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Old 26 October 2011, 03:24   #1
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Elephant Drains

My Rib does not have elephant trunking fitted, only time I needed them was once after hitting a big wave and getting loads of water in the Rib, however the bilge pump took care of it. I am interested to hear if anyone has any views whether they feel they are definately useful or not needed in most conditions playing around southcoast etc. Cosmetic or usefull ?
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Old 26 October 2011, 03:55   #2
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!

Little to go wrong with the trunk and so it is a very good backup or even alternative (as long as you can get on the plane) to a bilge pump.

I have had bilge pump failures in fairly messy waves whilst crossing the Solent and was grateful that we could lose the water from the RIB quickly.
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Old 26 October 2011, 04:25   #3
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Interesting point ....

I considered fitting them to my Avon, but in reality wimped out of drilling a really big hole in the boat....and fitted a small ( the smallest RULE) pump. This was just to get rid of water carried into the boat after skiing /swimming etc as I realised I'm never going to go anywhere where I may have to empty the boat quickly , or get that much water in it anyway.

I had deck drains (with a removable stopper and rubber flap - not the proper trunk) that I also never used in 3 years on the Shearwater. I think I only ever used the main bilge pump once in anger and that was due to having alot of weight in the back and stopping to fast.

On a differant level when I was working for Steve the elephant trunks were invaluable. Maybe because we ran in rougher water or due to design I'm not sure but they were used most trips apart form the flat calm days... even if just to make sure customers feet didn't get wet at all.
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Old 26 October 2011, 04:36   #4
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I realised I'm never going to go anywhere where I may have to empty the boat quickly , or get that much water in it anyway.
You are aware that there is a man called Sod who wrote a law that is instantly evoked by statements like that?

Trunks for me every time. Even if you are brim full (and I've been there) even if you aren't on the plane it's like the "cat flaps" on dingies - any forward movemet will asssist in letting Newton's laws take care of the water. I have two, both operable from the driving seat.


Granted drilling a 70mm hole in your transom is a bit unnerving.......
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Old 26 October 2011, 04:58   #5
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You are aware that there is a man called Sod who wrote a law that is instantly evoked by statements like that?

Yep - but it really is a 'beach' boat and 5 years in still OK ( watch this space for photos of it full of water ! ) .

Oddly the only boat I have owned and had to drain alot of water from was my 380...mainly as had a constant medium sized waterfall in over the transom. So as fast as it came in it went out the drains...must raise the engine an inch !
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Old 26 October 2011, 05:01   #6
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My view, yes you should have them. They are an extra "tool" you can use if needed.
I rarely have to use mine as the auto pump takes care of any build up but a quick example of when they were needed:
A launch in the Conwy river earlier this year had to be a bit hasty due to a jet skier who had fallen off and was being pulled out into the estuary on the tide. The wind over tide was creating up to 10ft waves. Because I was solo and the casualty was a big fella it took longer to get him in the RIB than I would have liked. All the time I had breaking waves filling the rib! By the time he was in and safe I was standing in 8" of water. The pumps were working, but the trunks drained the water almost immediately. The ILB turned up about 10 minutes later and commented they hadn't seen sea conditions like it since january.

Not a planned event but the trunks did there job perfectly. The more armour you have the safer you are likely to be when it goes a bit wrong.
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Old 26 October 2011, 05:07   #7
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All good advice, my Rib seems very dry most of the time, only time ive had a lot of water was when I stuffed it into a wave which I knew at the time was going to happen and didnt bother backing off as I was having too much fun.

I was out last sunday and the waves coming down the swash channel near Poole were massive beasts and still the boat was pretty dry, I didnt see any other power boaters out that day just some large yachts and many kite and windsurfers.

I dont fancy a hole in the transom, I will ponder some more, might be good for peace of mind.
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Old 26 October 2011, 06:57   #8
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Boris,

I guessing your set is similar to mine. I do have a trunk but the biggest factor would be actually draining from the deck into the bilges so that they can be emptied by the trunk. On mine this is through a number of smallish drain holes under the rear bench seat. (In fact the biggest hole is right over the fuel tank sender which is not a brilliant piece of design) Any decent amount of water would take an age to drain through. Even using a hose to wash the deck can take a while to drain through.

The latest Cobras (and Scorpions) have deck drains/scuppers that exit above the waterline on the transom with rubber flaps to stop water going the wrong way. This may be a more effective solution if you want to add drainage capacity. The trunk creates a big hole in the transom and my worry is that the trunk will tear without me knowing and fill the boat up with no way of easily stopping flow!

(P.S. I should have joined you on Sunday)
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Old 26 October 2011, 07:15   #9
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Good point really around what you are draining - the deck or the hull ?

In my experiance (and opinion) trunks really should be to drain the deck fast as this is where the water gets dumped in bad weather or stuffing etc. This should leave the hull still free of water.

Some boats have drain holes from the deck to a bilge well with a pump , or an open well with a pump.

These boats should then have trunks from the deck straight out the back to clear the large volumes of water that may come in in bad situations.

However even if you leave the trunks down 'most' ribs will just end up with a few inches of water on deck , with the hull itself still empty ( bar the off bits that seep in ) and the boat sitting on the tubes.

If a RIB drains the deck to the hull then I'd be looking at changes . I cant think Cobra make them like this ............but wonder if I am confusing bilge well with hull in OCs post?

A trunk from a covered bilge well is odd --- why have a big hole which the water can only get off via small holes ?
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Old 26 October 2011, 07:21   #10
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Originally Posted by Oscarguitar View Post
Boris,

I guessing your set is similar to mine. I do have a trunk but the biggest factor would be actually draining from the deck into the bilges so that they can be emptied by the trunk. On mine this is through a number of smallish drain holes under the rear bench seat. (In fact the biggest hole is right over the fuel tank sender which is not a brilliant piece of design) Any decent amount of water would take an age to drain through. Even using a hose to wash the deck can take a while to drain through.

