Trillium Belly Band Removal Stell Plates, Trillium 4500

[Dino C]

Hello,
What is the best practice when it comes to whether or not one should remove the steel plates inside the open gap, when the belly band is removed from a Trillium 4500?
Should I remove them, or is it ok to leave them in place?
Thanks

[John in Michigan]

Depends on the condition of the plates. The majority of steel plates in my Trillium 4500 were badly rusted, many of them just brown powder. This extreme corrosion resulted in the fiberglass outer shell around each plate bulging outward 1/4" or more.

I ground out/cut out the fiberglass bulges and most of the plates (at least 40 plates). Then I sanded and cleaned out the center seam with acetone and patched it with fiberglass.

If the plates are intact, I don't believe they need to be removed. Just need make the seam water tight to prevent rusting.

[Dino C]

Thanks John,
That's helpful. I was informed I could use short stranded fibreglass Bondo to fill the gaps, then go over with bondo to sand smooth. Is that as good as 3M 5200 sealant?
Thanks

[John in Michigan]

Dino, I don't know. I used 3M bondo glass to fill the center seam gap then final finish filled with bondo filler. After a year or so there was some cracking on the rear side and the front left corner. It's possible I didn't lay in a thick enough layer of bondo glass in those areas. I ground out and repaired those cracks with thickened epoxy (pc-7 or pc-11 brand, don't remember which one).

How to avoid this problem? Here is my opinion. Instead of bondo glass:

1. Use several layers of woven fiberglass tape, or

2. Use epoxy with woven fiberglass or glass strands, or

3. Use 3M 5200 to fill the center seam, or

4. Use bondo glass, then apply a vinyl body side molding using a waterproof adhesive sealant such as 3M 5200 or a waterproof construction adhesive

[Steve Hague]

Dino,
When I removed the bellyband on our 1978 4500, I made certain to remove every steel backing plate. While I observed that there was plenty of fiberglass matting or tape to provide structural stiffness of the interior joint, however it did not consistently seal the butt joint around the plates. I feared any moisture that found its way under the Ensolite might eventually find its way to any remaining steel backing plates.
I used long-stranded Bondo Hair to first fill all the large gaps left after removing the plates. I next used short-stranded Bondo Glass to sculpt the general finished shape. After rough sanding I applied Bondo Gold. For my first fiberglassing project, I thought it turned out well.

[Dino C]

Hey Steve, Thank you.

[drdoyle]

Remove the old rusty steel backing plates. Fill the gap with spray foam. Sand flat. Apply two or three layers of 2 inch fiberglass cloth tape using west sytem epoxy resin. Sand smooth. Use a very thin "interlux- watertite epoxy filler" , use a plastic hand tool, sand and repeat. Finish with epoxy primer and color stripe of your choice.