How to Make a Smooth Hull

[rgmarine]

I've always been disappointed in the way hull sides have turned out whenthere is no support behind the hull skins. It seems that no matter how carefulI try to be you can still see ripples in the sides of the hull. If thesedefects were scaled up to full size, I think the ship owners would be demandingtheir money back from the builders.

So, at the scale that we work on in paper models the hulls should appearperfectly smooth with no warps or wrinkles. To accomplish this requires some support behind the hull skins. There are many ways to do this: florist foampieces, balsa pieces, Styrofoam pieces etc.., all squeezed between frames andsmoothed to frame lines. Here is anotherway that I'm trying as an experiment. This is not my idea - I got it from Hiob at Paper Modelers where he usedthis technique to build a 1:200 Kursk model that is nearly five feet long. This process lookedinteresting so I decided to try it.

Photo5

I had a model of a Polish destroyer in progress so this would be my guineapig. One thing that I always do is tocolor the edges of my hull stiffeners with black magic markers. After coloring, I soak the edges with superglue which when cured gives a hard workable surface. And when you are sanding down a softer fillerbetween frames, the black shows through when you reach the frame and the hardersuper glue surface prevents you from sanding away too much from the frames.

Photo 6 and 7
The expandable foam is the same stuff you can buy in the hardwarestore to seal wall cracks and stop air leak and it comes in a spray cans. Using Hilti expandable foam in a can, Ifilled in the spaces between frames and allowed the foamed skeleton to cure for24 hours. It ain't pretty and this stuff is hard to work with in an open space.It is sticky and gets all over everything. My wife said it looked more like a dessert than a ship. I thought itlooked like something more disgusting especially if it was painted brown. Shesaid "How can you make a ship out of that mess?" I replied "It's simple. I'll just cutaway everything that doesn't look like a ship." So next I'll hack away at the foam and seewhat we end up with.

 

[rgmarine]

How to Make a Smooth Hull 2

Carving away the foam was surprisingly easy. I used a serrated butcher knife to do the rough trim and then used a serrated steak knife to do the final trimming. One issueis that the foam looked more like Swiss cheese (see photo 8 and 9) so I filled in the worst holes with another shot of foam and did a final trim as in photo10. The foam, when cured ,can be cut and sanded easily and as seen in photo 10 where you can see why I edged the frames with black to make them stand out when sanded.
Photo 11
I would have liked to have a more substantial surface to attach the decks and skins so I put on a coat of vinyl spackling compound with a putty knife. This took care of the irregular bubbles left over from the foam.
Photo 12
The spackling compound sands very easily and it only took a few minutes to bring the surface down even with the frames. Next step is to spray on a couple coats of dark grey primer to seal the surface in preparation for skinning.

Photo 13
Decks went on with no problems as seen in Photo 13 and then I continued skinning the hull. In retrospect this method is probably no better or faster than putting balsa or florists foam between the frames but it was an interesting experiment.

 

[Paperbender]

Thanx, you are a good teacher. I'll have to give it a try.


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[Revell-Fan]

That's good! I've seen this technique when model builders make solid forms for vacuum forming.

 

[silveroxide]

I have not tried the spray foam yet, but it looks a bit messy. I still like to use the styrofoam from shipping boxes best and the mess is cut down a little but it is still a mess of chips and bits on the working area. I may give it a try when I get to do another ship.