Fibreglass Cracks

posted in: Painting the Outside 15


” We are going to start the exterior updates and have some questions.
If you have the answers or can send me to links that I can research.
1. Fiberglass cracks. We assume we need to grind it down, create a channel to put fiberglass in – do we use mesh or strand?
2. Do you have a recommended brand of fiberglass to use?
3. We are painting it ourself. What brand of paint and where do you look for the supplies? Boating supply?ow do I fix”


First I always encourage people to go slow.  Try out the trailer, use it, see how you like to camp, you may want to change something.
The last thing you want is a finished outside and then have to touch-up or patch something.
I also recommend the last thing you do is the outside finish,
A couple of questions on the cracks, first any crack in fibreglass is the result of stress, this stress could have been caused by snow on the roof or a bent or broken frame.  You always want to identify why the fibreglass cracked before you try to repair it.  If you don’t fix the cause then the cracks will reappear.  Second how deep are the cracks, there are different processes to use if the cracks are just in the surface and the gel coat vs cracks through the fibreglass matt that effects the structure.  The best source for information on fibreglass and repair is from fibreglass boat repair, our trailers are exactly the same and the repair process is identical.
Just about all polyester fibreglass resin is the same, so Bondo, 3M, any of those are good quality and available ot Home Depot, Canadian Tire, etc.
For DIY paint jobs I recommend using the Roll & Tip method (again used on boats) using marine topside paint.  I personally like Interlux Perfection, this is a premium quality 2 part top coat and it is available in Calgary at Industrial Paint and Plastics   they can tint the paint to almost any colour. I think is about $85 gallon.

15 Responses

  1. Seraphena
    | Reply

    Hi Ian. My question of the day to you is; the inside insulation has come off the ceiling beside the door entrance. What is the best product to adhere back to the fibreglass shell? Was thinking of contact cement but not sure. Also I would think something that works quickly as not sure how I would keep it up while it is drying

    • Ian
      | Reply

      You are right on the mark, contact cement is the correct adhesive to use. Use high quality contact cement, one that will withstand temperature extremes. The absolute best product is automotive headliner adhesive but it can be difficult to find, especially in smaller quantities so look for a quality brand like 3M or similar.

  2. david wilder
    | Reply

    hi Ian

    I purchased the door seal from vintage trailer…the one you suggested on your site. any tips on installing it?

    • Ian
      | Reply

      Hi David

      The seal works excellent and you can install it either around the outside edge of the door or the inside edge of the opening, in both installations the “flap” faces towards the weather.
      The advantage to installing it around the opening is that any water that drains off the roof are diverted by the seal on the body opening. I installed mine around the door and in heavy rains water can eventually seep past where the seal contacts the body.

      On mine I have installed a secondary small seal around the door opening to supplement the main seal. In short the best place to install the seal is around the door opening, this location addresses both leak situations.

  3. Bill-1
    | Reply

    I read about the comment about stress fractures. I have a crack around the door upper right hand side about three inches long. It is about 2 inches from the upper curve of the door. What can cause that and is it typical

    • Ian
      | Reply

      Common causes for cracking in this area can be from a bent or cracked frame, usually either the left frame rail behind the axle is bent down or the front right frame section in front of the doorway is bent down. If the frame is OK then it could have been caused by an impact to the roof area or excessive snow load, but both of these causes will also show considerable spider cracking in the gelcoat
      Check out these 2 articles, they will help you diagnose the possible cause and

  4. Bill-1
    | Reply

    What is the best way to clean mold in a 13ft boiler white liner inside the camper

    • Ian
      | Reply

      Hello Bill

      The ensolite covering the walls is extremely durable, you can use most any household cleaner, recommendations include; Spray 9, Simple Green, Magic Eraser, Ammonia & water, etc.
      Let me know what you use and how it works

  5. Nancy Flemming
    | Reply

    Hello Ian, Thank you for all the information. I have recently purchased a 1976 13′ boler that I will be redoing this spring/summer. I am looking at taking out the porta potti under the front bottom bunk and putting in a small dinette, so we can leave the back bed made up. My plan it to remove the door from centre section and put in a table that could be put down to create a bed if needed, I would cut down the existing cushions for seating. My question is would this create any structural problems?

    • Ian
      | Reply

      Hi Nancy. The only structural component at the front where you are working is the horizontal piece just below the window where the hinges for the upper bunk were screwed into.

  6. Nancy Flmming
    | Reply

    Thank you, that is good, looks like it will be a fairly simple change, I am also considering leaving the top bunk, but that may change when I get into the project.

  7. Cecily Evans
    | Reply

    Hello Ian
    I am looking into replacing the front and back windows in my 1973 boler, 13 foot. I was wondering which is better or what the difference is between the one piece locking gasket and the two piece locking gasket? Also is it a 1/4″ thick piece of plexiglass that I order for the window?


    • Ian
      | Reply

      Hi Cecily. Both the one piece and 2 piece locking gaskets work equally well, the one piece has a smoother finish and looks a bit better to some.
      It is important to use 3/16″ or 4.5mm thick Plexiglas for the front & rear windows, DO NOT USE 1/4″, it is too thick and will not bend into the compound curve to match the body.

  8. Greg Wedgewood
    | Reply

    Just starting a complete cabin off frame rebuild of a 1975 13ft Boler. I have many questions.
    1. Is there a replace furnace available.
    2. How best to hide the Ensolite seams. (someones previous caulking is a mess)
    3. I need to replace the door handle/lock. Registration says this is a 1975, but I believe this to be a guess. Is there a sure way to tell if it’s a ’74 or ’75.
    Thanks, Greg.

    • Ian
      | Reply

      Hi Greg, here are my answers to your questions
      1) There in not a direct replacement, one option I like is the Propex heaters, they are small, quiet and one unit can be mounted outside under the trailer freeing up valuable space inside

      2) Caulking is the best, here is the link to my article that includes the best caulking to use

      3) Your boler is right at the changeover year for door locks, from 1968 to 1974 a “L” handle utility latch was used, from 1975 to 1988 a Bargman L400 door lock was used. I have replacement kits for both types, when you click on the kits there are pictures of the lock that kit replaces in the descriptions
      Hope this helps

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