Saturday, April 16, 2011

Drilling a BIG Hole in a Perfectly Good Boat

Today was Hail Mary day, and now my boat has a 6" hole in the hull. But before that....

There is a 16" diameter backing plate that mounts on the outside of the hull and is through-bolted through the inside mounting plate and actuator assembly, sandwiching the hull in between. Everything gets gooped up with 3M 5200 before final assembly. All this means that the anti fowling paint has to be removed where the outside plate will attach so the 5200 seals directly against the hull. The first pictures show the areas cleared of paint. I'll touch it up by hand before final assembly.

We also ran into a little problem. My glass guy was using the backing plate to be sure he maintained clearance between the stringers while building up the glass. It's a tight fit, and adding glass up the sides of the stringers could push it over the edge. Well, he didn't realize that the outside plate is about an inch smaller in diameter than the inside plate.

Darn. So he's had to do some grinding on the finished side, and has established a keep-out zone on the side still being glassed. The good news is that the inside plate now fits on the starboard side, which means it's time for drilling.

A 6" hole saw and a powerful right angle drill are a hazardous combination. Fortunately I've been beaten up by them before and know to proceed slowly and with caution. The pictures show my hull being threatened by the drill, then the final results.

Next you can see the inside mounting plate visible through the hole, and two screws that get placed to locate the plate in the hole. The screw heads just barely catch the edge of the plate, so I picked up some larger screws on my way home today and will also relocate the holes so they firmly catch the plate edge .

The last picture shows the mounting plate from inside the hull. You can see three black bolts running through the plate. These are jack bolts used to precisely level the plate so it's exactly parallel to the hull's outside surface. ABT provides a very useful alignment tool to confirm the plates position, and I'll post picture later when I really put it to use. All I did today was make sure the plate position was in the right ball park, and it is.

Stay tuned......
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