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Old 01-05-2013, 08:58 AM   #1
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Default 84" EPS Lancaster Build

I've always wanted to build a four engined electric model and now I think I have the confidence to go for it after the 64" Wellington and 60" Hampden proved to me that two small out runners are perfectly capable of flying models of the that size so what size would four motors enable you to fly???
As with the previous builds the aim is to use very cheap 2" thick EPS wall insulation sheet for the build material with cheap spruce strip for all spars. Motors will be $6-00 HK outrunners !!
I looked at radial engined examples of four engined bombers as I have the cowl moulds and they are so easy to work with and I was seriously considering the Shorts Stirling but most of the nacelles on radial engined four motor bombers seem to be very short. Too short for me to fit my gear into anyway. Some even have the cowl sitting on the leading edge of the wing so not enough room there for my preferred set up.
Then I made a cowl for the Skystreak 26 / 36" build which proved to be close enough to a generic merlin engine cowl that I could mod it to represent the Lanc cowl without the chin rad which would not be possible to mould in one go anyway. The chin rad can be added later.( see attachments)
I decided to attempt to build the Lancaster in the end; due to the fact that the lovely long nacelles would, hopefully hold the motor, battery and ESC set up and would enable me to position the weighty components of the build well forward of the leading edge of the main wing and to cap it all I had a mould available for the engine nacelles...
I found an electric plan on Outerzone which was too small at 72"span; well the nacelles were and it was not much larger than the 64" span twin engined Wellington anyway.
To make the nacelles fit my cowl mould and battery requirements I scaled it up to 84" span and here is the resulting wing plan.(see attachments)
Now I had the wing (at least a full sized plan of it anyway) in my hands so to speak, I compared the nacelle to wing span ratio on the plan with a drawing of the Lancaster.
As you can guess the nacelles on the plan were too small and they actually need to be slightly larger which is great as the bigger the better for that area of the plan as far as I'm concerned.
Today I can make the main spar up as I have already bought the 12mm by 4mm spruce strip for the huge cost of 1-40 something.
It's a three piece construction with the flat wing centre section being one piece and the two out board sections the remaining two pieces.
I'll make up four plywood plates cut at the angle of the outboard wing sections and then use them to glue and clamp the whole spar together with the correct outboard angles set into place. The spar can then be used to correctly set the angles of the foam wing panels when they are eventually glued into place.
Next I need to find some 2" thick EPS foam sheet from the builders merchants which comes in 8ft by 4ft sheets so I'd better take a knife with me or I'll never get it into the car.
Somehow I have a feeling that this is going to be a very long build and it might not work but it is worth having a go at to see if a 7ft span four engined model can be built cheaply and lightly enough to fly on four $6-00 motors.

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