Conference unifix::sailing

Are cracks in gel coat normal? To some extent, yes. Should they happen?
No. 

Gel coat cracks, as I understand it, because the underlying laminate is 
flexing. Gel coat is rather brittle and cracks rather than bend. Cracks 
are most common near sharp bends (eg, cockpits) or where fittings are 
bolted to the deck (eg, stanchions, pulpits). The laminate flexes 
because it is not stiff enough to resist the loads being applied. These 
loads can be either mechanical or thermal (expansion/contraction due to 
temperature differences).

This has a couple of implications. First, every material will eventually
fail if flexed often enough. This is called fatigue life. I have seen an
article that claims that some of the latest racing boats reach their
fatigue life very quickly (a couple of years). Second, if a boat is
flexing in normal weekend sailing, one might question its strength in 
bad weather. The cracks in the Catalina are probably not cause for 
concern, but Catalinas are not intended for offshore sailing, either.
When a surveyer looked at our deck a year or so ago, he expressed 
surprise at finding only one crack in the gel coat -- he indicated that 
he normally finds quite a few.

Alan

PS I hope the pulpit is through bolted with backing plates, not screwed 
to the deck!

    The cockpit crazing I find "normal" but I'd check a little further
    on the pulpit crazing. You might want to ease up a bit on lifeline
    tension. I'd check the forward bulkheads to make sure they're still
    firmly glassed to the hull. You might also call the Catalina plant.
    And then depending on how much you trust your dealer you could talk
    with them about it.
    
    Have you talked with other owners to find out what their experiences
    have been? This would seem like the quickest way to establish what's
    "normal" for your boat.
    
    Ed

    Sounds like some one has been jumping up and down in your cockpit
    and bumping things ( other boats or docks ) against the bow pulpit.
    An 85 boat seems pretty new for sponatneous grazing if there is
    such a thing.  I own two "mature" fiberglass boats both of which
    probably rate as ripe banannas(bananas? - you know, the yellow things)
    by contemporary cabon fiber - kevlar racing boat standards.  The
    larger of the two ( an E22 ) has a center console which supports
    the mainsheet block, vang, several other controls and the combined
    weight  of the three person crew when the heels, which it usually
    does a lot.  The laminate hehe is only about 1/8 to 3/26 inches
    thick.  Not very thick and it flexes like it wants to leave the
    boat in a hurry when the wind and waves come up.  I'd expect this
    to be crack city but there isn't anything on it.  On the other hand,
    I've encountered grazing on the fiberglass portion of the keel just
    above the lead casting.  Ordinarily you can't much stiffer than
    this since the laminate here is about 1 1/2 to 2 inches thick. 
    It seemed  just another ding from a wayward lobster pot but after
    a few minutes of sanding my finger pushed right through the glass
    into a void big enough to swallow a golf ball.  This wasn't hard
    to repair (lots of gougeon and chopped glass) but I've gotten into
    the habit of checking any grazing by pushing on it with a stiff
    tool(screwdriver or knife) to check for any underlying voids.
         The cockpit has a lip all around which is about 3 inches wide.
    This flexes when I lean on it but the only grazing seems localized
    in places where I've dropped things like spinnaker poles and hammers.
         The other boat is a 25+ year old interclub dingy which is dry
    sailed.  It gets used during the winter in a frostbite racing fleet
    and is launched from a rockly beach.  Given the temperature of New
    England water in the winter, most of the sailors chose to get the
    boat as high and dry as possible before getting out.  Needless to
    say 25 years of "USMC" style beach landings has left its impression
    on the hull.  There probably isn't a square inch of hull under the
    waterline that doesn't have cracks in it.  But, the hull doesn't
    leak or flex any more than the newer boats.  When I first got the
    boat it offended my esthetic sensibilities to have so many cracks
    and I wasted several weekends trying to cover them up.  A friend
    who bought a similarly afflicted interclub sprayed it with new gelcoat
    and wet sanded so it looked new.  After half a season of slow sailing
    he sold it.  Seems he couldn't coax any speed out of the boat. 
    Now I just fix any new cracks that appear (very few - no more room)
    before Fall (Fall?) put in time.
         If you've done all that the others have recommended and haven't
    found any voids in the layup or structural defects, it's easy although
    time consumming to cover the cracks.  Widen the crack, sand the
    surrounding gelcoat so there a very slightly depressed area abutting
    the undamaged part, fill with marine-tex or the polyester paste
    made for this, cover with wax paper, and wait til it dries.  Peel
    off wax paper and sand flush.  Repeat if needed and then wet sand
    with succesively finer grits and rubbing compound til you're satisfied.
    If your hull isn't dead white there are tints available but mixing
    and matching is an iterative process.  Before getting a quote from
    a yard  I've found it worthwhile to ask myself if I can get a part
    time low skilled job paying $35/hr after taxes.  The answer does
    amazing things to my esthetic sensibilities.

    Another thing is consider with gelcoat crazing is whether the situation
    is getting worse or not. On my boat, a 21' Florida Bay hen cat rigged
    boat, their were gel coat scars from the time I bought it [new].
    the dealer says its a result of sloppily pulling the laminate off
    of the mold, not a result of in-water flexing.  After this season,
    its first, the gelcoat looks just as it did the day i bought it,
    and now the dealer is fixing up the original problems.
    
    good luck
    joe

    I am looking for ratio of catalyst to gelcoat. The only thing I could find
    on the net was 
    
    temp	drops per oz of gelcoat
    
    80-90	15
    70		25
    50-60	50
    
       Do these look right?  It has been a while since I last mixed a batch
    and I have lost my mixture ratios.  
    
    
          Thanks
    
          john