Doesn’t time fly when you’re having fun? I couldn’t believe it was time to put pen to paper again and update you on the projects loitering in the workshop. This month I thought we’d begin by looking, once again, at RDS and hidden controls. This was promped by a letter from a fan of the column… Yes, I know, startling isn’t it? I have a fan! Brian Knock sent me a package in the post, alongside an Aladdin’s cave of a letter. Inside were snippets of scale information that were very interesting to read, and also a couple of Swingees for me to play with. Now, you may recall that we mentioned these in the February column when we investigated hidden control surface actuation. Brian says the clear one (right) is from a model called a Sea Captain which, sadly, is no longer sold. The other came from Tower Hobbies, although, again, I can’t find any information about it and am unable to advise if they’re still available. If anybody has experience of these devices, do please let me know. Also included in Barry’s letter was an interesting picture showing a DIY Swingee (Fig.1) which I thought might be nice to share. If you have a go at making one, do please let me know how you get on?
Finally, Rob Bulk of RBC kits got in touch to say that he stocks a type of Swingee that’s made by Kavan (Fig.2) and looks very similar to that pulled from the Sea Captain. Interestingly, Kavan suggests that several Precision Secret Horns (PSHs) can be ganged together for larger models. If you’re interested, check out the RBC website at rbckits.com.
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LIGHT OF MY LIFE
The Hurricane landing light quest resulted in a flurry of activity on RCM&E’s modelflying.co.uk forum and produced lots of good ideas. If you don’t mind, I’ll skip over the suggestion that I stick silver tape over the wing leading edge, although if that floats your boat I have no problem with it. Not good enough for us ‘detailitis’ sufferers I’m afraid. Anyway, in truth, I’m having some difficulty with certain parts of the assembly and want to have solved the problems before letting you see it. However, I will give you a taste of what I’ve done to replicate the reflector, the leading edge ribs and the bulb housing. I’ve also sourced some great scale bulbs from a dolls house supplier in Bath. It never fails to amaze me what you can find with a little web surfing. Mind you, even though I’m thrilled to find these bulbs, they’re probably too long for the depth of dish I’ve made from annealed litho plate. The problem has arisen for two reasons. Firstly, I can’t get the lith to ‘dish’ enough and, secondly, the beautifully laser-cut light stand-offs are flat, and not dished upwards away from the reflector. The net result is that a scale size bulb will not fit between the stand-off and the reflector dish. I’ll have another go at the reflector before giving up, but it’s proving to be a bit of an obsessive challenge.
The light mounts, including the two visible wing ribs are made from litho plate, with the centre cut out lips being formed over a piece of ply with a suitably shaped hole. The tubing is styrene and the bolt heads are simulated using hex section styrene rod, sliced thinly. There are several suppliers of hex styrene rod and I have several sizes for just this sort of job. Meanwhile, the litho plate reflector dish was annealed several times and formed through a one inch hole in some thick ply, by rubbing gently with a rounded piece of hardwood dowel. The finished reflector was then polished with Solvol Autosol, a creamy metal polish, much loved by the bike and classic car fraternity. That terrific bulb stand-off is laser cut and produced for me by my good friend Steve Jarman. Having given Steve the artwork he duly set fire to several bits of ply, liteply, glass board, and even Perspex (I didn’t know you could laser cut Perspex!) before finding a material that would take being cut so finely. Thanks Steve.
I will keep at the lights and let you know how it goes, however if you want to join in with any suggestions the thread is still running on the modelflying.co.uk website.
For those who are reluctant to try this material, or are nervous of it, don’t be! Give it a go for it’s wonderful and so easy to use. I finally made the effort to get some from Sheffield Insulations having been told by a friend that it stocked the stuff, trouble is, I was never told exactly what the material was called. The actual purchase was slightly surreal and certainly made me chuckle at the time. Picture this: I walk into the Sheffield Insulations trade centre in Wolverhampton and eventually shuffle nervously to the front of the queue. I’m surrounded by burly builders with tool belts and steel toe cap boots enquiring about lorry loads of heavy building products. “Yes, sir?” says he. “Errr,” says I sheepishly, “I build model aeroplanes and…” With this the rufty-tufty builders moved a step further away from me and without letting me say another thing, the chap serving me grinned, reached under the counter and placed a block of blue foam in front of me. “You want this, yes?” “That’s the stuff,” says I, “do you get asked for blue foam a lot?” With this he laughed. “Yep, colleges, universities, schools, and modellers of all types.” Anyway to make a short story long, two large sheets were stashed in my car. The product name is actually DOW Styrofoam SP-X, code 21615. It comes in sheets measuring 2500 x 600mm and in two thicknesses: 50mm and 75mm. My bandsaw throat is not large, so I opted for the thinner 50mm. The two sheets totalled just £20 plus VAT.
So, what can we do with this stuff, and how do we use it? Well, I’m no expert but I will relate my brief experiences. Firstly, cutting it. I use a bandsaw, not because it’s a particularly hard material to cut but because this type of saw keeps all the edges true. You need to go carefully, mind, so as not to build up to much heat in the cut and melt the foam. Of course, there are other ways to cut the foam, including, believe it or not, a bread knife. I‘ve also been known to lop a chunk off the big sheet with a hand saw, but the chippings go everywhere! A hacksaw blade works fairly well, too.
