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Repairing Hairline Cracks

Repairing Hairline Cracks
Ever wondered what causes those annoying fine cracks in gelcoat? And more importantly how do you make them go away? Read on to find out about an easy solution to this age old problem.

What causes gelcoat cracks?

Hairline cracks, stress cracks or spider cracks (star cracks) that occur in gelcoat surfaces on fiberglass boats or other water craft are often seen as a cosmetic issue. In most cases this is true, however it is important to seal them correctly otherwise water may penetrate into the fiberglass and cause more serious damage. Most stress cracks occur in the gelcoat layer of fiberglass surfaces and can be repaired by yourself. If structural damage is suspected, you should get your boat inspected by a qualified boat repairer. These problems occur as a result of:
  • Manufacturing defects
  • Environmental challenges
  • Stress and movement
Also, older fiberglass boats tend to have a thicker application of gelcoat which means they are more susceptible to cracking. Stress cracks first appear as very fine hairline cracks. Over time, the cracks get larger and the structure may begin to delaminate and/or blistering starts to occur. The main causes are:
  1. Swelling of the resin due to water diffusion
  2. Wave action and rigging stresses
  3. Direct sunlight or thermal shock on darker colored gelcoat can cause warping, delamination and blistering
  4. Impact
  5. Expansion or contraction

How do you tell what the cause is? By the pattern of the crack:

  • Radial cracks  (spider cracks, star cracks) – caused by impact or by a fixture / bolt that puts strain on a certain area of a boat and cracks occur around the hole.
  • Linear crack – caused by flexural strain
  • Thermal fatigue cracks –  when gelcoat repeatedly expands or contracts. These might be in a parallel pattern or a non-directional pattern

How to avoid gelcoat stress cracks?

Spider cracks can be avoided by countersinking holes just through the gelcoat, so the load is placed on the structural fiberglass rather than the brittle gelcoat. There’s also a great article on how to drill holes correctly to avoid chipping and cracking in fiberglass. Quite often however, it’s near impossible to prevent these unsightly cracks due to the fact gelcoat is so brittle and rigid.

How to repair gelcoat cracks

One quick and easy way to repair gelcoat stress cracks yourself is by using MagicEzy Hairline Fix – A purpose built DIY repair solution for stress cracks in gelcoat and fiberglass. MagicEzy Hairline Fix is a one-part, pre-tinted (available in 10 colors) sealant that allows you to complete the repair in seconds without having to grind out the existing damage. It requires absolutely no tools and once complete the repair is guaranteed to last by MagicEzy. Watch the video below to see just how easy it is.

MagicEzy Hairline Fix

Below are real before and after images of a MagicEzy Hairline Fix repair taken from the Bayliner Owners Forum. MagicEzy-Hairline Fix-Before-After-BOC Image source: www.baylinerownersclub.org/index.php/forum/general-boating-topics/55481-crazing-repair-before-and-after Here is another one courtesy of the BoaterEducation Forum Hairline-Crack-BF-AF Image source: http://www.boatered.com/forum/topic.asp?TOPIC_ID=164951  

48 Comments

  1. Terry Gee on September 28, 2015 at 5:17 pm

    Treebranch has broken the surface of the back of our caravan causing an indentation the size of a twenty cent piece. Part of the surface has been pushed in. Will magicezy be adequate to fix the hole?
    Terry.

  2. MagicEzy Customer Service on December 18, 2015 at 2:36 pm

    Hi Terry,

    I would recommend using MagicEzy 9 Second Chip Fix for this sort of damage. If possible I suggest removing any loose bits of material with a file or dremel tool before applying the MagicEzy product.

  3. Steve Wyatt on March 17, 2016 at 5:58 am

    I need some of that in baby blue and royal blue

  4. MagicEzy Customer Service on March 17, 2016 at 11:32 am

    Hi Steve,

    Thanks for your comments. MagicEzy Hairline Fix comes in 2 shades of blue – Royal Blue and Navy. You could easily mix a baby blue by combining royal blue with a tiny bit of Snow White.

