CB italian midget sub : lining up the hull halves

[raalst]

The casing for the first

The casing for the first half of the mold is ready.
I also sealed the gap between boat and board with
paraffin wax.



after the silicone rubber layer I will apply a layer of plaster,
and then the rest of the casing is filled with PU foam.
This will be leveled to the top of the casing, and the casing sealed with
another board. Then the whole is put upside down, and I should have
a mold half in a box with a fixed plaster interior, and a
removable silicone rubber inner mold

[raalst]

the first layer of rubber

the first layer of rubber has been applied. finally...

Does anybody have a good tip (from his/her *own* experience)
for a filler material in the silicone rubber ?
a filler material means more volume for less bucks, hopefully.

[anonymous]

Not really and filler can

Not really and filler can make the RTV weak. Generally I brush layers on. Up to about 3/16 of an inch thick making sure I keep the out side of the RTV as smooth as possible. Once you make your mother mold it will be well supported. If it's a good RTV that's all the thickness you'll need. Anymore is a waste. Just take your time. The mold is everything.

Steve

P.S. If you plam to use plaster be careful. It is a weak and heavy material. Back it up with burlap. first do a splash layer. Then follow up with burlap and plaster. Another coat with just plaster. Lighter and stronger. Best is to make an epoxy glass mother mold if you can.

[raalst]

Thanks for the tips !

Thanks for the tips !
I *will* reinforce the plaster shell.

I agree epoxy is lighter/stronger but I am a bit scared about
- exact ratio's of stuff and catalyst required
- toxicity
And polyester might shrink/warp too much and distort the
RTV mold.

[anonymous]

You bet Ronald. Like I

You bet Ronald. Like I said. Take your time. You put a lot of good work into that hull and you don't see a model of this subject everyday!

Best of luck,

Steve

[raalst]

here is a picture of

here is a picture of the second layer of silicone rubber.
Note I colored the second layer so I could see what was
covered and what was not.
third layer will be white again.

[Guest]

A polyester resin hardcase will

A polyester resin hardcase will work okay. Shrinkage is negligable- if it was that bad, you wouldn't be able to cast a hull from it (think about it)

Andy

[raalst]

I'm considering GRP.
(Glass Reinforced Plaster)

I'm considering GRP.
(Glass Reinforced Plaster)

[paul]

Your sub is looking great.

Your sub is looking great. Can't wait to see it finished.

[raalst]

Thanks Paul ! Me too...

almost

Thanks Paul ! Me too...

almost finished with the silicone for the first half now...
Even having two hull halves per the 18th of May seems ambitious now.
(18th is our local dutch yearly sub event)

[raalst]

Next Phase ! plaster time

Next Phase ! plaster time ahead.

as you can see the silicone is rather lumpy, this is because I re-used
small shreds of old cured RTV in the middle layers. Because of
this, I think I can leave the registration bumps out of it.

I must confess 2 cockups :

*always* plan before you drill a hole


*always* plan before you saw a hole in a plank. The little built-up
of the boat is now crammed into a cut-out recess in the planking.
Otherwise the plank could not be attached full-length to the board..


My late grandfather would have been disappointed. He teached me
woodworking far better than this...

[raalst]

plaster is being applied. I

plaster is being applied. I found a synthetic wool sold in pet shops
(it is called filter wool and intended for aquariums) and used that
as "rebar" for the plaster instead of burlap.

first impressions about it are good. but of course all shall be revealed
then the box is turned and the original removed.

[raalst]

Compared to this, the egyptian

Compared to this, the egyptian kings sleep their eternal sleep in
cardboard boxes



btw, what is this metal wire stuff called in english ? over here it is
called kippengaas (hen's mesh)...

[pirate]

Ron,

We call it chicken wire.

Ron,

We call it chicken wire. But won't it rust in the plaster, therefore negating any structural integrity?

As Steve said, burlap or hemp is traditionally used here in the plaster.

Pete

[raalst]

Hi pete,

no, the chicken

Hi pete,

no, the chicken wire is galvanized and the plaster is only
wet for a short while.
I had no burlap or hemp around (smoked it all ).