Bilge pump for hull water? - Page 2

Mike B · 12 July 2006, 10:32

I don't know if it is feasable or recommended. But my Narwhal's hull is filled with pressure-compacted closed cell polyurethane foaming, which makes it unsinkable even if the hull is broken. (NB this wasn't retro fit it is as standard). Would it be feasible to retro fit this?

They have received certification of an unsinkable boat (whatever that is!)
http://www.narwhal.es/narwhal.php?pa...es&idnoticia=2

I once saw a demo for a dory where they chainsawed it in half and paddled away the two halves due to the inherent bouyancy - I guess this would do something similar.

Just a thought.

Mike

jgrace · 12 July 2006, 14:04

Quote:

Originally Posted by Mike B

I don't know if it is feasable or recommended. But my Narwhal's hull is filled with pressure-compacted closed cell polyurethane foaming, which makes it unsinkable even if the hull is broken. (NB this wasn't retro fit it is as standard). Would it be feasible to retro fit this?

They have received certification of an unsinkable boat (whatever that is!)
http://www.narwhal.es/narwhal.php?pa...es&idnoticia=2

I once saw a demo for a dory where they chainsawed it in half and paddled away the two halves due to the inherent bouyancy - I guess this would do something similar.

Just a thought.

Mike

It's a good thought!

It would certainly solve the problem if leaks were an ongoing irritation.

The most likely difficulty I can see is making sure that the foam gets into all the crevices of the hull void. Anyone know whether the internal structural members in a Valiant hull have holes in the neutral axis?

One other issue: Would the hull start to squeak as it flexed in a sea? I don't want a squeaky rib!

Jim

J S · 12 July 2006, 14:12

Mike B I saw this as well I think it was boston whaler

Mike B · 12 July 2006, 14:27

Quote:

Originally Posted by jgrace

One other issue: Would the hull start to squeak as it flexed in a sea? I don't want a squeaky rib!

Jim

Never thought of that! - Mine doesn't squeek but if there are voids then I suppose it is potential - I don't think your likely to hear anything above the wind / engine / water at sea - though I guess it would be possible when walking on the deck at rest.

Mike

ian parkes · 12 July 2006, 19:17

years ago we filled a load of club kayaks with that foam in each end . after a while it absorbed water and they were as heavy as hell . Not sure if there is some better stuff about now but the foam in a can you get in the builders merchant has the same problems .

I filled the inside of my boat with about 4 inches of water tis morning. It only filled the stern area as its on my sloping drive . Took the bung out this evening and about a egg cup full came out , so some is getting in around the deck drain . Maybe its the outside of it leaking more. So out with the deck drain fitting and re seal then try again .

Other than the bolts that hold the engine on I can't see anything else there to leak .

jgrace · 12 July 2006, 20:19

Quote:

Originally Posted by ian parkes

I filled the inside of my boat with about 4 inches of water tis morning. It only filled the stern area as its on my sloping drive . Took the bung out this evening and about a egg cup full came out , so some is getting in around the deck drain . Maybe its the outside of it leaking more. So out with the deck drain fitting and re seal then try again .

Ian, when you say you filled "the inside of your boat" do you mean the deck or the hull void underneath? I think you mean the deck, but if so, then an eggcup-full is practically nothing. If I had 4" of water permanently standing on the deck and two or three eggcup-fulls got down into the hull every 24 hours, I wouldn't have a problem.

Jim

ian parkes · 12 July 2006, 21:32

Yes filled the deck area with the boat facing stern downhill as if on a slipway .
What I was getting at was that if a little water was getting through the deck drain fitting from the inside then its not sealed and a lot of it could be entering from the outside when the boat is afloat .

Daniel TD5 · 12 July 2006, 21:33

has it got a front anchor locker if so it leaking from that all later 2002/2003
have solas sealed hulls which don,t leak the front anchor lockers are open to allow water in to the hull

http://www.rib.net/forum/showthread....ht=solas+hulls

all early anchor lockers were part of the formed deck at all leak new designs
were a fixed box type which sorted the problem

dan

ian parkes · 12 July 2006, 22:15

Yes it is the type with the anchor locker as part of the hull but the water isn't getting in there as its never had enough water on deck to fill up . I have filled the anchor locker and it holds water ok .

