Whose airplane is it anyway?

Peter Dohm wrote:

I don't know the reason, but every delta winged aircraft that I can recall
ever having seen pictured has had a pronounced nose high attitude while at
rest.

From that observation, it is easy to infer reasons--and, of course, to be
wrong!

If anyone here actually knows the real reason, please post it. (Inquiring
minds want to know.)

Peter



You have to get the nose off the ground if you're going to put a prop
out there.

"Peter Dohm" wrote

I don't know the reason, but every delta winged aircraft that I can recall
ever having seen pictured has had a pronounced nose high attitude while at
rest.

From that observation, it is easy to infer reasons--and, of course, to be
wrong!

If anyone here actually knows the real reason, please post it. (Inquiring
minds want to know.)

Delta wings don't really stall; they go into a "mushing flight" mode. That
is why they can land with the nose way up. To get slow, they need to get
the nose up. Also, the maximum lift coefficients are the highest with a
large angle of attack.

Taking off, the nose high attitude lets it "fly off" the runway when a
decent speed is reached. They would need to go very fast to bring the nose
up from a level attitude, because the elevons are not way back there on a
fuselage with a long moment, like standard wing plan forms. Without the
long moment, the elevons need all the help they can get, initiating
rotation, and the nose high attitude does just that.

You may have noticed that delta wings with a big canard (Mirage,
Eurofighter) do not have such a nose high attitude. The canard provides the
long lever (moment) needed to rotate the wing.
--
Jim in NC

Add to that:

http://www.aerodyn.org/Wings/larw.html

The high alpha is a side effect of low aspect ratio wings.

Richard

On 18 Mar 2007 16:10:20 -0700, "Lou" wrote:

Isn't this the same problem that the sonex builder
had putting in the corvair engine?

We have one (Sonex) on the field getting a VW engine and no one's
complained about that so far.

His is flying.
Lou

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

On Sun, 18 Mar 2007 23:25:24 -0400, Ernest Christley
wrote:

Richard Isakson wrote:
"Richard Riley" wrote ...

Well, do check with them for your own peace of mind, but there ain't
nothin - and I do mean nothin - that he can do. It's faintly
theoretically possible that if you include his name in the registered
name type of your airplane he could have grounds to sue you, but it's
never happened and probably never will.

Just to be on the safe side, call it something else when you register
it.

Frankly, the big change that needs to be done to your airplane is it
needs fixed main gear and a lower ground attitude. One man's opinion,

Yet, as Lieutenant Edwards found out a great deal of care must be taken when
you're dealing with changes in the center of gravity of flying wings.

Rich



I've taken painstaking care not to move the CG or change the airfoil,
sweep or angles of the wings. I have made the nosegear fixed. That

Lordy, When I flew Jack Yoder's Barracuda, there wasn't much he hadn't
changed and it flew well. The wind root sections that contain the gear
were modified to symetrical air foild as he went to wide profile tires
for dirt strips and the root thickness wasn't enough to hold the
wheels. I'm not sure if he moved the wing a bit on that one due to CG
of not. If the CG falls in the correct place on the wing it's usually
considered a good thing.

OTOH he put a 260 HP 6 on a GP4 designed for a 180 HP 4. It was a fun
air plane to fly. It took some doing with no break out force or stick
gradient in pitch. Roll forces were just fine. He had moved the wing
but it could still end up in an aft CG situation. Tiny tail and aft
CG is not a good combination.

saved me 10lbs, lots of complication, and several failure modes. It may
cost me a couple kts, but I consider them kts well spent. If I knew
then what I know now, the main gear would be aluminum leaf springs.
There's lots of weight in the gear retract mechanism, but its fairly
evenly spread forward and aft of the CG.

As for changing the ground attitude...you've got to get it high enough
to put a prop on there. I do have less than 9 degrees nose-up, which is
the limit. It's just under 8, if I recall correctly.

Much nose up attitude when on the gear can make for some interesting
take offs in *some* planes.

Actually in some areas we have a lot of leeway and onthers very
little.
On some planes you can move the wing fore, or aft to fine tune the CG
with no problem and on others the change in coupleing can be
pronounced.

Any time you change something from the original design you may end up
in untested territory, unless it's a popular mod.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger wrote:

Actually in some areas we have a lot of leeway and onthers very
little.
On some planes you can move the wing fore, or aft to fine tune the CG
with no problem and on others the change in coupleing can be
pronounced.

Any time you change something from the original design you may end up
in untested territory, unless it's a popular mod.


Bingo, Roger.
It's important to know what you don't know. I don't know enough to
predict what will happen, and don't want to take the time to do the
proper experiments to find out. The wings on a Dyke Delta aren't easy
to adjust. Impossible really, as it would entail rebuilding the entire
wing. The stall progression on the swept delta wing is also different
than a conventional wing. Lots of variables. Just enough knowledge to
know the variables exits. Leave well enough alone, I say. 8*)

As for switching the engine, there's a decade(s) of flying data that I
can dig into and feed off of. Maybe I'll learn as much about
aerodynamics and structures and design my own delta some day, or maybe
I'll finish this one and have enough fun to forget about it. 8*)

All the designer can do is send you certified mail, and all its good for is
covering his six if you buy the farm in the airplane you built in deviation
from his plans, etc. There's nothing he can do to stop you from flying it.

"Ernest Christley" wrote in message
...

I have just been informed by the designer of the aircraft that I am
building that there is a possibility that he may not allow me to use an
alternative engine. Granted that weight and balance, as well as power
requirements must reasonably lie within allowable ranges, what is the roll
of the kit or plans manufacturer in the final homebuilt aircraft? Will the
FAA award him the power to veto my airworthiness certificate?



--
Posted via a free Usenet account from http://www.teranews.com

"Juan Jimenez" wrote in
:

All the designer can do is send you certified mail, and all its good
for is covering his six if you buy the farm in the airplane you built
in deviation from his plans, etc. There's nothing he can do to stop
you from flying it.

Or, in your case, not flying it.



ALC