Floats on PT-20
01-07-2006, 01:37 PM
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Floats on PT-20
New to rc universe and newbie when it comes to communicating thru the internet. Patience --
With that said here is my question, I am currently building a PT-20 and have built a pair of Great Planes .20 size floats, if I read the instructions correctly, with a flat bottom wing the top of the floats and the bottom of the wing should be parallel? Instructions indicate with semi and symmetrical wings about 1 1/2 degrees of positive incidence should be used. Thinking of installing the floats parallel but a little voice in my head says to use a little positive incidence. What do you guys think and recommend? I currently fly a Seamaster off water and hope to use the PT-20 to train my son(with wheels on) and just another toy for me with floats. With a large river in my front yard I hope to make it my primary flying field. Thanks for your help in advance.
With that said here is my question, I am currently building a PT-20 and have built a pair of Great Planes .20 size floats, if I read the instructions correctly, with a flat bottom wing the top of the floats and the bottom of the wing should be parallel? Instructions indicate with semi and symmetrical wings about 1 1/2 degrees of positive incidence should be used. Thinking of installing the floats parallel but a little voice in my head says to use a little positive incidence. What do you guys think and recommend? I currently fly a Seamaster off water and hope to use the PT-20 to train my son(with wheels on) and just another toy for me with floats. With a large river in my front yard I hope to make it my primary flying field. Thanks for your help in advance.
01-07-2006, 10:34 PM
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RE: Floats on PT-20
The "true" incidence is from the farthest point of the leading edge to the trailing edge. So, on a PT20 with the thick leading edge that wing has, if your floats are parallel to the bottom of the airfoil you really have a coupla' degrees of incidence . My telemaster has about five degrees positive and it flies exceptionally well, but violates a lot of the "guidelines" .
If you get too much positve incidence, the plane will lift onto the nose of the floats and water-loop. You won't like that.
If you get too much positve incidence, the plane will lift onto the nose of the floats and water-loop. You won't like that.
01-09-2006, 02:15 PM
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RE: Floats on PT-20
JimCasey, many thanks for the response. Great Planes instructions leave alot to be desired. Your help clears up my understanding of how to set up the floats. Setting up with the bottom of the wing parallel to the top of the floats, will give me some positive incidence and I can adjust for more incidence with use of shims and will be cautious of too much incidence. certainly want to avoid "water loops". Thanks again - will be down in the shop tonight.
01-09-2006, 03:10 PM
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RE: Floats on PT-20
If my memory serves me correctly the PT 20 does not have ailerons and in true three channel tradition has lots of dihedral. If this is so you will have to be careful not to fly if there is more than a gently breeze as the wind will lift the plane over onto it's back if it gets caught crosswind while on the water. Even on trainers with ailerons it is best to remove most of the dihedral to prevent this from happening. I have heard that even Piper Cubs (full size) rig them with the dihedral removed if operating from water.
Peter
Peter
