I have a question that has been bothering me for quite some time. Someone once told me that if you want to build an indoor plane (electric slow-flight), it should only have the top of the wing covered and if you make an outdoor plane (gas), it should have the top and bottom covered. Why is this? I would think that if you didnt cover the bottom of the indoor fliers wing, then it would disturb the laminar flow in the front part of the wing earlier than it would be disturbed if it was covered on the top and bottom. Is it just for weightsaving reasons?

Here is two examples so you know what I am talking about.
Indoor - http://www2.towerhobbies.com/cgi-bin...?&I=LXBDF2&P=0
outdoor - http://www2.towerhobbies.com/cgi-bin...?&I=LXAP68&P=0