Repairing rotten thermopanels

[lotsofspareparts]

Doing a tear down and rebuild of my upper bunk, have got 80% of the ceiling removed (pretty much fell off) and now have to remove what remains on the dry side of the coach.

I have also found more than a dozen holes in the aluminum skin so far. I know I can seal them with eternabond tape, but this roof has NEVER been coated and am wondering if I should worry about more of them over the dry panels. Does the corrosion start from the inside out?

I am also wondering how to disassemble the walls in the head to replace those ceiling panels as well.

[Oz]

I don't know how to do it without damaging the underlayment at least to some extent, but a paint scraper works quite nicely.

[fgutie35]

When I removed a 1 foot square of plywood from one of the walls on my Elandan that was rotten, I used an old fillet knife and a small butane torch to heat up the knife. If you try to jank it out dry, big pieces of the foam will come with it(don't ask me how I know). heating up the knife and sliding it right behind the plywood worked very good for me with the least amount of damage to the foam. Just make sure not to stay in one spot for too long cause the foam tends to shrink when it melts. Similar to a styrofoam cup.

[lotsofspareparts]

I have already removed 90% of the foam. I did that because the plywood had seperated from the aluminum roof and the whole are above the bunk was sagging. It got really bad first time it rained, I had a big vinyl bubble filled with water. I put a 3 gallon bucket under the bubble and stabbed it with my pocket knife and watched the water flow.

I went to Lowes today and was unable to find the high density styrofoam. They had 2"x2'x8' sheets of the high density but nothing in 3/4in. I have found all of the other materials I require except for the foam.

Anyone got a lead on the foam??

I have also decided to leave the panels in the head alone as the damage is not as bad as I originally thought. I am however going to be replacing the entire panel above the bunk, and the entire plywood section below the bunk. New paneling and ceiling covering throughout the whole rig and she should be good to go. And seal the roof of course.

What does anyone reccomend to use to clean the roof before hand? I saw something called TPS or IPS or something like that on another post, but no description of the product or where to purchase it.

Any help would be greatly appreciated!!

[Bfrisch143]

try calling (Palcos) ,  1-586-774-3334   they may answer your question about removal of a glued on panel , if that's what your asking .   good luck       

[JDxeper]

Pharaoh has a good post on how to clean and seal the roof, the TSP is Trisodium phosphate, it is available from most paint stores, it is a cleaner and  used to kill the gloss, so material will stick to the surface being treated.  Most people use it in combination with a phosphate soap, to clean the surface before painting or in this case applying kool seal to the roof. 
Most untreated roofs will have many pin holes in them.  Winnebago used some metal( steel) staples and corrosion with the al roof happens.  I taped all pin holes I could find after cleaning them treated with kool seal, also taped all joints and seams and all vents.  Its a tough fight to keep them dry.

[lotsofspareparts]

I appreciate everyones responses. Coupe of questions,

Do I have to be concerned about pinholes over the portions of thermopanel that are dry? I plan to seal the whole roof hopefully this next week if the weather man is telling the truth.

Does anyone know where I can purchase the finely ribbed aluminum that is used above the cab, It is the panel under the bunk, it is full of so many pinholes and has fell victim to a large amunt of electrolosis around all of the screw holes. I personally think it maybe easier to replace it that trying to tape it. That is unless someone has a better suggestion on how to save what I have.

Does anyone have any information as to how these are framed up in the front? The majority of what I removed was plywood, but also removed some chunks of solid wood (rotted solid wood) from around the perimiter of the bunk. I downloaded the coach manual but it wasn't to descriptive in this area.

I appreciate everyones advice!

[Oz]

The pinholes can occur anywhere moisture is underneath the aluminum, whether it be on the roof, or the side panels as well.  As the roof bows over time, water which leaks in one place can travel to places you wouldn't expect.  A good way to look for holes is to take a hose and wet down a portion of the roof.  Sponge off the bulk of it and press down on the roof surface moving slowly and methodically over the area, Look for water seeping back up through pinholes as you push down.  Wipe them dry and circle them with a permanent marker as you go.  This does take time and no, it isn't anywhere near as fun as winning a free ticket to a pig roast, but it will clearly define the areas and extent of the corrosion.  You can then determine if it's feasible to use Eternabond tape and go over the existing holes, or if a replacement is in order.

Extruded aluminum can be purchased in varying sizes and types of extrusions from numerous commercial sources.  There are some suppliers listed in the Resources section of the Member Area and any addtional sources are greatly welcomed.

The wood framing is one thing Winnebago totally neglected to make any documentation for.  My guess is that they figured the wood would never need to be replaced... ha........ ha.....   ha.

I've not heard of any member who has actually diagrammed out the framing since the repairs are usually localized or it's an entire roof replacement.  My suggestion on that one would be measure the wood sizes which are left undamaged for girth.

In the photos you presented, the roof aluminum is definitely to the point that it should be replaced if at all feasible for you, since the pinhole issue is quite extensive.

There is also a post on glue recommendations for when you get to replacing the "skin".

In addtion, you may try to contact user Matt10.  He just did a major thermopanel replacement on his Class C.

[lotsofspareparts]

Thanks for the reply Pharaoh, I have been kicking the idea around if I should just go ahead and replace that portion of the roof skin, it is pretty far gone. The roof is one piece of aluminum so that will probably wind up being an interesting chore just replacing the forward section.

