This is LEGO set 42105 - Catamaran from the LEGO Technic theme with 404 pieces, which came out in 2020.

This set is a fantastic set. The build is a lot of fun and the catamaran really floats. The sails look amazing and I love how the steering mechanism was made for them. This boat also looks great with the blue and lime green colours, and it's a great model to display on a shelf.

All in all, this set is an awesome set and I would HIGHLY recommend you to get this. You can find this set on eBay and BrickLink for sure. Here is the link where you can check out the full gallery I made for this set on my website: www.klokriecher.de

Videos I made of this set:

Stopmotion

Review

Speed Build

We bought this model specifically for use in studying Newton's laws for our science curriculum and this model made for a fun build as well as a great demonstration of the various forces involved in the motion of a sail boat. Specifically, I wanted to teach the kids the concepts of Newton's laws, apply them to a sail boat, demonstrate the counter-intuitive idea of a sail boat moving against the wind, and then test the theory. It also doesn't hurt that it's a great-looking model and the last Lego boat I owned was #4020 so I was overdue for a new one. So, how does this boat purchased "for science!" hold up?

Form

The finished model looks great and thanks to the size, really feels like you get a lot of model for your money (especially at 20% off, which it can easily be found at). As pointed out in the main review, it does not display very well due to it having to balance on its rudders and the hydrofoils. The colors and form of the model are striking and the potential is there to build a single-hull model sail boat. Any set that immediately inspires ideas for alternate models and modifications gets a few extra points in my book.

Function as a Lego Set

As a Lego Technic model, it's mostly a success. The rudders are a bit loose and don't quite line up properly (they don't want to naturally stay parallel to each other and the mechanism, while stiff enough, has a bit of play and isn't the best design). The hydrofoils lift up and down, each with their own worm gear system. This can be a little tedious to use, especially for non-child sized hands where the cranks are a bit small and hard to grasp, but they other than that work fine. The controls for the sails work great and are easy to use and as Technic sets go, these are all unique functions you won't find in your typical car or motorcycle.

Function as a Model

Were this simply a model boat I would have been disappointed but since it's Lego, with a minor modification, the experiment went just fine. Since this is a hydrofoil design, it doesn't really function all that well in water. I was not familiar with the concept of a hydrofoil catamaran, but it was nothing Youtube couldn't make sense of. In short, the hydrofoils do little until the boat gets up to speed. Being a Lego model, this boat would never get up to the speeds required, and so (besides being the wrong shape), the hydrofoils are strictly for looks in this set. No problem, though. 15 minutes later, they were upgraded using some spare parts to the highly-aerodynamic and beautifully color-coordinated 6x12 plates you see so elegantly mounted here.

The hulls come apart into two pieces and snap together firmly. There are no obvious gaps when assembled, but they are not what you'd call sealed. After our experiment, they did have a little water in them, but not much. I imagine it would stay afloat indefinitely in perfectly calm water, but being tossed around as a child might do, they'd eventually take on too much water. I would not consider this to be a bath tub toy.

Overall

Overall it's a fine build, with functions you won't find in other models, and an excellent look. Not perfect, but a nice model which lends itself well to tinkering and experimentation thanks to its floats-in-water capability. I'm a little disappointed that the boat does not really function properly out of the box, but after modification of the keel, our experiment was a complete success. The kids were able to adjust the sails and apply a wind force with a flex-straw (also shown) and the boat moved against the wind, just as Newton's laws predicted it would.

Introduction

Hi there, my name's Leo and this is my review of the LEGO set 42105, Catamaran. I'll be going through the overall building experience, variety of parts, playability and functionality, and value for money. Let's begin.

Building Experience

The building experience was average, and some parts were quite fiddly and took quite a bit of work to get into place, such as the sails which were a nightmare to get to stay in place. Taking the model apart was also pretty difficult with some of the pins not budging, and it sure took some of the skin off of my fingers, though I suppose this is to be expected with technic models. Therefore, for building experience, I award a 3.

Parts

In terms of parts, there was a decent array considering the number of pieces in the model, and I think it would be unfair to expect more variety. For this reason, I rated parts a 3.

Playability

Now moving on to playability, this is what really lets the model down. The model features many levers and moving parts that educate you on how a catamaran really works, however in the water, it is almost impossible to do anything with the model. Not only is it unstable and flimsy, but the supposedly airtight floats at the bottom also were not aligned properly which allowed water to enter the model at the front. There was no way to realign these as the two pieces do not move. This led to the model sinking within about a minute of playtime and me having to drain the water back out. Adding to the problems is the fact that it is not very stable in the water. It features two extendable legs which reach into the water and are supposed to offer stability, though they are so thin that they barely help and the only thing really keeping the boat afloat and partially stable is the aforementioned leaky floats. Therefore, with all of these issues adding up, I found it impossible to use most of the features whilst in the water, only really being able to see them in action out of the water on a table. This is extremely disappointing as the whole model is based on being a floating boat that works in the water, and therefore I give playability a 1.

Value for Money

Finally, value for money. Although this model has its problems, it is still great value for money, with an RRP of just £34.99 and at the time of writing, a new value of just £26, I think it is very cheap for a technic build and great if you want to learn about how boats like this work and get to use it in practice. It also features a second boat model which makes it slightly more worth the money. I'm sure not all sets will have the same errors as mine and the opportunity for other builds is there, so I have given the value-for-money as a 4.

Conclusion

Overall, this is a very mediocre build, with some very promising aspects, some of which don't exactly work as advertised, though it is great value for money. It is not anything special and has its drawbacks, although is saved by its low price. Overall, taking in all the factors discussed, I believe the most suitable rating for this model based on my experiences to be a 3.