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Tip of Foil Breaching Surface

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Leelanau
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Tip of Foil Breaching Surface

Postby Leelanau » Thu Sep 07, 2017 6:04 pm

Long time reader, first time poster.

I have about 20-25 sessions under my belt on a LF Rocket Foil, the original low aspect shape. I've been progressing fairly well, have surface and touch-down jibes mostly sorted and working on fully foiling transitions and a little jumping and seemed to run into a frequent issue/challenge. Often on a foiling transition/carve I find the tip of the foil wing pokes through the surface, causes it to ventilate and I come crashing down. No way to save it as it happens so quickly. It's happening to me in messy swell when it's hard to time a carve for a certain point in the wave. I've been fine in flatter conditions, when the margin of error for proper elevation is greater.

For background, I mostly ride on Lake Michigan and on NW-NE conditions the most convenient places for me are totally exposed to maybe an 80 mile fetch, which makes for some sizable (but typically irregular) freshwater swell. I was out last night in 12-14 knots and was battling some messy wind chop on top of 3-4' rollers. I was specifically working on transitions in these conditions and was probably crashing on 3 out of 4, and as best I could tell, because of a ventilating foil. Mid-carve I lose lift and come crashing down, even when I'm being mindful of staying low enough to start the carve. For the first time on a foil, I wasn't really having fun.

So question is, do all foils suffer the same fate when the tip breaches the surface, or is this specific to some shapes? Same thing can happen when I'm healed over hard going up wind. I swear I've seen videos of others riding consistently with one tip poking the surface. Very few other foilers in my area and haven't had a chance to demo any other foils. Is this just something I'll need to work on/suffer through as I progress or are other foils more forgiving of this? Thanks.

borist
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Re: Tip of Foil Breaching Surface

Postby borist » Thu Sep 07, 2017 6:54 pm

Breaching is not a good idea. You can get away with some but not often. Are you sure you only poke a tip? I crashed often in bigger chop in the beginning before I got more experience, stopped slowing down too much and got better and maintaining correct depth. How tall is your mast?

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Re: Tip of Foil Breaching Surface

Postby evan » Thu Sep 07, 2017 7:19 pm

Seems like the racefoils with small wingtips that are sanded well are less sensitive to ventilating. I was surprised to see a photo of myself with a wingtip above the surface in a session I couldn't recall any ventilation issues:
Attachments
breach.jpg

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Peter_Frank
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Re: Tip of Foil Breaching Surface

Postby Peter_Frank » Thu Sep 07, 2017 7:21 pm

Hi Leelanau

What you experience is normal, and what happens to all of us.

There are differences in how "hard" a wing will ventilate, but yours is quite good at keeping lift, and can sometime regain after ventilation because of its sheer size - but other times it will "drop" you.


When you get more experienced, two things will happen (without you knowing, it simply takes a lot of time):

1. You will NOT get the tip or wing over the surface, not even in chop, very often.
2. When you do, you will be able to ride it out, more and more often.

But you will still, even when really experienced, get some radical wipeouts because of ventilation - it is just a part of the game that will happen now and then when you push it to the limit :naughty:

Yes, on some videos (especially the Ketos, Pink Lady at 1:48 :thumb: ) you can see part of the wing over the surface - this is a "stunt" so to speak, because she has good control, and can keep the rest of the wing stable under the water, using the lower part of the mast as a wing too while leaned over, and using the kite to get sufficient lift.
With raceboards you lean over too, and really powered, so here you can also ride like this often.

But when not having lift from the kite, and more upright, it is way more critical and you will often drop fast...

In short, all main wings might drop you hard when you ventilate, a bit different how rapidly they do it or regain, some are A LOT worse than yours, and a few might be better - but it is just how it is with all of them :wink:

8) PF

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Re: Tip of Foil Breaching Surface

Postby Leelanau » Thu Sep 07, 2017 8:04 pm

Awesome. Thanks for the feedback. Sounds like I just need to keep working on it. The flat water transitions started to click when I began taking more speed into them. Thinking about it, I may have been a bit more tentative yesterday given then conditions (and all the crashes). With more wind I find that I can hang on the kite to recover, it was light enough yesterday and with a 8m kite that wasn't really an option.

borist - I the full length mast, which is what I learned on. LF reports 100cm, but I think it's closer to 95.

