another way to shape a master

[raalst]

I am scratchbuilding a submarine and came across the following tip,
which was already used in anger by a few of my fellow modellers in
the SubComNL.

The normal way to make a master form is to cut out ribs and fill the
space between the ribs with some foam plates. you can see a splendid
example of this construction method at mylo's building thread

http://s181686668.onlinehome.us/phpBB2/viewtopic.php5?t=5376

With me, the scaled down version of the drawings gave a space between ribs
that will not ever be produced.

So, I used a bottle of sprayable urethane foam (called PUR over here).
It is often used in construction, as a glue and as a filler. (H*ck, half my
house would not be standing if not for that foam. What happened to
wood and nails and craftmanship ?)

The beauty of this is that it glues together your frame and it will fill
any size of space.

I just made a test-setup of two ribs of 1cm MDF, spaced apart with an
M5 threaded rod. Then, to counter the foam's expansion (and thus to
get smaller air pockets) I wrapped it with cling-wrap household foil.
This foil does not stick to urethane, nor to polyester.

then I stuck the nozzle of the spray can thru the cling-wrap and presto ]http://home.vianetworks.nl/~raalst/cb/proef2.jpg[/img]

after hardening and sanding, it looks like this ]http://home.vianetworks.nl/~raalst/cb/fillspant.jpg[/img]

urethane is polyester resistant, but I intend to apply a layer of car filler
to be able to sand the whole thing smooth(-er than the ribs are currently)

Ps building thread will follow later.

[Guest]

I'll add a further piece

I'll add a further piece of advice- before applying polyester filler apply a piece or two of chooped strand matt and resin. This will skin the master with a tough surface that resists any handling damage.

Then just fill as normal.

Andy