  5. Kyle Kellogg on April 5, 2016 at 1:24 pm

    Had some spider cracks show up on my bass boat over the past season. The gelcoat is black with flake in it, what color would i use? Is midnight what you consider black?

    Thanks

  6. MagicEzy Customer Service on April 5, 2016 at 1:26 pm

    Hi Kyle, Yes Midnight (Black) Hairline Fix is what I suggest for repairing the cracks you are describing. If you have an image of the cracks, please send to info@magicezy.com and we can take a closer look at it for you.

  7. Burt on May 17, 2016 at 12:51 pm

    I have an older boat with a variety of cracks. If I fill the cracks with Magic Ezy, can they later be covered with gelcoat or Awlgrip if I need to make the color uniform?

  8. MagicEzy Customer Service on May 17, 2016 at 2:06 pm

    Hi Burt, generally we do not recommend over-coating with other products, simply because we cannot be sure of the chemistry compatibility. You could always test in a small inconspicuous area before applying more liberally.

  9. Jose on July 27, 2016 at 8:35 am

    Would this product be recommended for below the water surface?

  10. Michael on August 11, 2016 at 5:20 pm

    Have you heard of anyone ever applying your product to the gelcoat of their glider? Any feedback from them? I have a “Discus CS” (you can paste into google images to see an example).

  11. MagicEzy Customer Service on August 12, 2016 at 11:29 am

    Hi Michael, I’ve had a look at your glider and for a cosmetic repair, I can’t see why MagicEzy wouldn’t be suitable. Strong adhesion, flexibility and UV inhibitors mean the MagicEzy repair will be strong and durable. At this stage we have not heard from other glider owners about using MagicEzy.

  12. Ansgar on August 24, 2016 at 2:40 pm

    I have a variety of spider cracks on the hull of my club 420 (sailing dinghy). The color is white, but since the boat is a bit older it has turned to a sort of creamy white. Personally I don’t really care for aesthetic appearance, but should I use fiberglass stain remover first to clean it off and then use a more bright white? Or should I just go for the creamy white color.

  13. MagicEzy Customer Service on August 25, 2016 at 11:41 am

    Hi Ansgar,

    In your situation I always recommend the MagicEzy Snow White colour. Before applying the product use a cutting compound (polish) to bring back the orginal white around the damage and then blend in to the rest of the boat.

  14. Michelle on August 28, 2016 at 8:32 pm

    Hi I have hairline cracks in my tiles due to the house moving and I also have chips the tiles are white polished marble like a grey vein running through them what colour would you advise thank you for your help and time.

  15. MagicEzy Customer Service on August 30, 2016 at 2:15 pm

    Hi Michelle,

    Thanks for your question. For your tiles, I’d suggest using Matterhorn White, which is a very light grey colour.

  16. MagicEzy Customer Service on September 26, 2016 at 2:59 pm

    Hi Jose,
    We avoid recommending it on surfaces that will be permanently under water due to some environmental laws in certain parts of USA.
    However, as long as MagicEzy is fully cured (to be safe I would allow 1-2 weeks out of the water) to allow it to fully cure before putting back in water temporarily it should be fine.
    I hope this helps

  17. Ed Harbour on December 18, 2016 at 7:24 am

    I have a 1987 33 CAL sailboat with gelcoat cracks and crazing on the cabin house and walkways. The boat is a two color egg shell. Should I purchase the Oyster & cream. Are they generally the colors utilized on older boats?

    Ed Harbour

  18. MagicEzy Customer Service on December 19, 2016 at 2:06 pm

    Hi Ed,

    Provided the cracks are only the width of a hair I would try to apply only Oyster first and see if it blends from the normal distance.

    Hairline cracks stand out once black colored dirt gets in them once they return to approximately the gel coat colour they usually blend in well.

    Please let us know if you have any other questions or concerns by emailing info@magicezy.com

  19. Joseph Gehrke on January 22, 2017 at 12:56 pm

    I have small spider cracks in my Bayliner. I looked at your colors but none seem to match mainly because all the lite ones all look the same to me. I would like to send you some photos with the contrast between a white sheet of paper and my boat colors, BUT, I can’t find a way to send them???

