Walker Bay Dinghy hull repair

[caiusflatulanus]

Does anyone know how to repair small, below-waterline, holes in the hull of a Walker Bay dinghy (WB8)?? I have two small holes in the bottom of the keel just forward of the wheel socket. That part of the keel has become thin, presumably due to the friction of dragging the dinghy up and down the beach in an area with big tides..... Any advice would be welcome.

[Minggat]

I have one of those. It's my favorite toy. I carry it on my stern and sail it around every chance I get. It's my sports car when the RV (mother boat) is snug and secure.

I'm thinking of two ways to approach your problem. Maybe a combination of both.

The first one of course is to repair the hole. For that I would contact a plastics suppluy outfit. We have one in the L.A. Harbor area called Plastics Depot. You have to tell them what type of plastic it is of course. I have forgotten, or just don't care. Some kind of polychickenfat or something. I went to the Walker Bay website and it just says "proprietary mix". I've heard it called a "Bleach Bottle Boat". If you can get the plastics shop to understand, they should certainly have a method and or material. Due to the nature of the material as I see it, it would either need heat to do the job or an ABS glue. If you can get that far, you should be 90% on your way. Downsteam of that, you might consider making a stainless steel plate to fasten over the spot with threaded hardware. I'm thinking thru bolt if possible, and bedding compound of course. Then you would have a "skid plate" where you need it. Let the bedding set up for a good long while before you tighten the bolts. That way you won't have all the sealant squeezed out. Personally, I would use 3M-5200. Somebody else might have a better choice.

[GordMay]

Walker Bay’s “High Impact Marine Composite” (HIMC) hulls are an injection molded “poly-something” plastic, to which nothing will stick.

Plastic dinghies are most often made from roto-molded polyethylene (PE), or polypropylene (PP).
Variations include cross-linked, super-linear, or blow-molded polyethylene.
Roto-molding is a process where polyethylene pellets are fed into a heated boat mold, and the whole mold is spun and tilted in several directions to distribute the plastic evenly.
Cross-linked and super-linear polyethylenes have a slightly different chemical structure than normal, which result in stiffer, and sometimes lighter plastic boats.
Blow-molding uses the same polyethylene as roto-molding, but a blob of molten polyethylene is injected with hot air into a cold mold. When the blob contacts the cold mold, it cools rapidly and the plastic takes on a harder, stiffer finish.

I’ve had “limited” success with “welding” (fusing) a repair on my polyethylene dink:

First you need to acquire some polyethylene plastic or a polyethylene Weld Kit*. Rough up the area with sand paper 80-120 grit, prior to welding, as well as in between welds if you've allowed it to cool.

* http://www.northwestpolymers.ca/welders.html

If you've got extra repair material it might prove useful to do little test repair, melting one piece of repair plastic to another just so you know how fast it melts and how they bond together.

I have an electric “fusing” tool, which works great on smaller repairs, but a mini propane torch works best ,since it's easier to get enough heat, and control it.. A standard propane torch can also work if you keep the flame low.

Heat the repair plastic more than the boat itself. You would like the repair plastic to fully melt but not fully melt the boat, for obvious reasons. I heat the repair plastic first, and get it melting then apply it to the boat - heating both together, and making sure not to overheat/melt the boat itself. After allowing to cool sand or surform excess plastic

Most people are more interested in making the repair waterproof than making it look perfect. If you're repairing a crack and the finished look matters to you, use a dremel type tool to cut a vee along the crack. Fill in the vee with plastic strips. Sand or sureform any excess for a smooth finish.

I’ve never used products such as:
Marine-Tex Poly-Dura is an epoxy plastics adhesive for hard-to-adhere materials like PVC, ABS, polyurethane, vinyl and polyethylene* plastics.
*Polyethylene must be flame treated, see detailed instructions.
http://www.marinetex.com/PRODUCT%20P...ral%20Info.htm

[Minggat]

"I’ve had “limited” success with “welding” (fusing) a repair on my polyethylene dink:"

A lot of good info there. Obviously Gord knows what he's talking about. Which leads me to the quote above.

With all that said, even if you're success is less limited than Gords', ya might want a skid plate so you won't have to do it again.

[Hud3]

If the holes are small enough and the right shape, you could insert a SS bolt with washers on each side. Add a rubber "gasket", if you can. I've fixed such things with self-tapping screws, but a screw wouldn't be a good idea in this particular case.

[svHyLyte]

See the following http://www.westsystem.com/ewmag/16/plastic.html .

Good Luck.

s/v HyLyte

[S/V Antares]

I have used a Superheated hot air "Torch" much like TIG welding but you use Poly rod. Browered it from the local Mr Plastic.

Get some of the same material or an old water jug and practice! a lot! The difference between a weld/ patch and a puddle is a blink.

Did a repair in the Bahamas using strips of a Galley cutting board. Worked well.

Let us know how it worked out