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View Full Version : Flex cracks in the bottom,will it float this year?



bigman
05-09-2004, 09:11 PM
My 68 18' 2+3 has flex cracks on the bottom of the boat. They are about the same on both sides, a little more pronouced on the starboard side. On the strake closest to the keel,the 90 degree angle going up to the bottom of the boat, going from the transome to the front, about 10' is cracked. Between the outside strake and the chine for about 6' it has many small cracks, this strake is fine it is just the flat surface between that is checked.I have stripped the bottom paint off and I am going to use West System's epoxy and cloth to repair these areas. My ? would be has anyone ever had to do this fix? Am I wasting my time just trying to fix these cracks as opposed to redoing the entire bottom? If I do the bottom it won't see water this year. If it makes a difference it is a barrel back. I would really appreciate any input, thanks, bigman.

Lenny
05-09-2004, 10:13 PM
I would use it this season and beef it up from the inside of hull this winter. Remember, Gel-coat, (or the paint on top of it) DOES NOT have the same flexural properties as glass. Hence why thin gel-coat can move a bit better with the glass substrate, and thick gel, like in corners of engine hatches and cockpit corners and radii shows cracks quickly. It is easy to build it up waayy past 25 or so mil in these places when spraying out a mold.

I would have fun with it one more time if it were me, and then, recore the sole this winter. Maybe a mat/roven/mat roven in this area after the coring is removed (if your's has it) and then a re-core there in 1/2 Balsa (end grain). on top of it all to boot when done. My 16 has coring on the aft part of port and starboard in the outer strake area to hull sides.

...just my opinion... :)

Morgan's Cloud
05-10-2004, 07:24 AM
Big,
How timely this question is ...

The bottom of my '66 St Tropez had the same cracks except the strakes are the one full set outer/one half set inner type.
The outer strakes had these cracks when I got the boat in 1987 and I had them checked out.. it was believed then that they were just gelcoat cracks where there was flex on the strake (single skin glass not re-inforced from behind) in what is a high stress lifting area.
Anyway.. my hull/deck/cockpit seperation resto revealed that the cracks were in fact structural and there was evidence of water weeping through the cracks over a long period. Good thing I decided to do this when I did huh ?

Well.. now about 2 years down the road, the entire hull interior (bottom) has been ground and faired. I epoxy micro light paste filled the strakes (all of them) put 2 layers biaxial fabric over the cracked/high stress areas and a fresh single skin over rest of bottom., Also now has 3 ribs over these areas that it never did.. that should take care of it for a bit ;)

I should add that on the hull bottom (outside) there was a slight concave on the bottom that coincided with the location of the cracks/lifting stress along the outer strakes ... this is all gone now . I hope to one day find out what difference this has all made !
Steve

ps.. I'm hoping that one day Lenny will come on a working holiday to Bermuda

MOP
05-10-2004, 08:08 AM
I am with Lenny! Very rarely have I ground off the gel coat in cracked area to find any damage to the glass beneath, but a little beef up internally and new gel will cure it. But for this season I would sand the area a "Little" and apply a thin coat of Epoxy, the only reason I notice you said bottom paint meaning you keep your boat in the water. When left in the water it may get a bit of water intrusion which can lead to blistering. If you were a trailer person the hull gets time to dry alleviating the intrusion damage greatly. Cracking is inevitable unless you do not use your boat at all.