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Old Nov 03, 2013, 10:56 PM
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Question
How much worse is an angled airfoil than a curved one?

I know it's going to be worse but how much worse is an angled airfoil than a curved one?

Or one with a curved front but an angled back.
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Old Nov 04, 2013, 02:38 AM
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A bit. Probably a little bit .

I.e. it depends exactly what shapes you're talking about, what you intend to do with them and particularly what speeds they should be working at.

Steve
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Old Nov 04, 2013, 04:47 AM
An itch?. Scratch build.
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Aerobat, try a Google Images search on, zedelsky airfoil

You should get a load of pictures, (that then link to web sites), showing variations on probably what you are talking about.
Some follow the upper surface curve, some have a flat sheet rear section.

As for the differences, that is a tricky one. There are probably some calculated or wind tunnel tests out there if you want to dig deeper, but for the size of models we build and fly, and at the flying speeds, I doubt you would notice much difference in flight.

That said, you would still need to compare like for like, (or very nearly a similar shape).
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Old Nov 04, 2013, 05:05 AM
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Ok so it's practical.
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Old Nov 04, 2013, 07:00 AM
gpw
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Yes... Practical !!! Years ago we used to fly planes with what was called a “diamond” airfoil , just two surfaces angled , no curves ( a ‘crude’ under cambered airfoil) ... That worked ... That later evolved into the “Jedelsky” airfoil .. and later on here into the flat plate airfoil ... so most anything will work really , some better than others , depending on the need ...
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Old Nov 04, 2013, 07:06 AM
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Yes that's the sort of thing I'm designing.

One idea, I have polystyrene flat block type shapes and I was thinking of making an undercambered angled airfoil by having two at the back and one at the front with and angled spacer between the first and second one.

Also does an symetrical (front to back) airfoil with the highest point in the middle rather than towards the front have any success at all? Or is it no good at all?
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Old Nov 04, 2013, 07:10 AM
gpw
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Got any drawings or pictures ? Curious !
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Old Nov 04, 2013, 07:12 AM
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Here

Name: polystyrene block configurations.jpg
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The blocks are from packaging originally so they are partly open at the bottom which I would have to cover with paper. So this makes them not very practical to shape into a smooth airfoil.

I want to make a very slow flyer. I really wanted to make wing sections out of the foam to cover with paper but it just wasn't pratical considering the blocks are open on one side.

I could maybe make some sort of v shape to attach to the front, but I can't quite think of how to create this yet. Maybe when I collect some more flat foam.
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Old Nov 04, 2013, 07:19 AM
yank and bank!!
Joined May 2013
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A significant percentage of model airplanes have wings that are a flat unshaped "board". Others are the same board with a curve bent in it that is visible from the side view. They fly decently enough.
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Old Nov 04, 2013, 07:20 AM
Build straight - Fly twisty
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At *our* sizes it is amazing what is practical.
Wings cut from 1/2 foam and left with a rectangular section. Looks like it shouldn't fly, but the vid shows does. Quite well too. Huh?
Wings with CF rods taped on top and bottom surfaces. Looks like the lumps and bumps would destroy the lift. The wing, in fact, performs well. How can that be?
An alleged KF wing with steps on the leading edge as well. Looks more like an Aztec pyramid than a wing section. Flies fine. Unbelievable!
A model with a Clark Y wing section flying inverted. Think about that one. A promo video for a Super Cub shows it handling inverted flight with grace and style. Am I seeing things?
The list goes on...
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Old Nov 04, 2013, 07:24 AM
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Yes it's very interesting it's good to think I can really use some of the materials I have without making a perfectly ideally shaped smooth plane, so what do you think about the second configuration there where the airfoil is symetrical front vs back (made from two blocks only), except for the angle that it is attached the the fuselarge?
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Old Nov 04, 2013, 07:29 AM
An itch?. Scratch build.
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Aerobat, also try a Google Images search on, airfoil section.

It will give you some idea of the enormous number of airfoils that are available.

There is the airfoil shape based on set of upper and lower coordinates. Then you also get the variations of thickness, (usually referred as a percentage).

If you are slightly interested, (or anyone else), in airfoils, have a look at this site, (one of many available) -- http://www.mh-aerotools.de/airfoils/

On the left there are some links to different types of airfoil for different flight requirements. Some will link to the actual airfoil number, showing characteristics, a picture, and coordinates for construction. Worth just having a dig through to give some idea of what is involved.

Airfoil design is quite a complex science. Luckily as modelers, we can produce just about any shape and get it to fly, but, to fly to competition standards does take a bit more effort in getting it right.
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Old Nov 04, 2013, 07:38 AM
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Here are my materials and some possible configurations.

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I do have a larger size of block that is bigger in all dimensions so I could also possibly experiment with a KM airfoil as someone said in another thread but it would require more materials because I can't really have a massive block at the front, it would be like a tiger panzer. I would probably have to get some flat foam to make a < shape leading edge.
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Old Nov 04, 2013, 02:07 PM
Build straight - Fly twisty
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Australia, QLD, Little Mountain
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I'd rate those in order of preference:
3
1
2
KF wings are easy to build from thin foam, and they fly OK. Making them from thick foam is not worth the effort.
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Old Nov 04, 2013, 04:36 PM
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Quote:
Originally Posted by RC Aerobat View Post
Here are my materials...
honestly i'd tkae those foam blocks for cutting wing ribs, then do a conventional wing build with spruce saprs or similar and cover with tissue, film or whatever.
I really like your "recycling" idea of some scrap foam...
Mabe this pic helps to understand what i'm talking about:

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