Replacing white plastic rivet/screw covers

[WayneJ]

This spring I will be renovating a 1985, 16 ft Scamp that I bought last summer. The trailer had lots of leaks, including around the rivets attaching the upper cabinets to the trailer. I have gutted the trailer. I am planning on replacing the rivets with new SS screws (maybe nylon screws?) and also replacing the screw covers themselves. As best as I can, I want to eliminate all sources of leaks. Does it make sense to use some type of sealent under the screw cover - that is between the screw cover and the outside fiberglass skin of the trailer? Or will the srew holes remain leak free with just proper tensioning of the screw fastners?

[Brian B-P]

If I were going to seal this combination, in which I believe the base of the screw cover acts like a washer between the screw head and body, I would coat both side of the screw cover with a sealant suitable for gasket service, sealing both the body-to-cover-base and cover-base-to-screw-head interfaces, since they are the two paths from the outside world to the screw hole. This is the approach I took with the machine screws and washers (not screw head covers) that hold my MaxxFan vent - there are no leaks but that has only seen a few months of weather so it is not a particularly useful test case.

I'm not sure if "screw" here means self-tapping screw engaging the fiberglass, or a machine screw passing cleanly through the shell and having nuts on the inside. I have used self-tapping stainless screws on some minor covers and vents, but would have much more faith in nuts and bolts maintaining tightness, especially for something carrying load like a cabinet. I'm not a big rivet fan, but they do grip the shell without depending on a tiny bit of thread engagement, and don't loosen by turning.

By the way, I suspect (only an offhand guess) that a nylon screw would need to be so large to have adequate strength that it's not a practical option - but it sure would be a corrosion solution!

[Jackie]

I have a standard S13 - so the cabinets are held up with rivets. When I gutted the trailer, then put the cabinets back in, with the rivets again, I filled the hole (through the shell and into the cabinets) with white caulking, then put the rivets through the snap-cap base hole and set in place. I then filled the base with caulking before snapping on the covers. No leaks.

[Frederick L. Simson]

Or will the srew holes remain leak free with just proper tensioning of the screw fastners?

The Fiber Stream has a wood interior, so it uses screws; not rivits.
The original finish was just a dab of caulk over the screw head. After cleaning all the old caulk out, I filled the screw hole with caulk in a similar manner to what Jackie did; but I merely snapped the cap over the top without additional caulk. After having dug caulk out of the screw slots once, and knowing I wanted to periotically check & adjust screw tension, I wanted the screw heads accessible.

[Loren G. Hedahl]

I'm not sure whether this has any value or not, but . . .

Have you ever been the Home Depot or competitor and seen those screws they use for installing metal roofing?

They have a 1/4 inch hex head and use a "beleville washer" followed a rubber sealing washer. The beleville washer is a larger than normal washer, but not as large as a fender washer, that has been pressed to a cup shape.

The sealing washer and gasket is the part of interest.

When the screw is tightened, the cup shape acts like a spring that retains the rubber gasket and compresses it inward to also seal off the shaft of the screw. Additionally the cup compresses and seals the outward edge of the rubber washer keeping it from being deteriorated by the elements. (Not the Honda Elements.)

I would bet someone sells these in stainless.

[Brian B-P]

The Belleville washer is an interesting idea. While they have been described as "cup" shaped, I think perhaps "cone" shaped is more accurate, and would avoid confusion with finishing washers, which have their uses but I believe are not what Loren is describing.

Both types of washers are available in stainless steel.

[Con]

If you read this thread you get some guidence re: sealing & pop rivet alternatives.
http://www.fiberglassrv.com/board/index.ph...opic=18751&st=0

[Mary F]

And here's a "Legacy" thread on Replacing Rivets with Fiberglass that touches on the (in-)advisability of replacing aluminum rivets with stainless.

[Benny K]

I had spider checking in the fiberglass around a few of the aluminum rivets that held up my upper and lower cupboards, but I went across the grain when I replaced them 3 years ago and used 3/16" stainless steel machine screws rubber washers cut from tire tube on some and neoprene "O" rings on others with SS washers and SS acorn nuts on the inside...will see which last longer.......no problems yet.....no water leaks...no difference in the spider checking .....cupboards haven`t fallen off yet leaving big holes in the shell, LOL....the only problem I find with all of these fasteners is that there is no thermal break in them or any insulation on the washers and acorn nuts, so condensation drops form on them on cool nights when the trailer is heated at the same time it forms on the windows and frames...There is some credence in what Wayne mentioned about nylon screws but the diameters would have to be way too great but maybe carbon fiber fasteners could work and not have a condensation problem ......this was probably where some of the rust was coming from on the acorn nuts on the original POP rivet type fasteners, and not external water leaks......Benny....oh, I also used some tap washers as gaskets under a couple of screws also