In an earlier post, Dieselfan mentioned smooth vs rough surface. Between a smooth surface as opposed to a rough surface giving more drag, it depends on the type of roughness.
As a wing or other object moves through the air, a boundary layer of airflow is created in direct contact with the wing. This boundaray layer of air moves significantly slower than the air which flows over it.
This boundary layer can be laminer (smooth) or turbulent. The turbulent layer does mix more with the air around it, causing more drag, BUT, laminer airflow also slows the air flowing over it down.
At 45-65mph it hardly matters, so I am just writing this for interest sake. It really only becomes important at speeds over 200kts. In fact, having a high drag aircraft such as a trike, with a good power to weight ratio, has some excellent benifits for us, and that's why we can land on soccer field, clear high opstructions into small field and land on farm roads. With a lower drag aircraft, planning your landing takes more skill, and you can run out of runway very quickly.
Anyway, shark's skin has a patterned roughness to it, which reduces the size of the boundary layer as they cruze through water. For many years boat, ship, submarine, surfboard, windsurfer engineers have copied this kind of roughness to give minimal drag in water.
It is now slowly being incorporated on the surfaces of faster aircraft, but because of the extra cost, we don't see too much of it yet.
Another interesting thing is that sound-waves have been successfully used to reduce the size of the boundary layer, so playing music to your wing might make you fly faster
Adding a fairing to a trike makes it a lot more stream-lined, but most fairing-less trikes are designed around the drag the undercarriage, pilot and passenger create, the position of radiators, airflow of propellors, length and position of hang point etc. etc. all play a role. If you are going for a fairring, do deal with someone who have paid their schoolfees, or get an aircraft originally designed with a fairing.
A fairing should not affect you cruze speed that much, your fuel consumption will benifit a great deal, and you could probably trim it a bit faster more easily.
BUT
Please remember that there is an optimal speed for each wing design. This is for trikes, conventional, gyro's, rotor's, propellors (also wings really) the works. If you are not getting the speed you want from your wing, get another design. Don't go messing with it yourself. It could compromise your safety.
- especally when itsa Gemini 
