Getting ready to repair the floor of my 1977 Trillium 4500

[Dino C]

Hi,
I recently purchased a 1977 Trillium 4500.
When I removed the tray beneath the porta potty under the front bunk, I realized the floor was rotten.
I planned to change the front bunk to a dinette, so I figured while I was at it, I'd repair the floor.
I have begun the repair.
As I removed the upper fiberglass sheet in front of the door way, and pulled off the rotted wood, I noticed that the lower fiberglass layer was not even. There were raised sections of epoxy.
How would you recommend I address this? Use fiberglass reinforced bondo to even it, before installing the plywood?

Any tips would be appreciated.

Cheers
Dino

[BASE1360]

I can’t tell how much lower the low spots are but I am assuming it’s not much. If you haven’t done the repair yet (I see I am responding a week after you made the post), you could use fiberglass filler to level it or just maybe fill the areas with a little more resin when you are adhering the plywood. Also, if you haven’t given it any thought, replace the bolts that attach the trailer body to the frame. They’ve been known to rust out.

[Dino C]

Hey thank you for the reply.

It turns out that the raised areas weren't solid epoxy as I feared, but actually raised section of delaminated fiberglass cloth. I used my multi tool to cut out around the perimeter of the large raised areas, to now only have a tapered edge with the thinness of fiberglass cloth around what used to be the raised sections 1/8 to 1/4" high.

I've removed all the wood on the floor from the front gaucho/bunk to the central area of the floor in front of the dinette.(It's a 4500). I have kept the upper fiberglass/Gell coat layer to reapply.

The 2" or so of remaining plywood under the edge of the closet and kitchen seems to have dried out, being exposed to air, and seems somewhat structurally sound. I don't know that I want to attack the much bigger job of removing those sections.
Perhaps they are ok, or I should inject wood hardener or epoxy, while I have access to those areas??

I need to have instruction on how to apply the new flooring. My questions are:

1) Should I do anything to smooth out the exposed bottom fiberglass layer? Add bondo filler? Epoxy resin? Epoxy resin with filler?

2) I measured closer to 1/2 " of removed plywood from the floor, not 3/4". Either way I am thinking to use 1/2" and use expoxy and fiberglass cloth to get to level. I am of the impression that I am to sand the bottom fiberglass layer of the trailer floor, wet in a sheet of fiberglass cloth(matt or cloth?), and lay the wetted plywood on top, then weigh it down or screw from underneath to pull those layers together? Then sand and wet the upper surface of the new plywood floor, and add another sheet of cloth, then add the original upper layer of the fiberglass & gell coat floor, and weight it down to bond.
Does that sound right?

3) Any other things that I am missing or can help?

Please feel free to make suggestions.

Thanks

[BASE1360]

It sounds like your bottom layer of fiberglass is now fairly smooth and flat since you removed the high spots. When I did my floor, I did put some resin over the area that wasn’t quite flat and let it cure. I then sanded it flat. It didn’t take much resin and it wasn’t very thick either.

The procedure you described in 2) sounds pretty spot on with what I did. You are correct in thinking getting under the closet and galley would be a lot of work. If the wood appears to be strong, I would just seal the exposed edges with resin/epoxy as a precaution. Injecting resin/epoxy or wood filler would be a judgement call as I can’t see/feel the wood for myself. I tend to err on the side of caution, however. Also, I didn’t use screws to help bond the new plywood to the fiberglass bottom. I just used weights spread over the area being repaired and made sure the floor under the trailer was also supported.

One more thing to take into consideration is your door alignment. Does your door sag? If so, it is possible floor rot compromised the structural integrity of the trailer and you might be dealing with a sagging corner. But, door sag can also be caused by rotten wood behind the door hinges. If door alignment seems off it would be worth investigating before you glass in the new floor.

[Dino C]

I had to repair the hinges already, so I am unsure if there is sag. I drilled holes and epoxied dowels, then reattached the hinges/door. Is there a clear way to determine if there is sag? Thank you for your time.

[BASE1360]

I didn’t have to deal with body sag and I think it’s less of an issue with Trillium’s because the plywood floor is glassed to the walls. I don’t know the history and condition of your trailer so it could be a non- issue for you too. If you run a level/straight edge from the center of your floor to a front corner and the floor doesn’t fall away from the straight edge as it nears the corner then I think you should be good. Of course, this is assuming you don’t have any highly spots on the floor that affect the straight edge. Google fiberglass rv and body sag and you should see a a few forum discussions on this topic. Using google instead of the search function on this website is better.

[Dino C]

OK..I'll look...thanks