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Old 04-06-2021, 11:30 AM   #1
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1954 22' Safari
Bellefonte , Pennsylvania
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Shell On Floor Replacement - Fasteners?

My 55 Safari will be getting all new flooring with the shell and belly pan on.
Although shell off is a more complete renovation, I just don't have the work space or equipment to do a shell off job.

My questions are:

Is there any way to install elevator bolts to secure the plywood flooring with the shell and belly pan on?

What are the recommendations for using self tapping SS screws to secure the flooring to the frame?

Thanks for all suggestions and insights.
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Old 04-06-2021, 12:16 PM   #2
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I have done 2 full and 3 partial floor replacements, all with the shell on or as I like to say "floating". All have been with belly pan removed (either full or partial) and insulation out. In '76 Argosy I did drive some of the old self tapping screws back in, but combined that with elevator and regular bolts. The oldest trailer I've done was a '61 Ambassador, had a 4" true "c" channel frame, not folded or boxed steel. No screws in the frame rails, all in the crossmembers and out riggers. Not sure I'd use SS, can be quite brittle. Not a lot to bite into in that maybe 14 ga. metal. The full floors I did, the trailer was on 6 ton jack stands so 20-24" off the floor. Axles were out, belly pan and insulation removed as needed. You may be able to work around that creatively. Certainly would like bolts going through "c" channel through floor and the end of the outriggers. I could tell you more about the '61 if you'd like.
Good luck, Mark D
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Old 04-06-2021, 01:11 PM   #3
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Yes, you can use elevator bolts with a shell-on. I did it quite successfully with my Bambi II. You just need to cut out the center (at least) part of your bellypan to gain access to the underside and have another person to help set/tighten the nuts and bolts.

Then you can button everything back up, and except for that slightly off person who wants to see your perfect bellypan, no one will ever be the wiser.

The C channel crossmembers and outriggers are not thick enough, in my opinion, to give enough hold with self-tapping screws. A few here and there, perhaps in a hard to reach spot would be OK, but I would not rely on them solely.
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Old 04-06-2021, 01:23 PM   #4
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Plenty of people have done shell-on floor replacements (though in my mind, doing a floor replacement with the shell on is the hard way to do it). Very few have tried to do it without removing the bellypan, and trying to do it without removing the bellypan is one of those "shortcuts" that ends up a long-cut in the end.

Anyway, the floors were held down to the crossmembers, in the 70's with self-tapping screws without any nut on the bottom, but the bolts securing the C-channel to the outriggers always have/need nuts.

There are a few threads on these forums investigating possible expansion bolts and other technologies that might allow someone to anchor the shell without removing the belly pan. I would bet that the time spent researching the various options for fasteners exceeded what it would have taken to just drop the belly pan.

Good luck!
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Old 04-06-2021, 01:45 PM   #5
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1954 22' Safari
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Quote:
Originally Posted by Belegedhel View Post

I would bet that the time spent researching the various options for fasteners exceeded what it would have taken to just drop the belly pan.

Good luck!
I think I am hearing "Drop the Pan already!"
I guess short cuts are the long way round.
Dropping the pan will make other things easier such as applying a POR 15 coat to the frame...and the floor replacement.

I bought some C1022 steel self drilling screws with a "Spex" finish to screw down the floor to the frame. These screws are rated to secure 3/4" plywood to steel up to 0.175" thick so should be up to my project's needs. I also have steel elevator bolts to use where needed.

The treated 3/4 inch plywood I will be using will be further treated with a penetrating epoxy sealant.
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Old 04-06-2021, 02:02 PM   #6
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Careful using a treated plywood as the subfloor. Some of that stuff has some very toxic chemicals in it that can not only outgas into your living space, but also react with the aluminum and steel fasteners and accelerate deterioration.

And yes, you will find that the most corroded areas of your steel frame will be where it is in contact with the bellypan, partially because moisture gets trapped there, and partially because of the anode-cathode reaction. This is one of those times where you should say "as long as I'm here..."

good luck!
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Old 04-06-2021, 02:17 PM   #7
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I am just going to say to not use treated plywood for the sub floor because of the corrosion problems. Treated wood corrodes both steel and aluminum. I was in the forest products industries a long time. I expect the newer treatments are as corrosive, or more so, than the old ones I am used to. Use regular exterior plywood. Coat the edges. Keep it dry. Or...look at the new composite material that Airstream is using.

Do you have the interior panels out? You need access to the top of the elevator bolts also. You either replace the elevator bolts or you depend upon the old elevator bolts to hold the shell to the frame. How rusty are the existing elevator bolts? The elevator bolts have nothing to do with holding the floor and everything to do with holding the frame and the shell together. If part of the elevator bolt shaft where it goes through the C channel is rusted away then it needs replacing. The subfloor does need to go into the C channel as a spacer between the frame and the shell. For small patches I have used an elephants ear notch around the existing elevator bolt and drive the wood into the channel. I had to thin the 3/4 inch plywood at the edges to get it to the 5/8 that seemed to be the c channel width.
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Old 04-06-2021, 02:42 PM   #8
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Originally Posted by Bill M. View Post
I am just going to say to not use treated plywood for the sub floor because of the corrosion problems. Treated wood corrodes both steel and aluminum. I was in the forest products industries a long time. I expect the newer treatments are as corrosive, or more so, than the old ones I am used to. Use regular exterior plywood. Coat the edges. Keep it dry. Or...look at the new composite material that Airstream is using.

