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Thread: alad61 - Italeri's PT-109 to an RC model....

  1. #1

    Default alad61 - Italeri's PT-109 to an RC model....

    As I stated I have finally started my Pt-109 conversion to rc. Is this a clever move? Well time and tide will tell.

    So after gathering some background research came the gathering of parts needed for my first go at a solo conversion, i.e no pre-established fittings kits or internals. However I am sure that you blokes will guide. nudge, push and tell me if I have gone astray. Although looking at how far I am into the build that might be a mute point... As far as assembling a model goes I reckon I have got that down pat. I mean how hard can putting this boat together be...? Anyway from the outset I had decided to run it with three props n motors much as the full scale. This is what I went with, 3 x JR 400 series suppressed motors these I would then attach directly to the prop shafts via some flexible tubing. The props and shafts are from Raboesch. I am using the water proof ones with a bushed strut and 2mm shaft and 20mm type D No 152 brass props. Behind these will be the rudders, which even though they are the minis the look a little big on the kit. I am powering the motors off a 7.2 4600mha Ni-MH pack through a Mtronicks 30 amp speed controller. If my maths is correct the motors combined shouldn't pull more amps than that so I reckon I be good with that. The receiver is a corona 6 channel I had in stock and a standard ball bearing servo to run the rudders....

    It kind of made sense that the first step would be installing the prop shafts, rudders and electronics. My inexperience in this area was certainly a telling mark as I didn't realize how much of the keel I needed to remove in order to get the shafts and housings I had bought to sit at the correct angle. Which I gauged by using the kit prop struts as my guides. What I then did was use a two part putty pressed in and around each shaft housing. which I then shaped sanded followed by some blade putty to get the final contours and low spots sorted.

    That took just over a week to do. Next on the do do list was mounting the servo, speed control and receiver supports. I decided to go with hollow rectangular ABS bar for this so I could keep the weight down plus I know how to work this better than timber in a model build. The other thing the equipment frame will do is add some rigidity to the hull. As a static kit the hull as is more than ample but feel as an rc model a little addition bracing is needed.

    As mentioned above the 'mini' rudders on this kit don't look so mini and I also needed to run them through some styrene tube acting as a long bush as the rudder shaft housing had a good 30+mm area beneath the thread to the o-ring seal and mounting base... I went through a couple of set ups for mounting the servo and rudder arms. On paper it was doing my head in and I realized I was simply over thinking it. In the end I tossed out the tiller arms that came with the rudders and picked up some control arms from my local LHS that had the ezy connects with them. So now with just one piece of 3/16th rod I was able to govern all three rudders. I then set the servo up so that a singe rod went directly down from the servo arm and through the middle tiller arm. Switched on the system then moved the stick on the tx and promptly tore the servo and bracing mounts clean off the hull!!! By then it was getting late so I spat the dummy and went to bed. Then at some ungodly hour my sub conscience through up an image of the old rack n pinion steering system in my first car and that's what I went with after rebuilding the rack/brace.

    Feeling pretty pleased with myself I boldly moved on to installing the speed controller and motors. My first attempt with mounting the motors didn't go as planned. I had purchased some metal mounts for them and the plan was to fix them to the hull with countersunk bolts through the hull and the heads recessed and filled over. Firstly I didn't take into account the curvature of the keel and secondly the mounts had the motors sitting to steep for the direct drive to work effectively. After some time in trying several ways to make them work I feeling a tad over whelmed. so I downed tools and the following night did some research on the old world wide web. My final fix still seems a little odd to me but it appears to be holding with the couple of full throttle bench tests. In the end I used some dense hard foam cut down into wedges and shaped to fit both the keels conture and the shape of the motors. I then stuck each motor to the foam mount with a good dollop of silicon, tidied them up and left them to dry for a day. The next night then fixed them to the model. To make sure I got good adhesion for the silicone and mounts I used some 80 grit paper to sand the rough up the plastic as well as filing some grid lines into the foam. The next night I was thinking how clever I was to leave the main prop struts from the kit installed but the first full throttle bench test showed me the errors of my ways. The motors and mounts were rock solid but the kit struts not so. with the motors kicked in to full throttle they didn't hold up to the thrust loads so they need to be replaced. Fortunately the shaft kits came with a multipostion three armed strut bearing so all I had to do was remove two of the three supports on the bearing clean up the one broken styrene kit strut, remove the other two kit parts, then drill and file out a groove to take the new struts and bobs your uncle. With the new prop struts and bearing housing being ABS all I needed to do was use some plastic weld to glue them in and then ca and baking soda was applied on the inside of the hull to fill the gaps and provide additional support.

