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  #1  
Old 09-06-2018, 12:36 PM
az_gila's Avatar
az_gila az_gila is offline
 
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Location: 57AZ - NW Tucson area
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Question Door bonding error fixes

How should I fix an error?

Apparently during the bonding of my first door some of the cabosil goop was probably smeared off the area shown in the sketch -



The missing bonding showed up when I attached the door hinges and can be verified with a bright light shining through the door skins - I have the early green glass parts. The periphery of the door is good and the unbonded area is only on one location. It is probably has less than a 1/32 gap but it does show up when the hinge attach screws are tightened.

I can think of two options but I'm sure there are more.

1. Drill a hole (#30?) in one side in the center of the 4 screw holes and inject a medium mix of flox forcing it to go out in all directions. Use nylon screws on the existing holes to prevent leakage.

2. Cut out on one door skin (the outer?) in the shape of the the square shown in the pic above with 45 degree edges. Fill with cabosil and/or flox and re-attach. Use nylon screws to ensure alignment and tighten them down to ensure 'squish'.


Possible problems I can see -

1. Getting the right consistency and being able to force the epoxy mixture into the gap.

2. Getting the cut-out piece back into alignment, but this may be solved with a custom shim. It looks like my door assembly needs a .025 or .032 shim under the outer door hing anyway.

Any other options? It's only fiberglass so it can be fixed.

It is getting that good gull-wing look though -

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Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ

Last edited by az_gila : 09-06-2018 at 12:40 PM.
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  #2  
Old 09-06-2018, 12:58 PM
Kyle Boatright Kyle Boatright is offline
 
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I would go with the epoxy injection. There is no way I would cut a chunk out of the door.
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  #3  
Old 09-06-2018, 01:18 PM
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Quote:
Originally Posted by Kyle Boatright View Post
I would go with the epoxy injection. There is no way I would cut a chunk out of the door.
Ditto-----your option #1 listed above.
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VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

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Old 09-06-2018, 02:00 PM
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Quote:
Originally Posted by Mike S View Post
Ditto-----your option #1 listed above.
OK...

Any suggestions on how big a hole to make for the hypodermic and how goopy to mix up the flox?

It's been mentioned before, but has anyone actually done it on a -10 door?

I think with a bright light I will be able to see how far it spreads internally.

One trouble is that if #1 doesn't work out well, then #2 becomes very difficult.
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Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ

Last edited by az_gila : 09-06-2018 at 02:02 PM.
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  #5  
Old 09-06-2018, 02:08 PM
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Mike S Mike S is offline
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Originally Posted by az_gila View Post
OK...

Any suggestions on how big a hole to make for the hypodermic and how goopy to mix up the flox?

I think with a bright light I will be able to see how far it spreads internally.
Hole big enough to fit the tip of the syringe-----shave the tip down with a razor blade.

Thick as you can get away with and still get it to come out of the syringe.

Drill a few extra holes if needed-----the flox will fill them up.
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Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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  #6  
Old 09-06-2018, 02:09 PM
rocketman1988 rocketman1988 is offline
 
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Default Syringe

Rural king, tractor supply, farm and fleet , and other farm stores carry nice syringes for the job. I did not even need a metal needle. I drilled #30 holes and shot the flox right in...
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RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
Doors - Done
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Wiring...

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  #7  
Old 09-06-2018, 02:14 PM
lr172 lr172 is offline
 
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THe problem with injection, is it assumes the cavity/void is large and consistent. It could be a bunch of small voids. Assuming you put epoxy on that area before bonding, it would seem unlikely to be one large void. The other problem with injection is air pressure. Without a vent in the cavity, it is VERY difficult to get the epoxy into anything but a small void, even with pressure from the injector.

While it is more difficult, I would opt for the second option.

Another alternative Would be to drill out the hole to maybe 5/16 then work epoxy into any voids visible and install bushings (3/16 ID) made from tube, similar to what is done in the cabin top for the front support bar. You then shape the bushing to be flush with both surfaces and then countersink. Given the thinness of the door, I would epoxy the bushing in.

You definitely don't wan't to apply screw pressure until you are sure that you have at least 1/4" of solid material around the screw and I would be concerned that you could get to this point with injection; You simply don't know what it looks like under there. The third option puts the screw tension on the bushings and eliminates the concern with voids.

I feel for you. I am at the very last stage of door work (working flanges of the top for mcmaster seals) and VERY happy to be almost past it - should finish tomorrow.

Larry
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Last edited by lr172 : 09-06-2018 at 02:28 PM.
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  #8  
Old 09-06-2018, 02:14 PM
Kyle Boatright Kyle Boatright is offline
 
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Quote:
Originally Posted by rocketman1988 View Post
Rural king, tractor supply, farm and fleet , and other farm stores carry nice syringes for the job. I did not even need a metal needle. I drilled #30 holes and shot the flox right in...

Yep. I've used a #30 and a #19 drill for the holes for this type of thing.

Hint: The local pharmacy will give you a free syringe for administering children's liquid (oral) vitamins and the like.
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  #9  
Old 09-06-2018, 02:47 PM
rocketman1988 rocketman1988 is offline
 
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Default But

But the rural king et al syringes are made for animals and they hold 35, 50, or 100 ccs.

As far as air pressure concerns, drill two holes, one to inject in, the other vents the air.

From an engineering standpoint, cutting the door open would be my last choice.

As far as getting enough flox in the void, I had no issues. Using a bushing concentrates the loads on a much smaller area than filling the entire void with flox...
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Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
Doors - Done
On Gear
290 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...

Dues Paid 2018,...Thanks DR+

Last edited by rocketman1988 : 09-06-2018 at 02:50 PM. Reason: Add
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  #10  
Old 09-06-2018, 07:17 PM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by lr172 View Post
THe problem with injection, is it assumes the cavity/void is large and consistent. It could be a bunch of small voids. Assuming you put epoxy on that area before bonding, it would seem unlikely to be one large void. The other problem with injection is air pressure. Without a vent in the cavity, it is VERY difficult to get the epoxy into anything but a small void, even with pressure from the injector.

While it is more difficult, I would opt for the second option.

.........................
In my case the missing epoxy is pretty much over the entire area marked. You can see the bonded edges with the bright light shining through method.

The edges are open so there is an air relief passage and flow path for excess epoxy. I'm just not sure how thick to make the flox.

I either missed it during door assembly - it was hot and I was trying to move fast, or it was smeared off when we placed the two floppy door skins together. On the second door we were more careful and held the second door skin by the top and bottom edges and lined up the middle clecoes first.


PS - Is the light shining through method an advantage for the old green epoxy parts over the later pink and grey gel-coated parts?
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ

Last edited by az_gila : 09-06-2018 at 07:19 PM.
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