Do you have the interior panels out? You need access to the top of the elevator bolts also. You either replace the elevator bolts or you depend upon the old elevator bolts to hold the shell to the frame. How rusty are the existing elevator bolts? The elevator bolts have nothing to do with holding the floor and everything to do with holding the frame and the shell together. If part of the elevator bolt shaft where it goes through the C channel is rusted away then it needs replacing. The subfloor does need to go into the C channel as a spacer between the frame and the shell. For small patches I have used an elephants ear notch around the existing elevator bolt and drive the wood into the channel. I had to thin the 3/4 inch plywood at the edges to get it to the 5/8 that seemed to be the c channel width.
I misspoke, I have exterior plywood - not treated.
I think the real difference in exterior plywood is the glue that holds the plies together. I will be using epoxy to waterproof the flooring around the edges where the rot usually occurs.

I am pulling the entire floor out. It seemed fairly solid when I bought the old Safari but when I dug in a bit I found patches and a lot of rot around the c-channel.
I am pulling the floor out in stages, not all at once, starting at the front.
I had sort of suspected I may need to thin the edges of the plywood a little to fit into the c channel. Did you use a router to cut a ply away?

Yes the interior panels are out and some but not all the bolts are corroded.
I will be removing all the bolts to install new ones.

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Old 04-06-2021, 03:24 PM   #9
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Yes. I used a router to thin the edges. Also thinned some with a hand plane. Looks and sounds like you have the job well in hand. That is more than I have ever done.
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Old 04-07-2021, 07:45 AM   #10
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Belly Pan removal for floor replacement...

The belly pan in my 55 Safari is of course held on by rivets.

Front belly pan rivets

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Rear belly pan rivets

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It looks like the front and rear belly pan sections are mounted under a trim piece. The side portions of the belly pan are attached with rivets.
I now plan to remove the belly pan while doing the floor replacement.

What size and type rivets will I need to reattach the belly pan?
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Old 04-07-2021, 09:14 AM   #11
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We went with 5/32 pop rivets to replace the 1/8 along the sides and 5/32 large flange rivets underneath into the crossmembers.
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Old 04-07-2021, 09:30 AM   #12
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You might want to use closed end pop rivets to put the belly pan back on, and any exterior trim pieces you remove, along with a dab of sealant (we used Trempro). Helps keep everything nice and watertight.
We found that those elevator bolts were easiest to tighten with 2 people. And the higher you get the trailer in the air, the easier it is on the person underneath. We were up on blocks at the time.



Kay
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Old 05-02-2021, 05:35 PM   #13
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I am getting closer to installing the first replacement floor section on my '55 Safari.
Here are some of my mistakes...
-I bought the wrong plywood - treated with chromated copper arsenate (CCA) which is corrosive to aluminum. Also this CCA plywood is 3/4 inch (actual 0.703") thickness, too thick to fit in the space between the shell channel and the frame.
Wrong type plywood

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-I started removal of the entire belly pan but soon gave up on that idea. This is a shell on replacement and I did have one section of belly pan that needed replaced. I soon discovered that removal of the entire belly pan was not an easy process and not worth all the extra work.

Damaged belly pan
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Section belly pan removed
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One thing I am doing right is treating the frame for corrosion protection. Very happy with the result.
Treated frame
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Here is the old flooring section, edge rotted out.
Old flooring
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I used cardboard as a template for the front floor section. My mistake here? I missed an old screw making me think, Why won't this darn thing fit???
Cardboard template
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I have ordered new plywood for subfloor. 19/32-in x 4-ft x 8-ft Pine Sanded Plywood, Untreated with an actual thickness of 0.594", close enough to the 0.625" thickness of the original 5/8" floor.
I plan to seal the edges with penetrating epoxy. I am also thinking of sealing the entire subfloor, top, sides, and bottom with epoxy.
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Old 05-02-2021, 06:00 PM   #14
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This is an I think it would work idea rather than something I have done. The elevator bolts hold the skin to the frame. They really have nothing to do with the floor other than they go through the edges of it where it is wedged in the channel. One could take the floor out. Then replace the elevator bolts while the floor is out, working from the top. Then elephant ear the new floor around the new elevator bolts. This requires putting the new floor in in pieces rather than whole sheets.
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Old 05-02-2021, 07:09 PM   #15
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We replaced our floor in our '56 Safari with the shell on or "floating" as someone called it. We dropped the belly pan a section at a time because the belly/side panels/c-channel at the floor are all tied together with the same rivets - if the whole belly was dropped at the same time, there would be nothing holding the side panels & c-channel up.

You can see how we did it in my "It's a Girl!!!" thread starting around post #109.

Good luck - it is do-able! While doing a body-off floor replacement is probably "easier" sometimes circumstances prevent folks like us from doing so. Ironically, now that our trailer restoration is completed, we have the space that a shell-off would be more feasible - but at the time, we lived in a house with a very small city lot. It worked for us...

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Old 08-30-2021, 01:19 PM   #16
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Finally have the front and rear flooring sections installed in my '55 Safari.
Fitting the curved sections was not easy.

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The rest of the floor should be a breeze

I will be installing the rest of the flooring in sections that run the length of the trailer. Basically two 8' x 4' sections and two 8' x 3'2" sections lapped together with cut outs for the wheel wells...more to follow.
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