    When that was all done I again used the foam to add a battery mount between the motors and servo. I know some body will comment about the wiring on the motors being parallel rather than series but I have had things in series fail and so take down the rest of the string due to the break in the circuit. So unless absolutely required I will always go parallel... I have still yet to put an inline fuse in the system and hard wire the deans plug to the speed controller

    I also still have some extra filling to do around the prop shaft housings but I'll work on that after the initial primer/filler coat and I am still deciding on whether to reshape the rudders to something closer to the actual boat but as they are thin I am concerned that vibration from cutting would damage the way they are mounted to the shafts not to mention me making a botch job of it...

    Feeling rather chuffed with my efforts I was quickly slapped down on how to gain internal access whilst maintaining the best water proof integrity I could. However it appears that Italeri had rc'ing this boat in mind when they designed it by having the wheel house and day cabin areas of the deck open. With that thought I assembled the main pieces of the cabins as a test to see how it would work.

    And work it just might. Firstly the deck need to be a bit more ridged so I added some rectangular I beam sections to the underside. Along with some plastruct angle as coping to help keep out any water.

    But even with the extra bracing I needed to find a way that the cabin assembly could be held to the deck and stay in place whilst the boat is under way. As it is it's not a bad fit and sits reasonably well on the deck. But that's in static mode... Being a hoarder of leftover parts, bits, fittings etc I found these two brass pieces from my robbe seawaolf sub when I converted the automatic front planes to servo controlled. A little reshaping and the screwing them in place under the two aft vent horns gives me a solid aft fixing point. I also added a klick-on in the day cabin that attaches to a small screw in the I-beam cross piece... And yes the vent is facing the wrong way they are just they were just there a test...

    Here is a tops side view of the deck with the added coping to help keep out water. Eventually I will be adding styrene sheet in the gun turrets for stopping water ingress as well. Now that I have drilled out all the holes needed to add the top deck fixture and fittings in place I plan next to fix the deck in place with the screws provided and use a marine grade polyurethane sealant/adhesive as well. That way I can paint over the seal and it will add extra waterproofing too. After I add more foam to the inside as added insurance and do some tub test to check on buoyancy and how it sits.
    Last edited by Kazzer; 08-11-2013 at 08:47 AM. Reason: Title change
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


  2. #2
    Join Date
    Feb 2009
    Location
    Zephyrhills, Florida
    Posts
    5,972

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    Looking really good Alec! Your speed control looks to be waterproof by its appearance but your steering servo and receiver are definitely not. If you are just going to be idling around in it then it might be Ok, but if you are going to be taking evasive action after a flank speed run youll probably wished you had a water resistant radio box to house your electronics. Perhaps something to keep in mind.
    IT TAKES GREAT INTELLIGENCE TO FAKE SUCH STUPIDITY!

  3. #3

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    Thanks Mark. Words of wisdom & I gather of experience also. I shall look aways to keep out the h2o from the rx & servo. By the feel of the weight and balance I am going to have to monitor any mods with additional weight. But I will add it to my list...:biggrin:
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


  4. #4

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    As I stated above I am planning on fixing the deck to the hull with the screws provided and using a marine grade polyurethane sealant to give a paintable waterproof seal and still allow me to take of the whole deck to access all the working parts if need be. However this clever plan requires certain modifications to make that work as part of the torpedo tube mountings are meant to be permanently glued to the deck over two of the screws... The idea I eventually had was something that I had come across many times over the years on various model kits to add parts after certain sub assemblies were done. Here's how I went about it...

    Firstly I needed to make a 'key mount piece for each of the rear tubes. for this I used some styrene tube cut to about 30-35mm and a piece of brass push rod which was glued so only about 2-3mm protruded each side


    Then the existing hole in the assembled tubes need to be widened to take the styrene tube


    Then the turntable mount for the deck needed to be drilled out to give a snug fit for the styrene tube piece


    I then filed out the keyhole slots into the tube, A sharpie was used to mark the position on the deck piece and tube foundation bearing so I had the correct position for the key slots. The idea being to push the tube onto the key piece and then pull the key piece down till a firm fit is felt. When that is achieved I used the liquid cement on the under side of the deck mount piece to glue the styrene key in place


    The next mod was to take the deck locking clasp and drill a small hole through them and the corresponding piece on the front of the torpedo tube. so that when the tube is in place a small brass pin is inserted to lock it down. They also needed the addition of additional styrene fillets to get a level mount without twisting or pulling up the deck..


