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hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 11:39 am
by slowboat
Obvious beginner question: What happens when you push a foil beyond its maximum speed?

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 12:40 pm
by Peter_Frank
slowboat wrote:
Fri Dec 01, 2017 11:39 am
Obvious beginner question: What happens when you push a foil beyond its maximum speed?

Hmmm, there IS not such thing as a specific foils maximum speed :roll:

The more power you can "invest" - the faster it can go.

There is a practical maximum speed though, the speed the really good riders are able to obtain, is what one determines as the "maximum" practical obtainable speed most often it seems.
Also, control is a big practical issue - as eventhough big lifting wings can go fast with sufficient power from the kite - it will be really difficult to control :wink:
Thus the smaller and faster wings are a lot easier to ride, when going fast.

Smaller and faster wings, do not need as much power either, to go fast, thus using the max power you can invest, you can go a lot faster with these.

However, when you reach more extreme speeds, cavitation (water is boiling because of local low pressure points around the wing) will set in at it will kinda stall at high speeds - but it will probably be at such speeds it wont be a concern for nor you nor me :rollgrin:

For thick and lifting wings, this will occur at lower speeds though, so might happen :naughty:

8) PF

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 1:07 pm
by Lokihel
You crash.


More often though you simply reach maximum speed. Sort of like any vehicle that reaches maximum speed. You may have your foot to the floor on the gas pedal, but it will not go any faster.

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 2:02 pm
by revhed
Peter_Frank wrote:
Fri Dec 01, 2017 12:40 pm
slowboat wrote:
Fri Dec 01, 2017 11:39 am
Obvious beginner question: What happens when you push a foil beyond its maximum speed?

Hmmm, there IS not such thing as a specific foils maximum speed :roll:

The more power you can "invest" - the faster it can go.

8) PF
Sorry, not, Bullshit alert! Fake news!
No one will EVER get a P O S L F funny or Cabrinha or Naish set up to go 40 knots, No matter how strong the wind or how big the kite used or how skilled the pilot is!
They will simply produce drag and not go any faster!
So there is MOST certainly any given KBHFs set ups max speed!
Simply physics no?
R H

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 2:11 pm
by Mossy 757
slowboat wrote:
Fri Dec 01, 2017 11:39 am
Obvious beginner question: What happens when you push a foil beyond its maximum speed?
You travel into the past/future leaving a set of burning tracks behind you...

Image

*serious answer

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 3:09 pm
by davesails7
Yeah, for good foils, you push in as much power as you can, and go as fast as you dare. Cavitation is a limit at very high speeds, but I don't think even the fastest foil riders in the world (40-45 knots) are limited by cavitation yet.

The faster you go, the faster your reactions need to be.

More efficient foils require less push to go the same speed.

I only rode the LF fish and Cabrinha foils briefly. Even at relatively low speeds, they just hit a wall where pushing harder just makes the whole thing stop working. It's been a while, but form my memory, when I pushed hard on the LF, somehow it lost lift. Not sure what causes it. I don't think it could be cavitation at such slow speeds.

In the end, I think the speed limiter for most is fear of crashing.

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 5:12 pm
by Mossy 757
davesails7 wrote:
Fri Dec 01, 2017 3:09 pm

In the end, I think the speed limiter for most is fear of crashing.
Do you think that the kites are the limiting factor for top riders? Like if Nico had a kite that could easily do 60 knots, would the foil follow along happily?

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 5:59 pm
by kiterocky
They will never go fast as a speed board....or jump higher than a twintip...or surf better than a real surf...but foil win in light wind always....

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 6:17 pm
by plummet
Yeah I agree with revhed and disagree with Peter. Each foil has a maximum top speed for its given set up.
What I find interesting is that nobody seems to talk about the stabilizer angles much? This highly affects your top speed. The slower you want to go the more aoa you crank on the rear wing. The faster you want to go the less aoa you want. So to tune a foil your really need to ask yourself what is your preferred speed. Then go about setting up for that.

You want more lift for low speed and less for high. This is precisely why planes have adjustable trim and flaps etc. However we have fixed settings on foils.

With a high lift setting you will have more drag, more stability and need to put more weight on the nose to keep the foil in the water at speed. So the maximum speed limit of a high lift set up is determined by the ability to stomp on the nose and counter act the lift.

I had my foil set up higher aoa for more lift, stability for learning. However when I fast I had to stomp on the nose to keep it down. I definitely reached the top end of that set up. By adjusting the stab to lol aoa ive increased that upper limit by at least 20%!

Re: hydrofoil at max speed limit

Posted: Fri Dec 01, 2017 6:23 pm
by plummet
Mossy 757 wrote:
Fri Dec 01, 2017 5:12 pm
davesails7 wrote:
Fri Dec 01, 2017 3:09 pm

In the end, I think the speed limiter for most is fear of crashing.
Do you think that the kites are the limiting factor for top riders? Like if Nico had a kite that could easily do 60 knots, would the foil follow along happily?
No. The limiting factor us not the kite. Snow kiters and kite buggiers hit 50-60+ knots with fairly low spec kites.

I have personally done around 50knots in my kite buggy on an old 10m edge. I've done been 45-50 knots on my 8m catalyst and 6m Reo!