BLOOP 4 Twin


Captain Turnbuckles
Supporting Member
Jan 3, 2023

There have been lots of posts on Redundancy lately. For the Bloop 4 I have in progress, that is a Moster 185 + Hand Deployed Parachute. For quite some time I was toying with the idea of twin electric motors for simplicity and reliability. It's not going to give me what I desire in mission range just yet. Watching Mike Sandlin's Bluebird fly, I'm strongly thinking about doing dual Atom80s. Think Lazair but as a twin pusher. One motor wouldn't be sufficient for most takeoffs but could get me back to field should I lose an engine. I may also be able to extend the TBO if I can run lower RPMs with the ever so slight increase in thrust.

I know I'd lose some efficiency spinning two props. I'd also add some weight having dual motor mounts, fuel lines, throttle linkages, frame bracing, ect. It would also give me a frame I could change over to Electric someday should I get too many noise complaints or battery tech catches up. I'm also considering this as I'm (175-185) 25-30lbs heavier than Mike Sandlin. So instead of adding weight to the tail or shifting the pilot position from the plans I could add this motor!

I can run models on weight, balance and thrust numbers... what I don't have a clear understanding on is how the turbulence from the propwash coming from each side will change performance. I ponder this as many twins have twin tails. Has anyone here placed two engines on a single engine design? The numbers seem to work out but will two motors change the wake on the rudder and elevator much? Mike Sandlin's Bloop 1 was a twin tail and may have been best suited to the twin Atom80 setup.

BLOOP 4 (without motor) - 168-178lbs
With Moster 185 - 200-210lbs - Thrust 171lbs (2 blade 130cm) 8500rpm
With Dual Atom80 - 214-224lbs - Thrust 242?, 121lbs each (2 blade 130cm) 9650rpm - ideally, with the extra thrust, I'd back down the RPM quite a bit.

On the weight, I feel I have enough wiggle room for added frame supports, motor mounts and what not to double. Vittorazi has a new Cosmos 300, that may also qualify... but it's new, not as well proven as these two motors. I'd like to keep the motors separated as opposed to linked, spinning a single center prop. She'd probably fly a little faster and stall speeds changing of course but hopefully not too much.

Bloop 1.jpg
Thanks for the ever interesting points of view and words of wisdom!
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