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Topic: Bulkhead Skin Adhesive (Read 1297 times) previous topic - next topic

Bulkhead Skin Adhesive

I'm cleaning up and resealing some exposed metal on my rear bulk head. I pried some of the skin back and removed some torn metal skirting and was pleased to find very solid metal without any rust jacking (consistent with Keith R's PPI). I need to stick it back to the steel tubing before sealing the entire seam with 3m 08308. I am considering using 3M Panel Bond (08115) to do so. My concern is that this will be permanent...it's not going to ever come off again. Can anyone make an argument for why I might want to use a lesser adhesive that could be separated in the future?

Re: Bulkhead Skin Adhesive

Reply #1 –
Elliot,

no input on your permanent glue choice, but curious, was there a certain reason you chose the 3m 08308 for sealing the seam? Is that a go to that most use for the application?

Thanks Mike.

Re: Bulkhead Skin Adhesive

Reply #2 –
Quote from: mkc1962 –
was there a certain reason you chose the 3m 08308 for sealing the seam?
My buddy manages an automotive body shop in Boise and that's what he recommended. Followed by a coating of 3M 08881 rubber undercoating, mostly for cosmetic appeal.

Re: Bulkhead Skin Adhesive

Reply #3 –
 ^.^d

Re: Bulkhead Skin Adhesive

Reply #4 –
Elliott, check the working time,  I have similar panel bonding adhesive and the working time is quite sort but it works great.

You should (must) clamp it.  If you are going to use 2x4s and jacks be sure to use blocks on the coach suspension so that if air is lost the floor won't come down and crush it against the jacks and blocks.  Clamping force needs to be enough to squeeze the adhesive but still leave a bond line, not too much.

Re: Bulkhead Skin Adhesive

Reply #5 –
Why not VHB tape?  Holds the skin on semi trailers, windows in skyscrapers, solar panels on roof. Skip the whole clamping and intermittent bond issue.

Re: Bulkhead Skin Adhesive

Reply #6 –

Even VHB tape suggests some pressure when bonding surfaces that are not perfectly smooth.  It would work well, make sure you choose a VHB tape with a thick enough core to conform with surface variations and allow the tape sticky part to make best contact.

I have had success with this variant.  5952.  There are many different VHB tapes for different applications and situations.
Amazon.com: 3M VHB Heavy Duty Mounting Tape 5952, 1.52" width x 5yd length...

Use a surface prep/adhesive promoter.  Do not use solvent based cleaners (acetone, naptha, xylene, paint thinner, turpentine etc) alone with any VHB tape, it interferes with the bond.  If you do be sure to follow with an IPA/water (50/50) mix or the 3M cleaner/prep.  IPA = isopropyl alcohol. 

Amazon.com: 3M 111 Clear Tape Primer - Liquid Bottle - For Use With 3M VHB...

For help selecting a good tape see:
https://www.3m.com/3M/en_US/vhb-tapes-us/product-selector/
https://multimedia.3m.com/mws/media/1204168O/3m-vhb-tape-design-guide-high-res-pdf.pdf

More on surface prep:
https://www.3m.com/3M/en_US/bonding-and-assembly-us/resources/full-story/?storyid=b3996cbd-9954-455f-8e72-88e452ca38c0
https://multimedia.3m.com/mws/media/66019O/vhbtm-tape-surface-preparation-technical-bulletin.pdf

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Bulkhead Skin Adhesive

Reply #7 –
The video from AM Solar shows using alcohol to prep the roof. Lower right hand corner in the link.
I followed their instructions and am having no problem.

Mounts

Re: Bulkhead Skin Adhesive

Reply #8 –
I should have said (fixed my post) to say that petroleum-based solvents can interfere with the VHB tape bond, use 50/50 mix of IPA and water (probably distilled) after any other cleaners before VHB tapes. Wipe down both surfaces well and allow to dry. Maybe twice. I added a couple surface prep links to the post above.

