Carving or moding foam?

Anyone here experienced with carving or moding foam. I am building a model ship for my grandson and finding the contours on the hull too dificult to form with wood. I haven’t tried balsa yet, I may try that before I use the foam.

I’ve carved foam and fiberglassed it for set pieces; what do you need to know?

Need to know the best kind of foam to buy and if it is a moldable or just carvable type? I could get by with either one but would prefer something I coud mold rughy into shape before finishing.

Ah, okay; sorry but I’m prolly not going to be able to be much help. We just use blocks of styrofoam, carve it with a hot knife and/or a bow knife and then glass it.

For what you’re doing, I’m not even sure if EPS or XPS foam would be better (I’m gonna guess XPS, tho).

ETA: How large (or small) is this model going to be?

Quite a few model railroaders have been using a pink EPS foam that Dow sells. It is normally used for insulation and can be hard to find in temperate climes (i.e. California) but you might check. It is denser than the usual coffee cup style packing foam that electronics and so on come packed in. The model rails use it for scenery contours and say it carves easily but produces a lot of static dust.

I can’t imagine a foam that can be formed into any kind of small. intricate shape - as mentioned, it is great for rocks and trees - as long as the audience is 100 feet away.

Shaping a hull less than 5’ long is not going to be realistic - in either execution or result.

How big is the model and how old is the kid? At some age, a matchstick in an eraser will pass as a boat in the bathtub. That is easy to do with foam.

A credible HMS Titanic is much less likely.

The actual model is 34" long, Not looking for collectible quality but would like evry nice toy quality for lack of a better description. It is an older container ship 662 feet long. If I cut my wood in 1/4" strips I think I could follow the contours fairy well. I have ribs every 2" or less cut to the contour of the boat, I just need to connect them. This is a smooth sided metal vessel though so I though foam and fiberglass might be a better option.

You might be able to carve the hull out of foam.
You may be able to apply a very tightly woven glass over it and then fill the imperfections with a slurry to get a smooth surface.
The deck and everything above it will need to be built and then fitted into the hull.

Folks have built airplanes using foam and glass. It is NOT quick NOR easy - and the stink is something else.

Sites catering to model builders sell thin strips of wood for this very use - to model hull planking.

I’d look real long at that before I’d try foam and glass.

Balsa is stronger, easy to work with standard tools. XPS is best for foam since it’s not a bunch of beads stuck together. Foam cuts clean on a band saw, it can be sanded pretty smooth. Balsa cuts cleaner with all sorts of tools. Both foam and balsa can be cut down rapidly with disk, belt, and drum sanders. The big disadvantage of foam is that dissolves easily in all sorts of glues. You need to use simple white glue or epoxy with it (although you can stick pieces together with a light spray of Super77 or just acetone). For a boat model I’d use balsa if possible just because it will be easier to keep modifying the model, drilling, cutting, attaching other after you finish the basic shape.

I carved a model of a dam for their visitor center out of high density floral foam and covered it with gel coat. Didn’t use any glass fiber. I was able to get some pretty good detail.

Anyone want to carve a six-foot-tall moai and send it to me? :smiley:

I would consider asking Rocketeer for some input. He may be our resident model building expert.