I suspect he means lightening holes, which I assume are the holes cut through the neutral axis of the webs to reduce the weight of steel. Not a ship builder though.
As an individual who has spent the last 25 years in shipbuilding, I 110% concur with the statement above.
The link at the top of post #2055 (
goto image #8 of #86), shows clearly that the holes in question are large enough for personnel to transit thru (
albeit that they are a pain to transit thru !). Limber/mouse-holes are normally at the extremes of welded joints / in corners between stiffeners & bulkhead / deck head plates & are generally no bigger than x1 or x2 fingers width in size. They help provide a route for air / fluids to transit, while having the additional benefit of prevent 'sheer' tears in bulkhead panels, caused by stress loading (
when larger / longer hulls are constantly slamming & bouncing in heavy seas (above sea state 6)).
The phrase '
Lightening holes' merely refers to the fact that by removing the centre section between the stiffeners, they are maintaining the structural strength of the bulkhead but actually reducing the overall weight of the vessel. This is a common shipbuilding practice as maintaining overall weight of a ship in 'dry' configuration allows the naval architects to calculate a more accurate set of speed / range calculations. In this modern era these are often written into the contracts & can cost both the customer & shipbuilder dearly, if the ship cannot achieve a set range, at a specific speed. This is something that LCS allegedly fell foul of when the data pointed to the fact that the ships can't transit from San Diego to Hawaii at a specific (
high) speed, as they would run out of fuel before they got there...
Many Navies have to re-examine this data after every refit / addition of any new system, as additional weight over & above the initial design data will have a detrimental effect to the ability to maintain top speed.