Well, I dropped my MK V dive helmet on the concrete patio while sanding it, and broke it. This opened up a lengthy crack over the top of the helmet. After taping up the outside of the crack with painter’s tape, I added fiberglass to the inside of the helmet. Next, I’ll add more body filler to the crack on the outside of the helmet.
Man in the Sea Museum
Today I visited the Man in the Sea Museum, a really cool museum of diving history. It’s located in Panama City Beach, Florida USA. Some of the equipment on display was familiar because I had helped write Navy documentation for the equipment, while working for defense contractors in the late 1980s. The museum entry fee was reasonable (I think it was US$5) and they gave a free huge poster about the history of diving.
US Navy Mk 14 
US Navy Mk 12 Helmet 
The museum people were all very cool, and friendly. They almost encouraged you to handle the helmets/suits and other items on display. And they were very nice to allow me to bring in a ruler and sketchbook to make some more detailed measurements and examination of particular items on the Mk V.
MK V Dive Helmet – refining the bottom rim
Once the cardboard base was pulled away, the rim around the bottom needed some reinforcement and shaping. I’m using a hobby wire mesh to define the edge, and then some more body filler to cover that. I cut the mesh with regular household scissors, then folded it over the bottom edge.
MK V Dive Helmet – first coating
After the plaster dries, it’s time to put on a first coat of plastic automotive body filler. I used the common 3M product, Bondo:
MK V Dive Helmet – basic shape
So this is the starting point for the helmet. A plastic inflatable ball with a cardboard base:
Now to coat it. I’m going to use plaster-coated cloth strips that I got from the hobby store.
I took the roll of plaster cloth and cut it into strips about 2-3 inches (50-75mm) wide. The gauze/cloth strips are just dipped into warm water. The excess water is squeegeed off with your fingers, and the strip is draped over the ball and cardboard
I made a real mistake by using a few cardboard strips for the “ribs.” This left a sunken area in between the ribs, and I stuck in a few cardboard strips to try and fill it in. I think it would be much better to use more ribs or, better yet, generate a conic section that fits the shape when rolled up, and cut it out of cardboard or similar material.