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Cabin doors hinges backplates

O

oren_rokach

Well Known Member
Hi guys,
Trying to figure how to reinforce my cabin doors' hinges.
Don't like the idea of countersinking my outer shell and using AN509 nuts directly into the fiberglass.
Would prefer some king of a reinforcement bracket, so it will be aluminum/fiber/stell(hinge) sandwich.
While no problem doing that on the Cabin top, since there are pockets, the outer shell glued to the inner is so thin, that if i will add some kind of bracket it will sit on top of the door.

What are you guys doing?
is the per-plan countersinking lasts good enough? ideas?

Thanks!
Oren
 
Doors

I used SS 100 degree countersunk flush washers. Countersunk similar to the plans with the washers to spread the load...
 
Airward

I think construction is just as much an issue, when you have the doors on and off a zillion times. You want to be able to set the doors in the same alignment every time you put them on, and you are better off not fiddling around with separate nuts on the inside.

There is one after market product out there - here - but it comes at a way over the top price, and the top plates do protrude about 3mm.

You could easily make up the inside nutplates/reinforcement plates (epoxy'd in place inside the cabin top), and use temporary reinforcement (an external plate, or washers) on the outside of the door (only) during construction. Just use temporary AN3 bolts to attach/detach the doors, often just two bolts per hinge on the cabin top will do. Once you're done, choose what to do on the outside of the doors. Either follow the plans, keep your custom reinforcing plates, or countersink and use SS washers as Bob described.

A.
 
Countersinking is a very effective method of retention. Just because the flare on the screw is longer than the depth of the f/g layup doesn't mean it is not strong. I built per plans and find the hinges to be very firmly attached to the door. don't forget that you already have 1/4" steel plate acting as reinforcement for the f/g. Can't see why you need more.

We could all argue that the door skin could be thicker, but I haven't heard of anyone ripping the door off the hinges yet.

Larry
 
Last edited:
Hi Oren

Could you glass in a thin steel plate on the outside of the door without it being an obvious bulge?

Otherwise, maybe just go with the plans though i agree it ?feels? too flimsy.
 
lr172 said:
SNIP

We could all argue that the door skin could be thicker, but I haven't heard of anyone ripping the door off the hinges yet.

Larry
Click to expand...

Happened to me - when a National Guard C-130 did a full power reverse taxi on the ramp right in front of me. The pilot door departed the aircraft, snapping the hinges. I was happy the hinges themselves failed and not the screw heads pulling out of the cabin top or the door.

The cabin top and door were not damaged. Some replacement hinges and I flew the plane home.

My recommendation, for all screws in the door use #10 SS tinerman washers under the heads. Worked very well for me. Do not glass over the screw heads as then you will end up messing up your paint job if you ever needed to do associated maintenance.

Carl
 
Carl Froehlich said:
I was happy the hinges themselves failed and not the screw heads pulling out of the cabin top or the door.

Carl
Click to expand...

Well, there's your answer. Hinges failed before the standard attachment to the f/g. Seems like good evidence that there is no real need to reinforce, as it is not the weak link.

Carl, good to hear the fix was simple. Wish I had thought to use tinnermans and leave unpainted. Mine are covered with bondo only, so easy to scoop out if the need arises.
 
Has anyone else noticed the flex in the cabin top/doors around the hinges? I've taken a close look at a couple of finished airplanes as the doors open and close, and there is a fair amount of movement in the fiberglass. Over the long term, that is a concern to me...
 
Kyle Boatright said:
Has anyone else noticed the flex in the cabin top/doors around the hinges? I've taken a close look at a couple of finished airplanes as the doors open and close, and there is a fair amount of movement in the fiberglass. Over the long term, that is a concern to me...
Click to expand...

I have noticed some flex during opening/closing. Not really surprising given the size/weight of the door relative to the f/g thickness, not to mention the force of the damper on only one side. I am not overly concerned, as the f/g is not likely to deform while in the closed position, where it spends 99.9% of it's time. structure seems pretty rigid/stable in the closed position. I just can't see how a few hours of jostling over it's life can create real issues.

Just one man's thoughts.

