Different, but related

I'm thinking of building a large, R/C model battleship. It would be ~16' L, ~3' W, & ~1.5' H.
6mm Meranti marine plywood is being considered. Would a traditional wood frame be necessary, or would S&G suffice? If framed, how does one glass-over those frame members, or more generally, is glassing the interior necessary at all? If framed, what wood would be recommendable and what spacing between the frame members(ribs)?
Next, is resin consideration. Of course epoxy is superior, but being that I'm not paddling, sailing, or powering myself in the vessel, would a good lay-up with polyester resin(to save $$$) work?
Thanks.

 

If you are going to have a faithful scale reproduction of a real battleship, ply sheets won't be much use, as they were round bilged affairs, and the ply won't conform to the shape, but if you only care what it looks like when in the water floating, that detail will be out of sight.

 

Actually, the plans I have show a flat-bottomed hull. My real concern would be the compound curves and shape of the stern.

 

The bottom is flat, but the "real" thing is round where the sides meet the bottom. If you are only concerned about the floating appearance, "cheat" with a chine !

 

You can always use laminated veneers to get the shape, had a friend who used to make super light rowing sculls that way.

 

6mm ply would make for a heavy model. Even kayaks that length use 4mm, and they get a lot more knocking around.
Stitch and glue is plenty, with a few frames.

For the compound stern, build the stern square, put some expanding foam on it, and carve to shape. There would be a good case for drilling out some of the foam later to increase lightness

PS - use epoxy. Poly is fractionally cheaper, but there are plenty of cheap epoxies that will do the trick, and make a longer lasting, least problematic build. Also, you could then skip epoxying the interior with fewer problems.

 

If the inside of the boat is not an issue, you might consider building the model with a combination of materials. 2" pink polystyrene, for example, is relatively inexpensive and can be modeled into fair curves with knives and heavy sandpapers, i.e. the stern. It takes epoxy well and I did it for a pair of canoe outriggers once, but rather difficult to get looking nice without fairing - no delam in like 10 years with epoxy. If you used a traditional planking method, you could use thinner polystyrene, like 1/2", and make most of the curves over frames without much trouble and still be able to fair it a bit to make radiuses for any glass work if you plan to glass it with some light stuff. Cheap enough to test it out as well, right? Otherwise, if you use 4mm plywood as rwatson suggests, you could try stitch and glue if there is no compounding of the curves. There was some other polystyrene I bought years ago that was even thinner than 1/2". It is called fanfold. I might try that as well for the hull sides. I think it costs like 30 bucks for an entire package of it and that'd be enough for your hull sides or other parts of the model where you need to carve and need some rigidity. For example, you could use fanfold to build a pilothouse or gun station and carve details into it. I can't recall if it hotglues, but a hotglue gun is a must for this type of modeling. Any bonds of hullsides to frame take a minute versus a day for epoxy to cure.

 

The hull of the boat is not likely to be the heaviest part of the structure. In modeling a battleship, you will have an impressive amount of detailed structural parts above the main deck. You may even need to use some ballast, depending on how heavy and how high above the main deck those items are. All that superstructure will also be subject to wind influence, and the sea state will have some influence. It is likely that you will "sail" the boat in calm weather so sea state may not be a major factor.

Not to be a naysayer here. You can certainly build a model of that description that is capable of performing well. The propulsion mechanism, motors, batteries, control elements, Rx, and such will serve as ballast elements. Whether enough or not can be determined experimentally. Several of our forum members are capable of doing the stability and performance calculation but the job would be tedious, time consuming, and expensive. That is why I say experimentally. Go for it.

Best of luck with the project. Sounds like great fun to me.

 

The fellow is right about the boat getting heavy on top. A flat bottom hull is not a friend for such. At 16' long and 3' wide, a vision of a deck heavy canoe comes to mind. Those can be tippy.

I might be inclined to use a different hull shape if it hasn't been done before.

 

Personally, I think its a non-worry. For a start, there is NOTHING as stable as a flat bottom craft.
I have a virtually flat bottom Canadian canoe of similar dimension, and it can safely cope with 3 x 100 + kilo adults, sitting on seats level with the gunnel.

If you stick batteries and motors in the bottom, with a jerrycan or two of water ( permanent ballast is too heavy to cart around), it will be able to support a large amount of superstructure - which most likely will just be foam, fiberglass and a bit of timber.

 

I suppose if you ballast it and don't get too topheavy; it'd be okay. Funny you speak about a flat bottom canoe. I, too, have a Gil Gilpatrick designed Laker, flat bottomed boat. I tried to flip it and so far have been unable. Even still, I did build outriggers for it for dangerously hypothermic water. I did consider it when I made my point, but wasn't sure how high he was going to build the super. Probably not any higher than I sit. Correction accepted.