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Scratch Build Soviet Project 667 BDRM Delta IV SSBN K-18 "Karelia" Scale 1/140

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  • Heart stopingly good stuff!

    David
    "... well, that takes care of Jorgenson's theory!"

    Comment


    • Thanks Gantu,

      You have an incredible ability to dig up some really good stuff. Nice!

      So getting back to the rear outlet scoops and their molding. I have been using the same silicon for the last couple of years, however as mentioned I have found another supplier who produces a molding silicon that is virtually the same and yet is about one third the price. I decided to test a sample of this new silicon on one half of the outlet molds. I have bough this silicon to be used primarily for the top of the hull of the 667 when I eventually mold that. I though that I would use this smaller mold as a test piece.

      I put in the usual ratio of hardener /catalyst as I would have put in using the Dow Corning 3481 but found to my amazement instead of it being pretty much as overnight cure it was hard within about 3 hours! Here you see original outlet pieces placed back in the mold ready for the next half of the pour. I have rubbed lanolin around the mold as the release and rubbed some extra into the air vents to block them up, inhibiting the silicon from flowing into them.


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      I used the rather cunning method of using rice to measure out the right amount of silicon so you don't waste it. I don't know what happened but I over estimated and this half of the mould turned out really thick. I had to them create heightened dam walls around the side for the next pour. I did'nt see the need for a whole new box. This second pour utilizes the new silicon brand. So far so good..

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      It was set really quickly. I couldn't believe it.


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      I did'nt put enough green pigment into the first mold so It looks virtually white. I colour code all the appendage molds of all my models. 667 is green. The darker green one is the news Silicon I mentioned. Really happy with this product. All I have to so is trim back excess silicon and clear the paths for the air vents if then have been molded in/over.

      I have yet to actually mold sample pieces yet but should do really soon.

      I have started in the meantime on the fin. This is the single largest mold as for the first time this will be one piece. It will involve me building a box to fit the piece in and pouring the silicon over the top. Previously all my sail / fin molds have been three piece, two sides and a top. This time I decided that it would be easier doing it this way. It also means that less detail would be lost around the joint between the top edge of each fin piece and the rim of the top. On 667 this are at the front has lots of widow detail I did'nt want to loose.


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      Firstly I needed to finish some final details like the round collar sections that push the planes just a little out from the sides of the sail. These were made from light 1mm thick styrene.
      I then also needed to add the nav lights on the side. Once these were done I needed to create a filler block that would fill the surfaces underneath the rear of the sail where the missile deck will eventually sit. This piece is primarily designed to create the void needed to make sure that I can get fibre glass in place when I am laying up the sail mold. Otherwise I would need to use a seriously bent brush to get underneath the mold in a really awkward way and layup. This piece of Renshape generally follows the profile of the rear of the fin and needed to sit level with the base of the fin as it would be mounted to the molding board.



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      More next week.

      Thankyou


      David H




























      Comment


      • David, will that sail be hollow or will it be a solid block? GRP or resin? Regards, Jörg

        Comment


        • Hello all.

          The Fin is hollow. It is a one piece mould so that you will easily be able to put plane movement mechanism in there.

          So I created a Renshape profile around the open section at the back of the fin to make it easier to get the master out of the one piece mould when its finally done and to make it easier to fibre glass inside the mould and pull out the fibre glass finished piece. I simply used super glue to glue this block in place. I then placed some masking tape very closely to the edge and filled around the edges and sanded back lightly to make sure that the edge of the sail master was still clear and not lost to the Renshape and filler crossing over any edge line that I would want to follow later on when cutting out the profile of the path. Pull off the tape when finished.


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          I then created a plinth ( for want of a better term) to separate the fin mould from the base surface. What this does is simply allows me margin to cut off when I am finishing the parts. I will simply sand back the 2-3mm of extra material to get a nice clean straight lower edge. There would be a lot of sanding and smoothing required to get the master just right.

