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  #1  
Old 11-25-2021, 04:11 PM
bernsbm bernsbm is offline
 
Join Date: Nov 2015
Location: Mequon, WI
Posts: 68
Default Plans revision related to the wing root gap seal

Anyone know why the recent changes to 38iS/U "Changes Made related to the necessary installation of wing root gap seal before flight" were made? Curious because I just had my plane painted after flying it for a year without the gap seals. Seals are now installed.

Thanks!
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  #2  
Old 12-01-2021, 07:03 PM
JwWright57 JwWright57 is offline
 
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Location: Charlotte, NC
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Iím curious also. I was going to wait (i have about 5 hours on the AC) until later but i guess now Iíll do it and replace them later when it gets painted.
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  #3  
Old 12-02-2021, 07:02 AM
bernsbm bernsbm is offline
 
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Location: Mequon, WI
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I heard back from tech support at Van's. Someone reported a change in stall speed/handling without the gap seals. Van's performed test flights and confirmed there was a difference in flight characteristics without the seal prompting the revision.

I have been flying two RV12's recently. One with the gap seal installed, the other, awaiting paint, without the gap seal. I noted the flare/stall characteristics of the plane without the seal were more abrupt. Most notably, when I expanded the wing skin fuselage gap to 3/16 inch in preparation for seal installation and paint, the flare/stall characteristics became even more abrupt. I needed to add power on virtually all landings.
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  #4  
Old 12-02-2021, 09:18 AM
AeroDog AeroDog is offline
 
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Location: New London, NC (near Charlotte), Longmont, CO
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I talked to a couple of -12 owners at Oshkosh who had used tape like the glider guys do rather than the provided seal. Any thoughts on this?

Jerre
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  #5  
Old 12-02-2021, 10:44 AM
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Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
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Quote:
Originally Posted by bernsbm View Post
I heard back from tech support at Van's. Someone reported a change in stall speed/handling without the gap seals. Van's performed test flights and confirmed there was a difference in flight characteristics without the seal prompting the revision.

I have been flying two RV12's recently. One with the gap seal installed, the other, awaiting paint, without the gap seal. I noted the flare/stall characteristics of the plane without the seal were more abrupt. Most notably, when I expanded the wing skin fuselage gap to 3/16 inch in preparation for seal installation and paint, the flare/stall characteristics became even more abrupt. I needed to add power on virtually all landings.
Wow, that's pretty wild. I have my wing roots sealed on top and around front "D" section of leading edge. I left bottom open to facilitate drainage and provide a little airflow to prevent moisture buildup. Stalls are extremely benign. No plans to changeÖ
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  #6  
Old 12-02-2021, 11:32 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by AeroDog View Post
I talked to a couple of -12 owners at Oshkosh who had used tape like the glider guys do rather than the provided seal. Any thoughts on this?

Jerre
This should provide the same result... we used the same method on the first prototype.

Keep in mind that if presenting an RV-12 for initial certification as an ELSA, technically the seals should be in place for it to be eligible for certification since the KAI specifically specifies it.
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  #7  
Old 12-02-2021, 07:11 PM
ravenstar ravenstar is offline
 
Join Date: May 2021
Location: New Hampshire
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While I don't doubt the issue in any way, I'm simply amazed that such a seemingly small change would have such a noticeable impact on the flight characteristics. I'd really like to understand what is happening aerodynamically speaking. Are there any good reading materials that might help?

I mean, if something I would casually have dismissed as cosmetic impacts stall behavior, what other significant details am I ignorant of?
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  #8  
Old 12-03-2021, 07:53 AM
bobg56 bobg56 is offline
 
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Location: Peachtree City, GA
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I flew mine for a couple of years without them, then added when doing my last C.I. I didn't experience any noticeable change in flight performance however I didn't go through the trouble of recording any numbers before and after...I did it to keep out rain water since I don't yet have a hanger.
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  #9  
Old 12-03-2021, 09:09 AM
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greghughespdx greghughespdx is offline
 
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Location: Aurora, OR
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Scott's point about ELSA certification requirements is an important one to reiterate. If the seal is not installed, technically the airplane is not completed to the plans specs.

Pilots of RV-12 aircraft with the gap seal missing have reported adverse effects, including unusual alarming noises and changes in aerodynamic behavior. The company's clear position is that they need to be installed before the first flight, and again if they are not installed the ELSA inspection should not result in a pass (EAB would obviously be a different situation). A seemingly "small" thing (the narrow gap) actually covers a substantial amount of area on an aerodynamically meaningful portion of the airframe. It doesn't take much in terms of gap size to have a potentially substantial aerodynamic effect.
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