Decks & Superstructure
Mid Size Power Boats
A Guide for Discreminating Buyers
by David Pascoe
In the chapter on hull construction we learned that decks aren't just for walking on and to keep the water out, but are an integral part of the hull structure, or at least should be.
Decks are the horizontal bulkheads of the boat. The significance of this is that decks are usually subjected to a lot of stress, and unless well designed and constructed, may end up showing the effects of that stress, often in unexpected ways.
While it may be hard to imagine why anything should ever go wrong with a fiberglass deck, the truth is that things often go wrong with decks.
Most frequently the problem involves the core, for virtually all decks in modern boats are cored by necessity. For over forty years balsa was the standard material for deck coring that has served us well, except . . . .
Except when the laminate is breached in one way or another and water gets into the core. Being wood, balsa can rot over time.
When balsa rots, it essentially disappears or is reduced to mush so that the end result is two thin fiberglass skins with nothing between them.
When you walk on it, the deck is apt to feel soft and spongy. It defects or gives way. If this progresses far enough, pretty soon hardware starts pulling off and massive leaks occur into the interior.
But long before it reaches this stage, telltale signs begin to appear. Surveyors rarely miss this sort of problem on a pre purchase survey since it is so easy to locate.
Trouble with deck cores almost never presents a problem that has to be fixed to a boat owner. In most cases he doesn't even know the problem exists, or chooses to ignore it.
The reason all this is important to boat buyers comes at resale time when the problem is discovered by the buyer's surveyor. Then, it becomes a big expensive problem for the owner just at the very time he thought he was done with the boat and whatever problems it had would be passed on to someone else.
Deck core problems usually kill boat sales so you don't want to end up buying into a problem like this.
So far, foam cored decks have proved fairly trouble-free, though while foam stands up to water intrusion better than balsa, the long term effects of water intrusion are largely unknown. Fortunately, we don't have the problem of hydraulic erosion of deck cores that we do with bottoms.
Incomplete bonding occasionally turns up in cored decks. Incomplete bonding is distinguished from voids by virtue of size.
Often called neverbonds, these are voids, albeit very large ones that result from very sloppy work. Since very few production boats are vacuum bagged when cored, especially when foam is used, decks are apt to contain a number of voids.
Depending on how well the lay up crew does its job, there may be only a few voids or many of them. This is one reason why I recommend that new boats should be surveyed. This is one of those cases where hull #125 may be defect free, while hull #126 is riddled with voids. Surveyors have various techniques for finding voids.
(Additional spaces are added for easy screen reading.)
Table of Contents - Chapter 7
Gimmicks and Weird Stuff
Where Does the Water Go?
Rope or Chain Locker
Deck Problems With Express Cruisers
Windows & Frames
Helm Stations Generally
- A Guide to Discriminating Buyers
by David H. Pascoe
Publisher: D. H. Pascoe & Co., Inc.
David Pascoe - Biography
David Pascoe is a second generation marine surveyor in his family who began his surveying career at age 16 as an apprentice in 1965 as the era of wooden boats was drawing to a close.
Certified by the National Association of Marine Surveyors in 1972, he has conducted over 5,000 pre purchase surveys in addition to having conducted hundreds of boating accident investigations, including fires, sinkings, hull failures and machinery failure analysis.
Over forty years of knowledge and experience are brought to bear in following books. David Pascoe is the author of:
- "Mid Size Power Boats" (2003)
- "Buyers’ Guide to Outboard Boats" (2002)
- "Surveying Fiberglass Power Boats" (2001, 2nd Edition - 2005)
- "Marine Investigations" (2004).
In addition to readers in the United States, boaters and boat industry professionals worldwide from over 70 countries have purchased David Pascoe's books, since introduction of his first book in 2001.
In 2012, David Pascoe has retired from marine surveying business at age 65.
On November 23rd, 2018, David Pascoe has passed away at age 71.