Wot 4 wing incidence

[Geoff S]

I'm well on with the replacement fuselage for my ARTF Wot 4 Mk2 and I've taken the opportunity to check the alignment and fitting of the wing and tail plane.  I thought I'd measured for the tailplane slot in the side piece very carefully, but, it appears, not carefully enough.  The wing is 2deg negative relative to the tailplane. I was aiming for 1 to 2 deg positive, so it's a fair way out.  On the positive side, the wing fits well, is square, and is parallel to the tailplane in the precut slots. The wing seat need a little fettling, but nothing serious. At least the tail isn't glued so I can modify the slot by cutting and filling to get it to the angle I think is appropriate.

 

Is my feeling that 1 or 2 deg positive reasonable?  What would be the effect of flying with 2 deg negative incidence?  Does anyone know the actual wing incidence of a kit built or ARTF Wot 4?   I only need to lower the front of the tailplane by about 3mm to achieve a 1 deg positive incidence, so it's not an impossible mod and won't mess up the work I've already done to repair the model successfully, too much.

[PatMc]

IMO the wing incidence WRT the thrust line is more important. The elevator can be used to effectively sort out the tailplane/wing incidence but fettling it before you glue the tailplane in place would be better. Never had a Wot 4 but with a sports aerobatic model my own choice would be 0-0 wing/tail incidence.

[SIMON CRAGG]

Oddly enough I have just fitted an old skool Wot 4 wing to my Thunderbob model, which flew like a brick with the foamboard wing.

 

After a bit of carving out, set it at 0/0.

[Geoff S]

Thanks.  After a minor adjustment to the tailplane slot (3mm down at the front), the decalage (a more correct term, as it refers to the angle between the wing and tailplane) is now slightly over 0 deg (about 0.5 degrees).  I'm thinking of increasing it a bit more while I can as it'll be much more difficult once everything is glued and covered.

 

Simon, how well did your Thunderbob fly with the Wot  4 wing at 0 deg relative to the tail?

[SIMON CRAGG]

I'll let you know Geoff, not flown it yet due to the patch resembling a paddy field!.

[Geoff S]

34 minutes ago, SIMON CRAGG said:

I'll let you know Geoff, not flown it yet due to the patch resembling a paddy field!.

 

Time for floats? 🙂

[Philip Lewis 3]

Around 1% should be ideal, the effect of negative incidence would be significant up elevator trim to counteract it to get it to fly straight level thereby creating additional unwanted drag.

 

0 degree would be OK but again you would trim elevator up to sort it out, so if yo fly as much inverted as upright 0,0,0 can be a good set up. 

Edited March 13 by Philip Lewis 3
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[Geoff S]

Thanks, Philip.  1%, or a touch under, is what I've ended up with.  I don't make a habit of extended inverted flight 🙂

 

Using control surfaces to counteract aerodynamic peculiarities can't be ideal.  In sailing, a dinghy is set up with the centre of effort (the sails) slightly behind the centre of lateral resistance (the hull) so that when close-hauled close to the wind, the boat tries to point up and that's counteracted by a small rudder correction (weather helm), which helps the 'feel'.  Excess rudder correction slows the boat, which isn't what you need when racing, so, like flying, it's all a matter of balance.

[Philip Lewis 3]

Exactly, and a good analogy,