How to retrofit a hard dinghy with inflatable tubes

When a family dinghy gets overloaded, the warning usually comes on the water, not in the driveway. Frank Lanier hit that point with Melelu, an 8-foot fiberglass Dyer knockoff that had gone from handy tender to cramped, twitchy liability once two kids, a dog, and an outboard entered the picture.

Rather than replace a serviceable hard dinghy with a new inflatable, Lanier chose a retrofit that kept the hull he already trusted and added buoyancy where the boat needed it most. That is the real logic behind this kind of conversion: preserve the rowing-friendly, durable core of a hard dinghy, then build in the stability and carrying confidence that a small cruising tender so often lacks.

Why the retrofit makes sense

The appeal is not abstract. A hard dinghy rows well and stands up to abuse, but once you start asking it to carry a family, fuel, gear, and a motor, the weakness shows up quickly. The inflatable-tube conversion targets that exact problem by widening the boat’s practical footprint on the water without scrapping the original hull.

Lanier’s background makes the lesson land harder. He is a retired U.S. Coast Guard officer and a SAMS Accredited Marine Surveyor with more than 40 years in the maritime and diving industries, so the choice reads less like a tinkerer’s experiment and more like a safety-minded adjustment. The point is simple: if the problem is structural, not cosmetic, a retrofit can be smarter than a replacement.

What the Walker Bay system actually is

The conversion Lanier looked at was Walker Bay Boats’ RID system, sold as a retrofit kit for specific hulls rather than a universal add-on. For the 8-foot class, the 275R kit was designed for the Walker Bay Original 8 hull. For the larger hull, the 310R fit the Walker Bay Original 10.

The tube itself is a Variable Profile Design, or VPD, tube. In the version described in the kit materials, it is a single U-shaped tube divided into four separate air chambers, with mounting tracks, a pump, and assembly hardware. That matters because the system is built as a matched package, not a loose collar you can sling onto any small boat and hope for the best.

Good Old Boat’s “An uplifting conversion,” published as an Issue 76 project in the Jan/Feb 2011 print issue, used this same basic logic: the family dinghy had simply outgrown the family. The magazine’s archive now includes that project among its digitized back issues, which makes the conversion a useful case study for anyone staring at a dinghy that has become too small for the life it is actually living.

How to judge whether your hull is a candidate

The first question is not which tube kit looks biggest or flashiest. It is whether your hard dinghy’s shape and dimensions are close enough to the intended hull that the mounting tracks can sit where they are supposed to sit and the collar can do its job without forcing the geometry.

That is exactly why model-specific Walker Bay assembly instructions matter. They included capacity plates and parts lists tied to the specific hull, which tells you the system was engineered around fit, not guesswork. If your boat is merely “sort of” close, that is not close enough. A retrofit like this rewards careful measurement and punishes optimism.

Lanier noticed that the proportions of his own dinghy were similar enough to a Walker Bay Original 8 to make the idea plausible. That is the threshold worth copying: not “can I bolt something on,” but “does this hull actually match the conversion’s design assumptions?” If the answer is yes, the retrofit can extend the life of a good dinghy. If the answer is no, a different tender may be the cleaner buy.

What you gain on the water

The payoff shows up in the places sailors feel immediately. The collar adds reserve buoyancy and broadens the stable feel of the boat when people step aboard, climb over the tubes, or shift weight with a motor hanging off the stern. That makes boarding easier and reduces the nervous, tender-feeling roll that small hard dinghies can develop when they are loaded hard.

The 310R numbers show how much the kit changes the boat’s usable envelope. Contemporary listings say the tube kit lifted the horsepower rating from 3 HP to 6 HP and increased person capacity from 3 to 4. That is not just a spec-sheet flourish. It is the difference between a boat that feels marginal with a family aboard and one that can absorb the load without acting as if it is one wave away from protest.

What you give up, and what you still have to manage

A retrofit is still a system, which means more parts to maintain. The kit structure includes the tube, mounting tracks, a pump, and assembly hardware, and the tube itself comes in PVC or Hypalon versions. That gives you options, but it also means the collar has its own material and repair requirements, separate from the fiberglass hull underneath it.

Walker Bay’s own repair guidance stays model-specific, including warnings to use the correct adhesive and fabric. That is the kind of detail that saves an owner from turning a small repair into a material mismatch. The four-chamber layout also helps explain the practical side of the design: one damaged section does not automatically mean the whole collar loses its shape.

There is still a tradeoff in storage, weight, and complexity. You are carrying more hardware and more air management, and you are committing to a boat that now has to be maintained as a hybrid of hard hull and inflatable structure. But for a cruising boat that uses its dinghy constantly, the better question is not whether the retrofit adds complexity. It is whether that complexity is cheaper and smarter than buying a completely different tender.

Lanier’s conversion answers that question in the most useful way possible. The old dinghy was not the problem. The mismatch between the dinghy and the crew was. Add the right tube kit, respect the model-specific fit, and a small hard boat can stop being the weak link in the fleet.