Johnnybgoode

Has anyone ever...?

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...thought that the myriad under-wing inspection panels and their corresponding transitions add drag as the air flows under the wing? I just bought some 4" wide 3M471 tape and will smooth those transitions, first on the forward inspection panels, and see if there is a noticable difference in feel or smoothness of the airframe throughout the flight regime. I know that my C has 16-20 of those single-thickness panels - except at the wing root where there is one with a doubler that has much less indentation/drag. That one is put on with panhead screws though...

Curious if

1) there are as many on the newer models and

2) if they are single thickness or double, so as to minimize the transition.

Chime in if this is a silly project from a scientific perspective. I am not an aerodynamics-trained guy.

Patrick

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Please post your results.  

My gut tells me that if there was room for improvement for the old models, then Roy LoPresti would have addressed it in 1977 when he cleaned up the F to make the M20J 201.

But you never know- and that's why I'm really curious.

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The top side gets much attention because the drag there messes with the lift in a more significant way...

If you can prove a measurable difference.... a dollar sign can be associated with the cost of the drag... and how much people would pay to eliminate it...

The ability to manufacture or machine stepped parts that fit perfectly is pretty much here today....

sounds pretty interesting...

Best regards,

-a-

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Glider pilots tape over edges.  Also look for Piper Cherokee Smooth Wing by Laminar Flow Systems.

Clarence

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Yes, Clarence. Dave Anders, in his beautiful and FAST RV-4 has been the impetus for my buying stock in 3M. My -4 has a couple of seams that are bare and my Mooney is beginning to look that way too. I'll tape and fly today and see if there are any noticable differences.

I didn't know of the Piper mods. I am curious to know from a theoretical standpoint if the under surface is as important flow-wise as the upper wing surface.

Patrick

Edited by Johnnybgoode

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Patrick, if you want to reduce drag in your C model, put all emphasis on the cowl. You’ll find more knots in there than modding the rest of the plane combined. The amount of work taping all those inspection panels and your ASI won’t be sensitive enough to register a difference!

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I’m curious to hear about the outcome - even subjective data - of your experiment. #TheScientificMethodRules

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Glider pilot here...  I doubt you will see much difference.  That being said, you will need more than tape to do what you want to do properly.  You should also be very very careful /thoughtful where you put the tape... There have been gliders that have lost control with tape coming off the wing.  Saying " glider people tape their wings" is understating what is done by a lot.  For every day tape, we are only taping joints between flying surfaces.  The wing root for instance, we seal that gap with one type of tape.  For the long term tape, there are several materials that go into this.  We use a 2 sided transfer tape which goes on the wing skin, then a curved Mylar and finally a "safety tape" which is designed to prevent the Mylar from peeling up because it IS A SAFETY ISSUE.    The materials to gap seal my entire wing run about 200 dollars for a 15m wing.

All of this meticulous work adds very very little performance in the area of L:D ... the problem is as you go faster than best L:D speed, that performance gain is more and more muted.  So why bother?  For contest flying (racing) , a 1% difference could mean a win.

 

Edited by Austintatious
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4 hours ago, Johnnybgoode said:

Yes, Clarence. Dave Anders, in his beautiful and FAST RV-4 has been the impetus for my buying stock in 3M. My -4 has a couple of seams that are bare and my Mooney is beginning to look that way too. I'll tape and fly today and see if there are any noticable differences.

I didn't know of the Piper mods. I am curious to know from a theoretical standpoint if the under surface is as important flow-wise as the upper wing surface.

Patrick

I had always thought that the underside was very important.  Higher pressure(more dense) air below and more drag, but I have no way to prove it.

Clarence

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From what I understand, the whole smooth wing business is more to do with maintaining laminar flow and the way it affects lift than about reduction of forward facing parasitic drag. That's why most Mooney wings don't have dometop rivets on top for the front third. But behind that point, the airflow is already turbulent so the gains would be negligible. Keeping the leading edge clean of bugs and waxed probably goes a longer way than micromanaging the inspection plates that are further back and underneath.

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Someone made a comment about the "antenna farms" near the tail not affecting performance as much as things further forward.  I imagine this is something along the same lines.

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3 hours ago, 201er said:

From what I understand, the whole smooth wing business is more to do with maintaining laminar flow and the way it affects lift than about reduction of forward facing parasitic drag. That's why most Mooney wings don't have dometop rivets on top for the front third. But behind that point, the airflow is already turbulent so the gains would be negligible. Keeping the leading edge clean of bugs and waxed probably goes a longer way than micromanaging the inspection plates that are further back and underneath.

My understanding is that it's not so much that the air gets turbulent as it is that the "attached layer" slows down from the contact friction so the affect on drag is less.   Airliners are made this way as well, with lots of flush rivets near the front and hardly any near the tail.

 

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This is the discussion I hoped to learn from. I've "heard " lots of things over my 22 years of flying, but I've "heard" many things from politicians too.

I was hoping to hear some science and we may be on the verge of it. That said, I taped, carefully, but didn't get to fly. Tomorrow...

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44 minutes ago, Johnnybgoode said:

This is the discussion I hoped to learn from. I've "heard " lots of things over my 22 years of flying, but I've "heard" many things from politicians too.

I was hoping to hear some science and we may be on the verge of it. That said, I taped, carefully, but didn't get to fly. Tomorrow...

Haven’t you heard, never trust anyone who’s profession begins with a P 

I’m waiting for the results

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11 minutes ago, Shiny moose said:

Haven’t you heard, never trust anyone who’s profession begins with a P 

You mean like Pharmacists and Physicians? ;)

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15 minutes ago, skydvrboy said:

You mean like Pharmacists and Physicians? ;)

Professors, Prostitutes, and Pissants?

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6 hours ago, Andy95W said:

Pirate? Proctologist?

(scary thought- a Pirate Proctologist with a hook for a hand)

Haha if yours is using the whole hand, find another one!! 

Sorry

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On 4/15/2019 at 11:10 PM, KLRDMD said:

Periodontists, pediatricians & pathologists ?

Especially periodontists. That's a ragtag bunch. :lol:

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On 4/15/2019 at 8:53 PM, Shiny moose said:

Haven’t you heard, never trust anyone who’s profession begins with a P 

Sure makes me glad I'm just a lowly Plastics Engineer . . . .

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Making the belly  smoother with tape might have an effect.  Note LASAR claims a 6kt speed gain with their 1 piece belly mod, far greater than the claimed 3kt with the 201 windshield. It almost makes me want to pay an arm and a leg for a one piece belly.  Of course they claim 5mph for the cowl closure, which I'm pretty sure does nothing for speed.  

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55 minutes ago, Hank said:

Sure makes me glad I'm just a lowly Plastics Engineer . . . .

We wont include that one, My wife also has a bachelors in plastics engineering then many more degrees and is a university Professor. So exclude professor also. 

Maybe its a different letter I was thinking about !!!

Edited by Shiny moose

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