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Gear Door Fairing Recommendation


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Just flew down and back from Marion County to Florida Exec and on post flight notice right gear fairing frayed and a small section missing. Soooo, question - probably can get mech to do some fiberglass molding work? Or new/pulled fairing or just file down and tape off? Just wondering what folks have done in the past and cost. Picture attachedIMG_0001.jpg

 

 

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Be sure that the doors overlap..The flat outer door over the inner door----.if they don't it could jam the gear up.13)      With the gear in the up position, place the new gear door so that it is overlapped by the outer door and is square with respect to the direction of flight. On some installations it may be necessary to trim the edge of the door adjacent to the brake caliper and tire.

Paul

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simple repair.  Be sure to use real aircraft fiberglass, such as 7781 and real structural aircraft epoxy, such as MGS or Aeropoxy.  Looks like the outer gear door was too tight and it cracked or chafed the top part of that inner gear door off.

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On 4/6/2019 at 8:09 PM, jetdriven said:

simple repair.  Be sure to use real aircraft fiberglass, such as 7781 and real structural aircraft epoxy, such as MGS or Aeropoxy.  Looks like the outer gear door was too tight and it cracked or chafed the top part of that inner gear door off.

I keep hearing references to something like "real aircraft fiberglass" but haven't been able to determine what that means.   E-glass (like 7781) is used for things like radomes because it doesn't conduct electricity well, and S-glass (like 4533) is often recommended for "structural" aircraft applications because it has more tensile strength and some other properties that may make it preferable to E-glass where more strength is needed and conductivity doesn't matter.  There are other types in-between and lots of different flavors.   None are specific to aircraft or aviation as far as I can tell.

AC43.13 and other ACs that I've been able to find regarding composite construction and repairs seem to provide little to no guidance on the matter.   Material selection seems to be up to the user.

I've heard "authoritative" advice in many contradictory directions, but nothing substantiated.  

The same sort of questions apply to the matrix or epoxies.  There's not a lot of definitive guidance out there that I can find.

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@anthonydesmet Hi Anthony - pull the old (both) fairings off for now. 2-3 MPH speed penalty 

I’m making new sets for folks under owner produced parts rules. 

I have a couple of people still in line ahead but can make you a set at a very reasonable cost.  I have plenty of material left over.  Let me know if your interested and I’ll forward you the rules for owner produced / supervised parts. 

Brad 

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1 hour ago, EricJ said:

I keep hearing references to something like "real aircraft fiberglass" but haven't been able to determine what that means.   E-glass (like 7781) is used for things like radomes because it doesn't conduct electricity well, and S-glass (like 4533) is often recommended for "structural" aircraft applications because it has more tensile strength and some other properties that may make it preferable to E-glass where more strength is needed and conductivity doesn't matter.  There are other types in-between and lots of different flavors.   None are specific to aircraft or aviation as far as I can tell.

AC43.13 and other ACs that I've been able to find regarding composite construction and repairs seem to provide little to no guidance on the matter.   Material selection seems to be up to the user.

I've heard "authoritative" advice in many contradictory directions, but nothing substantiated.  

The same sort of questions apply to the matrix or epoxies.  There's not a lot of definitive guidance out there that I can find.

E glass or S glass is OK,  Bondo brand autozone parts store fiberglass cloth in no way compares to aircraft stuff.  Same with epoxy. Bondo polyester resin or hardware store epoxy doesnt approach the stiffness and strength of aircraft structural epoxy.

Put it this way, clamp the gear door to the table with part hanging over the side. . If you cant stand on the gear door, its not stiff enough.

Edited by jetdriven
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1 hour ago, jetdriven said:

E glass or S glass is OK,  Bondo brand autozone parts store fiberglass cloth in no way compares to aircraft stuff.  Same with epoxy. Bondo polyester resin or hardware store epoxy doesnt approach the stiffness and strength of aircraft structural epoxy.

Put it this way, clamp the gear door to the table with part hanging over the side. . If you cant stand on the gear door, its not stiff enough.

This is what some people say, but I've never seen any references or data to back it up.   There's nothing in AC43.13 or any ACs that I can find.   "Manufacturer's recommendations" seems to be the rule, referring to the manufacturer of the matrix/epoxy or glass.

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Thanks Don - these are 5 layers of carbon, one of fiberglass and vacuum formed. Yours are hand layup - looked great but definitely thicker.  The vacuum process does a lot to limit how much epoxy is in the structure.  Less is more in terms of strength.

Here are some other pics of the parts in process

F73C8D35-BC66-4BC7-8A1B-C38C01506514.jpeg

E0112352-2775-429C-BB16-1DA246759DB3.jpeg

1D7E2916-090D-47D4-8DC7-AFC9F61B2D66.jpeg

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Some things to be familiar with...

1) The glass is the strength of the part...

2) The resin, or matrix, or epoxy is the glue that holds the fibers together... and provides a nice smooth moisture resistant finish...

3) The direction the fibers are laid, usually has to do with the strength desired... thin woven mats oriented in different directions spreads the strength out uniformly in all directions...

4) Vacuum bagging is a great technique to provide a smooth finish and minimize the amount of extra resin while eliminating bubbles that want to mess up the polymer matrix adhesion... extra resin, as we know, doesn’t add strength, but sure does add weight... eliminating air, that keeps the most strength.

5) making good strong parts, is one part good materials, and one part good process...

6) a good glass has a rough surface that really takes a good hold of the polymer... this bond is critical to the part’s strength... expensive glass will be interesting to see at the microscopic level... and it’s data will look like a very strong stress/strain graph... lots of stress, no strain, and a big number for ultimate strength when it fails....

+1 for user supplied parts...

 

Great pics, Brad!

PP thoughts only, with a hint of a polymer guy mixed in....

 

Best regards,

-a-

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18 hours ago, EricJ said:

This is what some people say, but I've never seen any references or data to back it up.   There's nothing in AC43.13 or any ACs that I can find.   "Manufacturer's recommendations" seems to be the rule, referring to the manufacturer of the matrix/epoxy or glass.

I think the SRM for the J model Cowling calls  for 781, the old number for 7781. That’s what I used to rebuild mine. And I do mean rebuilt like the exhaust is rebuilt, cut half away. Rebuild that part. Then cut the other half away and rebuild it. 

Edited by jetdriven
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1 hour ago, jetdriven said:

I think the SRM for the J model Cowling calls  for 781, the old number for 7781. That’s what I used to rebuild mine. And I do mean rebuilt like the exhaust is rebuilt, cut half away. Rebuild that part. Then cut the other half away and rebuild it. 

The SM says 181 actually, which has similar specs to 7781.   The listed epoxy resin systems seem to mostly not exist any more, either.

 

 

 

 

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I have a thread out there now about pretty much the same thing, but both of my inner doors have been chewed up and damaged. As a result I had them removed during the annual last month and a lot of responses that I I got here on the subject was to keep them off.

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