    All that was need to finish it was position the twin rail guide mount towards the leading end of the torpedo and glue it to the tube guide mount


    This was all then repeated for the opposite side giving me the final result


    At this point I have only assembled the two rear tubes in their basic format just so I could get the mechanics working. My next task is to add styrene wall in the inside of the gun well to help keep out water. I am also rethinking the idea of using some thin epdm rubber as a seal between the hull and deck over the use of a polyurethane sealant. I will need to make a decision sooner rather than later as it gets closer to completing the basic assembly and then some tub tests. But I am thinking the rubber lets me cleanly remove the top deck as a whole to access whats beneath. Of coarse the other thing is cut out some expanded foam to fit the underside of the deck as emergency flotation...
    Last edited by alad61; 08-14-2013 at 08:22 AM. Reason: Didn't proof read...
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


  5. #5

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    What have I done over the last few nights...

    The one thing I discovered about the instructions is that they aren't all that clear. Why you ask? Well when dry fitting the forward tube launchers I discovered that they also cover the deck mounting screws!! So now all for torpedo tubes are removable when needed. Also I was not happy with the deck skylight windows. As the kit goes they are pretty good for a static job but I was concerned about how the thin acetate/acrylic window pieces with the etched brass frames would stand up to the handling of the boat when rc'd. Normally I would use micro-scales krystal klear for fixing these sort of parts to a model. However krystal klear is basically a modified pva glue thus it would fail fairly efficiently in a water environment. I could use one of the liquid glues I have for the clear parts and then the only other glue would be ca for the pe parts but as that would be just a thin cohesive on a thin clear piece I was concerned of failing during handling with the styrene inevitably getting some flex. So I experimented with clear rtv silicon. Firstly I used the ca to glue done the pe part and then covered that in blue tape. turning over the deck I squeezed a bit of the rtv into the skylight opening and left it to dry. My first thought with this idea was that since the silicon wouldn't hold paint I only had the paint the window frames after some masking over the silicone 'glass'... Wrong!! the silicon when, even gently applied in the opening made its way onto the top of the pe frame under the tape. Onto plan 'B'. The first part in placing the pe parts and covering them with tape didn't change. But for the second part I mixed up some epoxy resin/glue and filled the window with that. Now some of the pe parts did get covered in the resin but with some careful masking I will be able to paint them up pretty good...


    The cabin window will prove a different challenge but I have some ideas to get round those and still use the clear inserts that came in the kit. Once the resin deck lights had fully cured I stuck on a piece of styrofoam under the forward deck area as added buoyancy...


    Checking the balance of the boat and its weight I relocated the battery forward of the motors. A good thing to as the first float test had the stern sitting a little to deep and lifting the bow up. Also in the picture is a quick makeshift waterproofing on the receiver. using a small zip-lock back I took the rx out of its case sliced a small hole it the bottom of the bag. Inserted the two rx leads from the servo and esc plugged that with some of the clear marine rtv fed the areal wire from a corner of the zip top and sealed that with some rtv. Not pretty but it works. As for the servo I followed some tips on water proofing servos from the old you-tube. Which essentially was layering the seams with rtv along with the bottom and then using a small o-ring and some tamiya diff grease to seal off the shaft and knuckle on the top. Again brutal but devilishly simple and effective.


    So with the battery repositioned I screwed on the deck added the cabin and all for torpedo tubes and then put it in the tub and I was pretty happy with how she sat in the water. The instructions say to do the waterline at 21mm from the bottom of the keel. which is where I added a pen mark to the bow and each corner of the stern transom so I could check.

    After checking how it sat I turned on the tx and the rx and then played... Uh-hmm, sorry tested it a bit. At the moment I only have two props on as the third one for the middle shaft is on back order. But I have to say that when the throttle was pushed to flank I had to be alert, as even with just the two props it wanted to launch itself out of the water so once the third prop is on it will scoot. holding the bow steady I slowly increased the revs and I was glad to see no obvious signs of prop walk, even with both props spinning the same direction. The lack of obvious prop walk I put down to the slightly over sized rudders which commanded pretty good too. Happy with the tank/tub tests I took it back to the bench opened it up and was greeted with some 6mm of water sloshing around the the inside.. So I dried it out and then put it back in the water with the deck off to see what was causing the leaks. What I found was water coming up the rudder posts mounts, not on the inside where the actual rudder post/stem slides through but between the post support and the styrene tube block I added to allow the nut to pull the mount to the hull proper. the picture shows where water was coming through. with the boat just sitting there the water only gradually welled up but with the props going the slow welling became a definite trickle...

