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Author Topic: Ocean Pearl  (Read 3038 times)

Crossie

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Ocean Pearl
« on: December 07, 2015, 05:31:45 pm »

    This is my first build log type post so I hope that I get things right, this is not the usual run of submarine something a little more light-hearted than a fighting machine.  One of my sons has the enjoyable hardship of working in the Caribbean where some seriously wealthy people play with their very big boys toys such as these machines........... http://www.seamagine.com/assets/SEAmagine-OCEANPEARL-2.pdf .
          As I only have a quite small boy's wallet my toys are appropriately reduced in size, in fact down to about 1/8 scale which will make this model about 560cm long and 310cm wide, these dimensions are a bit variable because I will build it around a couple of 15cm diameter commercially available acrylic spheres to save myself the trouble of vacuum moulding them.
          A couple of hours looking at images on the internet yielded enough views from different angles to be able to sketch out a drawing.....can't call it a plan really.......so that I can start construction, my intention being to make a plug to subsequently mould the 'bodywork' maybe in grp/epoxy or perhaps polyurethane plastic. Looking at the pictures it can be seen that this machine is largely made up of flat surfaces with rounded off corners so that makes things much easier, I've got a lot of depron sheets gathering dust in the shed so that determined the material for the plug. This has a disadvantage in that it is quite 'tender' and  needs a lot of care to avoid dents and notches.....it was cheap though! . The plug as shown below was then painted with alkyd enamel primer, sanded and then waxed.
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Crossie

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Re: Ocean Pearl
« Reply #1 on: December 07, 2015, 08:55:44 pm »

    Someone asked me why the multi-colours, well that is just the result of rubbing down successive layers and high spots showing through.
        Anyway a bit more progress today and have I have layered on some silicone to make the skin mould , so that was one coat brushed on to avoid air bubbles and then another 3 coats with fumed silica as a thickener in the mix. Unfortunately the only stuff that I had in the workshop was a quite soft formulation- Shore A 20 but will have to do .Using silicone will allow me to fabricate the body using various resins depending on what I have to hand or feel like using and because the sides have very little relief it will make removal of the cast from the mould  much easier. Also it means that the plug is much less likely to be undamaged during this first stage and could then be used again.
       So here it is now- - rather like some sort of pink, angular lobster!

                                                       Trevor
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Crossie

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Re: Ocean Pearl
« Reply #2 on: December 08, 2015, 02:12:11 pm »

   In the picture above the white thing is a plaster ''jacket'' which is formed over the silicone ''skin'' when it is cured but is still in place over the plug. This item then keeps the silicone skin the  right shape when laying up the mould,
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Crossie

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Re: Ocean Pearl
« Reply #3 on: December 08, 2015, 02:24:39 pm »

 

 When it is removed complete with the silicone skin, with luck there will be no air-bubbles and provided that the waxing and release agents were applied adequately it should not stick anywhere and I'll have a useable mould. As you can see in this picture, there are a couple of places that had not enough protection and the silicone has bonded to the outer layer of paint- the silver/grey bits, so these will show up as small depressions in the finished cast. That will have to wait till tomorrow when I'll have to get the workshop temperature up a few degrees, I've got some polyurethane resin handy and that needs warm and dry conditions to get a successful result.

                                                           Trevor
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Big Ada

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Re: Ocean Pearl
« Reply #4 on: December 08, 2015, 04:55:56 pm »

Wow, this looks an interesting build to watch.

Len.
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Re: Ocean Pearl
« Reply #5 on: December 08, 2015, 05:41:06 pm »

Just clean the stuck paint off with some paint thinners before prepping for moulding.

Crossie

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Re: Ocean Pearl
« Reply #6 on: December 08, 2015, 06:52:44 pm »


 Well Len, I hope that I can make it interesting enough! I don't really have enough patience for the mega detailed type model and I certainly admire many of the wonderful models shown in Mayhem but I do enjoy making things that are a bit different and might throw up some new challenges. This model will operate the same as per full size in that it will have a pumped air bladder system to vary the buoyancy down to just positive and will use a vertical thruster for diving so that should power fail, it will surface. I think that the more difficult aspect of the construction will be organising  the placement of the system components to ensure that the centre of gravity is at the vertical thruster axis which is just behind the cabin dome so that it dives reasonably level, the two rear horizontal thrusters mounted under the tails are for fore and aft and sideways movement. I've just got to get the boring bit of moulding the body out of the way first.

