Just curious: Water landing question

"Mike Flying 8" wrote

Now I just wonder why the floats would stick?!?! I am going to have
to find something that I can read about this.

If you are able to get half of the water to actually be air, be it waves or
bubbles, that would mean you reduced the wetted surface contact by half, and
the drag by half. As much drag as water has, that would make a tremendous
difference.

Getting on the step, well, the step is the part of the float or hull where
the float takes about a 8" jump, upwards, so the back part of the float is
not as tall. (assume the top of the float is flat)

The step, (because it looks like an upside-down step) is usually slightly
behind the CG. When you get going fast enough, you are on the step when the
whole back (all aft of the step) is out of the water. You now are about half
out of the water, and have a lot less drag, so you quickly accelerate to
flying speed.

When you are going fast enough, you put a small amount of back pressure on
the stick, and get some more positive attack, and you pivot about the step
and the wing lifts you up and out of the water.

At that point, you can make a leisurely climb out, or if you have trees or
something to clear, you ease off and let the plane accelerate in ground
effect, the zoom up and over the trees on the bank.

So, getting on the step is the key to getting the plane quickly hauling ass!
--
Jim in NC

It is easier to get off of water with some chop to it because it
aerates the water. Air has less friction than water so the more
turbulence the hull can get beneath it the easier it is to break away
from the surface.

Getting "on the step" refers to reaching a speed whereas the hull is
planing at its "step" on the water like a speedboat. If you look at
the bottom of a float or seaplane there is a break or upward "step"
usually located aft and at a specific angle to the CG. The purpose of
the step is to enable the plane to rotate about a point (of planing)
while at speed on the water. If the step wasn't there the plane would
drag its afterbody when rotating for take-off

The distance it takes to get off of the water is largely dependent on
the aircraft, a very rough, general, off the cuff number under good
conditions at sea level would be a similar distance as that of a
similar land plane plus 30%-50%. However Seaplanes are much more
sensitive to increases in weight, and density altitude plays a large
hand in getting off of the water. Many small seaplanes/floatplanes
will start having trouble getting off of the water at gross weight
past a density altitude of 6000'.

D

That would be water's viscosity.

Every try picking up a glass from a wet, smooth counter?
--
-------------------------------
Travis
Lake N3094P
PWK
wrote in message
...
On Jan 29, 5:35 pm, Mike Flying 8 wrote:

Now I just wonder why the floats would stick?!?! I am going to have
to find something that I can read about this.

Something to do with the lowered pressure caused by the water's
velocity, just like Bernoulli says. Once you break free of the water,
the airplane accelerates quickly. Sort of like leaving a bunch of
draggy weight behind.
Molt Taylor, in his amphibious Coot, had air inlets just ahead
of the sterp, and air was ducted through tubes to vents in the
backside of the step itself to aerate the water a little. It got on
the step faster. If the water is a little choppy, getting off is
faster because of the same sort of thing: a bit of turbulence against
the hull reduces the water's hold on the airplane.

Dan

On Jan 29, 3:34*pm, William Hung wrote:
On Jan 29, 5:27*pm, "Robert M. Gary" wrote:





On Jan 29, 12:04*pm, Mike Flying 8 wrote:

Out of my pure ignorance, what does glassy water have to do with
TO/Landing distance? *I have been searching on the internet trying to
find something educational, but not having much luck. *

I would think the Landing would be longer because the lack of *ripples
would result in less resistance in the water, but I would think the TO
would be shorter for the same reason. *What am I missing?

I'm just a pilot and not a hyrodynamic engineer so I'll try my best.
The reason landing is longer is because you have no idea how high
above the water you are. So you try to cross over the shore around
5-10 feet and then just set up a slow decent until you feel the slash.
That tends to take up more space since you're waitng for the water.

The take off is longer because the floats stick to the water. I'm not
sure how to better explain it but you can certainly feel it. When the
water is choppy the floats come right off the water but when its
smooth you can actually feel the water pulling on the floats as they
try to pull away. Once the floats break free of the smooth water its
feels like you just got released and you feel a noticable speed
increase in ground affect.

-robert

Is this what they mean by "getting on the steps"?

No. Getting on the step means the floats are not so deep in the water.
They are riding higher in the water so there is less drag. I believe
the extra take off distance required of a glassy water take off might
be because of surface tension. You don't have that in waves. In any
case, I just fly them, I can't claim a detailed knowledge of why the
water reacts that way.

-robert

On Jan 28, 4:35*pm, es330td wrote:
What kind of space does it take to land/takeoff in a plane with
floats? *I realize there are all sorts of rules about where one can do
this but I have a relative with a ranch that has a fairly decent sized
body of water on it. *This is Texas, so its pretty flat with neglible
trees and I wondered if a plane could be put down there. *I tried
looking around a little online but couldn't find anything that spelled
it out.

Try searching for the Sea Plane Pilot Association for more info. Years
back when I did a lot of float plane flying in Louisiana and
Minnesota, a common technique was to motor around in a circle to chop
up the water just before takeoff if we were in a confined area. I flew
both floats and amphibs and my last seaplane flying was in a Cessna
206 on amphib floats here in Alabama last year.
Did a lot of demo flights for a Lake Amphib dealer in the mid 60's on
private lakes in Louisiana. Got my sea plane rating flying with Marion
Cole in Monroe, LA.

On Jan 30, 1:35*pm, Mike Flying 8 wrote:
*

Now I just wonder why the floats would stick?!?! *I am going to have
to find something that I can read about this.


Same as Coanda effect I think.

Cheers

*

Ol Shy & Bashful wrote:
a common technique was to motor around in a circle to chop
up the water just before takeoff if we were in a confined area.


That's probably the safest way. Another is to roll the plane into the
wind (if there is a cross wind) onto one float during take off. Or roll
back and forth to break water tension. Works but requires a bit more
finesse.

On Jan 29, 5:35*pm, "Morgans" wrote:

When you are going fast enough, you put a small amount of back pressure on
the stick, and get some more positive attack, and you pivot about the step
and the wing lifts you up and out of the water.

And knowing that exact amount of back pressure is what makes a
seasoned sea plane pilot. Too much back pressure and you'll just
muddle in the water, too little and you'll start to bobble.

-Robert

"Robert M. Gary" wrote

And knowing that exact amount of back pressure is what makes a
seasoned sea plane pilot. Too much back pressure and you'll just
muddle in the water, too little and you'll start to bobble.

"Bobble?"

That must be one of those new "highly technical" terms I'm not familiar
with. g
--
Jim in NC

"Morgans" wrote in news:6t3oj.34$Xi2.7
@newsfe02.lga:

"Bobble?"

That must be one of those new "highly technical" terms I'm not familiar
with. g

bobble [n]: 1: a repeated bobbing movement

bobble [v]: frequentative of bob

bob [vi]: 1 a: to move up and down briefly or repeatedly
b: to emerge, arise, or appear suddenly or unexpectedly