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Old 03-09-2018, 16:53   #1
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why not standpipes?

i understand it would be difficult to retrofit in most boats, but is there a reason builders dont use an FRP tube glassed to the hull and directed up above the waterline and then attach the sea cock and flex plumbing? so all your thru-hulls are essentially above the waterline inside the boat. maybe the inside of the tube would collect too much marine growth and plug up? if thats the reason it seems anti foul inside the tube would serve, and regular bottlebrushing.

ive seen standpipes in steel construction but not FRP, curious why that is. ive got three to relocate on my project and can place them right next to a floor/bulkhead for proper support. having trouble seeing a down side, but a ton of peace-of-mind on the upside...

thoughts?
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Old 03-09-2018, 17:07   #2
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Re: why not standpipes?

When the sailboat heels over, odds are the standpipe would be below the water line. Plus the Syphon effect. Yes you could put a vacuum breaker at the top, but then you risk starving cooling water to the engine. That would get spendy quickly.
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Old 03-09-2018, 17:20   #3
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Re: why not standpipes?

There are a lot of reasons they are not common, but they are sometimes used. On our Amel the cockpit drains are FRP standpipes straight down to the hull. Very strongly glassed to the cockpit floor and the hull. Safe, efficient, and they add to the structural rigidity of an already very stiff hull.

Some reasons they are not used...

To be useful they would have to be above the waterline at all angles of heel. That is very hard in a monohull sailboat.

The standpipe needs to be VERY strong, without a seacock on the bottom, any failure would sink the boat.

When boats are sailing fast, they entrain a lot of air under the hull. That would tend to fill those standpipes with a large volume of air and then need to be cleared by whatever pump was being used.

Many pumps are not self priming, and need the head of seawater to initiate flow.

They are expensive to engineer properly and they take up lots of room in the interior.

Many thruhulls are used as drains, and need a straightline gravity drop.
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Old 03-09-2018, 17:20   #4
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Re: why not standpipes?

sorry, need to clarify. these are not for the engine (im electric) just salt water taps to head/sink and discharge. got to have a siphon break either way so thats a non issue i think. underway(sailing) SOP is all seacocks closed unless actively flushing. mostly im just picturing the elimination of below the waterline leaks/catastrophes when the boat is unattended for long periods. had a buddy sink his boat at the dock when a bronze seacock dissolved in a hot marina here in san diego. wouldnt have happened with standpipes...
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Old 03-09-2018, 17:28   #5
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Re: why not standpipes?

Quote:
Originally Posted by robwilk37 View Post
.......maybe the inside of the tube would collect too much marine growth and plug up? if thats the reason it seems anti foul inside the tube would serve, and regular bottlebrushing.............
I have a stand pipe and it does not have a problem with marine growth. I assume this is due to a lack of sunlight.

Inside of pipe is coated with plain epoxy primer.

Steve
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Old 03-09-2018, 17:33   #6
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Re: why not standpipes?

Quote:
Originally Posted by billknny View Post
There are a lot of reasons they are not common, but they are sometimes used. On our Amel the cockpit drains are FRP standpipes straight down to the hull. Very strongly glassed to the cockpit floor and the hull. Safe, efficient, and they add to the structural rigidity of an already very stiff hull.

Some reasons they are not used...

To be useful they would have to be above the waterline at all angles of heel. That is very hard in a monohull sailboat.

The standpipe needs to be VERY strong, without a seacock on the bottom, any failure would sink the boat.



When boats are sailing fast, they entrain a lot of air under the hull. That would tend to fill those standpipes with a large volume of air and then need to be cleared by whatever pump was being used.

Many pumps are not self priming, and need the head of seawater to initiate flow.

They are expensive to engineer properly and they take up lots of room in the interior.

Many thruhulls are used as drains, and need a straightline gravity drop.
id still have a seacock at the top, so they dont have to be always above water when healed. but i have the option at this point to put them nearly on the centerline so they would be above HWL. strong is a given and easy to do. yes, would have to pay attention to priming - good call. dont think a 2" heavy wall FRP tube will take up too much room, no more than the flex would. and my galley sink is centerline and midships so ive got a straight shot down for the drain.

keep em coming, this is fun...


i was going to run my cockpit drains as you say but opted for an above the waterline discharge. in my head it seems they would drain faster this way, no?
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Old 03-09-2018, 17:39   #7
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Re: why not standpipes?

