Another Seacock Question - replacing through hulls and ball valves with Blakes?

[Kukri]

I recently bought my first plastic boat after 42 years with wooden ones.

She came with four Blakes' seacocks and with gate valves on the engine intake and the cockpit drains, with no valves at all on the engine exhaust or the bilge pump outlet both of which are in the topsides. Two of the three gate valves have had it.

I have a dislike of ball valves, even the DZR ones and I very much prefer the Blakes' popular pattern.

I may be too picky, but the ex boat, of the same size, had been thoroughly rebuilt by me and had Blakes' seacocks on everything, above and below the waterline, on the grounds that boats may go aground, take water, heel, etc...

Questions:

1. Am I too picky?

2. If replacing a smaller bore through hull with a Blakes 38mm seacock, how does one go about enlarging the hole, in GRP (I know what I would do with wood - block off the old hole with scrap timber and rebore with a hole saw centred in the scrap wood - is this still right?

 

[cmedsailor]

1. Am I too picky?

2. If replacing a smaller bore through hull with a Blakes 38mm seacock, how does one go about enlarging the hole, in GRP (I know what I would do with wood - block off the old hole with scrap timber and rebore with a hole saw centred in the scrap wood - is this still right?

1. It's not necessarily bad neither good to be picky! It's you boat so do whatever will make you feel secure. Personally, I prefer ball valves but good quality bronze ones. In fact I am planning to replace the old brass ones with new bronze next year.

2. Just use a hole saw. It's only GRP. If you want to simply enlarge the hole why bother if it's exactly in the center (provided nothing else inside limits you)?

 

[danielefua]

I recently bought my first plastic boat after 42 years with wooden ones.

She came with four Blakes' seacocks and with gate valves on the engine intake and the cockpit drains, with no valves at all on the engine exhaust or the bilge pump outlet both of which are in the topsides. Two of the three gate valves have had it.

I have a dislike of ball valves, even the DZR ones and I very much prefer the Blakes' popular pattern.

I may be too picky, but the ex boat, of the same size, had been thoroughly rebuilt by me and had Blakes' seacocks on everything, above and below the waterline, on the grounds that boats may go aground, take water, heel, etc...

Questions:

1. Am I too picky?

2. If replacing a smaller bore through hull with a Blakes 38mm seacock, how does one go about enlarging the hole, in GRP (I know what I would do with wood - block off the old hole with scrap timber and rebore with a hole saw centred in the scrap wood - is this still right?

I cannot but endorse all what you write and I am glad to be as picky as you but, unfortunately, the new Blakes are indeed DZR. I had to change one of my 1" Blake (not produced any more) in my GRP boat and I faced your same problem. First: install a new which is not genuine marine grade bronze but DZR; is it as good? I hope so! Second: re-bore a larger hole and third: decide whether to use the external flange since the original seacock did not have one. Regarding the second point I just used a cheap portable drill press and everything worked out fine. Regarding the third point I did use the external counterflange. The only thing I really would not repeat is the latter: a good over-glassing job will suffice.
Consider that the new Blakes are, yes, DZR but have a handy grease nipple: is this a fair booby prize?

Daniel

 

[Plum]

I recently bought my first plastic boat after 42 years with wooden ones.

She came with four Blakes' seacocks and with gate valves on the engine intake and the cockpit drains, with no valves at all on the engine exhaust or the bilge pump outlet both of which are in the topsides. Two of the three gate valves have had it.

I have a dislike of ball valves, even the DZR ones and I very much prefer the Blakes' popular pattern.

I may be too picky, but the ex boat, of the same size, had been thoroughly rebuilt by me and had Blakes' seacocks on everything, above and below the waterline, on the grounds that boats may go aground, take water, heel, etc...

Questions:

1. Am I too picky?

2. If replacing a smaller bore through hull with a Blakes 38mm seacock, how does one go about enlarging the hole, in GRP (I know what I would do with wood - block off the old hole with scrap timber and rebore with a hole saw centred in the scrap wood - is this still right?

Enlarge the hole in the grp the same way as you would with wood. I understand the current Blakes seacocks are mode from dzr brass so the choice between them and ball valves is all down to your personal preferance. Personally, i do not fit seacocks to skin fittings that are more than 200mm above the waterljne.

