Cabinet Moving, Rivets Popping! - Fiberglass RV


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Old 06-19-2010, 09:17 AM   #1
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I just posted this on the Casita forum, but I've had great interactions on FGRV, so I thought maybe I'll try here too. We have a 16' SD. It seems to be a common problem for the front rivet above the microwave cabinet to break, apparenty because the cabinet top is trying to move inward. The other rivets are bent, with the acorn nuts sitting at an angle. I did a temporary repair of the first rivet using a brass 10-32 bolt after drilling through from the original hole outside, resulting in a new hole in the cabinet top flange. I didn't realise it had moved quite that far. Last night, I discovered the aft-most rivet sheared. So I'm thinking maybe I'll drill out all four rivets along the top and try to push the cabinet top outward again before re-riveting all at once. Otherwise, I'm going to have to redrill to get straight holes again. Has anyone else encountered this? Our Casita is five years old, so maybe this is some kind of settling-in process? Or maybe pulling it home after buying it last fall with a horribly deformed tire (Marathons now replaced) on that side that shook things up enough to cause the shifting?

Is this a common problem? Any other ideas on how to remedy the situation?

Parker
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Old 06-19-2010, 04:24 PM   #2
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What you're describing sounds like shear forces on the rivet. I wouldn't re-drill, but it would make sense to install a fastener system that distributes the stress and still allows movement.

You might try putting a fender washer on the inside and outside to distribute the stress -- put butyl tape under the washer and between the washer and screw head on the outside and trim and bend the inside washer to fit with your cabinet on the inside-- and use a stainless steel screw with a fender-washer-spring-washer-nut-capnut arrangement on the inside.

The spring should be a sturdy type that has a diameter smaller than the smaller, standard-size washer you place under the nut and which you can not easily compress between your finger and thumb, the nut that holds everything together should be fastened to the point where there's just a little bit of give between the coils of the spring, and the stainless steel screw should be cut 3/16" above the nut, then capped with the cap nut tight against the other nut so neither can move. I'd probably paint all my hardware white (or whatever color your cabinets are) before installing them.
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Old 06-19-2010, 04:36 PM   #3
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Using a different fastener system is a good idea. Basically, what you want to avoid is any flexing of the two parts independently of each other. It's kind of like torquing a fastener --- leaving it looser and vulnerable to a small amount of "wiggle" is much harder on it than not.

Another good (and hole-less) way to take care of it would be to use fiberglass tabbing between the inside fiberglass of the cabinet and the inside fiberglass of the camper shell.

Both of these methods assume there is nothing "special" wrong with your camper (for example, you took out interior support and the whole shell is flexing more than anyone can guess at). I doubt this latter is true, but felt I should mention it.

Basically - unitized rigidity is your friend; small amount of mating surface area and flexing of attachment method is your enemy.

There is nothing wrong with a good rivet attachment, but on the other hand, since you are not in a production setting, and don't have those limitations, you can also do better.

Raya
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Old 06-19-2010, 05:06 PM   #4
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Learn from aircraft assembly. Take nails or something with a head that won't fall through the hole and that is the same diameter as the hole and align all the holes with them. Then remove the nail alignment pins one by one and replace with your fastener, rivet, bolt or whatever. Do this not in order, in other words jump around so that the parts to be fastened don't develope wrinkles, like tightening lug nuts on a wheel.

Aircraft manufacturers use a system called "Cleco" http://www.skinpins.com/fastclecotemp.html

At any rate, it is a good assembly practice to place all the fasteners before starting to tighten.

Have fun!
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Old 06-19-2010, 06:34 PM   #5
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Actually, on something that can flex a bit (like a fiberglass cabinet), wouldn't you start fastening at either one end, or in the middle and work in linear fashion? I understand torquing a head or a wheel, say, in a star pattern, because you do not want to warp it or have some weird imbalance. And the item to be torqued is fairly "solid."

But if something is flexible (such as fiberglass, or, say, a long wooden toerail on a boat), I would typically either start in the middle and work my way to each end, or start at one end and work my way to the other end (depending on the situation). So I did not end up with a "bulge" or "wrinkle" in the middle.

Raya
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Old 06-19-2010, 09:01 PM   #6
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I appreciate all the discussion here. Of all that I read, the "Cleco" idea is probably the most workable. As Peter pointed out, the rivets are in shear, because the top of the cabinet is riveted to the curved roof-line and wants to move inward. I'm reluctant to try some floating fastener arrangement, however. I think the result would probably be motion to the allowable travel of such fasteners, and then the problem begins anew. Raya, tabbing in with glass might be good if the trailer were gutted, but I'm working with a cabinet riveted through the Casita's carpeted walls and ceiling.

I think I'm going to make up a length of 2x4 or one inch pipe, extended with a piece of 1/2" all-thread so I can make a long diagonal jack to put pressure between the opposite wall/floor corner, and some sort of crossing support on the cabinet flange. Hopefully, with the rivets removed, I can jack things back into place, insert some 3/16" bolts to hold things in place, and re-install the rivets one by one. The trailer has not had any crashes, frame bends, or other calamities; I just think this is a natural consequence of the curved ceiling wanting to wedge the cabinet top inward.

