RocHobby Critical Mass 1100mm Review
Review by Gunnar Hovmark, Staff Contributor
Transmitter: Spektrum DX6i
Receiver: Orange DSM2, 6 channels
Battery: Gravity 3 cell, 2200 mAh, weight 180 grams
Balancing weights: Zinc tire balancing weights, about 60 grams
- Nice handling qualities, especially a very quick and crisp roll response
- Very good retracts
- Good looks.
- Very distinct spin entry and exit
- Almost noiseless
- Needs a smooth runway
- Weak propeller
If you have a smooth runway and want a good looking medium sized aerobatic plane with a retracting main gear this is a good choice. If you don’t have access to a smooth runway it’s better to get something else.
This is the only plane I own that I haven’t chosen myself. I won it on a lottery, and I’m very glad I did. It’s the standard version, i.e. with a moderately powerful motor and made for a three cell battery. There used to be a high speed version with a more powerful motor, but I’m not sure that it’s still in production. If you want a high speed plane there are other choices from RocHobby though.
The Critical Mass has an almost flat belly and the wing is held in place with four screws from below. That makes it very easy to fit my home made skis to it. It’s my favorite winter plane.
My Critical Mass is a plug’n’play version, i.e. everything was in the box except the battery, receiver and transmitter, and weights to get the CG right. Assembly is easy. It took me about four hours, including waiting for the glue to dry and writing status updates on Facebook. The recommended CG position is surprisingly far forward, but you should definitely trust the manual on that. I glued a few tire balancing weights inside the cowl.
In the air the Critical Mass is a very pleasant acquaintance. The standard version is definitely fast enough for me. The roll response is excellent. It’s maybe a little too sensitive in pitch. I haven’t tried to use exponential travel on the elevator, but it might be a good idea. Spinning with the Critical Mass is fun. Both entries and exits are quick and distinct, but remember to have lots of altitude before you try it the first time. The Critical Mass is the quietest plane I’ve ever flown, not counting gliders. That could be a good thing if you have noise sensitive neighbors.
The retracting main gear is excellent. Mine has taken some rough treatment but always works flawlessly. However, I’ve had to straighten the aluminum struts after rough landings a number of times. That can be done by hand directly at the field. Another special feature is the split flaps. I always use them for landings, but I don’t think they make all that much difference.
The Critical mass has small main wheels close to the CG, and a small stabilizer. That means that it’s very prone to nose-over. My club field is a slightly rough and bumpy grass field, and I have never been able to land the Critical Mass on wheels there without a nose-over. Takeoff is also risky, so I always hand launch it, unless it’s on skis. The propeller is a bit weak. It snaps if it touches the ground during taxi or takeoff, i.e. when the motor has power. It has always survived my nose-overs though.