You Can Repair Fiberglass

[Cmtravels]

Caroline, this was our first foray in fiberglass too, but this group has been great with advice! The one thing we learned yesterday is that not all fiberglass mat is created equal. Bought the first batch at West Marine and went down beautiful. . Second batch was from Home Depot and was a bear. Not sure if it was a bad batch or what. Also wish we had bought the gallon of epoxy first. Have fun!


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[caroline3583]

Well, I've been informed I have a "stickie"...but the repairs apply to both? Called Itasca, and they told me the skin of my roof is 1/16" thick, so I will have a hump afterwards. I cannot get to the backside of the hole. I will have to wait to post any pics, as it's pouring here in Scottsdale, but the Gorilla tape I put on 6 months ago is still holding up. Ace hardware carries mat and resin, but epoxy??

[Andrew Gibbens]

Originally Posted by Cmtravels

What is the best way to join the two pieces together?

I'm a bit late to this party but there may be some tricks to pass on. Limiting the 'repair' you have to do is the real challenge on a job like this and most instructions assume you have a friendly angel who will hold the piece in place while the resin hardens! Here is my suggestion - the drawing's a bit technical, but it's meant to be a slice through the joint between the old and the new at any point.

Steps are:

1. Cut the filler piece to the shape of the hole (that makes the repair as small as possible), or vice versa if easier. Taper the inside of the cut edges as much as possible - a 1 to 10 slope would be perfect, but the 1 to 3 taper shown will do. Rub down the inner surface of the filler piece and original shell with something like 80 grit sandpaper for several inches back from the joint.

2. To hold the filler piece in place until laminated, drill holes through the middle of the joint and fit small bolts with penny washers to keep the two surfaces exactly flush with each other. Do this with care as every misalignment will show later. Two or three bolts along each side should do, but more may be needed. Before installing them, coat the bolts and washers in wax to make it easier to get them out if resin gets on them. You can apply packaging tape across the outside of the joint between the bolts to stop any resin leaks - this is helpful if you haven't cut the two pieces perfectly the same.

3. Lay thin strips of fibreglass mat or tape along the vee of the joint, between the bolts. Let these harden and they should be enough to hold the filler piece in place, allowing the bolts to be removed. Do not be tempted to leave the bolts or nuts in place, as that6 will cause much more work later.

4. Finish laying up fibreglass mat or tape to more than the thickness of the original shell and overlapping the repair on the two sides - onto the areas that you sandpapered before.

5. You are now left with a small 'repair' to do along the joint on the outside to make it cosmetically acceptable. A little grinding out and adding bondo may be needed to get a smooth surface to finish. Never be tempted to widen the area that needs cosmetic repair as that makes more work to do.

In case it's not obvious, this technique can only be done from the inside - well, it could be done from the outside but then the cosmetic repair afterwards would be a huge problem.

[Cmtravels]

Thanks! We kinda' did the same thing. The back of our camper looks like buck shot so we used holes that were already in the camper to brace the two pieces together with lauan. We got the inside complete. Waiting for decent FG mat from Amazon and I'll start on the outside.
First photo is the bracing.
Second is after on the inside. This was the bad FB mat we used. It came out opaque and not translucent like the first batch from West? But cured and seems strong.
Third is after the bracing was off. An auto body repair shop will not be hiring us in the future but not too bad for newbies!




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[Andy Sigmund]

Help: I have a lot of screw holes in the UHaul I just bought. What is the best way to fill these? Can I use epoxy putty? Is there a tube of something made for this?
Thanks. Andy

[Davie B]

I have a different kind of repair problem. Our LiteHouse has what I think is a structural piece on the roof running the length of the trailer. The piece is attached to the roof with some sort of adhesive and pop rivets.

Backing the trailer into a space, I managed to hit a low hanging branch and cracked the end of of the structural piece. The part needing the repairs is hollow and has several angles.

