Join Date: Feb 2000
Location: Annapolis, Md
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Modify aluminum hull/keel
If you are talking about the early 1970''s (before about 1974) you are looking at IOR I boats. These were not too bad, but are a real handful to sail shorthanded or down wind. Compared to the IOR II boats that follow, IOR I are comparatively robust,stabile and slow.
The FRP in use before 1972 tended to be less prone to blistering and also more simply engineered than the boats that follow shortly thereafter. Aluminum technology of that era was extremely primitive when compared to modern alloys, welding and forming techniques, engineering, and electrolysis protection. Making things worse is that the big aluminum racing machines of that era were not designed to be long lived. They were designed to push the envelope and win races.
There are a number of things that I would be concerned with in an aluminum IOR I boat. I would be concerned about fatigue at frames, in areas where the hull plating had a lot of shaping, and near the keel to hull joint, and deck to hull joint. Many of these aluminum boats of this era had glassed over plywood decks which are prone rot. Forming and welding techniques resulted in terribly unfair hulls that would be faired using massive quantities of filler. While epoxy and microballons were coming into use, these fillers were often polyester based. At some point the adhesion between the fillers and the aluminum will give up and you can be facing a problem that makes blisters seem like a walk in the park. I saw ''Tenacious''being refaired after the Fastnet Disaster. I could not beleive how bad her hull looked before the refairing and how much material went into refairing her.