i am building a cestna 182. almost finished.iwas installing the fuel tank that is located in front of the plane when it occured to me that full tank of fuel would will change center of gravity. when i first set cg should tank be empty or full of fuel.

Typically the C.G. is checked with an empty tank...
Perhaps more close to ideal would be to have it balance in the sweet spot (middle of the range, or just a little nose heavy ) with half a tank.

If the fuel tank is ahead of the CG then you balance the plane with the tank empty. If it's behind (such as in a pusher plane) then you balance with the tank full. So for the large majority of planes you will balance with the tank empty. There is a saying to remember here, "A nose heavy plane flies poorly, a tail heavy plane flies but once". When you balance with the tank empty the plane will become nose heavy when you fill the tank. Flying like this ok because you can still control the plane, and as the tank empties the plane will balance out. However, if you balance with the tank full as the plane flies it will become increasingly tail heavy, which will make the plane increasingly more difficult to control. And the last thing you want to do is run out of fuel and have to dead stick a severely tail heavy plane.

Hope this helps

Ken

Hey buckijim. Doesn't it say in your instruction manual whether to balance the plane with an empty or full fuel tank? (But I've never heard of a manual that instructed one to balance with a full tank.)

Most of the time the plane is balanced with the fuel tank empty. That way, the plane will start out nose heavy, but when the tank is empty it will be at its most "tail-heavy" balance point. If the designer/builder/instruction manual writer did his job correctly, the empty vs. full fuel tank situation will have been accounted for in their balance point testing.

What we usually do at GP is make certain the plane will be able to flair on landing on low rate elevator with a full fuel tank, but not unexpectedly tip stall or snaproll whenever full elevator is pulled on high rates with a near empty fuel tank. This way, the modeler should never get into trouble.

came with very little inst. just photos. not good at all. have had to ask a lot of questions to get it together. i flew in the 70s. been a long time, we did not have kits. everything was scratch. did not seem as tough as these kits they make today.grand kida found some of my old parts in a box, now i am coming back for these little guys. thanks to all for your help. i will probably be back with more questions before i get it finished.

Did not have kits in the 70"s? Wonder were they all went? I had them in the 40's

the Cessna will probably tip stall pretty easy.....If you haven't flown in 30 plus years...get help

Actually, I have found the Cessna (182) to be one of the most forgiving planes I have. It flys like a dream, practically lands itself. My Cub and Decathlon are WAY more prone to tip stalls.
YMMV
Paul

sorry tedmo. maybe they did have kits , don't know i came from the poor side of town, we didn't have hobby shops , jutt a few guys who played with these things, i do consider my self a newby as it has been so long. i didn't mean to fluff any feathers, just ask a simple question about something i didn,t know, i thought that this was the thing to do. i will not ask anymore, i think newbys will be reluctent to ask questions when all they get is a smart ass answer. have a good life, you will hear from me no more.