IOM rollup

by mark | 20 Dec 2015

So I’ve been been building an international one meter. I’ve been meaning to find a place to post build photos and a more detailed build log, but here I am almost done with the hull and just now getting around to it.

The boat is a Noux IOM, designed by Anders Wallin. Anders has a lot of great information about the boat to be trawled off the interwebs, so it seemed like a good place to start.

I’ve made a lot of mistakes so far in the process having never really worked with fiberglass, wood, or a dremel before. There are a lot of build logs online with much better quality than what I’ve come up with here, and I hope to get a more polished looking boat the next time around. I didn’t think to record mistakes as I went, but here are some memorable ones to avoid repeating:

  • If a plank snaps while planking the shadows, remove it. It won’t bend properly if you just glue it back down. I had removed another broken plank and I know the superglue lets it snap off fine, but I was lazy on one and now the hull has a permanent (though nearly invisible) lump which I couldn’t quite sand out
  • Don’t use a foam brush applying polyester resin over 3/4oz glass. The glass will stick to the brush making it really hard to get a smooth finish on the first coat. Lots and lots of sanding time wasted due to this.
  • Use less resin than you think you need. My first coat on the hull was full of runs, and required a power sander! I screwed up the hull and cockpit by using too much resin. I did a pretty good job on the foredeck though after learning from my mistakes.
  • Power sanders and balsa do not get along. I did it anyway out of desperation and it all turned out okay, but I had to add way too many coats to make up for low spots.
  • Components are fragile after they’ve been taken off the stations even though they’re glassed. A few times when hand sanding I’d grip a piece too hard and hear a cracking sound… nothing visible, and I’m hoping it’ll all turn out okay. Next time I won’t need to sand quite as much because I’ll use less resin and get fewer runs.
  • Bristled paint brushes work really well for applying resin. I didn’t discover this until trying both the foam brush and a squeegee and getting bad results with both. The brush is great – and you can tip it to get a pretty good finish. It does seem like for subsequent coats the foam brush is pretty good though, as it doesn’t leave brush marks (or I’m bad at tipping). The problem with the paint brush is that it takes so long to soak it out, and the resin starts to gel before you’re done. I think my next boat will use West System 105 epoxy with 206 hardener, which will give me plenty of working time, compared to the 12 minutes I get with polyester resin.
  • 3/4oz cloth is hard to work with, but it’s what I’ve used for the whole project. As it stands right now (and I doubt this will change – I’m painting it after all!), my hull has 2 layers of 3/4oz cloth (due to how much I had to sand the first one), cockpit has 1 layer of 3/4oz, and the foredeck has 1 layer of 3/4oz. The back side of each is painted in polyester resin, without cloth. Next time I think I’ll use 2oz cloth, as without the 2nd 3/4oz on the hull it would feel flimsy.
  • Make the fin box a tad wider than you think it needs to be. I epoxied the inside of mine and joined it and the fin fit in just fine, but when fully installed I realized the fin was only fitting because the box had bent! So I had to use a file to remove extra resin from the box, while it was installed… I was a little hasty, slipped, and stabbed the hull with the file. It cracked through the glass. On the upside, just another mistake to be fixed with more sanding and more resin! Barely noticeable now that the hull is painted.
  • When joining the cockpit and foredeck to the hull, I wish I had put planks along the inside edge, hull-side. I didn’t do this, which didn’t leave much bonding surface between the two components. Because of this I put the epoxy fillet on the deck side, which was messy (I made my deck a little wide, and then sanded it down to be flush).

Planking the cockpit. I started with this, thinking I’d rather learn from mistakes on the deck than the hull.

Planking the hull. That twist at the transom is where I snapped some planks which I had to remove. Sanding them to fit and flex is key.

More planking, bow view.

Planking almost done!

Sanding. Using lightweight spackle from Ace. The spackle shows through white under the glass later on – if I wasn’t going to paint this I’d investigate balsa-colored fillers, or doing a more careful job planking so there were no gaps which required filling.

My first time glassing anything in about 8 years. I had used 6oz cloth then – much easier to work with, but that hull was way over weight.

I should have done this coat up on a table. Squatting over something on the ground isn’t the best position to think rationally as your 12-minute timer is ticking. When something goes wrong don’t forget to breath deeply (through your respirator, of course), and take a moment to think it through.

Pulled the hull off the shadows. Sitting next to the fat boat I’d given up on years ago (makes a nice decoration though).

Glassing the deck and 2nd coat on the hull. I did this one on the table – much easier to work on. I still used way too much resin on the cockpit, which was a big mistake.

Dremeled down the bulkhead to make room for the keel box. This bulkhead was actually a shadow which I didn’t mask, and kept in. Some careful aligning took place with the fin and a plum bob. I superglued the box in place once it was aligned, and then superglued in the supports. I then epoxied around the joints for strength.

Similar to aligning the keel box. I used a bbq skewer which fit the rudder log housing perfectly, and lined that up with the keel. Superglued reinforcements in place, and then epoxied for strength.

The boat lounging on the rug, showing off its fin. I bought the fin from Adrian Olson 8 years ago on my first attempt at building an IOM. It’s been sitting around ever since.

I was originally going to do a flat foredeck, but after all the work I’d put into the rest I changed my mind. It was worth doing the extra work for a beautiful foredeck. For the foredeck I used cardboard stations rather than plywood, as it was easier to cut out. I think for the hull I wouldn’t use cardboard as it doesn’t hold its shape well when pressed. On the other end of the spectrum plywood was too hard to cut to shape. Maybe I’ll use foam board next time!

Foredeck glassed up, posing with the cockpit on the hull. These three components are just sitting together and clearly need some trimming. You can see the gap under the foredeck where it meets the front of the cockpit. I ended up doing some very careful shaping here to get the pieces to mate cleanly.

Epoxying the cockpit to the hull (I did the cockpit and foredeck separately). The cardboard cutouts helped (theoretically) to hold the hull in shape, as it’d widened up from being off the stations. I don’t think this actually did anything. Next time I’ll leave some more thinly cut plywood bulkheads in place from the original planking.

Looks like a real boat if you put the camera inside!

Fitting a forward piece which will hold up the foredeck. Making sure it has enough clearance with the mast in the box. I painted the other side to waterproof.

After joining the foredeck to the hull. Haven’t taken the masking tape off yet. Kitchen scale weighed it in on target… I forget the exact number, but I think it was about 580g. I hear IOMs are supposed to be ~630g with all deck fittings. I don’t have paint or deck hatches here, so I might be a few grams over.

I sanded down the extra cockpit and foredeck to be flush with the hull. This left exposed balsa, so I masked up the edges and painted with the West System 105 epoxy + 206 slow hardener. I really like how the resin worked on this, especially how much working time it gave. On the next boat I will probably use that instead of the polyester resin for everything – it doesn’t smell quite as bad, though on a bigger job I’d do it outside anyway.

With everything all sanded smooth, I painted the hull today. Out of some moving box I built a painting station with a hole in the side for a hair dryer. I’m using a Rustoleum enamel – I hope that works out okay in the water. I’m not sure yet if I’ll put a clear coat over it. This was my first time using spray paint on something where I cared about the finish.

The deck is going to be white. I’ll be out of town for the next week, so the deck will be done in January. Then I’ll start on the electronics, which will be an Arduino uno and some Eneloop AA batteries in series.

Contact: Carole Mark
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