Mick,
Admhawk has a good point. Your model is so large that you must take thermal expansion into consideration. In direct summer sunlight it will absorb nearly 1 kilowatt of solar energy per square meter - that is about the amount of energy a toaster uses. Imagine four toasters runing continuously inside the ship - it is going to get very hot. There are three problems you must deal with.
1. First, the deck itself will expand and contract. Here is a link to a site that lists linear coefficients of thermal expansion for several plastics:
http://www.edl-inc.com/Plastic%20expansion%20rates.htmIf the 4 meter long deck deck is made of acrylic and it heats up 10 degrees Celsius the deck will lengthen 2.7 mm, or about 1/10 inch! The deck could easily heat twice that much on a hot day. Ouch!
(acrylic = 0.000068cm/degree C x 400 cm x 10 degrees C = 0.272 cm)
This is about four times as much expansion as an equivalent length of aluminum.
Glass reinforced with epoxy or polyester will expand much less. If it is the same material as the hull it will expand and contract about the same for a given temperature difference. Wood will expand even less. Use adhesives that can take the heat!
Whatever supports you build for the deck should be of the same material as the deck itself. Short detail parts can be of something else because they won't expand much, but any long major support members should be the same material. If not, they will expand at a different rate and the bonds between materials will break, or the deck will warp.
I speak from experience. I reinforced a 1:96 fiberglass hull with plexiglass pieces, and glued it with epoxy. I set it out in the sun to dry after painting and the plexiglass parts expanded faster than the fiberglass. Fortunately, the epoxy melted and the plexiglass parts just poped up out of the hull. It was easily fixed but I learned the lesson about thermal expansion!
2. The deck will expand/contract more than the hull because a) the deck absorbs more solar energy and b) the hull is water cooled. This will be especially true if the deck is painted a darker color than the hull. If you attach the deck to the hull rigidly something will have to give, and the results will not be nice. You can attach it firmly at one point, but all other points should be fitted with slip joints to allow expansion.
3. You should give some thought to ventilation of the hull to avoid frying the electronics. Electronic devices generate internal heat, and they need to lose this heat. Equipment is typically specified to operate over some ambient temperature range (although some hobby equipment doesn't list this spec). If this is exceeded the solid state components will go into thermal runaway (the hotter it gets the hotter it gets) and melt. A lot of new equipment has thermal shutdown protection, but the model will be left dead in the water if this happens. In any case, during trial runs keep a thermometer in the hull to see how hot it is getting.
For a rule of thumb, if you don't know the thermal specs of the equipment keep the ambient temperature below 45C (113F).
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Keep us informed of your progress. You are entering territory most modelers never have to deal with.
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