A-Class foiling sailors

[flyinggorilla]

@flyinggorillaI've watched your videos and really like what you do.  You should be proud.  I have noticed your leeward board let go from time to time myself and think it is too much.  I have wondered if it is because you have what I think are the original F1 boards or technique.  You already have good feedback on the boards and set up so I will focus on the latter.

I don't see you moving your front foot or body much and would start there with more adjustments to be able to control pitch of the boat.  You are too rigid.  You can even steer with your back foot as the boat is so easy to rotate on the foils.  Watch the videos of the most recent Worlds and you will see people being very active on sheet and body placement and footing.  It was required to be super active in body movement and steering to get through the chop at Houston Yacht Club and the purpose of all the movement is to keep the leeward board loaded evenly, not overloaded or out of the water.  The Nacra 17 sailors are tremendous in this respect as they run forward and aft as I guess those boats are difficult to sail well and can fall off the foils too.

It will take some practice but I think you can get fewer falls off the foils in this way and it will give you a lot of satisfaction to do.  Nicks and foil finish is important but your boards look to be working well and are just losing grip, something you can help avoid with your steering, trimming, and body weight to keep the boat a little lower in the water when there are waves.  And of course keeping the boat level is critical.  I see you heeling just before the first fall and that leads to you losing pitch control and that along with the heeling increases the load on your leeward board which increases the difficulty of keeping flow attached to it.  

The second fall looks to be after you turn up a little, maybe due to a puff.  Again the boat pitches up as you turn and then the boards go above the knuckle and then lose grip and ventilation begins. 

thanks, awesome tips. lots to practice now! 

I try to minimize footing and move body weight forward/aft as needed. But as you point out not agile enough. It seems even when just sheeting in 30cm, one needs to move body weight forward at the same time. Consequently that's why I often lost grip in the past when sheeting-in quickly to not lean windwards, as this reduces the forward pressure, letting the foils go above the kink. Got it. Thx!

 

[flyinggorilla]

A-Cat z-foils ventilate in cold freshwater easily. Foils have been sanded with 600P following the recommendation to use more coarse sanding in cold freshwater than in saltwater. Fixing all pinholes, applying hullkote, ensuring no finger-prints or sunscreen on it. And finally reducing foil rake to minimum to just be able to fly and managing body weight forward as the boat takes speed. However, still, watching A-Class catamaran world championship 2022 it seems they foil so much more stable.

Season 2022 is over, and I think I made a bit progress on ventilation. I changed 4 parameters, of which one was standing out:

• radius of foil leading edge
• water got a bit warmer over the summer
• rudder and foil rake
• body movement

My conclusion is that the biggest improvement comes adjusting rudder rake to less lift. I was simply flying too high most of the time and had too much lift on the rudder. That had lots of my weight backwards and also required more main foil lift. To fix that issue I added better rudder rake markers to properly reset them after sailing a leg and made further adjustments to the rake system.

The impact of the other changes is a bit harder to justify, but I give the improved leading-edge radius a bit of a credit, and water and body movement the rest.

To better tune the leading edge, i created a tiny 3d printed tool. That is modeled after a NACA airfoil profile with similar proportions than A-Class main foils. That should be a better approximation than a circle shape. https://www.thingiverse.com/thing:5594872

Here is also a club-racing video of those "tunings" in use.


Have a good winter,
FG

 

[martin 'hoff]

@flyinggorilla very interesting! Do you know your rudder aoa before and after? Or the delta in degrees?

 

[flyinggorilla]

@flyinggorilla very interesting! Do you know your rudder aoa before and after? Or the delta in degrees?

the delta was approx 0.7 degrees. on the DNA this means the upper rudder gudgeon moved 3mm forward.

 

[flyinggorilla]

Got my new Exploder AD3, an A-class catamaran that flies on hydrofoils. The sail is from world champion Steve Brewin and the mast is from Austrian manufacturer Fiberfoam. This is my maiden flight with this amazing boat. Will it fly? Watch and find out! The water temperature was 10 degrees, fresh-water, and the foils were factory prepared and not yet sanded. The true wind speed was approx 10 knots, with gusts of 15 knots. My top speed that day was 25 knots. I plan to publish some comparison to my DNA F1x, which got an upgrade over the winter too.


