NAVIGA Mini Eco: Rules, Boat Specs and How to Start Racing
NAVIGA Mini Eco is the small electric group-racing class of NAVIGA Section M: freely built boats with a submerged propeller, at most 430 mm hull length, at least 450 g ready to race, a battery of at least 140 g and an energy limiter set to 21 Wh. Three to six boats race anticlockwise around a triangle, and whoever drives the most laps in the race time wins the heat. This page sums up the 2024 rules, what a competitive boat looks like and how to get started.
By Kyle HilsonUpdated: November 20267 min read
This article is part of the RC Boats guide. All rule figures come from the NAVIGA M class Rules 2024 (valid from 1 January 2024). NAVIGA updates battery and energy values once a year, so check the current rulebook and annexes on naviga.org or with your national federation before you build.
From the workbench: SwellRC’s author Kyle Hilson mostly races boats in this class (he calls it Mini Eco Expert) and builds many of his boat parts himself. The rules below are quoted from the rulebook, not from memory.
What is NAVIGA Mini Eco?
NAVIGA is the international federation for model ship building and model ship sport; its Section M covers powered racing models. The Eco classes are its entry point into electric group racing: several boats on the water at the same time, a buoy course and lap counting, rather than one boat against the clock.
The rulebook defines Eco and Mini Eco together as freely built model racing boats with electric underwater propeller propulsion. Hydro and Mono drive units and surface-piercing drives that stick out beyond the hull are not allowed. Mini Eco is the small version: same racing format, a shorter and lighter boat and a smaller energy budget. The full-size class appears in older rule sets as Eco Expert.
Why the class is popular with club racers: there is no restriction on the motor, the hull is free design, the boats are small enough to build on a kitchen table, and the energy limiter keeps the racing close, because a faster boat that wastes energy runs out before the end.
Mini Eco boat rules at a glance
| Rule | Mini Eco | Eco (for comparison) |
|---|---|---|
| Hull length | max. 430 mm | free |
| Minimum weight, ready to race | 450 g incl. start number plate | 1,000 g |
| Drive | Submerged propeller only | Submerged propeller only |
| Motor | No restriction | No restriction |
| Minimum battery weight | 140 g | 360 g, no maximum |
| Power cable | 30 mm of at least AWG 16 (1.5 mm²) to each pole | 30 mm of at least AWG 12 (3.3 mm²) to each pole |
| Energy limiter | 21 Wh (1260 Wmin) | 60 Wh (3600 Wmin) |
| Boats per heat | 3 to 6 | 3 to 6 |
Source: NAVIGA M class Rules 2024, general safety rules and class rules for Eco / Mini Eco. The weight is checked in ready-to-race condition, including receiver, battery, cables, connectors and mounts. Loose buoyancy aids such as foam blocks or balloons are not allowed unless they are a permanent part of the boat.
Which batteries are allowed, and what does the energy limiter do?
Only NiMH, LiPo and LiFe cells may power the boat. At the voltage check a LiPo cell may not show more than 4.23 V, a LiFe cell 3.65 V and a NiMH cell 1.42 V; a higher reading counts as overcharging and the racer is disqualified for that heat. Only one set of batteries may be used per heat, and the pack must be easy to reach for checks.
Since 1 January 2024 an energy limiter is mandatory in all Section M classes except F1 and F3. The limiter sits between battery and motor controller and cuts power once the set energy has been used; for the Mini classes that is 21 Wh. The ramp-down time is set to 5 seconds. In practice this turns Mini Eco into an efficiency race: prop, hull and throttle use decide whether you still have energy on the last lap.
- Swollen (“ballooned”) cells must not be pressed back into shape and should not be used again. On a second offence the racer is disqualified.
- Batteries may only be disposed of in the approved containers at the event.
- Packs that are water-cooled must stay a solid block even without the cooling plates.
General LiPo handling is covered in are LiPo batteries dangerous? and how to charge a LiPo battery.
Kill switch, hull colour and numbers
- Kill switch: a loop of red cable that anyone, including the rescue boat crew, can pull to cut power. Factory connector pairs such as XT60, XT90 or T-Deans are allowed with a red wire loop of at least 20 mm diameter. It may not sit on a lid or other removable part.
- Receiver switch: with a separate receiver battery the boat needs an on/off switch operated from outside the boat; with a BEC no extra switch is needed.
- Hull colour: bright and in contrast to water on at least one third of the bottom and the top, so a capsized boat is easy to spot. Dark colours such as black or deep blue are not allowed, and all-white does not count as contrasting.
