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Hull Repair on an Old Hobie
Do-It-Yourself: Catamaran Soft Deck Repair With Expoxy Injection
Hull Repair on an Old Hobie
By Rob Morse (prindle599), written April 17, 2013
Soft decks are not a death sentence for your old boat. It took me a few hours to re-bond the inner skin of the deck to the foam core to repair the soft decks. It took longer to refinish the deck than to make that structural repair. The repair isn't difficult, but it does take some feel to get right. The old Hobie decks have a thick outer laminate, a foam core, and a light weight inner skin. In my case, this inner skin came away from the core and I glued it back together. Here is the short version of how it's done before I give you a full step by step description.
- Drill holes in the outer skin.
- Carefully drill through the foam core by hand.
- Inject thickened epoxy between the inner skin and the core.
- Pull the cores together with sheet metal screws.
- Let cure and remove the screws.
- Fill the holes with thickened epoxy.
- Sand, fill and refinish the deck.
It sounds easy, and it is if you take it step at a time. Read through the directions several times. Do all the preparation work you can before you mix epoxy, and don't forget to chock the trailer wheels if the boat is on a trailer (Free lesson number 1. Yes, I chased the trailer around the garage.) The size of the hole we drill is determined by the size of the syringe tip we use to inject the epoxy.
I used a standard syringe with Luer Lock syringe tip. The screw is a number 8 sheet metal screw (#8 x 1) and the drill is a #17 of .173 inch diameter.
Required repair tools-
drill motor, #17 drill bit, tape, rubber gloves, permanent marker, 20cc syringe, rubber tubing, mixing cups, stirring sticks, paper towels, shop apron, #8x1 sheet metal screws, small instrument screwdriver.
Mark the deck-
(picture- 1 rule)
I wanted the screws to be about 1.8 inches apart so I made a paper guide and marked the deck. Keep thumping the deck and keep marking until you find hard deck.
Drill the outer skin-
(picture- 2 drill outer deck)
Using a drill stop, drill holes approximately ¼ inch deep through the top deck. The drill stop can be a metal tube or a strip of firm tape rolled onto the drill bit. Use a stop or you will accidently drill through both skins. (Free lesson number 2) Drill through the top skin only. Go ahead and drill all the holes through the outer skin of the deck. (picture- 3 drilled deck)
Drill the core-
(Picture- 4 drill through core)
Remove the drill stop from the drill bit. By hand, drill through the core by twisting the bit between your fingers. Do not push. Stop drilling when you feel the resistance of the inner skin against the bit. Do not drill through the inner skin! (Free lesson number 3) You can feel the inner skin flex away from the bit and then feel the bit pushed back out of the hull as the skin moves back into place. Drill all the holes through the core.
Prepare and inject thickened epoxy between the core and skin-
(picture- 5 syringe)
(picture- 6 fill)
I used a 20 cc syringe with a short rubber tube slipped around the tip. The rubber tube forms a seal between the deck and the syringe body. Mix up epoxy and thicken it until it has the consistency of honey, catsup or mustard. A water-thin laminating epoxy will leak through small holes in the inner skin. A mixture that is too thick will sit as a lump and keep you from pulling the skins back together.
I injected a few cc of epoxy into each hole until I saw the epoxy squirt out the adjacent holes. I only injected one row of holes before I installed the clamping screws. Stop squirting and start screwing once you've put epoxy in the first row of holes.
Pull the cores together with sheet metal screws and let cure-
(Picture- 7 screw)
(Picture- 8 fasten)
Put mold release on the sheet metal screws. I used bright plated screws and a light coating of release wax to keep the screws from sticking. Screw through the inner skin. I used a small electronics screwdriver so I could feel the torque on the screw. Continue to tighten until the inner skin is pulled against the core. It is easy to strip the screw in the inner core, so be very gentle. (Free lesson number 4)
Leave the screw in place and move on if you do strip it because the screw at least seals the hole. Continue injecting epoxy and pulling the cores together as you work your way along the repair area.
Wipe up any excess epoxy now. It is easier to wipe up the liquid than sand off the solid epoxy, so wipe up your spills. Let the epoxy cure before you remove the screws.
Remove the screws and fill the holes-
(picture- 9 fastend)
You now have a hard decks. You also have a bunch or rough screws sticking out of the deck that give it an industrial Frankenstein non-skid look. I prefer a smooth deck. Back out the screws. Wipe the area around the screw holes with a solvent soaked towel to remove any mold release. Fill the screw holes with thickened epoxy. This epoxy mixture must be thick enough to stand on its own and not drain out of the screw holes.
You want something that is as firm a mayonnaise or peanut butter. Fill the holes in the deck. I wanted to leave a solid plug of filler between the inner and the outer skin, so don't I wasn't skimpy with the filler.
Smooth and finish-
I rasped, sanded and refilled the repair area. Then I waited until another sailor was having their boat repaired and had a professional shoot on gelcoat.
Please comment with your experience if you use this repair method.
Rob
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Comments
Add a new commentAs for mold release on the screws, I used a toilet O-ring (not a used one). I just shoved the screws into the O-ring and got them all waxy. I also used self-drilling screws. It kept me from having to drill through the inner core by hand. So far so good.
I have a blue '81 cat fever, and can't wait to get it back in the water.
Thanks to Rob for putting together this tutorial. It gave me the courage to take a drill to my hulls.