I have also noticed on alot of the previous posts that alot of users are using silicone to seal some things on the roof and other spots of the RV. We use Sikaflex 291 and Fast Cure 3M 5200 at work on our yachts and I have found both of these products to be the perfect sealant to use in circumstances where a fitting or hatch will be exposed to large amounts of water (such as a roof). Do you know if any of the other members have had good experience using these sealants, or have tried these sealants instead of silicone.

Thanks for the advice on contacting Matt10, I will do just that.

[Oz]

Boating sealants would be a very obvious choice for such use for us, as you've mentioned.  One point in mind though, unless the price of these marine sealants are on a par with those found at Lowe's or Home Depot and such used in the home maintenance industries, price is always a big factor for us.  From my limited experience with boating products, if it's "marine grade" it's around 4 or more times the cost of typical products for landlubber use.

But, the choice on anything always comes down to what a person is able and willing to spend on any given item.

[lotsofspareparts]

The sealants aforementioned are expensive, as they are intended for marine use, but I have noticed while exterior silicone that we use to seal small joints between 2 finished fiberglass parts (mostly for looks) will need to be replaced in about 4-5 years under constant exposure. Sika and 5200 never have to be replaced as there is no deterioration, other than a change in color due to UV exposure (white turns yellow, black turns light gray). I guess it would really depend on how long you were planning to keep an RV.

Another thing I have noticed is the sheer lack of stainless fasteners on this thing. Even the interior of our boats get stainless fasteners (304 for interior, 316 for exterior). Even the staples we use are 304 stainless lol.  I wonder why Winnebago would not do the same thing considering the exposure these units have to the elements. I am guessing it falls back to the bottom line. Pardon the rant, I wanted to get that off my chest to someone who would probably understand. I do however plan on replacing every single fastener I can get my screw gun on with 316 stainless, we buy in bulk at work and get a great discount.

[ibdilbert01]

sheer lack of stainless fasteners

I'm a big fan of stainless as well, but its kind of hard to use them on the surface, as stainless fasteners in aluminum can  increase corrosion.

Sounds like you have plenty of experience with marine applications, I'm excited to see how your go about making your repairs.   

[lotsofspareparts]

Actually you have that backwards, any other ferrous metal (besides stainless) directly attached to aluminum (non ferrous) will cause corrosion, otherwise known as electrolosis. If the stainless fitting being used against the aluminum is grade 304 or better you should never have a problem, unless it is used underwater in a salt environment (we don't drive submarines so I think we are all safe) that is when "zincs" come into play. The ingredient in stainless steel that makes it "stainless" is chromium, or chrome. Alot of  people don't know that stainless steel just like regular steel will rust. It is the oxidization that takes place when the fitting is exposed to air that actually prevents it from rusting. If you have a stainless screw and screw it in to something on a wet day with no type of sealant behind it, it will eventually weep rust from behind the screw head.

We actually use aluminum fuel and water tanks in our yachts. We use brass valves to turn the tanks on or off. By ABYC regulation we have to use a stainless hex bushing between the 2 metals to prevent electrolosis. They won't let us thread the brass valve directly into the aluminum because it will fail eventually.

The majority of "stainless" fasteners you purchase at a hardware store are very low grade stainless steel. Always keep that in mind.

Check us out here http://www.fathomyachts.com

[Oz]

For every repair job which required removing aluminum trim I used stainless screws to reinstall.  Some of these repairs are over 4 years old and there is no blessed sign of corrosion.

[DaveVA78Chieftain]

used underwater in a salt environment (we don't drive submarines so I think we are all safe) that is when "zincs" come into play

Careful now, some of use do play with submarines (Submarine Sonar Systems).
And yes, I have inspected a lot of "zincs" in my day! 

Dave

[ibdilbert01]

Actually you have that backwards

Ah, so I'm a bit backwards, we all have our faults...    W%

I once had a 1973 boat that I restored and used stainless screws to fasten the aluminum handrail down.  After many seasons I removed part of the handrail to mount a trolling motor, every one of the screw holes corroded.   Since then, I've never tried to mix stainless and aluminum again. 

There is also some mixed feelings on the airstream forums.  Some of them claim its ok, some don't.   Maybe its just the quality of materials.

[lotsofspareparts]

You always want to use a sealant of some type behind a stainless fastener when it is being used against a dissimilar metal,  it can be silicone or any other type of soft sealant. It will seal out any moisture that could get behind the fastener which will cause the stainless to corrode (due to lack of oxygen exposure), and will eventually spread to the aluminum as well. But as a general rule, stainless and aluminum are compatible metals.

[lotsofspareparts]

Got ahold of Interstate Metals Fabrication down in Oregon today, $550 bucks for the roof, the 4in brake folded aluminum with pittsburgh seams and prepainted, and a sheet of 3/4 blue board. Freight included.

[lotsofspareparts]

Plans are sort of stalled at the moment due to the foul weather up here in the Northwest. I really wish I had someplace indoors I could work on this thing.

[lotsofspareparts]

O.K. Was able to order 2 sheets of the 3/4 x 4' x 8' Dow Blue Board Styrofoam on Lowes.com, unfortunately it won't arrive until Oct 1st.

The rebuild is soon to start.

[jkilbert]

on my dad's 74 itasca we had the same problem in the overhang area. his method of repair was to strip out the bunk, saving as much trim as possible. we then wirebrushed the aluminum by hand to remove any loose corrosion and foam/wood. we then taped any holes, from the outside and applied  generous layer of fiberglass epoxy resin. we built up to approx 1/4 inch thick then put 3/4 treated plywood over that then reassembled the bunk. this took care of the pinholes in the aluminum and added strength to the bunk. so far it's been holding up well. on the outside it was just normal body prep before paint.