Weight vs. Drag?

[a6m2-n]

Which of these will restrict the performancxe of a plane more? What factors must be taking into consideration if I wanted to reduce one or the other. I want to know this for the sake of one of my float planes, I want to see how "aerobatic" i can make it. So i pretty much just want to know which of these factors I should consentrate on more. Any thoughts will be appetiated.

[Dave Robelen]

Hello a6m2-n,
Weight is a major player where aerobatics are concerned. As weight builds, so does induced drag, and the rate of climb is equally affected. This is most noticeable as you pull a heavy model to the vertical with modest power. It is almost like putting on the brakes.
As the drag is reduced, the level velocity can be increased, and more energy gained for the entry into the vertical pulls. Drag is a major enemy when there is limited power because it eats into the efficiency throughout the flight.
A heavy but clean model can be flown though manuevers much better than a lighter draggier one for equal power. This assumes equal power in both cases.
Regards, dave

[a6m2-n]

Thanks, on a similar note, how would a plane with a K&B .40 fly with a gross weight of 5 lbs? Would putting floats on it reduce perfromance drastically?

[Dave Robelen]

Hi,
You did not mention the wing area, but if it is ample a K&B 40 should do a creditable job. The idea is to get the model flying "on the wing" rather than depending on brute force to haul it through manuevers. Putting floats on a plane that already weighs 5 pds. with a K&B .40 would really cut into the aerobatic ability. The two floats add a bunch of drag just from their shape, and the added weight will increase the induced drag from the wing. Might be a bit of a dog.
Regards, Dave

[a6m2-n]

I heard somewhere (forget where) that the shape of modern floats have an airfoil so they will "fly themsleves" Is this true?

[Dave Robelen]

Hi,
I have never seen a float that could produce meaningful aerdynamic lift and still work well in the water. There have been some rather wide, blunt floats used on powerful free flight models, but these could be yanked off of the water by the engine involved. The best bet is the slender, planing float with a step on the bottom and a rounded top. Size the floats so that they are about 3/4 the length of the fuselage, the step is behind the CG a small amount, and their combined volume is adequate to float the plane. This type of float does a great job of accelerating on/in the water, and has about the lowest drag for the job.
Regards, dave