- Registration number: a permanent number from your national federation, black on white, 20 mm high, fixed to the hull, not to a lid.
- Race number shield: 80 × 80 mm, white, black number 70 mm high, mounted vertically at the back and visible from both sides.
- Two boats: you may register two models per class; both carry the same registration and race number.
How does a Mini Eco race work?
The race runs on the NAVIGA triangular course (Annex C1 of the rulebook), anticlockwise. The start line runs straight to the uppermost buoy.
- Racers stand on the platform in race-number order; the order is reversed in the next heat.
- Each boat lies in the water with its stern touching the landing stage.
- An acoustic signal from the Platform Judge or the lap-counting computer starts the heat.
- A late starter whose rivals have already reached the bottom-left buoy must start towards the bottom-right buoy without hindering the others.
- The boats drive as many laps as possible in the race time set in Annex A1.
- Rounding a buoy on the wrong side costs one lap per buoy. You may not turn back to correct it.
- Broken-down boats are picked up by the rescue boat at the end of the heat, unless a boat is sinking.
A race has 3 or 4 heats; the two best heats are added up, and the six best racers go to a final that decides the result. The rescue boat always has right of way: touching it means disqualification, or a one-lap penalty if the judge rules the touch accidental. Radio systems on 2.4 GHz are allowed in all classes.
Juniors up to age 12 may race the Mini classes and the Eco classes, but may not act as start assistants.
What is Mini Eco Team?
Mini Eco Team is the relay version for Mini Eco boats. A team has two or three racers and at most three boats, built to the Mini Eco rules. Only one boat per team is on the water; the next one may start only when the dead boat is in the rescue boat. A team may use three sets of batteries, may not charge during the race, and each member drives only their own boat. Hitting the rescue boat disqualifies the whole team.
What does a competitive Mini Eco boat look like?
Because the hull is free design, there is no single standard boat, but the rules push builders in a clear direction:
| Part | Why it matters | What to aim for |
|---|---|---|
| Hull | The 430 mm limit and 450 g minimum fix the size | A light, stiff hull that reaches 450 g with the battery placed for balance, not with dead ballast |
| Prop and drive | Energy is capped, so efficiency wins | Submerged prop, true-running shaft, several props to test |
| Motor | No restriction | A motor that is efficient at the current you actually draw, not the hottest one |
| Battery | At least 140 g; energy capped at 21 Wh | A pack that holds voltage across the race time |
| Rudder and turn fin | Laps are won in the turns | A boat that holds a tight line around the buoys without scrubbing speed |
Wiring, servo choice and propeller balance are covered in how to wire an RC boat, model boat servos and how to balance an RC boat prop. Motor basics are in model boat electric motors.
How do you start racing Mini Eco?
- Find the national model-boat federation affiliated to NAVIGA in your country and a club that runs Section M events.
- Go to a race as a spectator and look at the boats on the bench. Racers usually explain their setups.
- Get the current rulebook and the annexes (race time, battery values, course drawing).
- Build or buy a hull that fits 430 mm and plan the layout to reach 450 g without ballast.
- Fit an approved energy limiter, a kill switch with a red loop and a bright hull colour before your first event.
- Practise starts and clean buoy turns. A missed buoy costs a full lap, which outweighs a slightly higher top speed.
Racing in the US often follows NAMBA or IMPBA rules instead; see RC boat racing for that format.
FAQ
How long can a NAVIGA Mini Eco boat be?
The hull may be at most 430 mm long (NAVIGA M class Rules 2024).
What is the minimum weight in Mini Eco?
450 g in ready-to-race condition, including the start number plate. Eco boats must weigh at least 1,000 g.
What energy limit applies to Mini Eco?
The energy limiter is set to 21 Wh (1260 Wmin) for the Mini classes except Mini FSR-E. Values can change once a year, so check the current annex.
Is the motor restricted in Mini Eco?
No. The rules place no restriction on the electric motor; the energy limiter and the battery rules do the balancing.
Can I use a surface drive or a hydro drive?
No. Eco and Mini Eco boats must use an underwater propeller; Hydro and Mono drive units and surface drives that extend beyond the hull are not allowed.
What happens if I miss a buoy?
Each buoy rounded on the wrong side costs one lap, and you may not turn back to correct it.
More on this topic: the complete RC Boats guide covers hull types, power systems, radios and where to run.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
