Backing plates

spuddog

spuddog

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Hi all,I intend to replace my seacocks,hopefully this weekend.At the moment I have gate valves on the inlet and outlet of the heads and a slightly better jobby on the engine intake.
I have bought 3x blakes seacocks ( 2x 3/4 inch + 1X 1.5 inch ) I would like to fit backing plates as there are none at the moment.
I have made up some plates from marine ply (from what I have read they are not the optimum,but the best I can do in what is becoming a tight timescale).
my question is,what is the best material to coat them with in order to waterproof/make them last a few/many years?
Cheers,John.
 
spuddog said:
Hi all,I intend to replace my seacocks,hopefully this weekend.At the moment I have gate valves on the inlet and outlet of the heads and a slightly better jobby on the engine intake.
I have bought 3x blakes seacocks ( 2x 3/4 inch + 1X 1.5 inch ) I would like to fit backing plates as there are none at the moment.
I have made up some plates from marine ply (from what I have read they are not the optimum,but the best I can do in what is becoming a tight timescale).
my question is,what is the best material to coat them with in order to waterproof/make them last a few/many years?
Cheers,John.
Click to expand...

bed in mastic & bilge paint over the bit that is exposed :confused:
others will disagree :D:D
 
If you get the time, how about stainless plates, just thin enough ( 2mm ? ) to be able to form to the hull shape, - but essential they bed flat under the seacock / s ) - in epoxy...

Most seacocks I've seen however, haven't suffered from backing as the main failing ( and backing DOES need to be above suspicion, especially with view to heavy kit moving hard against seacocks at high velocity in a gale etc, shearing off or dislodging could lead to a very bad day ) but access is the usual problem; keeping this clear and maintaining at intervals seems at least equally important.
 
Seajet said:
If you get the time, how about stainless plates, just thin enough ( 2mm ? ) to be able to form to the hull shape, - but essential they bed flat under the seacock / s ) - in epoxy...

Most seacocks I've seen however, haven't suffered from backing as the main failing ( and backing DOES need to be above suspicion, especially with view to heavy kit moving hard against seacocks at high velocity in a gale etc, shearing off or dislodging could lead to a very bad day ) but access is the usual problem; keeping this clear and maintaining at intervals seems at least equally important.
Click to expand...

So add different metal rather than plywood

attachment.gif
 
Plywood does not last long in boat bilges; as for disimilar metals, yes I should have mentioned attaching to a common anode.

An infinitely better practice which I also forgot to mention is if starting from scratch to place all the seacocks, if at all possible, in one accessible place - a manifold, where one can lift one hatch in the cabin sole to get at the lot.

All happily abstract for me as I avoided having any holes in the hull at all, from new-build.

Something to have in mind is that some lightning strikes blow seacocks, log impellers etc clean out of the hull...:) ?!
 
Seajet said:
Plywood does not last long in boat bilges; as for disimilar metals, yes I should have mentioned attaching to a common anode.

An infinitely better practice which I also forgot to mention is if starting from scratch to place all the seacocks, if at all possible, in one accessible place - a manifold, where one can lift one hatch in the cabin sole to get at the lot.

All happily abstract for me as I avoided having any holes in the hull at all, from new-build.

Something to have in mind is that some lightning strikes blow seacocks, log impellers etc clean out of the hull...:) ?!
Click to expand...

what backing plates would you recommend for use in a plywood boat :confused:
 
Good quality marine ply is perfectly adequate. Use a Polysuphide sealer between it and the hull, including the slightly oversize holes. Paint with Danboline when the sealer had cured. If done properly the seacock wont leak so no water will get near it. Do not connect to anodes. Completely unnecessary. Properly installed and serviced Blakes will last a lifetime.
 
Tranona said:
Good quality marine ply is perfectly adequate. Use a Polysuphide sealer between it and the hull, including the slightly oversize holes. Paint with Danboline when the sealer had cured. If done properly the seacock wont leak so no water will get near it. Do not connect to anodes. Completely unnecessary. Properly installed and serviced Blakes will last a lifetime.
Click to expand...
I agree - just use good quality marine ply and it will be fine.

If your wanted the gold plated solution you could make the backing plates and coat the ply in epoxy, bed them on a suitable mastic and then paint the whole thing with a couple of coats of danboline bilge paint.

If people have had problems with ply in the bilge of their boat, then it must have been rubbish plywood and not painted very well either.

With respect Seajet, there is always someone who thinks that having no holes in the bottom of their boat is somehow a good thing but the vast majority of boats in the real world have holes in their hull with seacocks on them. There's nothing wrong with a good quality seacock and there's nothing to worry about for most of us, and most boats don't sink either.

Finally, another vote for not connecting seacocks to sacrificial anodes. Its a waste of time and unecessary, and might actually do more harm than good - depending on how your boat is wired.
 
My vote would be for you to follow advice from John Morris, Why do half a job when you are fitting expensive valves intended to last a lifetime? Epoxy coated marine ply will last just as long and bilge paint will make it look nice as well as helping to keep the water out.

Yoda
 
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