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Wing section help

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Monz09/08/2019 21:05:11
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Busy planning the next build, a quarter scale BF109 E4, and a bit stuck on which section to use.

I'd like something semi symmetrical to keep the lines between the fus and the wing. The Matt drawing says its similar to the NACA 2315, but that looks a bit thick for the slope.

Would the E374 thickened up a bit be ok? Any other ideas?

Thanks.

Andy Blackburn09/08/2019 21:53:44
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Posted by Monz on 09/08/2019 21:05:11:

Busy planning the next build, a quarter scale BF109 E4, and a bit stuck on which section to use.

...

At 1/4 scale (!!), that's about an 8.14 ft wingspan and an average chord about 1.32 ft; that's pretty big. However, I'd be inclined to stick with a bona fide slope soaring wing section because the problem with very large models that have thick wing sections is that they're often relatively light, so often end up being a little bit slow.

If it was me I'd go for the thickest available proven PSS section (not a lot wrong with E374, but I seem to remember reading that RG15 is designed to work even when thickened up quite a lot, possibly as much as 15% but I could be mistaken), mounted at a reasonable angle on the fuselage with possibly a bit of artistic sleight of hand at the wing root. And washout, of course...

HTH

A.

Peter Miller10/08/2019 08:53:22
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I really like NACA3414 or 2414. They are flat bottomed from the spar back for easy building but work just like symetrical sections These are 14% thick and I use them on most of my designs.

Peter Miller10/08/2019 09:29:12
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Actually I just had a look at my compufoil and NACA3412 looks better as it would be thinner for the size that youare working with

Alan Gorham_10/08/2019 11:12:57
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I'm no expert so I can't offer you any advice, but Andy Meade's Hawker Typhoon is 1/5 scale I think and built from a powered kit. After seeing it fly at the Lleyn PSSA event in June I'd question whether you need a specific "slope" section. The Typhoon has a thick semi-symmetrical section so yes will be draggy but the model carried enough momentum to fly like a tankbuster.

I'd probably say don't build the Me too light!

Martin Harris10/08/2019 14:17:00
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Interesting observation. The designer of my current (rather long term) build has stated that his original Tempest, built to comply with the then current 5kg limit for scale comps was nowhere near as good a flyer as a much heavier second version that he built at 7kg - and that was not as good as a customer's model with a Quadra Petrol at 10kg that he test flew!

Monz10/08/2019 15:44:10
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Thanks for the help guys. Having a play around and the NACA 3414 (assume you meant that Peter?) fits almost perfectly at 2°.

Alan Gorham_10/08/2019 16:30:46
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Just checking that everyone appreciates we are talking about a slope soarer here and not a power model.

PatMc10/08/2019 16:40:17
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The Bf 109 was 14.8% at the root but down to 10.5% at the tip - ref 4th page down this document, I think Paul Matt's referring to the same ultimate source but AFAICS he's missed a "0" out, it should be this NACA 23015 at the root ? Which would give a nearer to symmetrical section only 1% thicker than NACA 2314.

Martin Harris10/08/2019 17:04:39
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Posted by Alan Gorham_ on 10/08/2019 16:30:46:

Just checking that everyone appreciates we are talking about a slope soarer here and not a power model.

That explains the reference to being a bit thick for the slope which I took to be some sort of muddled reference to its angle of attack!

Monz10/08/2019 17:12:18
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Posted by Alan Gorham_ on 10/08/2019 16:30:46:

Just checking that everyone appreciates we are talking about a slope soarer here and not a power model.

Correct! This'll be a glider, in a very loose sense of the word!

Peter Miller10/08/2019 18:43:38
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Posted by Monz on 10/08/2019 15:44:10:

Thanks for the help guys. Having a play around and the NACA 3414 (assume you meant that Peter?) fits almost perfectly at 2°.

Yes, NACA 3414. It would seem that they had modellers in mind when they designed the 109.smiley

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