Hi Peter,
Our boats are relatively small so we can usually trim and ballast them with useful "payload", i.e. decent size batteries for longer run times instead of "dead lead"!
I don't think any of my ships (up to 1.5m) weigh more than about 5kg max.
My Sea Scout is about 2.1kg. Runs full bore for around an hour on a 4Ah LiPo😊

WO Nerys is also absolutely right👍
My Sea Scout didn't need extra ballast, it trimmed perfectly with a 4Ah Lipo.
My long thin naval ships (LoA to Beam ratio ca 10 to 1) and a lot of top hamper, do need ballasting, so I use one or more SLA batteries so I can patrol all day if I want to😊
Trimming is a doddle, just move the SLA(s) fore or aft to suit.

That tug with 20kg ballast must be huge😮
I've seen huge (>2m!) models of container ships and tankers etc over here, which use car batteries for power thus reducing the need for dead ballast.
Such ships are often built in two or three sections bolted together at double bulkheads with computer type D-shell electrical connections. Must take a lot of detailed planning. Doh my head aches 🤕
Ya pays yer money and takes yer choice!
Cheers, Doug 😎

Ah. Thank you. They seem to run well so should be ok.😊

All depends on the boat, if it is fairly wide beam, you probably don't need any. Rule of thumb is that if it is long and narrow, you probably will. Also depends on the type of boat. My Dutch Coaster needs it wheras my Sea Commander motor cruiser doesn't. My Thames Barge needed a little just to trim her properly. I'm building a motor barge at the moment, she will need a little to keep her prop underwater. Usually a scale model of a ship and particularly naval ships, being long and narrow and probably a bit top heavy will need ballast.

Cheers,
Nerys

Good question, there is no fixed rules, but if the model is built from lightweight materials it will sit higher in the water than the same model built with heavy materials. Also the weight of the the control fittings and the additional external fittings can also determine the amount of ballast needed. So it's trial and error in the test tank before a trip to the lake. By having movable ballast you can balance your model to get the best results. Usually what looks right is right.
Cheers Colin.

I must be doing something wrong. I do not have ballast in any of my four boats. How can you tell if you need it. Is it always necessary or only if the boat does not sit level. Sorry for the basic question but just shows I don`t even know the basics.😔

Hi Nerys,
I like that idea.
Sand barge with its own natural ballast.

Martin555.

My large model tug requires almost 20kg ballast. I use lead scrap, melted and poured into cube-shape plaster of Paris moulds of about 4kg size. Before the lead sets I insert a small lop of stainless cable to form a handle. These lead cubes fit into 'pockets' built into the model.

Now there's an idea for a new model, one of the sand barges that run from the River Colne up to London with cargoes of sand and ballast for building operations. Leave the hatches open, couple of heaps of sand which will bring her down to a load waterline and there we have it, a 'working' replica, and naturally ballasted.

Nerys

I'm with you Nerys👍
Sounds good but sand is simply too bulky for my ships.
And as you say the lower the better for stability.
Guess the sand works well for large wide beam boats, but not so good for my high LoA to Beam ratio naval ships, up to 10 to 1 or so.
I also use lead shot, bought in 1kg bottles from Krick, to do the ballast test.
When I know how much weight I need I still have some chunks of lead left from a visit to an MBB (now part of EASA / ESA?) scrap metal shed.
Guy who took me there was a neighbour and friend of mine who was responsible for the machine shop which made the motor casings and burner tubes for the ARIANE 5 rockets.
Some exotic metals in that shed!
For final trimming, also on aircraft, I have cards of several 5gm lead trim weights, also from Krick. Cheers, 😎

Hi Colin,

I tried using sand in my Dutch coaster, but despite the fact that it moulds nicely to the hull, I found it too bulky, so replaced it with lead shot. This came from Ebay and I found a seller who did larger quantities at a relatively competitive price. I put 100 gms in a longish freezer bag, tie a knot in it as tight up to the lead as possible. Turn it inside out and tie another knot. Roll the surplus around the package and seal with sellotape. Then use velcro to stick it in place. My Dutchman was far better with the lead than the sand as it was lower in the hull, thus giving more stability. I have since used a couple of 100gm bags to balance my Thames Barge and will do the same in my motor barge, nearing completion, to keep the prop nicely under water.

I liked your idea of getting lead from tyre fitters!

Cheers,
Nerys