Sometime ago, someone brought up the problem of how to paint the fuel tank openings on a L-IV.    In the past when I primed my wings, I  used masking tape and guessed about where the  tape should go;  however, my results were pretty poor and not consistant.

Recently, I had a machinist friend  look at the problem and he came up with a solution that seems to work pretty well.  He machined a dummy fuel cap (aluminum plug) that mates with the exact surface where the regular fuel cap seals.  I  lined the opening with a piece of vinyl tape and placed the plug into the opening.  Then with an exacto knife, I trimed the tape  where it  appeared above the plug.  BINGO,  I now had a perfect circle inside the fuel tank opening that shouldnt be painted.  Then it was pretty easy to add masking tape below the  edge of the vinyl tape to cover the opening and when the wing was painted, I ended up with a nice looking result.

If any brave soul wants to give my plug a try,  you can contact me directly at :
billhogarty@hughes.net

PS  I DO NOT recommend painting your own plane.  Its a forever job best left to the professionals.  : - (