Larry
 
Hinge nut plates

Slightly off topic of your question... One of the best mods (if you haven't already done so) is to add nutplates to the door side hinges. This saves considerable time taking on an off the doors especially if you glass over the hinge pockets for a McMaster Carr door seal.

s7mY32tjV2T6pYo6TjD66G4qzqSB1W5en2SD8xstSTif7h2xVzA7njp6h5R1rGVuvfzTmYrUZMYGbDLQSfmbc2_YMMQ78KzjK8Nl8g28IGtJswmPkqZN5_Hte-6E82ZJhUPAfs3vqZKOXX5q47f23qieM4MSDh1ZdWaakXraSXXwJ_LEMpkQeqhCN2UwmU9Fcylb7aAC9xZeA9aCrJqJ1I8ryM_MhSRSnsDoMzZDjE16AwrgfGuJwsFVToY1yT1tE9U_jI-dIki_R85jTFSrrFBcpiziiWsI6RvDP_Fy6vN4nfIbwL3NN-AK3Kt7TK4G8YUHTyV48yslRr9k2BmB9IKKyD3P4EzShbbw6FwGf1IPo4lnPvTN4NhfLSCrppjpt3JgM4yb2-xybiIW1Q8_59_EsjwuHmkMH-4My3575ahKx6Nw6FheoC1Jkv40pQvXpBJeAf_ypBI39yVkdRa797Jy_7PAXvDFDIAotHfsv0kFR5OxPO5kR6nktiP3f3gQT1ZIKhwRJtCcctr9RHc127ZfjcMVqpah26XURG9NFkH5rexKjqN4ujlp8B2R9qkazIEd4ot3AGKVCOTVSFmXgRdmdq_cZcVt3C_2aqcFSNuh-z-dBB1a__AYnTyK3gHPGHyfhTZxQNAHV9QTY0AdiI9s2AIPLZ44VCTprWLUiAR_p78QfwyPW0Y=w575-h766-no
 
rvanstory said:
Slightly off topic of your question... One of the best mods (if you haven't already done so) is to add nutplates to the door side hinges. This saves considerable time taking on an off the doors especially if you glass over the hinge pockets for a McMaster Carr door seal.

s7mY32tjV2T6pYo6TjD66G4qzqSB1W5en2SD8xstSTif7h2xVzA7njp6h5R1rGVuvfzTmYrUZMYGbDLQSfmbc2_YMMQ78KzjK8Nl8g28IGtJswmPkqZN5_Hte-6E82ZJhUPAfs3vqZKOXX5q47f23qieM4MSDh1ZdWaakXraSXXwJ_LEMpkQeqhCN2UwmU9Fcylb7aAC9xZeA9aCrJqJ1I8ryM_MhSRSnsDoMzZDjE16AwrgfGuJwsFVToY1yT1tE9U_jI-dIki_R85jTFSrrFBcpiziiWsI6RvDP_Fy6vN4nfIbwL3NN-AK3Kt7TK4G8YUHTyV48yslRr9k2BmB9IKKyD3P4EzShbbw6FwGf1IPo4lnPvTN4NhfLSCrppjpt3JgM4yb2-xybiIW1Q8_59_EsjwuHmkMH-4My3575ahKx6Nw6FheoC1Jkv40pQvXpBJeAf_ypBI39yVkdRa797Jy_7PAXvDFDIAotHfsv0kFR5OxPO5kR6nktiP3f3gQT1ZIKhwRJtCcctr9RHc127ZfjcMVqpah26XURG9NFkH5rexKjqN4ujlp8B2R9qkazIEd4ot3AGKVCOTVSFmXgRdmdq_cZcVt3C_2aqcFSNuh-z-dBB1a__AYnTyK3gHPGHyfhTZxQNAHV9QTY0AdiI9s2AIPLZ44VCTprWLUiAR_p78QfwyPW0Y=w575-h766-no
Click to expand...

I second this. It was very easy to do and quite a bit cheaper than the rather expensive product mentioned earlier.

Has anybody fabricated a decent looking cover for the hinge on the cabin top side? I?m thinking about perhaps making a small cover of some sort that will screw into the hinge itself. It would be pretty simple to tap a small #6 drilled hole or two.
 
Yes

I made stainless covers for the exterior hinge pockets...the hinge was drilled and tapped for two 6-32 screws. I think I used 025 SS for the covers...
 
I made a plate holding 4 floating nutplates.
Then made up a super dry fluffy spheres mix and filled the whole hinge pocket.
Taped and waxed the hinge first.
Once dry, pulled the hinge out and sanded back the fill to the door.

Now the hinge just slides into a perfect slot in the pocket and you bolt in from the outside. You wouldn?t even know there was ever a pocket there.
It has probably added some weight but likely also made the whole area a lot stronger. I toyed with doing epoxy then expanding foam then more epoxy but just went the simpler way.
I haven?t countersunk the door yet. As I?m repeatedly installing and removing I?m just using regular AN bolts.
Just another way.
 
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