Craig,

Interesting.......  Note that the flaps will actually fly higher than their ground rigging position because of linkage slop and in flight air flow.

Of course, every 300 series aircraft is different.  Let's assume we are talking about a slow built (fast builds are slightly different), Short engine mount, small tail, pre-preg glass, standard wheels, and built according to plans.  That means, by design, the flaps are in -7 degrees reflex when faired into the fillet - that is if the fillets were laterally located to the same position relative to the longeron.  Also, remember that the horizontal stabilizer is to be mounted between -.5 to -1 degree incidence (relative to the longeron) - another variable.

Note that increasing the reflex results in wing forces that want to further lift the nose.  If the horizontal stabilizer is not at the correct AOI, the elevator may be necessarily positioned for more nose down force that may increase drag.  It is not possible to know if your rigging is "sweet" for everyone else unless all the conditions match.  Indeed, your reflex position may overcome a condition in your tail.

If you wish to attain greater speeds, consider also using gap seals on the rudder and elevator.  BTW, where is your rudder positioned at 215 Knots (true or indicated?).

I do have a problem with your sea level speeds as the aircraft would have increased drag from the sea water.

Grayhawk

 

Hi Bill,

 

I know a lot of others are claiming that reflex is at the faired in position.  That may not be the best position.  My little 320 does 215 kts at sea level.  210 is about the average cruise at 7500.  I am dialing in an extra 1/2 inch (measured at the trailing edge of the flap) of reflex.  While flying in formation I have determined that for my airplane this is the sweet spot.  Too much will slow it down and any less will too.  The difference between the faired in position and my reflex position is 7-10 kts.  I also have the gaps on the flaps taped  and gap seals on the ailerons. 

 

Craig

N73S

From: Bill Kennedy [mailto:bill_kennedy_3@hotmail.com]
Sent: Wednesday, March 24, 2010 3:27 AM
To: lml@lancaironline.net
Subject: [LML] 320 Airfoil Reflex

 

I've never been certain that my flaps up position is exactly right. I know some of you couldn't sleep if their flaps weren't in exactly the best spot. So, here's what I would like from you:

What is the exact angle between your cockpit longeron and the top inboard skin of your flap when it is fully up? I ask this question because it will be easy for me to measure and correct if necessary and it is not ambiguous. My plane is a 320.

Thanks -- Bill Kennedy

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