motiondave

bilge pump or not to bilge pump.....

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How olds the boat? 40 yrs old- I would trust that bung as far as i can throw it- Dont worry that its a sealed floor- cut a hole, install the pump-reseal- and then put another above your floor- as was said above- its something you will hopefully never need but the day you do - you wont regret it. In my boat- I run an overflowing livebait tank- so my bilge gets water in it all the time- and I just pump it out- no probs- but every second trip i clean the boat with the bungs in and flush the pumps out with fresh water. Every trip i check the pumps, lights and electronics- the day before I go out and I too put the bungs in at home (after once forgetting to put them in at the ramp)

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Just because a boat is sealed does not mean it can't be swamped. I launched my boat which has fully sealed chambers underneath without the bung once. I used my bilge pump to save me while I foundered around looking for the Bung. Could not find the Bung and bail at the same time. Water will go to the back of the boat and i could see my engine was getting closer and closer to the water. Also it may be fine in the bay but if your out and you get a wave or swell hit you on the side you could well go over. 

Attached is a pic of a Bar Crusher which is also a fully sealed boat. They may not sink but they will definitely flip if you get swamped in the rough or if the swell is peaky.

barcrusher_resized.jpg

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I would not cut into a sealed chamber under any circumstances. Are a lot of them a pressurised as well. 

My boat manual specifically states not to drill into the sealed chamber. Many boats have compartments in the sealed areas anyway so a bilge pump in there will not help. 

I would not breach the sealed chamber. Just replace the bungs. 

 

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2 minutes ago, recurve said:

I would not cut into a sealed chamber under any circumstances. Are a lot of them a pressurised as well. 

My boat manual specifically states not to drill into the sealed chamber. Many boats have compartments in the sealed areas anyway so a bilge pump in there will not help. 

I would not breach the sealed chamber. Just replace the bungs. 

 

How would it be pressurised if its got a bung in it? this is a 40 year old boat and just quietly a gas cylinder wouldnt hold pressure for 40 yrs.

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I have a Surtees and it has two bungs in the sealed chambers and they say it is pressurised and specifically say not to breach it. 

You can do what you like to your own boat of course. Just my opinion. I think it would be a very bad idea. 

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Well, I got given a working 1000gph bilge pump. And after reading the horror stories over overflowing bait tanks, wave wash from beach landings, rain storms, blood, guts, pee.....( Sounds like D day landing,😂😂), I'm going to fit one at the back so if goodness forbid anything like that happens, I'm covered. It will drain passenger area. 
If I'm not required to fit one in the sub floor, them im not going to start chopping 👍
So thanks again everyone for the help.👍👍

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Recurve   a sealed chamber is just that   sealed   if it has a bung in it  then its not a sealed chamber  putting an inspection hatch with screw lid and o ring stops water from entering said chamber once you plumb in a pump  hose  wires and seal all   sealed chambers can be holed and take water   then what do you do while you watch your pride n joy sink ?????  Geez maybe i shoulda put a pump in there  ddooohhhh

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Rickmarlin, I just checked on the web as was many years ago I read the Manual. Pressure tested, not pressurised. So you're right about that. 

I would be following the manufactures advice  

If I hit anything hard enough to breach my hull I would no doubt have big issues that would over whelm any bilge pump. Also most boats have multiple chambers so if one is breached the others won't be. 

Seems like you would be just making a weak link by replacing plate alloy with silicone. 

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Anyway  we all have different ideas on things thats why its such a good forum  the gist of it is he has a pongrass which has an underfloor area the length of the boat that has bungs  same as mine and many other earlier boats  no bilge pump under there is asking for trouble ☠

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I get a bit of water down there from time to time through the cable holes - as water can get down there, I actually fill it up on the trailer with fresh water to get the salt out using the pump. They are worth having

 

 

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3 hours ago, rickmarlin62 said:

Anyway  we all have different ideas on things thats why its such a good forum  the gist of it is he has a pongrass which has an underfloor area the length of the boat that has bungs  same as mine and many other earlier boats  no bilge pump under there is asking for trouble ☠

Dead right Rick, always worry a bit about boats with high "self draining decks" , if you cop a green one and the water is sloshing around on the deck you are in lots of trouble- if its sitting in the bottom of the hull then less so. Center of gravity will be in a very bad place and whooshka- capsize time. Not that "downflooding "is much fun either but it doesnt take much water sitting on the deck to cause big problems.

