Friday, February 4, 2011

This Old Hull – Laser Deck Repair with Air Pressure

Somewhat housebound after yet another New England snowstorm this winter, I’ve had the chance to work on my 23 year-old Laser hull with decks adjacent to the cockpit so soft and sagging that they seemed to be structurally unsound. My good friend and fellow Laser enthusiast, Yarg, told me that the problem might be delamination of the fiberglass-foam sandwich deck structure. Pictured below is a piece of the 1/2” thick deck material which I had cut out for an access port some years ago in order to repair a cracked mast step tube.

Inspecting the underside of the deck, using a mirror, and an existing access port next to the centerboard revealed what appeared to be perfectly intact fiberglass. However, pushing on the deck seemed to suggest an airspace as the upper deck surface made a crunching sound when it touched the rough foam surface below. My findings probing through a 1/16th inch test hole were consistent with the delamination theory as well. Perhaps the deck might be repaired by injecting epoxy into the space between the layers, but without easy access to the inside of the hull, clamping the two sides together would be problematic. Pushing from the top only would leave a seriously sagging deck. The answer appeared to be pressurizing the hull with an electric air mattress pump.

I began the repair by cautiously connecting an electric air mattress pump to the stern drain hole applying just enough pressure to cause the sagging deck to rise. Too much pressure, causing the hull to explode, would be counterproductive. Drilling holes in the tubing reduced the air pressure as necessary. After covering the deck with masking tape, I drilled an array of 1/16th inch holes into the soft areas of the deck using a hexagonal pattern, 2 inch hole to hole spacing, and 3/8th inch depth. The hand drill had a stop using a piece of dowel to prevent drilling too deep. Five 1x2s clamped across the deck prevented the deck from rising above its normal flat position when the air pressure was applied.

West Marine extra slow curing epoxy allowed enough time for me to inject all the holes before it thickened. I injected the epoxy using a West Marine syringe with a tapered nozzle that fit snugly into the 1/16th inch holes. I loaded the syringe by removing the plunger and pouring in the epoxy. It takes way too long to try to suck it into the syringe. I injected one syringe-full (about ½ ounce or 15 ml) into only 1/3 of the holes which worked out to holes with a 4 inch spacing pattern. The other 2/3 of the holes allowed for excess epoxy and air to escape. The average epoxy thickness was about 2.2 mm or 3/32th inch. It was comforting to see the excess epoxy and air bubbles flow out of almost every hole when the air pressure was turned on indicating that the epoxy had spread out well. I injected some extra epoxy into any hole that was not oozing.

After leaving the air pressure on for 24 hours (praying the pump wouldn’t conk out before the epoxy hardened) the deck appeared to be quite solid. A few of the holes were leaking air, so the pressure was turned off, and the leaking holes were sealed by injecting a little more epoxy. By the way, pressurizing the hull is a good way to find other leaks as well. Running my hand under the joint between the deck and the hull revealed a previously unknown large leak near the bow with air blowing out. I’ll do a search for smaller leaks at some point. The final step for the deck project was to apply some Gel Coat repair material to the 1/16th inch holes.

The soft, sagging deck is now flat and solid, but will it be good for another 23 years (or even 23 minutes of sailing in rough conditions)? Time will tell.



  1. Great site, keep it up the great work.

  2. Fantastic article for anyone wanting to do this repair correctly, as you have done. I've read so much rubbish about repairs using polyurethane products like 3M 5200, which of course is completely the wrong way. Well done!

  3. Do you have any more details on this? I'm curious which epoxy you used and how much it took. Which gel coat repair did you use and how much of that did you need, do you have any info on that part? I have an '87 Laser with sagging decks that make the same noise as yours and I'd like to fix it this winter.

    Also need to fix some chips in the blades if you have any wisdom on that process.

  4. See a new posting, "This Old Hull Update" for most of your answers.
    For blades I use West System epoxy with 404 High Density filler. The only prep I do is a little tapering all around the chip with sandpaper and an acetone wipe off. Mask around the filled area to keep epoxy off other parts of the blade. It does not really matter how you fill the chip; use peanut butter texture and dab it on, or use thickened but pourable mix into a a partial mold (usually one side but not both). Plan on doing a lot of sanding. I start with 100 grit and work my way to 400. If it was the blade for my best boat I would go to 600 or even 1200 grit. Then use multiple coats of Teflon polish. The board should feel extremely smooth, even slippery. If you use the white epoxy coloring additive you won't see much color difference.
    To repair a big missing chunk I try to get some reinforcement into the repair. I use 5d SS shingle nails stuck into the foam core of the board. Leave the heads if there is room, or cut them off. Making a mold for one side will save a lot of sanding. Usually a small piece of wood clamped on will do it. Put wax paper on top of the wood to prevent a wood/epoxy bond. A potential problem here is that a big glob of epoxy generates a lot of heat. The mix can actually smoke and it bubbles. That reduces strength and necessitates the need for more filling of holes later, but even when this has happened the board repair remains solid. You can use gel coat on a big repair, but it easy to sand through the gel coat when you are finishing it. For a pretty look re-gel coat or paint the whole board when you are done.

  5. I'm curious if this repair added significant weight to the hull?

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