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Old 11-29-2009
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old seacock inspection

We have an old cal 33. The seacocks are the right kind but I am not sure the installtion is correct, There is a wood base then a washer and nut holding the outside to to the inside. the threaded part is showing about 1 1/2 inches then there is another nut and then the base of the seacock . Is normal on a boat from the 70's and can the seacocks be left this way?
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Old 11-29-2009
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We have a Nicholson 39 from 1976 and all our sea cocks are the same. When we remove them for servicing/repair we change the wood base for a plastic base [cut from an old breadboard approx 1cm thick] instead.
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Old 12-01-2009
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Quote:
When we remove them for servicing/repair we change the wood base for a plastic base [cut from an old breadboard approx 1cm thick] instead.
Richard; In your opinion do you think an installation where one inch of thread showing between the nut, holding down the wood/plastic base and the base of the seacock itself, is a proper installation?

How often do you replace your seacocks?

Any info is appreciated.
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Old 12-01-2009
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It would not meet current standards in which the seacock is through bolted to the hull and there supposed to be able to support weight X in a worse case issue.

In the US it could be a survey/insurance issue when a boat changed owners Or the insurance company wanted some things bought up to current standard
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Old 12-01-2009
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Detail on seacocks

Just to confirm the detail: Our seacocks are all through hull mounted with phosphor bronze bolts. They are Blakes standard bolts. The 'washer' made of plastic goes between the hull [which is very thick being an old Nicholson - 3cm on the sides or 4cm lower down in thickness] You could probably tow the boat from the seacocks, so I'm sure that they would meet US standards. As far as I know there are no requirements for strength testing in the EU.

We only acquired the boat approx 6 weeks ago and its our first boat. We are not replacing the seacocks as a matter of course but inspecting each one in turn. The reason for taking one off was that it had stuck solid and the only way to unstick was to remove from the hull and then use a rod up the centre to unlodge the centre turning part of the seacock. Seeing the condition of the wood washer [marine ply] we have thought about replacing all the washers, but will not do so this season, since there are more serious issues to work on.

It's critical that the seacocks are through hull bolted, since the very last thing you want is a seacock separating from the hull at sea. The new one we have just fitted we are epoxy sealing where we have cut through the fibreglass so that there can be no water penetration into the fibreglass layers.

What the washer does is allow you to shape it slightly to match the shape of the hull, which is not flat, allowing the seacock to be bolted solid to the hull. You can remove part of the plastic washer with a sureform plane to match the inside shape of the hull before using Sikaflex [never ever use silocon below water line it will leak as I found out on the Wayfarer I had before the Nicholson].

We are keeping a log of maintenance on the sea cocks. Most have slight corrosion on the back of the inner piece, slight pitting that is. Looking at the Blakes site they mention this can be due to lack of anode. We have an anode but the previous owner decided in his infinite wisdom to disconnect this from the boat earth. I will replace that connection before we return the boat to the water in a few weeks!

Last edited by RichardKM; 12-01-2009 at 11:34 AM.
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Old 12-01-2009
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Quote:
Originally Posted by RichardKM View Post
We have a Nicholson 39 from 1976 and all our sea cocks are the same. When we remove them for servicing/repair we change the wood base for a plastic base [cut from an old breadboard approx 1cm thick] instead.

Richard,

Do your self a favor and use real fiberglass backing blocks. They are easy to laminate. Plastic cutting board, Starboard and many of the plastics in this family do not like anything to stick to them and they do not stick well to sealants. They also have different expansion and contraction coefficients which when attempting to bond something to them will eventually cause a leak.

Those Blake's sea cocks will last a LONG time if properly maintained. They can be re-lapped, cleaned and lubed and put back into service provided there is no serious corrosion or dezincification.

As to the OP's question many boats have seacocks like this. They should be able to withstand a static load of 500 pounds at the innner most point of the hard fittings. Usually this is the tip of the hose barb where the 500 pounds is applied. More thread showing means more lever at the inner most hard fitting.

Proper flanged seacocks, even wihout through bolts, are a safer installation but many boats are still floating with the "valve on a thru-hull" type installation.
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Quote:
Originally Posted by Maine Sail View Post
Do your self a favor and use real fiberglass backing blocks. They are easy to laminate. Plastic cutting board, Starboard and many of the plastics in this family do not like anything to stick to them and they do not stick well to sealants. They also have different expansion and contraction coefficients which when attempting to bond something to them will eventually cause a leak.
OK, makes sense. Did you laminate them yourself? Do you then cut them and seal the edges with epoxy?