Like so many things, it's tempting to believe that there's an easy fix (new equipment), when it's really just the operator that needs the work.

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Re: Tip of Foil Breaching Surface

Postby juandesooka » Thu Sep 07, 2017 8:41 pm

I'm no pro, maybe 25 sessions ahead of you, but a few thoughts to add.

I was going to ask too about full length mast, but I see you answered. This gives you more room to play with in chop. I am nearly always in chop and my board is normally only 6-12" above water surface, so when you hit 2' chop, wing still in the water. I find it helps to kind of pump in the swell, rising and falling with the waves, to lessen breaches.

I started on a super low aspect foil (carafino original) that had a very clearly defined top end. At too much speed, the wing breaches, and you go flying. So I learned the bad habit of jumping off when I got going too fast. When I got my mid aspect wing (stringy), it took a while to re-figure out top end -- which meant holding on when it felt like going too fast, and miraculously riding out the speed past beyond where I thought possible. Then came the same thing with turns, trusting that it will hold when digging in, even at speed. But a part of learning this trust too was that in mid turn if there's a slight breach and lose some lift, trying to hold on and power through it rather than allowing the semi controlled eject. Again I discovered that sometimes I could rescue it without a wipeout -- half the time or more maybe? So, if you're like me and have a tendency to jump off before you wipeout uncontrollably ... might be worth focusing on powering through for minor breaches.

Finally, the spitfire / canard style wings: these have both wings lifting, with a small front wing, and a larger rear wing providing the main lift. If the front wing breaches, the loss of lift is minimal not catastrophic, you sink down a little but keep on going. As I understand it, this is bad in a fighter jet, as a stall means falling backwards in an unrecoverable drop; but in a foil that is a design benefit, as dropping backwards means dropping down from foil slowly. If you have anyone locally who will let you try their spitfire, may be interesting to compare. [the other advantage, the radius of the turn can be much tighter, as the turning force is pivoting on back foot, rather than steering the front wing through a turn....that could be another thing to work on if you're losing lift halfway through carving turn, focus on completing the turn tighter and quicker, as opposed to a wide arc?]

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Re: Tip of Foil Breaching Surface

Postby marekmk » Fri Sep 08, 2017 11:28 am

I have the ketos easy wing and when the wing ventilates its very predictable and to keep it flying. I have flown other wing with the wing almost at the surface and been immediately thrown of............

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Re: Tip of Foil Breaching Surface

Postby davesails7 » Fri Sep 08, 2017 12:28 pm

The flatter the wing is at the tip, the less problem you have when it breaches. Riders who switched to the flat Sword wings noted this.

LF also notes this in their new Thruster video with thekiteboarder.com. The new Thruster is completely flat and they say you can ride around with large parts of the wing out of the water.

I have seen in the videos that those keetos wings can ride with a large part of the wing out of the water too! Their freeride wing looks like it actually has the wings angled up at the tips.

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Re: Tip of Foil Breaching Surface

Postby gbrungra » Fri Sep 08, 2017 2:32 pm

The SUP foils (GoFoil, etc) appear very tolerant of breaching. Which is good since they are being riden in surf w short masts.

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Re: Tip of Foil Breaching Surface

Postby Mossy 757 » Fri Sep 08, 2017 3:25 pm

I feel the need to live up to my reputation as the word police:

Breaching - when something underwater comes above water
Ventilating - when air is pulled underwater along a low-pressure gradient and attaches to a lifting surface displacing water and therefore not providing lift since air is less dense than water, this causes a "crash down."

http://lancet.mit.edu/decavitator/Basics.html

I've experienced ventilation by crossing through a tide line between waters of different densities/temperatures.
Guys with the original batches of Banga foils got a lot of ventilation from their struts and had to sand carefully to make it stop.
Ventilation sometimes occurs when a wing tip breaches, creating a little eddy that sucks air down along the wing.

Either way, it's kind of a separate problem from breaching. Breaching means you got the geometry of your riding position wrong and your foil got dry for a second. Ventilation might happen even if you're not breaching due to design characteristics inherent in the foil. Similarly, there are foils (Sword2 flat wing comes to mind) where you can breach without ventilating...


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