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Old Dec 01, 2005, 01:17 PM
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dpoles's Avatar
United States, NY, Ithaca
Joined Oct 2001
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Pattern/3d airfoil?

looking for a good airfoil biased towards pattern, but with 3d capability.

For a 35" ws scale aerobatic ship.


thanks
David
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Old Dec 01, 2005, 01:41 PM
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theKM's Avatar
central PA.
Joined Sep 2004
20,206 Posts
3D is mostly thrust, throws, and control surface area. If have large amounts of all these, the airfoil isn't all that big a differentiator. Only airfoils that will really help is a fair bit different, and that's a high point that is very far forward that will help keep the airflow attached to the wing for longer when you go to higher alpha.

...we also need to say that at these reynolds numbers, there's very little difference to an airfoil wing and a flat plate... so just go with the pattern airfoil and the "big three" I mentioned at the start of this post.


Just check out the airfoils on the StevensAero beasts. They're pretty capabel flyers.


It does also sound like you want to have and eat cake at the same time
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Old Dec 01, 2005, 01:48 PM
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United States, NY, Ithaca
Joined Oct 2001
2,142 Posts
Ahhh...but what is a good pattern airfoil?

I do not want to build a flat plate 3d plane, I have 2.
I would like to build a pattern plane(see above: biased towards pattern) that will do "some" 3d. Steven's Aero and Mountain Models are exactly what i am thinking of, unfortunately neither make a Sukhoi.
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Old Dec 01, 2005, 04:17 PM
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Ottawa, Ontario, Canada
Joined Aug 2004
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I scratch built a 36” Giles using an Eppler 168 if I remember correctly, and it flew great. I still have the plans on my computer at home, so if you’re interested, I can confirm that that’s what I used (and/or send you a copy of the plans if you want more inspiration).

Another option is to download the manuals for similar aircraft. Some of them, especially kits, often have 3 views with accurate airfoil sections. (Stevens Aero Groove, G-ride, maybe Dystraction come to mind). If you’re CAD-ding, you can always import an image of the airfoil you want, do some tracing with splines, and run with that.

At the small scale and low speeds, the fine details of the airfoil become less critical. One could probably simply draw an ellipse and taper one end using the TLAR method and have a nice flying airfoil. However, quoting an “official” airfoil number always makes you look smarter at the flying field

Tom
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Old Dec 01, 2005, 10:47 PM
Registered User
Colorado Springs, CO
Joined Oct 2004
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I have also used the Eppler 168 airfoil on a pattern ship of my own design and have been very pleased with it. I used its companion, the 169, on another design with similar results. The difference is the thickness, about 12.5% for the 168 and about 14.5% for the 169.

Both have essentially a straight taper to the trailing edge, so you have a good chance of building the wing square without having to go to building tabs and the like.

Good luck!
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Old Dec 02, 2005, 08:33 AM
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United States, NY, Ithaca
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Thanks, just what i needed. I would love a copy of that Giles Tommy. I love looking at plans and getting ideas for my own designs and I will probably add that to the loooong build list too!!

I am drawing in Cad
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Old Dec 02, 2005, 11:00 AM
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Ottawa, Ontario, Canada
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Here you are. (Happened to find the email from a year ago where I emailed the PDF to myself at work for printing on the plotter here).

As you can see, there’s not much detail on the plans. Being a scratch build, I like to get the basic shape on paper, and figure most stuff out as I go. I recall the main spars being some 1/8th inch square spruce I had lying around from an old kite. Ribs were 1/32nd balsa. The canopy was carved out of some white Styrofoam, and the canopy/forward fuse was removable as a hatch to get at the batteries. For the fuse, I built up two copies of the side view, and then pinned them to the top view and built a truss framework between them.

I originally had a geared Speed 480 in it (shown on the plan), but it didn’t quite have enough oomph. Eventually went to an AXI 2808/24 and the model really came into it’s own

The DWG is on my home computer… I’ll see about adding it to this post when I’m there.

Tom
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