          Once this was done all I needed to do was make a box to fit the mould in. I would need sides that would be at least 5mm higher then the top of the mould. This would be needed to get the mould nice and thick. Once again I cut 5 pieces of particle board to size and drill and screw the holes needed to seal up the sides.



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          I marked out a center line for where the fin would be place. I then drilled two holes in the base of the box and two corresponding holes in the base of the fin to then screw the fin down inside the base of the box. Then screw the sides in.


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          Then I boxed up the end if the box and poured rice into the mould. I have to be economic with silicon at the moment. I have to save the new stuff for the hull moulds but in the meantime I will use the old 3481 base stuff for this mould. This one will use a fair bit too. then you pour out the rice into the container that you are going to use to mix up the silicon. Mark the side of the container at the height of the rice and substitute with silicon. Fool proof, really.


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          Mix up the silicon. I have this bad habit of really liking the smell of mixed silicon. Then add some green pigment to get the colour right. Colour co-ordination is important.



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          The bubbles slowly rise to the surface. This is going to be a big chunk of silicon.

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ID:	134586 Originally I didn't know If I would need to permanently have the box around the mould as I wasn't sure that the wall thickness of the silicon around the sides of the mould would be strong enough to hold their shape and not bulge outwards. I needn't bother. This mould is so thick that it holds its shape really well and once I say up a gel coat and then weave, it supports the shape really nicely. I put an initial grey gel coat in side the mold. Let that dry and then put in some fine weave 6 oz. Then another layer of heavier weave. 8 oz. After this there is enough rigidity to pull the part out. Really happy with the mould, and really happy with the parts coming out...


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          This pic shows the finished part. I have to cut out the back lower section. This comes out messy as I try not to put too much gel-coat and weave over the area that is the filler created by the Renshape fill in. I take a Dremel tool and cut out the back bottom half, following the line of separation from the edge of the fin master to the Renshape. I also grind the inner lower rim so that the fin will sit nicely over the outline on the hull where the fin will be attached.

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          In the background you can see the hull board in the final stages before starting the hull moulding process.

          Enough for now....

          David H












          Comment


          • Hello all,

            So now I am almost ready to start the slow tedious process of creating the two hull halve moulds. Once again the top mould will be a silicon mould with a fibre glass hard shell. The lower hull will be a hard shell fibreglass mould. The reason for this being that the top mould has so much more detail than the lower one. It is also often a more complex shape so the Silicon is best suited to capture the detail.

            My experience with large silicon moulds has been a bit hit and miss. I have had problems with undulations being caused along the length of the hull, this has mainly been due to the varying thickness of wall over the mould. The smallest undulation is really noticeable especially when you have a large dead flat surface like a missile deck. This has been something I have been working on overcoming. I have used two methods. Firstly I came up with the idea of using a really stiff woven steel mesh like a rigid security door mesh that is really stiff but will still allow silicon to mould its way in and through. I decided to cut some shapes out of this mesh along sections of the hull that would require a consistent shape where undulations would really not be good. (An undulation being a up and down surface across an area that should'nt).

            I cut out a flat section of mesh for the missile deck and also decided to cut out and bend a small long section into an "L" shape that would run down the side of the mold in order to create a nice straight edge of the edge of the mould to line up with the lower hull. Once I had created these pieces then I could turn my attention to the development of the moulding board.

            The moulding boards were built out of particle board. A decent large piece was left over from the renovation and extensions to our kitchen. So I took the board to school and cut out the required pieces to make the sides and the top. Then taking them home i could take out my drill, drill the holes and the countersunks and assemble.



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            You make the base around the board rather deep so that you can ensure that the flat board that the model will actually be based upon is dead level. The mould needs to be absolutely flat. I then countersunk the holes, especially the ones on the top and will when needed cover them over with tape especially later on when i am glassing over the are covered with screws.

