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Jim Meade

Wing Gap Seals

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The CTSW uses mylar gap seals and various types of tape on the stabilator trim tab.

Does anyone have direct, personal, specific knowledge of the application of mylar gap seals to wing flaps or ailerons on the CTSW?  I'd like to communicate with someone with direct experience.

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I don't think the tape is mylar, it's bolus tape which is a stretchy, rubbery plastic.  Mylar doesn't really stretch.

I don't think you can tape the flaps, they are slotted type and the wing/flap gap changes as they extend/retract, which would pull, tear, and/or bunch up the tape.

In theory you could tape the ailerons, but they have very small gaps and I don't think you'd gain anything.  You'd have to tape them at max deflection to avoid the tape binding them, and then when they were not fully deflected you'd have excess tape either wedged into the gap (a potential binding problem again) or out in the air stream (creating more drag than without tape).  Seems like a maintenance headache with no benefit to me.  And the possibility of binding a control surface is hazardous.

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Andy,

Do you have direct, personal specific knowledge of gap seals on the FD CTSW or are you speculating?  Nothing you say sounds at all like my experience with gliders or with the gap seal information available at Wings and Wheels.

The tape on the underside of the FD CTSW stabilator-trim tab joint is mylar.  The tape on the top of the joint is Bowlus.  If you doubt me, ask Arian Foldan at FD USA.  Arian substantiates my reference of Wings and Wheels as the procedure used to gap seal that joint.

Again, I'm looking for direct, specific, personal knowledge of gap seals on the flaps or ailerons of the FD CTSW or FD CTLS.  So far, I haven't found anyone who has done it but I'm looking.

 

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35 minutes ago, Jim Meade said:

Andy,

Do you have direct, personal specific knowledge of gap seals on the FD CTSW or are you speculating?  Nothing you say sounds at all like my experience with gliders or with the gap seal information available at Wings and Wheels.

The tape on the underside of the FD CTSW stabilator-trim tab joint is mylar.  The tape on the top of the joint is Bowlus.  If you doubt me, ask Arian Foldan at FD USA.  Arian substantiates my reference of Wings and Wheels as the procedure used to gap seal that joint.

Again, I'm looking for direct, specific, personal knowledge of gap seals on the flaps or ailerons of the FD CTSW or FD CTLS.  So far, I haven't found anyone who has done it but I'm looking.

 

Sheesh, sorry I attempted to give some help, and that I committed the grave sin of posting an answer didn't meet your exacting standards of direct personal experience.  I doubt you'll find anybody with personal experience though, because it's frankly kind of a dumb idea. 

Could you do that to your control surfaces?  Um sure.  What would you gain?  A half knot?  BUT... the slotted flaps rely on blow-through air to generate their effects, so you are interfering with how the flaps function, and slowing or hindering that blow through air will affect stall speeds and flap effectiveness.  Though I have never stood out on the wing of a moving airplane and measured airflow to get "direct, personal knowledge" here's an excerpt from Bold Method:

By opening a slot between the wing and the flap, high pressure air from the bottom of the wing flows through the slot into the upper surface. This adds energy to the wing's boundary layer, delays airflow separation, and produces less drag. The result? Lots of additional lift, without the excessive drag.

And from the Wikipedia entry on slotted flaps:

A gap between the flap and the wing forces high pressure air from below the wing over the flap helping the airflow remain attached to the flap, increasing lift compared to a split flap.[11] Additionally, lift across the entire chord of the primary airfoil is greatly increased as the velocity of air leaving its trailing edge is raised, from the typical non-flap 80% of freestream, to that of the higher-speed, lower-pressure air flowing around the leading edge of the slotted flap.[12] Any flap that allows air to pass between the wing and the flap is considered a slotted flap. The slotted flap was a result of research at Handley-Page, a variant of the slot that dates from the 1920s, but was not widely used until much later. Some flaps use multiple slots to further boost the effect.

But maybe they don't teach that in glider school.  😎

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Looking at the wing design, how the ailerons are attached, and the design of the gap, I am of the opinion that the design is supposed to have airflow between the gap. Closing that off could lead to poor stall characteristics and poor handling. If you do choose to close the gap be very cautious when test flying the airplane.

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