Door latch pin plates

Hi everyone.

On page 45-17, the plans have you fabricate and install the fwd/aft latch pin plates around the pins. I'm wondering: are those still necessary if using the McMaster seal and the Planearound pin blocks (which are larger/fill the gap properly)? I don't really understand their purpose, so it's hard to tell.



Thanks
Rodrigo

In flight, the doors want to open. The pins bear against the metal latch plate aft of the door, and on the door the load is carried by....a tiny bit of fiberglass? The purpose of the plate is to have a metal piece which spreads the load out over an inch or two of the fiberglass.

BobTurner said:

In flight, the doors want to open. The pins bear against the metal latch plate aft of the door, and on the door the load is carried by....a tiny bit of fiberglass? The purpose of the plate is to have a metal piece which spreads the load out over an inch or two of the fiberglass.

Click to expand...

Thanks, that makes some sense.
Since those plates are attached by two rivets, however, isn't the load spread over just the contact area of those two rivets (another little bit of fiberglass)?

rdamazio said:

Thanks, that makes some sense.
Since those plates are attached by two rivets, however, isn't the load spread over just the contact area of those two rivets (another little bit of fiberglass)?

Click to expand...

Since the hole thru which the pins pass must be larger than the pins, the contact area there would be very small. Rivets, otoh, expand sideways to ‘fill the hole’. Also, the plate will have some friction in shear. Plus, in use, any grit on the side of the pin will sand the metal latch plate or, on its absence, the fiberglass. Fiberglass sands a lot easier than metal.

rdamazio said:

I'm wondering: are those still necessary if using the McMaster seal and the Planearound pin blocks (which are larger/fill the gap properly)?

Click to expand...

I did not install those plates. Used the PlaneAround pin blocks and 3rd latch with McMaster Carr seal too, so didn't see that it was necessary. 50 hours on the plane and no problems that I can see doing it this way. I think the key is that 3rd safety latch. With it in place, the pins won't have NEAR the pressure on them as the door won't be trying to flex open with constant pressure on the pins.

I fabricated my own door latch system mostly identical to the PlaneAround door latch system (hint: A LOT of work. Better to buy the PlaneAround kit!) and did not use the thin SS plates supplied in the finish kit.

I also made a custom door latch system, with a center latch. However, I used the std Vans approach, using the UHMW pin blocks in the door. That is 1" thick, strong plastic that is screwed to the door. From my view, this is the mechanism that takes the shear load from the pin to the door. I assumed the metal plates were related to the Vans seal that I didn't use and therefore did not install them. I didn't see how they added any significant strength in shear beyond the block and assumed their purpose was to help sealing. I put filler around the blocks to make a good seal with the McM seals. If you door frame blocks are not built wider than spec'ed, these plates can be used to scrape paint off of your door jam edge.

Larry

rdamazio said:

Hi everyone.

On page 45-17, the plans have you fabricate and install the fwd/aft latch pin plates around the pins. I'm wondering: are those still necessary if using the McMaster seal and the Planearound pin blocks (which are larger/fill the gap properly)? I don't really understand their purpose, so it's hard to tell.

Thanks
Rodrigo

Click to expand...

Those plates protect and secure the VANs style (door mounted ) seal when opening and closing the door, since the seal could easily get caught up on the pin blocks in the door frame. The pics show what these plates look like installed. I ended not liking the VANs seal and removed it.

The plates are not needed with the Planearound latch and door frame mounted seal. In that case the delrin blocks will come in close contact and align the door as you close it.

A bit of advice when fitting the door latch and doing final adjustments of the door. Do it with the door struts installed as it adds a bit of twist to the door. It has the effect moving the lower part of the door aft since the loading is at the upper aft part of the door. You may find that you need to move the door forward when closing it to align it. I was able to compensate for this by using washer shims on the door hinges. It is an iterative and somewhat frustrating process, but you can get it to line up nicely in the end.