I'm wondering if I should drill out the pop rivets and remove the piece to work on it, or repair it in place. Photos are attached of the crack. Any suggestions?I know that the roof is filthy.




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[BAMA & Pachyderm Posse]

looks like fiberglass ,what is under it ? if it is just another skin I would stuff it with cardboard and hand lay fiberglass cloth to about 1/4 inch then sand and paint

[Wado]

A bit off topic but what is the best way to cut a hole or make the window openings larger? Jigsaw, dremel? Any hints or tips on what to do and what not to do? How about drilling holes and not cracking the gel coat.
thanks

[RogerDat]

I claim no great experience but I do know an oscillating tool and a sharp (high quality) fine tooth blade cuts through the fiberglass tabbing on the wall floor joint well.

I used this one but the blades that come with it are not very good. bought some 180 degree curved and short straight blades a notch or two up in quality.
Variable Speed Oscillating Multifunction Power Tool

[sokhapkin]

I second for oscillating tool and 180 degree blade. Works like a charm.

[Jim Bennett]

I have all the tools mentioned for cutting fiberglass, and have used each one with success.

A good jigsaw, with a sharp blade, will work good, especially if you are doing a big cut. I used this when I put a large access hatch in.

The oscillating tools work great too, and I have used mine for smaller cuts. They are slower, but easy to control, and do a great job.

A Dremel tool too will work great for small work, with a good cutting blade. Slow, but nice cuts.

Which ever tool you use, first tape the cut line, and a few inches to the side, and make a good mark with a dark pen, so that once you get going, the line is easy to follow. If doing a lot of cutting, a vacuum to suck up the dust as you go would be helpful. Remember to wear a dust mask.

[rdickens]

If you use a jigsaw, there is a blade available (ACE Hardware), that cuts on the downstroke.

Most jigsaw blades cut on the upstroke, but I hear that might lift and splinter the finished
(i. e. the gelcoat) edge. You might be able to minimize the gelcoat edge damage by putting
blue "painter's tape" along the edged of the intended cut?

Ray


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[Jim Bennett]

Originally Posted by rdickens

If you use a jigsaw, there is a blade available (ACE Hardware), that cuts on the downstroke.

Most jigsaw blades cut on the upstroke, but I hear that might lift and splinter the finished
(i. e. the gelcoat) edge. You might be able to minimize the gelcoat edge damage by putting
blue "painter's tape" along the edged of the intended cut?

Ray

I have used those blades lots, especially on laminate counter tops, and they work quite well, and do leave a cleaner surface cut on materials that splinter harshly. You do however have to use a strong steady hand on the jigsaw, as the blade pushes away from the surface, and can bounce the saw out of the hole.

I did try to use one when doing my hatch, and abandoned it, as it really grabbed easy on the fibreglass, causing it to bounce the thin trailer shell quite a bit. Instead, I used a good sharp finer blade, and used sandpaper to nicely clean the edges. The wee bit of chipping you might get would only be an issue if you needed to leave an exposed edge you need a perfect finish on.

[rdickens]

Thanks, Jim!
Good to know! 😊

I may want to cut some access holes into some of the interior cabinets someday soon.
I had been wondering about Roto-zips, Dremels, vibrating tools jigsaws, etc.

Ray


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[Wado]

Looks like I just put several new tools on the wish list.
Wade

[Johnny M]

