Cermark MB-339 any good?
06-30-2005, 12:26 AM
#1
Cermark MB-339 any good?
Getting back into turbines after some time off and am looking into new airframes for my Ram 750. I saw one in the classifieds for a good price and need to know is this a good plane or not? I fly from a 700' grass strip and I think the 750 will be plenty of engine. I liked the looks of the plane when it first came out, but was in no condition to by one at that time. There was a pretty good buzz about it when it first arrived, but then talk of it died out. I know it's out of production, but was that for lack of interest or problems with the airframe or both?
06-30-2005, 02:56 AM
#2
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RE: Cermark MB-339 any good?
IMO,
Its a proven JET ARF, yes it had some minor issues, but nothing major that would not want to make you own one, other then seeing many of them at the jet meets lol. I think the lack of interest comes from more of a better selection of jet arfs around back then.
Its a proven JET ARF, yes it had some minor issues, but nothing major that would not want to make you own one, other then seeing many of them at the jet meets lol. I think the lack of interest comes from more of a better selection of jet arfs around back then.
06-30-2005, 02:28 PM
#3
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RE: Cermark MB-339 any good?
I fly one with a SWB MAmba @ 20lbs ready to fly.
It flies very nice and has a nice look in the sky. With an Eagle Tree telemetry it's showing 110 MPH indicated airspeed.
I fly this setup on 400' hard surface it lands very nicely if C/G setup proper, if not it will bounce badly.
I plan to reduce inlets some to see its effect on airspeed.
The only problem I see with your post is that the wheel wells and gear length are maxed out at a 2" wheel and about 2" of strut so I doubt it would be a very good grass performer as the wheels will have a terminal velocity of speed in the grass and I'm not sure it would equal takeoff speed.
This plane in the 14lb RTF range would be a real performer, and it is doable with some effort and expense.
It flies very nice and has a nice look in the sky. With an Eagle Tree telemetry it's showing 110 MPH indicated airspeed.
I fly this setup on 400' hard surface it lands very nicely if C/G setup proper, if not it will bounce badly.
I plan to reduce inlets some to see its effect on airspeed.
The only problem I see with your post is that the wheel wells and gear length are maxed out at a 2" wheel and about 2" of strut so I doubt it would be a very good grass performer as the wheels will have a terminal velocity of speed in the grass and I'm not sure it would equal takeoff speed.
This plane in the 14lb RTF range would be a real performer, and it is doable with some effort and expense.
06-30-2005, 07:15 PM
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RE: Cermark MB-339 any good?
Tam has some mods that i would reccomend making on the airframe especially for a 20lb+ unit. I wish they would re-release this, as the price was right and the plane looked good. Russ
07-01-2005, 02:31 PM
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RE: Cermark MB-339 any good?
Have one with a P-80 and comes in at 20lbs. Flies very nice and the guy who did the test flight greased the landing.
The CG that was recommended to me by Tam is right at the front of the engine hatch line about 1" back from where Cermark recommends.
I did all the mods Tam has on his website, use caution as these mods will add tail weight and the moment is huge.
I ended up with all servos upfront and control rods running to the back for rudder and elevator.
From previous posts here on RCU do not skimp on the mods, these planes have been known to have some structual failures if the mods are not done.
Keep the speed at 150mph or less before putting any load on the plane ie high "G's"
Like the post above the wheels are small for grass and there is no option to go bigger unless you tear in to the wing and make the wheel well larger.
Good luck
The CG that was recommended to me by Tam is right at the front of the engine hatch line about 1" back from where Cermark recommends.
I did all the mods Tam has on his website, use caution as these mods will add tail weight and the moment is huge.
I ended up with all servos upfront and control rods running to the back for rudder and elevator.
From previous posts here on RCU do not skimp on the mods, these planes have been known to have some structual failures if the mods are not done.
Keep the speed at 150mph or less before putting any load on the plane ie high "G's"
Like the post above the wheels are small for grass and there is no option to go bigger unless you tear in to the wing and make the wheel well larger.
Good luck
07-01-2005, 04:20 PM
#7
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RE: Cermark MB-339 any good?
As for the C/G.
Make a 1/4" thick plywood plate that encompasses both wings spars using a slot, and extends up past top of wing for each wing half. Then drill a c/G hole in top edge of plywood plate that extends above wing top surface that is 4 3/16" behind the wing leading edge mold form of fiber fuse.
Then assemble plane Canopy and all with header tank full since it technically never empties, wheels down and use a hoist and pulley to lift up plane with string harness run thru the c/g holes in plywood plates.
This is my preffered method of balancing all my models, FWIW, I learned on an ARF Kangaroo and never once Kanga rooed it, I was unable to use any of the OEM precut mounting positions already installed for components. Ended up gutting it out. But thats what the C/G needed and I was'nt about to add weight.
I would call this a C/G lifting jig and it would be nice if they came precut with all model kits. C/G is very critical on these heavvily wing loaded models.
Make a 1/4" thick plywood plate that encompasses both wings spars using a slot, and extends up past top of wing for each wing half. Then drill a c/G hole in top edge of plywood plate that extends above wing top surface that is 4 3/16" behind the wing leading edge mold form of fiber fuse.
Then assemble plane Canopy and all with header tank full since it technically never empties, wheels down and use a hoist and pulley to lift up plane with string harness run thru the c/g holes in plywood plates.
This is my preffered method of balancing all my models, FWIW, I learned on an ARF Kangaroo and never once Kanga rooed it, I was unable to use any of the OEM precut mounting positions already installed for components. Ended up gutting it out. But thats what the C/G needed and I was'nt about to add weight.
I would call this a C/G lifting jig and it would be nice if they came precut with all model kits. C/G is very critical on these heavvily wing loaded models.
07-01-2005, 06:54 PM
#8
RE: Cermark MB-339 any good?
Ok, so you're using 4 3/16" back from the LE at the side of the fuse. I had one which lasted 200 flights and it balanced slightly aft of the hatch line. My new one balances a little behind that and is noticeably tail heavy on takeoff, particularly if not using the flaps. So I think I'll move some things around. Thanks.