So far I can say that the AD3 Exploder foils are more stable than the DNA F1x foils (from 2019). Rudder rake system works like a charm, very smooth and easy to adjust. Also foil rake is smooth and easy. I chose the short arm for mast rotation, that works perfect too on the fiberfoam mast.

The only challenge I have right now is to grab the mainsheet more precisely at the right position, so to not accidentally uncleat the traveller sheet. That happened several times, also as I am so far used to the DNA which has a control lines for the traveler, that is separate from mainsheet. I guess good for a quick bear away, but ugly if you are on the foils flying +20kn. How do you release the traveller at the buoy for the bear away? with mainsheet in tiller-hand and traveller sheet in other hand? or differently?

cheers FG

 

[he b gb]

Got my new Exploder AD3, an A-class catamaran that flies on hydrofoils. The sail is from world champion Steve Brewin and the mast is from Austrian manufacturer Fiberfoam. This is my maiden flight with this amazing boat. Will it fly? Watch and find out! The water temperature was 10 degrees, fresh-water, and the foils were factory prepared and not yet sanded. The true wind speed was approx 10 knots, with gusts of 15 knots. My top speed that day was 25 knots. I plan to publish some comparison to my DNA F1x, which got an upgrade over the winter too.


So far I can say that the AD3 Exploder foils are more stable than the DNA F1x foils (from 2019). Rudder rake system works like a charm, very smooth and easy to adjust. Also foil rake is smooth and easy. I chose the short arm for mast rotation, that works perfect too on the fiberfoam mast.

The only challenge I have right now is to grab the mainsheet more precisely at the right position, so to not accidentally uncleat the traveller sheet. That happened several times, also as I am so far used to the DNA which has a control lines for the traveler, that is separate from mainsheet. I guess good for a quick bear away, but ugly if you are on the foils flying +20kn. How do you release the traveller at the buoy for the bear away? with mainsheet in tiller-hand and traveller sheet in other hand? or differently?

cheers FG

That is one awesome looking machine!

 

[AndreasBerlin]

Exploder is a great boat It's going to be fun!

 

[martin 'hoff]

Got my new Exploder AD3, an A-class catamaran that flies on hydrofoils. The sail is from world champion Steve Brewin and the mast is from Austrian manufacturer Fiberfoam.

@flyinggorilla – looks like so much fun! Do you need help for 2-boat testing?

 

[flyinggorilla]

Do you need help for 2-boat testing?

@martin 'hoff you are more than welcome, and you know where to find me. the upgraded DNA F1x is ready as well. ;-)

 

[Lost in Translation]

The only challenge I have right now is to grab the mainsheet more precisely at the right position, so to not accidentally uncleat the traveller sheet. That happened several times, also as I am so far used to the DNA which has a control lines for the traveler, that is separate from mainsheet. I guess good for a quick bear away, but ugly if you are on the foils flying +20kn. How do you release the traveller at the buoy for the bear away? with mainsheet in tiller-hand and traveller sheet in other hand? or differently?

cheers FG

Hi FG,

I've got a 2020 eXploder. It is a great boat, and I've had 6 A-cats before. Looks like I have the same traveller set up as you. It has not been a problem for me as it is pretty close to a traditional traveller on a catamaran in terms of control line.

For me the mainsheet and traveller are the same line. If I want to drop the traveller, I pull the line to me while on the the wire, keeping coils of line in the tiller hand, and ease the traveller. The traveller doesn't ease that well for me without releasing a little mainsheet tension too.

I am amazed how in medium breeze you can sail with the boat without easing the traveller at all, both upwind and downwind foiling. Makes the boat really easy to sail as the rudders are almost the only thing to change.

 

[galacticair]

Got my new Exploder AD3, an A-class catamaran that flies on hydrofoils.

Great to see the new boat @flyinggorilla. Looks like a weapon.

I ended up buying a 2016 Exploder AD3 (with rudder upgrades + new boards) last year. Took a while to get it transported from Australia via container, and I’ve only been sailing it every 2 months or so (busy with work & family). It’s been a fun challenge, though I’m still learning to stay on foils more than a few seconds... It took me 4-5 sessions to realize I needed to lock the boards & rudders to prevent them sliding up (like in your video). And about the same time to realize my board rake settings were way too aggressive and I was getting up too high on the foils (thus rapid loss of control). I need to work more on body movement at takeoff, with lower rake. And I’m only starting to figure out rudder rake (I only recently got it calibrated).

