Indeed flaxbybuck. I have to add some 25kilo ballast to get her to loaded draft and as a 174cm model I can't afford any weak spots. Originally I intended to use the space in between the frames as water tanks to fill to achieve draft required. Since this would have required to drilled holes in the bottom I eventually opted against it and will use concrete blocks.

Hi Jock, I congratulate you again for the work you are doing and the method you are using.
The structure seems very robust and adequate for the enormous size. You're really smart.
A curiosity: you intend to use concrete as ballast, did I understand correctly?

Just a crazy idea about painting the melamine, how about painting the backside?
len

Len, it would be pointless as the melamine has a rough underside to better adhere to glueing. I thought of the melamine as the surface is slick, hard, waterproof and other then prior preparation for better paint adhesion requires no treatment. It is however more difficult in cutting and shaping cut out forms as it is a much harder material than let's say plywood.

Hi Jock, you can ask me whatever you want, don't worry, it's a pleasure for me. If I don't know the answer or my knowledge isn't sufficient to answer you, I'll simply say: "sorry, I don't know".
I was about to comment (doing some calculations without 3D drawing software, no need) on your post but before doing so I would like to know something else:
Do you intend to place blocks of already solidified concrete in the hull and then fix them in some way or do you intend to make a casting inside the hold and then let it solidify in the hull itself?

I hope the transport system to the place of sailing, and launch facility are strong - I see portable cranes coming into play - come to think of it what a cool way to pick up your boat from the back of the car/van on a crawler crane, with remote control, then that takes it to the launch site and carefully lowers the boat into the water, or even crawls into the water from a sloping beach!!🤔😂

Hi Jock, this answer reassures me somewhat. Being able to remove ballast is better especially for ships of this size. In fact, I would first put the model in the water (empty or only partially ballasted) and then insert the various ballast modules in the pre-established and previously tested points.

What I will tell you is absolutely not a criticism but another point of view.

Even though concrete is very cheap, I would never choose it as ballast.
I don't feel like giving you advice, because you are very prepared, you know your stuff, but I want to tell you my opinion anyway.

First of all, I would choose for the ballast the material that has the highest specific weight but at an affordable price (certainly not gold or platinum). Therefore I would prefer lead, brass, steel, iron, copper, zinc, etc. to concrete.
These materials are not as expensive as gold or platinum but they do have a certain cost it is true.
They certainly cost more than concrete, but you can always get them for free among waste materials.

Even if you have a lot of space available in your huge ship model, I wouldn't waste it unnecessarily. If you have set yourself the goal of reaching a certain ballast weight, it is always better to reach that specific weight while taking up as little space as possible.

For example, if to reach a certain weight you need to have a certain volume of cement, with lead you will get the same result with much less volume and therefore taking up much less space for ballast.

Cement has a density that varies depending on the types of cement (there are more than one hundred types).
The specific weight of cement varies from a minimum of 1400 kg/m3 to a maximum of 3200 kg/m3.
The reference weight that is often used is that of Portland cement 3150 kg/m3.

Now taking into account the case most favorable to you and comparing concrete with lead, for example it turns out that the latter is almost four times heavier.
In other words, with lead instead of cement you will take up a quarter of the space intended for ballast. Using iron or steel you will be about a third of the way there.

Why is it better not to waste space?
All the volume recovered using ballast with the highest specific weight can be used to add or move mechanical or electronic equipment that you want to put on board.
If you already have enough space for every type of electronic device imaginable then fill these spaces with very light, non-impregnable floating material.
If you insert more than 34 dm3 of floating material your ship will be unsinkable.
If I'm not mistaken, our estimates ranged from 32.16 dm3 (Rhinoceros calculation) to 32.2 dm3 (geometric/mathematical calculation). The largest estimate with the prismatic coefficient method gave us 33.8 dm3.
(for those who are interested in this topic but have not understood what we are referring to, they can follow the link at the end of the text).
With 36 dm3 I would feel safe.
Logically, inside your hull (undersides plus topsides) you have much more than 36 dm3 available.
To this you can add the volumes of the superstructures if necessary.

The main question (sorry if you already wrote it and I missed it) is: how much weight do you want to dedicate to the ballast?
Regarding this point, I remind you that oil tankers have a maximum immersion (full load of oil) and a minimum (completely empty).
I wouldn't put all the ballast on immediately but I would keep at least five kg for subsequent adjustments.

The transport and launching of this fantastic model is an operation that must be treated separately and which I will truly enjoy. It's not easy but the more difficult things are, the more interesting they are.
It is certainly an operation that must be done by at least two people.

https://model-boats.com/forum/131081

Hi Jock, I see you are very determined about the choice of concrete and the construction phases.
You have already weighed the pros and cons of using concrete so yours is a wise choice.
The only doubt I have is on the specific weight of 3.16 kg/dm3. It could be different and it could be less. However, since you have decided to proceed with an empirical method (very effective in this case in my opinion): "Once I get to the point of putting my model to water, I will do some testing how much weight I really need" then establish precisely the specific gravity no longer matters.

