Sticking the landing? Floor question

[Old Macdonalds]

Quick question for those who have replaced their floor in a pontoon style "egg" ie. closed shell at the bottom ...

How did you stick the floor down?
I have been watching a ton of boat building videos where they are mixing resin, silica and chop strand to make a "peanut butter" paste to stick their floors down to the stringers, and doing filets and tabs along the edges. This is after they have applied a layer of chop strand to the underside of the floor to give it something to laminate to. They then put a couple of layers of chop strand on top to seal the whole thing.

Any suggestions or is this the road I should be following? Getting everything prepped so when the weather gets warm enough I can get to it.

[John in Michigan]

Was there previously subfloor and finished floor layer that was removed? Or what?

For example: The Trillium has a molded fiberglass shell bottom with "pontoons" molded along the starboard and port edges. Above that bottom shell is a plywood subfloor, then above that is an internal molded shell "finished floor". All layers are bonded together with polyester resin.

[Old Macdonalds]

The Surfside is nearly identical to the Trillium and ours has the plywood between the shell and the glassed-in floor but was rotting at the door, over where the fridge/ heater vents are and under the sink. It had almost disintegrated at the door because there was a metal threshold with screws and water had obviously infiltrated there. Wouldn't even hold the screws. The fiberglass had crumbled away from the opening because the plywood had gone soft and so there was no support to that corner of the body. The door therefore does not hang properly and that probably added to water leakage over the years.
I have already ripped out the floor in the front section of the trailer from the rise of the dinette, forward. Some came up easy and other spots were well stuck down. I have a new floor cut out and will be taking the grinder to the shell in a few places that still have some build up, this weekend. Without a heated shop I need to wait until the weather is warm enough to cure the fiberglass. We just had a foot of snow dumped on us last weekend but we are just above freezing during the day now so it is going quickly. However, I would like to be able to get straight at it when I can and there is a sale on resin, chop, etc at Princess Auto this week so want to have all my tools, supplies etc. ready to go. If I need extra mat, now is the time to get it. Any advice from the forum for expediting this project would be appreciated. I told my husband I am planning on having it back on the road by July and he is giving me the "Sure, whatever you say, honey" look.

[David Tilston]

Cate, What interior version do you have? Is it a front kitchen, (fibreglass interior) or the side kitchen, (wood interior)?

Pictures would really help.

[Old Macdonalds]

Empty interior at the moment except for some ratcheting cargo poles propping up the roof. Was a side kitchen with sketchy wood built cabinets. Curbside closet framing was warped and not doing much to support the roof. Just pinned together with brad nails into butt joints. I will be rebuilding with joinery, pockets screws, biscuits and glue for strength. Dinette is already framed and in pieces in my garage. Once the floor is in then glassing in wall to roof reinforcement and bring the egg back into shape. Have already moved the roof vent, patched and started last fall glassing in roof ribs in kerfed western red cedar. Have a bunch left from another project so will incorporate into the build for its resistance to rot. Roof took a snow load at some point. Once the egg is stable, I will pull the frame. Have already built the cribs. Have a friend who is a welder/millwright who will inspect it and let me know if it is salvage or scrap. New Flexiride axle to go in either way and then hook up the brakes and lights. Even empty, as long as the frame and egg are stable then a mattress, cooler and sleeping bag means we are on the road, at least locally. I have my summers off so road worthiness is the first goal. Luxuries like running water and cabinets will come. Have to figure out how to post pics.

[John in Michigan]

To your initial question regarding the bottom shell and floor, both my Trillium 4500 and my Boler 17 are "clam shell" molded fiberglass, so if I crawl under the trailer and look up I see molded gel coated fiberglass. In both trailers, there is a molded fiberglass pontoon or gutter along the edges. This clam shell is laid directly onto the steel frame, then a 1/2" or 5/8" plywood subfloor is either tabbed to it (Boler 17), or adhered to it with polyester resin (Trillium 4500). There are no ribs in the floor. To secure the body to frame, bolts run down through the plywood subfloor and fiberglass shell into steel flanges welded to the steel frame, then are secured with nuts.

