Well - I finally pulled the old F-48 foam plugs out of storage and am back to working on them this coming winter. Health permitting of course. Today I decided that I am going to have hollow glass hulls, so have turned my foam shaped hulls into “plugs” over which I will lay-up epoxy and glass. 1 layer of 4 oz. glass and an exterior of 1/2 or 3/4 oz. is planned. Perhaps will add a bit more 4 oz. inside where beams fasten or dagger board trunk is located for additional strength. I am using plastic packaging tape as mold release once glassed hulls are cured. Photo 1 is the foam half hull and the other half hull covered with packaging tape. The other two are the tape coverd foam hull with layer of 4 oz. glass applied. Note how transparent glass gets - easy to spot any voids or dry spots.
More photos as I move forward.
Looks good! Just a couple questions. Will the overlap on the packaging tape cause corresponding ridges to “print through” onto the finished surface? Could a mold release film be used instead?
Mold release film might be worth a try, but I guess you would have to treat the foam surface before applying to seal the holes/bubbles of the foam.
Good to see, that you recovered so far, Dick. All the best on your way back to normal.
Bill - yes, the tape will leave very fine lines on the inside of the glass where the edges of the tape overlap. Not a big problem and very easy to simply sand down if you are thinking of using the glass layup as a mold.
You will need to seal the foam before using any kind of mold release, as it is really water-thin. I think by the time you compare the two, if it is easy to get at the inside of the glass lay-up, you will find the packing tape by far faster. If you consider having to smooth the foam, then seal it, then sand, smooth and polish it before applying the PVA or mold release, you will have a ton of time invested. But this is a good thing if you have a lot of parts to make. If you are only doing one off, the time to fill and fair and sand is about the same. If you have maybe 1/2 dozen or so to make, it might be faster to use the tape, and then sand and finish the parts from the layup as yo are working on the exterior of the part. Finally if you are looking at production - say mabe more than 5-6, I would probably use a regular mold build-up.
To me, the biggest problem is getting smooth and polished surfaces on the “inside” of the mold. I find working on the exterior of the hull much easier and faster to do.
Just keep in mind, the lines where the tape overlaps will be no thicker than the tape being used. If you have ever had a problem with Scotch Tap on packages or stuck to a smooth surface, you know how hard it can be to find and lift the corner of the tape. My guess that some coarse sanding paper leaves deeper scratches than the thickness of the tape.