    To fix the problem I dissembled the rudders and removed the nut, washer and block/bush then mixed up some epoxy resin glue and put that around the base of the post and lower half of the tread slid the block/bush back in place added some more glue around that and then re threaded the nut and washer till it clamped the post in place and repeated the process for the remaining rudder post mounts then left it to dry over night. The other area that let water in was at the point where the putty I used to mount the prop shafts in place sat on the hull. This I sealed off too but not before flipping over the hull to check out the fillers seal around the prop shaft tube where it leaves the hull. Close inspection revealed a small void so that was filled with some medium zap ca. Tonight I just sat the boat in the tub and left it there for about an hour or so as we had dinner and was most pleased to find the hull inside nice n dry. I also checked out the water line with the top deck removed and found that there wasn't any noticeable difference. However I have still yet to add the rest of the deck fittings and weapons but these being plastic don't carry a lot of weight but we'll see. If it turns out to be sitting to low then I may have to resort to using a lipo pack rather than my preferred NiMh stick battery... Now if all goes to plan I should have the remainder of the deck fittings done and mounted end as well as some open water trials in the wild...
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


  6. #6

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    Ok life can tend to get in the way of "all go's to plan" ideas. But hey that is life. The only part of the plan, which went to plan, was putting it in the open water even if all the deck fittings weren't completed. Try as I might inpatients gets the better of me at times. BLUSHER So whilst I took a break to run my Skipjack and Akula I decided to try out the PT boat... I am sorry for the quality of the video, I only had our little digital on a tripod fixed with a wider view to give the best coverage of the water for capture, also the midday sun bouncing from the plastic and water slightly over ruled the auto settings on the camera. I think it sits pretty good in the water even though the breeze was a bit more gusty that Sunday. On the whole it ran pretty well with a good turn of speed at full throttle. The waterline is not dead on scale but it still cuts the water nicely at flank speed as well as showing virtually all the transom clear of water at flank and the three over sized rudders make it very responsive.

    http://s244.photobucket.com/user/AJ-...bc1b6.mp4.html

    There were however some things I discovered from the trial, a couple of which were... the drive lines still needed some tweaking and after some 20 minutes it took on a bit of water. It seems that the front third of the deck wasn't as flush a fit as it should have been and as the video shows when she headed into the wind and chop a fair bit of water washed over the bow. Which taught me that concessions and sacrifices need to be had when converting things to a working model so I added some additional fasteners to pull the deck down better. I have the screws sitting nice and flush with the hull so once its all painted they should blend in a treat. I also still have yet to add more sealing foam in the bow area too.



    Other tasks completed with the assembly are the torpedo tubes, since taking the picture I have completed the fourth tube. So these are sitting aside ready to be given another clean and then primed. What I didn't do with this kit ws give all the sprues a deep clean. With all the little fiddly bits and constant handling of things I will give each of the sub assemblies a good scrub when they are done. For this I will use a cream cleanser and denture brush under warm water.


    And I have been scooting through and adding all the deck fittings. Although I haven't been following the manual as sequentially as I should, mostly due to assembling things to get the rc side working which has resulted in a bit of a random flow almost like doing a jigsaw...


    What this picture shows is how good some of the kits design is. Because I need to lift of the whole cabin section I couldn't glue the rear gun safety rail and brace together as per the instructions but when the center cabin assembly is locked in place the brace bar sits very snugly into place with the safety rail.

    I also managed to get a first coat of primer/filler on the hull over the weekend as well which I have since sanded back and used a blade putty on to fill in the small voids from mounting the prop shafts. Before giving it another and final coat of the primer/filler now readied for the grey primer.

    Last night I completed one of the 50-cal mounts and guns and most of the exterior cabin add-on pieces, bar the wheel house & windscreen these will be later when most of the main painting is done photos to follow. As I draw nearer to the end of the assembly line I am collecting some stills of the boats as a painting guide. Sadly most of which are b&w but who doesn't like a challenge. I did find a couple of pictures of the boat out of the water and in transit which give a good reference to water and scum line even if they are mono chromatic.


