Stall strips vs. Washout

Stall strips are used to fix a design shortcoming. No engineer
wants to design a wing that stalls sooner than absolutely necessary,
but some wings didn't behave as predicted and the stall strip was meant
to induce stall on the inboard wing areas and get the nose to drop
before the ailerons lost authority. The Tomahawk has a reputation for
some nasty stall/spin behavior, and I imagine the stall strips were
meant to alleviate it somewhat. The Bonanza has them, too. With newer
computer-generated airflow modelling it's easier to spot deficiencies
before the wing is built.

"Kyle Boatright" wrote


Like I was trying to say last night, the AA-1 and Tomahawk both have
hershey
bar wings and stall strips.

KB

The AA-1 had them more to make the high speed stall more noticeable, as I
recall reading , somewhere.

The AA-1 was hot little number, for that HP, and people changing to it from
slower designs could have hardly ever have produced a real mean high speed
stall in their earlier planes, as most other designs of that HP and period
were close to 50% slower.

The stall strips were there to get the pilot's attention, earlier, before
they got into trouble.

Or so I recall reading.

Tomahawks just were nasty to handle in a stall, because of the T-tail way
out of the prop blast, and they need to stall earlier to keep elevator
control? I'm guessing about that one, just from what I have heard.
--
Jim in NC

On Mon, 21 Feb 2005 17:42:36 -0500, "Morgans"
wrote:


wrote in message
roups.com...
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.

I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section, with the tips remaining flying to
the end. They are not as efficient at high speeds as elliptical or tapered
wings, but that is seldom the mission of planes that have constant cord
wings.

The old "Hershey Bar Wing" Cherokees are the only planes I've flow
that I could put into a stall, keep it in the stall, and still make
turns using the ailerons. Many airplanes don't like that and in
particular the Bo series of planes are likely to roll over with which
ever wing you try to raise going down instead. It's amazing how fast
they can put the greasy side up.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

In article ,
Roger wrote:

On Mon, 21 Feb 2005 17:42:36 -0500, "Morgans"
wrote:


wrote in message
roups.com...
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.

I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section, with the tips remaining flying to
the end. They are not as efficient at high speeds as elliptical or tapered
wings, but that is seldom the mission of planes that have constant cord
wings.

The old "Hershey Bar Wing" Cherokees are the only planes I've flow
that I could put into a stall, keep it in the stall, and still make
turns using the ailerons. Many airplanes don't like that and in
particular the Bo series of planes are likely to roll over with which
ever wing you try to raise going down instead. It's amazing how fast
they can put the greasy side up.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


The old Meyers 200 was another plane that you could hold in a stall and
rock the wings with the ailerons without falling off into a spin. It
also had about 3 deg of wing twist.

Some aeroplanes have stall strips just to give stall warning, by make the
h-tail vibrate from the turbulence.

some Hershey-bar wings have twist to improve its handling.

most all taper wing have some washout in form of twist or aerodynamically or
a combination of the two.

aerodynamic washout can be achieved by using an airfoil at the tip with more
camber, or more nose camber (drop nose)

Messersmith was probably one of the first to use a combination of twist and
a more cambered tip airfoil, it is made so the zero-lift line at tip have a
small amount of twist compered to the root airfoils zero-lift line, the cord
line have then a larger amount of twist. At high speed the tip will not
produce negative lift due to the small difference in zero-lift line.

Jan Carlsson
www.jcpropellerdesign.com