Given that the sheet I purchased was 50mm thick, if I need a thicker block then gluing chunks together is the obvious way to go. Mind you, I’m still researching a good glue to use here, as it’s important that the easy sanding and sculpting properties are maintained across the join. I’m currently using epoxy so, at present, the way I get around this is to keep the glue well back from the surface that will be sanded, Trouble is, it’s hardly an exact science as you never quite know how much material you’re going to sand away.
For me, making a blue foam part begins by tracing a plan view of the bit I want to make on good old greaseproof paper. This is then cut out and the outline stuck to an adequate size piece of foam. The bandsaw then cuts the block more accurately. A second and third tracing is made of the side and front view, these attached one at a time and the bandsaw employed to create the rough shape. That said, in the case of the Hurricane radiator, the part was too large for the bandsaw and got hacked with a small hand saw. It’s at this point that the artist inside needs to surface. Now, be assured that I’m no artist, however with time and patience even my limited skills can produce something reasonable. I once heard that the trick to carving, say, an elephant from a block of stone, was to remove anything that didn’t look like an elephant. This is sort of the same…
For my part I start the shaping process with some rough 120 grit aluminium oxide paper attached to small bits of pipe, or rectangular blocks of balsa. The paper has to be sharp to cut the foam as opposed to rolling it off the surface and, as such, I’ve even resorted to the very gentle application of a coarse Perma-Grit block. But please, be very gentle if this is your weapon of choice, and switch to the much finer grades well before the final shape is achieved. The last stages are done with Halfords foam sanding pads as these are great for creating a really lovely surface. You need to be careful to avoid dinging the foam as it’s extremely soft. Nothing can really be done if it becomes damaged and you must either resign yourself to correcting the flaw with filler after the part is glassed, or make another and try to be more careful.
Don’t be afraid to start again, I tend to throw quite a few bits in the bin before I get one that I like. There is, of course, the possibility of applying filler to the foam and here I use a very lightweight and soft product: Red Devil Onetime Lightweight Ready Mixed Filler. This is just about the only stuff you can use on blue foam but, like the foam, it also needs glassing over to have any strength.
Once the final shape is achieved and it’s as perfect as you can make it, a layer of 25 gsm cloth will make the part really quite tough. You’ll probably be amazed how well the glass cloth will conform to the underlying shape if carefully teased down here and there. The carburettor air scoop in the accompanying pictures is covered in just one piece of cloth using L285 epoxy resin from Fighteraces.
Make sure you coat all the surfaces, external and internal with resin, even if you only use cloth on the areas that will get knocked about with general handling. There’s a good reason for this: I once sprayed a part I’d spent several hours making, only to find that cellulose primer rapidly dissolved it from the inside out!
To give you an idea of the weight savings you can expect when using blue foam as opposed to lightweight balsa, a friend built a traditional balsa radiator for his Hurricane as per Brian Taylor’s plan, and it came out at 40g. Mine, made from blue foam with a layer of cloth / resin and a resin flow coat came out at 20g. Quite a saving!
Loads of things can be made from blue foam, such as cowls, wheel door inners, canopy and spinner plugs and even entire fuselages. It’s a very useful material to have in your armoury. Another way of using this foam, which I’ll explain when we look at creating cowls, is to coat it in several layers of heavier glass cloth, then dissolve the foam from inside with cellulose thinners or petrol. This leaves a very nice light hollow cowl.
Okay, all this leads nicely to other Hurricane progress for not only is the radiator fairing and carburettor intake finished, the wings are glassed and they’ve been given a final prime. What’s more, all the blemishes have been treated to some 3M Red Acryl Stopper. If you’ve never seen Peel Ply used, my method of glassing a wing will be quite interesting so I’ll show you this in a future column.
If you’re a scale modeller you’ll already know that all sorts of challenges can present themselves during a build and, often, the way to tackle them isn’t immediately obvious. When problems arise I often leave them and get on with an easier bit while the old grey cells get to work. Eventually I find a solution and can go back to that section. A good example of this problem solving came in tackling the Hurricane’s foot step and hand holds which, for those who delight in such detail, were simulated thus:
Firstly, a hole was cut in the lith panel that was already attached to the fuselage. Now, this may sound easy, however the problem was how the hole might be cut without causing distortion to the thin litho plate? The answer was to use a very small drill bit and chain link the holes, after which a flat needle file could be used to carefully open up the aperture. On the full-size Hurricane, a small hinged (at the top) flap covers the hole and is pushed flush with a spring. To recreate this effect, I made the flap from litho plate, supported the upper part from behind using a small section of balsa, and angled the flap very slightly inwards at the bottom to give the effect that it hadn’t quite returned flush with the fuselage.
The hand hold is totally different in that the panel hinges outwards and is operated by pulling the foot step down. In a stroke of genius, I’ve even seen the footstep cunningly being used as an Rx switch by one modeller. Anyway, on my model the hand hold cover is made by cutting some lith to shape and laying it over a close fitting blanking panel. I’m fairly pleased with the effect and look forward to seeing the finished items in paint.This leads me to a question that I’m often asked: How do I cut litho plate so cleanly?
The answer is simple: Gently score the cut line once with a scalpel blade, then work the metal back and forth along the score until it snaps, which it does quickly and easily. In fact, you can even cut curves this way! Of course, some use scissors which, although successful, will tend to curl the edge of the plate. Others cut right through with a Stanley knife but you’ll find it slow going and it’s likely to murder the blade.
Right, that’s it from me for now. Remember, if you’ve got any questions or queries, you’ll find me on the forum at modelflying.co.uk.
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