[ercoupe-tech] Re: NTSB probable cause...

[craig]

The 10% figure probably came from  design codes. Any hole no matter how small 
and the design codes say that you must at a MINIMUM deduct 10% of the 
structural strength of the metal. In any case if you drill more holes you would 
have to do the calculations to determine how much tensile strength remains.ie, 
drill enough holes and you could end up with NO tensile strength left.