One question for you & @Lost in Translation: after takeoff, I frequently find that my leeward hull rises way too high, while my windward hull is only barely foiling, leading to negative heel and a very precarious situation (risk of body dragging in the water & then capsize). I’m guessing this is partly due to the excessive board rake. But I’m wondering what is the proper trim response to equalize the heel when in negative heel?

Everything I’ve read suggests that to immediately increase ride height I should do a mix of: body weight back, unload foils (bear away, sheet out main). But in the case of negative heel, the leeward hull is already too high, so that doesn’t seem appropriate. But the windward hull is too low, so…?

 

[galacticair]

I ended up buying a 2016 Exploder AD3 (with rudder upgrades + new boards) last year.

Also, a general thank you to everyone on this thread (and other A Class threads in SA). All the advice here was a big factor in getting me to pull the trigger on a foiling A cat, and also guided me to a suitable AD3 model as a starter foiler. Special thank you to @SimonN, @lostintranslation, @flyinggorilla, and probably a few others I forgot to name.

I’ve started compiling an A Cat “Foiling 101” guide based on advice across SA, the A Class Facebook group, and various YouTube videos. This is more about basic technique, rather than tuning. I’m happy to share it via DM - I will probably share it more openly once I have a better sense of what actually works. It’s intended for people like me who don’t have ready access to foiling expertise/training and want to tap into some wisdom of the crowds.

 

[Lost in Translation]

congrats @galacticair . Windward roll is the hardest thing for people starting out and appears to be common for foilers in general, not just the A. You ease the sail to fly, the boat accelerates and the apparent wind goes forward, and then you roll to windward as you loose heeling moment from the sail. It's pretty much guaranteed if you stay static and is an art to master.

Here is someone talking through her process: . You can see her sheeting on after take off among other things to see the boat's roll in balance. Roll is your flight control as much or more than pitch. Pitch is mostly for take off.

 

[galacticair]

congrats @galacticair . Windward roll is the hardest thing for people starting out and appears to be common for foilers in general, not just the A. You ease the sail to fly, the boat accelerates and the apparent wind goes forward, and then you roll to windward as you loose heeling moment from the sail. It's pretty much guaranteed if you stay static and is an art to master.

Here is someone talking through her process: . You can see her sheeting on after take off among other things to see the boat's roll in balance. Roll is your flight control as much or more than pitch. Pitch is mostly for take off.

Thank you for sharing, great video. Very helpful to have the voiceover to guide on what is happening (I miss a lot of details when watching regular videos without running commentary). I watched it a bunch of times at 0.5x speed to really observe the sequence of body vs sheet movements, very helpful to see.

Body movement: looks like she leans way back to initiate foiling & then steps forward nearly immediately when foiling starts. I hadn’t been nearly as aggressively in both directions.

Sheet movements: I had read that you need to move the sheet a lot, but the video shows just how much - way more than I had imagined. I’m not sure my mainsheet demultiplication is the same as in this video, since my sheet doesn’t seem nearly as easy to trim…

She doesn’t show a full gybe. Does anyone know of a good video with full gybe sequences?

I’m especially interested in seeing technique after the gybe. In particular, do people run any rudder diff downwind and then adjust it each gybe? I’ve read it’s common to run 0.5-1 deg diff downwind (she mentions 0.5), but to me it seems like it really cuts the flow of the gybe to grab the diff line and yank it the right amount.
(again maybe my setup isn’t ideal - I don’t have a diff indicator and my rudder angle indicators are by the rudder itself, so I need to glance back at one or both rudders to check the diff as I adjust it; plus I find adjusting it at speed is impossible so I need to slow way down)

 

[Revelry]

Thank you for sharing, great video. Very helpful to have the voiceover to guide on what is happening (I miss a lot of details when watching regular videos without running commentary). I watched it a bunch of times at 0.5x speed to really observe the sequence of body vs sheet movements, very helpful to see.

