Glues Fastners & Paint
There are many, many different materials you can use to build a boat with.
Here are a few of the glues, fastners and paints that are commonly used.
Glue Articles A Test of Different Finishes by Phil Keck The 10,000th test of PL glues by Phil Keck
Glues Titebond II - This is the most common glue used to build homemade plywood boats, it is a cheap yellow construction glue that has been around for many years and is available in most home improvement stores.
This glue is waterproof and after it is fully cured, can be submerged in water without worry that it will fall apart.
There have been many boats built with this glue, and many of them live in the water or are stored outside in wet climates.
The best way to use it is to spread the glue on both surfaces and then clamp them together.
Use a paper towel to clean up the excess glue that squeezes out, it is better to mop up excess glue than to have a dry joint that is starved for glue.
Wood glues in general seem to like lots of clamping, the more the better.
You can also turn this glue into a gap filler by mixing a filler with it, such as wood flour, wheat flour, sawdust etc and spreading it on like a putty.
The problems this glue has is that if used in large globs, it can form a skin and prevent the inside of the glob from curing.
Also it shrinks a lot as it cures, so if you use it as a fillter, you need to do small batches and let them cure, then add more if it shrunk too much.
This glue is also referred to as TB2
PL Premium - Concrete Blend - This is a construction glue that comes in a calking tube.
This glue is squeezed out of the tube and looks like toothpaste, but has the consistency of freshly chewed gum.
After it is fully cured, it remains rubber like and does not get hard and brittle.
This is an excellent glue to spread on the inside of all of the joints such as chine logs, it will seal the corners and prevent water from seeping between the plywood and the log to help prevent rot.
Not to be confused with concrete leveling product - the leveling is a liquid and a completely different glue.
Also not to be confused with landscape block PL, which is brown in color and doesn't stick that well.
This glue is also referred to as PLP-CB
PL Premium - This is a construction glue that comes in a calking tube.
It sticks to just about anything, but the difference between this and the concrete blend is that this version has a self bubbling agent so when applied, it forms many small bubbles.
Some people build with this instead of TB2, but the bubbles makes it unsighly and it is usually not used for gap filling or corner sealing.
DAP Bathroom Caulk - This comes in a tube that looks like a toothpaste tube, and squeezes out, typically colored white.
It is a great adhestive for attaching deckplates & access hatches like rubbermaid containers or bucket lids.
It sticks very well to most surfaces including plastic, cures to a rubber like consistency, but is weak enough that you can pull it apart, and remove it from surfaces with a putty knife.
It works so well, that I don't use fastners for access deckplates anymore, I just attach them with the DAP.
Silicone- This is almost completely worthless, the ONLY thing it is good for is to act as a gasket between 2 parts in compression such as windows or hardware that is bolted on.
I have seen many people try to use it as a surface patch or gap filler, and it is very poor for that application.
It sticks to itself well, but if not squeezed between two surfaces, it will quickly seperate from whatever it was smeared onto and fall off.
Marine Goop This is great (but expensive) stuff.
It is clear like silicone, but has amazing sticking power.
It will stick to plastic (and just about anything else) very well, and cures to a rubber like state.
Ironically, it is so strong that you should not use it for attaching deckplates, because if you ever want to remove it, you will have to tear it apart.
If you have a gap somewhere and don't want to fix it properly, you CAN smear goop over it and that gap will be fixed.
I like this so much that I have a tube of it in the kitchen and use it for many household jobs.
Liquid Nails - Very similar in apearance to PL Premium, but it has been reported that this glue does not hold well and so is not suggested.
Gorilla Glue - This is a fairly expensive glue, but works similar to PL Premium.
Epoxy - This is the 2nd most extensively used glue in homemade boat building.
It comes in a 2 part liquid form that must be combined in a specific ratio (like 2:1, or 5:1) to activate a chemical reaction, after which you have a short work time before it cures.
It sticks to darn near everything except plastic and wax.
It does not shrink when it cures, works great as a glue or a filler, can be thinned out with acetone, or thickened with a variety of fillers.
