Automatic Bilge Pump Switch

[MedMan]

I have always had problems in fitting a fully-automatic bilge pump that I could rely upon due to the configuration of my boat's hull. I am hoping that forum members may be able to help me solve them.

My boat is a Trident Voyager 35. She has a full length keel as shown below:

There is a glassed-in tray in position A extending all the way from the ballast to the stern. The only holes in this tray are a 25mm drain hole below the engine, a 50mm hole for the pipe leading to the manual bilge punp and a 25mm hole for the pipe leading to the electric bilge pump. The void below the tray is approximately 1 metre deep and 2 metres long and it is 10cm wide at the bottom and 70cm wide at the top. That is quite some void with the capacity to hold a lot of water!

My problem is where and how to site an automatic switch to control the pump. I have already concluded that it will have to be an electronic switch rather than a float switch, but where and how do I mount it?

 

[tugboat]

I have a steel boat with a deep bilge sump and my arrangement works well. You need a wood batten about 50mm wide and long enough to touch the bottom of your bilge sump. Attach a foot piece at right angles on the bottom end and attach your pump and float switch to that. The thinner the foot piece - the less water you will have left. Attach the discharge hose and electrics cable to the vertical batten at intervals. You will probably need to fit a right angle connector where the hose emerges which you can disconnect in order to withdraw the pump/switch for maintenance. When the rig is lowered into place, secure the batten to something convenient so the pump can't lift off the bottom. Mine is held with a couple of cable ties. HTH.

 

[LadyInBed]

As the void is the problem, you need to reduce it’s volume. I would fill it with (say) expanding foam or the like, maybe foam in a hose pipe to the lowest point of the void so you can suck up the last dregs, then you can seal off the void with (say) a sheet of Formica or Perspex then Sicoflex it in.

I don’t think an auto bilge pump switch is a viable option in your situation, unless you put it on the tray below the engine.

 

[Shantyman]

I think nigelB has the right idea. I cannot think of owt worse in a boat than an inaccessible void space.

I would however not simply fill it up with foam.

If there is sufficient access to the glassed-in tray itself, I would cut a hole in it about 12" diameter and then fill the void with foam. I would then hollow out the foam in way of the aforementioned 12" diameter hole to make a nice little sump deep enough to hold at least a couple of gallons of bilge.
I would then line this with glass/resin and at the same time glass in a mounting for the float switch.

This will make your float switch accessible and also enable you to easily keep the bilges relatively clean by reducing the tendency of the bilge liquids to slop around the relatively shallow tray.

Cheers.
Have fun.

Shantyman.

 

[smb]

My Voyager 38 has the same arrangement as Tugboat only in SS. Works a treat and the complete assembly can be easily withdrawn for maintenance/cleaning.

Unlike you however I do not have the tray, the sump is open on the 38' with only the propshaft in the way. You do not say what the tray is made of, but my guess is you could cut say a 4'' hole to pass the pump and switch through then make a bracket to attach the shaft to the edge of the hole or if you want/need to cover the hole fit the shaft into a 6'' cover plate bolted or screwed in place.

Steve

 

[Shantyman]

Looking at your drawing again I would be inclined to make quite sure there is nothing in the void that you may need access to at a later date.

For instance, it may be worth checking how the lower rudder mounting is fixed to the keel, i.e. is it through bolted into the void??

 

[MedMan]

Thanks for your thoughts. To answer a few of the questions raised:

The tray is fibre glass. The area below the engine is clearly inaccessible, but the area aft can be reached through a 40cm x 40cm hatch in the floor. The tray is about a metre below the hatch with the shaft running centrally across the space. Drilling a hole through it is certainly possible, but reaching through that hole to cut out and glass over foam would require 2 metre long arms with three elbows!

To the best of my knowledge there is nothing in the void. The lower rudder fitting is a stainless shoe bolted right through the lower aft edge of the keel. I replaced the bolts just after I bought the boat and fitted an anode to the shoe which has kept the bolts and the shoe in good condition since.

