Ok i was reading the other thread about OS engine problems, and i got to wondering about my Fuel Tank. i went to my Nexstar and noticed that i could move the cell around and almost pull it out from the back, shouldn't this be a BIT more stable than this ??? i added some foam around it tonight, but i was wondering just how much foam can i add around the cell before i mess with the weight enought to make a difference.

Thanks Tim

Good catch!
the tank should be stable foward and side to side, up and down also . there is not much to cause it to slide backwards though.
foam is fairly lite but rechecking balance after any changes is wise. while you have the tank out tie a string around it for easy removal next time.
1/2 " of foam is plenty but you may not have that much space so do what you have room for. don't pack it to tight or the foam can't do it's job.

I use a type of foam than is used for packing artwork it tears into 1X1 squares, or strips,any shape you need, its very light weight, if you think the foam your using is heavy then just check the CofG if it's looking like the nose is dipping a little too much the shift the reciever /battery pack slightly rearward to get it to balance.
a slightly nose heavy plane is OK and a little foam will not add too much weight but when adding any weight to any part of a plane being foam or repair always check the balance and CG.

good advice all around,
Foam is cheap if not free. electronics and lots of things come packed in foam. some is heavy like the sheets for sale in hobby shops[:@]
Closed cell foam is nice as it won't absorb fuel. i often use the rolled stuff for putting under the sill in new house construction its 4 or 6" wide and 1/4" thick and is fuel pruff (good for exposed components such as on spads) a roll of it from your home improvement store will last you and your buddies a long time. or you can jack up your nieghbors house... well maybe not

I got a trash bag or two of thick foam blocks from a computor store, still giving that away. a block to fit in the fuse snuggly will give the same protection as used in the old drop an egg off a ladder trick we did in grade school.

auto glass comes in nice sheets af flat closed cell foam dense enough to use as leading edge material in SSC wings[8D]

large blocks are also nice on the bench to keep your plane from getting bench rash.