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Dec 05, 2011, 02:30 PM
Boaters are nice people.
Thread OP
Build Log

Motoscafo Anti Sommergibile.


This is the story of my semi scale build of the M.A.S. sofar.

I bought the plan some 15 years ago; I had no experience with building plank on frame, so I figured a square box with a pointy end wouldn't be too difficult to start with...

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Description: The plan.

One time, being home, recovering from the flu, I made a 75 cm version out of thick cardboard (SWMBO wouldn't let me in the shed, and sawdust in the living was a no-no), glued together with hotmelt.
This worked rather well and I covered the model with molten candle wax, so I could cover it in glasscloth and polyester without sticking it onto the cardboard.

I did the laminating at work, where I had a workplace suitable for this messy and smelly job and the right tools.
As I used the leftovers from the production, the glass was rather coarse and the resulting hull build like a tank...
Once the polyester had fully cured, I used a lot of heat to make the hull hot enough so the wax would melt again and I could get the cardboard hull out (the cardboard hull didn't survive, as the hotmelt also got weak...)

Cleaning the inside from the remainder of the wax was quite a challenge, as was smoothing out the outside by sanding and adding additional coats of polyester resin.

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The picture shows my attempts to add a strip of wood, where the deck would have been attached to, but the weight of the hull didn't allow for more extra weight than a lightweight deck, so I never finished this hull and only used it as a testbed for various motors, from a geared down 05 car motor to a 900 size, turning a 45X prop, cellcounts from 7 - 12 NiMH.

You can see I abandoned the two motor original for the more efficient single shaft/big motor & prop set-up.

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Having goofed around with it in the local marina, the hull proved very fast on 12 cells and very nimble on 7 cells, but too heavy to carry a deck and superstructure without looking as if it was on the edge of sinking...

Together with my son, who started in the hobby around that time, running my boats, lacking one of his own, we started out building two of these boats, slightly bigger to avoid weight issues.

My son was 13 at the time and the picture shows his build at the present state:
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After he'd gotten this far, running FE got his attention and pretty soon the both of us were racing our boats in the National competition.
Needless to say that building and maintaining a fleet of FE boats and battery-packs took a lot of time, which took it's toll on the M.A.S. build.

I kept working on mine every now and then and eventually the hull was sheeted but for the bow section.
The transom was easy:

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The rest wasn't too difficult either, until I got at the front, like today, I than was even more a budget builder, so I used the lightest and cheapest ply I could find; 3,2 mm poplar ply from the local building mart.

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The 3,2 mm ply was not just very soft surfaced, but also very reluctant to bend around the bow section, so I had to work around that:

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The sheets and stringers ended at the first former and I used 6 mm ply to extend the lines of the stringers, giving a hold for the strips of poplar ply, which were sanded to fit snugly next to each other, forming the curvature of the bow section.

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The top view shows, my accuracy on the curve wasn't too good at the time.
I left holes, so the interior could be waterproofed with epoxy once the bow was closed.

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In this shape, the hull sat on the shelf for a number of years before I had time to work on it again, between moving to another house and racing six sundays a year.

Regards, Jan.
Last edited by pompebled; Oct 18, 2015 at 07:50 AM. Reason: Addition.
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Dec 05, 2011, 03:24 PM
Boaters are nice people.
Thread OP
The announcment of the 1/35 M.A.S. by Italeri got my 'sleeping beauty' awake; the bowsection was finished and glassing was next.

As I had changed jobs and working with polyester had made me allergic to the stuff, I chose glasscloth and epoxy, far less smelly and it didn't trigger an allergic reaction.

I started with glassing the transom and the steps, once this had cured, I moved on to the sides, followed by the bottom sections:

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As I wanted to keep all edges sharp, I made templates for the glasscloth and cut the parts with a very small overlap, so it wouldn't bend over the edges. Once cured, I cut the overhang with a sharp (razor) blade and used sandpaper for the rest, carefully watching not to sand through the glasscloth.

As can be seen in the picture, I used as little epoxy resin an possible to avoid runners and 'floating' of the glasscloth.

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Once the glassing was done, I added two thin layers of epoxy to cover the weave of the glass; as I had to work in sections and sand and degrease prior to every coat, this took the better part of a week, one flat surface a day.

