Glassing Cowl Rivet Lines ? Pondering ?

BillSchlatterer · #1 11-16-2008, 09:40 PM

I'm wondering what those that glassed over cowl rivet lines used and how much of the cowl rivet lines did you really cover?

It seems to me that you can cover all the way out to the hinge edges and then fight getting the edge straight again or just barely cover the rivet line and maybe you won't get a line that shows where the glass lays between the rivet line and the edge?

I have some 1.8 oz glass and I was considering going not quite to the edge and then just fill and sand lightly with one layer of the light glass. I really don't want to mess with the edges again as they are just about right but I don't want to have a bump where the rivet line is covered?

Any thoughts, comments, help from those that covered them would be appreciated.

Then again, the rivet lines are very flush and the hinges are glued in and shouldn't move so is it really worth the trouble?

Thanks Bill S
7a Finishing

PS. Pondering is what passes for thinking in Arkansas,... just happens a little slower :-)

rvbuilder2002 · #2 11-16-2008, 10:23 PM

Quote:

Originally Posted by BillSchlatterer

Then again, the rivet lines are very flush and the hinges are glued in and shouldn't move so is it really worth the trouble?

No, it's not worth the trouble.
The prepreg. material your cowl is made of is very hard and stiff.
As long as your cowl is installed without any preload on the hinges they will hold up great...even if you hadn't bonded them to the cowl.

jsharkey · #3 11-17-2008, 05:34 AM

Quote:

Originally Posted by rvbuilder2002

No, it's not worth the trouble.
The prepreg. material your cowl is made of is very hard and stiff.
As long as your cowl is installed without any preload on the hinges they will hold up great...even if you hadn't bonded them to the cowl.

I agree - you are meant to see the rivets on an RV and marvel at their flushness

Seriously though it will just add weight, work and expense for no real benefit. Light and simple is the Van's way.

Jim Sharkey

DanH · #4 11-17-2008, 07:59 AM

Assuming the rivet heads are flush or just a fuzz below the surface, one or two wipes along the rivet line with epoxy and a squeegee (no glass fabric) will flush and seal it nicely. Just block sand it flat, then start your weave fill and paint prep.

AMURRAY · #5 11-17-2008, 12:45 PM

I might get some VAF bashing, but yes I put a fiberglass strip over the rivets. I never even heard of this until I talked to a multiple Lancair builder. I think it was 10 plus Lancairs. Of course they use carbon fiber. A little out of my budget. I used 5.6 oz 2 inch fiberglass tape and trimmed it to 1 1/2 inches. I positioned the tape about 1/8 to 1/4 inch to the edge of the cowling. I then sanded, filled and feathered the edges of the tape. I also covered the rivets on the wheel pants and gear fairings. I didn't take much time at all. Most of the smoking rivets I have seen on RV's have been from the fiberglass areas.

Bob Axsom · #6 11-17-2008, 01:16 PM

Quote:

Originally Posted by rvbuilder2002

No, it's not worth the trouble.
The prepreg. material your cowl is made of is very hard and stiff.
As long as your cowl is installed without any preload on the hinges they will hold up great...even if you hadn't bonded them to the cowl.

The two bottom hinge installations popped rivet heads after some flight time was accumulated. Went to next size larger dia rivets and they started "working" also. I came up with another installation using screws. Had I covered the heads with fiberglass it would have been difficult to detect the failure and to drill them out in the traditional way.

Bob Axsom

allbee · #7 11-17-2008, 02:38 PM

two ways to do this, you can sqeeze the rivets the normal way, than take a grinding burr and grind it in just a smidge and than put filler over the top. Or you can take the hole for the rivet and pt a taper cut with a cutter and let the rivet set in just a smidge, now comes the tricky part, how to set the rivet with it set in just a we bit, simple, take your revit sqeezer and put a flat die on one side and take a dimple die for the #8 screw and put that on the side for the rivet head, very carefully sqeeze the rivet, with flat die twards the back of the rivet and the nobed die for the dimple die set on the rivet head. Walla you have an incased rivet.

allbee · #8 11-17-2008, 02:40 PM

OH I also took the dimple die and put a flat on the face with a grinder.

rvbuilder2002 · #9 11-17-2008, 05:26 PM

Quote:

Originally Posted by Bob Axsom

The two bottom hinge installations popped rivet heads after some flight time was accumulated. Went to next size larger dia rivets and they started "working" also. I came up with another installation using screws. Had I covered the heads with fiberglass it would have been difficult to detect the failure and to drill them out in the traditional way.

Bob Axsom

Which cowl do you have Bob...the gel coated Polyester one or the epoxy one?

jsharkey · #10 11-17-2008, 05:54 PM

Although I have a tail dragger without the nose gear slot in the cowl I was still planning to add some extra mechanical fastening on the inboard ends of the lower cowl hinges to prevent them "peeling" due to flex, vibration and buffeting there. They are the only open edges on the cowl to bulkhead joints so they pick up peel loads. The rest of the joint is mainly in shear which is much easier for 3/32 rivets in fiberglass to react.

Does anyone have pictures of how they fastened this area?

(btw - Fiber glassing or filling over the rivet heads is for cosmetic reasons only and probably hinders detection of structural problems in the long run - just my 2 cents.)

Jim Sharkey