Materials and Supplies
Resins
You are going to have 2 basic choices when it comes to resins- Epoxy and Polyester. There is much debate about
the merits of one over the other- Go to any web page or message board about boat repair and you will find countless arguments
about this very subject. I have done a lot of research into the matter, and in my mind, Epoxy resins win hands down. Personally, I
wouldn't even consider using polyester resin. Really, in all my research, the only advantage that I have found to polyester is the
price, but even this I feel is false economy, because in the end, I think that the numerous advantages of Epoxy more than make up
for the difference in cost up front.
Epoxy resins adhere to virtually any surface far better than polyesters do. You don't have to take my word for it, though- There are PLENTY
of technical resources on the web that will back this claim up. Epoxy adheres to wood far more reliably than polyester- Just ask anyone who has gone through the
heartache of building a boat with Polyester resin and wood only to find the two separating later... It's no fun! Look at the web sites for just about ANY company
that supplies the do-it-yourself boatbuilder, and you will. overwhelmingly find that they recommend epoxies. There is a good reason for this- They work!
I often hear the argument that polyester resins are 'safer' than epoxy. This is often backed by statements like "I have been working with polyesters
for years, and never got sick from them, But know a guy who used epoxy once, and had an allergic reaction", or some similar line. Yes, It's true- A small percentage of the
population will develop a sensitivity to Epoxies, which can result in adverse health effects ranging from mild irritation of the skin to far more severe reactions such
as breathing problems. But, most will never have this problem. And, You can decrease your chances of developing a sensitivity to epoxy by doing what you SHOULD be doing
regardless of the type of resin you are using- Keeping it off your skin!
Now, I am by no means saying that Epoxy resin is safe- Or even that it is 'safer' than polyester. They both have their hazards. But, anyone who has worked
with (or even near!) polyester resin and it's associated nasty styrene smells knows just how bad the fumes can be. Many of those same people that will tell you how 'safe'
polyesters are tell you that you 'get used' to the smell, and it doesn't bother you any more. Perhaps- But what kind of damage is it doing? That euphoric feeling that you get
when working with the stuff isn't really from a job well done- The stuff WILL get you high if you don't protect yourself from it. Is the damage long term? Who knows. Read
the MSDS for the stuff, and you'll quickly see that there is a LOT of nasty stuff in there. I find epoxies in general just a lot more user friendly- None of the nasty fumes.
Oh, Did I mention that the Hardener that you use with polyester, Methyl Ethel Ketone Peroxide (MEKP), is VERY flammable? And that it's also a severe skin
and eye irritant? There is a reason that UPS will only ship it in small batches without paying hefty extra fees. It's just plain nasty stuff. Goggle it, and do a little reading. It just might
make the extra cost of Epoxy seem worthwhile!
I am sometimes accused of making epoxy out to be some kind of miracle product, that can do no wrong. Yeah, I love the stuff, but it does have a few drawbacks. First of all,
you DO have to be fairly precise when mixing it. If it says to mix it 3:1 with the hardener, then try to get as close as you can. With polyester resin, you can vary the cure time to
suit the job and/or conditions by adjusting the amount of catalyst- but DO NOT try this with epoxy. You can get different hardeners for epoxy that vary the cure time, but changing the ratios
will just end up leaving you with an uncured mess.
So, Is there ANY reason to use Polyester? Well, I suppose that if you are on a VERY tight budget, and there is just no
way to swing it with epoxy. But, I'd save up my pennies. How much more does it cost? Well, Here is a breakdown using the current supplier that I use-
Epoxy
1 Gal Resin w/42.6 oz hardener (3 : 1 ratio), Total of 1 1/3 Gallons- $61.00. That works out to about $45.00/Gal
Polyester
1 Gal Resin w/Catalyst- $32.50
To me, It's worth that little extra cost. I'm sold on Epoxy, I do all my work with it. Much of the work done here CAN be done
with polyester resin, but you're on your own as to the specifics. Again, I'm NOT going to get in to the pro/con arguments on the subject,
do a google search and read up on it for yourself.
