fiberglass advice???? - Fiberglass RV

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Old 07-14-2006, 10:19 AM   #1
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Trailer: Surfside 1978
Posts: 12

I'm going to try fiberglassing for the first time this weekend. I need to extend the opening on my windows to make them smaller to fit my windows properly. I only need to extend the opening about approx. 1-2cm. i don't know alot about fg repair, but i'm assuming it's kind of like paper mache. I have to cut the strips of fg mat to fit the area and use makybe a light piece of wood, covered with aluminum foil as a backer and somehow get it to hold in place as i work. i cover my area. what i'd like to know is:

1. the mixing of the resin. how do i measure it to mix? for example, i think the package says, add 2 oz of the stuff in the can and 14 drops of hardener. well, how do i measure 2 oz. sorry for such a dumb question. do i use a measuring cup? i know i shoudl use old marg. containers for mixing and popsicle sticks.

2. how many layers of fg mat do you think i need to apply in order to get the thickness of the cabin? do i just apply one layer of fg mat then continually add the others or do i have to wait for that first layer to dry?

3. i'm thinking of just using a paint brush, (the kind that kids use in elementary school) to apply the resin. will that dissolve?

4. do i dip the fg mat in the resin then put it on the backerboard, or do i put the fg mat on the backer board and then dip my brush in the resin then apply it to the fg mat? is one way better than the other?

5. since all my work will be hidden by the clamping ring in the interior, it doens't have to look pretty. however what if i make a mistake. do i just saw off the mistake, or sandpaper it away?

6. i have taken out all four windows in my trailer. i want to get all this done this weekend and try to reinstall the windows as well. is there a certain amount of time that you have to let the fg set before sawing or sandpapering it or drilling through it for that matter?

7. should i wear a mask. i'll be doing this outside. is there a specific temp. that you shouldnt' be working in or the fg won't set?

Those are some of my questions above. If you have any words of advice for a first time fiberglasser i would greatly appreciate it.

Thanks to everyone.

brenjean is offline   Reply With Quote
Old 07-14-2006, 02:13 PM   #2
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Trailer: No Trailer Yet
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Laying Fiberglass isn't too hard
Check this link, that was approx 12 below yours, some really great advice


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Old 07-14-2006, 02:51 PM   #3
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I also found this site on the net

Good Luck
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Old 07-14-2006, 03:56 PM   #4
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I'll just fling in things that come to mind on each of your questions.

1. You need to mix reasonably accurately, but with (regular) polyester resins you don't need to be exact. You could pour a measured amount of water into your margarine tub and use that to put a mark on the outside of the tub. Then dry the tub - if you get water anywhere near the resin, it will stop it setting! Popsicle sticks ("non-sterile tongue depressors") are what the pros use to mix!

As soon as you're thoroughly mixed the catalyst into the resin, pour it into a bigger container - more surface area means it won't heat up so fast, so it won't set so quickly. The ideal for this on small jobs is a paint roller tray - the resin pools in one end and the sloping bit gives you somewhere to put your sticky brush down. Once any unused resin has set, you can bang it out of the tray and re-use it.

2. Number of layers depends on the glass you are using. Around 5 oz/ft2 of glass mat sounds about right - say 3 layers if you're using 1.5 oz/ft2 mat. You can apply this thickness, but not much more, in one work session. Apply each layer individually. Overlap the new glass at least 5cm onto the old glass.

3. Applying by paint brush is ideal for small jobs like this. Remember that you want to use a 'stippling' (or stabbing) action to wet out the glass - too much brushing risks pulling it all apart. You won't know if a brush falls apart in resin until you try to use it, so a test run first would be a good idea - actually doing a complete test run of the whole process away from your trailer is an even better idea!

Decide whether you will (1) use disposable brushes and throw them away or (2) wash the brushes in expensive solvent (paint thinners will do, but acetone is better) and re-use them - it depends what you pay for brushes and solvent as to which is cheaper. Washing brushes inadequately in expensive solvent and then having to throw them away is the worst option of all, OK? Have spare brushes to hand - you will get caught out at some point by the resin setting while you're still working with it - stopping work and throwing away unused resin (and the solid brush) is the only solution at this point, you cannot stop the resin setting!

4. Plan A (conventional): Paint resin onto the job, lay a strip of glass onto the resin and stipple it with the brush, so the resin wets through the glass. Add more resin if needed - you're aiming to just wet out the glass, with no dry strands left, but not to add any more resin than is needed to do this. More resin than the minimum needed is not better, it's worse - but it will take practice, so you'll probably put too much resin on to start with.

Plan B: Lightly wet out a strip in the 'dry' end of your roller tray. You've then got about a minute (before the glass mat starts to disintegrate) to lightly coat the job with resin, pick up the soggy glass and stipple it in place.

