To protect the hatch seals on US Navy subs, they have a plastic-dipped aluminum ring with a lip that is placed over the hatch ring. The ring is hinged so it folds in half and can be easily stowed inside the sub when getting underway. R/Jay Resepectfully, Jay K. Jeffries Andros Is., Bahamas Save the whales, collect the whole set. From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Hugh Fulton Glen, Tried and true. Follow the plans. Everything is there for a reason. You will never wear it out from opening and closing the hatch and diving. You may damage it from dirt or UV or just ageing. The Captain put it in to retain the ring, so you stretch the o’ring slightly over the dovetail. A bit of grease also helps to retain O’rings, however it also attracts dirt. I have studied his plans and his genius is in his simplicity. ( I always complicate things). IT can be argued that you can use a slightly oversize ring with an external dovetail but if you get it wrong you squash it in here and it pops out somewhere else. Phil Nuytten has a very nice little addition which is a plastic cap to cover the hatch face for when the hatch is open to stop damage from people climbing in or when it is being serviced. Chs Hugh |