Teardrops n Tiny Travel Trailers

I been getting a crash coarse in fiberglass . What are you doing putting resin on wood. If so why not use the mixs?

slowcowboy wrote:hey guys .Slow here. I am glassing just a door. 36 inches by 30 inches...........can I get away with no cloth to glass it? any thoughts or feed back?

I am getting back at the kampmaster again. and gave up on finsh in a week thingy. slowcowboy.

I'd use glass with resin. For just a clear finish on wood, either a spar varnish or exterior poly. Resin alone won't move with the wood and will eventually fail.

spar urethane and mineral spirits go to top of page put mix in search pick what will work for you
bondo is not glassing it will fall out after wood gets wet a few times

Slow, what are you trying to achieve? Are you just trying to smooth out some low or rough spots, or are you trying to weatherproof?

What is the door made of and what do you plan to do for the final finish?

Bondo is a polyester resin with filler fibers already added. It is not compatible with most of the foam insulation that we use and some things don't like to stick to it. It will absorb moisture if not sealed by additional stages of finish (sealer/primer coat, top coat).

Straight epoxy (resin + hardener) won't add much strength by itself and probably won't keep wood from checking and cracking later; and it doesn't make a good fairing compound all by itself (although you can buy pre-thickened epoxy resins know as epoxy fairing compounds). It does make a pretty good sealer, but is generally not UV resistant, so needs to be prepared and painted or covered in varnish after curing. The first prep stage after curing is to wash it off with water using a green scrubby pad and paper towels. The chemical reaction causes a waxy substance called amine to "bloom" to the surface, and you don't want to spread this around with your sandpaper, etc., or the next thing you do might fail to stick.

If you add fillers (chopped glass fibers, micro balloons, cabosil, etc... available separately) to epoxy it can act a lot like (even just like) Bondo, but won't eat the foam. Depending on the filler used, it may or may not absorb moisture, but most systems call for a couple of "barrier coats" of "neat" (unthickened) epoxy as a sealer coat to seal up any porosity from sanding into the fillers.

If you are wanting to add strength and puncture resistance to the door panel, then glass cloth, or weave, should be used. As I understand it glass mat (with chunky random laid fibers) should only be used with polyester or vinylester resins because the binders used to hold the mat fibers together (and in some types of glass cloth) are not compatible with epoxy; so always tell your sales person which system you are using at the time of purchase, just to be sure.

Unlike Bondo, epoxies have to be mixed at fairly exact ratios, so if you plan to do very much of it there is the added expense of the metering pumps and/or a digital scale (I use both for every batch as a double check).

And here is the big thing, Personal Protective Equipment (PPE). If you plan to handle, use, cleanup and/or sand any of these chemicals you must know how to properly use a carbon filter style cartridge respirator (not just a dust mask), wear disposable rubber gloves and sleeves, and wear at least safety glasses with side shields.

Soooo, to answer your question, no, you can not glass a door if you don't use any glass.

To be honest, doing fiberglass properly can be quite complicated. I've been working with it for a while now and am still not sure that I am using the optimum methods.

Let's recap some terminology as I understand it:
Bondo - brand name 2 part thermo-setting Polyester fairing compound.
Epoxy - 2 part thermo-setting plastic adhesive containing epoxides.
Resin - can refer to the resin part of a 2 part system, but is sometimes used to refer to a mixture of resin and hardener; sometimes used specifically to denote polyester resin as opposed to epoxy.
Neat epoxy - epoxy resin mixed with hardener and nothing else added; sometimes also just referred to as epoxy,
Epoxy/glass - glass cloth laminated with epoxy. Sometimes referred to as a layup. The process of doing a layup may also include the term "wetting out" the glass.
Thickened epoxy (or just "Thick") - neat epoxy mixed with fillers to provide structural strength for joining and/or so it will hold on to vertical or overhead surfaces; or as a fairing compound (certain fillers can be used to make fairing compounds lighter in weight and easier to sand). Some fillers do some tasks better than others (fairing vs. structural bonding); some do okay at either task.
Composite - anything that is made up of two or more materials that when combined result in something that is more useful or stronger than the sum of the parts. Epoxy isn't that strong in tension and can become brittle by itself. Glass cloth is very strong in tension but is floppy and limp. Together they are much more useful.

KC covered it pretty well (as usual) so I'll just add a bit about polyester resins, which is what I think you were looking at (?)

As mentioned, the "can of Bondo with the tube of hardener in the auto section" is body putty used for finishing. If you just want to seal the wood on the door, you can use polyester resin on its own, but resins are normally pretty brittle - that's why we add the cloth to the recipe.

If you do want to 'flood coat' the wood to seal it, you can use some waxed resin and thin it down 10% with lacquer thinner, acetone, or styrene so it soaks into the wood better. It will also need to be painted to keep the UV off it.

That said, on the shelf right next to the can of Bondo should be a "fiberglass repair kit", which should have resin and cloth in a kit large enough to do a door. The area it covers is given on the packaging.

A big +1 on the PPE: styrene is nasty stuff. Maybe going a little off topic here but I ran across this a while ago and I've been looking for an excuse to share it...

The styrene industry has invested many years of effort, and nearly $12 million in funding state-of-the-art independent research, to develop the most thorough and accurate information about possible cancer effects resulting from styrene exposure. The results of extensive health studies of workers in styrene-related industries collectively show that exposure to styrene does not increase the risk of developing cancer, or any other health effect.

