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Old 23 January 2018, 09:52   #1
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Ideas for drains.

Hello.

Our unit's new Valiant RIB has a couple of open drain holes on the rear transom which drain the deck when you are under power. Of course, when you stop, the boat refills.

There is a bilge pump fitted and we've temporarily plugged the two holes, but, with the deck being completely flat, we still have an annoying half-inch of water slopping around after it's turned itself off.

What's the solution?! At the moment we drain the deck fully by getting under power and then plug the two drains, but what a palaver...

Surely there's a better option?

We've looked at one-way valves (but I can't see them working reliably), hand bilges with a scoop that'll get right down to deck level etc.

Thoughts, please? (Other than 'get used to it'... )

Thanks.
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Old 23 January 2018, 10:24   #2
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Quote:
Originally Posted by Devs Ad View Post
Hello.

Our unit's new Valiant RIB has a couple of open drain holes on the rear transom which drain the deck when you are under power. Of course, when you stop, the boat refills.

There is a bilge pump fitted and we've temporarily plugged the two holes, but, with the deck being completely flat, we still have an annoying half-inch of water slopping around after it's turned itself off.

What's the solution?! At the moment we drain the deck fully by getting under power and then plug the two drains, but what a palaver...

Surely there's a better option?

We've looked at one-way valves (but I can't see them working reliably), hand bilges with a scoop that'll get right down to deck level etc.

Thoughts, please? (Other than 'get used to it'... )

Thanks.


Sounds very wrong to me. Either the deck should be above the waterline & the drain holes act as scuppers, or there should be a device to close off the holes, typically an “elephants trunk” self bailer. It sounds to me trike something’s been missed off.
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Old 23 January 2018, 10:58   #3
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+1 for Elephant trunks or risk one way valves.
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Old 23 January 2018, 12:35   #4
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what model valiant is it my v570 has no such holes or trunks just a bilge pump below deck
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Old 23 January 2018, 12:51   #5
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Rule lo pro and whale sub smart bilge pumps drain quite low. A NRV close to or out of the bilge will reduce some running back of the bilge lines.

Although I have one way valves for my deck, I found they almost pumped water in whilst idle. I stuck with them and fitted an additional NRV and a expanding bung I could remove.
https://www.force4.co.uk/force-4-exp...RoCObIQAvD_BwE
In reality an elephants trunk would have been the easiest.
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Old 23 January 2018, 13:34   #6
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As with what PD says - you shouldn't really have open holes at all. Could you post some photos of the holes? Is the boat new or used?
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Old 25 January 2018, 04:01   #7
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Many thanks, everyone, for all your replies - they have been really helpful.

I will get some photos for you asap. Yes, it's a brand new boat (well, now a season old) and has a flat deck with no recess for a bilge pump, hence the issue. At the rear there are a couple of small swept dips (ooh, 3" long, 2" wide and 1" or so deep) against the transom which lead to these two drain holes which obviously pass right through to the outside, so are under water when idle - the boat having a slightly nose-up stance.

The boat 'floods' only to a small degree - the water will be a few inches deep at the stern, but levels off (due to the boat's stance) after a foot or so. Obviously as people board and move around, this water then sloshes around very annoyingly and will wet anything left carelessly on the deck!

As soon as you take off, the water drains rapidly and it remains this way - until you once again stop...

Is it perhaps 'designed' for this so that the RIB adopts a tail-down stance for a faster take-off?

For our purposes as a safety boat, however, it's just a bludy nuisance. Our other power boat - a dory-style - has a recess to take a bilge pump, and the problem is solved. With the RIB, however, even tho' it does have a pump, there is always a goodly number of pints of sea water left behind after it's done the best job it can.

I am considering adapting the pump so that it has an intake hose rather than simply 'sucking' from under itself. This could then be set in one of the 'dips' I mentioned to draw from there?

I hadn't come across the elephant's trunk before, so thanks for that. Why do short tubes like this cost from £50 upwards?! Personally, I'd also prefer a neater solution, and once less likely to be damaged.

I'll get these photos.

Cheers.
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Old 25 January 2018, 05:57   #8
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No boat should let water in from the outside, especially a new boat, something is wrong, what model of rib, take some pics, sounds wrong. Also what size engine on transome.
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Old 25 January 2018, 07:55   #9
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It sounds to me like these drain holes are intended to have elephant trunks on one-way auto bailers fitted on/over them, but for some reason they are not present.

Photos will help.

The boat should absolutely not flood when at rest, and a stern-down attitude will slow, not help, your take off and ease of getting up on the plane, so it definitely it's a design feature.
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Old 25 January 2018, 13:13   #10
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As a Valiant Owner. I suspect that this boat has a "one way valve" with a rubber flap circa 2" in diameter. These one way valves do not work very well, as any small bit of debris will cause a problem. Also the rubber gets hard and does not seal very well (even when new).

I removed the valve and made a plug to fill the remaining hole. I then drilled it out to take a 75/76mm elephants trunk. The trunk is a better system. This work is not quite a simple as I have made it sound. If there was a slight well in the deck of the boat to take a pump it would stop a lot of sloshing of water on the deck.

Also it should be noted that the 2" hole is no good for draining the deck in a hurry even with the pump. I would class it as a dangerous design flaw on any rib. One of the main advantages of ribs is the ability to ship water quickly.

If the boat fills with water, the application of power will cause the bow to rise and the majority of the water will flow over the transom. This will still leave a considerable amount of water in the boat which will have to escape either via the pump or the hole/ valve / trunk arrangement.

Regards

TSM
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