Questions

I have mentioned before the 18' cruiser I am building. It is coming time to glass the hull and I had some questions.
I am going to be using Bondo with fiberglass mats, mostly because i'm a broke af high school kid and It it what is possible to get. This boat will spend most of its life in brackish/salt water and I need to make sure that the Bondo does not corrode in the salt water. My primitive knowledge of composites would tell me polyester will not not corrode but I guess the main question here is do I need to coat the fiberglass or something or can i just leave the Bondo exposed against the salt water.

 

Is this a wooden boat (plywood, other, etc.) being sheathed by polyester? A fillers will need a top coat, particularly if using polyester, which isn't the best choice on wood and/or boats that will spend extended time in the water. If you do plan on extended stays on the water (doesn't much matter what type it is), consider using a vinylester over the whole shebang, once you've faired, Bondo'd and sheathed.

Simply put, Bondo doesn't have a very good reputation, without a sheathing, or at least a 10 mil resin coating over it. For extended stays in the water, you'll want a good bit more than a light 10 mil coating over Bondo.

 

1 bondo will not saturate the mats properly. Only a true laminating resins will succeed.

2 polyesters absorb water, swell, then blister finally falling apart. Bondo completes the process faster than most other polys

I had a skiff come into my shop a few months back. It had been left in the water for 5weeks on factory gelcoat (polyester). The bottom was completely covered with 1/2 inch blisters. I had to remove all the greatest then add a layer of epoxy saturated mat. Smooth with epoxy fairing compound, epoxy primer them paint..

3 anything left in fresh, salty or brackish water will have stuff grow. Anti-fouling paint slows the growth, but it still needs to be wiped off regularly.

 

Yes, The boat is a wooden boat that is being coated in some sort of composite. Can you point me in the right direction for finding a vinylester?

 

A wooden boat is best encapsulated in epoxy, then sheathed with fabric. Next on the list would be just encapsulation with epoxy, no sheathing though some species of plywood will "check" and crack (like Douglas fir) without a sheathing and all wooden boats without a sheathing, will lose the abrasion protection it provides. Vinylester is the second best choice with the same condisions as epoxy. Polyester is the least favorable resin system to employ on a wooden boat, though is done occasionally. For it to be truly effective as a waterproof membrane, it needs to be relatively thick compairtivly, with a fair bit of fabrics too, which all but defeats any costs savings you may think you're gaining. Simply put, you'll use so much more of the resin and fabrics, that it all but equals out.

Google is a wonderful thing and "vinylester" is about as easy to find as bad **** sites. Discount resin formulators exist all over the web, most supplying resins at about 1/2 the price of the major brands. You can pay over a hundred a gallon for West System epoxy or about half this at one of the discount formulators. The same applies with most of the resin formulators, who also supply polyester, vinylester and the fabrics you'll also need.

Lastly, I can't tell you how many (hundreds) of boats I've seen that were sheathed in polyester, just to find it didn't work very well and sheets of fabric are hanging off it's flanks after a while. Cutting corners on the resin system isn't generally considered a wise move, particularly when you add up all the costs of the other materials in the boat, which will have a similar fate, when the sheathing or resin fails. Unless your boat is only intended to live a short time, you should bite the bullet and use epoxy. You might spend a few extra 20's, when all said and done, but the material is so much superior, it'll easily pay for itself.

 

Chipping at my life savings here, but do you think 30 gallons should be enough to complete my boat with the epoxy? Looking at West Systems 105 Epoxy.

 

Sweet God, 30 gallons? The last 18' boat I built took about 5 -6 gallons. Again, West System and the other major brands cost twice as much, as the discount formulators. Do a search and you'll find formulators that sell at 1/2 of West System. It's not that West System and the other major brands aren't very good, as they are, but when you compare the base resins and hardeners, their additives and other ingredients, plus their physical properties and attributes, you'll find they're very similar, so why pay the premium price.

 

Thats kinda what I had in mind. Also thank god there are cheaper ones that will work just fine! I was starting to get a little scared about finishing this project (I'm a high school kid that cuts firewood for money) One Epoxt that I have looked into is the composite pro system by Resin Research. Price list / shipping http://resinresearch.net/id6.html MAybe you could take a look and tell me what you think. I have used polyester resins before to put the backs on bows that I make but other than that I don't have much experience with fiberglass.

 

I don't have any experience with Resin Research products, but you can find lower pricing. Try Progress Epoxy (epoxyproducts.com), Marinepoxy (boatbuildercentral.com/products.php?cat=MarinEpoxy or B&B brand (bandbyachtdesigns.com/store/533-2/). These will be some of the lowest if buying small amounts.

