I have a LEGO ship that I want to photograph as it's sailing along in a pool. Of course the LEGO bricks have cracks in between them so water will leak through.
Does anyone have any ideas as to how to waterproof the hull? Something that won't harm the bricks that can be easily removed. Also I don't want whatever the material is to be visible in a photo.
I would try liquid latex (liquid frisket) which you can buy in most art supply store.
This will not damage the bricks and is easy to peel off. You can apply it using a cheap throwaway brush, either in between the bricks (like a cement wall) or as a thin transparent layer on the whole hull. I recommend the second method because it's fast, straight forward and the easiest one to clean up.
I use this stuff for all kind of painting and molding jobs. It's a great material.
I would tend to suggest another non-waterproofing solution - build something to hold your ship from underneath, that will safely rest on the bottom of your pool.
Of course, if you don't want it to show on the picture, you'll have to be extra careful about how you do it, but I think it's the simpliest solution.
What I would do is buy a large plexiglass sheet (or any other transparent material), make sure your ship is secured to it (drill some 8mm holes in the plexiglass and poke studs in them, or Technic Axles, or whatever). Then you can have someone hold the sheet & ship slightly under water so that the ship looks like it's floating, whereas it's actually not. As long as the borders of the sheet are outside of your camera frame, you're in business.
I owe that idea to a Stargate SG-1 episode I rewatched recently, actually. In the making of, they explaing how they make it look like a bullet is floating in mid-air - they just embed it in a plexiglass sheet and film right through it. It's it's good enough for commercial television, it should work for you too.
Maybe you don't need to waterproof it. If you are able to fit a block of foam (eg. extruded polystyrene) inside the hull, that will probably be enough to ensure buoyancy.
I suspect that water leaking through the hull will not be the real problem you need to solve. Granted, I haven't seen a photo of what you have built, so I might be wrong. I think the real problem you might have is that a Lego boat will be quite a bit less massive than a wooden or steel ship with the same proportions.
If you go look up some of the old sectional boats that they made in the mid 1970s, they all came with lead filled keel piece to keep the otherwise light and rather top heavy Lego boats from capsizing. Depending on your weight distribution, you might need to add some ballast to keep it floating correctly. If you aren't up on your boat physics, just keep the center of mass of the boat as low as possible in the water.
I suggest you give it a 'dry run' (ha-ha, get it?) in your bathtub and make sure that you aren't accidentally going to recreate the closing scene of Titanic before you set up your photo shoot.
Try spraying the inside with plasti dip, it goes on like spray paint or you can use a cheap paint brush, then you can peel off as one whole piece. Best of all it comes in many colors!
Get it here www.plastidip.com they also sell it at most home improvement stores.
Maybe clear contact-paper on the inside?
Put tape around it. Make sure to duble layer it.
You could use cling wrap, or plastic wrap might work. Maybe you could use aluminum foil.
I'd suggest to use clear silicon to seal the underside of the hull then add a weight in the bottom middle to keep balance and also make the ship a bit heavier.
I didn’t try this but it was my best idea.
