I would drop the belly pan. It would not compromise the floor, and you could get to everything under the coach, replacement would only require a box of aluminum rivets, instead of cleats or fishplates, or gusseting the floor.
The downside would be that you would be doing the work lying under the coach (although you could catch a nap that way), and the fiberglass would tend to get all over you (wear old clothes you want to throw away anyway).
While it would be a bit messier working from underneath that is a reasonable way to do it. Consider using a mechanics crawler to lay on and roll yourself around. I bought one and it helps a lot. Of course you do have to jack the AS up a bit so that there is enough room to roll around underneath. Jack stands under the ends of the heavy metal strips that the axle is bolted to makes a great support. I also used a bottle jack under that metal in between my tires to raise the rig. I did find that I could not remove the part of the belly pan that was above the axles without removing the axles though. There were not difficult to get off but I did have to buy a small floor jack to do it. They each way 200+ pounds. Also you will find propane lines here and there in the way of taking off the belly pan. You will also have to remove the leveler jacks from underneath since they are in the way of taking off some of the belly pan. You might want to check the overall condition of your belly pan. I found that I needed to take some of mine off anyway since it was coroded here and there and needed to be replaced.
With all the stuff in the way of working from underneath cutting out the floor like you suggest might not be a bad idea too. Some strips of plywood along the seams would give you something to glue/screw the middle piece to. The glue and screws along the joint would make the results pretty much as as strong as the orginal. When I replaced my subfloor I left about 1/2 of my belly pan on since it was in very good shape. So I removed and replaced the floor in that part entirely from above with good success. I did use gussets at the seams like you suggest. If it can work for the whole floor I don't see why it wouldn't work for just part of it.
The bottom line is that both approaches would work and it is your choice which way would work best for you.
Bob, there's no single answer. The bellypan area does get air circulation and wet insulation shouldn't do permanent damage while it dries out -- if the floor was sound to begin with and all leaks are fixed. Enclosing the trailer and using a dehumidifier for a week or so could speed the process.
Removing floor where you'd walk would bother me. The floor would lose its membrane rigidity in the horizontal plane. This is the same reason you want your home subfloor to cross multiple joists. Side-to-side frame crossmembers would greatly restrict any useful access you might make from above. You'd almost have to drop the bellypan anyway if your inspection actually found something to be done.
[on edit:] Y'know, these floors are only 1/2" anyway. I really wouldn't cut into it unless I had to and the area was under bed or cabinet where no foot load was taking place. Screws and a backing board just aren't going to hold up to load in my opinion.
__________________ . BobStream
...You really don't know someone 'til you've had recess with them. ...Alex Ziton, age 8
You can easily cut inspection panels in belly wrap and rivet slightly larger patches back in place.
Frame and crossmembers are in full contact with the floor underside. Glassing the floor could add significant weight that is not in the original design and would reduce your useful load correspondingly. Get to a CAT scale after project completion to assess fully.
Insulation has its best input on the trailer sides and above you. Sad to say the shell insulation is pretty minimal in R value. I wouldn't go overboard on floor insulation -- fiberglass stapled to any floor you reinsert should be good. Most foam will fall all apart with vibration & structural movement while underway. I would be concerned about it hiding & holding moisture up against the floor underside -- but I have done it under a gaucho -- pictures here. The foam was laid in and supported on the A-frame which was the right thickness below the main structural frame -- I didn't have to puzzle over fasteners. I then stapled fiberglass to the new floor outside the frame between the outriggers.
I'd still hesitate doing this just to dry out fiberglass -- that stuff is only 2" in the first place. Inspection value from above is still minimal IMO and you'd be challenged to do anything useful from above. By comparison crawl under your trailer and imagine how much easier cutting and patching a 2' x 3' hole in bellypan would be! Belly skin lap joints never were intended to be watertight and should not be sealed due to need for circulation/drying.
__________________ . BobStream
...You really don't know someone 'til you've had recess with them. ...Alex Ziton, age 8
You can remove an edge piece of belly skin right where it meets the side wrap. Is the width of your trailer just under 8'? The fore and aft main frames are somewhere around 4' on center and outriggers are approximately 15". So yes, you can access outrigger areas this way.
Around any plumbing or trailer perimeter I would hesitate very strongly before installing foam right up against the underside of the floor. Any moisture between that and the floor would never dry and you'd get floor rot for sure. Short answer -- a strong 'no' to spray foam.
There are all sorts of hits about if you search the Forums on: aluminum .025"
__________________ . BobStream
...You really don't know someone 'til you've had recess with them. ...Alex Ziton, age 8
I don't know which way is better, but I have been able to get quite a bit of work done under the trailer while it's up on my homemade ramps. Gives quite a bit of extra room, but that doesn't mean it's fun. Here's a picture.
__________________
ingrid
1967 24' Tradewind #19104 ~ Forums #4449
.... and by the way. You don't want to use tin snips to cut any aluminum -- the edge gets twisted & warped all sorts of ways. There's a good manual tool for small jobs -- see pics & links in lewster's post here. I've used it quite a bit and it works well if you're patient (better ones available if you have air tools and $$). Also look at this thread. Lots of useful info all through both -- there's a link for Metal Supermarkets -- probably one of those near you. .025" might be a special order.
__________________ . BobStream
...You really don't know someone 'til you've had recess with them. ...Alex Ziton, age 8
Putting fibreglass (or any sealer) on only one side of a board, especially one exposed to wide variations in temperature and humidity, can do more harm than good. Moisture can be trapped or escape through only one side of the panel.
This can cause twisting or warping, even delamination of the plys.
Besides that, waterproofing the floor isn't addressing the problem.
I'm refurbishing a '63 Avion 24' and a '73 Sovereign, both have floor problems.
I'll be working from above and below on both units, though I'll take the shell off of neither.
Properly scabbed, your floor patch idea will work fine. I'm planning on using the same technique and hoping to engineer it so that the panel or "hatch" can be easily reopened if necessary.
Jeff
I may not be understanding the problem you are trying to fix. If you are just concerned about water having been under the floor and the insulation being wet between the floor and the frame members then it will dry out as you drive. If the leaking was a flood with water running out of the belly pan seams I would suggest the following.
If the side to side frame members are of a year that doesn't have hole then check the tightness of the belly pan to the frame. You will want air to move the length of the trailer. If the frame has holes you are all set.
Cut some nice holes in the belly pan as far back as you can in front of the last frame member. Like 5 one-inch holes. Engineer some way to blow warm air into the belly pan from the other end. A pvc pipe with T's at the hole connected to a shop vac in the rear to pull the air would help. The idea is to pump warm air through the space to dry it out. Leave it run for a week. If the leaks haven't been ongoing and the insulation repeatedly wet for long periods then you should be fine.
Now if these leaks were around for awhile like 5 years you need to beware of the adage..... don't look unless you are prepared to do the Monty. It's not an issue of are there problems, it's how bad is it and how much worse it will be when you start cutting out sections of floor. This could get out of controll really easy.
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