Towing is the operational question that defines whether a chase boat actually works in the fleet. The whole reason owners specify chase boats rather than larger tenders is that the boat is too big to stow. The flip side is that it has to follow the mothership somehow. Three options exist: tow it, run it under its own power, or carry it on a shadow vessel. This page covers towing in detail, with the loads, the gear, and the operating constraints that matter.
For broader context see what is a chase boat and chase boat range.
When towing is the right answer
Towing wins when:
- The mothership is moving short to medium coastal distances (10 to 200 nautical miles)
- Sea state is moderate (force 4 or below)
- The chase boat does not have enough range or fuel to keep up under its own power
- The route avoids open ocean crossings
Towing fails when:
- Open ocean transit is required (Atlantic, Pacific, long Indian Ocean)
- Sea state above force 5 is forecast at any point on the route
- The mothership cruises above 14 to 16 knots (most chase boats cannot be towed reliably above this speed)
- The passage is overnight without crew on the chase boat
For long ocean legs, the chase boat is either carried on a heavy lift or shipped commercially. For everything else, towing is the default.
Bridle setup
A chase boat tow uses a Y-bridle attached to the chase boat's bow towing eyes, with the apex shackled to a single tow line that runs back to the mothership. The bridle is the load-spreading element. Towing from a single bow point puts all the load on one fitting and steers the boat erratically.
Specify at hull design:
- Two stainless or bronze towing eyes, port and starboard at the bow, through-bolted to a backing plate. Minimum SWL 5 tonnes per eye on a 12 metre hull, 8 tonnes on a 15 metre, 12 tonnes on an 18 metre.
- Bridle length: roughly 1.5 times the beam. A 4.5 metre beam wants a 7 metre bridle.
- Apex shackle: forged stainless, SWL matched to the towing eye spec.
The bridle itself is usually high-modulus polyester (Dyneema or equivalent) with chafe sleeves at both ends. Stainless wire bridles are heavier and harder to handle but survive abrasion better in long-distance work.
Tow line
The tow line runs from the bridle apex to a stern bollard or dedicated towing point on the mothership. Specifications:
- Material: nylon double braid is standard. Nylon stretches under load, which absorbs shock. Polyester or Dyneema do not stretch enough for chase boat towing and risk snatch loads on the bridle and bow eyes.
- Length: 3 to 5 times the chase boat's length, adjusted so the chase boat sits on the back of the second wave behind the mothership. Wrong length and the chase boat surfs the stern wake and starts yawing.
- Diameter: 28 to 36 mm depending on chase boat displacement. Builder-supplied bridle and tow line packages are sold pre-matched.
A dedicated tow drum at the mothership's stern simplifies handling. Most yards now offer this as standard above 50 metres.
Speed and trim
Towing speed for a chase boat is normally 10 to 14 knots. Above 14 the boat starts to plane intermittently and the bridle loads spike. Above 16 you risk capsize.
Trim the chase boat slightly bow-up by:
- Filling rear water tanks
- Leaving fuel forward
- Tilting outdrives or surface drives down (water pressure helps stabilise)
Stern bias makes the chase boat want to plane, which is exactly what you do not want under tow.
Watch and monitoring
The chase boat under tow should be visible from the mothership's bridge. Specify:
- AIS transponder on at all times so the mothership tracks the chase as a separate target
- Anchor light on at night to confirm position
- VHF on channel 16 with autoresponse if the chase is unmanned
- GPS tracker independent of mainship power, in case the chase loses electrics
Some operators run a tracker like YachtTrace for redundant position monitoring on towed chase boats.
Loads
Tow loads scale with displacement and speed. Rough numbers for a planing chase boat under tow at 12 knots:
| Chase boat length | Displacement | Steady tow load | Peak load (force 4 chop) |
|---|---|---|---|
| 11 m | 8 t | 1.0 to 1.5 t | 3 to 4 t |
| 14 m | 14 t | 2 to 3 t | 5 to 7 t |
| 17 m | 22 t | 3.5 to 5 t | 8 to 11 t |
| 20 m | 32 t | 5 to 7 t | 12 to 16 t |
These numbers assume a clean tow. In confused following sea or quartering chop, peak loads spike higher. The bridle, tow line, and attachment points should be specced at least 2.5 times the steady load.
Mothership-side fittings
The towing point on the mothership matters more than most owners realise. Three options.
- Stern bollard: standard on most yachts. Adequate for chase boats up to 14 metres. Above that, single-point loading concentrates stress on the bollard and its backing structure.
- Twin stern bollards with bridle: better load spread. Required for chase boats above 15 metres in our experience.
- Dedicated tow drum with shock absorber: large yachts (70 m plus) often fit this. Pneumatic or rubber shock absorbers smooth out peak loads.
Retrofitting any of these into an existing yacht is expensive. Get the chase boat decision made before the mothership refit specification freezes if possible.
Towing in heavy weather
Above force 5 the standard advice is do not tow. The chase boat should be either lifted out, run under its own power to shelter, or carried on a shadow vessel.
If towing in deteriorating weather is unavoidable:
- Slow the mothership to 8 knots or less
- Pay out tow line to maximum length to add elasticity
- Move all fuel and water in the chase boat to mid-ships and bow
- Stand watch at the chase boat helm if crewed
A snapped tow line at speed sends the bridle whipping back at the chase boat's bow. Crew on board should never stand forward of midships during a tow.
The carry alternative
If the mothership cruises ocean legs regularly, towing becomes impractical. Two paths.
- Carry on a shadow vessel. The shadow lifts the chase aboard with a deck crane and carries it across the leg. Standard on programmes with both vessels.
- Commercial heavy-lift shipping. Companies like Sevenstar Yacht Transport and DYT Yacht Transport carry chase boats trans-ocean for around 80,000 to 200,000 euros per leg depending on route and size. The boat ships separately and rejoins the mothership at destination.
Either path is more expensive per nautical mile than towing but removes the weather and speed constraint completely.
Crew responsibility
The chase boat captain is responsible for the towing setup, daily inspection of bridle and shackles, and standing by during the tow. The mothership engineer is responsible for the tow drum and stern fittings. Both report to the mothership captain on the bridge.
Coverage of crew structure and chain of command at chase boat crew.
For broader operational context return to the chase boats pillar and chase boat specifications.