The latest Cobras (and Scorpions) have deck drains/scuppers that exit above the waterline on the transom with rubber flaps to stop water going the wrong way. This may be a more effective solution if you want to add drainage capacity. The trunk creates a big hole in the transom and my worry is that the trunk will tear without me knowing and fill the boat up with no way of easily stopping flow!

(P.S. I should have joined you on Sunday)
Last Sunday was pretty horrible with the lareg waves up the swash, I used my time as a practice session going againts the waves at slow speed and then riding them coming back, good practice I would say, bit scary at times but helps me on experience of big waves. The Rib coped brillinatly, the trick was slow speed heading into the waves allowing them to go under the boat rathe than riding them and on way back lots of use of throttle control and going across biggest waves, it was very fun.

Yes ive seen the new type of drainage on the cobras and will probably have those fitted, they have a hole in the rear storage compartment an inch or so above deck level and tubes which flow through and down out to the transom, rather neat finish and easy enouth as an after fit.
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Old 26 October 2011, 07:57   #11
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Peter M,

My post was not very clear. My set up is that the deck drains into the bilges via a number of smallish drain holes and the large hole over the fuel tank sender under the stern bench seat. I think the big hole is there to allow access to the sender but as you would expect allows water to pour all over the electrical connections. The stern of my boat has a huge (1.5 metre) covered locker that contains a bilge well with a bilge pump. The trunk opens into this well as close to the bottom of the hull as possible but off to one side to give clearance for the motor.

I agree that this is not a great design and would prefer to have the deck drain bypassing the bilges completely. However it must be said (touch wood) that I have so far not had any cause to use the trunk apart from on dry land, or worry about the speed at which the deck drains, but there is always a first time... I should think about having some fitted as Boris is considering.
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Old 26 October 2011, 10:10   #12
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I do have a trunk but the biggest factor would be actually draining from the deck into the bilges so that they can be emptied by the trunk.
On my boat, the trunks drain the deck. The bilge is emptied by a 1000gph bilge pump. One of these days I'll add in a second backup pump, as I have experienced the pump screen clogging with debris.

Quote:
The trunk creates a big hole in the transom and my worry is that the trunk will tear without me knowing and fill the boat up with no way of easily stopping flow!
Just start moving forward. Doesn't take a whole lot of speed to get enough pressure difference to get water to leave. You do have to have a plan to get the boat out of the water, though. Nice thing about a RIB is that even if inundated, it's likely not going anywhere.

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Old 26 October 2011, 11:04   #13
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Ive seen ribs with failing pumps after a stuffing, with a boat half full of water, you loose a lot of steerage, and if you have to make a sudden turn you have literally tons of water sloshing over the deck this can make a bad moment really nasty.

Once you get any way on the bow will lift a little causing the water in the boat to move back, in addition you get a small void at the transom as the boat moves forward, these 2 things added together cause enough of a difference to drain very effectively.

in rough weather my trunk goes down till i get back to the harbour or get to slow speed.
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Old 26 October 2011, 17:31   #14
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On my Vipermax I had two drains installed. I've been out in some snotty weather, but I've never deployed them due to the fact I have only stuffed it once. I had a moment of madness and I was being a tit, I was more worried about the tooth that had gone though my lip and blood over the dash than water in the boat

But even then there wasn't much water on board and the deck pump coped with that.

But I would suggest at least one drain. Even if you never use it, there is always a chance that you'll take a big one over the bow and need to clear the water fast. I used my drain in the last RIB I owned that I used several times. You'll be surprised by how differently your RIB sits and handles in the water when up to the tubes in water.
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Old 27 October 2011, 02:20   #15
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I have two 3" trunks for the deck of my Parker, no deck pump. Plus an automagic rule pump in the bilge (and a bucket as 2nd line of defence for the bilge).
Key in safety critical systems is to have redundancy, and to not rely on active devices (ie switch, electrickily) as the fallback option.

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Old 27 October 2011, 03:03   #16
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The trunk creates a big hole in the transom and my worry is that the trunk will tear without me knowing
My trunk was about to hit it's 25th birthday when it cracked slightly at the fold & started weeping- I've had more water coming in from between the toobs & the hull on other boats than that trunk leak!

Quote:
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and fill the boat up with no way of easily stopping flow!
1) engage forward gear.
2) opren throttle.
3) job done!


Seriously tho' my old SR4 had no trunks, and the time it got swamped, it was a 10 minute slog with a bucket to get the water down to a level it would stand half a chance of getting on the plane to use the silly wee Searider "hole in the floor" drain. That swamping also managed to fill the main battery switch with salt water. 2 hrs later the Garmin 12 switched to it's internal battery, if that puts things in perspective.

Trunks are good.
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Old 27 October 2011, 03:28   #17
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I retro fitted my trunk to the Valiant DR 490. It is about 1 hrs work. Time well spent and very easy to do.
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Old 27 October 2011, 09:21   #18
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Used to run with both trunks down on my SR4, made cleaning the deck easy, hard astern then full ahead.
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Old 27 October 2011, 10:29   #19
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Plus an automagic rule pump in the bilge (and a bucket as 2nd line of defence for the bilge).
Can you get a bucket into the bilge to empty it?

Can't on mine (only access is through an 8" round hatch on the motor pod.)

jky
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Old 27 October 2011, 14:43   #20
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Can you get a bucket into the bilge to empty it?

Can't on mine (only access is through an 8" round hatch on the motor pod.)

jky
yes
but a smallish bucket only, diameter abt 15-20cm
via the engine bay of the inboard

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