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Repair Crazed Gel Coat. (Random Small Cracks).

If in the process of restoring the hull finish below the water line you discover some tiny cracks in the gel coat, don't be alarmed.   Hair thin cracks are usually only cosmetic surface damage.  However, wider cracks in a corner or flat area, may be a sign of hull stress.  Investigate and resolve this situation with epoxy before repairing the gel coat.  Thin gel coat cracks can be filled and sealed with Captain Tolley's Creeping Crack Cure.  This is a penetrating sealant for hairline cracks.  Both Defender and West Marine sell this well named, effective chemical.  While I have no personal experience with this product I have it on good authority from several SJ23 members that it works well.  It works just as well above the water line.  Sealing a crack prevents water from entering thereby protecting the underlying core.

Properties of Captain Tolley Creeping Crack Cure sealant. 

• One part water based acrylic polymer penetrating sealant.
• This low viscosity sealant is formulated so thin that it uses capillary action to find its way inside a fine crack and sets by water loss forming a rubbery mass that prevents further ingress of water.
• It usually takes 24 hours to cure as it air dries.
• It is recommended to apply a fill every 20 minutes till no further product is absorbed into the crack.
• Does not dissolve polystyrene.
• It can be used next to old sealant.  Dust often helps to plug a crack.
• It can accommodate a small amount of movement of the structure.
• It can resist sunlight but this is usually not a problem since the surface of the crack is so small anyway.
• It has good bond strength within the confines of a crack.
• It can be painted over because so little of the repair is exposed.
• It has good chemical resistance.

A similar product is Magic Ezy Hairline Fix.  Click here for a demo video.

GEL COAT REPAIR TIPS

NOTE 1: When doing bottom repair be wary of and check for star shaped cracks.  They might be tiny gel coat blisters.  If it's hollow, grind it out with a Dremel tool and repair the gouge with fibreglass putty.  One SJ23 member's rudder was covered with them, but they didn't show up until he removed eleven years of grunge.  Funny how good bottom paint can hide a world of microscopic damage!

NOTE 2: Sometimes a gel coat crack will continue to spread.  To stop the crack, apply a drop of Krazy Glue in the crack.  Wipe up any excess immediately.  This technique does not fill the crack or cause any discolouring.  It works well on a horizontal surface.  I think Krazy glue would be less effective on a vertical surface since it will likely run out before it can set.  On the other hand, the majority of cracks are on a horizontal surface. 

The purpose of gel coat is to create a smooth coloured finish that also protects the fibreglass from UV rays.  Gel coat is extremely thin, yet despite this, it will last a long time with soft shoes.  However, it is quite easy to remove by scraping or sanding.  Therefore when considering repair work, you should use the least intrusive technique first.  That means chemically removing a stain before you sand it off. 

Gel coat can experience three types of damage: oxidation, weather cracks or an impact gouge. 

• Oxidation happens over time with exposure to the sun.  The finish becomes dull and fades if unprotected with wax.  You can literally rub the loose stuff off, just like dust.  Try this sometime with rain water sitting on the deck.  To remove the oxidation use a marine rubbing and cleaning compound.  DO NOT overdo the rubbing.  The last thing you want to do is remove gel coat and expose bare fibreglass.
  - A word of caution about rubbing compound, it takes elbow grease to make this stuff work.  If you take your time you can have good results.  Use a clean rag.  Dirty, gritty rags will gouge the gel coat.  Don't use a power polisher. 
• Weather cracks happen when water freezes inside the pores of poorly applied gel coat.  Since this damage is usually more severe you may be tempted to take the aggressive step of sanding.  If so sand lightly with a flexible applicator like a stiff sponge.  The flex allows the sponge to follow the shape of the hull, preventing hard spots under the sanding.  If a rigid applicator is used it will gouge into the gel coat exposing fibreglass.  If you have to sand, my suggestion is to use wet sandpaper starting at 600 grit on a flexible applicator.  If kept wet, the wet sandpaper can remove a phenomenal amount of gel coat very quickly, very smoothly.  Be careful.  If the fine grade paper is too fine then move to a coarser grade.  This is NOT an excuse for not willing to use some elbow grease. 
• Gouges happen when you don't pay attention to what you are doing! 

The most difficult aspect of gel coat repair is to tint the new stuff to the same colour as the hull.  After all, you want a seamless repair.  For this you need a person who is NOT colour blind.  I know this may seem like an invasion of your skills, but younger eyes can discern colours better and yes women are generally better at it than men.  So bite the bullet and ask for help.  It's also a great way to prevent those ongoing comments about THAT lousy repair job!  By now you should have an inkling of what I'm talking about. 

• Thoroughly wash and clean the hull, rinse it off with fresh water and let it air dry. 
• Outline the repair area with a pencil so you don't repair more surface than you have to. 
• Roughen the damaged area with 100 grit sandpaper and wipe off with a solvent such as Interlux 2333N or Dupont Prep-Sol.  Do not use acetone as it is fast drying and may not keep wax or grease in suspension long enough to wipe off.  Don't touch the repair area afterwards or you will contaminate it. 
• Apply the new gel coat, having confirmed that it is the same colour as the old.  Use a very flexible putty knife.  Vinyl is usually best.  Then apply plastic food wrap over the wet gel coat, going from the center out so you don't trap an air bubble.  The plastic food warp will create a gloss finish.  If you are good at it you can use the putty knife over the wrap to smooth the finish.  Let set till cured.
• Once cured, peel off the plastic wrap and polish the repair surface with fine rubbing compound.  Flare out the rubbing around the perimeter to hide the edge.
• Wax the repair with a polymer wax.  Apply the wax in several coats.  Polish it with a power polisher.
• After a few days you can wax the rest of the hull.  Polish it with a power polisher.  This really smoothes the wax and actually makes it last longer.  The idea is to keep the pores of the gel coat filled with wax.  This is the trick to preventing oxidation, creating long life and retaining the colour.
• Click here for a demonstration of gel coat repair.

The key to gel coat maintenance is: keep it clean, keep it waxed, and repair dings in a timely fashion.  Polish no more frequently than necessary using the least abrasive compound.  If you need to use rubbing compound rather than polishing compound to remove oxidation and restore gloss, you're not washing and waxing often enough.  Please keep in mind that this Tech Tip only a general guide line.  There are more sophisticated techniques.  Repairing gel coat is not that difficult.  Making it look really good requires some artistic skills, patience and cleanliness.  The single biggest problem is to match the colour.  Good luck.
 

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