Recoating a Driftboat Bottom
For all the benefits offered by an aluminum drift boat, there is only one main drawback, and that is the fact that operation in very shallow waters will only be as good as the bottom coating. Bare aluminum "sticks" very well on rocks, and that grabby nature can get bothersome when low water conditions make frequent bottom contact a fact of life.
Bottom coatings like Gluvit and Coat-It keep aluminum drift boats operating at peak levels. Trouble is these products wear, and over time will require maintenance, or the boatís performance will suffer.
Redoing a drift boat bottom is not hard work. It is however, loud, messy and generally not fun. Because of this, youíll want to make every effort to get the best adhesion (and resulting longevity) when you do take the time to redo your boat.
Optimal time of year for this project is the heat of summer. The main reason for this is the ability to work outdoors. First, the dust created in this process is a mess and will permeate every corner of an indoor environment. Secondly, the epoxy bottom coatings benefit from summerís heat in the curing process. Schedules and available time being what they are, I took on my drift boatís bottom in Decemberís cold. This does provide some challenges, but they are not deal-breakers.
If you want to power this project out, the work can easily be completed in a day (allow more time for the epoxy to cure). If you work at a leisurely pace, a weekend is an easy deal.
-1 Helper (part time)
Metal edged scraper
-60 Grit Flapper Wheel
-1 Qt. Acetone
-Masking Tape and Newspaper
-1 Gallon of Gluvit or Coat-It
-Cheap Plastic Trowel
-Cheap Paint Brush
-Propane Heater (winter only)
STEP ONE: Empty the Boat
Removing all interior seating, storage compartments and benches makes for a much lighter boat to flip over. In addition to the obvious, remove your oarlocks so they are not bent or broken in the rollover process.
STEP TWO: Roll the Boat Over
When aluminum drift boats are empty, theyíre really pretty manageable. My wife and I can handle the task of getting the boat flipped. Once rolled, put blocks under the bow and transom to provide greater stability (and take pressure off anchor releases if theyíre in the way).
*POUNDING OUT DENTS-When you roll the boat over, you may be surprised at the wear and dents your boat has accumulated. Unless thereís a random, dramatic dent in a low wear area, I leave all the dents and depressions alone. The reason is that the bottom coatings do not flex well as the bottom dents (they all say they do, but they donít) and as a result, the bottom coating separates from the metal. A pre-dented bottom will hold the coating better in the second round than one that you pound out, only to push in again under normal use. If youíve put a few "tunnels" in the bottom between floor supports, donít sweat it.
Photo 1 shows the worn bottom. Not horrendously bad, but the remaining Gluvit is doing little as the main impact area has been worn away.
STEP THREE: Scrape Loose Material
Looking at the bottom, there will be places where the old bottom coating is flat gone, places where it is loose and places where there are bubbles. Using a metal edged scraper, attack all vulnerable edges and remove every bit of material you can with this method. In the end, virtually all the old material will need be removed and this is the cleanest and most peaceful way of doing it, so spend some good time here.
PHOTO 2 shows just how much material you can remove by working at it a little bit with a scraper.
STEP FOUR: Grind Off Remaining Material
Using a 4" grinder with 60 grit flapper wheel attached, grind off all the remaining old coating. Do not forget a dust mask and safety glasses, and dress knowing full well this will be a mess. Once you get a feel for how the wheel cuts, this can go pretty fast. On my boat, I ground off all high-wear areas and any spots where adhesion was poor on the last bottom coating. I stopped short of removing all material in the very front of the bow and very rear of the stern because these are not wear areas, and I still had good material in these places. I faired in all the edges, took out any bad spots and called it good.
*PROPANE TORCHES- Iíve often removed epoxies and varnishes by heating the material with a propane torch until it softens (and loosens), then scraping it off. This is not a good option for aluminum boats. The heat-treated alloys in aluminum boats require extreme caution in the application of heat. If misused, excessive heat can damage your hull integrity.
Photo 3 Ė Youíll need a grinder with flapper wheel, safety glasses and dust mask.
