Can anyone tell me if roof on 1995 320 SE is made of GRP fiberglass or just ordinary fiberglass? I have to do a repair and I know polyester will not stick to GRP. Was wondering if anyone could give some advice. Travelling to Texas to get fixed is not an option. I have coach in BC Canada at the moment and wont be going south until December.
Thanks
Bob
Bob,
Welcome to the ForeForum.
Tell us what size/kind of repair is needed.
Picture would even be better.
I repaired a crack in the roof on my 1996 U320 with Marine-Tex which is available at The Plastic Shop in Victoria, where I live.
Use the white which is very close to the roof colour.
I repaired a 20 sq. ft. area of the roof with fiberglass off the shelf at Home Depot. Both mat and cloth.
Bobiv, GRP just means glass reinforced fiberglass, it can be done with polyester resin or epoxy. In the case of Foretravels, original construction was polyester, and can be repaired with same. Maybe someone can give you an idea of what reinforcing materials were used in layup of roof.
Here's a link to a materials supplier, click on learning center for everything you want to know about fiberglass.
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I dont know if it makes a difference but have since found out it is called FRP
FRP (Fiberglass Reinforced Plastic) and GRP (Glass Reinforced Plastic) are variations on the same thing. They can be bought in giant continuous 10' wide roll or by the foot and in sheets of various sizes. The roofing material (as well as the sides) are laid up fiberglass. In the case of the roof, laid over ⅜" marine plywood. The only place, as far as I know, that Foretravel used the FRP or GRP sheet goods is for the bottom skin, the the floor, and the partitions of the basement. Also, at least on our coach, behind the wood paneling on the inside of the outside walls. According to Rance, at Xtreme Paint and Graphics (and formerly a Foretravel employee), Foretravel used polyester resin.
Attached see two pictures; One is a wall 4" diameter plug that that I drilled when putting in a dryer vent. The picture shows the sidewall construction from left to right: outside to inside. Note the FRP material next to the ¼" interior wall paneling. The other picture is of the fridge vent opening when I was replacing the vent and installing a marine fridge.
Don
Bob,
Not sure what kind of repair you need to make, such as a crack, hole, delamination, etc. The roof is first a layer of gel coat, then some fiberglass reinforced polyester plastic, bonded to a 3/8" thick plywood panel. Next you will find some foam insulation in between square aluminum framing. On the ceiling side is another layer of wood and thin plastic. This is normally done upside down in a mold that has been treated with a release agent like a wax. First the gel coat is sprayed on then the FRP (usually with a chopper gun, a tool that chops the fiberglass into short strands and sprays the plastic resin together) is applied (could also be fiberglass mat which is slower, but gives a more even thickness}. If you have a crack and it has been there for awhile it is possible the plywood is rotten in which case that needs to be replaced. Normal procedure for a crack is to carefully grind away the area around the crack with a disk sander to create a feather edge at the crack, Then you can apply fiberglass mat and resin to build it back to original thickness. Sand to get it smooth and level with the original roofing. Apply gel coat and repeat the sanding process. In order to get the gel coat smooth and shiny you have to sand through all the grits up thru 2000 grit. Polyester resin is probably what you should use as it will stick to polyester, but not epoxy. Epoxy resin is stronger and will stick to polyester and itself. What I have said is just a start. Consult a book on polyester fiberglass repairs.
Since you are in British Columbia, there are probably some boat yards that will have experience doing fiberglass repairs and may be able to do the repair in case you think this might be a difficult job.
I repaired a 4'x5' hole in the roof from a refrigerator fire.
I cut out the area, laid in a plywood panel, coated the panel with fiberglass then put a piece of fiberglass panel (bought at Menards in 4'x8' sheet.) over the fiber-glassed wood panel ( used 3m 5200). This brought the height of the roof about even with the original roof.
I laid fiberglass around the edges of the fiberglass panel, and blended by sanding, then coated the entire area with gel coat.
Turned out ok.
Its strong, and looks good enough for the roof, now covered with solar panels, I will probably paint the entire roof later this fall.
I have a spongy area around the bathroom sky light, I will cut that out and do the same repair.
Thanks for all the replies. I have since talked to Foretravel and they tell me the top layer on the roof was built with FRP. The plywood underneath looks brand new. So as Im told Polyester wont make a chemical bond to FRP only whatever mechanical bond you can create. Sounds like Ill have to use epoxy and go from there.
FRP is fiberglass reinforced plastic, aka "fiberglass." It ca be preformed into sheets, or job formed by saturating fiber reinforcements with resin.
I assure you Polyester will bond to FRP made with polyester resin, which is what Foretravel uses.
Did Foretravel tell you polyester resin won't bond to the roof structure? While it's true you're trying to achieve a secondary bond, rather than laying up your materials in a virgin layup which would require you to go back in time to when the motorhome was being built, it is entirely doable. If not, it would be impossible to repair any body damage on these coaches. Just need to follow good practices in preparation.