Sunseeker 21’ Rebuild

Hello!

I have recently purchased a Sunseeker Sports 21’ According to the seller it’s a 1985 but I contacted Sunseeker directly and they have said it was a model built between 1977 and 1980.

Anyway, I plan on restoring her but also adding a few modern touches along the way. My first large job was to remove the carpet, plywood subfloor and remove the original fuel tank. (She would of originally had an inboard motor but it’s been professionally converted to have an outboard motor) The original fuel tank was all disconnected and now is just dead weight.

Unfortunately it seems that most of the stringers are rotten. I’ve read on multiple forums and articles that you should replace like for like. Same active core, same glass etc… But the tops of the stringers haven’t been glassed over like I have seen on stringer replacements on other boats. Is this okay? It also looks like the original glass is quite thin.

I’m replacing the Stringers with 12mm Marine Ply as this is what is currently in place. I’m a little stuck on which fibreglass to use and how many layers.

Any help or advice would be greatly appreciated!

I like to use dry pressure treated dimensional lumber for stringers. If plywood gets wet, it fails very quickly. PT solid lumber will last for years if it gets wet. After the stringers are installed, foam up the cavities for hull strength and floatation.

If you want a built-in fuel tank, it must be sealed and have a sealed connection to thru-hull vent and fill fittings.

Finally deck the floor by placing resin-saturated strips of cloth or mat on the top edges of the stringers and frames. Now screw thru the plywood into the stringers. Finally, cover the plywood with 2 layers of light cloth or 1 layer of heavy duty cloth and saturate and fill the mesh with resin.

I prefer you marine ply plan. Polyester resin, 1.5oz chopped strand mat, woven roving (I don't remember the weight), and a thickener for the resin.

Bed the stringers in the thickened resin, 2 mat and 1 roving on each side with 6 to 8 inch out on the hull. If you want to cap the stringers with glass, cut seperate strips. Glass won't roll around corners. Plan on doing the transom too.

Tyvek suit, disposable gloves, full face respirator, P100 filters, organic vapor filters, fiberglass roller, chip brushes, acetone.

Mike, so you think screws into the end of 12mm plywood will hold well, or are you not using screws to hold the plywood deck in place? Just curious.

Also, light FG cloth will bend around corners. Even medium cloth will bend, Using SS staples to hold it in place until the resin cures, can be useful.

Thank you both!

I’m going to stick with the Ply as it is what Sunseeker used. So Polyester Resin is okay to use? I priced up the job using West Systems Epoxy and it’s a lot more expensive.

I read somewhere that polyester resin is stiffer and doesn’t do as well with stress??

@

MikeSchinlaub said:

I prefer you marine ply plan. Polyester resin, 1.5oz chopped strand mat, woven roving (I don't remember the weight), and a thickener for the resin.

Bed the stringers in the thickened resin, 2 mat and 1 roving on each side with 6 to 8 inch out on the hull. If you want to cap the stringers with glass, cut seperate strips. Glass won't roll around corners. Plan on doing the transom too.

Tyvek suit, disposable gloves, full face respirator, P100 filters, organic vapor filters, fiberglass roller, chip brushes, acetone.

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Would these work..

- ECF Polyester Resin
- 450G (1.5 OZ) CHOPPED STRAND MATTING - 965MM WIDE
- 600G BIAXIAL CLOTH - 1.27 MT WIDE + - 45°

I don’t plan on capping the stringers as it wasn’t done from factory, I keep reading that you should replicate the existing rather than improve/change.

Chris1956 said:

Also, light FG cloth will bend around corners.

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I misspoke on that. It will bend, but it will cause air pockets at the

Sunseeker26 said:

So Polyester Resin is okay to use?

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That's what the boat was made with. Also, csm is bonded together with an adhesive that is broken down by the poly resin, but not by epoxy. So epoxy shouldn't be used with csm.

Sunseeker26 said:

I read somewhere that polyester resin is stiffer and doesn’t do as well with stress??

Click to expand...

I'm not really knowledgeable on the chemestry and physical properties of the stuff, but hulls made back in the '70s are still around. The wood is the weakest link. Some people will rebuild everything with coosa, but that's like $400 for a 4x8 sheet. Maybe more now and depending on thickness.

Chris1956 said:

Mike, so you think screws into the end of 12mm plywood will hold well, or are you not using screws to hold the plywood deck in place? Just curious.

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We use drywall screws. Stainless is overkill. If moisture can get to the screw to cause rust, then it will rot the wood anyway. Also another 2 mat and roving around the edge of the floor. It's structural, tying the hull to the floor.

Sunseeker26 said:

I keep reading that you should replicate the existing rather than improve/change.

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Same concept as a car really. There's no one right way, and three people will have three (or four) opinions on the same thing.

Far cheaper to buy the boat you really want without all this work. Good Luck!

Thank you Mike, I appreciate all your insight.

@airshot, I didn’t realise the stringers were in this condition unfortunately, the floor felt sturdy and sound!

The work actually excites me, I’m a perfectionist and I’m really looking forward to putting a stamp on this boat. The different types of glass and resins is a bit of a minefield but excited to learn it!! Unfortunately here in the UK most used boats are fishing ones that are more suited to our waters, I wanted a cruiser that can both!

Bust Out Another Thousand

She will be a fantastic boat once her bones are restored! A lot of the original features are there so she’s worth it!