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Tapered vs straight trading edge wing

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Tapered vs straight trading edge wing

Old 12-23-2017, 01:50 PM
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bentwings
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Default Tapered vs straight trading edge wing

I did a search but didn’t come up with anything. I’m sure it’s been asked before.

What happens when a wing is changed from a double taper...leading and trailing edges tapered toward the tip, to a leading edge tapered and straight trailing edge? Assuming the symmetrical airfoil remains the same.

All of my old pattern planes had straight trailing edges and tapered leading edges. These were from the days of rocket pattern.

I have plans for a neat old old school pattern plane but it has double tapered wings. I would like to make it single taper straight trailing edge. It’s a low wing very similar to the Dirty Birdy planes. This will be a sport plane just to fly for fun. No competition. I had a bunch of these planes and I really liked the way they rolled and the general smoothness that they flew. I simply have forgotten the old pattern reasoning for this. This plane also has a very long, slender fuselage similar to the DB and UFO pattern planes of old.

I’m sure the CG. Will change but I think that can be calculated pretty close for the first flights.

Thanks
Byron

sorry for the misspelling in the title.
Old 12-24-2017, 06:31 PM
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jester_s1
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A couple of things happen with a swept vs double tapered wing. First, as you've already thought of, the CG moves back. That may require/allow a longer fuselage. The big thing that swept wings give you is taw stability in turbulent wind. The effect i is a lot like dihedral that works both uoright and inverted but without the roll coupling or impact on knife edge performance. The straight TE also rolls a little better since trimming out the effects of aileron drag is much simpler. The downsides to a swept wing is less accurate tracking in loops and a resistance to yaw input. Old pattern planes existed with all 3 kinds of wings- straight LE, straight TE, and double tapered. The choice depended on which flight characteristics the designer wanted to emphasize or what undesirable quirks he wanted to remove from a previous design.
Old 12-24-2017, 08:13 PM
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bentwings
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Thanks for the info. This plane has a really long fuselage and relatively short nose so if the nose gets a little longer that’s fine.
the DB and UFO planes always flew great in the wind. Now that you noted yaw stability I remember them both wiggling the tails a little in stall turns and anything where lots of rudder was used near stall. Both rolled extremely well.

I have the option to go either with double double taper or just straight trailing edge. I don’t have any flight characteristics of this plane so I’m just going to go ahead with the straight trailing edge and be carefull on the first flights. I can always build a new wing. It will have flaps, ailerons, retracts and maybe spoilers. Smoke? Nah..too complicated for now.

This plane will be a hotrod, the aircraft version of my Streetrods. Lots of power and light weight and very clean. Mostly to be able to do things my warbirds could not do.
Old 12-25-2017, 10:45 AM
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jester_s1
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I can offer a comparison between an Intruder, Kaos, and Sweetater. The Kaos and Sweetater both have double taper wings. The Intruder has a slightly swept TE, so a bit more extreme than you are talking about. The Kaos and Sweetater are a bit more neutral handling with good yaw response. The Intruder resisted yaw input, requiring more rudder. But on a windy, turbulent day it was the best plane at the field. The others get tossed around, but the Intruder didn't.
Old 12-31-2017, 08:06 AM
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bentwings
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That’s interesting. I remember a lot of experimenting was done in the hay day of rocket pattern regarding wing platforms. There were a couple that even had slightly swept back wings. The Arrow had tapered wings but I didn’t really like it on windy days. The wind seems to be a constant here so I’m going to build this with a straight trailing edge. I layed it out on Soild works and it’s not as radical as I thought.

I should maybe make a new thread but this plane has a diamond airfoil horizontal stab. I only ever had one plane with this shape but it also had a full flying stab too so probably not exact comparison. It flew ok but pilot error made a spectacular mess before I really could evaluate it.
any opinions on this?

Byron
Old 12-31-2017, 06:24 PM
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jester_s1
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The venerable old Intruder had a diamond stab. It worked well and was easy to build.
Old 12-31-2017, 08:22 PM
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bentwings
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Thanks! I feel much more comfortable now.

byron

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