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            As you can see from this picture I need to now mark out where I will put the cut in order to have the hull sit level at the equator for the two moulds to be split. This requires me to strap down the hull to the board, making sure that it aligns with the centre line and then using a level base tool with a pen attached to try and accurately work out where the widest point of the hull translates to its equivalent point on the flat board below. Takes a bit of work.

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            I also have to work out the corresponding position alone the rear flat surface for the twin booms. After I have done this I can then start cutting out the profile with a jigsaw.
            This cut is started with a series of drill holes in the board just on the edge of the outline. This helps get the jigsaw blade down in place. Once the cut is done it is never perfect and a rasp is taken to the edges. Then it is a case of taking the hull and pressing it down into the hole to try and get it to sit level.

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            This photo shows the gradual shaping of the sides so that the hull will slowly work its way down to the waterline and sit nice and level. Then I measure out the where the bottom of the hull sits underneath and cut out some small particle board pieces and secure them from underneath with a couple of screws to make sure that the hull will not push through any further.


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            Next will be lots of Play doh!



            next time...

            David H





            Comment


            • Hello all,

              So I am settling the hull down to equator, nice and level all the way around with the exception of the rear with the horizontal plane fillets. As mentioned way before, Soviet boats have the stern planes raised slightly above the centreline of the hull. I missed this when I was at the tail end of building the Papa last year. Only to be informed by Jorg and HWSNBN. Thanks guys! Anyway I have taken the decision to raise this filleted section slightly above the moulding board plane. This feature will easily be captured with good detail in the top mould but will it play havoc later on when moulding the two huill halves and getting them to line up properly. Time will tell..

              I now have to fill in any gaps around the sides of the hull where the cut out does not meet right up against the hull. This is to stop extra silcon from seeping down in between the hull and the board. This takes a little while as I carefully scree away any excess playdoh. Once this is all done and consistent then it is time to start the perimeter.

              As also mentioned previously I will be using a new silicon from a supplier I found down in Melbourne. It is more cost effective than the Dow Corning equivalent (Silastic 3481 base) I have been getting up here.
              in Newcastle. After the hull is sitting where I need it to sit and secured, I then screw down strip of pine to create a wall to hold the runny silicon once it has been pouring onto the top hull and runs down the sides. In previous years I have simply cut square strip of pine about 10 mm high and screwed it around the perimeter of the job at a distance of about 15-20mm from the edge of the hull. I have sometimes glued small wedges on the inside to create register points to line up the mould as it sits inside the fibreglass hardback. This time I angled the stock to create a gradual sloping down silicon flange when stock is unscrewed and taken away. This will make the fibreglass take a less abrupt 90 degree bend downwards towards the base of the splitter board. Fibreglass does not like tight radius unless you can vacuum bag it.


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              At the front I did not have any curved pine stock. So I simply heated up some PVC pipe and then silicon ed it down to the boat making sure that it met up with the sides and had a little Play Doh underneath the corners to stop silicon getting away.

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              The silicon is mixed up, You want to do this in several layers and as has been the mantra of the HWSNBN make it thick. So I have bought 3.5 kg of the stuff. I will mix some thixotropic hardener into the mix when pouring the silicon down the sides of the hull. I am aiming for a initial thickness of about 5mm.

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              Firstly I pour the base silicon around the sides. This when set will give a nice smooth side flange. Not that you will need that. Ideally the texture should be roughed up to give maximum keying into the fibreglass hardback. There will be plenty of layers over this to mess it up.

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              I was amazed at how quick this new silicon setts. It was rock hard after about 5 hours. The previous stuff I had to leave over night. Amazing! I could then pour a layer over the top of the hull proper. I mixed up some Silicon with some thixo to thicken it up to cling to the sides better. I mix the silicon up with a stick but apply it with a brush. I work the silicon around in a circular kind of fashion in order to work it gently into all the scribe details and to make sure as best I can that it gets into every nook and cranny. It really feels and looks like I am working with thickened PVA glue.


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              Till next week...


