Build Log – Vantage 475T: Nemesis – Small Trimaran

These pages will show the build log of our Vantage 475T project as we start with an old ISO dinghy as a test bed and then make it into a trimaran and then finally replacing the IS Ohull with our own main hull.

The main premise of the build is to have a fast, safe small boat that can be used in different ways depending on the weather, who is coming sailing and how we feel that day.

We have some sailing experience with small dinghies and catamarans and really enjoy both types of sailing. We only have limited storage locally so the max length we can work with is 4.75m so the ISO fits the bill ideally. They are old designs now but back in the 90’s were at the forefront of bringing the skiff sailing paradigm to the general sailing public.

For a test bed I had various criteria I needed to work to:
I wanted maximum sail area, power and speed for as little cash as possible.
The ISO has a Portsmouth Yardstick number of 924, only marginally slower than a 29er or a UK Cherub. The 29ers are 50cm shorter, with less and seem to sell for £3000 to £8000 in the UK. I felt they would be a bit too small, underpowered and hadn’t got the money – simple. A UK Cherub is a over a metre shorter, has a large sail area but not easily found and certainly not cheap although they are lighter. ISO’s are ten a penny – or one for £900 in fact but that included 2 masts and several sets of sails (2 almost new), a great road trailer and the dolly trailer. Couldn’t go wrong really?

A dinghy that was tough
ISO dinghy’s are known as tough boats and although 30 years old this one was in fine shape with no soft spots.