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Thread: Fiberglass truck camper modification

  1. #1
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    Default Fiberglass truck camper modification

    First off, I know that this is a boat building forum and my question pertains to A Bigfoot fiberglass truck camper, however, I have found the RV industry to be lightyears behind the boating industry in terms of products and repair methods. This is especially true with fiberglass shell campers like mine.

    My issue is the center lap seal of the clamshell (picture below). As you can see. The upper shell overlaps the lower shell. The manufacturer drives an absurd number of screws through the overlap and generally does a poor job sealing them. There is a piece of trim that hides the screws and creates a nightmare crevice that holds water. As a result, mine leaked extensively.

    I am trying to mod out this seam to make it bombproof. My thought was to use stainless screws and seal them with 5200 and then seal the bottom lap joint (about 1/8 inch clearance) with 5200 as well. I would like to then apply either a rubberized deck coating OR fiberglass over the whole thing as the primary seal (5200 is secondary in case coating fails of glass disbonds). I am not particularly concerned about aesthetics. Just want to keep the camper dry.

    What marine grade rubberized coatings would you use? Would you take the gelcoat down, or just clean and rough it? Is this a bad idea? If so, why? How you you foresee this failing?

    I don’t have a ton of clearance above and below the seam, due to through shell fittings but the fiberglass option shouldn’t see huge loads due to the joint design and the zillion screws. I can work around the penetrations. I have read a seam like this should extend 4 inches in either direction to provide adequate bonding, but that was for a structural seam (i.e. fiberglass, not screws/lip, carrying the load). What do yall think about the required margin to prevent disbonding? Is epoxy to rough/clean gelcoat a bad idea in this case? Should I take the gelcoat completely off?

    for the rubberized coating I would only have to worry about failure due to the flexing of the joint. My guess is that the marine industry has a solution that would easily handle my conditions.

    I have done some hand layup and vacuum infusion of carbon fiber laminates, but nothing in-situ like this. Making a laminate in a mold is a different beast from repair work like this (I assume).
    52FA8C67-1A2D-493A-99D3-59515E5251D3.jpg
    Attached Images Attached Images

  2. #2
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    Default Re: Fiberglass truck camper modification

    I'd send the top clamshell part to fg dust hell.
    (16 grit @5000 rpm)
    re glass the whole thing, a couplethree layers of staggered fg tape.
    epoxy of course
    5200 is devil sperm.

  3. #3
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    Default Re: Fiberglass truck camper modification

    I thought you boat guys love 5200 for permanent thru hull stuff

  4. #4
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    Default Re: Fiberglass truck camper modification

    5200 is wonderful for its purpose. It's when it gets used for stuff that other goop is better suited for that the going gets tough.
    Hope for the best, but plan for the worst.

  5. #5
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    Default Re: Fiberglass truck camper modification

    Quote Originally Posted by mmd View Post
    5200 is wonderful for its purpose. It's when it gets used for stuff that other goop is better suited for that the going gets tough.
    what goop would you use for sealing up the screws and the lap joint gap before glassing/painting over?

  6. #6
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    Default Re: Fiberglass truck camper modification

    If you never, ever want it to come apart again without a lot of cutting and cursing, then 5200 is the goop of the day. If you ever want to take it apart, thry 4200 compound from the same maker.

    But please be aware that, when it comes to questions of 'how to' and 'what stuff' here in The Bilge, no matter who says what, and no matter how qualified they are to say what they say, somebody will be along in a few minutes to say that they are all wrong and that you should used the stuff they are suggesting instead. Read, investigate, and use what makes sense to you.
    Hope for the best, but plan for the worst.

  7. #7
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    Default Re: Fiberglass truck camper modification

    I actually couldn’t take the shells apart even if I wanted to. It is 100% permanent. If i used another (4200 or 4000UV) it would be for the faster cure (although they do have a 5200 fast cure). I assume glassing over a curing sealant is not good practice. I know the drill of naysayers and brand loyalists on message boards. Mostly, I just look to avoid major mistakes. You know, the ones that are super obvious to anyone that has experience. I take brand/product recommendations as a starting point for my research. Sometimes I wish there was a website to hire DIY consultants for projects. I’d totally pay some salty retired guy to come look over my shoulder and show me the ropes.

