)

What have I learned ?

Small foils are faster. Although I haven't anyone to work on this with, but I feel at 80kg I'm on the lighter side and appreciate the control and lower lift of a smaller foil. 337cm is TINY but let's you push down and feel the effect.
Shims are good for control but the manufacturer has warned me they add drag and should be avoided. I've decided to use a tiny 0.7mm (1.5 degrees I think?) shim to help with control, since you can't go fast if your not. Bigger shims are helpful as you learn to control the speed but I haven't used 2mm shims for a while.
Shorter Fuselages are faster. Longer fuselages are more stable and long+ version (much) more powerful, and don't seem to be that much slower if you compare my Nautical Mile from yesterday (www.ka72.com/Track/t/484459) on 115+ with today. I'm sure, side by side less drag would be good, but depending on your setup 30kts and more is definately achievable with power, just make sure you can keep the nose down (I couldn't!).
Rear Footstraps are Great! It's taken me a while, but I've learned to love my back strap.
Foil Sails are Nicer! Definately not absolutely necessary (I was using a 5.0 S2 Venom slalom 4 cam sail to crack 30kts). My 7.0 Loft SkyBlade gave me great confidence to push (rather than hang on for dear life) but that might also be the conditions... smaller swell when riding a 7 vs 5m sail!
Flat Water please! You can't go fast if your bouncing off swell. Water is SO SLOW if you drag your board down so make sure you keep your altitude steady.
Mast Base takes some adjusting! For 20kts I really like my slalom setup at 132cm from the tail, but at 30kts I need it at 135 or 136. If you sheet in and nose dive, move it back. For pure speed you want to be a little back foot heavy and drive off the fin. Fun!

I just had a blazing 30knot peak session between SGSC & GRSC on George's river in a gusty 10-25+ knot SW-S-SE. Felt as gusty as typical W! The setup:
FMX 178 LR Hyperion 91 wide board was awesome. Felt like the rake should have been higher than 1.5? and mast base maybe 1cm forward of 132 setting but overall pretty stable!

Loft SkyBlade 7.0 dedicated foiling sail was super stable. Had it rigged to the trim dot but maybe should have given it an extra 1cm downhaul to compare. Didn't try. Too cold.
F4 560cm2 front wing mounted on 100cm fuselage with larger slalom rear wing 210cm. No shims! brave? stupid? Fast! Could have done with a small shim in hindsight!

The ride was amazingly comfortable at 25-28 knots. and absolutely on edge of my ability at 30! The reaction time needed to move as little as 2cm or 50% body weight depending on the gust and water state takes commitment. A few times I had to slow down because I knew I was getting fatigued or distracted. And a few times I was too late