Oh gurus of Fiberglass/Epoxy I need advice

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Oh gurus of Fiberglass/Epoxy I need advice

Postby cubby_1969 » Thu Mar 16, 2006 9:13 am

I'm nearing the skinning phase of my teardrop and I'm deciding on how best to cover it. Due to cost and that I just don't think my style TD would look good in Aluminum, I have decided that I would seal and paint it. Here is my plan and you guys can tell me if I'm barking up the right tree.

My walls and roof are 1/2" ply so I don't need the strength or added cost of fiberglass. I planned on using auto body Bondo to fill my wood grain, screws, and any other imperfection, sand it all smooth, then coat with epoxy. A friend gave me a gallon of Evercoat Boat Yard Polyester Resin with Styrene. It is already thixed and waxed according to the label. I plan to coat the whole outer skin with this and then prime and paint with automotive paint. The paint would give me the UV protection I need, and the epoxy would give me the waterproofing I need. It would also be a lot cheaper and lighter without the embedded cloth.

Let me know what you think. :worship:

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Postby mbader » Thu Mar 16, 2006 9:55 am

Check the compatability of the sealer and the automotive paint.
I tried Serman-Williams automotive clear coat over Smiths epoxy sealer and it all bubbled up and I had to sand it off and start over.
So test on a small piece or better yet use all products from one supplier.

As you pull a trailer it's going to flex some. The paint might crack at the corners and joints.
The fiberglass cloth might pervent it but that's a lot of work for a maybe.
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Postby davel » Thu Mar 16, 2006 10:42 am

mbadr said:
As you pull a trailer it's going to flex some. The paint might crack at the corners and joints.
The fiberglass cloth might pervent it but that's a lot of work for a maybe.


As mbader said it is going to flex. We just finished resanding and resealing the edges and joints because of this flexing. Just a simple fiberglass tape seems to tie these joints together. It's a lot easier to do it in the first place than to go back and redo it.
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Postby cubby_1969 » Thu Mar 16, 2006 10:53 am

Taping the edges would be easy enough. I just don't want to have to buy the large peices of cloth.

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Postby Chuck Craven » Thu Mar 16, 2006 2:25 pm

Quote"
A friend gave me a gallon of Evercoat Boat Yard Polyester Resin with Styrene. It is already thixed and waxed according to the label. I plan to coat the whole outer skin with this and then prime and paint with automotive paint. The paint would give me the UV protection I need, and the epoxy would give me the waterproofing I need. It would also be a lot cheaper and lighter without the embedded cloth. " :thumbdown:


Polyester Resin does not stick to plywood very good, should use epoxy.
Polyester Resin is for repairing fiber glass boats.

If you are going to paint it, take a look at Rot-doctor as the sealer.
They have a bottom paint too. See the Baha Benroy links. Rot-doctor is in
the Rich's List.

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Re: Oh gurus of Fiberglass/Epoxy I need advice

Postby angib » Thu Mar 16, 2006 3:23 pm

cubby_1969 wrote:A friend gave me a gallon of Evercoat Boat Yard Polyester Resin with Styrene. It is already thixed and waxed according to the label. I plan to coat the whole outer skin with this and then prime and paint with automotive paint.

Duane,

This sounds like a sensible plan to me.

As that is polyester resin, not epoxy resin, it doesn't need any UV protection - sure it'll fade over 20 years (as will paint), but it won't break down. If this resin has already been 'waxed', that suggests that it is a gel coat resin, intended to be the exterior layer of a fiberglass moulding (the wax is needed to make the resin cure in air). You could just add some pigment and use that as your final coat, though it wouldn't be terribly smooth - but then you'll have to sand it smooth anyway, if you're going to put automotive paint on top.

The suggestion to tape the corners makes sense and it only needs to be fairly light tape (sorry, can't suggest a weight as we use metric!). Be sure to radius the corners a bit (1/4" is enough) before applying the tape as otherwise the tape will have a void at the corner.

If the resin has been 'waxed' remember to sand it plenty between layers - that wax would stop subsequent layers from bonding fully. A wipe-over with thinners or acetone is the best preparation for another coat.

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Postby angib » Thu Mar 16, 2006 3:30 pm

Chuck Craven wrote:Polyester Resin does not stick to plywood very good, should use epoxy.

Chuck,

I'll rephrase something I said to Mike: Please keep quiet about polyester resin not sticking to plywood very good, as there are thousands of plywood boats held together only with glass tape and polyester resin. They currently sail round the world quite happily, but they may all sink if the polyester resin finds about about this problem and loses self-confidence......

It is certainly true that epoxy sticks better to plywood than polyester. Indeed, epoxy sticks better to plywood than the plywood sticks to itself, so you could argue that it's overkill in this application.

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Postby cubby_1969 » Thu Mar 16, 2006 3:41 pm

The can does state it's for wood, metal, or fiberglass. I mainly want it to seal the wood not for strength.