[Old Macdonalds]

Thank you John for your input. I think I have been unclear as to what I am asking regarding the floor. When I took out the front floor it was adhered to the shell both at the edges in the form of tabbing and to the flat fiberglass surface that rests on the frame. As I mentioned before, the Surfside is almost identical to the Trillium. I would not be surprised to learn they are the same mold. The front floor was bolted to the frame with four bolts which I ground off to remove it. They were quite compromised with rust and so I will be replacing them with elevator bolts. I am now working with an empty shell and I am simply asking about methodology based on the experiences of others who have already done this job.

In adhering the plywood to the shell, the boat builders I have watched, cover the downside of the plywood with chop strand mat and resin and seal all the cut edges. Once set, they then mix resin with 1/4 inch chop strand, and silica to form a paste. That is applied to the top of the stringers and the plywood is dropped on top, chop side down. It is weighted until cured and is similar to how I have used a construction adhesive on joists in house building. It is also the method boat builders use for adhering mounting blocks and to facilitate wrapping perpendicular surfaces. As there are obviously, no stringers I am wondering whether this paste method is appropriate for such a broad horizontal surface as the shell or if

A) I should apply chop strand to the downside of the ply and then once cured, apply just resin to the flat surface of the shell and drop in the plywood onto the wet resin.

Apply resin and chop strand to the shell and drop the bare ply on top of it while wet.

or if I would get a better lamination if

c) I also embed a layer of chop strand in resin to the shell and drop the plywood (with cured chop strand on the down side) on top while it is wet.

It all has to do with how much resin and chop strand and possibly silica I need depending which method I use and if the last one is just overkill or necessary to get out the air bubbles and give a better lamination. It is my understanding that a good floor installation helps with load transfer of the roof and walls to the frame.

It will be weighted and bolted down to pull the plywood and shell together until cured
After achieving a lamination of the subfloor to shell I intend to tab in at the sides as was originally done, and then seal the upper facing surface leaving some edge gapping to allow for drainage into the pontoons. A finished vinyl floor will be installed over that.

Of course I could just glue the whole thing down with construction adhesive and hope for the best but I prefer to do it right, once.

[River Robert]

Every one here loves pictures

[John in Michigan]

Two structural patches that I applied were both located under the rear gaucho of my Boler 17. They both have a frame bolt at their center. In those cases I tapered the edges of hole in the surrounding floor, used a 1/2" plywood patch where the surrounding floor is 5/8", and joined the patch to the surrounding floor using chopped strand mat and polyester resin. Those patches have worked fine.

If I were to do it again having more experience now, I would first adhere the plywood patch to the fiberglass shell using polyester resin. Also instead of using chopped strand mat to join the patch to the surrounding floor, I would have used biaxial cloth and rolled it out with a fiberglass roller.

On a small patch near the door, I used a thickened epoxy product (PC-7) between the patch and the fiberglass shell, and around and above the patch. That worked fine as well.

[John in Michigan]

Cate, if you search threads on this forum, you'll find people have extensively repaired or replaced subfloors in Trilliums and in Amerigo FG16's. In those trailers, I am fairly certain the subfloor was originally adhered to the shell using polyester resin, and when the subfloor is replaced, either polyester resin or construction adhesive is used to adhere the floor. Tabbing can be done using biaxial fiberglass tape and polyester resin.

[John in Michigan]

Cate, I believe you stated you have removed all of the furniture and the subfloor. In this case you can't use polyester resin to glue down the new subfloor because it hardens too quickly. You must use either epoxy resin or a construction glue. Then lay heavy weights on the subfloor. Then install new frame bolts. Then tab the subfloor to the side of the shell with biaxial fiberglass tape and fiberglass resin.

If you haven't worked with fiberglass resin or epoxy resin before, read instructions carefully, watch some videos, and then practice before doing trailer project.

Again, others have done subfloor replacements with their Trilliums and Amerigo FG16's. You can search for those threads. Also, for fiberglass work in general, there is a good thread here:

https://www.fiberglassrv.com/forums/...ass-52498.html