              David H




              Comment


              • Hello all,


                It's been an interesting week. Around the North coast of NSW we have experienced some of the worst Bush fires in Australian history. These fires are 100-500 kms away and yet we have have been blanketed in the worst bushfire smoke and ash I have ever seen. Here is a pick taken just the other day although this pic doesn't do it justice, the sky is really brown. As if the drought isn't bad enough...

                ​​​

                The red dot is the Sun.

                ​​​

                Anyway, back to the work...

                It is important that you pour up several layers of silicon down. After the first thick layer had been put down and dried it was time to embed the stiff mesh. I have found that this material gives me an extra insurance policy against having large flat surfaces undulate like what could happen on a missile deck as I still don't totally trust silicon to give me an absolutely flat large surface. I took some old security door mesh and marked out three pieces that I wanted to embed into the silicon. Two thin long pieces along the side of the mould to give the sides as straight as possible an edge that should line up with the lower hard shell mould piece. These long rectangular pieces are given a "L" section by taking them to the "magnabend" which is tool at school that bends metal simply using electro magnets. After this I cut out the mesh piece to fit over the top of the missile deck and slightly wrap down the sides.

                So after mixing up a new batch of silicon I them lathered an new later over the areas to be reinforced with mesh and then pushed the mesh into the silicon, squishing out silicon through the holes in the mesh and then applied more siliicon over the top to completely cover the mesh and then earlier layer of silicon.

                ​​

                ​​​

                As can be seen in these images the layers applied have been pretty thick. The mesh is embedded inside and helps create a more boxy look. By this stage the wooden sides have been removed and I took to the silicon flange with a knife to gut some triangular registration points. The angled in the silicon created by the angled wooden borders will make it easier to lay up layers of F glass without the weaved pulling u around tight bends. Once this has all dried it is time to as a layer of fibre glass gelcoat. A nice thick layer to capture all the detail before laying down the first weave. Once again all my hulls are down in bright Orange.


                ​​​

                ​​​

                Many years ago a friend of mine who was a surfboard shaper, gave me an enormous roll of fibre glass strand, in a huge and very heavy ball. This thing was soo dense and heavy and after years of pulling off strand and chopping it up does not seem to have gotten any smaller. Anyway I mixed up some resin and poured around the base edge of where the silicon mould meets the board and wrapped numerous circuits of strand around the base. I worked it up the sides of the silicon flange and up over the flange to the edge of the hull mould itself. I then chopped up huge amounts of the strand and made my own chopped strand and then worked it in over the rest of the hull. I did several layers of this over the next couple of days.

                ​​​
                Once several layers of this have been put down It was time to think about the egg crate arrangement. This involved creating a wooden frame over the fibre glass to stop it from warping in the
                harsh Aussie sun in December. I learnt this the hard way a long time ago after making some glider wing moulds. I did'nt egg crate them and they warped soo bad. No hope of getting them back to straight. Anyway for this once again I use deep plywood side pieces and three transverse bulkheads to support between.

                ​​​


                Once this box has been created I simply fibre glassed over the edges and sides, making sure that the entire base of the plywood box is in contact and is glassed down to the hardback underneath.
                This is a very effective method of stopping warping.

                ​​​


                ​​​

                I left this for a couple of days just to fully harden and then all I had to do was split down in between the fibre glass and then splitter board and separate the top half of the mold from the mould box and start on the lower hull. This involved plastic spatulas and carefull prying. I could lay the mould down resting on the plywood egg crating, and have the board sitting on top. Then push down on the lower hull exposed on top through the base of the splitter board. Then pull the wooden mould box up. You just don't wan the hull top pull out of the mould. That would not be good!

                ​​​

                ​​​

                I am pretty happy with the results. I just need to grind off the sides, make them nice and neat and turn my attention to the lower hull on top.

                Enough for now...


                David H..

                Comment


                • David,
                  I do not see the pictures, you may need to reload them. Also, be safe! Fire is a scary thing.
                  peace,
                  tom
                  If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                  Comment

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