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Dec 03, 2012, 11:52 AM
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weekend hack's Avatar

CMP Yak 54

Any one have this model? CMP Yak 54 .46-.50 size. I have had 2. I first put a .61 Magnum engine in it but it seemed under powered. Then I placed a Magnum .91 four stroke in it. Over all it seemed to be a good fit, as far as the cowl etc. It balanced by placing the battery to the rear. However, It flew heavy, during moderate elevator input it would (high speed stall?) snap roll to right. I thought it was over powered and possibly too heavy / high wing load. The landing gear broke during a light bounce. I replaced it with a metal gear. Any way eventually it met its demise.
I bought a second one recently placing a Magnum .60 four stroke, more along what was recommeded. To balance it I had to place the battery forward under the fuel tank and add an additional 12 oz ! of weight behind the engine. Now it still flys like the first one, heavy and wants too snap roll during moderate elevator input. The only thing I can think of is to extend the motor mount (considerably) to balance it so I can remove the 12oz of lead added. I will also have to add a few inches to the cowl...more work than I wanted to put into it. Anyone esle have this plane and have a similar problem?
Last edited by weekend hack; Dec 03, 2012 at 11:46 PM.
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Dec 04, 2012, 07:36 AM
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Give up, the CMP Yak was not the best plane in the world. You have hit upon it's problem... high wing loading and snap happy....
Dec 04, 2012, 12:02 PM
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Wow must be the design. I fly a Yak 50CC size and have no problems.
Have you tried reducing the throw a bit more?
Dec 06, 2012, 08:33 PM
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weekend hack's Avatar
Thats what I was afraid of, like they say you get what you pay for. Thanks for the reply. tomorrow I am going to test fly it. I extended the motor mount up 3 inched forward. We will see.
Dec 06, 2012, 08:42 PM
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weekend hack's Avatar
Yea, I have them set at the recommended throws. It is a conservative amount. When flying it, if you get into trouble and have to give anymore than mild elevator input, stand by she may snap to the right and if you do not have a good amount of altitude, shes going in.Glad your is flying well. Guess I should super size! Thanks for the suggestion
Dec 07, 2012, 10:11 AM
Registered User
A snap with full elevator can be a sign of too much throw...If you're not running out of elevator on landing try reducing the throws some.....the instruction on CG and throws are a starting point
Good Luck...I hope it's not the airplane

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