Great Loop Bridge Clearance Guide

Written and maintained by TheCenterOf editors. Last reviewed: 2026-05-29. This page is planning guidance, not navigation, legal, insurance, mechanical, or safety advice. Verify current charts, bridge notices, lock schedules, marina terms, weather, insurance language, and local rules before making a departure decision.

Who this is for

Use this page if you are shopping boats, measuring your current boat, or trying to understand why air draft keeps appearing in Great Loop planning.

It is written for conservative route planning, not for squeezing under structures with heroic confidence.

How to use this guide

Read it once for the big idea, then come back with your boat details, intended start month, crew style, and rough budget in front of you. Great Loop planning gets much clearer when each page is tied to a real decision instead of treated as general inspiration. If a section makes you uneasy, that is probably the section worth turning into a checklist, phone call, measurement, reservation question, or shakedown exercise.

The best use of this page is not to memorize every sentence. The best use is to identify which parts of your plan are still soft. A soft plan is not a bad plan; it is simply one that still needs verification before the boat, crew, money, and calendar are committed.

If you are comparing options, write down the tradeoff in one plain sentence. For example: “This choice saves money but adds docking stress,” or “This route is prettier but depends on a better weather window.” Clear tradeoffs are easier to manage than vague preferences.

Keep those notes with your route plan so future decisions can build on the same logic.

Planning questions to answer

• What assumption are we making here because it is convenient, and how can we verify it?
• What changes if the weather, marina availability, repair timing, or crew energy is worse than expected?
• Does this decision still work for the smallest normal crew on board, not just the most experienced person?
• What is the backup if the preferred stop, bridge timing, lock schedule, fuel dock, or anchorage does not work?
• Are we choosing the option that makes the route calmer, or the option that merely looks better in a plan?

Air draft is the real boat

Published specs are a starting point, not the final answer. The real air draft is the height of the boat as it will travel: antennas, radar, mast, arch, hardtop, canvas, dinghy storage, solar panels, lights, and anything else above the waterline. Used boats are often modified, so two boats with the same model name may not have the same clearance.

Measure the actual boat in realistic cruising trim. If the arch folds, know how long it takes, who can do it, what tools are needed, and whether it is safe to do repeatedly.

Why margin matters

Bridge boards, water levels, wind setup, tide, river stage, wake, load, and measurement error can all affect the real clearance situation. A plan that depends on inches may be technically possible and still unpleasant. Some crews are comfortable with tighter margins than others, but everyone benefits from knowing the real number.

The Loop is long enough that a repeated anxiety becomes a lifestyle problem. If every low bridge feels like a bet, the boat may be controlling the route more than you expected.

Bridge clearance checklist

• Measure from the waterline to the highest fixed point in normal cruising trim.
• Record a second number for the lowest practical travel configuration if equipment can be lowered.
• Label antennas, canvas, mast, arch, and electronics that change the number.
• Keep the measurement available at the helm and in the trip notes.
• Verify low-bridge sections with current charts, notices, bridge boards, and local information.
• Do not let online anecdotes override current conditions in front of the boat.

What to consider when buying

The conservative rule

A bridge-clearance plan should make boring sense. Know the boat. Know the water. Know the structure. Know the fallback. If any of those are uncertain, slow down and verify before turning a planning problem into a contact sport.

Related Great Loop pages

Great Loop Starter Guide · Route Overview · Seasons · Budget · Boat Requirements · Boats Under 40 Feet · Great Loop Trawlers · Locks

Before acting on this page

Turn the advice into current facts. For route movement, that means current charts, Notices to Mariners, lock and bridge information, weather forecasts, marina confirmation, fuel availability, and local knowledge where appropriate. For boat decisions, that means measuring the actual boat, reviewing maintenance records, checking insurance language, and testing whether the crew can handle the boat when conditions are not perfect.

A Great Loop plan should be specific enough to guide the day and humble enough to change when better information arrives. That balance is the difference between useful preparation and false confidence.

How this page was built

This guide was written as an editorial planning aid for Great Loop and boating readers. It combines common route-planning principles, practical cruising tradeoffs, and TheCenterOf's existing Great Loop content structure. It is intentionally conservative: when a decision depends on current conditions or official rules, the page points readers back to verification instead of pretending a static article can be the final answer.

Corrections, updated links, and first-hand route notes are welcome through the contact and corrections page.