We need more air

At the Wooden Boat Show in Mystic, CT, we learned that the whistle button is the single most interesting thing on a fourteen-foot tugboat with a face. Kids press it. One kid pressed it and did not let go, and the whistle trailed off mid-note like something that had run out of breath.

Nothing failed mechanically. The horn will happily sound for as long as there is pressure behind it, and the compressor will happily refill the tank — just not as fast as a determined child can empty it. The old tank simply did not hold enough stored air to cover a sustained press, so demand outran supply and the note died out. The fix is more air: a larger tank, and a reservoir that can outlast the enthusiasm of the person leaning on the button.

The plan was deliberately unambitious: replace the existing air tank with a larger one, and leave the rest of the pneumatic system alone. Capacity was the constraint that mattered — the horn was never the problem, the volume of stored air behind it was.

While the lines were open anyway, two additions went on the list. A second whistle, on the grounds that there was no good reason not to. And a digital air gauge, so that the tank pressure is a number I can read rather than a thing I guess at.

• Removed the old tank. It lived in a simple wooden enclosure under the seat. I unscrewed the air line fittings and disconnected the wiring, then lifted the tank out.
• Built a new enclosure. The replacement tank is slightly taller than the old one, which ruled out the vertical mount the original enjoyed. It goes in horizontally to clear the underside of the seat, so the enclosure was rebuilt around that orientation.
• Added a second whistle on the roof. The air line runs to it from a tee off the feed to the original whistle, so both are fed from the same supply.
• Fitted the digital air gauge sensor to the tank and routed its wiring forward to a new gauge in the dash, so there is now a number to look at instead of a hopeful guess.

Awesome. 2 whistles, twice the fun.

If you are upgrading an air system in a space you have already filled once, learn from the following:

• Measure the clearance, not just the tank. I compared the new tank to the old one, decided it was only a little longer, and left it at that. The tank was never the problem.
• Measure every component in the system, not the one you are replacing. The compressor sits higher than the old one, and that height was what actually ran out of room under the seat.
• Check the vertical dimension of the space before you commit to a horizontal layout. I ended up mounting the tank vertically to make the height difference work, which is a fine solution but a poor surprise.