There has been a lot of talk on construction threads of other sites questioning the size of the flaps on the Vaillencourt hurricane. The plans show a chord of 4 inches, and that's a lot of flap.   Guys are complaining that the flaps seem to blank out the elevator on landing..the plane stops flairing.

I sent an email to the Ottawa Air Museum, and a kind gentleman went out, climbed under the Hurri they have on display, and measured the chord of the flap - He measured 16 inches..

At Vaillencourt's scale that works out to a 3 inch flap. Roy said he got HIS dimensions from another set of model plans, so the size could well be off..

Question - how would the 25% smaller flap affect the landings? Will it reduce blanking? Will I still get more lift? What!!!!

Sandy, it will only make more of a difference if you're putting the flaps down a lot. Take the 3" flaps and draw an imaginary line from the center of the leading edge to the bottom of the deployed flap at max. Now if you have the 4" flap and only deploy it to the same amount down you will have the same amount of lift/drag, although the flap will be at a slightly lesser down angle.
If you deploy the 4" flap down more you will get more drag, less lift, as you will with any flap.
How's that ?

Oh, and you know blanking is a characteristic of angle of attack, when you're talking about about flaps blanking an elevator that's set above it. The turbulent air could hit the elevator if you flare a lot, but you know you land a hurricane on its mains, so it shouldn't be a problem.

so i should be able to go with the scale flap and have no problem.. :-?

increasing flap chord increases the camber and the pitching moment.  You have flown and I have flown tail draggers
nothing i flew had drag flap.  70 deg. of flap was drag flap back then.  You came in with a lot of power on and landed in a short distance.

the 3 inch chord flap at say 30 degrees will give you a nose down pitching moment. which increases forward visibility.

i think that the blanking idea comes from the way the model handles when a lot of flap is applied.


since these aircraft did three pointers all the time, then i think that the use of max flap should NOT be a problem, unless based on reynolds number the scale size and area of the horizontal tail are smaller than they should be.

i am trying to visualize an approach in say a chipmunk with max flap.  all i can remember is the thing being tossed around by turbulence over trees and such, dropping a wing and picking up with rudder.  can't speak for the Harvard, haven't flown one.

Full scale hurricane had 1 flap position - full. Gave 80 deg deflection, and dumped the nose. Pilot had the stick back in his gut right to the ground...

We don't have the advantage of steel gear mounted to steel rails and titanium stuff and maxi absorbing gear struts... our gear is mounted to wood, glued to wood, braced with wood.... >:(

Guess I'll go with the scale 3 inch flap chord and hope that minimizes the troubles other flier have had - we all know i have tremendous landing skills..... which will be exacerbated by a 25 - 30 pound plane.... ;D

http://www.vaillyaviation.com/images/Hurricane%20landing%20technique.pdf

Thanks for that link Brian but I have already copied it about 4 times (we all are aware of my stellar landing performance!!)...... my real concern is will the be a difference in landing with the smaller flap.

As an aside, i got a reply from Airframes Assembly in the Uk. (Sorry my k won't capitalize!) He confirmed the 16" measurement, and even sent a photo of the tape on the flap... 14.5" from center of torque tube to end of flap, and the tube is 3"

So, I'm going to change Roy's plans a bit and go with 3" flaps.

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tail setting angle?
take a look at the mk1 hurricane picture http://en.wikipedia.org/wiki/Hawker_Hurricane
the tails getting angle is decided, in part, by the downwash on the tail.  in the picture (which is hi rez) it appears to be quite significant i.e. quite a lot of degrees.  also the elevator angle on approach/flypast, which this aircraft is, is not that excessive, hence the advice to keep the speed up on landing.


i thought these (full size) things landed at 80 mph?  must be dreaming.

nope, landed at 80. I've seen cockpit videos of them, dump the flaps and pull the stick back....

Fussing over details  :)  Good stuff Sandy.  Looking forward to reading more as your build progresses.



Don't want to hijack your thread, but since the topic is flaps:  today I learned that the Bf 109 (Me 109) drooped its ailerons by about 11 degrees when the flaps were deployed.  And, it compensated by increasing the angle of incidence of the horizontal stab.  That's pretty cool for a design that first flew in 1935.  Unfortunately, the book I am reading didn't give me a reference source to confirm this feature.  I'm gonna dig for that one.

i think you should treat yourself, Sandy
http://www.haynes.co.uk/webapp/wcs/stores/servlet/BookFeature_HurricaneManualView?storeId=10001&catalogId=10001
mind you you might have to work on the model in a car garage.

I agree.  The Haynes books are great.

I have the one for the Spitfire; thoroughly enjoy it.

I have the Haynes book for the Hurricane. there is a ton of information in it, EXCEPT for the chord of the flaps  :-? It did, however, have some references in the back; that's where I got addresses to send my flap question to (only the nice guys at Airframe Assemblies replied  [smiley=tekst-toppie.gif]).

Another thing not mention by Haynes, but I found in a copy of the Pilots Manual, is that, unlike what a lot of us thought, the Hurricane did have provision for partial flap deployment.

"At 1000 feet on the down wind leg, ASI 120, RPM 2400, flaps at 30 deg. Over OMB, 600 feet, gear down, ASI 95, RPM 3000, flaps at 60 deg. IMB, ASI 90, RPM 3000, flaps at full 80 deg."

Not exact quote but taken from the manual.. page 32.