Our Ultimate Guide to the International One Metre (IOM) Radio Sailing Class
The International One Metre (IOM) is the most popular and highly competitive radio-controlled (RC) racing yacht class in the world. Raced worldwide, this measurement-controlled boat strikes the perfect balance between high-performance tactical racing and affordable, strict building limits.
Whether you are a seasoned dinghy sailor looking to test your tactical skills on land or a hobbyist builder eager to construct a competitive racing machine, the IOM class offers a global community and unparalleled fleet sizes.
What Makes an IOM? The Class Rules
The IOM class is governed by the International Radio Sailing Association (IRSA) and the IOM International Class Association (IOMICA). The strict class rules ensures that racing remains a true test of a skipper's skill rather than a battle of wallets. By limiting the use of exotic materials and keeping components standardised, older hulls can remain competitive against brand-new designs.
Key Specifications Table of the IOM Class
| Metric / Attribute | Specification Rule |
|---|---|
| Hull Length | Exactly 1,000 mm (1 metre) maximum |
| Maximum Draught | 420 mm |
| Minimum Weight | 4,000 g (4 kg) fully rigged and ready to sail |
| Maximum Mast Height | 1.7 metres |
| Permitted Hull Materials | Wood or Glass Fibre (No Carbon Fibre or Kevlar allowed for hulls) |
| Fin & Rudder Materials | Carbon Fibre is permitted |
| Spar Materials | Aluminium alloy or timber |
| Control Channels | Strictly 2 channels (1 for Rudder, 1 for Sail Winch) |
The Three One-Design Rigs
To allow racing in everything from a light drifting breeze to a roaring gale, the IOM class utilises three standardised rigs. Skippers must choose the appropriate rig before a race heat begins based on changing weather conditions.
- No. 1 Rig (A Rig): The largest sail plan, used for light to moderate winds. It offers maximum surface area to catch faint breezes.
- No. 2 Rig (B Rig): A mid-sized sail plan utilized when the wind picks up and the A Rig begins to overpower the boat.
- No. 3 Rig (C Rig): The smallest sail plan, designed to keep the boat controllable and fast in heavy wind and wave conditions.
Why the IOM Class Rules the Waves
1. Pure Tactical Racing
Because the boats are limited to a simple two-channel radio system (one servo for steering and one winch to sheet the sails simultaneously), the competition comes down to boat setup and pure sailing strategy. You race under the World Sailing Racing Rules of Sailing, meaning boat preparation, racing tactics, starting line positioning, and wind shift navigation are important elements that determine the winner.
2. A Haven for DIY Builders
Unlike elite RC classes that require expensive pre-moulded carbon layouts, the IOM is intentionally friendly to home builders. Many legendary designers offer competitive plans for amateur construction. With wood or glass fibre hulls, many skippers can successfully build a race-winning club boat on a budget in their own garages.
3. Vibrant Global Community
From local weekend club meets to massive continental and global events, the IOM boasts big fleet turnouts. Major events like the bi annual World Championships routinely draw over 80 entries from dozens of nations.
How to Get Started
If you are ready to dive into the world of IOM radio sailing, the pathway is straightforward:
- Visit a Local Club: Find your national governing body, such as the Model Yachting Association (MYA) in the UK or the Australian Radio Yachting Association (ARYA), to locate an IOM fleet near you.
- Choose Your Boat: You can purchase a ready-to-race commercial boat, source a home-completion kit from a specialised builder, buy a used competitive boat from class forums, or even 3D print some of the most recent designs.
- Choose your Sail Maker: Your sails are the horsepower source of your boat and, while the main dimensions of the 3 sail suits are controlled through the class rules, every sail maker is able to use their own tweaks and ideas to design and make sails. So whether you make your own sails or choose a professional sailmaker, like CatSails with their high attention to detail, you will need to set your boat up with one of more rigs.
- Get Measured: To race in official events, your boat must be measured by an official class measurer to ensure it perfectly aligns with the strict IOM box rules and weight minimums.
The International One Metre class proves that you do not need to be sitting on a multi-million-dollar yacht to experience the absolute pinnacle of competitive sailing.
Here are Cat Components we design and manufacture many components that will help you prepare and improve your boat. Please see our extensive list of components in our Online Shop and if you have any question on how to get started or help with preparing your boat, please Contact Us
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