Rob Ashley
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Everything posted by Rob Ashley
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Hi Tim, I won't offer advice about the power/weight ratio for electric as I don't feel qualified. But you should be proud of your plane - it's a cracker. Well done you. Rob
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Hey Tom, Glad to see you are still keen - welcome to the hobby. Rob
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Hi Derek, I made a couple of these: They are quite universal, very stable and light. Fold away flat too. Best Rob
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Nicely said BEB.Edited By Rob Ashley on 05/02/2018 18:15:34
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Tom, There is nothing wrong with continuing to build your own plane if that's what you want to do. Years ago this was the only route to go, but there are now other ready made models on the market that make your journey to successful flight a little easier. Perhaps it is better to build yours in the background whilst learning to fly on a 'known' platform. By this I mean one that has already flown and is trimmed and balanced correctly - there are plenty of trainers out there and some clubs even have a club trainer. Learning from someone else will reduce the time it takes for you to learn the basics and give you more smiles per £ spent. I'm like you and want to know everything all at once, but in this hobby there is a multitude of information out there (not all good or indeed correct) and it will take a lifetime to acquire it all; but there are things that are more important to know sooner and this is where an instructor can help. A lot of people have commented here all trying to offer help and it can be daunting to assimilate all of the advice given, but don't let that put you off - one of the best things about this hobby is the amount of help available. Rob
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Peter, I'm feeling a little more confident about the power train I have picked - I 'spose I can always add a bigger motor if needed, but to know she will fly on 1 engine well is comforting. I must admit the belt sander made a huge difference to the proceedings, as did the bench disc sander when I could keep my knuckles away from it... takes off skin quite quickly, so it appears. I think I would loose my fingers if I used a power planer.....
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Hi Tim, That really does help - thanks. It gives me a little more confidence in what I am doing. I bought 2 x 430 Watt motors and assuming a 7lb model will give me 122.8 Watts / lb. So theoretically there is a little spare power if the weight comes out a little higher. This may also be slightly overpowered which should mean lower throttle and longer flight times. Only flight testing will see.
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Richard, A fellow CNC'er. I agree with you that most of your time is spent digitally drawing the plan before you can machine it. I guess the real advantages are accuracy of the kit you make and once the drawings and cutting files are made you can re-produce as many as you like. I made 2 GTC kits (shown in my GTC thread) - the second for a mate. I really enjoy the whole process of drawing to machining and view it as another side of the hobby to enjoy. I didn't put jig tabs on my ribs by the way and I have kept my nose as per the plan (although scaled to 68" span). Best of luck with your build. Rob
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Right - Canopy time. I made a plug from some pine I had lying around and cut the outline shape on the bandsaw. A quick tickle with the belt sander and some hand sanding produced this. I tried the plastic bottle method and spent ages trying to shrink it with an old hair dryer. Realising this wasn't cutting the mustard I let rip with a paint stripper. MUCH better. I melted the very end of the plastic on my first run but will have another go tonight. Couldn't resist a dry fit of components.
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Very true Peter - my forays into electric so far have shown that electric is more expensive to start with. I guess my thoughts to change were based on frustration with loosing a really nice IC engine. I have bought 2 motors and ESCs with plenty of capacity in the ESCs to upgrade the motors if I need some more thrust from a larger prop. Although I am tempted to buy some SC engines I think I will stick to electric for this model - it was always intended as a very nice test bed for my in progress BT Mosquito.
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I guess my next question is when the manufacturer quotes a max amps for the motor that means that is the max the motor can draw safely?
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Hey - thanks Peter, Destiny is on my to build list. Quite far down at the moment but it is on there. Is there anyone who can check my calculations/guesstimations for an electric conversion? Please? My GTC version is 68" span with tgt weight of 6 1/2lbs. I was going to put in 2 x OS 32s (until one of them blew a cylinder liner) and OS claim the output is 1.2hp (!) at 18000rpm and props from 9x6 to 11x6. A good starting point of 1492 Watts or 229 watts per pound!?. Seems excessive. Going another way and using 120 watts per lb for sport aerobatics gives me 6.5x120 = 780 Watts. A little more than half I would have had from the IC engines. As this is a twin I can divide the power between 2 motors and plumb for 400 watts of power. If I buy 2 motors that can deliver a max of 665 Watts each and a max of 46 Amps (from the manufacturers specs) but that would be 60 Amps on a 3S. But that watts would be determined by the prop and voltage of the battery wouldn't it? I am thinking of buying two motors that have 1250kv which would drive a 10x6 prop on a 3S battery (13,750 rpm) or alternatively a 790kv motor that would turn a 12x12 prop at 8690 rpm. Any thoughts or suggestions gratefully received - I'm getting bogged down in the choice available to me.
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A few evenings later I managed to put the remainder of the bulkheads in got a little further. Then it was onto planking. Now I'm not really a great fan of it but I do agree with Peter Miller that it can be therapeutic - but for me that's only when it goes well. I'm reasonably content with the result so far - just needs some sanding.
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I managed some progress this week. After putting the wings aside whilst giving the propulsion problem a stern head scratching I cracked on with the fuselage. The CNC'd formers fitted perfectly and were a pleasure to build with, just needing cyano for the balsa ones and epoxy for the 2 ply ones that take the stresses of holding the wing in.
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