  8. #8
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    Default Re: Fiberglass truck camper modification

    Once you get 5200 or 4200 (pretty much any goop, really) on a surface, fiberglass WILL NOT stick to it. No how, no way. If you want to put on a surface layer of more 'glass, fill & fair with a polyester-based body putty, then 'glass over, fair, & paint. If you are not going to add any more 'glass layers after the fact, I'd sand, fair, and paint first, then use a goop of your choice to seal screw holes and seams. Careful masking beforehand will make the goop lines nice and straight and clean - just pull the tape off before the goop cures.
    Hope for the best, but plan for the worst.

  9. #9
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    Default Re: Fiberglass truck camper modification

    Quote Originally Posted by MC_AK View Post
    I thought you boat guys love 5200 for permanent thru hull stuff
    We don't all listen to Jimmy Buffet either.
    Is this canopy supposed to flex?
    In the photos, is one part the steel pick up cab?

  10. #10
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    Default Re: Fiberglass truck camper modification

    No Buffet?!? So disappointing
    It is not supposed to flex in the sense of an elastomeric seal. The screws pass through both the upper and lower shell so they prevent any vertical joint movement. I suspect the original design was for the screws to keep the two shells clamped together and the construction adhesive between them was supposed to carry the bulk of the shear load. In reality, the water degraded and failed the adhesive and the shear load was carried by the screws. I am inferring this from the goopy mess of wet adhesive I dug out and also the cracked gelcoat around my screw holes. The wall construction is a 1.5 inch eps core, 1/8 in fg outer skin, 1/8 in luan inner skin SIP. Should be pretty stiff in bending, but it is also bouncing down the road on the back of my truck, so I expect some flex. Nothing crazy though. The metal in the picture is the door frame. This is looking down the seam of the rear facing wall.

  11. #11
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    Default Re: Fiberglass truck camper modification

    Good to know. I planned to seal the lap and the fasteners and clean up all the squeeze out. I plan to sand down the gelcoat before glassing, so any residual 5200/4200 should be removed before glassing. Even if it doesn’t bond at some places around the screws, as long as it is sealed up and water can’t get in, it is good as I am not replying on this to be structural.

  12. #12
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    Default Re: Fiberglass truck camper modification

    After sanding, and before 'glassing, wipe the area down well with a solvent such as acetone. Good ventilation and rubber gloves are recommended.
    Hope for the best, but plan for the worst.

  13. #13
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    Default Re: Fiberglass truck camper modification

    In fiberglass boats, there is the hull-to-deck join. The flange of one part ( hull) overlaps the flange of another part ( deck--usually the gunwales and cabin top). The best seams are glassed together. Near as good, and since your join won't be subject to the forces of 30 knot speeds in three foot seas, are screws and goop--like 5200 or Sikaflex. This joint is covered by the rub-rail and is not visible outside the boat.

    Like your joint, they use a lot of fasteners. Partly this is because the two parts are kind of floppy and don't necessarily fit together perfectly when they first come ou of the mold; the screws --plus ample use of a grinder--brings things together with ( hopefully little daylight showing through).

    In a production setting, this all happens at once as the deck is hung over the hull, dry fit/ ground/ pre-drilled. Then goop is applied. Then the parts are brought together.Much banging and pushing and pulling and swearing may ensue.

    Then a couple of guys with screw guns run around the boat.

    Then ( usually a senior man) a worker with a single gloved hand circumnavigates the vessel and with the aplomb of a concert conductor, tools the squeeze-out from the joint into a nice mini-filet.

    Then the rub rail is installed.

    Next.


    These joints remain watertight for maybe five years. Then, the owner needs to re-caulk by gunning in goop from below and tooling the excess with a gloved finger.

    There's a variety of geometries. Here are a couple of flavors to get the gist.


