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malconium · 01-06-2005, 01:01 PM

PWDF4,

From your description I am not entirely clear which direction the new steel u-channel is running. Are you talking about adding new members from side to side in between the existing cross-members? Also it would be an interesting piece of information for other Polyboard prospective installations to know how much extra weight you are adding with the steel. Did you decide to run the Polyboard sheets lengthwise or from side to side? What type of fasteners have you decided to use for holding the Polyboard in place? How do you like the product overall? Any other details or even photos of your progress would be of interest to me and perhaps to anyone else considering Polyboard.

Thanks and happy Polyboarding,

Malcolm

PWDF4 · 01-11-2005, 01:23 PM

THE 'U' IS DOWN. I HAVE ADDED A CHANNEL DOWN THE CENTER OF THE TRAILER, FRONT TO BACK. I HAD TO WELD SOME ACROSS THE TRAILER ALSO. ESPECIALLY WHERE THE 4' WIDE PIECES BUTT TOGETHER. I FIRST PUT A 36" PIECE OF POLYBOARD ACROSS THE FRONT FROM SIDE TO SIDE. I CUT ALL PIECES DOWN THE CENTER TO MAKE THEM EASIER TO HANDLE AND TO MAKE THEM EASIER TO INSTALL. THEN I PUT A 4' PIECE THEN ANOTHER 4' PIECE THEN A REMAINDER OF 34" PIECE. AS FAR AS THE FASTENERS THAT I USED, I USED 1/4" SS CARRAGE BOLTS AROUND THE WALLS. THIS WAS USED WITH SS FINDER WASHERS AND NYLON SS LOCK NUTS. THE FASTNERS IS THE CENTERS WERE 1/4" X 1" TSH MS VERY FLAT HEADED BOLTS. THESE WERE USED WHERE THE METAL WAS THICKEST OR OVER 1/4" THICK. I HAD TO DRILL AND TAP FOR THESE. WHERE THE METAL WAS 1/8" THICK I USED 8X1-1/4 MTH S/D ZINK - HARD SCREWS WITH A DRILL POINT. I HAVE CONNECTIONS WITH A BOLT COMPANY AND THESE WERE RECCOMMENDED. I WOULD SEND YOU SOME OF THE PICTURES BUT THIS WEB SITE ISN'T VERY USER FRIENDLY. THERE IS A PLACE TO ADD THE SILLY ICONS BUT NO PICTURES. MY E-MAIL ADDRESS IS PWDF4@AOL.COM. IF YOU WILL SEND ME YOURS, I'LL BE GLAD TO SEND THEM TO YOU.

malconium · 04-23-2005, 12:43 PM

Leo,

Wouldn't the marine grade plywood cost in the same general range as the Polyboard? Why not consider using the Polyboard for the whole thing? You would want to add some stiffeners to the Polyboard but that would not be much different work wise than adding all the splices between the plywood and the Polyboard apron. The last time I checked the price of Polyboard was rising some. I think the 3/4" 4x8 sheets where into the low $80's per sheet.

Malcolm

Over59 · 04-23-2005, 02:25 PM

How are you going to attach the lap together? Glue? Screws?. I think you'll be better off with the 5/8 marine ply or A/C exterior all the way. Known vs experimental. I'm using 3/4 marine saturated with thin epoxy around the edges for the whole floor with the shell off. The last floor made it 45 years. That will be good enough for me.

You know of course that it often starts out as "just a patch". Then it's going to be "a shell on", and then.

Over59 · 04-25-2005, 05:56 AM

As I understand it you are lapping poly and ply together. Does the poly hold glue or screws?