Now the hull looks like this:

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I had a few spots, where air had been trapped under the cloth, so when I started sanding, there were a few holes, exposing the wood, so I added a few patches with the next coat of resin:

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This has been sanded last week and covered with a final layer of epoxy.

I made sure to sand each layer within 24h, as fully cured epoxy is rock hard and very hard to sand.

Regards, Jan.
Last edited by pompebled; Oct 18, 2015 at 08:01 AM.
Dec 05, 2011, 03:41 PM
Boaters are nice people.
Thread OP
As my intended testtank turned out to be too small, I have to resort to lying on my belly at the canal near my house...
The weather hasn't been favourable lately for (outdoor) balance testing, but I have the suspicion, the access to the interior of the boat will be a major issue, as the superstructures are very small.
I know from my 75 cm model that the weight needs to be very far back, the batteries were against the transom, with the deck in place on the 110 cm model and the 'goodies' of the depth charges and ammo cabinets in place, this could be a major problem.

Last sunday had reasonable weather and my daughter was available for 'camera duty', so off we went:

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I had secured the motor in it's position with some string and positioned the batteries all the way back, so the CoG would be at 30%, as I would balance my FE:

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It looked ridiculous and made to boat ride with the nose up:

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So it was down on my knees again to move the batteries forward:

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This looked a lot better, so off I went to the end of the jetty:

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Getting the boat to line up was tricky as it blew half a gale and the hull was still very light:

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Having other hobbies, like kiting, is an advantage, after having rolled out about a hundred metres of one of my kite flying lines, I was ready to go:

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Go!

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And catching out the cameraman, as with spooling up the line, the boat came rapidly closer to the shore:

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Thanks to my daughter for taking the pictures, she also made a few movie clips, but those need some editing before I can show something, the quality is poor, so maybe I'll get a real video camera next time.

I'm pleased with getting the balance at least half way right, next is installing the drive train, to see if the boat runs similar under it's own power, hopefully a bit quicker, as there's a limit to how fast you can reel it a kit line...
I'll have to wait for less wind to go testing without a deck, as there was a substantual amount of water in the hull after a few test runs into the wind, fortunately only the batteries and the motor were on board.

Regards, Jan.
Last edited by pompebled; Oct 18, 2015 at 08:10 AM.
Dec 05, 2011, 07:37 PM
"Take the Cannollis"
Steve Bad's Avatar
That is quite an unusual build technique.... don't think I've ever seen
a boat built with the "lost wax" process........

Looks good !
Dec 06, 2011, 03:42 AM
Boaters are nice people.
Thread OP
Quote:
Originally Posted by Steve Bad
That is quite an unusual build technique.... don't think I've ever seen
a boat built with the "lost wax" process........
Looks good !
Hi Steve,

Keep in mind that was done 12 years ago, before I had internet and my only source of information was a German RC-magazine.
I based it loosely on the 'German rubber' method, which is used on curved shapes.
As mine was boxshaped, I thought that candle wax might do the trick.

Regards, Jan.
Last edited by pompebled; Dec 20, 2011 at 04:07 PM. Reason: typo.
Dec 11, 2011, 11:25 AM
Boaters are nice people.
Thread OP
A little update on the progress, I scanned the rudder section and 'paintshopped' the depth charge clutter away to get a clean look at the rudder assembly:
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Based on the experience with the smaller 75 cm version, I enlarged the rudder surface, to avoid having no steering at all when on the plane.
The blade is 0,8 mm brass, the shaft 4mm spring steel, unfortunately my Dremel cutting disks were thicker, so the slot in the shaft had to be sawed manually, which, due to the nature of the spring steel, took some time...

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As brass soaks up a lot of heat, I used a paintstripper to help heat up the material, while soldering the joint with my 100W iron.
It must have been a peculiar sight, me soldering away, with the paintstripper clutched between my knees...

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Admittedly not the neatest job, I may have to add some more solder and heat to get a smoother finish.

A little testfit on the transom:

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This week at work, I used the circular saw to cut some aluminum U-profile into a motormount.
It fits nicely between two bulkheads.

