Steel plate in my nose.

[58BUBBLE]

Before I put the shell back on I have a couple questions. I have read in a lot of threads about a metal plate that is in the front of all models for structural strength. I don't remember pulling this off when I removed the shell. I do have a piece of thin steel that is very corroded and half gone that could have been it but can't remember where it came from. Did they install these plates in the small trailers also? Does anyone have a picture of how it should be mounted? What kind of metal should I replace it with, I know steel can cause big problems with aluminum. Also, I saw somewhere in a thread about support brackets in different spots along the U channel. Do I need to add some of these brackets when rebuilding. I think maybe they would go on either side of the door and various spots for more support. If anyone has any suggestions about these support brackets and placement please let me know.
Thanks,
Jake

[markdoane]

Jake,

I don't think the metal plate is a structural element per se, but more an anchor point to ensure the shell stays firmly attached to the frame. The original plate was 12 ga. (about 1/8" thick). I replaced it with a new steel plate, well painted with POR15. As you can see the original was pretty rusty.

You should stick with steel for the plate, and paint it with POR15. Use 3/8" grade 8 bolts to attach the plate to the frame crossmember.

The support brackets are located at the corners. Again, I think they are location reference points rather than structural members. I found them very useful for getting the shell put back in original location.

The brackets on either side of the door are pretty important, I would mark those carefully and put them back exactly where they were.

[58BUBBLE]

So from what I can tell it looks like yours is bolted to the crossmember on the top side and bent 90 degrees. Then, would the plywood go right over the top and butt up against it? Do you run the bolts through the plywood and crossmember, or just the crossmember?
As for the brackets, were the originals made of the same aluminum as the shell?

[markdoane]

Yes, the plywood sits on top of the angle, bolted through the crossmember, plate, plywood, and u-channel. I used hot zinc plated washers, and then sprayed it well with zinc rich paint. You can see the four bolts in the previous photo, I think they were 2" long.

The original corner and door brackets were steel.

Here's the new plate. It also has three electrical conduits stubbed in, that are for routing wires from the conduit runs in the bellypan. You can see I actually used a second piece of steel strap, on top of the plywood, in place of washers.

[58BUBBLE]

I know a lot more about insulation now than I did before but need to decide on which product I should use. I was all set to buy the 3.5" fiberglass insulation at HD and smash it between the frame and floor like the factory but now I'm having 2nd thoughts. I'm not looking forward too installing the elevator bolts with fiberglass insulation hanging in my face and the frame holes. It's not a "clean install like foam board insulation would be. I currently live in Utah so I would like to have a good insulation job and I know the fiberglass will be at least as good as it has for the last 48 years, but would foam board be better? Is it good to have the fiberglass smashed between the frame and floor? it seems like it might be good because it would act like a gasket? Or would this be bad? As far as the foam, can you just liquid nails it to the bottom of the plywood or would that be bad not having a space between the floor and insulation? Can I get the same R value out of the foam board? As you can tell even though I know more now I'm still just as confused... TIA

[markdoane]

Jake,

Those are all tough issues. I ended up using fiberglas batts, but I installed them after the floor was on. It was my thinking that smashing the fiberglass between the floor and the frame reduced it's effectiveness. I am using 3 1/2" batts to get as much R-value as I can. If you lay 3 1/2" batts over the frame, it will only fluff out to about 2" between the crossmembers.

I also didn't want the batts to be laying in contact with the bellypan. I think that would let any water in the belly be wicked up into the batts. So I used steel strapping to suspend the fiberglass above the bellyskin. See the picture below for an illustration.

In the corners, where the space between the bellyskin and the floor tapers down to 1" or less, I used the method you describe with foam board. I would recommend using foil backed polyisocyanurate board, it has higher R-value than white beadboard or blueboard. Here are the R-values per inch thickness:

Fiberglass batts R-value 3.2
expanded polystyrene (white styrofoam) R-value 3.8
extruded polystyrene (blueboard) R-value 4.8
polyisocyanurate board R-value 5.8
foil backed polyisocyanurate board R-value 7.0

I thought carefully about adhesive and foam board, but decided not to because I was worried about getting a good fit inside the frame. If you cut the board for a tight fit, I think that flexing of the frame will cause edge wear where the foam meets the metal frame. If you go that way, I would cut the boards 1/2" smaller than the opening, and fill the gaps with fiberglass insulation.

