Help! Seams won't go away!

For really stubborn, wide seams, I'll run a couple of strips of tape down both sides of the seam, then lay the putty in the trough, leveling it with a putty knife or piece of plastic card stock.  Pull the tape, let it set, then hit it with a sand paper board.  It seems to do a better job of hiding the seam, and not making a big mess down the side of the seam.  

Gene Beaird,

Pearland, Texas

Gamera

BTW make sure the seam is actually cemented together. I've puttied and sanded seams a dozen times and they would not go away. Found out later that the seam wasn't glued and when I'd put pressure on it with the sanding stick it would 'pop' and I'd end up with a crack again. Worst situation was on a 1/72nd B-29 - the long seams on the top and bottom of the fuselage kept popping loose over and over- took me a while to figure out this was what was happening.  

Yes!  This is the big problem with the original post. If the orignal glue joint is not good enough, no amount of filling will be satisfactory.  The glue joint MUST hold.  Then you can worry about fillng the remaining seam.

Often times I find that the putty didn't really fill the seam so much as bridge it. So, as I'm sanding it later, the gap under the putty is revealed. In this case, it may appear that the seam is reoccurring but in reality I'm just sanding the void open. That's where practice, practice, practice comes in. Gotta make sure your putty is filling, not only spanning, the joint.

And, as others said, glue strips of thin styrene into wider gaps before puttying.  

Question on this: after you apply `whatever`method, how do you deal with covering up raised details like rivets and raised panel lines. This is a continual frustration for me...sanding away detail to get rid of the seam!!

The seams that give me the most trouble  are the ones where one side is higher than the other. You cannot just sand the high side down to match the low side without creating other problems. These have to be feathered with putty which I have to keep at over and over.