And from an (albeit conservative) MSDS:

Potential Acute Health Effects:
Very hazardous in case of eye contact (irritant). Hazardous in case of skin contact (irritant, permeator), of ingestion, of
inhalation. Inflammation of the eye is characterized by redness, watering, and itching.
Potential Chronic Health Effects: CARCINOGENIC EFFECTS: Classified + (PROVEN) by OSHA. Classified 2B (Possible for human.) by IARC.
The substance is toxic to the nervous system, upper respiratory tract. Repeated or prolonged exposure to the substance can produce target organs damage.

I've done 4 tears with just epoxy resin on the doors, no cloth. Thing is, you need to do multiple layers of epoxy. 1 or 2 won't do it. I usually put on like 6 or 7 coats with sanding between coats so that it flattens out well for paint. Make sure that the edges are sealed as well, as that's the most important part. Once painted, you shouldn't be able to see ANY signs of veneer in the edge. Think of it as a thick plastic coating you are applying. And, it takes time. Cloth on a flat piece of ply isn't going to do anything for it, unless you plan on beating it and need it for the abrasion resistance but I'm sure I'll hear some feedback on that statement. Doug

doug hodder wrote:I've done 4 tears with just epoxy resin on the doors, no cloth. Thing is, you need to do multiple layers of epoxy. 1 or 2 won't do it. I usually put on like 6 or 7 coats with sanding between coats so that it flattens out well for paint. Make sure that the edges are sealed as well, as that's the most important part. Once painted, you shouldn't be able to see ANY signs of veneer in the edge. Think of it as a thick plastic coating you are applying. And, it takes time. Cloth on a flat piece of ply isn't going to do anything for it, unless you plan on beating it and need it for the abrasion resistance but I'm sure I'll hear some feedback on that statement. Doug

Doug,

You have built many beautiful (and long lasting) campers!

I've tried to build my knowledge on this forum. Could you provide some details on your techniques? What type of epoxy and hardener do you use? Is the hardener "amine free"? How long of a cure do you allow between coats? Do you wash off amine blush between coats and how? What type and grit of sandpaper do you use?

Thank you for your contributions of your experiences.

Take care,
Tom


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I use West System, metered pumps and the 207 catalyst if it's going to be a woody. If it's going to be painted, you can use the 206, as the paint will be the UV inhibitor. Use the "official" rollers that West system has. The cheap ones from HD will break apart in the resin and leave chunks of roller in the finish. Cut a roller in 1/2 giving you 2 small rollers, cut one of those halves in 1/2 lengthwise and pinch it in a spring clamp to use for "backdragging" the finish. I use a small detail type roller, only like maybe 4" wide. Mix up your resin...I usually do something like 8 pumps of each, mix it well, wet out the roller and start rolling it on. Once I get an area coated out, I grab the piece in the spring clamp and backdrag the wet resin to smooth out the dimples caused by the roller. Once cured, I sand with something like a 220 to take off the high spots, scuff the entire thing with a scotchbright, then put on another coating. I let it completely cure between coats and sand, rather than pile on another coat prior to it's being completely cured. I've never had an amine blush using the West System materials. I do however have a dryer environment to work in than many of you and in the winter, the shop is heated with wood. I just build up 6-8 layers of the epoxy like described using the back dragging method to "tip off" the epoxy and make it lay flat. You're going to go through a load of rollers. On the last 3 layers I'll start to use a long flat board or my air file to flatten out the epoxy so that it doesn't show waves, much more important on a painted one than on a woodie. The clear depth on the finish on a woodie will hide the waviness that can be seen on a paintie. Check out the West System website as I think they have some videos and "how to's" that are informative. Doug

Thank you Doug!

Just wondering how much epoxy you need for an average tear?

That depends on just how flat you want the surface, and what condition it is prior to applying any epoxy, or if it's a woody type of finish, or if it is going to have glass over it. It's going to take more to get it real flat if that's what you are going for, as you are sanding much of it off with each layer you build up with. Using West System...I buy a 1 gallon can of resin and an appropriate sized can of catalyst. I've never used a full gallon of it on a tear. I don't apply cloth on mine...cloth will soak up more product. Thing is, take your time and do it correctly. I've seen lots of people do a hurry up job and then ask why it isn't nice and flat when they put the paint on it. Paint or clear coat won't hide anything. Your final finish is only as good as the prep work that went into the substrate. Doug

I will add that if you are going to do 8-pump batches, as Doug suggested, then you want to pour that batch into a paint roller tray (or pour and spread it directly onto your work) pretty quickly after mixing. This will slow the heat reaction down and maintain the advertised working times. If you leave a large mass like that in a cup it will heat up pretty good and kick off a lot quicker.

I don't use pumps for epoxy resin, I use either volume or weight measurements. After having to scrape off uncured epoxy because of a defective pump, I trust the scale. This is easier with a 2:1 resin than with a 5:1.

I use the pumps to get the liquid into the mixing cup so that I can weight it on the scale. It is a lot cleaner, more controlled and there is no waste dribbling from a pour that would need to be wiped up. I almost always have to adjust the amounts, at least a little. But then again the digital scale I'm using increments in 0.05oz steps and I always try for exact.

In about 4 gallons of use, usually mixing less than 3oz at a time, I've only had one small area not cure properly, and I think that was due to too cold of an ambient temperature never letting the exothermic reaction begin. Had to scrape that one off.