    Screen Shot 2021-05-06 at 7.17.45 PM.jpg



    At any rate. Screw and glue is what I'd advise for you.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  14. #14
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    Default Re: Fiberglass truck camper modification

    [QUOTE=wizbang 13;6444596]We don't all listen to Jimmy Buffet either.

    Wait, what??

  15. #15
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    Default Re: Fiberglass truck camper modification

    Contact Bigfoot directly. I have a 35 year old Bigfoot camper and wanted information so I could place a roof rack on it. This was just after the new owners resurrected the company so the information on older models was limited, but they went to a lot of trouble to help me. I was hugely impressed by the people there.

    Jamie

  16. #16
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    Default Re: Fiberglass truck camper modification

    ^DING! DING! DING! We have a winner!

    Great information & advice, Jamie.
    Hope for the best, but plan for the worst.

  17. #17
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    Default Re: Fiberglass truck camper modification

    Quote Originally Posted by Breakaway View Post
    In fiberglass boats, there is the hull-to-deck join. The flange of one part ( hull) overlaps the flange of another part ( deck--usually the gunwales and cabin top). The best seams are glassed together. Near as good, and since your join won't be subject to the forces of 30 knot speeds in three foot seas, are screws and goop--like 5200 or Sikaflex. This joint is covered by the rub-rail and is not visible outside the boat.

    Like your joint, they use a lot of fasteners. Partly this is because the two parts are kind of floppy and don't necessarily fit together perfectly when they first come ou of the mold; the screws --plus ample use of a grinder--brings things together with ( hopefully little daylight showing through).

    In a production setting, this all happens at once as the deck is hung over the hull, dry fit/ ground/ pre-drilled. Then goop is applied. Then the parts are brought together.Much banging and pushing and pulling and swearing may ensue.

    Then a couple of guys with screw guns run around the boat.

    Then ( usually a senior man) a worker with a single gloved hand circumnavigates the vessel and with the aplomb of a concert conductor, tools the squeeze-out from the joint into a nice mini-filet.

    Then the rub rail is installed.

    Next.


    These joints remain watertight for maybe five years. Then, the owner needs to re-caulk by gunning in goop from below and tooling the excess with a gloved finger.

    There's a variety of geometries. Here are a couple of flavors to get the gist.


    Screen Shot 2021-05-06 at 7.17.45 PM.jpg



    At any rate. Screw and glue is what I'd advise for you.

    Kevin
    Thank you for the excellent information on boat construction. The camper shell joint is most similar to the overlap configuration. I may ultimately end up modifying the metal trim with weep holes so it doesn’t hold water, fill old stripped out holes with thickened epoxy, reinstall stainless steel hardware sealed with 4000UV. I am testing 4000UV now on some test pieces to see how “non-permanent” it is. I have read Anti-Bond works well for removal of 4000UV residual.

  18. #18
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    Default Re: Fiberglass truck camper modification

    Quote Originally Posted by Jamie Orr View Post
    Contact Bigfoot directly. I have a 35 year old Bigfoot camper and wanted information so I could place a roof rack on it. This was just after the new owners resurrected the company so the information on older models was limited, but they went to a lot of trouble to help me. I was hugely impressed by the people there.

    Jamie
    I am in contact with Grant at Bigfoot. He has been extremely valuable in describing the interior construction. I think he needs to be careful in his recommendations for repair as there are some liability issues, especially since my camper was built by the former Bigfoot. I am not trying to be a jerk here, Bigfoot campers are good, but far from the pinnacle of design. Like all RV’s, cost drives every decision. This “cheap” approach carries over into conversations about modifications and repairs. They can tell you how to recreate their cost-effective construction, but they are likely not the best audience to workshop superior (but costly) design mods. I would think the boating community would have similar experiences with mass produced boat manufacturers.

    This is why I reached out to a boat builders forum. It seems like those that build their own are always thinking outside the mass-production box to come up with the best (not the cheapest) solution.

    Having said this, Grant has been great and very responsive, but he owns the company. It is unreasonable to expect him to spend hours workshopping fixes.

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