Photo 4 is the boat bottom with grinding complete. All remaining Gluvit will stay.
STEP FIVE: Expose Clean Aluminum
Go back over the complete bottom with the grinding wheel. Apply no pressure, only the weight of the grinder and expose bright aluminum. This will provide a fresh, rough surface to promote the best adhesion. I also smoothed out any nicks and cuts in the chine, while preparing the chine for coating also. Those areas of Gluvit that where not completely removed were surface scuffed also.
Photo 5 shows the bottom once it had been gone over a second time with the grinding wheel to provide a base for the Gluvit to adhere to.
STEP SIX: Clean
Brush as much dust as you can from the bottom and do a final cleaning with Acetone to achieve a ready-to-coat bottom.
Photo 6 Ė Cleaning with Acetone removes oils and contaminants. After a while it gets really groovy too, but the hangover is a killer.
STEP SEVEN: Prep for Gluvit
Even under the best conditions the epoxy bottom coatings will run for a period of time. Tape off and protect side paint on your boat. I run the tape through the middle of the chineís exterior in order to allow coverage of the lower portion of the chine itself. Wide tape allows newspaper to be attached also to protect paint from drips.
Because I did this project in December, temperatures were very cold. Cold temperatures slow the chemical reaction of the epoxy, dramatically lengthening cure time. To counteract this, I used a propane heater beneath the hull to warm the aluminum and achieve a faster cure rate. Preheat the hull realizing that flooring has to become warm before the heat will get to the bottom itself. Leave the heat on during and after the application process. This step is only necessary in cold environments.
Photo 7 shows my makeshift hull heater, along with the newspaper protected sides prior to coating the bottom.
STEP EIGHT: Apply the Bottom Coating
Mix the bottom coating per the manufacturers instructions (MIX WELL OR THE EPOXY WONíT CURE!!!) and apply in workable quantities to the bottom. I like to use a trowel instead of a brush to move the material around (a good stiff piece of hard cardboard is fine too). Spread the material in sections, focusing on the high-wear areas (under passengerís feet to rowerís seat). A light coat is all thatís necessary far-forward under the bow and far-rearward in the stern. Apply the thick coat in the area it counts.
A brush is handy for addressing the chine and any detail areas. Apply the whole gallon (or however much actually comes in the gallon container) to the boat.
Photo 8 shows the Gluvit and hardener additive. Gluvit and Coat-It are competitive products and as far as I know both are good. I havenít seen a side-by-side comparison to really judge them against each other.
STEP NINE: Baby-sit the Job
Under the best of conditions in terms of temperature, the epoxies require a few hours to reach a state where they wonít run. During this period, pay attention to all sloped areas: bow, stern, chine and dents. Trowel and brush the material back into position as necessary to produce an even coating. This is not an art project, so no need to go overboard, but I donít like the material to pool excessively in depressions. Iíll also guarantee you it will run off the nose of the boat if not attended to.
If you happen to be running a heater under the boat like I did, do not leave the heater unattended. One small gas leak and the flames get quite large (donít ask me how I know this, but thank God I was there).
STEP TEN: Allow to Fully Harden
The can says the product will harden in 24 hours, but the last time I did mine outdoors (in the heat of summer) it took two days and this time in the garage, it also took two days. Fully cured Gluvit looks almost like glass and feels as hard. You should not be able to dig a fingernail into it.
Donít rush to get your boat back on the trailer. If the coating is not fully cured, you may glue your boat to the trailer. Be patient and take your time. When it is ready, flip the boat back over and reload. Youíre set for another few years, depending on the amount of use.
While youíre waiting for the bottom to dry, the boat being upside down offers an easy opportunity to hit it with a coat of wax.
Photo 9 Ė Fully cured Gluvit will be clear with maybe a little color in the deeper areas. It should have a mirror-like finish and be seemingly hard as glass.
Total cost for the project is less than $100. Expect to pay $500 or more if done by a shop. Itís not a hard thing to do, but youíre paying for a lot of labor and mess. I personally like to know how each step of the process has been handled and that Iíve achieved the best possible coating and adhesion.
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