retractable floats?

Any designs out there?
...... just curious. I've never seen anything like that.

Wouldn't it be cool to retract conventional floats?

"Richard Riley" wrote in message
...
On Sat, 16 Sep 2006 14:19:02 -0500, "dlevy" wrote:

Any designs out there?
..... just curious. I've never seen anything like that.


There are the retractable wingtip floats on the Grumman amphibs - I
think they were an option on the Widgeon and the Goose. Those are the
only ones I can think of.

There are the retractable wingtip floats on the Grumman amphibs - I
think they were an option on the Widgeon and the Goose. Those are the
only ones I can think of.

And the Consolidated PBY "Catalina".

Richard Riley wrote:
On Sat, 16 Sep 2006 18:51:57 -0500, "dlevy" wrote:

Wouldn't it be cool to retract conventional floats?

Cool? I guess.

It would be complex - probably significantly more complex than
retracable landing gear. I'm not sure you'd actually save any drag.
Floats are big, when compared to the fuselage. So you'd have to
increase the size of the fuselage to contain them when they retract.

You'd reduce your wetted area some. Weight would go up. My guess is
you'd end up with an airplane that wasn't any faster.

OTOH, you could think of a flying boat as one with the floats
permanantly retracted and faired in.

Richard, just thinking offhand here, with two glasses of a sweet red
wine, and counting.

Think of the Dyke Delta's gear retraction, with two sets of legs.
Instead of pulling wheels into the fuselage, pull a set of floats up.
They could be semi-hidden in the fuselage to decrease the wetted area.

On Sat, 16 Sep 2006 18:51:57 -0500, "dlevy" wrote:

Wouldn't it be cool to retract conventional floats?

Umya where exactly would you like to retract then to?

"Ernest Christley" wrote

Think of the Dyke Delta's gear retraction, with two sets of legs.
Instead of pulling wheels into the fuselage, pull a set of floats up.
They could be semi-hidden in the fuselage to decrease the wetted area.

I'll bet you would not gain as much as you think. If it was half retracted
in the wing, the wetted area would be cut only in half. If it was just
pulled up to the bottom, you would only lose the wetted area of the top of
the float. With the CG relatively far forward on a flying wing, there will
be a lot of float forward of the wing, so even with retracting model, you
will not be able to even get half reduction, since the whole front part of
the float forward of the wing will still be hanging out in the breeze.

The "not gain as much as you think" part comes into play with the fact that
you are going to lose some by gaining interference drag, between the float
and the wing! Sucks, huh

Now imagine another problem. Think of the nose high attitude that the plane
has as it sits on the runway. You don't have that attitude as you are
flying through the air at a bit higher speed, like at pattern speed. Your
floats would be pointed tips down, at an angle of the difference of the
angle of the wing at pattern speed, and the angle of touchdown speed. That
would be a pretty big difference, right? All of that drag would be trying
to pull the nose down, and would no doubt take a ton of power, just to
maintain altitude, I'll bet!

All of that drag would be even a greater problem (I'm theorizing, now) as
you slowed for touchdown. Just as you are trying to pull the nose up, the
slower speed means you are starting to lose elevon effectiveness, and you
might not be able to get the nose to stay up.

Are you a sailing man? If you are, you will know the meaning of the word
"pitchpole." If not, it is when the tip of a hull (usually in reference to
a catamaran hull) digs into the water at a "hearty" speed, in your case
because you could not keep the nose up. The result is a forward, rapid,
uncontrolled somersault! Ouch! (at least! ) g

Fun thought problem, huh?
--
Jim in NC

Morgans wrote:

Fun thought problem, huh?

Well, it was until you showed how it is clearly impossible 8*)

Actually, the original post wasn't asking about putting floats on a
Delta, I was just saying that the mechanism chosen by John Dyke might
possibly be a solution for retracting floats. If I were to pick a
solution for floating a Delta, I'd change to a rear mounted ducted fan
engine and seal the belly.

As for all the aerodynamic effects or moving around a large portion of
the airplane, you weren't expecting a fully engineered solution in an
off-hand internet post, were you?

"Ernest Christley" wrote

Well, it was until you showed how it is clearly impossible 8*)

Actually, the original post wasn't asking about putting floats on a
Delta, I was just saying that the mechanism chosen by John Dyke might
possibly be a solution for retracting floats. If I were to pick a
solution for floating a Delta, I'd change to a rear mounted ducted fan
engine and seal the belly.

Humm, what about CG issues? Are you going to put the people way up in the
nose, or just add a large chunk of concrete where the engine used to be? g

As for all the aerodynamic effects or moving around a large portion of
the airplane, you weren't expecting a fully engineered solution in an
off-hand internet post, were you?

Well, from you, I expected nothing less, than an engineered design
modification plan, with all of the "t's" dotted, and the "i's" crossed! Or
something like that! ;-))
--
Jim in NC

Morgans wrote:
"Ernest Christley" wrote
Well, it was until you showed how it is clearly impossible 8*)

Actually, the original post wasn't asking about putting floats on a
Delta, I was just saying that the mechanism chosen by John Dyke might
possibly be a solution for retracting floats. If I were to pick a
solution for floating a Delta, I'd change to a rear mounted ducted fan
engine and seal the belly.

Humm, what about CG issues? Are you going to put the people way up in the
nose, or just add a large chunk of concrete where the engine used to be? g

As for all the aerodynamic effects or moving around a large portion of
the airplane, you weren't expecting a fully engineered solution in an
off-hand internet post, were you?

Well, from you, I expected nothing less, than an engineered design
modification plan, with all of the "t's" dotted, and the "i's" crossed! Or
something like that! ;-))

You set the bar much to high.

CG issue. It would have to be a nearly complete re-design, moving the
pilot really far forward with his feet crammed up into the nose, much
like the Air-Cam.

It's worth noting that the wheels on the Delta cause a nose-down vector
when in the down position. This goes away when they're retracted, but
is compensated for by the CG shift aft just slightly. The net effect is
no pitch change.

Many of the aerodynamic issues you brought up earlier could be dealt
with a combination of choosing different lengths for the front and rear
legs, and having the floats retract behind a stationary faring. I'll
work out some exact numbers some day AFTER I get the current one flying
with boring wheels 8*)

Long ago I came across an article in an aviation magazine
describing (and having photos of) a set of "retractable" floats on a
Cub. These were pivoted on fore-and-aft pins at the mains so that they
swung outward far enough to give the wheel (which was still there and
fit into a well in the float when the float was down) access to the
surface. There were various cables and struts to make the things work.
They had small tailwheels on them to keep the tips of the ground. The
whole setup seemed to work fine.
Wish I knew where I could find that article.

Dan