Plastic deck hatches- are they actually watertight?

[Kelpie]

I'm considering fitting something like this:
Force 4 Inspection Hatch with Lock | Force 4 Chandlery
to a dinghy that I'm building.
Normally you would use a small round screw-in hatch, but that gives very limited access to the space. A bigger opening will make it easier to build and also make a much more useful storage space.
My only worry about this kind of hatch is that I don't know how much I can trust it. Is it going to be suitable for sealing a buoyancy compartment?

 

[Tranona]

They are commonly used in loo and shower compartments - I have one for the access hatch to the engine which is in the shower part of the loo compartment. Not sure I would rely on one for an air and water tight seal for a buoyancy chamber.

 

[geem]

I'm considering fitting something like this:
Force 4 Inspection Hatch with Lock | Force 4 Chandlery
to a dinghy that I'm building.
Normally you would use a small round screw-in hatch, but that gives very limited access to the space. A bigger opening will make it easier to build and also make a much more useful storage space.
My only worry about this kind of hatch is that I don't know how much I can trust it. Is it going to be suitable for sealing a buoyancy compartment?

In our nesting dinghy we have two compartments. The rear compartment is a full buoyancy compartment with a small water tight inspection hatch. Its only about a 100mm diameter aperture. Big enough to get a hand in. We don't use this compartment for storage. Its water tight. There is more than enough buoyancy in this compartment to keep the dinghy afloat.
The front compartment is used as a storage locker. Its big enough to put shopping in and anything we want to keep dry. The locker has a proper lid and is made of foam core. The design of the lid keeps the locker dry but if we were to turn the dinghy over it would likely take some water in. We dont have a lock on it as I think it would probably be broken in to. We just have a bolt on it. We dont leave anything in there that we cant afford to lose. The bulkheads in the dinghy are all foam core so also provide some natural buoyancy.

 

[Boathook]

I'm considering fitting something like this:
Force 4 Inspection Hatch with Lock | Force 4 Chandlery
to a dinghy that I'm building.
Normally you would use a small round screw-in hatch, but that gives very limited access to the space. A bigger opening will make it easier to build and also make a much more useful storage space.
My only worry about this kind of hatch is that I don't know how much I can trust it. Is it going to be suitable for sealing a buoyancy compartment?

The q&a on force 4 says water tight but I would not like to use it as part of a buoyancy compartment with only one latch holding it shut against air pressure trying to get out.

 

[wombat88]

I wouldn't trust it for a dinghy that might go over. Any warping and the corners won't seal. Stick with the round ones and maybe use two, well spaced.

 

[Jonny A]

I have something similar, a round one for the gas locker on my Contessa. It leaks continuously and drives me mad. I've tried replacing the seal and keeping everything spotless and free from dirt but it still leaks like a sieve. If anyone has any suggestions I'd welcome them greatly.

 

[Kelpie]

That's a pretty unanimous response, thank you, and not entirely surprising!
I think the largest hatch I could fit that would be reliable enough would be around 6", unless anybody is aware of anything larger?

 

[prv]

I’ve got one that’s the same design as the common screw-in 4” type, but quite a bit bigger:


Its waterproofing is not severely tested in that location, but it certainly shows no sign of leakage and the fit and seal are convincing.

Pete

 

[neil_s]

I have a similar rectangular hatch on my gas bottle locker. It was fine at first, but I have noticed that the lid has warped slightly over several years and I don't think it seals properly, now.