Builders' Forum Archives
Re: Fiberglassing How To
Posted by Robert N Pruden on May 10, 2005
I am assuming that you have sealed the panels and done all filling necessary to create a smooth finish on your hull.
Tools to have at hand before starting:
-mixing cups for epoxy, have several: you don't want setting epoxy mixed in with fresh epoxy, this causes the fresh stuff to be thicker than you want it. I use plastic beer cups that sell for $2/24 -a few mixing sticks, these can be scraps of plywood thin enough to use, or popsicle sticks -soft plastic spreader with fine edge -a few cheapo 2" paint brushes to tip off: meaning you use the brush to spread any blobs of epoxy that need a smaller effort than what you get using a spreader -gloves, a few pairs of latex or nitrile will do -good ventilation or a half-mask with organic solvent filters to keep you from becoming sensitive to epoxy vapours
Ok, the hull will be upside down on a level surface. There will be four contact points at the bottom where the hull rests on something. Those points must be level or you may end up with a twist in the hull, which you will not be able to remove once the glass is on. Once the hull is laid out level and you are certain there are no twists anywhere, you are ready to lay out the glass.
Drape the glass over the hull so that the glass just overlaps one side by a half-inch or so. Use sharp scissors to trim the other side so that there is a half-inch overlap. You should have enough width that the glass fully wraps the hull in the middle with extra width hanging over the bow and stern. Trim the excess glass away from the bow and stern. Now you should have an upside down hull with enough glass to cover all of it with a half-inch overlap hanging below the sheer panel.
SPECIAL NOTE: What you do from this point on is permanent. If you mess up any batches or are uncertain whether you mixed them up properly - toss them out BEFORE using them. If you take a chance and use a bad mix, you waste all that nice glass and have to clean up your panels before restarting. IT is better to lose teh $$$ for a batch of epoxy than lose all that time and $$$ for replacing the ruined glass.
Mix up a double batch of epoxy to start. This will give you enough epoxy for ~10-15 minutes work. As you gain confidence in wetting out the epoxy you will naturally want to mix more. I would mix no more than 4 pumps of resin/hardener at any one time, especially if it is hot outside. If you find that the epoxy is thickening before you use it all, make your next batch smaller.
Once you have mixed a double batch of epoxy, start wetting out the glass. I would advise you to start by using a brush to spread the epoxy from the center of the hull on the keel towards one end. Don't brush the epoxy along the entire length, just do a couple of feet at a time. You will finish one half of the hull (bow end, for example) the finish the other end (stern) afterwards.
Brush the epoxy from the keel (center of the hull) down to the side (sheer panel) so that you have a band of glue that effectively cuts the hull in half. Use the spreader to spread the band of epoxy so that you don't leave a thick layer of glue to harden before you can get back to it.
Working toward the bow now, pour all of the epoxy out of your mixing cup along the keel. Use your brush to spread it along the keel, then use the spreader to spread it "gently DOWN" the sides of the hull. DO NOT USE A LOT OF PRESSURE while using the spreader. You want to spread the epoxy over the glass and have it absord into the weave. When that happens, the glass disappears and the wood grain appears. This is the stage where you really get to see how beautiful your boat will look. You should scrape the epoxy along carefully so that the weave of the glass just shows through the epoxy. At this point the glass weave is saturated with epoxy but not overly so. If you use too much epoxy it will run and you will have to scrape off the excess epoxy. This is imporant NOW because if you don't get rid of those runs now, you will have hours of sanding later on to remove them.
Keep mixing batches of epoxy as you need them. When you get to the bow you will notice that the glass has stretched somewhat and you have excess glass hanging over the bow. Trim off the excess glass so that the end of the glass is almost even with the end of the bow. Wet this out. You are now done wetting out the bow end of the hull.
Move to the stern half of the hull and keep the glue spreading. You might find that the band of glue you started with is kind of thick, that is because during all the time it took you to wet out the bow half of the hull, that band has started to cure. That is why you had to spread that layer of epoxy thin, so that the band doesn't set thick and mess up your final finish with a chunky look in the middle that you'd have to sand off later.
Spread the epoxy on the stern half as you did the bow half. Take care to look for any flaws such as air bubbles or runs on the bow half as you wet out the stern half. These are easily removed by using the spreader. Sometimes air bubbles form because there isn't enough epoxy on that spot, add a little epoxy there and spread it evenly.
When you get to the stern end of the hull, trim off the excess glass and wet it out as you did at the bow end. At this point you should be looking at the entire hull wetted out and looking very good. You should see the surface of the weave of the glass showing through. Carefully look over the entire length of the hull for any flaws that don't look right. If there are none then you have done a good job of wetting out the hull.
Air bubbles are your greatest enemy so make certain they have been pressed down using gentle pressure with the spreader.
You might have an outgassing problem that happens when gasses are released through the glass from the wood as the air temperature rises during the day. That is why it is ideal to start gluing during stable temperatures that start falling near the end of the day. I have never had this problem but I live in a rather cold part of Canada where temps rarely get hotter than 30 C (80 F). I also have a rather cool garage that is relatively cool even on hot days.
If you have any further doubts, let me know, I'll be checking this thread every once in a while. You can also phone me if you have to, at 780-434-0080, ask for Rob. I'm always happy to help a fellow builder. When I started building I had the help of dozens of experienced builders who helped me do a great job on my first boat.
Robert N Pruden
In Response to: Re: Fiberglassing How To by Eric on May 10, 2005
- Additionally by Robert N Pruden on May 10, 2005