5. Mistakes can be sawn off or sanded away (wear dust mask for either) - but sanding isn't easy, until you put a sanding disc in your angle grinder (the laminator's friend....). Think again about doing a practice run off the job. You wouldn't recommend anyone to pick up a saw for the first time to trim an expensive bookcase, and fiberglassing is no different.

6. Leave sanding, sawing, drilling until the next day - it can be done sooner, but the fiberglass will not be as hard and will clog tools badly.

7. The only mask that will protect you while laminating (not sanding) is an inorganic vapour mask - anything else, like a dust mask, is completely pointless. Polyester laminators who are not forced to wear masks generally don't wear them. Personally, I use a vapour mask when working indoors, but not outdoors or a garage with the door open. Don't get scared of the materials - for example, polyester resin isn't anything like as dangerous as used engine oil. Don't laminate below 5C/40F. Above 20C/70F, start reducing the proportion of catalyst or the resin will set too quickly to allow you to get the job done.

Them's me random thoughts- I hope it helps, and: Have Fun!

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Old 07-14-2006, 09:27 PM   #5
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Trailer: 1988 Bigfoot 5th Wheel Deluxe
Posts: 148
My husband and I just had our first experience with fiberglassing while repairing a Scamp floor. He mixed the resin while I cut the fiberglass matting to fit, painted resin on the location, placed the matting, then dabbed resin on top of the matting. We were able to work fairly quick with this method. We used several disposable brushes and gloves. If you do any overhead work an old shower cap is recommended. Also don't mix more than the 2 oz. because you won't have time to apply the resin before it begins to set.

We had 2 kinds of matting we experimented with. One was the loosely woven thin kind and the other was thicker strands woven into squares. Personally I preferred the squares because it held its shape better while the resin was applied. The loosely woven was thinner and the strands were hard to keep in place. We found both kinds at Lowes.

After it dried I used a Dremel saw blade to trim the excess fiberglass. Wear eye protection and a mask for this. All in all we are pleased with the results for our first attempt. It is not hard to do but you need to be organized before you begin.

Good luck on your project.
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Old 07-17-2006, 01:55 PM   #6
Trailer: Surfside TM14 1978
Posts: 49
Another good book called 'canoecraft' is available and popular at many popular libraries. It has a great section on fibreglassing.
re: measuring the catalyst and resin. I find that when I buy 1 litre of resin it comes with the right amount of catalyst. I pour 1/4 of the litre into a margerine dish, then add 1/4 of the catalyst. Then mix with a paint stir stick. I then place the cloth where I want it and paint the resin onto the cloth. This method seems to always get a reasonable sized batch for me that works well.
Let the remaining resin, stir sticks, etc set before you throw it in the garbage.
Don't forget disposible gloves.
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Old 07-17-2006, 08:34 PM   #7
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Trailer: 1985 17 ft Burro
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I replaced my entire floor and had to fiberglass it to the shell. The fiberglass company that I bartered with allowed me to help laminate to the shell. This is what we did when filling in a large space with many sharp angles...

Fiberglass Mat: Tear several pieces of fiberglass mat to be relatively same width and length.

Butter: Mix resin with hardener in recycle #5 plastic cup (we have a squeeze bottle with little measuring cup on top for hardener). Add cotton fibers to make a paste, not too runny, not too thick.

Resin: Mix resin with hardener in another cup.

Pizza: Take a piece of cardboard and layout fiberglass mat and wet it down with brush and fiberglass resin. Lay another layer on top of that and wet it down. Don't get too sloppy wet, just enough to get all layers moist. We did three layers.

Butter the area, smooshing in the crevices because fiberglass strands do not like to bend sharp corners. Take the cardboard pizza and grab fiberglass mat under first layer with gloved hand. Lay this down on your buttered area. Pat down with hand first, then stipple with brush, and roll out with special plastic roller. You are trying to get out all of the air so the fiberglass mat and resin become one with the wood or the area you are covering.

Side notes: The time you have to work with the above butter, pizza and resin depends on how much hardener, or activator you add to resin. I usually plan on about 15 minutes. This process works best if one person is mixing butter, resin, and making pizzas while the other is laying out butter, pizzas, and smoothing fiberglass mat down.

Do not mix resin in cheap drink cups (red or blue beer cups) these will melt instantly (don't ask how I know this). The bottom of a milk jug and ziplock reusable containers are good cheap mixing containers. Round containers work best, because once resin hardens you can roll them a bit and the resin breaks off...viola good to use again.

Sanding and grinding is probably the most hazardous part of the job. Wear good eye protection, a good respirator, and cover your entire body. Don't allow other people or pets near the area. If you get any dust on your body (you will) take a cold shower. A warm shower will open your pores and allow the minute strands to enter into your skin even deeper. I wear a painter's suit and work gloves. I duct tape the arms tight to the gloves. Somehow dust strands enter in and work their way into my forearms. The result is a couple of days of itty bitty slivers, making sleeping uncomfortable. If you feel slivers, put duct tape on the area and pull off. This will eliminate some of the slivers but not all.

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