However, I have found the factory installed shrink is usually only readily available on certain size loop connectors, not all sizes. I have found it difficult to locate it for spade connectors (does it exist?) and in the smaller sizes.
Unless you have noticeable or extreme vibration, which is not common on sail
boats, or on large wire connections that use lugs, the spade is the way to go - loosen the screw, slip on the spade and tighten.
Yes large rings and spades are available in factory made heat shrink. However, you will most likely only ever find "safety spades" or "captive fork spades". Safety spades are written into the ABYC standard as the ONLY acceptable spade connection. Straight spades, the ones without the bent up safety tips, should be avoided on boats!
Ancor is NOT the only manufacturer of good quality heat shrink connectors. I buy from AMP, FTZ, 3M and Ancor and I've never not been able to find the terminal I needed..
ABYC, Nigel Calder, Don Casey, USCG and other industry insiders and experts would all disagree with you about sailboats NOT having vibration issues. Perhaps, if you feel that sailboats don't exhibit vibration, you have not spent enough time, off shore, in rough weather. I can assure you that when your boat literally falls off the face of a wave that there is CONSIDERABLE vibration and strain to every component on the boat including cabinetry, wiring, tankage, engine, rig, plumbing and more. Vibration is one of the main reasons the ABYC and other experts, in the industry, suggest "safety spades" , "strain relief" & a "mechanical connection" other than solder alone among other safety precautions......
Some Nigel quotes:
"Cables in boat use are subject to vibration and, at times, considerable shocks. Solid-cored cable of the kind used in household wiring is liable to fracture. Stranded cable must be used on boats."
"Cables need: strength to resist the vibration and pounding experienced in boats, adequate insulation to prevent ground leaks, and sufficient size to minimize voltage drop."