Body movement: looks like she leans way back to initiate foiling & then steps forward nearly immediately when foiling starts. I hadn’t been nearly as aggressively in both directions.

Sheet movements: I had read that you need to move the sheet a lot, but the video shows just how much - way more than I had imagined. I’m not sure my mainsheet demultiplication is the same as in this video, since my sheet doesn’t seem nearly as easy to trim…

She doesn’t show a full gybe. Does anyone know of a good video with full gybe sequences?

I’m especially interested in seeing technique after the gybe. In particular, do people run any rudder diff downwind and then adjust it each gybe? I’ve read it’s common to run 0.5-1 deg diff downwind (she mentions 0.5), but to me it seems like it really cuts the flow of the gybe to grab the diff line and yank it the right amount.
(again maybe my setup isn’t ideal - I don’t have a diff indicator and my rudder angle indicators are by the rudder itself, so I need to glance back at one or both rudders to check the diff as I adjust it; plus I find adjusting it at speed is impossible so I need to slow way down)

Generally I have found running diff downwind really effects your pointing. With no diff you can get really low which is good in waves and for VMG. If you've shot past lay downwind you can diff on a bit to help get up to the mark.

My rudder rake downwind goes from +1 (or more, if experimenting) both sides in the ultra light to 0 in ultra heavy.

So through the gybes I don't touch diff really, but here NZ it's hard to know what the fashion is!

A near foiling gybe as follows:
Roll in with a bit of ease, it's ok if the leeward hull touches down but keep the windward one flying. Flip the tiller to the leeward side and cross under the sail before it gybes. Then hold on to something as you grab the tiller on the new side and give it a shove to pop the sail over. You'll come out still foiling but then hooking on becomes another thing. The quicker you do it, the better the outcome, but beware of the G forces when you make the turn.

 

[Lost in Translation]

For a 2016, I would not run diff downwind like Revelry says.

For 2020 and newer eXploders, a little diff seems to bring stability. Those boats also often have 12:1 mains as they are more geared to upwind foiling with very high sheeting load needs.

The biggest loss in jibes is getting going on the new jibe. Easing mast rotation can help as well as just lots of practice.

 

[Revelry]

For a 2016, I would not run diff downwind like Revelry says.

For 2020 and newer eXploders, a little diff seems to bring stability. Those boats also often have 12:1 mains as they are more geared to upwind foiling with very high sheeting load needs.

The biggest loss in jibes is getting going on the new jibe. Easing mast rotation can help as well as just lots of practice.

Great to hear - Yes our newest boats here are pre-2018 so intel on 2020+ performance would be great.

I'm assuming the extra diff downwind means you come out of the gybe a bit higher but bear away with more pace/sheet load?

I am running a 12:1 ish with full upwind foiling so understand those sheet loads!!

 

[BallRoughCat]

Hi everyone, great info here, thanks I have the problem with my pretty new Exploder that I can not get it to foil at all. I wonder: what is the reason for this? Am I maybe too heavy (220 lbs)? What are the effects of really tony dents/chips in the foils/rudders? Could that habe a great effect? Unfortunately no other A-Cats round here to ask. I am at a bit of a loss. Thanks 🙏

 

[Lost in Translation]

You can definitely feel the diff in the mainsheet load downwind. I'm not really sure if it causes much more of a heat up out of the jibe or not. The 2020 and up boats are really impressive.

When people don't foil at all, it is speed / lift oriented. You must be level and have 12+ knots of boat speed to take off. Flying a hull and easing the main to let the hull come down to level helps. The rudders are your elevators. Putting a lot of lift in them will hurt your ability to take off. Even a negative setting can be OK.

 

[Revelry]

Hi everyone, great info here, thanks I have the problem with my pretty new Exploder that I can not get it to foil at all. I wonder: what is the reason for this? Am I maybe too heavy (220 lbs)? What are the effects of really tony dents/chips in the foils/rudders? Could that habe a great effect? Unfortunately no other A-Cats round here to ask. I am at a bit of a loss. Thanks 🙏

I'm thinking too much rudder lift... I am also 220lbs. Mainsheet ease is important to get the nose to lift initially, then you have to rip it back in as soon as the apparent comes on.

 

[BallRoughCat]

Thank you, I will give it a try with less lift!