Ok, So we've settled on Epoxy. Now what? There are a lot of different brands out there, and I have used quite a few of them. I used to be a
die-hard West Systems user. They make a fine product, and a very complete system of various resins, hardeners, and additives that allow you to do virtually
anything you want to get done with their product. Add to that top-notch customer support and excellent technical information, too. On many of my previous projects,
I went through a LOT of their product. But, recently I have switched to another supplier, U.S. Composites. Honestly I have been just as happy with the product and the end result.
Better yet, the cost is significantly lower. West systems resin will set you back about $112 a gallon with hardener. Compare that to the $45 a gallon that I am paying
now- It's 2 1/2 times the price. I've used both products side by side, and honestly I can't tell a difference.
Some Epoxy Basics
I am not going to get really in depth here- Just kind of skim the surface. The manufacturer of the epoxy that you use will be able to provide you with better
and more specific information than I ever could. But, Here's what you need-
Epoxy Resin
This is the basis for the whole 'system'.
Hardener
This is mixed with the resin to start the chemical reaction that causes it to harden. It is mixed at a specific ratio with the resin- Anything from 1:1 to 7:1 or more. Most manufacturers make different hardeners for different applications or conditions.
Check with them to make sure that you are getting exactly what you need. Pay close attention to the temperature requirements for the particular harder that you are working with, especially if
you are working outside or in an unheated (or poorly heated) space. Many have minimum cure temps, and some will take a long, LONG time to cure at lower temps. Also, if you are working in a HOT
environment, you will want to get a slower hardener that will give you more working time. The manufacturer can help select the correct one for you.
Mixing Pumps
Virtually all epoxy manufacturers sell some kind of pump that measures out the proper amount of epoxy and hardener. You COULD go without them, and measure it all in graduated cups, but
the pumps are a lot faster and more precise- Well worth the investment. Keep in mind that some of the pumps come so you mix one pump of resin with one pump of hardener to get the proper ratio, and others measure out the same amount for each pump, so
to get a 3:1 ratio, for example, you need to put 3 pumps of resin and one pump of hardener.
Mixing Containers
Plastic containers work well- Especially flexible ones. You'll want a variety of sizes. They aren't too expensive, and they are reusable- Once the epoxy hardens in them, you just flex them a bit and it'll
'pop' out.
Protective Equipment
You want to avoid skin contact as much as possible. ALWAYS wear gloves when dealing with resins and hardeners. I use Disposable Nitrile gloves. Eye protection is also a must, and long sleeves are a good idea.
Cleanup Equipment
There are a number of solvents that work for cleaning up uncured epoxy from tools. I generally use Acetone. For getting it off the skin, I keep some denatured alcohol handy- It's a little
more 'friendly' than many of the other solvents out there. Also, Have plenty of paper towels and rags on hand.
Fillers
There are dozens of additives and fillers that allow you to modify the epoxy to suit your needs. Most of them thicken it in some way, to reinforce it, or to prevent it from sagging so it can be
used as a putty. We'll get in to the individual types as they are needed on the project, But I like to keep a good structural filler (Chopped glass strands, for example), a good general purpose filler, and
a fairing filler on hand. Most epoxy suppliers will have various fillers as well.
Ok, Now on to the fun stuff. If you are completely new to working with epoxy, You should mix up a batch or two to play around with before you get in to the serious work. Get an idea of how it mixes, how
it behaves, and how long of a working time you have with it. Add in some fillers, and see what they do. Glue some stuff together, fill some holes- Just get to know it.
To mix a batch up, measure the correct amount of epoxy and hardener into a mixing container, following the manufacturers instructions. With the epoxy I am using, The manufacturer calls for
a 3:1 ratio of resin to hardener, so I measure out 3 parts resin, then add one part hardener. Mix it well- And take your time. It is critical that the hardener be mixed well with the resin for it
to react properly. If you are using the resin as-is, without a filler, you are ready to go. This is how
Fiberglass
Fiberglass is made, as the name implies, from long strands of glass fiber. Glass is melted, then drawn out into long flexible strands. The strands are then woven or formed into different types of cloth,
which is then reinforced with resin. Different types of cloth are suitable for different applications-
Woven cloth
Woven cloths are available in various weights, suited for different applications. It, as the name implies, is woven from alternating strands of fiberglass, laid at a 90 degree angle to one another. You'll find them to be the most useful for general fiberglass repair. They are fairly flexible, conforming to odd shapes and curves well.
