RCU Forums - View Single Post - New Somenized (TM) 69", Yak-54
View Single Post
Old 08-13-2007, 12:29 AM
  #94  
Brenner
 
Join Date: Jul 2007
Location: Bridgman, MI
Posts: 793
Received 9 Likes on 9 Posts
Default RE: 69" QQ Yak-54

cje0114 ,

If yours came in at 8.2 lbs, then mine with the YS 120 should be somewhere in the neighborhood of 9 lbs. That's still 1.5 lbs lighter than what I'm flying now, and only 22 oz/ft^2 versus 28 oz/ft^2 wing loading, definitely a big improvement.

Reza,

Unfortunately I don't have any direct experience with either the FZ,or the DZ as far as vibration is concerned, but the YS 120 AC can definitely shake an airframe up if all the stiffnesses, and masses are aligned. Usually I fly this motor in a pattern plane with a soft mount, and there's no problem at all, but right now it's hard mounted in a built up Goldberg Sukhoi, and in this airframe the motor will resonate with the airframe at about half throttle, but it smoothes out at max throttle, so most of the time the vibration isn't much worse than a light buzz. I'm hoping that the Yak 69 " will behave similarly, because I'm not enamored with the idea of replacing the light plastic engine mounts that come with the Yak, with a heavy soft mount.

How did you guys design a plane that's 2lbs lighter than the Goldberg Sukhoi, with 10% more wing area? Structurally, is the Yak 69" similar to the Goldberg Sukhoi? I notice in the online manual that there are lots of big holes in the structure around the engine mount. Is this structure going to be strong enough in the presence of engine vibration.
Brenner is offline