I like the idea of the inverted T bar with everything on it. My present electric bilge pump is not actually a submersible type - it is mounted just below the floor and is connected to a length of rigid PVC pipe which drops down through the tray. However, it would seem reasonable to use the inverted T bar just for the automatic switch. Any thoughts on that?

 

[Anonymous]

[ QUOTE ]
I like the idea of the inverted T bar with everything on it. My present electric bilge pump is not actually a submersible type - it is mounted just below the floor and is connected to a length of rigid PVC pipe which drops down through the tray. However, it would seem reasonable to use the inverted T bar just for the automatic switch. Any thoughts on that?

[/ QUOTE ]If you go for a pneumatically operated switch (Jabsco do one) then you only need to affix a light plastic tube to a rod instead of a T bar. Since the electronics and wiring are well clear of the water they are more reliable (in theory, anyway!).

 

[Guest]

Why not have the 'switch' that is based on two electrodes that are separated by a short distance - the rise of water literally shorts the two electrodes and a small current passes enough to kick a relay into operation and pump starts.

The electrodes can be as long as you wish and inserted through the floor and once bottom is felt - lift up a cm or so to ensure that it is water etc. that activates the relay.

Of course you could always fit a normal bilge auto switch to a rod and then insert that via a suitable hole till it touches bottom ? Why should you have to put your arms into the space ?

 

[catmandoo]

In addition to the pneumatic switch you could also fit a duplicate linked to an audible/visible alarm set to go off before the pump . If it was mine I would want to know immediately and why the void filled up particularly since it is so inaccessible

 

[Anonymous]

[ QUOTE ]
In addition to the pneumatic switch you could also fit a duplicate linked to an audible/visible alarm set to go off before the pump . If it was mine I would want to know immediately and why the void filled up particularly since it is so inaccessible

[/ QUOTE ]Good point - my battery condition monitor, the BEP, has a bilge pump monitor as standard, giving the total number of cycles and the total running time since last reset. I find it enormously useful. I have also built to my own design a small circuit that gives a loud audible alarm if the bilge pump should run for longer than a preset time for any reason (I have mine set at 25 secs) so if you have a serious leak at sea, with the engine running and don't hear the pump, you would get a warning very quickly, long before the water has flooded the engine.

 

[Jcorstorphine]

If I have understood the problem correctly, you need to get the detector well down into the keel. Not very keen on electrical type conductivity detectors as they can be confused by oil insulating the electrodes. In industrial application we use tuning fork type sensors which use the damping effect of a liquid to change the resonate frequency of the tuning fork. The fork can be mounted on an extension, in some case I have used a 5 meter stainless steel tube to get down to the bottom of a Pit. The things to think about are power consumption and the fact that most of the units work on 24 volts. Here is a web address of a typical unit. although there are cheaper units on the market.

http://www.keison.co.uk/vega/vegaswing_71.htm

 

[Graham_Wright]

Jabsco are also investigating the use of a "surface tension effect" switch but I know not how far progressed they are. As this information may be confidential please do not read it.

 

[pvb]

Solid State Bilge Pump Switch...

You could certainly use a plastic or metal rod to position a switch in the bilge. There's an interesting solid state switch made by Snake River called the Bilge Buddy. It has 2 separate encapsulated sensors which can be installed at different levels - the upper one turns the pump on; the lower one turns the pump off (with a 5 sec delay to prevent cycling due to water running back down the pipe). Full info in the manual. It's only about £20 from West Marine or other chandlers.

 

[MedMan]

Re: Solid State Bilge Pump Switch...

Many thanks for the information on the Snake River Bilge Buddy. This looks very interesting and could well be just what I need.

 

[MedMan]

If I had read your post it would have appeared to contain an interesting idea but, of course, as it was confidential, I did not! /forums/images/graemlins/smile.gif

 

[MedMan]

Many thanks for the information on Tuning Fork Detectors. I have followed up the link but, as you say, they seem to be 24v only and current draw could be a problem. The detector would appear to consume about 1Ah per day which would not necessarily be a problem with my solar panels running but would soon run the batteries down if there was prolonged bad weather or if a huge gin-palace parked next door and plunged me into shade!