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I have a stand pipe and it does not have a problem with marine growth. I assume this is due to a lack of sunlight.

Inside of pipe is coated with plain epoxy primer.

Steve
good to know, thanks so much!
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Old 04-09-2018, 00:59   #8
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Re: why not standpipes?

I had a steel boat with the toilet overboard done that way in SS pipe, never plugged or caused a problem in 25 years.

I was going to refit the galley sinks with ball valves directly under the sink bottoms and extensions for the handles, no need for plugs which often seemed to get lost and I could keep them closed to prevent smell but did not get around to it.
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Old 24-03-2019, 07:52   #9
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Re: why not standpipes?

Quote:
Originally Posted by billknny View Post
There are a lot of reasons they are not common, but they are sometimes used. On our Amel the cockpit drains are FRP standpipes straight down to the hull. Very strongly glassed to the cockpit floor and the hull. Safe, efficient, and they add to the structural rigidity of an already very stiff hull.

Some reasons they are not used...

To be useful they would have to be above the waterline at all angles of heel. That is very hard in a monohull sailboat.

The standpipe needs to be VERY strong, without a seacock on the bottom, any failure would sink the boat.

When boats are sailing fast, they entrain a lot of air under the hull. That would tend to fill those standpipes with a large volume of air and then need to be cleared by whatever pump was being used.

Many pumps are not self priming, and need the head of seawater to initiate flow.

They are expensive to engineer properly and they take up lots of room in the interior.

Many thruhulls are used as drains, and need a straightline gravity drop.

Bill, your comments noted thanks.


Q - why not have seacocks on cockpit drains or any drains?



(If your piping breaks you are able to seal the opening with the seacock.)?


Ive read something along this line before.


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Old 24-03-2019, 08:40   #10
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Re: why not standpipes?

Quote:
Originally Posted by billknny View Post
There are a lot of reasons they are not common, but they are sometimes used. On our Amel the cockpit drains are FRP standpipes straight down to the hull. Very strongly glassed to the cockpit floor and the hull. Safe, efficient, and they add to the structural rigidity of an already very stiff hull.
My little Tanzer22 has two fiberglass tubes connecting the cockpit drains to the hull below. It is all quite solid, and since buying the boat in 1981 I have not had a problem with them. But, others have had the water in the tubes freeze, crack the tube, and sink the boat.

Bill
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Old 24-03-2019, 12:35   #11
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Re: why not standpipes?

yeah - i have flexi standpipe drains from a center cockpit with big seacocks at hull level - the boats getting pretty old and its time to replace those bloody seacocks - not a quick, cheap or easy job. Thinking about a cross drain above waterline and glass over the standpipe holes in hull - shes got enough height above the waterline to do it.
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Old 24-03-2019, 14:15   #12
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Re: why not standpipes?

All through hulls on my '69 Pearson 35 were/are stand pipes except the head inlet, outlet and engine inlet. Pipes are 1 1/2" fiberglass tubing stoutly glassed to the hull with woven roving, mat and cloth. They are all less than 2' out from the centerline and have almost no problems with water ingress when heeled. None have sea cocks, just hoses to sink and cockpit drains above. A seacock would only be necessary if the tops of the standpipes went under water when boat was heeled.

Learned the hard way that the standpipes stayed above the water line. The cockpit drain hoses attached to the standpipes were extremely painful to get at with the engine in place. The hoses had been painted with white fiberglass or epoxy resin and assumed the PO had done it for cosmetic reasons. Turns out the hoses had badly deteriorated in sections and the PO had coated them with resin as a fix rather than replace them. When I pulled the engine, grabbed one of the hoses and it broke off in my hand. Lesson to learn, if PO did ANY work on the boat don't assume it was done right.
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Old 24-03-2019, 18:05   #13
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Re: why not standpipes?

I had fairly large standpipe cockpit drains in my previous boat and the biggest hazard was keeping from treading on small children who liked to lie on their stomachs and look down them to watch the bottom go by.
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