> > >  > >Ken,

 > >>  >
 > >>  >The Russian company Beriev had this interesting amphibian at OSH
 > >>  >Look how close the wing is to the water for ground effect
 > >>  >and the length of the  wing strakes. The Russians know a lot about
 > >>  >flight in ground effect. It was built with aluminum so composites
 > >>  >ought to be tougher and stronger.
 > >>  >
 > >>  >Look how fast it is with only 420 HP.
 > >>  >I think the payload number is a mistake.
 > >>  >That is probably less fuel.
 > >>  >
 > >>  >http://www.beriev.com/eng/be-103/be-103.html
 > >>  >
 > >>  >I think the idea will work on the Coot.
 > >>  >You could do away with the sponsons and their drag.
 > >>  >
 > >>  >Paul Lamar
 > >
 > >
 > >>     That is what Molt's idea was but on my new plane I raised the wing
 > >>  5.5 inches to get the thrust line closer to the CL of the prop.
 > >>    I was the first to put sponsons on the coot and they added 10 mph
 > >>  and everyone that has added them has reported the same gain in speed.
 > >>    I think that the V-hull is sending dirty air into the wing and the
 > >>  sponsons are sending that air under the wing instead making the wing
 > >>  more efficient.
 > >>    I am not impressed with the cruise speed considering the landing
 > >>  speed, that tells me there ain't no wing on it and any seaplane pilot
 > >>  will tell you that ain't going to work.
 > >>
 > >>  Ken
 > >
 > >Looks like a lot of wing area to me. In true ground effect a
wing becomes more
 > >efficient. Also the strakes will prevent the hull air from affecting the
 > >wing. Beriev really knows what they are doing when it comes to sea
 > >planes as they are the only company in the world to go into production
 > >with a jet powered amphibian. They have been doing this for many years.
 > >
 > >I will say mounting two engines on struts lowers the thrust line.
 > >That is one advantage they have over the Coot configuration.
 > >
 > >Paul Lamar

 >    Seaplane pilots have a saying that the only difference between
 > water and concrete is that water is wet and at an 85 mph landing
 > speed this plane is a piece of junk and any seaplane pilot will tell
 > you that.
 >
 >   Also with a high thrust line that plane will takeoff at 10 to 15 mph
 > faster than the landing speed so that will put you bouncing across
 > the waves at nearly 100 mph.
 >
 >   You just cant have a fast seaplane as there will be a compromise
 > somewhere, yes under perfect conditions it will land and takeoff on
 > water but it is not a perfect world out there on water.
 >
 >   Now take a Beaver on floats that cruises at 110 and lands at 50 and
 > with the thrust line lower than the wing it will takeoff slower than
 > the landing speed, now you have numbers that a seaplane pilot will
 > drool over.
 >
 >   Another plane topping the list of a real piece of junk is the
 > Seawind, I am doing work on two of them and the owners want me to
 > test fly them and I said no way, I think it is safe to say I will
 > never get in one.
 >
 >    Ken Welter

There is no physical reason why a high thrust line should cause a longer
takeoff run. I can see how it would be more difficult to get on the step
if the elevator lacked authority to pitch the nose up. A longer tail boom
helps as does a larger elevator of course. That assumes the elevator is
in the prop wash. Also you might try adjusting the thrust line to a slight
down thrust angle. The only thing that really matters is the thrust
to hull water drag ratio. That far outweighs any aerodynamic drag from the
wing. A dual engine airplane scores in thrust as the projected prop area
is much greater for a given amount of HP. Once the sea plane is on the step
aerodynamic drag becomes more important.

If the wing is real low when the airplane lands it will cushion the airplane
and cause it to float in ground effect. That is a very noticeable effect in
a Mooney say as compared to a Cessna.

Another factor in a high wing sea plane is the use of Fowler flaps
that drastically lowers the landing speed. Fowler flaps are possible
in a low wing sea plane but they must be very heavy  and strong indeed to
withstand the water impacts. Either that or rapid retraction when
the sea plane is about to touch the water.

   Paul Lamar

   No one has ever put flaps on a coot but I am building new wings
that will have flaps and they will be operated by an air cylinder so
that they will be very fast and if I hit a wave cylinder will act as
a shock.
  I already have the air system in the coot as my landing gear is air
operated by air and when I built the plane I installed the flap
system so its ready to go as soon as the new wing are finished.

  Ken

Good idea Ken.

If you stick a strong pito tube down below the hull a 
few inches and use the sudden increase in water pressure in the pito 
tube to trigger an air valve that automatically dumps the flaps I think 
that would work great.  

All airliners use a similar system by using the landing
gear squat switch to raise the spoilers over the Fowler flaps
to dump the lift as soon as the wheels touch down.

You should be able to lower the landing speed by 5 to 10 MPH by using 
Fowler flaps. No small amount as the impact energy is proportional to 
the square of speed. 60 mph squared is 3600 while 55 squared is 3025 
or 16% less impact energy. If you get it all the way down to 50 mph that is
2500 or 31% less impact energy than 60 MPH! A bunch and well worth doing.


Paul Lamar

 
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