Posted: Oct 10, 2013 - 10:36 AM
The major changes that occurred to the H18 over the years were to the hull construction and to the rudder system. The hulls were made lighter in the mid-1980's (about 1984 to 1986). There were some catastrophic hull failures at the front crossbar connection if the hulls were not reinforced with fiberglass and the upgraded stainless steel anchor plates. These hulls are easily identifiable by a "red glue" which can be found at the seam line between the deck and hull. Later boats went back to a more robust hull construction.
The other major change was an upgraded rudder system which came about around 1987. The new system is easier to adjust and less likely to have kick-up failure which could result in hull or rudder damage.
A boat built in the late 70's would have the older, sturdier hull construction. None the less, check the hulls for cracks or damage under the deck lip where the crossbars attach. Otherwise, give everything a good inspection since you're looking at around a 30 year old boat, pretty much everything is suspect. Major things to check are condition of hulls for cracks or soft spots, condition of all aluminum components (especially crossbars) for signs of excessive corrosion, condition of sails, and overall completeness of the boat. Expect to purchase new standing rigging and shroud anchor bolts if the previous owner can't tell you how recently those items have been replaced.
sm