Www.solocoastalsailing.co.uk

 

[vyv_cox]

There has been a thread recently in which the manufacturers of Blakes seacocks participated. Their oldest drawings are dated 1991 and show the material then to be DZR. My own investigations, based only on other people's recollections, suggest that DZR was probably introduced in about 1984. It may be that some were produced in 60/40 brass for about three years prior to this but this is unconfirmed. Before these dates they were bronze.

Enlarging holes in GRP is very simple. As others have said, using a hole saw with a dummy centre of wood is perfectly OK and is a technique that also works well for seized skin fittings. For modest increases in bore a flap sander works well but it is preferable that the dust falls out of the boat.

My opinion is that ball valves are perfectly acceptable for cockpit drains and exhaust, if you choose to have any valve at all. Bronze ball valves from ASAP have brass balls, which is not recommended. However, their DZR equivalents have DZR balls and should last for very many years. You will get all three for the price of one Blakes. http://www.asap-supplies.com/dzr-valve-female-each-end-405707?nosto=nosto-page-search1

 

[NormanS]

I suppose it depends on the design of your pipework, but provided your exhaust and bilge pump outlets are installed with adequate swan necks, why would you need, or want, seacocks for them?

 

[Kukri]

I suppose it depends on the design of your pipework, but provided your exhaust and bilge pump outlets are installed with adequate swan necks, why would you need, or want, seacocks for them?

Very fair question, but strange things happen at sea, and if the big ship Classification Societies want them on big ships, I want them on my little one! To offer a couple of examples, both of which have happened to me..

- a glorious long fast run with lots of surfing down the backs of waves... during which time the sustained pressure on the exhaust overcame the swan neck and flooded the engine..

- more prosaically, a grounding or three, when typically the heel adopted by the boat exceeds anything that she will ever do when sailing, and the incoming tide gets to all sorts of places before she lifts...

 

[NormanS]

Very fair question, but strange things happen at sea, and if the big ship Classification Societies want them on big ships, I want them on my little one! To offer a couple of examples, both of which have happened to me..

- a glorious long fast run with lots of surfing down the backs of waves... during which time the sustained pressure on the exhaust overcame the swan neck and flooded the engine..

- more prosaically, a grounding or three, when typically the heel adopted by the boat exceeds anything that she will ever do when sailing, and the incoming tide gets to all sorts of places before she lifts...

Fair enough, but as I say it depends on the design of your pipework.
Many years ago I had a home built Folkboat, and although I put a swan neck on the exhaust, I could visualise circumstances where it could be overwhelmed. She had a hand started engine, so the starting handle was stowed hooked onto the exhaust seacock, so that I wouldn't forget to open it.

With the boat I have now, the exhaust swan neck is adequate, and the electric bilge pump outlet has a non-return valve in the line (as well as a swan neck). The manual pump has valves.

No criticism of your belt and braces approach, but I would need to have some built-in reminders to open valves as required.

 

[pvb]

If modern-day Blakes seacocks (oxymoron?) are only DZR, you might equally go with the Maestrini DZR ball valves which Vyv suggested. Or you could go the whole hog and fit Perko bronze ball valves which have plastic balls - http://www.asap-supplies.com/fittin...pares/seacock-valves/perko-seacock-0835005plb

 

[Tranona]

- a glorious long fast run with lots of surfing down the backs of waves... during which time the sustained pressure on the exhaust overcame the swan neck and flooded the engine..

Fitting a water trap lower than the engine exhaust outlet as is now almost universal practice in addition to a swan neck virtually eliminates that scenario. Suggest you read the material on the Vetus website on designing exhaust systems.

 

[VicS]

. Suggest you read the material on the Vetus website on designing exhaust systems.

Or in the catalogue at http://viewer.zmags.com/publication/39b85263#/39b85263/80 and the following pages ( esp p. 84)

 

[pyrojames]

I have used DZR ball valves for everything now. I used to use bronze, but it was much cheaper in Oz, so the increased price wasn't a factor. I have always been unsure about the new (post 1980) blakes valves. I don't like the fact the valve is secured by 4 bolts, which even with small levels of corrosion, given the large surface area to volume, can result in significant loss of strength relatively quickly. I much prefer a solid piece of pipe with a flange on the outside, that can not fall out if small bolts fail.