Re: Bulkhead Skin Adhesive

Reply #9 –
Quote from: Roger & Susan in Home2 –
I should have said (fixed my post) to say that petroleum-based solvents can interfere with the VHB tape bond, use 50/50 mix of IPA and water (probably distilled) after any other cleaners before VHB tapes. Wipe down both surfaces well and allow to dry. Maybe twice. I added a couple surface prep links to the post above.

India Pale Ale?

Re: Bulkhead Skin Adhesive

Reply #10 –
Isopropyl alcohol.

Re: Bulkhead Skin Adhesive

Reply #11 –
Elliot
What happened to the little bit of metal that supported the skin?
Are you going to replace it?

Re: Bulkhead Skin Adhesive

Reply #12 –
Quote from: Lt403 –
Elliot
What happened to the little bit of metal that supported the skin?
Are you going to replace it?
It was pretty beat up and bent/torn in a couple spots so I removed the section you can see in the picture. I don't think it is needed if a good adhesive and seem sealant is used. I am waiting for a guest to leave before I crawl under the coach and take a look at the rest of it but I might just remove all of it so I can get a nice clean seam all the way down. If it looks like it's still doing it's job I might leave it but I'd probably feel better knowing it's all water tight.

Re: Bulkhead Skin Adhesive

Reply #13 –
Thanks

Re: Bulkhead Skin Adhesive

Reply #14 –
I ultimately decided against using an adhesive. I didn't want to solve the small short term problem by introducing a long term problem if I ever need to work on the bulkhead. I instead opted for stainless steel screws and then will seal the seem and around the screws with the 3M stuff.

Re: Bulkhead Skin Adhesive

Reply #15 –
Also, for anyone tempted to pry back the sheet metal That LT403 asked about in reply #11, do so with caution. In it's unmolested form it creates a water tight seal But once you pry it back it'll never go back to a flat/tight form again. You will likely end up doing something similar to what I am doing now.

Re: Bulkhead Skin Adhesive

Reply #16 –
I've had gaps there since I bought the coach.  I spoke to Keith R about it, and he told me not to be overly concerned about it.  He did some resealing, but I see that its pulled away again leaving a few gaps along the edge between metal and fiberglass.  Definitely going to need something more robust and airtight like you are doing to keep it sealed and watertight. 

But now I'm thinking its a bit of a catch 22.  When I had my fresh water tank overflow issue the other day, I'm pretty sure the was majority of the water that seeped in, ran out of the bulkhead via those gaps.  Had it been sealed up watertight, I'm probably be looking at the beams sitting in 1/2 to 3/4 inch of water an much further forward in the bulkhead.  I think I dodged a bullet because of those gaps.  On the other hand, I can see where water being thrown up from the road driving could be an issue, particularly from salted roads.

I still want to seal up up the way you are, but think I'm going to make rerouting the fresh water overflow to vent from the bottom a prerequisite.

Re: Bulkhead Skin Adhesive

Reply #17 –
The OCD corner of my brain took over and decided I wouldn't be satisfied unless I sealed the entire seam. Currently waiting on a 2K epoxy primer and then I'm going do the whole shebang.

Re: Bulkhead Skin Adhesive

Reply #18 –
Quote from: Elliott –
The OCD corner of my brain took over and decided I wouldn't be satisfied unless I sealed the entire seam. Currently waiting on a 2K epoxy primer and then I'm going do the whole shebang.

Never done that.  But, I would likely use a product that had a little flexibility in it.

There will be some expansion/contraction between FG and steel with temperature fluctuation and likely a little movement with body flexing going down the road.  Yes, this IS speculation on my part. But, there are plenty of sealants that retain flexibility, yet do a good job of sealing.
 

Re: Bulkhead Skin Adhesive

Reply #19 –
So I'm really happy with the 3m 08308 seam sealer. It's easy to work with, you can build it up, and it's ready to paint after 15 minutes. It dries shiny and hard, but not brittle; plenty of flex in it, kind of like a stiff taffy.

The only downside is that the required primer is hard to find locally and it needs a special applicator gun. Otherwise it's absolutely perfect for this job.

I coated over it it with 3M rubber undercoating for extra piece of mind. As with all body work, 90% of the effort was prep.