Ideas for drains.

Devs Ad · 23 January 2018, 14:52

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.

Pikey Dave · 23 January 2018, 15:24

Quote:

Originally Posted by Devs Ad

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.

charliee · 23 January 2018, 15:58

+1 for Elephant trunks or risk one way valves.

beerbelly · 23 January 2018, 17:35

what model valiant is it my v570 has no such holes or trunks just a bilge pump below deck

gtflash · 23 January 2018, 17:51

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.

Andy_Rs600 · 23 January 2018, 18:34

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?

Devs Ad · 25 January 2018, 09:01

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.

boristhebold · 25 January 2018, 10:57

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.

Andy_Rs600 · 25 January 2018, 12:55

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.

two stroke mick · 25 January 2018, 18:13

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

Devs Ad · 28 January 2018, 14:42

Hi all.

I've managed to get some photos.

It's a Valiant 470 Sport.

The photos show the holes on the outside of the transom, a close-up of the same, an inboard view and a close-up of the small well that leads to the outlet.

I think it's pretty clear it was designed this way, and I should point out that the boat doesn't 'flood' with these two plugs open, but it does take on a few inches of water towards the stern - which then drains away quite quickly under power. Hence me assuming it's designed to keep the stern low at rest for a quick take-off?

There is an access hole for the hull (photo 3), and I don't know if there's any mileage in converting that somehow in to a recess where a bilge pump could sit? If I can get hold of a spare access cover for not too much, I'd certainly experiment with this.

Looks like elephant trunks are the best self-draining option.

Many thanks for all you thoughts and comments.

Xk59D · 28 January 2018, 14:48

Never seen anything like that on a rib but I guess it used to be a one way bailer, I would swap it out.

Edit....this is the job- http://www.rib-shop.com/drain-sock-kit/

Poly · 28 January 2018, 15:18

Any of the one way bailers will struggle with rubbish, leaves etc you seem to be accumulating there, so I’d say your choices are: 1. cut a big hole and fit a trunk - how easy that is will depend on your skills and what the transom/hull is like in that area.
2. Fit an expanding bung in the hole. If you don’t ship water often this will serve your needs - you will normally use the boat closed off but if you stuff it or are taking on lots of spray and keeping on the plane you remove the bung. (This is my arrangement and I use the bilge pump for routine spray).
3. Possibly add a small dam around the top of the recess to stop the water flooding back. Perhaps you could engineer that so it is removable/collapsible in a hurry.
4. Buy some wellies.

Andy_Rs600 · 28 January 2018, 20:12

I've never seen anything like that either. As has been said you need some trunks on a bigger hole, or some small one way bailers, or just some bungs. If your not comfortable drilling/cutting a big hole for the trunks I'd just put a hung in and leave the pump to clear water.

Just to clarify again, no amount of water in the boat will make your take-off any quicker, only slower. More stern down just makes you slower to accelerate. I can't imagine any rib builder designed the boat to ship water (even a little bit) by design. I think these used to have a one way valve on that has somehow gone missing...

Dave Cowell · 29 January 2018, 09:42

It looks as if the one way valve/rubber flap is missing, possibly knocked out when someone was poking at it to remove a blockage
Drain Socket and Diaphragm 42mm
shows the parts

Wightdiver · 29 January 2018, 15:13

Quote:

Originally Posted by Poly

Any of the one way bailers will struggle with rubbish, leaves etc you seem to be accumulating there, so I’d say your choices are: 1. cut a big hole and fit a trunk - how easy that is will depend on your skills and what the transom/hull is like in that area.
2. Fit an expanding bung in the hole. If you don’t ship water often this will serve your needs - you will normally use the boat closed off but if you stuff it or are taking on lots of spray and keeping on the plane you remove the bung. (This is my arrangement and I use the bilge pump for routine spray).
3. Possibly add a small dam around the top of the recess to stop the water flooding back. Perhaps you could engineer that so it is removable/collapsible in a hurry.
4. Buy some wellies.

If you are unsure about cutting holes in your deck then try these, http://www.ronhalemarine.co.uk/super...b_DSC03214.JPG

The trunk is attached to a flange held in place by 6 screws that you could simply place over the existing holes so no need to chop the transom up.

Poly · 29 January 2018, 18:32

Do you think that would work well with a much smaller whole than the trunk is?

beerbelly · 29 January 2018, 19:54

Quote:

Originally Posted by Poly

Do you think that would work well with a much smaller whole than the trunk is?

I think his main problem is water getting in not out if the water thats getting in is being cleared by the holes he has fitting a flanged tube and trunk over it should be ok as long as he makes sure the flange to transom is sealed

Poly · 29 January 2018, 23:34

Quote:

Originally Posted by beerbelly

I think his main problem is water getting in not out if the water thats getting in is being cleared by the holes he has fitting a flanged tube and trunk over it should be ok as long as he makes sure the flange to transom is sealed

Intuitively that feels right, but I've always assumed my drain worked on a venturi type approach rather than pure gravity/inertia. Perhaps my drain is simpler than I think - but it works very quickly.

beerbelly · 30 January 2018, 07:11

Quote:

Originally Posted by Poly

Intuitively that feels right, but I've always assumed my drain worked on a venturi type approach rather than pure gravity/inertia. Perhaps my drain is simpler than I think - but it works very quickly.

Im not saying your wrong just that it would be better than he has now at least thevtrunk would stop water flowing in at rest