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Hey Raiders, 

I'm a bit late to this topic, seems there are varied opinions as I am sure people are thinking of their specific craft when commenting but here are my thoughts and considerations.  As always a picture is worth a thousand words ....

Case A :

image.png.d55ee891db310e4e87092ae8f4dfc2f9.png

Simple hull. Everyone would agree that this single skin hull needs a bilge. Also that a properly working and maintained bung is airtight/watertight - otherwise the hull would not float !  Skippers responsibility to make sure everything is working - just like patching up holes in the hull.

Case B :

image.png.3e63f0a04fe3b49fa307ea29daadd230.png

If we add a raised floor, or removable deck nothing really changes. In essence it is still Case A, a single skin craft, however, there is the added risk that you may not immediately notice water entry, so adding a bilge pump is a definite no brainer.

Case C :

image.png.ca448fbe2393cd7d381a2f4764a33f0b.png

The manufacturer has now created a double skin hull with an airtight chamber underneath the sealed raised floor. Yes, I would argue the chamber is airtight if the bung is properly maintained and working. 

If the lower hull is breached the air chamber would fill with water, the craft would ride lower and be less stable but by design the inner hull would still provide floatation.

In this design, the manufacturers also add more bungs to drain the raised deck (or scuppers) if it is a self draining hull etc. MSB rules say no bilge is required (presumably) because there is redundancy in the twin skin design and if everything is working the hull should not sink as it has inbuilt flotation from the airtight chamber. 

Practically speaking though we fishos that go regularly offshore know nothing is infallible - bungs and bung washers included - so we recommend implementing additional redundancy to the MSB reqs by adding a bilge pump.

Case D :

image.png.22e60b5135b41d4298b11fc48ef96cc0.png

This approach preserves the manufacturer inbuilt hull floatation, but drains the deck area should you cop a wave over the side, or drain a bait tank overflow or use the deck wash etc. There are considerations around stability if too much water is in the top deck, but in general, boats designed like this have several air chambers below the deck and the fuel tank is sandwiched in the middle for stability and lowering the centre of gravity of the hull. 

Case E :

image.png.5c08a219483c5db33a1b4c811b2e07bf.png

You can cut through the deck and install the bilge in the below deck chamber. You have removed the inbult hull floatation and have now reverted to Case A / Case B, single skin hull and you definitely need a bilge because you may not immediately notice water entry.

Case F :

image.png.b869e2f10c89e154bfe6df63696f1d39.png

You can seal the deck, where you have installed the bilge pump. But note, the chamber is no longer airtight as the bilge outlet hose acts as an air vent. So in essence you are still in Case A / Case B and you do NOT have inbuilt hull flotation.

A further consideration for this approach is that should the lower hull be breached, you will not be able to pump the water out of the chamber.

image.png.0ea0da26f90d029ae5d473dc478f189e.png

As you start to pump water out, the outlet tube fills and you have now created an airtight chamber, so you will actually be sucking in the same amount of water as you are pumping out. To be confident of pumping the water out of the chamber, you would need to implement an air vent and ensure you have a large capacity pump installed that can suck water faster then it can enter through the hull rupture, so it replaces the water with air sucked in through the vent. (The vent is the same concept as why you must open the breather on your fuel tank to pump fuel out.)

image.png.98d60d22bae13d135dfb513ab67a4a61.png

 

The only other consideration I will add to this is that manufacturers have implemented the above concepts in different ways. My Haines is built with 3 independent subfloor chambers, one on each side of the 250L fuel tank  and one that runs down the middle under the fuel tank. Also Haines have created a bilge well at the stern, so that the bungs to the air chambers are inside the main hull not exposed to the sea.

Hope this picture helps explains the Haines approach (the well is not to scale ofcourse):

image.png.5e6f2f1492c634e4f7e699e8cfcf6356.png

This provides the redundancy of twin hull, airtight floatation chambers but also reduces the risk of a failed bung filling up a floatation chamber. Its a bit of a pita to duck under the rear seat to make sure the well is clean of fish guts etc that may choke up the bilge pump, but that's a small price to pay for what the deign buys me.

Anyway, they are my thoughts, hope it helps.