C Johnson · 04-25-2005, 11:08 PM

I have my "C" channel out and there are no weeping holes in it. Just the holes for the elevator bolts, rivets, and #10 screws that hold it to the floor. The ends, however, are open.

malconium · 04-25-2005, 11:11 PM

While it is true that the Polyboard does not hold screws quite as well as plywood does they do still hold. Certainly long enough to let the glue on your splines set. The type of glue that I used seems to stick very well to the Polyboard and is also supposed to be excellent for wood. I used Elmers Polyurethane glue. A very similar product is called Gorilla Glue. Both are available at Home Depot. You need to wet the surfaces before you put them together as the glue activates with a little bit of moisture. It also expands to fill any voids and usually squeazes out of the joint some. It will stain your hands too if you get any on you. I think a well glued spline joint with about a 4" strip of wood or Polyboard as the spline should make a joint between the Polyboard and plywood that would be as strong as either of them.

It would be possible to install everything with the Polyboard using bolts instead of screws if you have the belly pan off by the way. The main place where I used screws was to connect the Polyboard to the splines where I am relying on the glue to do the real work. I did use decking screws in the u-channel down to the Polyboard too except at the ends of the outriggers. There I used self-taping/self-drilling screws down into the ends of the outriggers. In the original install there wern't any screws into the outriggers that I could find (which suprised me). I used larger screws than what were originally into the plywood too. Since the c-channel part of the u-channel slips over the edge of the floor (at least for those later models that have that type of channel) the screws are only holding the channel laterally

Regarding the Polyboard expansion issue I installed my Polyboard sheets from side to side. I also typically cut my sheets in half so I was basically installing 4' x 4' tiles. The specs for the Polyboard suggest that you leave a 1/4" gap on the ends between 8' sheets. That seemed to me to mean that 1/8" gaps should be about right for between 4' pieces. As a practical matter I think you are supposed to leave a little bit of a gap between plywood sheets too. A 10" piece of Polyboard would have a pretty small amount of expansion compared to an 8' piece at 1/4".

I did not see any intentional weep holes in the u-channel when I took my AS apart. I did decide to add some. I drilled 1/4" holes with at least one in each wall section. I added a piece of fiberglass screen over each hole that is held in place with a little vulkem around the edges.
The Polyboard glued to the plywood should be strong enough laterally in my opnion. Also while every part of the AS does add some to the strength it is also my opinion that making sure to fasten the u-channel to the ends of the outriggers should go a long way toward resisting any outward movement of the body even without any contribution from the sub-floor.

I do wonder it there could be problems using 9" tiles over Polyboard because of the expansion. Maybe the tiles would actually have a similar rate of expansion though. I believe I read somewhere here in the forums that the original tiles were installed so that the joints in the plywood fell at the same places as the joints in the tiles.

Malcolm

Torii · 04-27-2005, 08:31 AM

Malcolm,

Thanks for the great info on your project! I have a few soft spots in my 75' Tradewind. In the fall I will have a look and see what kind of damage I am dealing with. If needed, a new floor will be my winter project. You mentioned several times in this thread that "The floor looks fine and seems plenty stiff enough to me". You have the distinct advantage of having done your floor in the same unit using plywood, how would you say the polyboard campares to plywood in terms of strength and stiffness. (which one is stiffer) I am 6'4 and weigh about 220. If I do replace my floor I would like to have one that does not flex under my weight if possible.

malconium · 04-27-2005, 12:46 PM

Quote:

Originally Posted by T Man

Malcolm,

Thanks for the great info on your project! I have a few soft spots in my 75' Tradewind. In the fall I will have a look and see what kind of damage I am dealing with. If needed, a new floor will be my winter project. You mentioned several times in this thread that "The floor looks fine and seems plenty stiff enough to me". You have the distinct advantage of having done your floor in the same unit using plywood, how would you say the polyboard campares to plywood in terms of strength and stiffness. (which one is stiffer) I am 6'4 and weigh about 220. If I do replace my floor I would like to have one that does not flex under my weight if possible.

The plywood was definitely nice and stiff without having to add anything additional to stiffen it. The Polyboard does need something like what I did with the aluminum channel. I am 6'2 and weigh in at 230 lbs. I think the Polyboard as I have installed it is plenty stiff enough for me at my weight. I have been working back and forth in the AS installing insulation and various other things ever since having installed the Polyboard and I do not feel that there is any kind of a strength problem. I have had my portable air compressor running on the floor without problems too. The Polyboard seems to be pretty tough stuff. It just is not quite as stiff as plywood and needs the extra help. I am still very pleased with the results.

