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post #1 of 6 Old 05-01-2006 Thread Starter
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Used boat advice - gelcoat cracking

I am in the process of purchasing a 1992 30" Catalina. After viewing it this past week-end I have a few concerns regarding the top deck. We observed cracking in the gelcoat in various areas around the boat. Most at the top of the forward hatch and the rest on the corner between the windows and deck.

Is this typical for the Catalina's or other boat built in the 90's? We currently own a 1980 Mirage and there are very few cracks on the top deck.

Any suggestions on this would be much appreciated.
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post #2 of 6 Old 05-01-2006
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Gelcoat cracking can be an indicator of stress related laminate damage underneath. Are the cracks deep, or merely surface crazing? If the former, it is probably a good sign to have a surveyor take a good look at it.
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post #3 of 6 Old 05-01-2006
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Spider cracks ?

I need a little more information. Are these cracks just on the surface and do they look like a spider web? If these are stress cracks in the gelcoat. For a quick fix and to stop any water intrusion, I have had good success with Captain Trolley's Creeping Crack Cure.
For a long term fix you have to clean out the crack and put a v groove in it. I have used a beer can opener. You remember these don't you? The pointed kind. Then fill epoxie filler like 3M 407, sand smoothe and paint or cover with gelcoat.

Spider cracks are usually a cosmetic thing and all boat will get them at some time.

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post #4 of 6 Old 05-02-2006 Thread Starter
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Size of cracks!

The both are straight line cracks that appear to be approximately 1 mm in width.
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post #5 of 6 Old 05-03-2006
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How long are the cracks, and are they parallel to each other?
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post #6 of 6 Old 05-03-2006
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Assume common flex/stress cracks => What is good enough?

While cracks are not a good thing you can find many OLD neglected glass hulls that have cracks, BIG CRACKS for years and they still hang togeather. Don't misunderstand me, they are not a good thing but they are seldom if ever, life threatning. IF you live in the north coutry where freezing is a common occurance it is much more of a problem as the ice expansion increases the size of the cracks every year. So, don't panic but anything you do to dry out (could of hot days in the summer) and seal up (putty, paint, or full blown expensive repair) is a good thing. However, most of the goodness is asthetic, and economic(resale) rather than life saving.

Having said all that I am assuming the cracks are the rather common flex/stress cracks that you will see on most all production boats aroung the corners of hatch openings etc. where it is hard to keep the structure from flexing at least a little bit. You should do an informal survey of boats of a similar vintage and function to see how they look. Sometimes it can happen that the builder makes a mistake or leaves out a backing plate or does a poor job fitting a bulkhead and the cracks are the first clue. In that case..... Good job sherlock, continue the investigation.

********
For more info one of the best texts is:

Fiberglass Boats
by Hugo du Plessis

Book Description
Since its first edition in 1964, owners and professionals have relied upon this classic reference to understand the many facets of fiberglass boat construction. Now completely updated, it is an invaluable, nontechnical resource for expert information on the principles of fiberglass construction, as well as sound practice. Author Hugo du Plessis focuses on the kind of boats that dominate the used market, examining fiberglass's durability, weaknesses, effects of use, and the latest research into causes of blistering--or osmosis. His advice will help owners extend the life of their fiberglass boats and prevent would-be owners from purchasing craft that are soon to fail.

About the Author
Hugo du Plessis has spent a lifetime with fiberglass. Forty years ago he was one of the pioneers, starting as a moulder and boatbuilder with a special interest in sheathing. Later he became a surveyor specializing in fiberglass boats, so gaining experience in the common defects as well as the elusive ones. He has, he says, learned something from every boat he has surveyed.
Hugo du Plessis has owned boats for 60 years, including a small charter fleet. This new edition was written on his yacht (fiberglass of course) while cruising in the West Indies

Available on Amazon used for aboutr $24 + ship. (new $40)
It is my fiberglass design/repair bible. It does not focus/dwell on mixing resin and laying fiber but on the design/stucture issues.

NOTE: Chapter 42 => "Every crack tells a story"

Last edited by sailandoar; 05-03-2006 at 11:02 AM.
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