Thursday, 2 May 2013

Stinger Build 07 - The End

Well had some fun casting the lead nose weight, tried a new technique, normally I just push the nose into wet sand to make a negative mould to pour the lead into, it works but the fit isn't brilliant. This time I used some plasticine wrapped in cling film to take a positive moulding from the inside of the nose, this was then set into some wet polyfilla and allowed to dry for 24h. I then carefully removed the plasticine to leave an accurate smooth negative in the now dry polyfilla. I had already weighed out my lead at 150g, so got out my little camping stove and an old sauce pan and melted the lead outside because of the poisonous fumes (wearing safety goggles and gloves as well of course). I then got a bit of a shock when I poured my lead into the mould as it immediately erupted flinging molten lead in every direction across the garden! Dam, fortunately I managed to jump out of the way and was OK, but it looks like the mould must have still had moisture in it, plus there is nowhere for the expanding gasses (i.e. steam) to go. Now I know why most casting is done in sand, it is because it is pourous and doesn't suffer from such dangers.

So I went back to the wet sand technique, I still had my plasticine positive which I used with the sand, re-melted fresh lead and this time everything went as expected, with a rough lead nose weight being produced which balances the Stinger perfectly. Lesson learned, don't mess around with polyfilla moulds, takes too long for an impatient builder like me. This means I will have to re-think how I am going to mould the wing joiner ballast out of lead, think I might try some wooden strips on a board next.

So the Stinger is ready to fly although I only have 600g of fuse ballast at the moment, good enough for a maiden though, hopefully get a chance to go up the hills soon. Although the Stinger has probably been the hardest mouldy I've ever built (only the 4th by the way) the resulting model is very good with a high level of stiffness, light weight and general shinyness. The controls are all solid with zero slop, it all fits together fairly well, the starboard wing needs a little fettling to line up the wing dowel. Nose cone is very tight fit, might even be able to get away without taping it on. Finally sussed out the new magnetic switch, works very well, like the bright blue light, it even shines through the white nose cone in dim light, although I doubt I'll be able to see it in daylight. There's a lot more finishing required compared to the Baudis Cyril I built last year, but once you've done the extra work, the quality is to the same high standard. Wouldn't recommend it for a first build though, ARTF it isn't!

Still now we'll have to get it dialled in and setup on the slope and hope it lasts a little longer than the Cyril. Stay tuned for the epic Cyril re-build, although I might just sell some stuff and buy a new wing instead, we'll have to see!

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