I had thought about adding pigment and skipping the auto paint, but I want a finish that looks good close up as well as from the next campsite. I'll be filling the woodgrain so it doesn't look like painted plywood. Add some alluminum angle over the corners, and a nice peice of diamond plate at the front to catch the rocks and I think it'll look good. 8)

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Postby Chuck Craven » Thu Mar 16, 2006 4:12 pm

Well I have talked to several suppliers of Epoxy and Polyester resin and was told not to use Polyester resin, as it will not soak in to the wood fibers deep enough. I built a cover for my pickup truck many years ago with Polyester resin. I did not do a good job of finish sanding before painting and the paint came off with in the first winter. In spring the fiberglass cloth and Polyester resin pealed off the wood. I call that a failure! I redid it with Epoxy and it held up for 5 years after with no problems. I have talked to several boat builders here and they do not recommend using Polyester resin. So by my research Polyester resin may or may not give one good results. With Epoxy an armature should get better results. I am sure that boat builders with vast experience in using polyester resin can get excellent results. But I am not a boat builder and have no intent to sail a teardrop across Lake Michigan. I just don’t want to have to redo my hard work because I didn’t listen to others advice. Advice is advice one can take it or leave it. If one asks for advice and one has something to give, it has to be taken only in the content of that persons experience and limited knowledge. But to tell someone he is flat wrong shows immaturity.
I am sorry that I may have ruffled your salty scales, but I can only go by my experience.

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Postby cubby_1969 » Thu Mar 16, 2006 4:49 pm

Well, don't worry. I'm listening to everybody, then I'll do the research before jumping in. I could still end up a totally different direction. That's why I asked. I don't want to spend a ton of time only to have to redo it in a year. I want to hear all sides pros and cons about my idea. You guys have done this before, I haven't.

Keep the ideas coming.

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Postby Chuck Craven » Thu Mar 16, 2006 5:42 pm

Cubby
That is what is grate about this forum. You can get advice from people that have first hand experience and from engineers that have the number crunching knowledge and those that have done it. It is some time overwhelming but that is the nature of any research / project. I have 40 years experience in working in the electronics industry. From 50 megawatt transmitters, 300 + ft antenna structures, antennas, electronic test instrumentation, to utility trailers and to customizing vans. As well as being a machinist for the last 40 years. I am still learning every day. I have seen some real good designing being done by the people on this form. Don’t ever get dishearten and give up. Even if you make a mistake there is always a fix or an alternative option. Using your head and your hands is a skill that makes life fun and rewarding. It’s mistakes that will get you the skills / education to your reward. Happy tear dropping! :applause:
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Postby Mitheral » Thu Mar 16, 2006 8:22 pm

Polyester is more than sufficient for our purposes. Epoxy is less water permable and will stick to oily woods like teak better but for regular plywood as a sealer polyester is fine. Epoxy is also 2-3 times as expensive (or infintely more considering you got some polyester for free).

Like angib said thousands of plywood and solid wood boats have been constructed using polyester resin. Many have been in service for dozens of years. And your teardrop will never see the conditions that make epoxy a better bet for boats.

I did not do a good job of finish sanding before painting and the paint came off with in the first winter. In spring the fiberglass cloth and Polyester resin pealed off the wood. I call that a failure!


Sounds like you didn't get the cloth wetted properly, the same thing would have happened with epoxy.
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Postby mikeschn » Thu Mar 16, 2006 8:31 pm

Using polyester resin, does one still have to put a top coat of spar urethane over it? Or is the polyester resin all one needs?

I'm trying to remember if Steve F. put spar urethane over his epoxy... :?

Mike...
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Postby Chuck Craven » Thu Mar 16, 2006 9:08 pm

I am not saying that Polyester Resin will not work! But for the first time user, it may not work as he/she expected it would. Many of the builders are using construction grade plywood. That type of plywood has waxed surfaces. But not all does! Polyester Resin does not get as hot has Epoxy does. Even if you sand the plywood the wax is still there. The heat of the Epoxy will drive the wax down into the fibers giving the Epoxy a chance to hold to the wood fiber. Polyester Resin sets so fast it can’t do that. If you change the harder amount in either Epoxy or Polyester Resin you will not get the right bond. With Epoxy you can select the hardener for a longer/shorter curing time, giving you a better bond and more time to work on it. So doing it cheep and take the chance of doing it over. Or spending a little more and get a better product. It’s like the Fram filter commercial pay me now pay me later. On this form someone was complaining about chi-ply wood. You get what you pay for. If you where building a $500,000 house and the builder use chi-ply delam plywood wouldn’t you be a little Poed. Real Poed if you had to pay for redoing it because you requested it to be used. Some one on this site used it on his tear and he is Poed. Some people think over engineering is bad.
But under engineering can kill someone. If you’re at fault then it is real expensive and in court you will always loose. Yes I over engineer things but I have never had any one hurt on what I have designed or built.
How many people have died crossing the ocean in a row boat before some one finely did it?
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Postby Chuck Craven » Thu Mar 16, 2006 9:18 pm

Mike
Polyester Resin is a short blue light reflector and will reflect some of the UV, as I have been told. That is why it is not as clear as Epoxy.
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