When using, this glue seems to prefer moderate clamping so there is still some of it in the joint.
The negatives are: it is not UV protected, so you must coat it with something to protect it from the sun, and the fumes are toxic, even though it doesn't smell that bad when you used it.
Epoxy is also fairly expensive, like around $35 per gallon, and not usually available in local home improvement stores.
This is a very usefull glue and can be used to fix just about any problem you have on a boat.
TIP: When wetting out fiberglass cloth, thin the epoxy with acetone first to make it penetrate the cloth easier.
Polyester Resin - This is sometimes confused with epoxy, but is a very different glue.
It comes in a liquid form with a small curing agent called MEK.
You mix only a few drops of the MEK with the resin to create the chemical reaction.
Polyester resin does not stick to other materials very well, but it does bond with itself if the next layers are applied within 24 hours of the previous.
Most factory produced sailboats are made with this resin, it is a great material for that purpose.
You should not use this as a glue to hold 2 parts together.
This is best used as a resin to wet out fiberglass cloth that is then applied as a skin to protect the surface below - such as fiberglassing the bottom of your PD, or coating the outside of your fins.
Also it makes a great molding material, you can mold your own parts.
It shrinks as it cures, so if you mold of a part, it will be easier to remove than if the part was made from epoxy.
Also when it cures, it makes a brain rotting stench which is highly toxic and many people allergically react to.
It is cheap, and UV resistant, and usually you can get it at home improvement stores.
Fillers
Gap Filling Trick - If you have a gap to be filled, one trick is to wedge a plug of sorts in it that is soaked in TB2.
This can either completely fill the gap, or it can reduce the gaps size to make it easier to fill.
TB2 & Sawdust - You can mix TB2 with a variety of substances like wood flour, talc powder, corn starch, wheat flour, sawdust etc to make it thicker, and then you can spread it like peanut butter onto an area you want to fill like a crack.
TB2 has a tendancy to shrink a lot, so you might have to apply a 2nd coat.
Also when fully cured, it doesn't sand that well, it is similar to sanding rubber.
The good thing is, you probably have a tube of TB2 on the workbench and it is not toxic you can work it with your bare hands.
TIP: before using sawdust as a filler, run it thru your blender and screen out the large parts.
Epoxy & Filler - Thickened epoxy is just about the best filler you can use on homemade boats.
You can use the cheap fillers like sawdust, or you can purchase a wide variety of fillers like glass micro baloons, silica, etc.
You can experiment around with the various fillers to find the one that you like the most for the type of finish you want.
After cured, the patch will remain stuck to just about any surface, and it sands really well.
Bondo - This is Polyester Resin that is thickened with a filler, and comes with a tube of hardener (MEK).
Both the bondo and the hardner look like toothpaste when it comes out.
It is commonly used in auto body repair, and it does work as a filler, but has the same problems as Polyester Resin, and after enough flexing & wet / dry cycles on a boat, the patch will fall off.
It is interesting that you can glue the patch back on with epoxy, and it will hold after that.
Elmers Wood Filler & Durams Water Putty - Both of these are very poor for using on boats.
They are powders that you mix with water, and they then cure to make a hardened patch.
The problem is the patch will not stick to wood, or if it does adhere for a while, the normal flexing will pop it out.
Like bondo, you can glue the patch back on with epoxy.
Fastners
Fastners are nails, screws and bolts.
Boats are mostly held together with glue, the fastners are primarily used for holding the wood together while the glue dries.
Some people even remove all of the screws after drying, so that there are no screws in the joint at all.
Others put a nail in every 2".
Personally I put a nail in every 4.5" or so and leave them in.
To measure, I turn the hammer sideways and go the distance from the face of the striking head to the tip of the claw, and drive another nail in there.
You can tell if you have enough clamping pressure by pressing down on the plywood to see if more glue squeezes out.
If more glue comes out, your nails are too far apart.
Ring Shank Nails - This is a nail that has rings around the shaft of the nail.
They are as quick to install as a nail, but hold like a screw.
