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Old 06-13-2004, 01:02 PM   #43
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You can add as many outriggers as you feel necessary.

Actually, the more the better.

For additional rear end hold down, we install a section of 2 x 2 x 1/4 angle, immediately outward of the frame, and rearward as much as possible, so that when you put the banana wrap back in place, it will hide that area.

Entire 4 x 8 sheets of flooring should be replaced whenever possible.

Sectioning one such as in the above photo's will permit the trailer to flex to a much greater degree, as all those seams will in themselves flex.

I would forecast severe problems with that type repair, in time.

Again, if the job is worth the undertaking, it should be done at least as well as Airstream did it. Anything short of that, "is not" proper repairs, and you can guarantee yourself that more problems will surface as the flexing takes place.

Then it will be back to the drawing boards, or dump the coach on some unexpecting buyer.

Not trying to be critical of anyone's repairs, but facts are facts.

I have doing this for over 38 years. I too, can tell you many many horror stories of improper repairs, that resulted in huge financial investments, to not only repair the additional damage caused by the improper repairs, but then also correct the improper repairs as well.

A floor that has had major splices, will result in shell damage, because of the additional flexing, especially when the floor patch jobs are at the front of the trailer.

A small amount of flexing is what an Airstream is designed to do. When that is exceeded, you will bite the bullet.

Andy
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Old 06-13-2004, 02:42 PM   #44
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Andy - thanks - very interesting. One more quick question, what do you think of laying sheets lengthwise with a good joint down the middle? I know this is different that what Airstream did originally - they lay the sheets crosswise. There have be two joint methods discussed - welding a steel stringer down the center and using about a 1x6 glued and screwed down the center. Seems either to me would be pretty strong.

Its makes sense to me to have as few joints as possible.

Ken
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Old 06-13-2004, 03:13 PM   #45
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Ken.

I would think that the long method would allow too much twisting from side to side.

Also your weakest area would be at the front, which is where you want it to be stongest.

Andy
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Old 06-13-2004, 04:20 PM   #46
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I'm trying to develop a 'free body diagram' (non-engineers can skip the rest of this post), and I don't understand what forces cause side-to-side twisting that wouldn't be damped by the axle. I think (for plywood floors only, not OSB) that the benefit of much higher bending resistance in the long dimension would make a lengthwise arrangement stiffer and less likely to result in separation.

And I don't understand why the weakest area would be in the front?

Help!
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Old 06-13-2004, 08:23 PM   #47
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Hmmmmmmm again, seems to me unless you do a shell off, it would be pretty tough to put the plywood crosswise. Sooo seems to me that instead of a 6 in wide strip down the middle, I think a 2-3 foot strip (what ever can be fitted between the frame glued and screwed would be the way to go. This would make it very stiff. If there is concern for twisting, then a metal stringer down the middle would not work at all.

Again, thinking out loud, I could see that since the distance is not that great side to side, the center would have a tendency to push up from the weight of the sides???? Whereas, since the distance from front to back is a lot, then the cross mounted plywood does make sense......... Very interesting stuff.

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Old 06-13-2004, 10:48 PM   #48
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Again, thinking out loud, I could see that since the distance is not that great side to side, the center would have a tendency to push up from the weight of the sides???? Whereas, since the distance from front to back is a lot, then the cross mounted plywood does make sense......... Very interesting stuff.

Ken J.
Ken,

I think any trailer is pretty stiff in the lateral, side-to-side direction, compared to the longitudinal direction, front-to-back.
Laterally, there are 10 to 16 steel crossmembers and a pretty stiff axle to resist any sideways bending. As you mentioned, the loads are located at the edges, but the edges are only about 20 inches from the main frame rails and are supported by outriggers.

On the other hand, in the longitudinal direction, there are only the two frame rails to resist bending, and the loads are concentrated at the axle attachment points. Except for a 'three axle Bambi', the loads are hung out from 8 to 12 feet from the axle.

So I think it advisable to put the plywood with it's stiffest dimension fore and aft, where it will add to the stiffness of the frame. Any method of joining the two sheets in the middle should work as long as it is equal to the shear strength of plywood. I think I would prefer the metal center strip with elevator bolts. Thats the type of joint that has been used for the side-to-side joints since the 50's with lots of success.

I still don't see where side-to-side twisting is a big issue. Unless a trailer were loaded with most of the weight in opposite corners, I don't see how it happens?
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Old 06-13-2004, 11:14 PM   #49
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All - I've been thinking about this floor replacement thing and trying to understand the pros and cons of replacing a larger section of plywood.....which I'm NOT gonna do.

It seems that replacing the whole rear section would actually be worse, not to mention more intrusive on the trailer. I would effectively have the back section of plywood disconnected from all of the other plywood. It seems I would want to keep the strength of that solid sheet, that right now runs all the way to the back of the trailer and only replace what is needed. Right now most of my trailer is one solid piece of OSB - why would I cut more out of it? Seems like having a split in the flooring 4 feet from the back of the trailer, all the way across, would cause more flexing than what I'm doing now.

