Technic

Catamaran

A Technic set that actually floats, and actually makes you think about why more sets don't try that.

Brick Rated Score

3.6/5

Set 42105 · 2020

Pieces405

Minifigsn/a

Year2020

Set number42105

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The verdict

I'll be honest, the first thing that hooked me about this set wasn't the sailing, it was the hulls.

Two long, slim, twin hulls that clip together and genuinely displace water, on a Technic set, in 2020, felt like LEGO taking a real swing. Once it's built you get working daggerboards you can raise and lower and a sail rig you steer with liftarms and axles, and that mechanism has real friction in it so your sail actually holds position once you set it. But the proportions bug some builders (the mast reads short next to those long hulls), and the flexible printed sails are fiddly to seat and keep flat. If you want a Technic model you can genuinely take to a pond or a bathtub and not just shelve, this earns its place. If you want crisp scale accuracy or a big, showy build, look elsewhere in the lineup.

Best for: Technic fans who want a model they can actually sail, not just display

The full review

What it is

I've built a lot of Technic sets that promise mechanical fun and then just sit on a shelf looking mechanical. The Catamaran is different because it's built to actually do something once it leaves your table. Those twin hulls, LEGO's first attempt at a proper floating multi-hull Technic model, are the real story here. They're long, slim, and split into halves that clip together with a connection you won't find anywhere else in the catalog, and they hold together well enough in water that people have genuinely sailed these things in ponds and bathtubs.

The catch

Where it gets more mixed is in the details. The mast is noticeably shorter than a real catamaran's would be relative to the hull length, and a few reviewers pointed out there's no length ratio here that matches an actual boat, so if you care about scale accuracy it'll nag at you. The sails themselves are new flexible printed plastic sheets, and getting them to sit flat and stay seated in their frames took more patience than expected for several builders. At $49.99 for 405 pieces it also isn't cheap for the piece count, which reviewers called reasonable in the UK but a stretch in the US.

Who it's for

I'd point this at a Technic builder who wants something they can actually take outside and use, not just admire on a shelf, someone who'll enjoy fiddling with the daggerboard mechanism and steering the sail rig by hand. If you want a display piece with clean proportions or a big flashy build to show off, this isn't your set. But if the idea of a LEGO boat that genuinely floats and sails sounds fun to you, it delivers on that promise in a way very few Technic sets even attempt.

The parts story

What the build is actually like, and the pieces worth knowing about.

Building this one feels less like assembling a vehicle and more like building two small boats and then rigging them together. The hulls go together first, each one a long clipped assembly, and then you're threading axles and liftarms through the deck to build out the daggerboard and sail control mechanisms. Nothing about the build is especially hard, but the sail mounting stage slows you down since you're working with flexible sheet material instead of rigid parts, and getting it seated evenly takes some fussing.

The standout pieces are the new hull elements themselves, roughly 28cm long and 5cm wide, unlike anything used in Technic before this set, plus the new flexible clear printed sail sheets that come in around 33cm tall. For a 405 piece set the part count doesn't feel padded, most of what's in the box is doing real structural or mechanical work rather than filler. It's not a set full of rare recolors or exotic printed parts, the appeal here is entirely in the novel hull and sail elements and the fact that the finished model is built to get wet.

Fun facts

01The 42105 Catamaran was the first Technic set built as a twin hulled vessel designed to actually float and sail on water.
02Its hull pieces are new molds, about 28cm (11 inches) long and 5cm (2 inches) wide, that clip together via a connection unique to this set.
03The sails are made from a new flexible clear printed plastic sheet material, standing about 33cm tall once mounted.
04Released in January 2020 at $49.99 for 405 pieces, it was retired in December 2021 after about a two year run on shelves.