After time, the wood swells a little and the rings around the shaft hold even better to the wood.
They come in a wide variety, the best for boat building seems to be the bronze silicone ring shank nails, the #14 at 7/8" is good for holding 1/4" plywood, and the 1-1/4" is good for holding 3/8" plywood.
The bronze won't rust, and if you need to run a saw thru it later, the bronze won't ruin your saw blade.
Galvanized Drywall Screws - These are the coarse silver screws that people seem to be using for everything these days.
The galvanizing will corrode & rust, but not as bad as the non-treated ones and they are cheaper than stainless screws.
Smooth Shaft Nails - Boats flex a lot, you should never use smooth shaft nails, they will work themselves out creating a burr that will cut your the next time your body passes near it.
Paint
The purpose of the finish is to protect the wood from the sun, rotting, and cover up building mistakes.
The paint and finish does not have to be completely water impervious, and unless you sheath the outside in fiberglass, it is almost impossible to keep the wood from getting wet because over time it checks (small cracks appear) and the water will soak in the cracks.
If you think about it, many houses are built with plywood exteriors which get rained on all the time, and they hold up just fine, so your boat will hold up if you treat it the same way.
Always use exterior paints, they have UV protectors and rot inhibitors that will extend the life of your wood.
Most paints have the consistency that 2 coats are thick enough to protect your wood for the first year.
You should paint an additional coat on your boat every year in areas that need it, to fill up the checking (cracks) and cover all of the scrape marks.
Latex Paint - This is a water based paint and is very easy to use, because you can clean up with water.
Most houses are painted with latex, and the modern day external formulas come with all sorts of rot inhibitors.
It is easy to sand after it is fully dry, and it is cheap to get.
2 coats of latex is not waterproof, it makes more of a surface like a coffee filter, it will let water pass thru it but as stated above, you don't need a completely waterproof surface.
The latex paint will apear dry after a few hours, but in reality it will take a couple of weeks to fully cure & harden.
You can take your boat sailing after only a day of drying, but I am not sure if that will interfere with the paint's curing cycle, and what long term effects it has on the paint.
Oil Paint - It is messier to use, but produces a harder surface.
The oil paint is getting harder to find these days, if you look down the isles of the stores, it seems that the oil paint is dissapearing.
You should apply oil paint in very thin coats, and let them dry for atleast 24 hours before applying another coat.
If you create bubbles, a skin will form and the center of the may never cure.
It isn't as easy to sand, the oil paint tends to quickly clog up sandpaper.
Oil -ON- Latex etc
There is much debate on whether you can paint oil on top of latex, and vice versa.
In my experience, it depends on how you prepare the surface, if the previous paint is fully cured, and which brands of paint you are putting on top of the other.
Oil almost always sticks on top of latex with very little prep, but if you want to have latex stick on top of oil, you need to sand it fairly well.
Porch And Floor Paint - Both latex and oil come in a "porch and floor" version, which has extra hardners and UV protectors in it.
I highly recommend getting this version of the paint, it is more durable than the regular external paint.
Epoxy - Good old epoxy, you can use it like a paint and finish the entire boat with it.
If you made your boat with lauan plywood, the epoxy will darken it a little and create an awsome bright wood finish.
The epoxy is not UV resistant, so you should paint varnish over it, or store it under a cover.
Some epoxies do resist UV fairly well.
You can paint on top, but it should be completely sanded first, otherwise the paint will not stick properly.
Varnish - It has been around since the beginning of time.
There are furniture varnishes & marine varnishes, I am not sure of the difference.
They are a bit on the expensive side, but produce a beautiful finish.
Polyurethane - This lets in more water than latex paint.
It quickly degrades in a marine enviornment, and is not suggested for boat building.
Wax - Fiberglass boats are often waxed to make a nice shine. It is NOT suggested to wax the exterior of your homemade plywood boat, because every year you will want to paint on an additional coat of paint, and the wax will prevent the paint from sticking.
There are wax removers, but it is a real pain to properly remove the wax.