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Old Dec 16, 2014, 05:04 AM
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Build Log
Amateur Building a EE Lightning

As a Christmas project I've decided to build a EE Lightning.

I chose this plane as it got quite a simple shape and I can mount the motor in the nose. And it's silver.

I'm new to corex but I have loads so I can make plenty of mistakes. I quite like how it's fallen out of favour and it's the underdog of materials.

First hurdle, there don't appear to be many plans. I built a Hans Jocaim spit and a p 51 many years ago and I think the same principles can apply here. I traced a 3 view in sketchup and printed it off for the prototype.

I'll hopefully start building this evening.

Cheers
Andrew
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Old Dec 16, 2014, 07:25 AM
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I think I will need around 1.89m2 of 2mm corex to build the Lightning. This should weigh with glue about 100g. I'm hoping the AUW will be 1kg. We'll see.......
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Old Dec 18, 2014, 01:36 AM
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I've been working on the design of the wing. It's going to be a wrap over. Each wing will be built independently so I can get the flutes travelling the right way. I'm experimenting both ways, across and with the chord.
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Old Dec 18, 2014, 07:07 AM
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What span are you planning? If you are sticking to the conventional parkjet dimensions of 600-700mm span, you want to target an AUW of 600g and hope that you eventually come in under 700g.

BTW, I assume that its just a typo in the second post....1.89m2 of correx is a very large piece and is going to weigh a lot more than 100g, given that 2mm correx weights ~330-350g/m2
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Old Dec 18, 2014, 11:01 AM
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I need to check my maths again. You're correct.

I see in your posts you talk about saving weight, I was surprised how easy it seemed to get there. I have over estimated with the 1.89m2 but I'm going back to the drawing board and will think about the design, strength vs weight.

The wing span will be 910mm, the length about 1200mm. The wing area is 2.8ft . This is a similar size to my Gauni Sea Harrier and GWS A4.

I'm enjoying the project so far, I forgot how interesting scratch building is, this being my first ever foray in to design is certainly getting the grey cells moving.

I've watched the first video in the Slope soaring thread, it was very helpful, I'll watch the others . I'm going to experiment with the flute direction. I see you favour with the chord, do you ever do it at 45 degrees? That would give an 90 degree difference with the lower skin.

Thanks for the help.
Andrew
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Old Dec 18, 2014, 11:40 AM
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I just did a quick sketch to get the areas and plugged them into my spreadsheet and your overall estimate of around 1kg is in the ball park and gives pretty decent wing loadings, so you should be OK at that wingspan. Airframe weight should be ~550g. The wing area seems to be quite high for a parkjet, so weight is not as big a deal as for some of the other designs (expect a CWL of around 6, which is nice and low).

Regarding the flute direction, a highly swept wing like this is just a delta with a triangle cut out of the back,....so I'd build it like a delta (e.g. Mugi Evo, my F16). That means the underside flutes run span-wise and the top flutes, once folded will run more or less chord-wise, and you will still get a decent profile. Then add a solid spar and some anti-crease strips on the inside of the upper wing skin and you should be fine. The only unusual thing in this one is the extreme sweepback...you will have to see if that results in it being too easy to twist or if it gives any unwanted washout/ wash-in.

Looks like you are having fun.

One other thing. Jim Beagle built a Sabre in the sloper thread and had problems with the highly swept wing's performance....might be worth chatting to him before you commit too much time to this one.
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Old Dec 18, 2014, 12:24 PM
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Thanks, I will, I saw pictures of the Sabre being built but I'm just getting to the bit where he flys it. It's almost like reading a book,

I was thinking also considering a KF3 or 4 aerofoil. It wont look right but for my first Spad it might fit the bill.
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Old Dec 18, 2014, 12:32 PM
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Quote:
Originally Posted by Andrew u.k. View Post
I was thinking also considering a KF3 or 4 aerofoil. It wont look right but for my first Spad it might fit the bill.
Don't waste your time - KF foils offer few benefits in correx over the simple folded one - no simpler, no lighter, no stronger and less aerodynamic. They make sense vs the default flat plate foam wing, but since the default correx one is already a nice airfoil, you might even be taking a step back going the KF route.
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Old Dec 18, 2014, 01:03 PM
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Cheers, I'll leave that then.
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Old Dec 20, 2014, 11:54 AM
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A bit more progress, I've redesigned the wing 3 times. I decided to remove the small bend in the leading edge. It was a lot of work, beyond my capabilities and after all it's meant to be a SPAD.
I have an external deflute on the leading edge and I'll run a bit of tape over it before covering in aluminium tape.
Pretty pleased with how its turning out so far.
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Old Dec 20, 2014, 12:14 PM
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I've used gorilla glue sparingly. I did some tests with it and seemed to stick right angles very well. I also used a bit of thick ca just to fix it all into position.

I've left the top skin over size for trimming later. I'm hoping to turn this up inside a little bit to give the sides something to stick to.
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Old Dec 30, 2014, 04:59 AM
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Some more progress.
As I build I can see where I can make improvements, this will just be the prototype.
The ribs have been cut as individual quarters so the flutes all travel diagonally out from the centre, I think this will probably be the strongest.
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Old Dec 30, 2014, 05:19 AM
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the air frame 480g so far. I'll be able to cut out a bit more from the horizontal deck.
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