Our comparison was with the existing marine ply washers. The plastic cutting board is a plain plastic one found in europe not like the disinfectant impregnated ones in the USA. Sikaflax appears to stick very well to the plastic.

Quote:
Originally Posted by Maine Sail View Post
Those Blake's sea cocks will last a LONG time if properly maintained. They can be re-lapped, cleaned and lubed and put back into service provided there is no serious corrosion or dezincification.
Ours are over 30 years old and the pitting I am fairly sure is due to the lack of connected anode. They do seem very well made. The new ones have a grease nipple. Is this a really useful addition or just an added extra?

Quote:
Originally Posted by Maine Sail View Post
As to the OP's question many boats have seacocks like this. They should be able to withstand a static load of 500 pounds at the innner most point of the hard fittings. Usually this is the tip of the hose barb where the 500 pounds is applied. More thread showing means more lever at the inner most hard fitting.

Proper flanged seacocks, even wihout through bolts, are a safer installation but many boats are still floating with the "valve on a thru-hull" type installation.
How is this tested? A pull of 225 Kg is a heck of a pull! Does this also apply to other through hull fittings [eg plastic threaded log/speed instruments]? I would be very surprised if the log we have just fitted took even 100 Kg.
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Richard,

Personally I don't like a grease zerk on a tapered cone seacock. This helps people put off and avoid the inevitable yearly or bi-yearly cleaning, inspection and lube which should be done on a tapered cone design. If lubed and cleaned yearly they can last nearly forever. If you ignore them by blasting more grease in there you may miss an issue for a while and then it may be to late.


The 500 pound static load is a requirement of ABYC for seacock installations though the testing has already been done. Many "valve on a thru-hull" installations will not survive this test but any UL Marine listed flanged seacock has been through this test and passed. Marelon flanged seacocks pass, Groco, Apollo, Spartan and Blake's too. If you decide to make up your own combination of the thru-hull and a valve the combination has not likely been tested to this level of certification.


As for the backing blocks feel free to take a look at these links.

Seacock & Thru-Hull Primer/Pre Information


Replacing Thru-Hulls and Seacocks



Seacock Backing Plates / Alternate Method / No Through Bolts
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Last edited by Maine Sail; 12-01-2009 at 03:39 PM.
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Thanks Maine Sail for the photo links. They are really excellent.

One thing with the Blakes which are different from the illustration is that the shaft of the sea **** is not fitted to the outside hull fitting. Hence why when we have fitted the outside hull fitting we are going to epoxy edges the hole we cut in the hull to stop water penetration into the laminates.

The thinnest our hull is 3cm [we counted 9 laminate layers] so might well be OK to use without a washer at all. We had assumed the wood washer was to allow the surface to be made flat against the hull... with a GRP washer you would have to grind away glass fibre to be able to match it with the hull before glassing in place. That would be a pretty messy process!

Thanks for the tips.

Richard
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with a GRP washer you would have to grind away glass fibre to be able to match it with the hull before glassing in place. That would be a pretty messy process!

Thanks for the tips.

Richard
No actually you use a thickened epoxy or thickened fiberglass resin to peanut butter consistency. I thicken with CSM, Cabosil/Aerosil & milled fibers. Just a strong recipe that I like.

You then then slather the backing block in the peanut butter, and coat the hull too, and then bolt the, WAXED, seacock in place using the WAXED bolts to align it before the peanut butter begins to kick. Once the bolts are tight and everything is aligned make a nice fillet with your gloved finger going around the block with the peanut butter that squeezed out.


I use a slow epoxy hardner if the "gap" between the hull and backer block is not too thick. I don't want to much exothermic heat. If the hull is has to much curve I take some off the edges of he backing block, not the hull, then do the procedure outlined above.

When using fiberglass backing blocks I only use epoxy or polyester or vinylester to adhere the backer to the hull not Sikaflex of 3M.

If your design does not use a thru-hull a solid glass laminate is even more important than a plastic with Sikaflex. Morris Yachts does this same type of installation, through solid glass, but, with Marlon sea cocks and no thru-hull. They simply seal the exposed hole fibers with barrier coat or epoxy. It makes for a nice smooth hull but does leave you entirely dependent upon the bolts because you no longer have a thru-hull..



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Last edited by Maine Sail; 12-01-2009 at 03:55 PM.
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