Originally posted by springer
I'll just offer you a few words of unsolicited (and probably unwelcome) advice, based on 7 years' involvement with the UK version of this comp.
Many competitors place too much emphasis on max weight and too little on controllability. When your model is staggering around, you have to be able to guide it, preferably without the need for exceptional flying skills.
Undercarriages are often far too weedy, with high rolling resistance. Make some sturdy tricycle gear with ball-races. It doesn't matter if it's draggy, 'cos you'll only be flying very slowly. Some competitors use undercarriages which are designed to deform on landing, absorbing some of the shock.
Make every effort to prepare the model well in advance of the comp, i.e. test fly it and sort out all of the annoying problems.
Consider your cargo bay. If you are under time pressure, rapid access to the cargo bay will be a huge benefit.
Propellor gearing works a treat, as long as the engineering is simple and rugged.
Don't ever be tempted to compete with a canard.
Keep it as simple as you can.
Springer
Hi Springer; Your advice is certainly welcome, and your ovservations are very good, especially the last one.
Are reduction gears allowed in SAE? I would definately employ one, if they are allowed, because a large, slower-turning prop would be, as you said, a treat for this low-speed competition. There are commercial gears on the market, for large electric motors, and I hope they would be allowed. The class doesn't have to fabricate the radio gear, or the rubber tires, so hopefully they could purchase a reliable reduction gear.
Tell me more about your observations of canards. Too small a canard would be a problem with the low speed and high-loading involved. I was thinking more of a tandem wing design, actually, with the forward wing close to the ground (for obvious reasons) and the aft wing atop a pylon. Variable camber (flaps) on the center section of the aft wing would allow it's lift to be adjusted to match the forward, lower wing while it's in ground effect, and once aloft and at speed the flaps can be reduced.
Here too, canards have not been successful, but both those I saw had too small a canard, in my opinion, for a highly-loaded application.
Stability and control must be achieved, even at the expense of maximum lift.
Are you familiar with the Russian "Ekranoplans?" (Sometimes called the Caspian Sea Monster) Good model for a weight-lifter. I wonder why we haven't seen a commercial cargo-carrier version?