Fiberglass Cowl Problem

[Boelkowj]

Hello All: I have 10-32 screws with 8s size Tennerman Washers as attach
fittings. The cowling holes have worn slowly but surely and now I know it is
time to fix this vibration problem. I like the size of the 8s but I suspect I
really should use 10s. They are unpainted and not bonded to the cowling. My
questions are 1) I think the solution would be to epoxy the Tennermans (larger
size ) to the cowling now that the hole is getting too big. 2) Should I flox
them in place from inside for a more secure bond? I haven't been bothered
before now with the washers "free floating" for lack of a better word. I've
liked the chrome look but maybe they should have been bonded when I had the
cowl Emron painted 200 hrs ago. What seems to be the conventional fix for this
problem as it will only get worse if I don't do it right soon? Thanks

Larry

[Boelkowj]

Thanks for your input. The backside ie. inside the cowling "dimple poke through
around the hole" I thought could also be epoxied with some build-up so that the
tinnerman is that much more secured in place around the inside surface as well.
I'll give it a try with straight epoxy and cleaned surfaces. I was sort of
thinking that someone should invent a very nice snap together or screw together
front and back tinnerman washer just like the other types of cowling fasteners
but have a nice finished tapered stainless steal screw appearance. I hope I
haven't confused you..Thanks for your input.

Larry

[pacplyer]

(Boelkowj) wrote in message >...
> Hello All: I have 10-32 screws with 8s size Tennerman Washers as attach
> fittings. The cowling holes have worn slowly but surely and now I know it is
> time to fix this vibration problem. I like the size of the 8s but I suspect I
> really should use 10s. They are unpainted and not bonded to the cowling. My
> questions are 1) I think the solution would be to epoxy the Tennermans (larger
> size ) to the cowling now that the hole is getting too big. 2) Should I flox
> them in place from inside for a more secure bond? I haven't been bothered
> before now with the washers "free floating" for lack of a better word.

Larry,

If your Tennerman-style fastners are the "clip" type, the floating
over the holes serves as a self-alignment process for cantankerous
cowlings and you might loose that benefit by epoxying them in place.
Hard to say if that's important without seeing your machine. Could
you install nut plates instead? They would still internally float
making it easy to align the cowling screws. You haven't lived until
you've pulled annuals on 40 year old Appaches. Talk about cowling
problems...

Good luck

pac "PK10" plyer

[Bob Kuykendall]

Earlier, (pacplyer) wrote

> If your Tennerman-style fastners are the "clip" type...

Um, I think that he's talking about Tinnerman washers (the dimpled kind) like these:

http://www.aircraftspruce.com/catalog/hapages/nas549washers.php

And you're talking about Tinnerman nuts like these:

http://www.aircraftspruce.com/catalog/hapages/tinnerman.php

I hope that helps clear things up.

Bob K.
http://www.hpaircraft.com

[pacplyer]

(Bob Kuykendall) wrote

> Um, I think that he's talking about Tinnerman washers (the dimpled kind) like these:
>
> http://www.aircraftspruce.com/catalog/hapages/nas549washers.php
>

Thanks Bob,

I see now that Larry's talking about bonding the dimpled washers to
the cowling itself. I didn't RTFQ right (read the f#$%&#$g question.)
:--)

On using different size washers and screws, I say mix em' and let em'
float till your friends start making fun of em'. It is iffy to use an
oversized dimpled washer under a smaller screw to span the enlarged
cowling hole. So I used to insert a thin wide stainless washer
between the smaller screw head and the oversized dimpled washer and it
looked and held great (experiment with different sizes until it
recesses.) But then you had to remember the 3 peice set-up at that
hole when re-cowling which was hard. So I would pen a little "3" by
the cowling screw hole with a fine-tipped permanent marker to remind
myself that something was different here. After all, these were old
twins with a patch here, a patch there... an Apache everywhere. You
might not want to put ink on the cowling paint on you airplane.

Remember, some people will do anything to delay rebuilding their
cowlings! ;-)

pac

[Boelkowj]

Thanks all for your suggestions. The 8s and 10s tinnerman washers both work
with the 10-32 flathead screws. I'll use the 10s to insure a better grip. The
holes in the cowling itself are now about 1/4 inch in diameter and I think the
10s washers will work OK just so long as I choose the correct epoxy to get the
washers to bond to the cowling after all is aligned correctly. I have heard
that the "metal weld A/B" works pretty good with bonding washers to fiberglass.
The cowling was initially designed to use tinnerman washers ...the problem is
the holes just got bigger due to normal vibration and I would like to fix it so
this won't happen again for a long time if possible.

Larry

[Blueskies]

rig up a little spotface tool and pilot off the existing (oversize) hole, Use some sandpaper on the face of the tool and
lightly sand through the paint. If it is just the right size the washer will cover the spot and you will still have the
'chrome' look after you glue them in place. You could probably get away with the spot face diameter being a little
smaller than the washer diameter....

--
Dan D.



..
> wrote in message ...
> In article >, Boelkowj says...
> >
> >Hello All: I have 10-32 screws with 8s size Tennerman Washers as attach
> >fittings. The cowling holes have worn slowly but surely and now I know it is
> >time to fix this vibration problem. I like the size of the 8s but I suspect I
> >really should use 10s. They are unpainted and not bonded to the cowling. My
> >questions are 1) I think the solution would be to epoxy the Tennermans (larger
> >size ) to the cowling now that the hole is getting too big. 2) Should I flox
> >them in place from inside for a more secure bond? I haven't been bothered
> >before now with the washers "free floating" for lack of a better word. I've
> >liked the chrome look but maybe they should have been bonded when I had the
> >cowl Emron painted 200 hrs ago. What seems to be the conventional fix for this
> >problem as it will only get worse if I don't do it right soon? Thanks
> >
> >Larry
>
> Bonding the tinnermans to the cowl is a good idea, but you're right, you should
> have done it before you painted, you want to bond to the fiberglass, not to the
> paint. You can make a mask, the same size as the washer OD, and sandblast off
> the paint in just that area with a recirculating sand blast gun and bellows.
> Then sandblast the back side of the washer, and epoxy in place. I don't
> understand what you mean by floxing in place from the back side.
>
> If you like the size (OD) of the 8's, you can put a stack of 10's on a flush
> head and lathe or belt sand them smaller. Count on a bunch of destroyed washers
> if you do, they're cheap.
>