I just purchased a RV-4 kit as my first low wing plane.
1 - I was told that flaps had little or no effect on this size plane.
2 - He said that I should build the plane with full-length (strip) ailerons, and then program aileron/flap mixing on my radio.

Opinions on both statements please (please, please)...

I have always enjoyed putting flaps on 40 size airplanes (all sizes for that matter)

With the current trend of using separate aileron servos, I have used Flapperons instead.

I will never do that again. IMHO, separate flaps are MUCH more effective, and if your plane is set up to use strip ailerons with torque rods to control them, setting up flaps is a breeze. Cut the aileron at a point that is about 1/3 of its length. Control the flaps with the aileron torque rods, and for the ailerons, either run flexible push rods from a center servo, or mount a servo in each wing.

Works like a dream.

What size is the RV-4? Normally for a small aircraft its not worth the effort for the amount of performance unless you are trying to go scale. Otherwise a 40 size aircraft can benefit from flaps, its not a necessity but a "neat" thing to have. There are advantages of flaps over flaperons. For instance, flaperons increase the angle of incidence over the entire span slowing the airplane but at the same time reducing the aileron effectiveness at the tips where is needed the most. While flaps only increase the incidence at the span section of the flap, leaving the wing tip incidence intact with plenty of aileron effectiveness. Problems with flaps? Its twice as much work as having just flaperons and more material and hardware making the aircraft heavier. Bottomline, its a personal choice.

That answers flaperons -vs- ailerons. Thanks.

Now, if I want to build without flaps (for now), should I use the full-length for aileron, or still split it and make the (future) flap area stationary?

I bought this plane after seeing one at my model field. I have chosen to put flaps on mine as my friend didn't have flaps on his and wishes he did to help slow it for landing. The standard size ailerons are fine and IMO don't need to be made larger. The roll rate for my friend RV is as high as you would want. Besides it looks really good with the flaps, very scale like.

I'm building an RV-4 with the flaps. I think that a 40 size plane lands pretty slow (relatively speaking), and that the flaps are not necessary. I want to get used to the flaps so that I'll be familiar with them for planes that really require flaps (such as a warbird). Just being able to find the knob quickly when you're under pressure is reason enough for me to include them. Plus it only costs $30 to add them. (that's 2 servos and a y cord)


Kerry

Flaps are a good idea. Since I lost my elevator in the air on my super cub (scared the hell outta me), I have been a flap fan. The flaps on the super cub helped me bring it back safely to a normal landing becuase they tend to pitch the plane up. Now, I don't know how they will perform on a 40 size plane, but I think they should help too. Just my $0.02
Victor

What I would do is make them the entire length, add the torque rods (even if you're not using them for ailerons) and add an extra hinge or two so that when the time comes, you just need to remove a 1/16" gap from the strip, and you have two control surfaces ready to go.