I've noticed that people are able to build faster prop racers than me, so I'm after advice to improve my technique. As an example, I'll use my prop racer from the Trench Run tournament: https://www.simpleplanes.com/a/ROIy7B/GP-108-2-Penlan-Mk-2
It seems that there's a few areas where there might be room for improvement.
1) Aerodynamics / streamlining. The obvious problem here is having two engine pods, so nudging them into line or into each other is a possible improvement. What else could be done?
2) Control surfaces / handling. OK, control surfaces create drag and slow the plane when they're used. Making them smaller might help keep the speed up, but that can make it difficult to get round the course. Is this just a matter of tweaking it and using the smallest control surfaces that will get the job done? Or is it better to have larger control surfaces to turn more tightly?
3) Overall size and weight. Is it better to go with a very lightweight design? Or is it more to do with the power to weight ratio? I think it's the power to weight that matters more, otherwise multi-prop designs wouldn't do so well, but I'm still open to suggestions. And I don't think the plane size matters too much - having more wing area can make your plane wider, but lower wing loading seems to help handling. Similarly, a large tail keeps the plane stable.
4) Engines. Obviously, propellers are set to maximum size, power and thickness. The one thing I haven't messed around with is the pitch control settings - mostly because it's gone wrong whenever I've tried. Is this something I need to get a handle on to make better racers? If so, are there any suggestions for settings to try?
Inline engines are definitely a good idea, as well as making sure a nosecone is in the front as opposed to an engine. Smaller control surfaces do help keep speed up. What you need is the CoM to be very close to the CoL and have the biggest control surfaces you can while still maintaining control (they will still be very small if you get the CoM right) and a higher thrust/weight ratio is always better. As for propellor pitch, manual pitch at about 75 degrees gives the highest top speed, but for some reason you need to set the starting pitch to 0, set the pitch range to 75, and make it respond to throttle and it drastically improves you acceleration. Also warbird blades are the best
For pitch there are certain angles you want. For the turboprops you want 70% tilt and for the normal one you want 60%. That will help lots