Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[aeronut]

I have a lovely model of a steam tug which gets very lonely on the water as it has nothing to tow.  I've seen a couple of plans/designs for barges/lighters which would make a suitable vessel to tow.  However, the barge would be around 1 metre long and is going to require a serious amount of ballast in order to get it to a realistic waterline.  Now, my ageing back won't take the weight and I'd also be worried about a heavy vessel overbalancing me into the water when launching.  So, I'm wondering if anyone has drawings or even ideas for a practical water ballast system to install.  I'm envisaging a self filling and self emptying arrangement, but haven't yet grasped how this is easily achieved.  I'm not adverse to installing a pumped system, but with batteries etc., this will tend to make it heavier to handle.  Your thoughts and ideas would be most welcome.

[tsenecal]

I have seen someone make their barge out of a long block of foam, with skins along the sides that extended several inches below the foam, with no bottom skin.  when placed in the water, the barge floated on the foam, with those several inches of "skirting" sitting below the waterline, looking for all intents like a real heavily loaded barge.  because it was made of foam and the skins were 1/8 plywood sealed with epoxy, it hardly weighed anything at all.

[Taranis]

Batteries make good ballast (lifted in and out separately) and can drive a high volume pump to evacuate the water
The water can be let in with plumbing valves without power by scuttling into water containers, just shut the tap or taps at the desired waterline
Balne moor MBC use something on these lines

[Tug Fanatic]

It is very simple.

You make a decked barge with a block of foam or a sealed air space that provides the buoyancy. The rest of the decked barge is then an empty hole that has small open entrances top & bottom which fill up with water when you put it into the pond and which empty as you pull it out.  A few 1 inch holes should work in the bottom & some smaller ones in the deck which can be disguised as part of the load etc. The small holes in the deck control the water flow. You obviously need the barge to weigh enough to get the filling up started.

The small entrance & exit make the water behave as part of the barge & thus as ballast. If you leave large holes the water weight never becomes part of the barge.

[Umi_Ryuzuki]

They mean like this,... 
.
There is a copper tube on the topside at, one corner, to vent air as the barges fill, and
one additional hole in the bottom, at the corner, to fully drain the water. 
There are baffles inside the flood compartment to prevent the water from flowing freely.

.

 

[tsenecal]

exactly as umi shows in her photo, except instead of a hole or holes in the bottom board, there is no bottom board. the bottom of the foam board is the bottom of the barge, effectively creating a waterline model that looks like it isn't.   removing all of that volume removes a lot of weight from the hull.

[Tug Fanatic]

exactly as umi shows in her photo, except instead of a hole or holes in the bottom board, there is no bottom board.

I think that there must be a bottom board. The baffles that Aimee mentions and the limited in/out flow capacity make the water behave as if it is part of the barge - making it heavy. If you leave the bottom out of the design the water is still a free agent & all you have got is water resistance rather than mass.

[tsenecal]

why do you feel that you need the mass....


in the illustration, pink is foam, green is built up area, and blue is the "bucket" area if you wish to make something like a coal barge, if you want to make a flat derrick for something like a crane, omit the blue.   in this arrangement, it floats ON the foam board, which makes up the entirety of the real bottom of the barge.  you still have to have the small holes in the corners to let the air trapped by the skirts to evacuate, but when removing it from the water, there is no "de-ballasting".

[CGAux26]

Most of the bottom needs to be covered, else you have free flowing water in and out of the barge.  This will result in very strange handling.  I have a 4' x 1' barge built like Ami says and it works great.  Several good size holes in the bottom makes it quick filling and draining, and baffles in the hull keep the water on board from sloshing around.


It was originally built with a pumped fill/drain system.  Way too slow, plus all the pumps, batteries, and plumbing were a pain in the transom.   

[warspite]

why do you feel that you need the mass....


in the illustration, pink is foam, green is built up area, and blue is the "bucket" area if you wish to make something like a coal barge, if you want to make a flat derrick for something like a crane, omit the blue.   in this arrangement, it floats ON the foam board, which makes up the entirety of the real bottom of the barge.  you still have to have the small holes in the corners to let the air trapped by the skirts to evacuate, but when removing it from the water, there is no "de-ballasting".

And there lies the problem - yes it's light - too light, it can be transported and placed in and out of the water with ease, but with no weight it isn't any real use for towing as it would act like a piece of foam sat on the water - which is all it is, yes there is some resistance and fitting baffles to create some resistance to the  free movement would help but it's not contained MASS which a tow is supposed to be.


With an enclosed bottom the water inside acts just like the weight, baffles restrict the free movement of the water even with holes in the bottom to allow it to empty, the water doesn't escape as the water is held in by the water the hull is in - so it cannot go anywhere and therefore becomes the MASS needed to created a realistic tow, the tug has to look like it's struggling to get the object to move to look right

[aeronut]

OK, thanks for the suggestions Chaps, I now have a good idea of how to proceed.  I think the holes in the bottom, with vents on the upperside seems the best way to go.  I'll have to consider how I'm going to ensure that the inside structure is fully waterproofed.  I'll get the drawings for the lighter which I have in mind and take it from there.  you've all been most helpful.


Gordon