Cheers 

Zoran

 

 

 

 

Edited by zmk1962
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Hi all...some boats have the air tight sealed chambers filled with foam,which displaces water.

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1 hour ago, back cruncher said:

Hi all...some boats have the air tight sealed chambers filled with foam,which displaces water.

I actually considered filling my subfloor area with spray foam. Would solve any issue if the hull got damaged, except the foam might fall out....but still no water would come into main part of boat

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3 hours ago, zmk1962 said:

Hey Raiders, 

I'm a bit late to this topic, seems there are varied opinions as I am sure people are thinking of their specific craft when commenting but here are my thoughts and considerations.  As always a picture is worth a thousand words ....

Case A :

image.png.d55ee891db310e4e87092ae8f4dfc2f9.png

Simple hull. Everyone would agree that this single skin hull needs a bilge. Also that a properly working and maintained bung is airtight/watertight - otherwise the hull would not float !  Skippers responsibility to make sure everything is working - just like patching up holes in the hull.

Case B :

image.png.3e63f0a04fe3b49fa307ea29daadd230.png

If we add a raised floor, or removable deck nothing really changes. In essence it is still Case A, a single skin craft, however, there is the added risk that you may not immediately notice water entry, so adding a bilge pump is a definite no brainer.

Case C :

image.png.ca448fbe2393cd7d381a2f4764a33f0b.png

The manufacturer has now created a double skin hull with an airtight chamber underneath the sealed raised floor. Yes, I would argue the chamber is airtight if the bung is properly maintained and working. 

If the lower hull is breached the air chamber would fill with water, the craft would ride lower and be less stable but by design the inner hull would still provide floatation.

In this design, the manufacturers also add more bungs to drain the raised deck (or scuppers) if it is a self draining hull etc. MSB rules say no bilge is required (presumably) because there is redundancy in the twin skin design and if everything is working the hull should not sink as it has inbuilt flotation from the airtight chamber. 

Practically speaking though we fishos that go regularly offshore know nothing is infallible - bungs and bung washers included - so we recommend implementing additional redundancy to the MSB reqs by adding a bilge pump.

Case D :

image.png.22e60b5135b41d4298b11fc48ef96cc0.png

This approach preserves the manufacturer inbuilt hull floatation, but drains the deck area should you cop a wave over the side, or drain a bait tank overflow or use the deck wash etc. There are considerations around stability if too much water is in the top deck, but in general, boats designed like this have several air chambers below the deck and the fuel tank is sandwiched in the middle for stability and lowering the centre of gravity of the hull. 

Case E :

image.png.5c08a219483c5db33a1b4c811b2e07bf.png

You can cut through the deck and install the bilge in the below deck chamber. You have removed the inbult hull floatation and have now reverted to Case A / Case B, single skin hull and you definitely need a bilge because you may not immediately notice water entry.

Case F :

image.png.b869e2f10c89e154bfe6df63696f1d39.png

You can seal the deck, where you have installed the bilge pump. But note, the chamber is no longer airtight as the bilge outlet hose acts as an air vent. So in essence you are still in Case A / Case B and you do NOT have inbuilt hull flotation.

A further consideration for this approach is that should the lower hull be breached, you will not be able to pump the water out of the chamber.

image.png.0ea0da26f90d029ae5d473dc478f189e.png

As you start to pump water out, the outlet tube fills and you have now created an airtight chamber, so you will actually be sucking in the same amount of water as you are pumping out. To be confident of pumping the water out of the chamber, you would need to implement an air vent and ensure you have a large capacity pump installed that can suck water faster then it can enter through the hull rupture, so it replaces the water with air sucked in through the vent. (The vent is the same concept as why you must open the breather on your fuel tank to pump fuel out.)

image.png.98d60d22bae13d135dfb513ab67a4a61.png

 

The only other consideration I will add to this is that manufacturers have implemented the above concepts in different ways. My Haines is built with 3 independent subfloor chambers, one on each side of the 250L fuel tank  and one that runs down the middle under the fuel tank. Also Haines have created a bilge well at the stern, so that the bungs to the air chambers are inside the main hull not exposed to the sea.

