Guns and Bilges

[middle_watch]

Two part query:

Bilges and bilge pumps, any wisdom to be shed? Seems like a sensible inclusion to a low freeboard model with (hopefully) fairly high speeds.

Second query unrelated: love the guns in the Deans Marine kit for the Dog boat, but they do not seem to offer them seperatly, is there a supplier of such things? Seen some in WEM but not what I was after.

[kennylibben]

wait, you want a pump to pump out water?

my suggestion - patch the holes.

but if you do want a pump in there then i'll post some stuff on helping you, hopefully sean can give some pointers to the actual pump as i'm not much of a technical person.

[middle_watch]

I just love gadgets Kenny!

Seriously, reading other builds of Dog boats and talking to proud owners they all report water ingress. I had in mind forming a channel to catch any loose water and a simple pair of bare contacts to switch on the pump when water hits them. Probably over kill but it was just a thought.

[kennylibben]

nope, in fact i recommend it.

For the channel i would take a 1/4 inch square rod of wood, whatever kind you can find, and place two running down the middle of the ship, leaving about 4 inches from the bow and stern. Then take some silicon and fill in on the sides of the wood and sloping up the sides of the hull. At the bow and stern have it sloping down into the channel. Let dry (might take a while), and epoxy the remaining wood. I'll pm sean to see if he can recommend some stuff for pumps.

[Sean Hert]

Now this is a topic I have LOTS of experience in! (Thanks to Kenny for the heads up!)

The bare contacts thing as a sensor never works (might kinda work with salt/brackish water).

I have a diagram for wiring your own up, which I have tried. It works- sorta. Usually, by the time the water is deep enough to engage the pump, it's too late. Plus, there's almost always a priming issue- it takes to pump so long to prime, and force the air bubble up and out, the usually wins.

However, here's an old article from the old MBG site I archived on how to make your own;

http://www.modelwarships.com//features/ ... topump.htm

I've also tried float switches, using a magnet and a reed switch- didn't really work either.

So, I've become a firm believer in the KISS principle of bilge pump activation;

1) A dedicated channel on my radio so I can periodically turn the pump on and off-

2) Letting the pump run all the time.

Option 2 virtually requires a dedicated pump battery.

Here's another article I archived that shows how to make your own pump. I've made numerous pumps this way, and they all work GREAT.

http://www.modelwarships.com/features/h ... n_pump.htm

When I make a water channel, I also like to build my battery boxes between the hull and the channel. I fill any empty spaces with foam, then epoxy the heck out of everything to make it watertight.

Water channeling is good- and remember, water is going to want to travel aft when the ship is in motion, and fwd when you slow and stop. Lots of water in the hull can build up a bunch of inertia, and can really cause your ship to swing and oscillate wildly in turns.

[middle_watch]

Brilliant stuff, thanks! Will have a go, but I will pass on building the pump myself, if memory serves there is a small pump available which is designed to run off a battery drill, used for filling and emptying model aircraft fuel tanks. I have a small motor which I used for the prototype Dog Boat that I know runs well off a standard 9v radio battery so will see what I can come up with.

Thanks again!

[Sean Hert]

People also use windshield washer fluid pumps- but they aren't designed for a constant duty cycle, and usually have a higher than average current draw. The pump from old Yugo's was a favorite. So, maybe a junkyard.

I have also seen little cheap plastic Chinese toy boats that have a little waterpump for propulsion in them- cannibalizing them would work.

It's usually not hard to find/bodge some sort of pump together. I can usually build a pump from that design I posted in about 1.5 hours.