The search results provide a good amount of information.
Key Findings from Search:
- Designer: John Brandlmayr (confirmed).
- Builder: Spencer Boats Ltd. (confirmed).
- Production: 64 units built between 1960 and 1983.
- Semi-custom nature: No "standard" interior layout for the Spencer 35 Mk I due to its semi-custom nature.
- Reputation: Known as a semi-custom bluewater cruiser, many made offshore passages, including Hal Roth's "Whisper". Regarded as a "Full-keeled, Classic Blue-water Cruiser".
- Variations: Significant changes with the introduction of the Spencer 35 Mark II in 1974. The Mark II had an Airex cored hull, rather than the solid fiberglass hull of the original design (Mk I). The basic hull remained the same between MkI and MkII.
- Design Philosophy: John Brandlmayr designed many Spencer models, prioritizing stability, safety, and comfort for blue water passages (from builder article).
- Interior Layout: Due to semi-custom nature, there's no single standard layout. I'll need to find common elements or general descriptions.
- Owner Reviews/Common Problems: Owner forums (like Spencer Yacht Owners Group SYOG) are mentioned. General praise for "solid construction and comfortable motion in a seaway" (from builder article). One snippet mentions "Owner reviews include some good data". I should look for common themes if possible. I found a reference to a Spencer 35 Mk1 owner discussing interior space and comfort.
Refined Plan:
- Introduction: Use the confirmed information about its reputation as a bluewater cruiser, designer, builder, and production years.
- History and Design: Discuss the 1960 launch, Brandlmayr's philosophy (from builder article), Spencer's transition to fiberglass, and specifically mention the distinction between the Mk I's solid fiberglass hull and the Mk II's Airex cored hull, while noting the hull shape remained consistent.
- Sailing Performance and Handling: Interpret the calculated ratios (SA/D 16.34, B/D 0.35, D/L 343) qualitatively. Combine with the "long keel" hull type (from and search) and "bluewater cruiser" reputation to describe handling and stability. Grounded search didn't provide specific anecdotal handling descriptions beyond its general seaworthiness, so I'll lean on the ratios and reputation.
- Accommodations and Layout: Emphasize the semi-custom nature. Look for general descriptions of typical layouts if available. The owner's perspective mentions "plenty of space and comfort". I'll have to keep this general given the lack of specific details.
- Owner's Perspectives: Synthesize general positive reputation (solid construction, seaworthiness) from the builder article and the owner's comment about space and comfort. I don't have enough specific "common problems" to dedicate a full section to weaknesses, so I'll frame this around general owner satisfaction.
I have enough information to proceed without further search for now.