Stress Cracks


Sent: Wednesday, November 07, 2001 4:41 PM
Subject: Re: Stress Cracks
Gary, My 1980 I36 Valhalla, has developed a couple stress cracks, one on the inside corner on the starboard side along the engine compartment and tne on the inside corner on the port side where the galley wraps around to meet the engine compartment. I was wondering if this is a problem others have experienced and is this a sign of more serious problems developing. Any insight would be appreciated.
John Boudreau




I can't quite picture where your cracks are. On most I-36s, the galley is on the starboard side, and "wrapping around to the engine compartment "(around the sink?) I think you're looking at parts of the cabin liner assembly. Typically the deck mold, which has the cockpit, and the liner with engine bed and side of the galley sink get joined with fiberglass tape along the port bunk. The starboard side, at least on our 1973 model, is joined by the plywood bulkhead at the aft end of the galley/forward end of the cockpit seat locker. I'm not even sure that bulkhead is glassed to the cockpit. Thus, I'm not sure exactly where your cracks are appearing.

I will say that our boat has hairline "cracks" in the gelcoat in places like the turn of the companionway steps where they meet the cabin floor, most of the cockpit flat surfaces, the trim edge along the cabintop between the monkey rails and the edge, and around the big mounts for the traveler.

Our boat has been raced hard, first by a previous owner out of Florida, then for 8 years on Lake Michigan by me, and 15 years of cruising and year-round sun exposure on San Francisco Bay. I've talked with my yard, whom I trust, and their diagnosis is that it is simply aged gelcoat that gets brittle and cracks with the normal working of the boat.

The solution is to take off all the hardware, grind down the deck surfaces and re-gelcoat. About $20k. I've seen one boat where that was done, and she looks beautiful. We've chosen to live with the cracks!

I did discover a few years ago that Tilex Mildew remover (the spray stuff you get at the supermarket) works beautifully for getting the black that forms out of the cracks , particularly during the winter. It does a great job of cleaning up the fiberglass. But, be careful because where the Tilex drips it leaves a very nice white, clean streak. I learned to use a "green pad" to apply and contain it - rub it on, let it sit about 5 minutes while you keep going on the next part, then hose it off with plenty of water. Be careful not to get a heavy concentration running over the topsides through a scupper or you might find a clean streak down your topsides! This "heavy duty" treatment also takes off any wax you’ve applied, so a re-wax job should follow.

A lighter grade solution, used this winter, is adding 1-2 cups of regular laundry bleach to a bucket of West Marine’s Boat Soap. It seems to have removed the winter mildew and not completely removed the was. It has stayed clean for about a month now.

The only other thoughts are that you might have loose engine mounts or have gotten out of alignment and getting excessive vibrations which could cause a crack. But I would think you would notice this whenever the engine is running. I'm assuming that you did not have any of those "things that go bump" experiences which might have caused cracks.


Don't know if that helps, but it's fun to talk about.

Rick Van Mell

Vanishing Animal




From: Raymond Cranston

Sent: Thursday, November 08, 2001 9:21 AM
Subject: Re: FW: Stress Cracks


I have similar cracks in my 1974 Islander. The boat is in the third year of a 3 year refit project to prepare it for an extended Carribean cruise. I have used a Canadian yard for the repairs. They have looked at the boat extensively and feel the cracks are nothing to worry about. They tell me they see these type of cracks often in other makes of boats as well.

Causes include temperature variations throughout the year and the inner floor not expanding and contracting at the same rate as the other glass around the engine compartment.

The yard's recommendation was that they do not affect the floors integrity but would do the repair if I decided to have it done for cosmetic reasons. Since we are putting in a teak and holly sole this winter the area will be covered.

Prior to the refit starting I used a product called Crack Cure that I purchased through Boat U.S. It sealed the cracks but discolored the area where it was applied. Good Luck.





Sent: Thursday, November 08, 2001 12:39 PM
Subject: Re: FW: FW: Stress Cracks

The discoloration from Crack Cure can be removed with turpentine. I have no idea why it works.

Brian Jacobs



They're comestic if merely through the gelcoat, but if the crack is entirely through the laminate, that's a different matter.

I had two cracks appear in the liner of the starboard cockpit locker on my I36, starting at the edges and several inches long. That fabrication is rather thin, 1/8"" maybe, and a lot of heavy objects have been thrown in there at one time or another.

Such cracks will only get longer if not taken care of because the live end of the crack is a stress concentration point. The "cure" is to drill a 1/4" or so hole centered on the end of the crack to spread out the stress concentration there. Not pretty, but effective. Be careful not to drill into the hull whilst doing so!

Mark Wyatt



From: Jim Garrison

Sent: Saturday, December 01, 2001 4:58 PM
Subject: Stress Cracks

I have similar "stress cracks" on my 1978 Islander 36. I hesitate to use the term stress cracks because it usually makes me think of something tiny and the cracks on Raspberry Tart are not exactly tiny.

They are at the starboard forward edge of the engine liner just at the battery area.

When the boat was surveyed last March I had a special interest in this problem. The surveyor was able to determine that the cracks began quite some time ago because they had been touched-up cosmetically and it was clear that the touch-up was probably at least 10-years old. The cracks did not appear to be getting worse and the surveyor did not feel
that they posed any structural problems.

My theory is that the engine liner did not fit exactly flush on the hull. When the liner was fitted to the hull it bent and put the piece under stress. The subsequent flexing of the hull caused the liner to crack at the weakest point - the corner of the battery area. - Just a

Jim Garrison
Raspberry Tart
TEL 650-726-3848
FAX 650-712-9608

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