    My original goal was to have this ready to take along to the sub regatta in NSW next month but 12+ hour days at work are winning the time war at the moment. But I ain't waving the white flag yet!!
    Last edited by alad61; 09-04-2013 at 08:55 AM.
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


  7. #7

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    Hi all. Just letting those that care know the project is still proceeding, be it rather stop start of late. I'm into the final painting stages when I'm not to tired from 12+ hour days at work...Very Angry

    I can say that detailing and weathering a model of a mostly ply boat has proved a challenge The Titanic
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


  8. #8
    Join Date
    Jul 2011
    Location
    Las Vegas, NV. - USA
    Posts
    1,603

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    Looking forward to your posts!
    If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

  9. #9

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    As they say... "slow n steady wins the race"

    I have now completed most of the bulk sub assemblies and slapped on some paint. I had an issue with the primer I used on the cabin assembly in that it came out from the airbrush almost dry. The result was a chalky dusty finish that was a mongrel to sand back. That's what I get for trying a different type to what I know... Any in the end I got a result that I am fairly happy with. Also because it is an rc model I have left out some of the detil that I would have normally put in for a shelf model.

    Things still to finish and add are the masts various ropes and flag along with the two twin fifty mounts and the life rings. As I mentioned in the previous post weathering has been a challenge. Not due to difficulty per say but more about how. The Elcos were pretty much a ply boat and those in the pacific were repainted to blend in with the coastal backdrops of the tropical/jungle islands. So that meant things like rust detailing need to be managed differently and dare I say some artistic license so my apologies to any that may be offended by my take on things. Essentially I airbrushed on the base colour then airbrushed the internal corners, joins and recesses were with a black thin wash for depth and followed this to highlight and pick out detail with a series of dry brushed light shades of greens and light grey with a hint of blue tones. Then with the detail picked out I weathered in any salt streaking and light rust from fixtures that I took to be metal. the streaking and rust detail was a mix of pastels and washes. Then I blended and softened some of this with a mist coat of the base color by airbrush and hand brush. The look I was trying to get was a bit of a beaten down look as the 109 was reported to be a little worn and tired when JFK got her.

    The next on the list was the paint list was the torpedo tubes. I have assumed these to be of some sort of steel construction as they needed to carry the torpedoes and be able to stand up to the explosive charge launch system they used. So that is how I weathered them. Talking to an ex navy man who delivers our warehouse stock I got a good understanding how quickly things with show rust on a boat with the salt water and air. The flash makes the rusting look rather garish but under normal light it is a lot more subtle. Again as with the cabin I used a black to shadow the detail on them and then pretty much followed the same steps as I did painting the cabins.
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


  10. #10

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    Then came the main hull. The waterline is a little different to what the instructions recommend as I used the way the boat sat in the water on her first sea trial to gauge where it should be.

    I started by laying down the red and then weathering it down a little using white, grey and different reds whilst avoiding the heavier bleached look that I have done on my subs. Again I am sorry but the flash washed out some of the weathering...
    [URL=http://s244.photobucket.com/user/AJ-1701/media/My%20PT109%20model%20assembled%20and%20converted%2 0to%20RC/PT-109belowthewaterline_zps0c9a7fec.jpg.html]
    Then I masked that off and did the green which was done the same as the cabin. Then I worked on the scum line with a mix of some thin greens airbrushed on followed by pastels applied both dry and wet over which went black and brown washes. I deliberately softened the demarcation line and used a darker wash as I reckon the waters the boat sailed through would have had oils etc floating on the water after combat incients as well as the make shift harbors would have been a little grubby as well...


    Over the last couple of nights I have worked on the small artillery cannon and twin machine gun mounts. If you look at the flack shield on the cannon you can see the red/brown stain on the paint. That isn't rust. That is me trying to show how the jungle mud can stain things. As with the other previously painted parts I will be pretty much following the same technique...
    1: apply a primer
    2: apply a base coat by airbrush
    3: apply highlights via pastels and dry brushing
    4: apply thin washes to recesses etc
    5 dirty down with more pastels and inks for rust and stains etc
    6 blend it with a combination of air and hand brushing via a thin coat of the base colour.
    7: apply a clear coat of gloss followed by a flat


    I have still to apply the clear coats on the guns though as well as finish the main deck and features. But this week end will be used for checking my subs and gear before heading south to the sub-regatta at Gosford on the 6th & 7th of next month.
    Cheers,
    Alec.


    Reality is but a dream...
    But to dream is a reality


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