Unexpected Snaps!

[crashdummy6]

I have a question, hopefully a confirmation of something I think anyway.

A snap in a tight turn. I have noticed on a simulator, the bigger, heavier planes seem to be more prone to snap in a tight turn than do the lighter wing loaded planes. I think this might be because of the higher angle of attack and the fact that the lower wing is moving somewhat slower than the upper wing. So it stalls and snaps under toward the low wing. Is this a correct assumption or am I way off?
Thanks

PS. I ask this because I am in the process of an 83” Midwest at6 kit. It says in the manual this plane is prone to that so not to go above the recommended throws on the elevator. Which I usually do. I like a lot of elevator for landing and hate running out of authority 3 feet off the ground. Probably has more to do with my flying than the plane setup though.

[Karl B²]

That sounds about right. A plane can also often snap roll out of a loop, often at the top when the airspeed drops.

If you limit your elevator throw so that it won't throw a high-speed stall, you may not have enough at landing. Some kits have very good throw recommendations, though I have no experience with your craft.

If all you're going to do with your plane is pylon racing, it's probably a good idea to limit your throws. For aerobatics, you'll want to have the ability to snap, and will have to learn to meter your stick throws when you don't want that highspeed snap.

[crashdummy6]

I won't even be doing those things. I will be doing more scale like flying, or crashing, whatever the case may be.
Thanks

[Sparky Paul]

With the T-6, you MUST keep the speed up higher than usual for a sport plane, on both takeoff and landing.
These are not floaters, and the tip-stall is always lurking.
Land on the mains, not 3-points and you probably may have the plane around for awhile.

[crashdummy6]

I am thinking of adding flaps. Not too sure if it will be worth the trouble, and/or how effective they would be. The kit does not call for them, but i do not think it would be TOO hard to add some.

[Sparky Paul]

The T-6 uses split flaps, which are easy to do.
And they add a lot of drag..
But you'll still have to watch the speed on landings..
Power needed would be higher than without them.

[Checksix!]

That kit should specify a given amount of washout on the tip panels, given the dihedral break on a Texan. It should be around 1 degree leading edge down or block up the trailing edge about 1/16th" prior to sheeting. Another thing that delays stalls of all kinds is keeping the leading edge radius as sharp as possible.
By the way that is an excellent flying kit, I used to race them in a class of all Midwest Texans with 1.20 four strokes. Just keep some speed up on landing and it's a pussycat


Dave

[Karl B²]

Another thing that delays stalls of all kinds is keeping the leading edge radius as sharp as possible.
Do you have that reversed, or am I misunderstanding? I thought that a sharper LE stalls at a lower angle of attack.

[Gary Warner]

Do you have that reversed, or am I misunderstanding? I thought that a sharper LE stalls at a lower angle of attack.

I noticed that too. LE should be rounded for 'soft' stalls. Now, to help 'tip' stalls, a sharp LE should be added to the wing root (like triangle stock added to LE) aka, stall strip.

Gary
--

[crashdummy6]

Do you have that reversed, or am I misunderstanding? I thought that a sharper LE stalls at a lower angle of attack.
He may be right as stated. The leading edge being sharp would cut down drag. He didn't really say thinner wing which I think has less lift than thicker wings. But, all things being equal, it would seem a sharper LE would "cut through" the air easier thus reducing drag which should help prevent a stall?.?.?..

Not sure though, just guessing :confused: .

[Karl B²]

In the case of a stall, the wing is pushed to an angle of attack where it's unable to maintain laminar, or smooth, airflow. The blunter the leading edge, the less it will tend to disturb the flow at these angles of attack, delaying the stall.

[Pinecone]

On full sized planes you will will see "stall strips" added to ensure that the root area stalls first. These are short (4 - 6") pieces of triangle stock attached to the leading edge. The sharp edge induces the stall at lower AOA than the blunter normal contour.

You could do the same thing with a model. Short pieces of triangle stock on teh leading edge about 1/4 the way out from the fuselage.

[Checksix!]

Yeah, it should have been leading edge radius as LARGE as possible.
Brain fart I suppose

[portablevcb]

The root of your question is 'how to build it so it won't snap' or 'how do I fly it so it won't snap'? Either are addressed above. But an easily snapping plane is more desired by the aerobatic guys than the scale guys. With warbirds I have trouble with pulling out of a loop if I don't pull power way down. Also, sharp turns (bank hard, yank the elevator) tend to expose a snapping tendency (do it up high the first few times to get a feel for it).

If you use a computer radio you can program in high and low rate for the elevator. Use high for landings if you need to. I've found that I rarely need it if landing with a conservative speed margin. As was said previously, wheel landings are almost required (there are exceptions) on planes with higher wing loadings.

I like washout in the wingtips to offset the tendency to snap. It also keeps the ailerons working a bit better in slow flight.

charlie