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CB italian midget sub : lining up the hull halves

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CB italian midget sub : lining up the hull halves

Postby raalst » Sun Dec 17, 2006 9:16 am

My project this winter (and summer and winter and...)
is a Caproni type CB italian midget submarine.
Why this one ? well, it's cute...
The CB looks like this :
http://www.regiamarina.net/subs/classes/cb/cb_us.htm

there are two left in this world, one in the technical museum of Zagreb
and one in a museum in Trieste.
I plan to visit one of the two, because there is not too much photo's
around on the 'Net.

it is my first scratch build, and it will progress slowly.

I am building from plans by ANB, which proved difficult to obtain.
the link to ANB is http://www.anb-online.org/page_info.php?cPath=2001_1027&products_id=942
but their online shop is not operational.
If you need to contact them in the future, I might be able to help.
their plans are nice.

I had the plans copied and 30% reduced so the model will be about
1m40. It amounts to a scale of 1:14.2.

I sawed the ribs from 1cm thick MDF. I always sawed two plates of MDF
at the same time, giving symmetric ribs for both sides of the boat.
This had to be done this way because you only get one side of the boat
in the drawing.
Image
I bought a motorized saw just for this job. cutting about 64 ribs
by hand is not my idea of a hobby.
Image

both ribs were then positioned using a 1cm MDF "side view".
I glued copies of the plan to the MDF and cut out the profile.
Image

The ribs were spaced and held by M5 threaded rod. So I had the
profile, and the left and right set of ribs.
Then I drilled holes thru the profile, just aboove and below where
the rods are, and tied the halves together with tiewraps, clamping the
side view profile inbetween. The rod was just flexible enough to align
the ribs with some precision.
Image

I used polyurethane foam to fill up the spaces and make a solid
plug. polyurethane foam is polyester resistant, and I did not have to
find foam plates of the proper thickness.
I tried on a test-rig first.
Image
It turned out quite nice, but the foam had bent the ribs about a
millimeter outwards.
Image
the foam remains rather soft, but I plan to apply a hard shell
by means of polyurethane yacht varnish.

when foaming the plug, I made sure to
foam the outer ribs first, and work towards the middle ribs
It's impressive stuff, that foam. I made a makeshift
dam to keep the foam where I needed it.
Image

then some crude sawing, cutting and coarse sanding, and it came out
like this :
Image

using a third bottle of foam, after filling the remaining gaps
the current result is
Image
A nice side-effect of the foam is that it also glues the ribs to the profile.

Next steps are filing and sanding the MDF ribs exact,
then plastering, then varnish, then plastering with polyester.
after that the scary stuff begins (i.e. moldmaking).
Last edited by raalst on Wed Jul 01, 2009 5:15 pm, edited 20 times in total.
Regards,

Ronald van Aalst

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Postby Sub culture » Sun Dec 17, 2006 10:04 am

One tip I'd suggest is covering the master with a layer of fibreglass matt and resin. Polyester filler isn't very flexible or strong and dents easily.

A layer of glass and resin will make the plug very strong indeed.

Andy
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Postby Bigdave » Sun Dec 17, 2006 11:59 am

A good friend of mine is building the same sub. I always call it the TOON sub. As it looks like it was designed by the Tiny Toons! It's so cute!! BD. :D
David Welch
Commodore SR-8

Image


"Eat your pudding Mr Land". "I ain't sure it's puddin" James Mason-Kirk
Douglas, 20K
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Postby raalst » Sun Dec 17, 2006 12:26 pm

@bigdave

I think I know your friend. He helped me obtain the ANB plans.

BTW, my contact in Italy informed me that
the ANB plans can now be ordered via the italian
business called MagicModel,
www.magicmodel-online.it
info (at) magicmodel-online.it

This shop is run by the secretary of the ANB, or so I understand.

I have the postal details if required.
Last edited by raalst on Wed Dec 20, 2006 9:02 am, edited 1 time in total.
Regards,

Ronald van Aalst

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Postby Bigdave » Mon Dec 18, 2006 8:22 pm

Hi Ronald,
Yes we do indeed have the same friend. Best of luck on your project! That is such a cool and unusual boat. BD.
David Welch
Commodore SR-8

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"Eat your pudding Mr Land". "I ain't sure it's puddin" James Mason-Kirk
Douglas, 20K
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Postby JWLaRue » Mon Dec 18, 2006 9:44 pm

Maybe this will encourage our mutual friend to get more progress done with his. :)

He's been talking about it for several years now!

-Jeff
Rohr 1.....Los!
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Postby PaulC » Sat Dec 23, 2006 1:33 pm

Jeff,

What is "our mutual friends" current email address? I wanted to drop him a note regarding the article on his boat in the latest SCR.
Warm regards,

Paul Crozier
<><
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Postby JWLaRue » Sat Dec 23, 2006 2:59 pm

Hi Paul,

E-mail inbound.......

-Jeff
Rohr 1.....Los!
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Postby colin-stevens » Sat Dec 23, 2006 4:57 pm

looks like a real beut, may look into it myself.
keep up the good work
colin
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Postby raalst » Thu Dec 28, 2006 5:20 pm

the plug is now covered with gypsum (plastercast ?).

Image

the gypsum will enable me to smooth the surface to a degree.
the lower part is already sanded, now the upper part must be
sanded.
After that, some polyester coating will be applied and then the
finer smoothing starts.

I practiced my first glassing today on another project. seems
not to involve rocket science. Might be beginners luck though
:shock:
Regards,

Ronald van Aalst

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Postby raalst » Sun Dec 31, 2006 7:45 am

today the tower was shaped.

I love polyurethaanfoam :D

base shape.

Image

nothing is level...

Image
Image

the plastic strip is a nice indicator of where to sand.

Image
Image[/img]
Regards,

Ronald van Aalst

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Postby Sub culture » Sun Dec 31, 2006 8:01 am

Going well.

You're doing things in the reverse order to my way of working though.

I skin the foam with glass and resin, then use polyester filler and glazing putty for the final finish. I don't like using plaster- tried it before and found it lacking in strength, plus it takes a while to fully harden off.

However you're method will work, but I'd skin it with resin and glass at the nearest opportunity, as the finish will be very vulnerable up until that point.

Andy
'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Postby raalst » Sun Dec 31, 2006 8:17 am

Andy,

that is the plan. especially after reading Mylo's story.

the trade off I made is that I rather work with non-toxic
stuff.

After the next sanding I will glass the hull and continue with
polyester filler.
That also means I am banned to the (unheated) shed, as I cannot
safely sand polyester filler inhouse.

The plaster hopefully makes that there is not too much polyester filling
to be done.
Regards,

Ronald van Aalst

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Postby raalst » Fri Jan 05, 2007 5:43 pm

applying the polyester went wrong on the first side I glassed.

http://s181686668.onlinehome.us/phpBB2/viewtopic.php5?t=5595

let's see how the other side will come out...
Regards,

Ronald van Aalst

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Postby U812 » Sat Jan 06, 2007 11:59 pm

I really like your choice of subject matter here Raalst. Nice to see you scratch build. I will be watching.

Keep going!

steve
U812
 

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