Using epoxy is different from polyester. Follow the directions (precisely) for resin to hardener ratios. Unlike polyester, where you'll screw around with the mix, you can't with epoxy. Also do yourself a big favor and look into some of the online procedures about applying goo and fabrics. Westsystem.com and Systemthree.com have good documentation about how to apply, mix and generally use epoxy. It's real easy for the novice to screw up a batch or two, until you've learned (the hard way) about the proper way to get things to do what you want. Once you've established the good set of procedures, it'll go a lot easier, so do some research.

 

You have done yourself a favour not using Vinylester.
As well as not being as good as Epoxy, it really, really stinks - like burning plastic chairs.

The Epoxy is actually easier than Polyester. because you don't have to be so picky about adding small percentage of Catalyst to a bucket of goo. Epoxy is either half and half, or 5 to 1 or similar.

It's worth doing just a few small sections to get the hang of it, but there are a couple of small tricks that might help.

When wetting out the Epoxy, even if the temperature seems comfortable, you might find a little warmth from an electric heat gun or hairdrier makes the Epoxy a little runnier, and does a better job of wetting out the cloth, quicker, and will speed up the Epoxy setting too.

If you're doing a cruiser, there might be quite a few flattish sections on the hull. If so, you can use some stuff called Peel Ply, or even some Taffeta from a fabric store. You can then roll approx metre x metre sections out over the wetted out Epoxy and Fibreglass, and smooth it down with a squeegee. It helps remove excess epoxy, and all the bubbles. When the epoxy cures, the fabric "peels" off, and leaves a really flat, smooth surface needing very little finishing.

Spend a little time on a few test sections, and it will make sense. There are some pretty good videos on applying epoxy to check out as well.

Good luck with it all.

 

Sounds good, I will look into the different brands of epoxy, is it required that I put some sort of finish on the epoxy or will it be ok that the epoxy is in contact with the sea water? If I can get away with skipping out on the finish I would love to in order to save some money. Also I have looked into using 1.5oz mats and layering a few mats on. The glass on the hull needs to be sort of load bearing and sturdy because the wood is not water tight and the quality of the wood is a little bit questionable. I feel like the hull will need two or three layers of overlapping mats at any point on the hull. Just based off my experience with making fiberglass bows I know the stuff is pretty strong but last thing I want to do is get into the middle of the swamp this summer on my journey and have an issue that puts my boat half way under water.

 

I will look into this, I have some experience with using fiberglass to make bows but this is kind of new to me. There are some big flat sections on the boat, will this peel ply stuff you are talking about help save time and money and epoxy on those sections? also is it sturdy? the glass layer of the boat needs to be pretty strong due to the fact that the wood is NOT watertight and is of poor quality. The wood almost works as a mold to build the fiberglass off of.

 

It will certainly save time, and it makes the Epoxy Resin go further.
By squeegeeing out excess epoxy from under the peel ply, you prevent having too rich a resin matrix. The strength of the glass layer is improved.

Probably more important from a cost saving point of view, you will save the cost of abrasives and fillers by making the layup more accurate. It's amazing how quickly the consumables add up.

Don't forget, if you can't afford commercial Peel Ply, get a couple of samples of Taffeta from your local fabric shop, and test which ones will do the job. The peel ply doesn't have to be sturdy - you peel it off after the epoxy is set. It's a throw away item.

 

Peel ply is just a work saver, but you'll waste a bit more resin using it. Plus it doesn't remain on the surface, it's just another tool you have to buy, so it's sturdiness doesn't matter. I mention this to the novice laminator, which I don't think will have nearly as good a time with peel ply, until you learn why it's beneficial.

Do your laminating and epoxy research . . .

 

Well, no - it will SAVE resin. AND it will also save on consumables like wet and dry abrasives and fillers. Avoiding those awkward little excess brush marks, or runs or ridges from the end of the squeegee saves a ton of sanding.

What oozes out from under the peel ply can be redirected to further up the hull onto the fibreglass cloth, or even collected back in the bucket. The only time that it wouldn't be a good idea to re-use it, is if you are trying for a really clear finish. Any bubbles entrapped in the excess can be removed with the help of the warm air source I mentioned earlier.

One other thing that peel ply does a great job at, is holding the fibreglass cloth down on tight curves in the hull where the glass cloth is trying to pull itself free.
If you are glassing the edge of a deck, or a strake on the hull, squeegeeing down peel ply over it ensures a firm attachment.