Warning about a roof top storage box

[DaHose]

Hey everyone. I am about done with my cabover rebuild and want to share something that I think is important about a roof top storage box.

I removed the storage box to work on the roof and I had not intended on putting it back up there. That meant I had 6 lag bolt holes to patch.

The 3 mounting holes furthest back are on the upper slope of the roof. I used a blade to remove all the silicone caulk someone gooped on there, then sanded the aluminum clean and put Eternabond patches over the holes. I am confident that will be nice and water tight.

However, the three holes on the lower part of the slope had a fair amount of corrosion around them and would require a bigger piece of Eternabond to seal them. I was fine with that, but as I sanded off the oxidation and muck around the big holes I realized there were a bunch of pinholes all over that area of the aluminum roof. Looking closely at everything, I realized that trapped dirt and water under the lower edge of the damned box caused galvanic corrosion all over the place. There is basically a 12" or so strip across that lowest area of the aluminum roof (where the box would have trapped all the moisture) that is pockmarked with pinholes.

Aluminum roof's are supposed to be just about maintenance free. What this shows me is that roof top boxes are a BAD IDEA!! Now I have to fix not just 6 big holes, but do a larger scale repair of that entire forward section of the roof.

My plan is to use some 6" wide u seal tape laid in an overlapping pattern and leave a 2" outer edge. That will cover the area like a super sticky aluminum "patch". I will then cover the seams of the large patch with my leftover Eternabond and I will also seal the edges with Eternabond. I will post pics to this thread when I am done.

Jose

[joanne0012]

Snowman9000 wrote:
Actually Lazy Daze's are affected by leaks, and until fairly recently had multi-piece aluminum roofs. The roof seams have been the source of many of the leaks. LD's do seem to last a lot longer overall, and due to that and to owner neglect of seams typical of all RV owners, older ones often have suffered leaks.

My 1994 Lazy Daze had a one-piece roof, and I'm pretty sure they had gone to one-piece several years before that. The edges do need a new roll of Eternabond every 8 or 10 years for maintenance.

[DaHose]

I've been trying my best to take pics. and notes at each step of the way. I will post the complete document in a dedicated thread when its ready. I will be sure to put it here in the class C forum.

Jose

[Dan_L1]

Jose,

Do you have any pics or a write up of your cabover repair?

I'm looking at that on our 97' Coachmen.

Dan

[DaHose]

Eternabond those seams, people.

Jose

[Snowman9000]

Actually Lazy Daze's are affected by leaks, and until fairly recently had multi-piece aluminum roofs. The roof seams have been the source of many of the leaks. LD's do seem to last a lot longer overall, and due to that and to owner neglect of seams typical of all RV owners, older ones often have suffered leaks.

[DaHose]

Well as I said, the rest of the roof (even the upper part that was under the box) is in great shape. Fleetwood did a great job selecting a durable coating.

The only spot that is bad is what was under the box and on the surface that would hold moisture. Hence my dislike for those stinkin top boxes.

That's a good point, pegleg. Better keep my sweat to myself.

Jose

[tatest]

Most structural alloys need corrosion protection, even when the only other metals around are other aluminum alloys. Slight differences in chemistry will set up local cuurents. Dealing with corrosion in aluminum was the second largest maintenance cost, after engines, for our larger military aircraft in the 50s through 70s, when aircraft were no longer treated as disposable as they had been in WW2. So the problem is not just about rooftop boxes, it is about monitoring and treating corrosion in aluminum. Good coatings help, which is why LazyDaze uses aircraft grade coatings.

[mlts22]

I have yet to hear about a Lazy Daze "C" trashed due to leaks, while other bands, it is almost common to read about massive cabover repairs needing accomplished after about 3-5 years.

That is a good point about the metal corroding. I wonder if putting a piece of rubber or plastic down between the aluminum roof and the carrier would prevent that.

[Peg_Leg]

But look at the knowledge your gaining. Just don't let to much of it drip off your forehead onto the alum as the salt content will cause more damage.

[DaHose]

The rest of the roof looks great, but now I have concern about the ladder handles and the rear rack. They have a bunch of goop all around them that I bet isn't sealing well and lets water in too. I'll tear into that after everything else is done. OY! The hits keep on coming.

Jose

[Dakzuki]

Any time you mate up dissimilar metals you run the risk of galvanic corrosion. It is a common issue that has to be addressed in the aircraft industry. If you think an RV is a grungy environment with corrosion issues, you should see a neglected commercial airliner.

I presume the cargo box mounts were steel. This can be mitigated by isolating the cargo box mounts frmm the roof (like with a rubber pad). The fasteners holding them together need to be isolated too. This can be done with nylon sleeves, washers etc. Kind of complicated but doable. This is only an issue when everything is wet for protracted periods of time. Trapped water must be considered too.

[j-d]

A lot of older RVs had a one-piece rolled aluminum roof. A great idea but there were two shortcomings.
First, that big sheet had enough expansion/contraction to lead to leaks around the edges.
Second, corrosion pinholes, even out on the open surface.
Our '84 Holiday had a multi-piece aluminum roof. As I recall there were four sheets about half width by half length of the roof. Curved down to the walls and Riveted to the aluminum frame through a sealant compound, then taped over. It leaked where the curved parts met the fiberglass front and rear end caps. I removed all that Butyl Tape and replaced with 4" EternaBond One-Step. Solid job and no further leaks.
** Somebody please validate or correct the following that I understand to be true**
Lazy Daze, a top builder, uses a one-piece aluminum roof to this day, but they offer superior craftsmanship and I understand they have to get the material from a supplier in Germany.