Hope this picture helps explains the Haines approach (the well is not to scale ofcourse):

image.png.5e6f2f1492c634e4f7e699e8cfcf6356.png

This provides the redundancy of twin hull, airtight floatation chambers but also reduces the risk of a failed bung filling up a floatation chamber. Its a bit of a pita to duck under the rear seat to make sure the well is clean of fish guts etc that may choke up the bilge pump, but that's a small price to pay for what the deign buys me.

Anyway, they are my thoughts, hope it helps.

Cheers 

Zoran

 

 

 

 

Good job and good explanation. To be honest, I've never been out into big seas, potential storm rain, etc , to possibly fill water into my main part of boat. Granted I forgot to put bungs in one time and launched boat into water, came back about 5 mins later and remembered I forgot. Was only about 5-6 lites water on the back. I just obviously put bungs in and sponged water out. 

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9 minutes ago, motiondave said:

actually considered filling my subfloor area with spray foam. Would solve any issue if the hull got damaged, except the foam might fall out....but still no water would come into main part of boat

Any foam you put in there will be a little damp and hold some moisture (condensation etc). So I would not recommend doing that unless all the boat stringers are full resin (like Seafarer). Any dampness/moisture in there would just accelerate the wood root. Better to open the bung and let the cavity drain and air in my view.

Cheers Z

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9 minutes ago, motiondave said:

Good job and good explanation. To be honest, I've never been out into big seas, potential storm rain, etc , to possibly fill water into my main part of boat. Granted I forgot to put bungs in one time and launched boat into water, came back about 5 mins later and remembered I forgot. Was only about 5-6 lites water on the back. I just obviously put bungs in and sponged water out. 

I don't think anyone actually plans for it to happen (unless you are a manufacturer testing the hull)..   but it does.  Have headed out in dead calm, with calm predictions only to have squalls turn up that have waves coming over the bow and across the front screens.  Wash from ferries or large cruisers can easily be over 1m high with a sharp standing wave. If it hits you side on, chances are you will take water. 

Be prepared is the motto.

Cheers Z

 

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1 hour ago, zmk1962 said:

Any foam you put in there will be a little damp and hold some moisture (condensation etc). So I would not recommend doing that unless all the boat stringers are full resin (like Seafarer). Any dampness/moisture in there would just accelerate the wood root. Better to open the bung and let the cavity drain and air in my view.

Cheers Z

True. Didn't think of that....

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1 hour ago, zmk1962 said:

I don't think anyone actually plans for it to happen (unless you are a manufacturer testing the hull)..   but it does.  Have headed out in dead calm, with calm predictions only to have squalls turn up that have waves coming over the bow and across the front screens.  Wash from ferries or large cruisers can easily be over 1m high with a sharp standing wave. If it hits you side on, chances are you will take water. 

Be prepared is the motto.

Cheers Z

 

Good point. Can get a bit "hairy" going through harbour in 4.5 m runabout. Dem damn wake waves are about 1m. I usually slow down and steer I to them at 90 deg angle. Boat goes ok through it. 

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6 minutes ago, motiondave said:

Good point. Can get a bit "hairy" going through harbour in 4.5 m runabout. Dem damn wake waves are about 1m. I usually slow down and steer I to them at 90 deg angle. Boat goes ok through it. 

Yes slow down. You may want to try a little off 90 rather than square on - you'll have a better chance of keeping your prop in the water as the wave goes under and the stern goes up (prop in water = thrust and steering).... and your bow will not bury as much. 

It's something I learnt crossing the bar at Huskission in a Savage Avalon runabout (16ft, 4.5m).  This approach work for me then and also works in the bigger Haines. 

BTW... that bar is long gone....along with the afternoon entertainment and excitement it brought to the local RSL club patrons.

Cheers Z

 

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24 minutes ago, zmk1962 said:

Yes slow down. You may want to try a little off 90 rather than square on - you'll have a better chance of keeping your prop in the water as the wave goes under and the stern goes up (prop in water = thrust and steering).... and your bow will not bury as much. 

It's something I learnt crossing the bar at Huskission in a Savage Avalon runabout (16ft, 4.5m).  This approach work for me then and also works in the bigger Haines. 

BTW... that bar is long gone....along with the afternoon entertainment and excitement it brought to the local RSL club patrons.

Cheers Z

 

Well....90 ish either way😁. Scares the s...t out of passengers when I do though...😂😂👍😂👍

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