mtntopgeo

My Feedback: (12)

Not slimer powered, but I'm sure that this is the place where I can get pointed in the right direction. Bought a NITRO MODELS Cessna 182 " .15 & EP" ARF. Wanted to put an Enya .15 in it, but perceived worries about overheating, exhaust exit, & poor construction made me think about electric. A Tower Pro 2409-12, 25 amp ESC, & a choice of props, all for $19.95 made the choice for me. Terrific flyer & more than enough power, but very fragile. A bad hand launch, coupled with slow reflexes, & a set of dumb thumbs spelled the end for the wing. Fuse & tail feathers were salvagable, so I grabed a wing from a Neofun Vision, (about the same span, & cord) took out the dihedral, & added ailerons. Set it up on the Cessna with o deg. incidence. The Cessna wing had a very blunt leading edge, & an airfoil that I would call a Clark Y. The Neofun Vision wing has a near razor thin leading edge, & is flat bottom. Immediadetly after launch, the plane was a handful. Had to give it full down trim on the elevator, to keep it near level. Controls were very "twitchy", & the speed at "full throttle" was much lower than with the cessna wing. After two or three min. of fighting this thing, killed the power, & thankfully set it down. My guess is that the slow speed was from so much "down" trim (about 5+ deg.) that I had to put into the elevator. So here we are. Do I give up on this wing? Do I start putting in some neg. incidence? Or do I just start with another plane????????? George K.

rainedave

My Feedback: (1)

The sharper the leading edge the more pitch sensitive a plane will be. Next, the flat lower surface of a flat bottom airfoil is not the centerline, or, chord of the airfoil. So, you added pitch sensitivity and positive incidence to your model by switching wings.

Look at these images.

You can see the red chord (center) line in the top image and how the flat lower surface is at a negative angle to it. If you mounted the wing as shown in the lower image you will have a lot of positive incidence.

David

combatpigg

My Feedback: (3)

George, your plane should now fly like a Neo Fun Vision [whatever that is] if the wing loading and power is similar. Sounds like you need to raise the trailing edge of the wing and re-check the CG.
Let us know how you make out.

longdan

I had a neofun vision. They are a r/e high wing 1/2A trainer designed for .049-.061 Norvels and coxes. They actually used to be marketed by Cox and were called a Katybird or something like that. One of the few (possibly only) wood ARF models that Cox ever sold. It wasn't very fast and was very pitch sensitive, due to the short tail moment, and I expect, the sharp leading edge. Easy to fly once you got used to it, but not very thrilling. It had a foil something like the pic below.
I wouldn't have expected much improvement if I had hung a Cessna fuse underneath that wing, even with a .15 on the front. The wing loading would probably be pretty high.

Yuu

David and Combatpigg are correct back in posts #2 and #3. Read the thread on "Red Duck" where a simular incidence problem occured while mounting a wing on a canard. The "incidence line" on a flat bottom wing is NOT the flat bottom. Do a search and see the drawings in 'Red Duck' which are very simular to Dave3's info in post #2. Let us know how you made out.

mtntopgeo

My Feedback: (12)

Dave, Thanks for the illustrations. Looks like I'm my own worst enemy here. Once I got the Cessna fuse repaired to as close to original as I could, & set the Vision wing in place, it appeared that the wing had a 3 deg neg. incidence. SO, I proceeded to modify the wing saddle area so that I could read "zero" off the bottom of the wing.

CP, Your point ("your plane should now fly like a Neo Fun Vision") is well taken as will be explained in the next comment. Also , Yes, I will start shiming the rear of the wing. Why do I have the sick feeling that I'm gonna end up at - 3 deg. , as measured off the bottom of the wing, before this thing flys neutral????

Longdan, Yes the Vision was originally set up for a Norvel .061. I flew it with that power plant & the modified wing (no dihedral, & with ailerons. As you mentioned; Not very thrilling. I swapped out the Norvel for an Enya .09. The Enya, 3 OZ tank, & big battery ( to balance out the Enya) must have added a half pound to the bird. First flight was with a 7x5 prop on the Enya. The extra speed, along with the increasewd pitching effect was a mini heart attack, waiting to happen. 2nd flight was with a 8x4 prop. Things settled down, but the speed was about the same as with the Norvel power. Now I had a plane with the same speed, but weigh a half pound more !!!!!! This was certainly an example where "bigger" was not better. I had mistakenly attributed the pitch problem do to the short coupled plane . Didn't have a clue as to the razor thin leading edge of the wing having anything to do with the problem.

YUU, Thanks for the RED DUCK reference. Finding out that I'm even more ignorant about wing airfoil, & design than I thought I was !!! Much good info there to digest.

I'm gonna try to get this thing to just settle down & fly neutral It is becoming quite obvious that I'm not gonna duplicate the original wings performance.

Looks like Nitro Planes has quit listing the Cessna. Not only that, but every thiing else on the .15 size planes section has been listed as "SOLD OUT" for many moons now. Wonder if there is a hidden message here???

Well, thanks again for the help guys. Doesn't seem to matter, wether it's for Sure Start size, the bigger stuff, or even electric, Help is always available at this forum. ...................... George K.

combatpigg

My Feedback: (3)

Short coupled planes can be set up to fly hands off stable, they just have a narrower margin.
If the wing loading and speed is kept within reason, the airfoil doesn't make much difference.....not enough to ruin your fun.