However, even using concrete (and therefore occupying a much larger volume than a heavy metal) you may still have a lot of space available to create the buoyancy reserve. You only need 34-36 dm3 and I think you could find them anyway.
Since it is very easy to create, it costs nothing and since you want to sail the Esso Deutchland on the ocean, I would seriously think about making it unsinkable.

I invite you to also consider (but you have certainly already done so) batteries as ballast. Don't limit yourself. In such a large RC model you can easily obtain truly exceptional performance in terms of autonomy.
What a great advantage not having to look for light but expensive batteries and instead being able to use heavy and cheap batteries without problems.

Even with the empiric method, it is better to immediately achieve the correct longitudinal trim with the two extreme quarters (bow and stern). In this way the addition of weights in the central quarters will have very little influence on the inclination and you will be able to regulate the sinking with greater serenity.

"I surely let you know once I get there." Of course I'm counting on it, Jock.
As I already told you, your work is one of those that attracts my attention and interest the most. I don't want to spoil too much but I'm curious about the electrical setup. It's not wrong to think about it now.
I hope you will put side lights, fog sirens, fog lights and more.

One question: How will you navigate your tanker, fully loaded, empty or somewhere in between?

When I use ballast I keep it simple. I don't generally use strict calculations as to ballast density, just approximate, so that the ballast is underweight. Then add trim ballast. Do a test run first. Fill some plastic bags with dirt/sand, or ? to see what it takes to trim the boat, then work out the amount of ballast you need. Kind of like using a balance scale to weigh something. Put the item on one side then start adding weights to the other side. Common sense will tell you what to do and what materials to use, depending on what is available, cost and effectiveness.

I add ballast to have the boat float evenly at or slightly above the waterline. This is done in a tub, usually outdoors. when there is no wind blowing.

As a boat will not usually float evenly (fore-aft and/or port-starboard) when completed, several locations for ballast might be warranted. Floating unevenly might be caused by either the details on the boat being not symmetrical or perhaps some off center internal components.

One can use fixed ballast or removable ballast, or both. My preference is usually removable ballast as who knows what changes might be added or removed in the future. For heavier boats both fixed and movable might be a good choice. The movable ballast is usually for trimming and fine tuning.

The most common type of ballast I use is usually non-rusting metal. What kind of ballast material depends on the amount I need and the size of the boat, and of course how much volume is available as well as the shape. Again, here is where common sense into play. We all know that the ballast should be added at the lowest point(s) available. That could define the overall shape of the ballast.

IMPORTANT: For better stability keep the ballast as low as possible.

So, here are some examples:

SMALL BOATS: (Boats generally under ~20".) Here the ballast is usually minimal in amount needed and placed into small spaces. BBs, small ball bearings (balls only), hardware (nuts, washers, etc.).

MEDIUM BOATS (~20-35".) More freedom of ballast locations allow a larger variety of materials. Perhaps a mixture of materials depending on if it is fixed or removable.

LARGE BOATS: (>~35".) Here is where cement (concrete) might come into play as well as other options for inexpensive materials including water itself.

TIPS:
💡 I had a large barge I wanted to trim out to about 100 pounds (45 kg). I brought some empty plastic soda bottles with me and filled them at the pond. Then I placed them inside the barge (photo) along with some bricks after it was in the water.
💡One of the SSMBC members has a "whaleback freighter" and uses a pump to add ballast after launching. Pumps it back out before lifting it out of the water when done.
💡 Coins. Here is the US the common copper penny can be used. Its inexpensive and stacks very well into a tubular shape.
💡 Velcro is a handy way of holding a ballast box in place.
💡 Many times I will make a 3D printed box and fill it with a ballast material and seal it. Often this is attached with Velcro.
💡 Cement (concrete) works just fine. I recommend "casting" it in a container which is the shape you want. Let it cure well (a week?) then paint it with several coats. I used urethane varnish. The best concrete to use is the kind without aggregate (powder only). The better the finish on your casting box is the better the finish on the ballast will be. I personally would not pour the concrete directly into the hull.

Note that these are just suggestions and can vary depending on the type of boat you have. Hope this helps.

Lew
Florida 😎, USA

More than right, Jock.
I look forward to enjoying the developments of ESSO Deutschland.

Hi Jock, I'm very happy that you continued the work on this model.
I love that you updated us on your progress.
This account is very informative.

Hey there Jock! Fantastic hull, I only hope my American Scout can be as smooth!
On styrene I'd give the Krylon Fusion line a shot. Smells to high heaven, but drys hard with a high gloss...will require multiple light coats as opposed to the Rustoleum line of Painter's Touch paints which cover well in one shot.
I am a fan of the Tamiya paints, but not of the Testors spray paints, although they do have decent coverage. It's the least they can do considering the can size.

As per usual, always do test strips and let everything gas out completely. Any gloss clear top coats should be tested on whatever you use to avoid any horrible unforeseen mishaps. Remember, if you think it's dry, it's not.

Hi Jock, I hope it's nothing serious.
Happy recovery and good luck.

GWS Jock🤞
Stiff upper lip old chap😐
😎

Good news Jock! Yet, anything invasive is a big job. Lay low and heal for a bit. It’s good to have that project to jump back into. It’ll aid in recovery; worked for me every time!
👍😉