 

[doug748]

I have a gate valve on the exhaust which in my view is an accident in the making. Not only can it be operated and forgotten but they are known for closing and never opening again, a bit like my local boozer.
The last owner started the motor and promptly blew the head gaskets. Ball valves are a bit quick and too easy to operate inadvertantly for this critical job.
For your ocean crossings you may be able to reach to bung a child's foam ball in there. The engine will eject it if you forget. The same sort of all fresco thing could bung up your pump outlet as required.

 

[Kukri]

Fair enough, but as I say it depends on the design of your pipework.
Many years ago I had a home built Folkboat, and although I put a swan neck on the exhaust, I could visualise circumstances where it could be overwhelmed. She had a hand started engine, so the starting handle was stowed hooked onto the exhaust seacock, so that I wouldn't forget to open it.

With the boat I have now, the exhaust swan neck is adequate, and the electric bilge pump outlet has a non-return valve in the line (as well as a swan neck). The manual pump has valves.

No criticism of your belt and braces approach, but I would need to have some built-in reminders to open valves as required.

I used to hang the starter key on the seacock. Same idea.

 

[Kukri]

I have used DZR ball valves for everything now. I used to use bronze, but it was much cheaper in Oz, so the increased price wasn't a factor. I have always been unsure about the new (post 1980) blakes valves. I don't like the fact the valve is secured by 4 bolts, which even with small levels of corrosion, given the large surface area to volume, can result in significant loss of strength relatively quickly. I much prefer a solid piece of pipe with a flange on the outside, that can not fall out if small bolts fail.

I see things a little differently.

A DZR seacock secured by silicon bronze bolts should be safe, because the large casting is slightly anodic to the bolts.

The turned shoulder on a skin fitting on the other hand is a stress raiser and therefore it is a natural spot for corrosion to start.

 

[reeac]

My Sadler has Blakes seacocks for the heads (toilet and washbasin). I religiously (I.e. On my knees) dismantle, clean and grease them annually. The engine cooling water and galley sink have ball valves - the latter having replaced a gate valve the hand wheel of which collapsed through rust. The ball valves have never seized or leaked and were never serviced in any way. I can't decide which I prefer, the undoubtedly durable but needy seacocks or the undemanding ball valves.

 

[vyv_cox]

My Sadler has Blakes seacocks for the heads (toilet and washbasin). I religiously (I.e. On my knees) dismantle, clean and grease them annually. The engine cooling water and galley sink have ball valves - the latter having replaced a gate valve the hand wheel of which collapsed through rust. The ball valves have never seized or leaked and were never serviced in any way. I can't decide which I prefer, the undoubtedly durable but needy seacocks or the undemanding ball valves.

Exactly the same as mine, other than the gate valve, which I have never had. Last year I found that the ball in the original engine coolant seacock had seized in the half open position and the stem had sheared. Every time I turned the handle, thinking I was closing the valve, nothing was happening.

 

[ghostlymoron]

Exactly the same as mine, other than the gate valve, which I have never had. Last year I found that the ball in the original engine coolant seacock had seized in the half open position and the stem had sheared. Every time I turned the handle, thinking I was closing the valve, nothing was happening.

Had exactly the same happen on my cockpit drains. I replaced them with stainless ones which I got for free.

 

[danielefua]

I see things a little differently.

A DZR seacock secured by silicon bronze bolts should be safe, because the large casting is slightly anodic to the bolts.

The turned shoulder on a skin fitting on the other hand is a stress raiser and therefore it is a natural spot for corrosion to start.

As mentioned before I do not think that the external flange with through bolts is necessary. If a Blake seacock is well fixed with its internal flange glassed over with several fairly wide GRP mat/cloth layers possibly with epoxy resin, it will resist the famous test of standing on it with one's weight; the job must be well done, of course. My boat had all the seacocks fixed this way at build time and, if anyone has doubts, it suffices saying that she was certified by the Lloyd's Register.

Daniel

 

[Kukri]

I had ball valves on the cockpit drains but these soon became stiff and eventually froze; I suspected that the nylon (?) seats were swelling very slightly. Replaced with Blakes. That experience diminished my enthusiasm for ball valves.