What i have is the Tower Hobbies 40 ARF trainer that my 10 year old trained on. They are affordable and the covering is what you get at the low price so it's stripped to the frame for a re covering(my first) job. The floats i'm installing are the Great Planes 40-60 's . The qustion i have right now is " The rec. CG is 3.5" on this plane with the trike gear installed and RTF. How do you figure the cg when the trike gear is not used. Balance with the gear and then remove to see if the cg shifts or stays? simply balance to 3.5 without gear and call her good? Got the basics figured i think,just this one detail where i can't the answer. HELP!!!!!!!!!!

CoG should always be the same irregardless of what gear you mount on your planes, whether it be floats etc

On my float planes I balance them with the land gear as per plans. Moving radio gear or adding wait to plane as need to get it correctly balanced. When I install the floats I rebalance the plane this time adding weight to the floats as need to rebalance the plane to the correct location. The imortant thing I find is insuring the step of the floats are 1/2 to 1 inch behind the CG of the plane, and that they are level to the datam line of the aircraft.
Sharpeye

Cubmaster126, If you find your plane (with floats added) is less stable than before, you might consider adding a sub-rudder just as with full-scale planes.

You might want to see my discussion on http://www.rcgroups.com/forums/showthread.php?t=249773&page=2 , (See Post # 19). Also try a Google search on airplane subrudders.

Virg.

By sub-rudders, are you referring to the added little vertical winglets added to the top and bottom of the elevator stab? And a flat bottom trainer wing is on a parallel line with the deck of the floats right? My book only explains the cub wing which isn't truely flat. Teaching my 10 year old to be a solo pilot seems easier at the moment with all the choices to make and right order to do things. Still have a LED light set to install before it gets covered also. So can I just assemble the plane with the step @ 1/2 behind the CG, wings parallel, then braces for the mounts, lights, covering, equipment, then balance at the new CG(book says it will move forward 3/8)? Is it that simple? Or do i have t maintain balance through out the whole build? Appreciate the help guys

Cubmaster126, Your mention of "vertical winglets added to the top and bottom of the elevator stab" would serve the same purpose as my suggesation of sub-rudders which would be located UNDER the fuselage, (sub = under).

Remember, I said IF you have stability problems with floats mounted, you could simply glue it on to the bottom of the fuselage at the aftmost location possible. You might GOOGLE the Japanese "Float Zero", the A6M2-N with its sub-rudder and then compare this with the ordinary Zero.

Don't forget, if you DO add a sub-rudder to see if it DOES make a difference on this particular model, you'll need to trim off some monocote so as to glue directly to wood.

Thanks Virg. Got the mounting all setup and figured. Got the braces in the fuse done for the float mounts and am going to leave out the lights, gotta learn to fly it before i get to fancy with things Have to make a 26mm riser for the rear mountfor the right AoA.I would like to upload some photos but one of my 3 boys has lost my card reader, have to get one this weekend. Well, gonna go see what damage i can do with some monocote