Join Date: Jul 2002
Thanked 4 Times in 4 Posts
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Deck to Hull fastening....
John, the main reason many high volume, ''price-built'' production boats lack the kind of hull-deck layup you prefer is simply due to the sequence of construction. The boat''s hull is finished out after which the deck is fitted, so full access to the hull-deck joint from the interior of the boat is at that point impossible. Instead, a wide range of alternative attachment methods are used including mastic, bedding compound, or fiberglass slurry in combination with some form of mechanical fastening - from pop rivets to stainless screws being driven into an embedded aluminum strip (boat builders don''t often lie awake nights thinking about dissimilar metal issues like we boat owners...). Often, the mechanical fastening is done to insure the chemical bond or to supplement it, rather than being the primary source of strengthening as with thru-bolted deck systems.
This is why boats like Hallberg Rassy deserve praise for the method they use: place the deck onto the hull, totally fiberglass over the hull-deck joint on the inside, then grind and finally paint the entire inside of the boat...and only then transport it to the boatyard (from the molding factory) where the boat is actually built out. That provides not only for a totally dry joint but means everything going into the boat (tanks, engine, etc.) can fit thru the companionway opening - a real advantage some years later to its owner when things start needing replacement.
The one famous boat I can remember reading about that had its hull-deck joing glassed over was Hal Roth''s WHISPER. After a Pacific circle, during which they suffered endless joint leaks, Hal ground down the original joint on the outside (a mastic seal with thru-bolts, as I recall), and then glassed the outside of the joint with 1", 2", 4" and finally 8" glass strips, as memory serves. It was a lengthy, tiring process (imagine the grinding...!) that in the end produced a watertight and stronger joint. Acknowledging that he could criticize the builder for need ing to do this, he instead points out the financial balancing act any builder faces between doing things for ''power users'' like the Roths vs. producing something affordable, which the Roths also needed. He describes this in his _After 50,000 Miles_ book, a good read even today despite the dated nature of some topics discussed.