Design and Construction
Ibold’s 35-foot hull has a length-to-beam ratio of 2.87 and a displacement-length ratio of 439, placing it among what reviewers call ultra-heavy cruisers. Its 41 percent ballast ratio and 1.66 capsize screening value describe a form intended more for offshore steadiness than speed around the buoys.
With roughly 322 square feet of wetted surface and a long keel, the Endurance 35 is a voluminous, deeply laden boat. Its immersion rate of about 1,020 pounds per inch means it sits heavily and moves slowly through the water. The theoretical maximum speed for a displacement hull of this length is 6.9 knots.
The hull is fiberglass. Because the boat was built at several yards to Ibold’s design, construction details can vary according to where and when each hull was completed. The few hundred boats produced include Belliure’s Spanish production as well as output from other yards.
Rig and Handling
The Endurance 35 carries a ketch rig. The standing and running gear dimensions recorded for the design suggest a workmanlike offshore inventory. Jib and genoa sheets are 31.5 feet long and half an inch in diameter; the mainsheet is 78.7 feet long, also at half-inch diameter; and the spinnaker sheets are 69.3 feet long with the same diameter. Those generous sheet lengths reflect the ketch’s divided sail plan and the need to trim from a central cockpit over a long deck.
Draft is about five feet, depending on load, allowing the boat to enter most marinas despite its heavy build. The Motion Comfort Ratio of 41.7 quantifies the easy motion that its heavy displacement and long waterline confer in a seaway.
That comfort comes with the usual trade-offs. The ultra-heavy displacement and high immersion rate mean the hull responds sluggishly to sail trim and calls for a patient hand. The long keel also limits maneuverability in tight marinas compared with contemporary fin-keel boats.
Accommodations and Cruising Capacity
The design was plainly intended for extended passages under both sail and power. It carries 185 gallons of water and 71 gallons of diesel. An 11-foot beam and the long-keel hull form provide the interior volume needed for that cruising brief.
Ownership and Refit Considerations
The cautions in the record are inherent to the Endurance 35’s type rather than documented defects in workmanship. Its weight, high immersion rate, slow response, and limited close-quarters maneuverability are all characteristics of a traditional heavy-displacement, long-keel motorsailer.
Individual boats may differ in construction detail because several yards built the design. A buyer or owner should also expect period-appropriate systems and the refit demands of a fifty-year-old motorsailer, rather than one particular documented weakness.
The Verdict
The Endurance 35 is a thoroughly traditional heavy-displacement motorsailer ketch, designed by Peter Ibold and built in fiberglass with a long keel. Its figures—a 439 displacement-length ratio, 41 percent ballast ratio, and 41.7 Motion Comfort Ratio—describe a boat intended for stable, slow, comfortable cruising rather than performance.
Pros
- Ultra-heavy-displacement hull with a 41.7 Motion Comfort Ratio for easy motion in a seaway
- Long keel and about five feet of draft allow access to most marinas despite the heavy build
- Ketch rig with generous sheet lengths suited to offshore trimming
Cons
- A 439 displacement-length ratio and high immersion rate contribute to sluggish response and low speed
- Long keel reduces close-quarters maneuverability compared with fin-keel boats
- Construction details vary among individual hulls because several yards built the design
