Aerodynamics Discuss the physics of flight revolving around the aerodynamics and design of aircraft.

1/4 scale schneider cup airfoil?

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Old 02-25-2010, 11:42 PM
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CarPainter
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Default 1/4 scale schneider cup airfoil?

I am building a quarter scale "American Mercury " a 1929 schneider cup racer. I am looking for an airfiol capable of 85 to 90 m.p.h., but but still be well tempered.

Any input would be helpfull.

Thanks
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Old 02-26-2010, 08:23 AM
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Default RE: 1/4 scale schneider cup airfoil?

A NACA-2412 or 2415 airfoil will work just fine. Use 1-2 degrees of washout.

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Old 02-26-2010, 10:53 AM
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Default RE: 1/4 scale schneider cup airfoil?

That will be a great model,what plans are you using?,can you post pictures of your progress?
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Old 02-26-2010, 01:53 PM
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Default RE: 1/4 scale schneider cup airfoil?

Boring, you should do the Pegna PC.7!
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Old 02-26-2010, 04:48 PM
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Default RE: 1/4 scale schneider cup airfoil?

The 2412 shown above would not be a bad option. If you know that you have trouble keeping the weight in check with your building and want to get some help on that front then the Selig 8036 is a little thicker but has a good reputation for carrying fairly heavy wing loadings with good grace. On the other hand if you know you are a light builder and can guarnatee a wing loading on the lighter side of this size of model then you could use a more racy airfoil with a little less drag such as the Selig 8038.
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Old 02-27-2010, 01:12 AM
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Default RE: 1/4 scale schneider cup airfoil?

Hi guys and thanks for the input.

I started into this project around Thanksgiving when I saw a drawing of the mercury on the french speedbirds site. I dug around for more drawings and was able to come up with one more pencil drawing but that's all. After awhile I decided what the heck, printed some big graph paper and started drawing. I have a fuse framed up (it may turn out to be a prototype), and I have the tail feathers in progress. I finished the float rib drawings last night so I may try to make some progress on them this weekend. I'm way over my head here but having a great time and learning daily.

I think the Selig 8038 will be out of the question for this project. The full scale had a weight problem and I'm sure mine will too. I will look further at the NACA 2412 and Selig 8036. Are there any freeware programs out there that plot these profiles?

Thanks again for the help. If I can get my act together I'll post some pictures in the floatplanes section.
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Old 02-27-2010, 08:52 AM
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Default RE: 1/4 scale schneider cup airfoil?

Hey Carpainter,

What level of scale are you going for sport scale or fully decked out with rivets and flying wires?
What type of engine are you planning to use?

I love to use Compufoil. The download is free and you can play around with different airfoils. But you have to buy it to use it to save and print out ribs. However you only need to pay for the features you want to use. So the price isn't that bad.

http://www.compufoil.com/index.shtml

I'm hoping to design a 1/3 scale sport scale Schneider Trophy model in a few years. It's going to be a fictional plane based on a Moto Guzzi design style. It will have full rivets, struts, and flying wires. I'm leaning towards powering it with a laser 360 V-twin engine.


Mitch
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Old 02-27-2010, 11:16 AM
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Default RE: 1/4 scale schneider cup airfoil?

Warlord

I am planing on doing a mid level scale job. The mercury was mostly wood so not to many rivetsbeside the ones on the cowel. It will have full flying wires and some cockpit detail. I would like to do more but I have almost no documentation.

Good luck with your Guzzi racer. My neighbor had a 750 LeMans when I was growing up. I always wanted one but never the money. Rice burners for me.

Bruce
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Old 02-27-2010, 12:17 PM
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Default RE: 1/4 scale schneider cup airfoil?

Profili2 starts off free with simple features and then costs you a measley $10 or $15 to open up all the features. www.profili2.com
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Old 02-27-2010, 12:36 PM
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Default RE: 1/4 scale schneider cup airfoil?

CarPainter,
I have been using a NACA 2315 on my last two scratch builds. It looks to me like the lift and drag coefficients are minimally different from the comparable 2400 series airfoils. But on the 2312 and 2315 the high and low points of the airfoil are both at 30% of cord. This makes for a very simple and efficient way to arrange the spars to build the classic model "D" tube wing. The high and low points of the 2400 series are not at the same % of cord. I can provide the coordinates of these airfoils for manual plotting or entering a CAD program to let the program curve fit. Photo of my Val with 2315 root airfoil. Just less than 2 degrees wing incidence. 14.3#, 7.8 sq ft wing area, 81" span. Only two flights since finishing in December, but it looks like it will be a very good model with excellent slow flight capability.
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Old 03-01-2010, 02:11 AM
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Default RE: 1/4 scale schneider cup airfoil?

I downloaded Profili this morning and played around with it for awhile. It looks like it will do everything I need for now. I looked for the NACA 2315 airfoil but I couldn't find it in the list.

I did find the find out that the full scale Mercury used the Curtis C- 62 airfoil It has a thickness of 8% and a camber of 1.92%.Pretty Zippy looking airfoil.

I got to a point this morning that I couldn't look at the computer screen any more and took my cub to the lake and flew for a couple of hours, The more I learn here, the more I realize I need to learn. The curve seems geometric. Now I know why people build kits.

Thank you again for everyones interestand help. Aint the the internet great.

Bruce

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Old 03-03-2010, 02:35 PM
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Default RE: 1/4 scale schneider cup airfoil?

ORIGINAL: AmishWarlord

Boring, you should do the Pegna PC.7!
We think alike! I recommended this aircraft to another on another thread. This could be 'doable' with modern electrics. Since I don't have the desire to invest in 'electric' I'll wait for someone else do it. The full-scale had some 'issues', however. Regards, ARUP
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Old 03-03-2010, 11:01 PM
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Default RE: 1/4 scale schneider cup airfoil?

I believe the Pegna has been done, and a while ago...the builder used electrics on the water prop to get it moving and up on the foils, a heli clutch and extension shaft on the ic motor (.60) to get the thing flying. Worked 'sometimes', but had problems on the transition between 'boat' and 'airplane'.
Evan, WB #12.
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Old 11-25-2011, 01:08 PM
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Default RE: 1/4 scale schneider cup airfoil?

Well my Snider Cup project just moved up a notch. I got a Enya VT-240 today.

Now to break it in, find a prop it likes and design a plane around it.

I seem to recall this thread being a few pages long. I know I posted a pic of a Moto Guzzi Motorcycle on here to show the paint job I'd like to do on my plane.

Oh well here it is again. [>:] Love the black with white trim and chrome accents.

I still like the idea of using that NCAA 2315 airfoil.

I thinking I'll use EDO rather than vintage pontoons on this one.



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Old 11-25-2011, 01:35 PM
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Default RE: 1/4 scale schneider cup airfoil?

However the Macchi M 67's floats look really sleek.
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Old 11-26-2011, 01:32 PM
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Default RE: 1/4 scale schneider cup airfoil?

build the thinnest wings you can which are strong enough and as light as possible-
That is exactly what the original full scale setups were -
The only reason for thicker wings -is that they are more numb to angles of attack
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Old 09-02-2018, 12:09 PM
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Default

I'd really like to know which airfoil you chose and see any pictures and info on the model you built.
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