Assuming an individual replaces the rotted sections by cutting back to the frame sections, splitting the support distance in half between old and new wood, screwing old and new wood down to frame with self tapping screws, insuring new flooring is inserted properly under "U" channel, with additional carriage bolts in the channel (Thanks Andy!)....... the repair should be sound.

Am I missing something? I don't see the benefit in cutting out more wood.

Joe
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Old 06-13-2004, 11:41 PM   #50
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When I was taking the old floor out of my A/S I ran across an old repair that was evidently done by someone that knew what they were doing. It was in front of the door, when the patch was made they routed the remaining floor back about 8" and did the same to the piece they were installing, making in effect an 8" half lap joint, there were no screws used, just glue. I had to literally tear the plywood into pieces to remove it. So I believe you can make a patch at least as strong as the original.
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Old 06-13-2004, 11:53 PM   #51
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Ken,

I think any trailer is pretty stiff in the lateral, side-to-side direction, compared to the longitudinal direction, front-to-back.
Laterally, there are 10 to 16 steel crossmembers and a pretty stiff axle to resist any sideways bending. As you mentioned, the loads are located at the edges, but the edges are only about 20 inches from the main frame rails and are supported by outriggers.

On the other hand, in the longitudinal direction, there are only the two frame rails to resist bending, and the loads are concentrated at the axle attachment points. Except for a 'three axle Bambi', the loads are hung out from 8 to 12 feet from the axle.

So I think it advisable to put the plywood with it's stiffest dimension fore and aft, where it will add to the stiffness of the frame. Any method of joining the two sheets in the middle should work as long as it is equal to the shear strength of plywood. I think I would prefer the metal center strip with elevator bolts. Thats the type of joint that has been used for the side-to-side joints since the 50's with lots of success.

I still don't see where side-to-side twisting is a big issue. Unless a trailer were loaded with most of the weight in opposite corners, I don't see how it happens?
Don
Since I have already laid my floor lengthwise I guess I would jave to agree with you. The only thing I would add is my outriggers are 15" long not 20", shorter distance = greater strength.
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Old 06-13-2004, 11:58 PM   #52
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When I welded my center strip in I welded it top and bottom, when A/S welded the crossmembers in they only welded the bottom side. I assume it was to keep the floor area level and not have any protrusions into the floor. I think it will hold at least as long as the original welds on the crossmembers.
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Old 06-14-2004, 12:10 AM   #53
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Ken.

I would think that the long method would allow too much twisting from side to side.

Also your weakest area would be at the front, which is where you want it to be stongest.

Andy
Andy
When I laid my floor I started at the back laying side by side lengthwise towards the front. I laid six sheets lengthwise bolting to the strip I welded in the center using it as a bolt guide to make sure I remained square to the frame. The last sheet in the front I laid crosswise, as the narrowing of the frame in the front was a concern. See link for picture of front of floor.
http://www.airstreamphotos.com/photo...sort/1/cat/500
I wanted as much strength as possible. Also I wanted to thank you for the advice on the bolts, after reading your post on increasing the amount of bolts I went back and looked at my installation and doubled the amount of bolts. Thanks.
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Old 06-14-2004, 01:16 PM   #54
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Just a couple of middle of the night thoughts....

As I think about it, I can't imagine the plywood adding any stiffness to the trailer. Its pretty flexable - what gives the trailer its stiffness is the monqoque (sp) design. I was surprised how flexible my frame is. As I got to thinking about what I said above about the center tending to lift, I think Don is correct about the cross members - cannot imagine that plywood would add any stiffness to the already still cross members - I also got to thinking about what Andy said about outriggers - the outriggers is whats taking the weight of the shell - therefore the more the better. Was talking to a friend of mine and he was saying the plywood only adds stiffness over about a 16in span - he said you have to be careful with plywood not to span it too much - soo the distance between frame and outrigger is whats important - about 16-20 in or so.

Anyway, just some idol thoughts.......don't know if they make sense, but the I find this discussion very interesting.

I would not however, use self tapping screws - I like bolts better and any joints I would use a 1x6 or so plywood thats screwed and glued.
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Old 06-14-2004, 01:43 PM   #55
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Joe,

Well, I'm glad that N. Dallas RV is refunding your money. I really like those guys and am still surprised that they let your trailer go out the door that way. You are still out mileage/hotel/time though. Looks like you have things well under control though!

Tripp
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Old 06-14-2004, 01:59 PM   #56
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Just a couple of middle of the night thoughts....

. . . - what gives the trailer its stiffness is the monqoque (sp) design.
Very true. But that assumes the shell is well attached to the frame. It's when the front and back connections are poorly made, or fail due to wood rot, that the frame starts to move up and down without the body.

Just out of curiosity, I'm going to measure delection of the frame before and after the floor is mounted, to see if there is any measurable difference.
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