#$@& inspection covers

aftCG

aftCG

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Tacoma, WA
I lost one yesterday. I knew damn good and well I saw them all during preflight. I did some pattern work and tried out two new GoPro mounts. The one on the tail handle caught the cover departing on my first takeoff.

I lost one last summer and replaced it with the Aeronca 4-prong type. I just looked on Univair and that type is $35.50 each. The two prong disappearing type are only $7/each.

What is the gallery opinion on these covers? Buy once, cry once?
 
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A #4 sheet metal screw and a Tinnerman nut will allow you to use the inexpensive dome type from Spruce. Last time I bought a handful they were around two bucks.
 
Here's the listing for those inspection plates at ACS: https://www.aircraftspruce.com/catalog/cspages/inspectplate.php?recfer=21070
Note that they still have the "clip" on the back (like the ones on my plane), and are available in both "domed" and "recessed" styles. The domes ones are super-cheap ($2.25 each), but the recessed ones seem very reasonable as well ($5.95 each). They claim the recessed ones don't come off as easily, and I have no knowledge if that's true or not, but I'd probably spend the extra $3 to find out...

If you want to try the Tinnerman / screw route, ACS sells the Tinnerman nuts that would clip to the edge of your inspection ring, then you would need to drill a hole at the appropriate spot on your inspection plate to line up with the Tinnerman. You'd have to decide if you want to countersink the hole or not, and that would dictate which type of sheet metal screw you'd need (also available from Spruce).

Tinnerman nuts: https://www.aircraftspruce.com/catalog/hapages/tinnerman2.php?clickkey=5485 (No #4 size available, but #6 size should be fine.
 
JimParker256 said:
Here's the listing for those inspection plates at ACS: https://www.aircraftspruce.com/catalog/cspages/inspectplate.php?recfer=21070
Note that they still have the "clip" on the back (like the ones on my plane), and are available in both "domed" and "recessed" styles. The domes ones are super-cheap ($2.25 each), but the recessed ones seem very reasonable as well ($5.95 each). They claim the recessed ones don't come off as easily, and I have no knowledge if that's true or not, but I'd probably spend the extra $3 to find out...

If you want to try the Tinnerman / screw route, ACS sells the Tinnerman nuts that would clip to the edge of your inspection ring, then you would need to drill a hole at the appropriate spot on your inspection plate to line up with the Tinnerman. You'd have to decide if you want to countersink the hole or not, and that would dictate which type of sheet metal screw you'd need (also available from Spruce).

Tinnerman nuts: https://www.aircraftspruce.com/catalog/hapages/tinnerman2.php?clickkey=5485 (No #4 size available, but #6 size should be fine.
Click to expand...
Thanks. The upper link indicates:
"Recessed center and flanged-edge design will not creep off center due to vibration in propwash areas. 4-3/4" dia. x .020 aluminum. Will not twist or vibrate".

The one I lost (this time) is just ahead of the trailing edge near the cabin. It's very much in the propwash area as evidenced by the video I captured. As in "Damn, it moves that much?!?!" The way the fabric flaps around there I'm actually surprised the paint adheres to the fabric for any length of time. I'm still editing the video but I'll post it later. It's like looking out the back window on a C152 when you do a 360 steep turn and hit your own wake - it's something you would rather not have seen.

I'm also thinking there is economy in buying the cheap ones and making one 4-prong type of out two cheap two prong covers. I would be money way ahead, and the risk of screwing something up (drilling into my inspection rings) is much less.

Edit: Now I guess I need to get some of that blue paint you guys were helping me with...
 
The aerobatics guys have been using the P-K screws forever. Just one in the front is enough with the cheapies - plan the spring fingers at 45 degrees, and bend one of them for easier insertion.

Remember, these things are designed for "oil-canning" and should be inserted/removed in the un- domed state.
 
Bob Turner said:
The aerobatics guys have been using the P-K screws forever. Just one in the front is enough with the cheapies - plan the spring fingers at 45 degrees, and bend one of them for easier insertion.

Remember, these things are designed for "oil-canning" and should be inserted/removed in the un- domed state.
Click to expand...
can you explain that please? thanks
 
These two photos ilustrate a lot of things. First, the #4 screw - standard for aerobatic and high power/fast fabric airplanes. Note the dome shape - let's call that convex.

You take the screw out, then gently punch the dome - presto, er boink! Concave! Concave is the way to insert/remove domed covers.

Note the curled spring. Not necessary on this older, better plate (note the closely spaced rivets, allowing more movement upon insertion), but essential on one side of the Aircraft Spruce plates - spring steel does bend.

Also note - no Tinnerman nut. Those old plastic inspection rings are weak, and cause problems.. On this one I glued a semi-circular piece of aluminum inside the wing with a threaded hole for the #4. It popped off during this photo shoot, and is now being re-glued.

If you are covering a wing, use Steve Pierce's metal rings. Also use metal drain grommets, and always - always - cover these things with a fabric doily or surface tape. We Cub fanatics use metal for all imbedded plates, and the metal itself holds the #4 sheet metal screw.

I would trade, one for one, all of my non-domed covers, for these "closely spaced rivets" covers if you pay all postage. I think the non-domed covers are ugly, and they still have to have the #4 screw on the Decathlon. I might have ten of them!
 
Steve posts on the Cub forums - he sells .025 rings and Cub openings. Use his products. I personally prefer .032, because it holds screws better, but the time and material involved makes Steve's products a best buy.

On the drain grommets - thinner is ok, not that you are dealing with a great deal of weight saving. Most are now just poking holes with a hot soldering iron - I have not yet become that brave around Butyrate. I cut mine with a sharp X-Acto knife. I don't know anything about seaplane grommets, except to say that if I ever use them they will get small donut shaped fabric patches over the flat part.
 
I looked at the opening for my missing cover and it has a screw hole already. If there was a Tinnerman nut it has gone missing. Easy enough to rectify
 
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