      Thanks Sc. I eventually managed to dislodge the paint, it wasn't very thick, only microns I guess but was really stuck. If the pull from the mould isn't acceptable with a little bit of work I'll have to de-wax the plug and brush on another silicone skin, though if I do that I'll use a stiffer silicone because this one is really floppy with the sides having very little shear . Alternatively I could form holding tabs into the skin to engage the plaster jacket for support- just making the skin lumpier would do it-I'm going to be optimistic!

                                 Trevor
       
                                                                               
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Crossie

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Re: Ocean Pearl
« Reply #7 on: December 09, 2015, 07:43:33 pm »

    After a chilly start to the day I got everything warmed up and spent the morning trying out the mould. Although I have often used polyurethane resins in a 'slosh moulding' technique I haven't tried such an open and flat mould as this one, so while it wasn't an absolute disaster it wasn't a fun activity. The resin was really too low a viscosity and adding fumed silica stiffened it enough to make it stand on the vertical surfaces but then had the disadvantage that it was difficult to get the spreading done within the pot-life of the mix. The net result is a not really attractive lumpy underside to the cast although the topside is just about acceptable, certainly to use as a prototype, but I will most likely mould another using the more traditional epoxy/glass cloth system. This will also come out lighter and weight just might be an issue as there is limited buoyancy in the two tubular structures which retain the flotation bladders and of course the 'bubble' cabin. A lot of the under structure will be plasticard to keep the weight down and some foam can be tucked away here and there no doubt- - early days yet, and I'd get bored if it was too easy! So here's a couple of pictures of today's efforts ,

                                                                                          Trevor   
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Re: Ocean Pearl
« Reply #8 on: December 10, 2015, 09:25:17 am »

Looks very tidy.

Should strong enough in PU, easy enough to sand out any dimples underside.

Will the rear pod thingamybobs be foam filled to counter the sphere's buoyancy?

Crossie

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Re: Ocean Pearl
« Reply #9 on: December 10, 2015, 07:11:31 pm »


 Thanks for the compliment Sc...it's just that I can't get out of the habit of viewing mouldings with aviation standard eyeballs!

 I shall try to get as much of the equipment up front to minimise any balance issues but, as you presume, I do plan to fill the rear 'tails' with foam after I've made up the rear power pods which will be mounted one under each side. These will be a small brushless motor in a sealed case, probably turned up from delrin rod and with a lip seal for the motor shaft and a direct mounted prop.

 The full size craft has a pair of cylinders running the full length of the machine inboard of the bladder casings, these are for the breathing air and so on this model that will provide some buoyancy, especially to keep the tail up. The cabin hemispheres arrived today, these are 150mm outside diameter and as can be seen they are very nicely blown from 3mm sheet, the 20mm flange will be reduced after attaching the mounting/sealing rings which will be turned up from some flat sheet. Not sure yet on what to use though it probably will be Whale tufnol 12mm thick, being easy to machine, tap threads, strong and not too heavy. The intention is to make the cabin functional in that the Rx and small camera and some other gubbins will be fitted there, but instead of the upper shell being hinged as on the full size, it will be bolted down onto an O-ring located in the lower half-shell.

      So here are the bubbles, the next job will be to brush a good few coats of PVA mould release onto them for protection during the build, it'd be a shame to get them scratched!

                                                                                    Trevor
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Re: Ocean Pearl
« Reply #10 on: December 11, 2015, 05:59:31 pm »

Understood. A lot of model submarine hulls are thickly laid up, and would benefit from a glance at how model aeroplane constructors use composites.

Crossie

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Re: Ocean Pearl
« Reply #11 on: March 07, 2016, 08:16:56 pm »


     Well progress has been a bit slow on this project, not through lack of interest, but with so many other things to do it's taken time to find decent pictures of the supporting structure of this craft, and then convert those into some workshop sketches . So here's the chassis just about finished apart from a few brackets for attaching the body shell and cockpit bubble and the propulsion and dive units. The cylinders and channels are  made up from 0.3mm brass sheet and the tubular members are standard K&S stock items, the whole lot weighs just under 600grms so with the potential for the cylinders to displace just under 1500cc when the bladders are fitted , the bubble about 1700cc and there are also the dummy air tanks I will have ample buoyancy in the finished model. I Hope!! Next is to make the propulsion units or hunt for something already manufactured or fitted to a cheap toy.

                                                            Trevor
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