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To get the angle right, I'm going to make a wooden support onto which the motormount will be attached using silicone, to dampen the vibration and noise to the hull.

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Regards, Jan.
Last edited by pompebled; Oct 18, 2015 at 08:18 AM. Reason: typo.
Dec 20, 2011, 04:04 PM
Boaters are nice people.
Thread OP
Progress is slow, but I've finished the rudder assembly out of brass strip and tubing:

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Despite softening the brass strip with the flame, forming the brackets turned out to be a lot of work.
The glare in the pictures fortunately masks some of the toolmarks still visible...

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Once it's mounted onto the hull, the motormount and propshaft are next.

Regards, Jan.
Last edited by pompebled; Oct 18, 2015 at 08:20 AM. Reason: typo.
Jun 22, 2013, 11:36 AM
Boaters are nice people.
Thread OP
I finally had some time to work on the M.A.S.

The motormount has been made out of aluminum L- and U -profile and has been glued into the hull using polymer kit:

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As you can see I abandoned the big heavy fan motor set-up in favour of a lighter and more compact outrunner, this allows for a much shallower propshaft angle.

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The two bolts in the motormount are for adjusting the height and keeping it in position while the kits (slowly) sets.
Once the kit has fully cured, the bolts are removed to minimize contact with the hull, to avoid amplifying motor noise.

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The propshaft is a 5 mm Raboesch with needle bearing at the end, I'll need to keep the stuffing tube greased properly to avoid getting the bearings wet.

Next is the strut between the hull and the rear bearing.

Regards, Jan.
Last edited by pompebled; Oct 18, 2015 at 08:34 AM.
Jun 23, 2013, 01:58 AM
Sea Dragon-Lover
Umi_Ryuzuki's Avatar
What are the specs on your new brushless motor?
And what size propeller are you planning on using?

Jun 23, 2013, 06:50 AM
no such thing as to many boats
louie R/C NUT's Avatar
Nice work
Jun 23, 2013, 10:27 AM
Boaters are nice people.
Thread OP
Hi Umi,

I see i forgot a link to the motor in question:
http://www.goodluckbuy.com/aeolian-c...aeroplane.html

Powerwise it's way over the top, but there's always the ESC...

I have room for a 55 - 60 mm prop, most likely candidate is a 45 mm X-prop, but I'll have to go test what will work the best and give me a 'sensible' topspeed.

The original was capable of 44 knots, no doubt I could achieve that with the power available today, but that would look rediculous and make the boat extremely hazardous to drive.

Due to the vertical sides, the hull tends to dig in when cornering at high speed and from the 75 cm test model I know what will happen next; the boat will turn over...

Regards, Jan.
Jun 23, 2013, 11:51 AM
Registered User
Jerome Morris's Avatar
Looks like she be fast.
Jun 24, 2013, 11:33 AM
Boaters are nice people.
Thread OP
A tiny update (had to work today...); the strut is in place, as is the grease tube.

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The reinforcement (two steel pins) are on the inside, laminated to the bottom with glasscloth and epoxy, in order to have as little drag under the hull as possible.

Pictures will follow as soon as the hull can be turned after the resin has cured.

Regards, Jan.
Last edited by pompebled; Oct 18, 2015 at 08:36 AM.
Jun 25, 2013, 04:33 AM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
Guessing either 3 or 4 cell Lipo? with the motor

Cheers
Nick
Jun 25, 2013, 05:28 AM
Boaters are nice people.
Thread OP
Hi Nick,

The plan is to use 4S, giving me something of 10.000 rpm under load.

Depending on propsize and pitch she can be too fast easily, but that's not my goal, this boat is intended as a walking companion along the canals of our town and on holidays, where my small tug has trouble getting into the current of rivers like the Moezel and Weser.
A planing hull with sufficient power should have no problems navigating larger rivers.

When I have the rudder installed, I'll fit a temporary plastic deck to keep the spray out and go testing with various props and lipo's to determen what's a 'sensible' set-up.

Without sprayrails, the bow wave will most likely creep up to the deck, so having that closed is a must to avoid getting a lot of water in the hull.

Regards, Jan.
Last edited by pompebled; Sep 14, 2013 at 08:09 AM. Reason: Typo.


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