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Old 02-23-2013, 10:41 AM   #1
2 Rivet Member
1967 17' Caravel
georgetown , Texas
Join Date: Apr 2012
Posts: 27
Caravel subfloor replacement self tapping screw question


Im doing a shell on complete gutted redo on my 67 caravel. I am replacing the whole subfloor in sections with plywood, coated with Thompsons water seal and 3m rubberized undercoating on the sides.

My question is in regards to bolting and screwing the subfloor down. In the back, I am getting rid of the bathroom in lieu of a queen size bed. In the rear section, we did not cut and replace the elevator bolts, just shimmed the plywood under the c channel.

Is this ok? Or did we screw up. Do we really need to cut off the elevator bolts and bolt the floor in? I was thinking about just using some self tapping screws and screw them thru the c channel at an angle into the new subfloor and not mess with the old elevator bolts.

Another question, can i just use self tapping screws all along the subfloor into the frame? If any one has done this, any suggestion on what product to use?

Many thanks!!!!!!!!!

ps. The wiring to the trailer lights, (7 pin thingy) is in bad shape. I was thinking it would be a good idea to run new wire thru the frame for the lights. Any suggestion on product?
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Old 02-23-2013, 11:49 AM   #2
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1961 24' Tradewind
1969 29' Ambassador
1970 21' Globetrotter
Jamestown , Tennessee
Join Date: Jul 2008
Posts: 1,783
I have done several shell on floor repairs. The body is attached to the floor with sheet metal screws and bolts thru frame outriggers. To access these it is necessary to open up the lower walls. If there has been any moisture in there most of the hardware will be in bad shape and should be replaced.

Regarding bolting the floor to the frame you can cut off all the old elevator bolts and use self threading trailer floor screws. These are usually 1/4 by about 2.5 inches and are made of very hard steel.
They can be found at places like tractor supply in small quantities or on E bay or other sources in bigger quantities.. These usually require drilling a 7/64 pilot hole and then are driven in with an electric drill. They are designed for the job and work well.

Around the edges I used 1/4 inch lag bolts and for the frame attachments used carriage bolts inserted from below by making a 3/4 inch hole in the belly pan where it was too close to the floor to get the bolts in underneath.

The floor was pieced in with pieces of wood screwed and glued underneath the joints.
It was not necessary to drop the belly pan this way and has stood up well.
In fact it is probably better done than the factory job which started coming apart in only 50 years
Rick Davis 1602 K8DOC
61 tradewind, plus a few others
13 Ram 2500 TD
99 Dodge TD 577K miles

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Old 02-23-2013, 01:03 PM   #3
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1968 17' Caravel
Battle Ground , Washington
Join Date: Dec 2002
Posts: 12,155
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I used the big self-tapping screws Rick describes above to piece in my half-floor replacement. I did mine shell on, bellypan on, so there was no access from underneath. That was several rears ago and it has held up just fine.

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Old 02-23-2013, 01:58 PM   #4
3 Rivet Member
1965 17' Caravel
Birmingham , Alabama
Join Date: Apr 2007
Posts: 180
Slightly different opinion here. You really don't want to cut corners on the floor replacement if you don't have to. If you are replacing the entire floor, I recommend you consider using elevator bolts where the old ones were. I used a few self tapping screws on the last floor section near the door because I couldn't reach under. The reason for the elevator bolts is the floor holds the whole shell to the trailers frame. Washboard-rough interstates, potholes, general flexing and vibration really put stress on the floor system. It's so much work to do this floor project, the last thing you want to do is fix it later if it loosens up. Also, loose floor fasteners can back out and spoil your flooring. Don't be afraid to take the back belly pan sheet loose and lay it down on the ground. Similarly, don't be afraid to cut a few 6 inch square holes in the belly pan for bolt access. You just rivet on a square patch sealed Around the edges with Vulkem. It's worth the trouble and you will probably be glad to be able to pull new 7 point connector wire through the frame. And yes, the lower inside walls need to come out. It's not hard to do, just take your time.

Please don't use any drywall screws on the floor, they will rust or snap easily. Use zinc plated. Remember the factory would have cut corners on the bolting if they thought they could have gotten away with it.

Have fun and good luck with your project!

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Old 02-23-2013, 05:05 PM   #5
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1961 24' Tradewind
1969 29' Ambassador
1970 21' Globetrotter
Jamestown , Tennessee
Join Date: Jul 2008
Posts: 1,783
Just for the perspective, the older trailers had elevator bolts installed and then hit with a hammer so they couldn't loosen. Back in those days I doubt there were any harden self threading (fine thread) bolts available. This is based on the body being screwed to the floor with slotted #12 sheet metal screws which indicates that they did not have power screwdrivers either although they may have had the old kind you pushed up and down on.
The trailer floor bolts I used were tight enough that the head could be pulled right through the plywood if you drove it hard enough. I have never seen one loosen even after thousands of miles. I have had no trouble with drywall screws either although possibly galvanized deck screws would be better.
I only used the drywall screws where I scabbed support boards under the new joints. Glue was also used.

Another one of those jobs that can be approached multiple ways
At any rate, no problems with any of these thus far
Dropping the belly pan on some of the older trailers, like my 61 is a serious job as it is riveted at the outside edges. On a newer trailers where the seams are underneath it would be much easier .
Rick Davis 1602 K8DOC
61 tradewind, plus a few others
13 Ram 2500 TD
99 Dodge TD 577K miles

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