Originally Posted by D White

Hi…My name is Dave and I love FIBERGLASS. I have been working on show quality Corvettes for 35 years and I’m wondering if there is any useful information I have learned in that time that I could pass on to this great forum. We are currently reconfiguring a Uhaul for a client which promises to be quite a build in the steam punk genre. This Uhaul is in remarkably good condition, but requires lots of patching and fiberglass work. It will be a perfect subject for this forum.
First of all, I believe anyone can make a satisfactory fiberglass repair. It doesn’t require much for tools, or specialized anything. I will document some work in this thread done with basic understanding. Yes there are other ways, methods, tools etc. I encourage others with differing methods to start a thread with those ideas. The more information, the better. I don’t know everything, and use this information at your own risk.
I start off with safety. You MUST ALWAYS use the following safety items as a minimum.
Dust masks
Eye protection
Nitrile gloves or better
Long sleeve shirts or tyvek coveralls
I know there will be lots of reaction to the following statement, but don’t waste your money on epoxy. I love epoxy and use lots of it, but you don’t need anything but regular old polyester fiberglass resin. I have 35 year old repairs still looking good with it. We use vinlyester resin, for many reasons, but you don’t have to and it may be hard for you to get. “tooling” resin would be a step up also. The problem with epoxy is that is does stick better, but nothing sticks to it except epoxy unless strict procedures are followed. You don’t have the time or the money for it, and you don’t need it if you follow the following two rules EVERY time
1. YOU ARE WEARING SAFETY EQUIPMENT AREN’T YOU? You must have a clean surface. Before starting a repair, clean all foreign material off with a razor blade then wipe with acetone. You may now start sanding the repair area with at least 80 grit, (40 is even easier). Use a sander, or do it by hand, but sand the heck out of it. It MUST be rough. After sanding, again wipe all dust and debris off with acetone. IF IT’S CLEAN AND ROUGH, IT WILL STICK.
2. SAFELY cut your mat (don’t use weave (cloth), your trailer was made with mat. When you are ready, mix your resin according to the directions on the can in a body shop style plastic cup or an grocery store style paper bowl, NOTHING ELSE. No cottage cheese container, yogurt container, pop container, or any other thing. Plasticers from other receptacles can melt into the resin and cause you problems, and you won’t know why. Yes I know other people have done it, but don’t you. Paper cereal bowls are cheap and become better after the resin has cured in them. You are now ready to patch, depending on what repair you have. I will start off with small and if it is useful to the forum, we’ll move to more complicated. If you have fresh resin and catalyst, mix it correctly and follow the above, it will work…YOU CAN DO IT!
If I can figure out how to post pictures, we will have specific information in the next few days

Okay Dave, I have read through this forum hoping someone already asked my question but didn't see it here...love your threads/posts by the way...

I have some minor diy fiberglassing experience repairing a small boat so I am familiar with some of this already but picked up a lot of great information here...anyway, my wife and I are restoring to like new condition with some layout modifications to suite our needs of our 1971 boler which I have a separate thread on...the po installed an Doemetic roof A/C in place of an vent, cutting the vent bigger than needed and putting a 3'x3' piece of untreated plywood in between the ac and the fiberglass roof in 2012...needless to say the fiberglass thickness wasnt meant for the 75 lbs of ac unit. The wood had rotten & had some leaking so we removed the ac to discover the sagging roof...I am planning to reinforce the roof to support the a/c unit and had thought about wood support from the inside to handle the a/c but don't want to lower our headroom as I am 5'9" and already hit my head on the ac a couple of times before we removed it....

I was thinking of beefing up the roof by fiberglassing 2 to 3" ribs around the a/c hole (square) and a couple of reinforcing strips of fiberglass continuing down to each side wall from the front and back of the opening. I was thinking about 1/4" thickness minimum to maybe 3/8". I also thought of maybe incorporating some thin wood inside the ribs as like I saw in the cabinet left of the entrance door when cutting a wider opening to accommodate a refridgerator, and the wood appears to be about 1/8" thick...

Any ideas on this structural reinforcement of my roof to hold the ac?

[D White]

Originally Posted by Johnny M

Okay Dave, I have read through this forum hoping someone already asked my question but didn't see it here...love your threads/posts by the way...

