Cowling and Fasteners on Kevlar Fiberglass cowls

[tls pilot]

A few hangars down from me, with bottom cowl off, I noticed the fasteners holes on the bottom of the cowl 

looked elongated and with little material left to the edge.  The plane is an older M model.

The fastener retaining rings not in place, thus the fastener pops out and one can see that the hole

is now bigger. 

Issue appears to be sooner or latter the fastener will go thru the cowling hole, then not holding anything but remaining

attached!

Anyone know of a fix?

Seems the area would need to cleaned of all the oil first, then would need to repair the entire bottom row

 

Any thoughts I can pass on would be helpful

 

[jetdriven]

They sell a 4002-OS Oversize retainer which fixes the wallerd out hole problem temporarily, but when that starts to pull through then you have to basically scarf out the fiberglass and rebuild it for about an inch all around. If you want to do the whole row your scarf the while inner half of the thickness  away, layup a stainless steel strip inside there with the 6 plies of 7781 to it so it has nice hole tolerance. Then you scarf away the outside replace that glass as well then countersink it. It’s a real hassle but it looks good when it’s done

Edited December 24, 2020 by jetdriven

[carusoam]

Vibration and metal parts in the cowling are tough for wear issues...

Byron has done a great job of identifying the challenge and the solution when he reworked his cowling... lots of description and pics for his 201...

PP fuzzy memories, but probably applies equally well to the M20M...

Best regards,

-a-

 

 

[M20F-1968]

Skybolt has fasteners with larger flanges which have greater overlap and can fix some of the problem.  Jetdriven's description is accurate.  The real fix is to grind out the fiberglass until you his the 1 1/2" or so wide metal strip embedded in the fiberglass.  This metal strip needs to be replaced, re-fiberglassed and new holes drilled.  Using the Skybolt fasteners would be a plus.  The 4000 series are adjustable and the size is appropriate fir the cowling/firewall interface.  They have larger flanges.  The 2000 series are smaller, can be used between the top and lower cowling, and can also be ordered with a larger flange.  This will delay wear of the new holes as well.

If you hollow out the inside of the cowling, you will save repainting, but you will need to re-fiberglass and sand to fit the old dimensions.

John Breda