Rivets vs bolts is an ongoing question, generating lots of opinions and anecdotal evidence. I've used a #10 brass bolt elsewhere when I needed something longer than the longest rivets Casita sent me. The head fits nicely under a rivet cap, and after trimming the extra length down to the nut with a Dremel after tightening, a rivet cap fits there as well. I'm really tempted to do that again. Have any of you heard of damaged fiberglass due to using bolts? I know it's often claimed that rivets are good because they break before damaging the glass, but I wonder what real evidence there is that bolts cause problems.....

Thanks,everyone, for your interest and suggestions! This is such a great group here.

Parker
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Old 06-20-2010, 01:29 AM   #7
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Quote:
Actually, on something that can flex a bit (like a fiberglass cabinet), wouldn't you start fastening at either one end, or in the middle and work in linear fashion? I understand torquing a head or a wheel, say, in a star pattern, because you do not want to warp it or have some weird imbalance. And the item to be torqued is fairly "solid."

But if something is flexible (such as fiberglass, or, say, a long wooden toerail on a boat), I would typically either start in the middle and work my way to each end, or start at one end and work my way to the other end (depending on the situation). So I did not end up with a "bulge" or "wrinkle" in the middle.

Raya
Hmmm. Good thought. But I feel that as you tighten, you compress the material a little, the next fastener a little more and so on so that by the time you get to the end, you have a lot of movement.

By fastening here and there won't you contain the movement and keep it distributed so you get a lot of little wrinkles instead of big ones? Especially tightening with Casita carpeting in between...

We can theorize until the cows come home and not get it correct; anyone out there have experience with this?
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Old 06-20-2010, 02:07 AM   #8
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Hi Roger,

On a relatively short cabinet and a carpeted wall, I don't think it will really matter which way it's tightened, really. So, I don't think it needs to be done like a head, or like how I would do a toerail.

Parker,

I think the "rivets give way before the fiberglass does and protect it" is fallacious. I say that coming from the fiberglass boat world, and also from experience with fasteners. I believe that what you want is a solid system, with tight fasteners. If the camper moves and a rivet pulls through the fiberglass, it's a failure not a "save."

Once movement starts, things will "work" and damage will be the result. I think this would be the usual reason for rivet failures. Keep things from "working" and you have a happy, monocoque-type shell.

If a tight rivet pulls through (when no other rivets have loosened and/or the camper has not flexed for some structurally wrong reason), then the answer is spread the load of the fastener (larger head, washer, backing plate, etc.), tighten the fastener, or attach in a way that will stay tight (tabbing, screw and nut, etc.).

I think that rivets were used in our campers because they were trying to make a very economical product with semi-skilled labor. Rivets are inexpensive and easy to apply in a production setting, therefore they fit the bill.

Not that there is anything wrong with a tight rivet in good shape. But their purpose is not so that they can break to save the shell.

Raya
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Old 06-20-2010, 06:14 AM   #9
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Parker,

I think the "rivets give way before the fiberglass does and protect it" is fallacious. I say that coming from the fiberglass boat world, and also from experience with fasteners. I believe that what you want is a solid system, with tight fasteners. If the camper moves and a rivet pulls through the fiberglass, it's a failure not a "save."

Once movement starts, things will "work" and damage will be the result. I think this would be the usual reason for rivet failures. Keep things from "working" and you have a happy, monocoque-type shell.

If a tight rivet pulls through (when no other rivets have loosened and/or the camper has not flexed for some structurally wrong reason), then the answer is spread the load of the fastener (larger head, washer, backing plate, etc.), tighten the fastener, or attach in a way that will stay tight (tabbing, screw and nut, etc.).

I think that rivets were used in our campers because they were trying to make a very economical product with semi-skilled labor. Rivets are inexpensive and easy to apply in a production setting, therefore they fit the bill.

Not that there is anything wrong with a tight rivet in good shape. But their purpose is not so that they can break to save the shell.

Raya
Raya,

This makes perfect sense to me. I've read many posts from people using bolts and not one yet of actual examples of fiberglass failures due to an unyielding bolt. Okay, bolts it will be! Fire up the impact wrench!! Just kidding. I think I'll go with brass bolts and stainless nuts under rivet caps. Brass is easier to trim to length after tightening so I can get the cap on. It's a one-time use each time, but starting with a little longer bolt and then trimming it makes it way easier to assemble and pull things together. I just read a reply to this same topic on the Casita forum. They installed a bolt at both ends of the cabinet flange (same spots mine failed) some time ago, and had no further problems.

Thanks again.
Parker
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Old 06-27-2010, 01:08 PM   #10
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I think I'm going to make up a length of 2x4 or one inch pipe, extended with a piece of 1/2" all-thread so I can make a long diagonal jack to put pressure between the opposite wall/floor corner, and some sort of crossing support on the cabinet flange. Hopefully, with the rivets removed, I can jack things back into place,
Parker,
You will find that a load stabilizer bar meant for pick up truck beds does just the trick.
It holds and jacks on an angle just right.
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