Isn't There A Name For This?

[Murocflyer]

Once again I find myself coming to this forum for advice. I come by every now and then for those difficult questions that only the experts that lurk here will have the answers to.

What is the angle of the horizontal called compared to the waterline of an aiplane? Lets say the horizontal has a positive angle such as in the picture below. What's that called? Is that angle bad? What can I do in flight to compensate for it if it is bad? It's too late to change it now and I didn;t think about the angle until just yesterday after I dripped the last drop of CA and sanded my last area.

Thanks for the help,

Frank


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[HELModels]

It is probably arbitrary. The dangle angle that matters is the incidence angle of the wing and the corresponding stab angle needed for the chosen Cl. Typically, and some argue that this is incorrect, this is called decalage when it is the relative angle between wing and stab. I argue that decalage is the correct term as persistent use in the literature suggests that it is now acceptable. As for fuselage alignment, I once knew an aeronautical engineer who claimed that the full scale requirement to see the runway on approach is what determines the alignment of the fuselage. With a model, there aint no souls on board. Lower drag fuselage alignments are possible with models that might not work in full scale for the reason already stated - you gots to see on final.

Oh, almost forgot, if you need positive decalage, then flip the whole shibang over and mount the rudder on the other side, since it looks like a symmetrical foil for the main.

[JetPlaneFlyer]

As ElectroStorch says... fuselage angle is pretty much irrelevant... However what is critically important is the angle of the tailplane (horizontal stabiliser) in relation to the wing. Your tailplane looks like it has a more positive angle of incidence than the wing... this is VERY bad (it could however just be an optical illusion)
For stable flight the tailplane incidence should be a little less than the wing, giving a positive 'decalage' as noted in the previous post.

[Murocflyer]

As ElectroStorch says... fuselage angle is pretty much irrelevant... However what is critically important is the angle of the tailplane (horizontal stabiliser) in relation to the wing. Your tailplane looks like it has a more positive angle of incidence than the wing... this is VERY bad (it could however just be an optical illusion)
For stable flight the tailplane incidence should be a little less than the wing, giving a positive 'decalage' as noted in the previous post.

Uh oh, this ain't good. So it's either chnage it or have a static display piece on my coffee table?

Frank

[vintage1]

Uh oh, this ain't good. So it's either chnage it or have a static display piece on my coffee table?

Frank

Or run it with massive up trim on the elevator ;)


The wing needs to be a little more positive than the tail in most designs..and yours is no exception

How they both sit with respect to the fuselage is not that critical.

However, if the model flies with the tail very high, or low, it increases drag. and as others have pointed out, a model that comes in with its nose down for a belly landing, is going to lawn dart instantly.

Just cut the stab out, and make a platform so its the same angle as the wing. Its balsa. It cuts and glues and sands.

The machine won't win any beauty prizes anyway, but at least it will fly.

[Sparky Paul]

As Vint says.."Just cut the stab out, and make a platform so its the same angle as the wing. Its balsa. It cuts and glues and sands.

The machine won't win any beauty prizes anyway, but at least it will fly."
...
And if the c.g. is anywhere's close to where it should be.

[gwinhh]

The base line for measuring these angles is the center line of the fuselage, which may or may not be the thrust line. Technically, I think decalage is the difference between angles of attack of the two wings of a biplane, though almost no one except old fellows use it that way.....

howell

[Ollie]

I use the term "decalage" too. The same meaning is "longitudinal dihedral."
See:
http://www.auf.asn.au/groundschool/umodule7.html#longitudinal

[Murocflyer]

Thanks for the replies and link fellas. I'm cutting away...

[Murocflyer]

Rework accomplished although unfortunately I had to lose the pull-pull system and went to a pushrod. As advised earlier, the pull is up elevator.

Here's the photos of the rework.

Frank


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[Murocflyer]

Maiden flight went excellent. Thanks for the help fellas!

Frank