Neil
Getting a prop at 2.5 grams shouldn't be a problem with a 8 gram minimum airframe weight for SO. Don Slusarczyk put a 1.2 gram molded balsa prop on his in a build on RC Groups, and needs ballast to meet 8 grams.
I posted a test of the first bucket prop I made close to SO Spec on RC groups. The blades are from a clear poly propylene 16 ounce beverage cup. It weighs 3.1 grams with a hanger from a Delta Dart and a 1/32 wire hook. It measures 250 mm diameter which is easy to trim to 240 to meet the rules. It was a little slow on .080 wide rubber, so I tried 1/8 inch. At 850 turns on a 10.3 inch loop, weighing 1.8 grams, I got 200 seconds run time. Average rpm was about 250. I'll need to mount it on a Double Whammy to see if it has enough thrust for climb at 8 gram airframe weight. I made some more blades from a 32 ounce poly propylene deli tub that I drew using Fred Rash's Bucket Props calculator. The specs for that tub call for 0.4 mm thickness. I expect a prop made with them might be a little lighter if I pay more attention to the spar and hanger.
Good to see the interest in this. Hope it helps the kids and coaches.
Joe
Received on Wed Nov 19 2014 - 15:07:18 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:48 CET