Map Notes:
Assume that Oxnard and Ventura are co-located.
Same is true for Long Beach (LB) and Los Angeles.
Note that Santa Barbara city (SBc) is distinct from Santa Barbara Island(SBI)
Full Loop is LB to SBc, to Rosa, to Cruz, to SBI, to Catalina, ending LB.
This GIF shows all eight of California's Channel Islands. The five northernmost islands are included in the Channel Islands National Park. The
Full Loop is from Long Beach to SB city, then the islands Rosa / Cruz / Anacapa / Barbara / Catalina, and returning to Long Beach after about 10 days afloat. SBI ((microscopic dot) is included mainly because crazy* Dave planned it - but since it's sorta on the line to Catalina - WHY NOT!!
A southeasterly
Half Loop would skip the northwest beat from LB to SB, instead requiring a shuttle to get the tow rig from the launch point at SB city down to the end point at LB. From SB launch this Loop would be identical to the Full Loop. However, that highway shuttle delivers "zero adventure points" and would consume almost as much time as just motorsailing up the coast ... so I think I'll do the full 360.
While the larger islands are occupied by Park personnel and open for some camping, there are zero commercial facilities. Our cruise through the Nat'l Park is like being in a wilderness setting. No fuel, provisions or services are available until the end of the cruise at Catalina. Prevailing weather is from the Pacific, west or northwest winds and currents.
The main cruise moves generally south and east to avoid the teeth of the prevailing conditions. Fagan's Guide suggests that Santa Rosa is best reached by "reaching" from SB city. Oxnard to Santa Rosa is usually a very tough upwind beat against the Pacific westerlies. Even sailing across the cut between Santa Cruz and Santa Rosa is generally predicted a pretty rough beat.
Some (or many) will prefer a shorter North Loop, see below.
ETA (edit to add)
* Dave Clark is only "crazy" because he was first to consider single-handing his 26X northwest (against prevailing conditions) from Marina del Rey to Oxnard. He did it quite successfully in summer 2003! Now, 2 or 3 others are hoping to follow him.