I could only find plans for the outer ring of the front centre vents online, so a bit of work was required to work out the plans for it myself. I also noticed a few discrepancy between the vents on the screen used R2 and the ones shown on some web sites, so decided to go with the screen used ILM version.
With the dimensions of the outer rim bit known, the various pictures I had of the parts could be scaled to those dimensions, and then the rest could be measured off from that. I also had several angled shots, and this is where I spotted the discrepancies, which I will rectify.
To start with I drew up flat plans to make the bits from. These will be made in styrene sheet then cast in resin, for durability. I first cut out the main parts, and then started on the gaps in the main plate.
When planning to cast something in resin, while making it you need to pay attention to the thickness of some parts, and how they will come out the mould. Itís no good doing super thin vent plates, if they wonít pull out the silicon. I prefer from a strength point of view, doing parts like this all in one. Therefore the vent flaps will need to be slightly thicker so they donít break when itís pulled from the mould. Doing it all in one is more complicated, but the finished item is much better.
So turning my attention to the outer ring, I made a wooden template of the inner dimension, which would allow for several thin layers of styrene to be wrapped and glued in place.
The first layer was glued and taped in place, as a base to work off. When this was dry three more thin layer were glued together, and then clamped in place, forming the familiar squared off oval. By gluing several layers together, when the glue is dry, it holds it shape perfectly.
Left overnight to dry, in the morning, the wooden middle section simply pushes out, leaving a perfect oval centre ready for the vent parts to go in.
With the centre grill bits glued in place final finishing touches like the slight rounding of the vertical edge could be done prior to it being glued in place. As this is going to be moulded, a bit of model filler was needed to make sure even the tiniest crack between joints was filled, if not silicon will flow into this and make it very difficult to get the part out the cured silicon.
With all the pre-mould pre work done, the last job was to slightly curve the outer edge to match the curve of the body. For this I have a curved section of metal set up with sandpaper on both sides, so things can be sanded to the correct curve whether it is an inner or outer curve.
The upper vent uses the same outer oval and the lower one, so that bit was easy to do, however the slats took a bit more work, to do. I found one lot of diagrams for making this, but after cutting them out in cardboard, they didnít fit together to well, and when compared with the angles on the close up shots of ILMís R2, they needed a bit of adjusting.
So I set to work on the vent flaps for the upper vent. I re-scaled the ILM pictures to the known dimensions of the oval, and then scaled everything to fit. As for the angles, they are easy to work out providing you know the length and width of the object.
Also as shown on the ILMís pictures when looking straight at the upper vent, the holes in the back are central to the vents, so I found it easier to print off a template and arrange the back plate onto that, so the vent slats lined up perfectly. The good thing about making a prototype to be moulded is adjustments can be made and re-made to get it right. Also styrene is much easier to work with than alloy, so where in alloy if its not perfect, another piece needs to be made which can take quite a while, in styrene a few minutes and cuts with a craft knife later, you have a new piece.
With the vent now finished a mould was made, and a resin copy cast. Due to how I made the mould no clean up work is required, just a quick wash in warm soapy water then a few coats of base grey, then a few more light coats of aluminium effect paint, and it was done. I am quite happy with it, and it came out better than I thought it might. When casting objects like this, there is always a chance the grills will be to thin and cause problems when being pulled from the mould, but with a bit of careful planning and casting, it came out fine.
With the inner vent panel finished and the outer case finally curved to the correct radius to match the outer skin, it was time to join them together. Being styrene a bit of careful application of model glue and they stick together just fine. As always with things like this there are tiny gaps at the edges so a bit of model filler is needed to fill them up, then a bit of sanding with fine wet and dry sandpaper.
When the prototype was at a stage I was happy with, I gave it a finally clean up, then made a silicon mould of it. As with any silicon used it should be de-gassed before use, but I always add a bit of silicon fluid to it so its slight runnier.
When set, the prototype is removed and a cast made.
So the final finished item, ready to go into R6. Being made from resin, you have to remember that if sections are to thin, they are not so strong, and also a possible air trap. As long as you remember when making it to make thin sections a bit thicker than if making it from alloy, the finished item will work and last just as long.
With a coat of primer and aluminium effect paint to finish it off, this which I thought was one of the harder bits to make, came out rather well.
Main Body Lower Vent
Main Body Upper Vent