Woven Roving
Woven roving is pretty much just heavy cloth. It is used where greater strength is required, but is not as flexible as the lighter weight cloths.
Mat
Mat, also called Chopped Strand Mat (often shortened to CSM) is a cloth that is made up of layers of chopped strand laid on top of each other. For the most part,
CSM is NOT compatable with Epoxy- Because it is actually 'glued' together, rather than woven. The materials used to adhere the strands to one another are usually
only compatible with polyester resins. CSM is very flexible, but lacks the strength and rigidity of a woven cloth.
Biaxial Cloth
Biaxial cloth combines a layer of woven fabric with a layer of mat. Most of them are stitched, rather than glued, together- so unlike CSM they can usually be used with
epoxies. They provide high strength and a quick build up of thickness, but don't tend to be nearly as flexible, making Biaxial harder to conform to curves, etc.
Plywood
You're working on a boat, so of course you are going to use marine plywood, right? Well- Not necessarily. For a lot of restoration applications, Marine grade ply is actually
overkill. There are a lot of less expensive and more easily accessable options out there. If you live in an area like mine, even if cost wasn't an issue, marine plywood just simply is not
available. Ordering it is cost prohibitive, with the shipping charges and often high minimum orders. Your local 'big box' home center, like Lowes or Home Depot, Will have materials that will
work just as well for your needs, at a much lower cost.
The most important thing is to make sure that whatever type of material you choose is outdoor grade. The glue used in outdoor plywood is, for the most part, identical to the glue used
in Marine plywood. The biggest difference between marine grade and 'outdoor' is the quality of the interior plys- Marine grade usually is void- free, while other grades may have some voids
present. Usually, they aren't a huge problem, especially when used in laminations.
Plywood sheets are 'graded' by quality of their outside laminates. They are assigned a letter grade (A, B, or C). If you see a sheet of plywood marked "BC", it has one face
that is "b" grade, and one face that is "c" grade. If you look at the local store, you'll probably find a selection of exterior grade plywoods- In my area, most stock both AC and BC grade.
Take a look a the plys- Some of the lower grade ones will have fewer layers of wood making up the laminate- They are usually not as strong. Also, look at the sides for voids- While you won't be
able to tell about any voids in the middle of the sheet, if you see a lot of voids on the outside, you can bet that there will be more in the middle. That should be avoided.
The species of wood is also a consideration- You'll likely find pine, and various hardwoods. Pine will work just fine, remember that it'll all be encapsulated in resin anyway. There are some exterior
plys out there made from various imported woods that have been reported to not be very rot resistant- There is a bit of 'buzz' online about them in the boatbuilding community. Like the ever-present argument
about epoxy vs poly, there are a lot of opinions out there, and many of them are based on what so and so said or heard from a buddy. Frankly, I've used these plywoods in the past, and again, remembering that
all of this work is encapsulated in epoxy anyway, I don't think that it's going to make a difference in the long run.
Paint
There are a lot of different options when it comes to choosing what kind of paint you use on your boat. You'll have to balance out the factors of cost,
ease of application, and finish result. Unfortunatly, there is no such thing as a cheap paint that is easy to apply and results in a great finish!
Generally speaking, Marine paints can be broken down into 2 categories- Single part and multi part. Multi part paints must be mixed before use- Generally you add a catalyst that starts the hardening process
before you apply the paint. Single part paints are used right out of the can.
The easiest to apply paints are single part- But the tradeoff is the finish you get isn't as durable. The cost of a single part paint is also much lower. Single part paints are good for many uses on a boat, but
you have to keep in mind thier limitation. They can't be used on submerged parts, such as hull bottoms. Also
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