This is one of those "Can you really do that?" topics.
Our foredeck hatch leaks. We can replace it with a nice Vetus or Lewmar hatch. Or, we can have just the lens replaced by Atkins and Hoyle or Select Plastics. Gerry (of The Incredible Hull) suggests replacing the entire frame. The guy we met from Select Plastics, also suggests replacing the frame because our original hatches tend to bend slightly over time.
However, rebedding the existing lens looks like it could be simple. What could go wrong?
The lens is just a big slab of acrylic or polycarbonate held into an aluminum frame with some kind of adhesive goo. Don Casey says you can simply cut the lens out with a sharp utility knife. You can easily buy or cut a replacement lens. You can easily rebed it with appropriate adhesive goo. Is there a hard part?
Cutting and Cleaning
Cutting the lens out really is easy. In our case, we were pretty sure the lens was leaking. When CA starting cutting, a huge hunk of crispy silicon pulled out from around the lens. This confirmed our theory that 80's vintage adhesive had failed and was the cause of the leak.
It turns out that the hard part is cleaning the old adhesive off the aluminum frame and acrylic lens. It was probably an all-day operation to scrape and clean and scrape and spray Xylene and scrape and wipe until there was no trace of crud or former adhesive anywhere.
We spread a healthy dose of GE Silicon II on the base and seated the lens. We let that sit for about 20 minutes. Then we filled in the edge with a heroic dose of silicon. There was goo everywhere.
It takes 24 hours to set up. However, we had to leave, so we haven't tested it yet.
Even if it's not perfect, it has to be better than the crispy — and not working — adhesive that dates from the 80's.