Cartoon scale working paper model of S503 Pietro Calvi

[zhuravlik]

Hello Lads,

It's a pleasure to start a thread in this wonderful forum!

I'm building this model to test some ideas i've had during the working season. I am the service man of a fleet of sailing yachts and work at La Spezia from may to november.
With this model I would like to test the appearance and dynamic properties of a cartoonized sub, strenght of an epoxy impregnated cardstock outer hull, micro piston tank and magnetic actuator for rudder control.
R/C guts are from graupner shark, a small 3 ch sub. All the commands are bang/bang.
I've started a couple of weeks with the micro piston tank ago fiddlin with some micro gearboxes to make the piston tank. Used one from chariot bit chargers from micro plane early days: http://www.rcgroups.com/forums/showt...=302756&page=4
I finally had some success but i still must build an oring piston in lieu of the original 10cc syringe piston and build the microswitch and diode circuit.
Next came the wtc wich is just a 13cm lenght of electric plumbing 3cm tube and a nylon cap. Here will sit rx, battery and piston tank while a reduced 6mm motor and magnetic actuator will stay outside.
Yesterday I ve built the outer hull using a very basic plan, few photos and cone designer program. Used some 200g/sqm black cardboard and loctite to butt joint all the pieces togheter using some card tongues to reinforce joints

[trout]

Very nice! I am intrigued by your piston. Can you tell me more about that? Where did you get the gearing?
Looking forward to your completed build!
Peace,
Tom

[zhuravlik]

Trout, I followed your Aluminaut thread with greatest interest. I loved your system, hacking an electric retract was pure genius, but i was unwilling to order and gut them so started to tinker with what was around. Then eye fell on this little chariot car gearbox. I ve punched an esagonal hole in the biggest gear to house the driver nut and filed flat a short lenght of 2mm threaded rod. then just added the piston and a base for connecting the gearbox and the syringe. I just copied from graupner u-16 as you can see from the photos:

http://www.rcuniverse.com/forum/rc-submarines-119/7549119-graupner-u-16-a.html#post7594072

[Subculture]

Nice work.

I think you may well find the cardboard will suffer over time, even if well coated in epoxy resin. It only requires a pinhole for the water to wick in, and cardboard is about the worst material when it comes to water resistance.

Looks to me like you've done the hard part in making the master, so how about going one stage further, pull a split tool from it and mould the hull.

[zhuravlik]

Subculture, thanks for nice words.
About that pesky cardboard I think you are right: epoxy didn't exactly saturated it despite being warm. But my little 1/350 tug is holding up very well despite being 3 years old:http://www.rcgroups.com/forums/showp...6&postcount=41
Anyway the hull pieces are in the sink to be tested, i hope to find them crispy and dry. If not, I was thinking to do the hull lost foam style, could be done with hotwired styro sections on a removable alignment skewer... Mmmh.

[zhuravlik]

Disaster!
Indeed I've been very naive to think it could work... As you can imagine soft spots everywere and delams too.
So back to the drawing board. I think I'll use lost foam method, despite remembering that building my little Alfa was a friggin putty Bedlam!

[He Who Shall Not Be Named]

Disaster!
Indeed I've been very naive to think it could work... As you can imagine soft spots everywere and delams too.
So back to the drawing board. I think I'll use lost foam method, despite remembering that building my little Alfa was a friggin putty Bedlam!

I've learned over time that Andy, when he says something, is usually right.

Get back on the horse and try again, zhuravlik!

M

[Subculture]

If you really don't fancy laminating a hull, as you made the original from sheet material, how about trying to make it from thin plastic sheet, or better still thin epoxy glass sheet (G10) which you can get in very thin thickness's e.g. 0.25mm. It'll be close to indestructible if you make it from that, and glue it together with a good epoxy like JB weld.
Plastic or composite sheet will be more springy than cardboard, but you can hold the sections together using soft wire and effectively stitch it together. once set, snip the stitches off and fill in the holes with more glue. That's a very old fashioned method of construction, but it works.

Another possibility is thin tinplate, which could be soldered together or glued with epoxy or better still modified acrylic glue. However watch the top weight.

[zhuravlik]

The current plan is to sleep a bit and start to rig the hotwire gizmos and get the work done.

I've tinkered a lot about other sheet material to use and decided for cardboard because plasticard and g10 are indeed too springy and metal would mean an external antenna. Heck, gummed paper hulls are mentioned in Vic Smeed's Model Boat Designs! Probably a dry impregnated glass sheet would work.. But again, every submarine needs a bunch of holes and scribings that you are going to need a strong, coherent base material and fiberglass is just perfect for this.

[redboat219]

Didn't you build a 1/200 Alfa using lost foam technique? http://www.rcgroups.com/forums/showthread.php?t=1418432

[Subculture]

You can get away with lot more on a surface boat, as it doesn't have to deal with water pressure like a sub. I've seen one or two model subs in the past built from wood, and they always end up with problems, and tend to either end up being retired as working models, or used as a buck to pull a glassfibre tool from.

Gummed paper was a good technique back in the days when room temperature curing resins were still pretty new technology and probably costly or difficult to obtain for the average modelmaker.

With the materials available to us these days, there's no reason for going for second best unless you are extremely strapped for cash.

[zhuravlik]

Yes Romel, you remember correctly. Building Alfa hull was a mess but came out pretty well.
With this under my belt i feel confident to try with much complex shapes.
The paper hull will be completed and used as a reference. It was built incredibly fast, 3 hours from start to finish and for sure did help to nail shapes down. For example i realized that deck is far too wide.

[zhuravlik]

Here is some progress: bow and stern were hand carved using a couple of formers, new narrow deck, some sandpaper and eyeball mkI.
Central section was rough-hewn with hotwire and chuked on lathe to be refined. Central deck will be made withthree pieces of depron to get the slot right and symmetrical

[zhuravlik]

Been another busy night: laminated three layers of 100g/sqm glass over the hullform and now it's almost ready for stern cut and foam removal.
I'd like to sharpen deck edges, will probably use some epoxy resin with a pugillus of tixo and a sprinkle of glass schnitzel. Or could use some kind of epoxy putty..
Any ideas?
Decided to vacuum form the sail for max lightness. On the opposite, keel wil be cast lead.
I'm thinking about opening bow and stern limber holes and scribing a few details on deck ; the issue here is scarce documentation but something can be done.
Bought some orings to complete WTC cap and piston. I will now focus on innards as I have now all the pieces together.
I have to apologize for attached photo's quality: they does not deserve to be on this forum.
Here is a better photo of the hull as it is currently.

[He Who Shall Not Be Named]

Been another busy night: laminated three layers of 100g/sqm glass over the hullform and now it's almost ready for stern cut and foam removal.
I'd like to sharpen deck edges, will probably use some epoxy resin with a pugillus of tixo and a sprinkle of glass schnitzel. Or could use some kind of epoxy putty..
Any ideas?
Decided to vacuum form the sail for max lightness. On the opposite, keel wil be cast lead.
I'm thinking about opening bow and stern limber holes and scribing a few details on deck ; the issue here is scarce documentation but something can be done.
Bought some orings to complete WTC cap and piston. I will now focus on innards as I have now all the pieces together.
I have to apologize for attached photo's quality: they does not deserve to be on this forum.
Here is a better photo of the hull as it is currently.

Now, that is quick, good work!

M