As for a sealed hull there can be no such thing surely , it has to breath or it would swell up in the sun and implode in the cold .

I won't be happy untill i have a pump fitted , what if the hull is damaged while at sea , the more I think about it the more I want a pump , its just a question of how to do it .

jgrace · 12 July 2006, 22:50

Quote:

Originally Posted by Daniel TD5

has it got a front anchor locker if so it leaking from that all later 2002/2003
have solas sealed hulls which don,t leak the front anchor lockers are open to allow water in to the hull

http://www.rib.net/forum/showthread....ht=solas+hulls

all early anchor lockers were part of the formed deck at all leak new designs
were a fixed box type which sorted the problem

dan

My front locker's always got water in it, but that doesn't mean it's not where water gets into the hull. Must take a look.

Jim

jgrace · 12 July 2006, 22:52

Quote:

Originally Posted by ian parkes

I won't be happy untill i have a pump fitted , what if the hull is damaged while at sea , the more I think about it the more I want a pump , its just a question of how to do it .

I agree completely!

Jim

Nos4r2 · 13 July 2006, 01:25

RE the foam filling idea- I used to spend quite a lot of time on iboats.com and pretty much everyone on there that restored a boat had problems with foams soaking up water. I wouldn't do it.

Why not fit a one-way drain plug to the transom instead of a normal bung? That way it'd automatically drain as you got on the plane. I've seen one fitted to an sr5.4 that had the flooding hull blocked up and the guy swore by it.

(edit) just googled them-self bailing plugs and expanding plugs to seal them when not in use. Any good?

Polymarine self-bailing plugs

Just bought myself the proper plug rather than my sanded down wine bung and a self-bailing diaphragm after finding that!

jgrace · 13 July 2006, 08:10

Quote:

Originally Posted by Nos4r2

Why not fit a one-way drain plug to the transom instead of a normal bung? That way it'd automatically drain as you got on the plane. I've seen one fitted to an sr5.4 that had the flooding hull blocked up and the guy swore by it.

A friend of mine has something like that to suck water out of the hull when planing. Problem is it lets water in when the boat's at rest

Jim

Nos4r2 · 13 July 2006, 11:27

Thats why you carry the expanding plug as well-for when your hull's drained.

Ezgoing · 13 July 2006, 12:08

Jim

Just noticed your thread. Sorry to hear about your challenge. It is amazing how a small leak can create so many problems.

From expeirience I would say that avoid cutting into the deck if at all possible. More often than not that measure creates more follow-on problems.

Regarding the absolute need to get access to the hull for a pump Ribs have been designed not to require this. If something serious happens your hull then you will be relying on your tubes, you will be in some sort of an emergencey and won't be hanging around. A bilge pump probaly won't make much difference.Better get the problem solved.

Flooding the deck can be a great way of finding the leak. With boat on trailer flood the deck with garden hose. Keep deck drains closed. open bung in hull. If there is a leak the water will flow into the hull and out the bung. The water will stop running when the water level has drained to the level of the leak. you should then be able to identify where the leak is. If yu think your deck drain is leaky then seal this with Sikaflex before you start.

It is amazing what you will be able to repair with a tube of Sikaflex!

Always best to try to let the hull dry for 24 hrs before applying the sikaflex.

Remember you may have a number of leaks so test after getting the first leak. Keep repeating the process until you get them all.

Best of luck.

Searider · 13 July 2006, 13:46

Just in the process of fitting a pump to remove any acumulated water in the void of my boat.

My cable runs are difficult to seal and if the well at the stern fills up then water goes under the deck.

Have had a bulkhead fitting made up - basically a piece of stainless tube with a flange welded on part way along it. The short end is long enough to fit a hose to, the long end is long enough to reach into the bottom of the bilge.
A small hole (the diameter of the tube) was then cut in the deck and the bulkhead fitting screwed in place.

The top of the bulkhead fitting is then connected to an inline (self priming) pump in one of the seat pods and the necessary piping led overboard over the transom.

