CoosBayLumber,

Your idea of flaps hinged a little below the wing is a good way to get simplified fowler flaps. It would be best if you can get them to really blend into the wing when not deployed, but it isn't critical. For best performance, the relative position of the fowler flap and the wing can be fairly critical, but you can expect a big boost in lift, even if the positioning isn't perfect. A significant part of the benefit with this arrangement is that the flap, when deployed, increases the wing area in addition to increasing camber and angle of attack. A friend of mine built flaps exactly as you are describing, and they worked great. If you need to simplify the implementation, there is a big benefit to a large flap, say 30% of chord & as much span as you can get without taking away aileron, which deploys to 30 degrees or so. You can expect a bigger boost with a thicker wing, if you don't have to stick with an existing wing. If you do make a big flap like that, it will need a fairly beefy servo. If you need a ton of lift from the flaps, I prefer to use separate flaps and ailerons, so you can keep roll authority when flaps are deployed. For takeoff, you probably don't want split flaps, as they increase drag a lot, as was mentioned.

You may not get the kind of performance you are after, but it will be a fun project, and you can certainly get a big boost in lift.

banktoturn