Malcolm

malconium · 04-28-2005, 11:38 AM

I went out to the AS yesterday just to make sure what I was saying about the Polyboard stiffness was correct. I can detect some small amount of visible deflection of the floor when I stand in between the major cross members. I do not detect it at all when I walk around though. My aluminum bracing is probably not as stiff as if someone were to use some steel. I still am fine with the small amount of deflection but it could cause a problem if someone wanted to glue down 9" tiles. Both the small amount of deflection and the possible expansion/contraction could very well cause problems with flooring of that type. I am intending to use some sort of floating floor so do not feel this will be a problem for me at all. I guess the bottom line is that plywood does provide the best stiffness if that is an issue such as for flooring type. I still very much like the Polyboard for the fact that it is entirely waterproof.

Malcolm

Torii · 04-28-2005, 12:07 PM

I agree that the fact that it is waterproof is a HUGE plus for the polyboard. If I end up ever replacing the floor in my Tradewind I will probably use it because sooner or later new leaks will develop and it would be nice to know that when they do that my floor will not be rotting as a result. I wonder if welding steel supports to the frame in about the same location and frequencies as Malcolm's aluminum bracing would result in a stiffer Polyboard floor? Of course that means even more weight added.

PWDF4 - I think you mentioned adding steel supports... How did that work out? Any flex in your floor? How much weight did you add to your trailer?

C Johnson · 04-29-2005, 12:07 AM

I think adding extra steel would significantly increase your weight. If you plan to upgrade your axles tho, it may be ok. Just my 2 cents.

ankornuta · 01-09-2006, 09:20 PM

Quote:

Originally Posted by malconium

I have already replaced the floor once but made the mistake of using the new variety of treated plywood before I found out that it is way too corrosive to aluminum and steel.

Malcom, I know you posted this a long time ago, but this statement confuses me. Did you use the ACX 5/8" plywood that so many people use for floor replacements? What's this corrosion you found out about?

malconium · 01-12-2006, 06:32 PM

Quote:

Originally Posted by ankornuta

Malcom, I know you posted this a long time ago, but this statement confuses me. Did you use the ACX 5/8" plywood that so many people use for floor replacements? What's this corrosion you found out about?

The first time I replaced my floor I used chemically treated 3/4" plywood. My unit uses 3/4" but I guess some models used 5/8". The problem with this solution was that the chemicals used to treat the plywood is way too corrosive to metal and especially aluminum. I could already see signs of problems when I pulled out the treated plywood to replace it with the Polyboard. Normal non-treated plywood does not have this problem (including ACX grade) only the chemically treated varieties.

Malcolm

ankornuta · 01-14-2006, 07:40 AM

Oh... good, I'm glad to hear that ACX won't do that! I was thinking that you were referring to ACX having this issue. I plan to start laying down my new ACX plywood floor next weekend after finishing the body lift this weekend. I've been shocked by the speed of my progress

(that's the good kind of shock, of course).

guy99 · 01-14-2006, 07:48 AM

Has anyone used MBO (Medium density overlay) for flooring. It is the material used for outdoor signs and is reported to be very water tolerant.

guy99 · 01-14-2006, 04:17 PM

To clarify, MBO is a plywood product with waterproof glue and with a resin impregnated 'paper' adhered to one side (or both).

markdoane · 01-14-2006, 07:47 PM

Guy,

I didn't use mdo. I think the advantage would be that mdo is edge sealed, which is something everyone does anyway with penetrating epoxy, and the one smooth side.

Otherwise, it is just B-C exterior grade plywood.

guy99 · 01-14-2006, 09:39 PM

The entire surface, or both surfaces, are water proof (resistant?) because of the layer of resin/adhesive used to bond the 'paper' to the surface of the plywood.

Also, the mdo I have used for other projects had no voids. I don't think B-C grade plywood is without voids. Flooring underlayment is though.