Unfortunately self priming pumps with a decent flow rate cost £££ but this is what I wanted so I paid up!

Also have 2000gph pump in the well at the stern.

Had to reseal the transom drain bung fitting when I got the boat.

Good luck

jgrace · 13 July 2006, 15:26

Quote:

Originally Posted by Nos4r2

Thats why you carry the expanding plug as well-for when your hull's drained.

The friend's one-way flap is on his hull drain, can you use an expanding plug on a hull drain?

I don't fancy putting my head in the water next to the prop trying to plug the hull drain after it has emptied!

Jim

jgrace · 13 July 2006, 15:49

Hi Ez!

Quote:

Originally Posted by Ezgoing

From expeirience I would say that avoid cutting into the deck if at all possible. More often than not that measure creates more follow-on problems.

Regarding the absolute need to get access to the hull for a pump Ribs have been designed not to require this. If something serious happens your hull then you will be relying on your tubes, you will be in some sort of an emergencey and won't be hanging around. A bilge pump probaly won't make much difference.Better get the problem solved.

I take your point about cutting holes in the hull, and about how useless a pump would be if you got a really big leak. And as you say, the tubes should always keep you afloat.

Nevertheless, my hull is hollow and keeps filling up with water when I leave it afloat. It may not have been designed to need bilge pumping but it does!

Since yesterday I've now got a completely new hull drain fitting and screw bung so I'm hoping the whole problem's been cured. If the water's still getting in, I'll try your deck flooding technique, but I'm not sure it will help in my particular case. I'm pretty certain my leak is under the waterline. The sheer volume of water I got in the hull in 48 hours can't be explained by rain.

Jim

jgrace · 13 July 2006, 15:52

Quote:

Originally Posted by Searider

Have had a bulkhead fitting made up - basically a piece of stainless tube with a flange welded on part way along it. The short end is long enough to fit a hose to, the long end is long enough to reach into the bottom of the bilge.
A small hole (the diameter of the tube) was then cut in the deck and the bulkhead fitting screwed in place.

Neat!

What diameter tube are you using?

Jim

Daibheid · 13 July 2006, 16:20

That hull drain flap valve at the end of hte keel is a feature on Griffins but can be finicky and at 2" diameter can suck a lot of water in fast. The previous owner of my boat had sealed it up with screws and sikaflex and fitted a half inch screw drain bung. He also fitted a bilge pump - the 'Whale' diaphraghm type.

I can tell you these things will wear you out pumping a rib hull dry.

However a little water inside the hull hammers the sealed flap open after a while causing an isidious leak. It gave me a few anxious moments looking at it on a mooring over a few days. So I repalced the origianl flap valve but added an adjustable tension cord from the centre into the hull and up through a deck drain to keep it shut snugly. If I don't get the tension right it won't drain the water when planing and too loose can actually prevent it sealing properly and the inrush can stick it open. Great when I get it set up right and I'm just about ready to junk the pump off the transom.

Unlike most Ribs the Griffins are designed to allow water drain into the hull but have two very large buoyancy tanks built in to the hull as back-ups for a holed hull or indeed when it rains or when you ship a few waves (or waterlogged middleaged wannabe wakeboarders). Mine is a bit over-engined so sits low in the water at rest and when the hull fills the tubes are adding a lot of buoyancy - not a situation I really like so I'd been thinking about some foam etc in the hull as a reserve. I would caution against most of the expanding foams as most absorb water so could long term give a serious weight problem that no pump would solve!

One possible solution if you can get any kind of access to the hull is to stuff in a few soft water containers, let them expand and screw the caps back on. I had these in a performance sailing dinghy from the manufacturer and they never made any noise but added huge reserves if a buoyancy tank was to get holed. Anything like that is going to cut down the amount of water that can get into the hull. As an aside the Allies in WW2 stuffed some ships full of empty oil drums and completely puzzled some Uboat captains who found they couldn't sink them after multiple topedo hits. The drums had to 'leak' out before the ships would sink. I know where there's an empty oil drum if it's any help<GRIN>