I have some minor diy fiberglassing experience repairing a small boat so I am familiar with some of this already but picked up a lot of great information here...anyway, my wife and I are restoring to like new condition with some layout modifications to suite our needs of our 1971 boler which I have a separate thread on...the po installed an Doemetic roof A/C in place of an vent, cutting the vent bigger than needed and putting a 3'x3' piece of untreated plywood in between the ac and the fiberglass roof in 2012...needless to say the fiberglass thickness wasnt meant for the 75 lbs of ac unit. The wood had rotten & had some leaking so we removed the ac to discover the sagging roof...I am planning to reinforce the roof to support the a/c unit and had thought about wood support from the inside to handle the a/c but don't want to lower our headroom as I am 5'9" and already hit my head on the ac a couple of times before we removed it....

I was thinking of beefing up the roof by fiberglassing 2 to 3" ribs around the a/c hole (square) and a couple of reinforcing strips of fiberglass continuing down to each side wall from the front and back of the opening. I was thinking about 1/4" thickness minimum to maybe 3/8". I also thought of maybe incorporating some thin wood inside the ribs as like I saw in the cabinet left of the entrance door when cutting a wider opening to accommodate a refridgerator, and the wood appears to be about 1/8" thick...

Any ideas on this structural reinforcement of my roof to hold the ac?

This is a great question, but I will need to see pictures.....Fiberglass Dave

[Johnny M]

Originally Posted by D White

This is a great question, but I will need to see pictures.....Fiberglass Dave

Hey Dave, thanks for the reply...Here is the only picture I have at the moment of the roof area, the roof was sagging a little when I removed the ac and plywood allowing water to pool up slightly rather than run off.

My thoughts were to fiberglass mat strips to the inside making a square around this area one layer at a time and continue the rear side and tongue side of the square area across to the sides of the trailer and have them blend in to where the sides meet the roof so it looks like it was molded that way when done.

I planned to accomplish this by putting slight pressure on the roof from the inside using temporary vertical wood supports & c clamps to shape the roof back to the dome shape eliminating the sagging and fiberglassing until I have enough mat in place to support the roof for the a/c weight. The other reason for the extra support is that I also would rather remount the a/c without the plywood.

As I said in previous post I thought about adding some wood strips to the fiberglass layers to add more strength or do you think that is not necessary?

[Borrego Dave]

I've done a lot of FG work but am no expert although you do find 1/8" luan ply glassed in between many spots of a FG build for strength. I don't think just that or strips would give you enough support for an AC unit...could be wrong on that. Might be the PO had the right idea and just didn't go far enough for a good mod. Possibly glassing in 1/4 or 3/8ths ply to the roof side to side would give you enough to carry the load without any distortion to the shell and still keep the interior clearance you have. The roof line would be a bit different but if it works for you.....Anyway, just my 2 cents for you and worth both pennies .

[D White]

Originally Posted by Johnny M

Hey Dave, thanks for the reply...Here is the only picture I have at the moment of the roof area, the roof was sagging a little when I removed the ac and plywood allowing water to pool up slightly rather than run off.

My thoughts were to fiberglass mat strips to the inside making a square around this area one layer at a time and continue the rear side and tongue side of the square area across to the sides of the trailer and have them blend in to where the sides meet the roof so it looks like it was molded that way when done.

I planned to accomplish this by putting slight pressure on the roof from the inside using temporary vertical wood supports & c clamps to shape the roof back to the dome shape eliminating the sagging and fiberglassing until I have enough mat in place to support the roof for the a/c weight. The other reason for the extra support is that I also would rather remount the a/c without the plywood.

As I said in previous post I thought about adding some wood strips to the fiberglass layers to add more strength or do you think that is not necessary?

I went out to the lot and took a really good look at a customer's Boler we have waiting for a redo. I do not see a way to use an air conditioner
in this instance. I would advise against it. If you feel you must and the plywood was working, you could fill the low spot with fiberglass and enclose some plywood on all sides with fiberglass to replace the rotted piece and put it back the way it was. I feel weight is too much....sorry I couldn't help and of course, this is just one opinion, others may have an idea for you
Fiberglass Dave