Decalage

[DRETW]

Ask First?
I've about finished my micro SE-5 and I'm ready to attach the wings.The stab is fixed(glued) so I'm giving my measurments all relative to it (the stab) at 0 degrees.
Because of its size, weight, power I don't imagine this plane to ever excede 100 or 125 MPH. Probably more like 5 to 10MPH. As an indoor micro it will fly at just above stall speed most all the time.
I'm guessing the decalage to be about 2 1/2 degrees for the bottom and 5 degrees for the top.
I would really appreciate any imput I can get.
Some specs;

Wingspan 15 3/4 inches
AUW 45-50 grams
Wing Area 85-90 inches sq.
Motor N-20 geared, 30? grams thrust,
2 1/2 degrees down, adjustable
Dihedral about 7 degrees, 3 degrees washout
Controls Rud, Ele, Thr

The wings are just set in place for now. I posted this question in the micro forem but I didn't get any responces, I'd like to be sure before I glue them permantly. I'll take anyones 2 cents.
Ted

[Sparky Paul]

I'd put both wings the same... maybe 2 degrees.

[DRETW]

I thought the front (top in this case) wing should have a bit more pos AOA than the bottom so it would stall first and make for a gentler break? Or is this why my guillows Neiuport 11 seems so tail heavy?

[DRETW]

Thank you for your imput Sparky!

[Sparky Paul]

I feel that decelage as applied to full-scales is somewhat out of place in models, since there's no occupant to be concerned about the severity of a stall.
According to Wylam drawings of the full-scale SE-5A for instance, the upper wing is rigged at +5, the lower wing at +6.
Various versions of the Albatross used the same rigging, upper and lower.
Nieuports ARE tail heavy! :)
That very short nose and very long tail assure that.

[BMatthews]

I'm with Sparky on this one. 2 or maybe 3 degrees tops. From there you can trim the elevator to go along with the final CG location. If you're using those little coil doohickys I assume that there's still a way to alter the center position?

[DRETW]

I'm with Sparky on this one. 2 or maybe 3 degrees tops. From there you can trim the elevator to go along with the final CG location. If you're using those little coil doohickys I assume that there's still a way to alter the center position?

Thats sorta the problem, it does use those lil' doohickys (the proper aeronautical term is thingamajig [ its French ]) and because of this the trim must be reset every time its powered up. You can't see in the photos but the elevator is counter-balanced with the addition of a couple of #8 shotgun pellets hammered flat and glued to the foward part of the ele. I suppose I could add or subtract a little to fine tune its flight but I wanted to get as close as possible to start. Yeah, if ya'll haven't tried using actuators I tell ya their light, simple, and they can make a grown man cry!

[BMatthews]

Nice job! But those wing struts are a bit of overkill ain't they? :D

What about cutting away the stab from just behind the leading edge so that you can wegde the stab and elevator to add any additional decalage that is required. I hate to say it but the final amount will be based on the CG location and how much pitch stability you want it to fly with. There's no easy way to figure that out other than fly and adjust.

[DRETW]

You wouldn't say that if you saw me (try to) fly!!

[Nigelp]

Same subject - different plane !

I just built my first foam profile flattie see "Zactly 3D" in the Foamies thread.

It flies very well, but has a tail down attitude - which doesn't seem to change much with C of G position, downthrust etc.....I finaly came to the conclusion that ALL profile flatties MUST fly tail down.

At 0 deg AOA (horizontal stab & wings) the flat wings have ZERO lift ! The only way a profile flattie can provide lift is if the tailplane is set with a slight negative angle to the wings or the wings set at a slight positive angle to the tailplane....If the whole thing is built flat, it HAS to fly tail down in order to provide a slight positive AOA to the wings in order for them to create lift !!!!

Makes perfect sense to me, but then i'm not an engineer !? Can anyone confirm my theory ?

Nigel

[alexcmag]

Same subject - different plane !

I just built my first foam profile flattie see "Zactly 3D" in the Foamies thread.

It flies very well, but has a tail down attitude - which doesn't seem to change much with C of G position, downthrust etc.....I finaly came to the conclusion that ALL profile flatties MUST fly tail down.

At 0 deg AOA (horizontal stab & wings) the flat wings have ZERO lift ! The only way a profile flattie can provide lift is if the tailplane is set with a slight negative angle to the wings or the wings set at a slight positive angle to the tailplane....If the whole thing is built flat, it HAS to fly tail down in order to provide a slight positive AOA to the wings in order for them to create lift !!!!

Makes perfect sense to me, but then i'm not an engineer !? Can anyone confirm my theory ?

Nigel


Nigel,

You're right. Any flat or symetrical airfoil need some incidence to provide lift. If wing incidence is zero, whole airplane will fly nose up.

If you it fly faster, will need less incidence for the same lift, reducing the "nose up" attitude. That's why this is not usually noted on GWS Formosa, in example.

[Nigelp]

Alexmag,

Thanks for your confirmation - I appreciate it !

Take care,

Nigel

[Murocflyer]

You wouldn't say that if you saw me (try to) fly!!

I'm curious to know, how did it fly?

Frank

[DRETW]

I'm curious to know, how did it fly?

Frank

Actually, it still hasn't yet. I took a break and tried to build a LRF. I don't build very fast and it seems my mind is constantly wandering off somewhere else. ( took me 21 years to finish a guillows Neiuport II, and honestly, I'm still working on it). I don't plan on taking quite so long on the SE in fact I was messin around with it today.
Soon as I try it I'll let ya'll know.
Ted

[Murocflyer]

Wow, great looking planes! I have yet to dabble into the indoor stuff. Sure looks like a blast.

Good luck on your upcoming flights.

Frank