As for having a air gap between the foam and the floor, that is not necessary. The reflective foil bubble that Malcolm is using in his walls requires an air gap, but it operates on a different principle of blocking heat flow.

[58BUBBLE]

Thanks for all that info Don, you have brought up some very good points. It looks like your frame design is different than mine, unless you added those outriggers the metal strap is laying on yourself. I don't have outriggers mounted low on the frame like that to attach the metal straps. I am thinking I will probably go with the foil backed polyisocyanurate board R-value 7.0. Is there a particular thickness you would recommend? Do they carry this type at HD? Is it fully surrounded by foil or is it just on one side? I assume if this is the case I would install it with the foil side down and glue the bare side to the plywood. Is that correct? I agree with your point about the edges being worn by the flexing frame but I think the fiberglass around the edges is an excellent solution.

[58BUBBLE]

Actually let me clarify my frame structure, my outriggers run from top to bottom so there is no gap to run the batts through like it looks on yours.

[markdoane]

Actually, my outriggers are solid, like yours. The batts are separate and don't run through openings in the outrigger.

The metal angles that the straps are attached to are lightweight roofing angles, rivetted to the outriggers about 3/4" from the bottom. The straps are about 28 ga galvanized roof flashing cut into two inch strips.

What I would do with the foam sheets is get whatever thickness you can find at HD (1" or 1 1/2"?) and put in two or three layers glued together. That would give you an R value of 20, if you want to spend that much money. I think the isocyanate is a good choice as it won't disintegrate like the white bead styrofoam. The stuff I found was foiled on one side. I put in two layers of 3/4" in the corners. I removed the foil from the glued surfaces, I don't think it is a good idea to glue to foil. The foil peels off easily. Leave foil on the outside bottom.

Here's more detail on the hangers for the fiberglass batts.

[58BUBBLE]

Oh yeah, Now I can see what you did. Do you think there would be any problem with putting in a layer of foil backed and then a layer of blue board. The reason I ask is I already have 2 sheets of the blue board sitting at my office.

[markdoane]

The blueboard is ok, it just has a lower R-value. Blueboard is pretty flexible and I don't think it will fall apart like the white styrofoam. In fact, look at the price/R value ratio of blueboard vs polyisocyanate. If the blueboard is 30% cheaper, it might be a better choice.

[58BUBBLE]

Is the steel plate then riveted to the shell? I don't think there are currently any rivets where the plate would have been. Is it possible mine didn't have one.
About the brackets, were they just short pieces of bent aluminum or were they steel? Did they do any reinforcing at all? Also, I was thinking of replacing some of my U channel but can't find anyone that sells it. Any suggestions?

Originally Posted by markdoane

Jake,

I don't think the metal plate is a structural element per se, but more an anchor point to ensure the shell stays firmly attached to the frame. The original plate was 12 ga. (about 1/8" thick). I replaced it with a new steel plate, well painted with POR15. As you can see the original was pretty rusty.

You should stick with steel for the plate, and paint it with POR15. Use 3/8" grade 8 bolts to attach the plate to the frame crossmember.

The support brackets are located at the corners. Again, I think they are location reference points rather than structural members. I found them very useful for getting the shell put back in original location.

The brackets on either side of the door are pretty important, I would mark those carefully and put them back exactly where they were.

[markdoane]

The steel plate definitely had rivets in it, holding the shell to the frame. In the picture above, there are about 24 rivets, two rows of 12.

Is it possible there wasn't one? Yeah. I think later models have a reinforcing plate in the rear also. I put one in the back of mine, made out of a length of 2x2 aluminum.

The brackets were steel. See the picture below. I don't think there is too much to worry about when making a steel to aluminum connection as long as you electrically isolate the two pieces with paint or zinc paste, use hot dip galvanized hardware, and spray with LPS corrosion inhibitor.

For the U-channel, I ordered a sheet of 2024-T3 to replace a side sheet, and I had enough left over to have the U-channels made at a local sheet metal shop.

Good luck!

[58BUBBLE]

Don,
Thanks for the info once again.
-Jake