  20. MagicEzy Customer Service on January 23, 2017 at 4:25 pm

    Hi Joseph,
    Please feel free to email info@magicezy.com with any photos and we will do our best to help you. Please also see http://magicezy.com/hairline-fix/ for images of light coloured boats for your reference.
    You can also mix two colours of our Hairline Fix product together so if in doubt you could purchase Snow White (the purest white colour we have) and also midnight (matt black) and blend the two together to get an exact match if you are up for the challenge.
    Please do not hesitate to email us if you have any more questions,
    Thanks and all the best

  21. Justinj on February 28, 2017 at 10:50 am

    Hi i have a new fibreglass bath with white gelcoat. It has developed a pair of very fine parallel cracks on inside edge. Do you hav a product that would make them not so noticeable thankyou

  22. MagicEzy Customer Service on February 28, 2017 at 11:03 am

    Hi Justin, this sounds perfect for our Hairline Fix product – please see http://magicezy.com/hairline-fix/ for more details and to find out where to buy. Wishing you all the best

  23. Walford on March 21, 2017 at 9:24 pm

    Hi I have hairline cracks on my 1998 touring caravan, would this product fix the cracks .Many thanks
    Walford.

  24. Emily on March 22, 2017 at 6:12 am

    Hello, we have a diesel pusher with fine cracks in the gel coat. Is this product okay to use on an RV?

  25. MagicEzy Customer Service on March 23, 2017 at 11:26 am

    Hi Walford, yes our Hairline Fix product would be ideal for hairline cracks in a Caravan. Please see http://magicezy.com/hairline-fix/ for more information and where to buy. Wishing you all the best

  26. MagicEzy Customer Service on March 23, 2017 at 11:28 am

    Hi Emily, yes our Hairline Fix product is ideal for fine cracks in an RV. Please see http://magicezy.com/hairline-fix/ for more information and where to buy. Wishing you all the best

  27. Chuck Sztroin on April 26, 2017 at 2:49 am

    How would you mix the Magnum Dream White color?

  28. MagicEzy Customer Service on April 27, 2017 at 4:53 pm

    Hi Chuck,
    Apologies Magnum Dream White is not a colour we are familar with – are you able to provide us with more information? Please email info@magicezy.com
    Please also visit the ‘examples of popular colours for boats’ section on http://magicezy.com/hairline-fix/ for help differentiating the difference between our white colour options
    I hope this helps

  29. P. Draper on May 12, 2017 at 4:11 am

    I am wanting to fill the hairline cracks on my trailer but I am then going to paint the trailer with Marine paint. Can I prime and paint over your product?

  30. MagicEzy Customer Service on May 15, 2017 at 11:52 am

    MagicEzy is quite compatible with other products however we do not know what ingredients are in every paint. Our primer MagicEzy Mega Fusion is fully compatible with our other products (ie Hairline Fix) so you can use the two together with no problem. We would suggest you complete the Hairline Fix repair, wait two days for it to fully dry then try a small patch test. If you would like any more information or have any other questions please email info@magicezy.com. Wishing you all the best

  31. Tami on May 22, 2017 at 11:47 am

    Would this product work for stress cracks on the bottom of my fiberglass shower?

  32. MagicEzy Customer Service on May 22, 2017 at 12:12 pm

    Hi Tami, yes MagicEzy Hairline Fix is designed specifically for stress cracks in fiberglass so it would be perfect to use in your shower! Simply apply according to instructions, allow to dry for at least two hours then cover the repair with clear (sticky) tape for the next 48 hours to allow it to set without getting wet. Find out more about Hairline Fix here http://magicezy.com/hairline-fix/
    If you have any other questions or require any assistance please feel free to email info@magicezy.com
    Wishing you all the best

  33. Sean Tiffin on May 30, 2017 at 1:00 am

    Will the oyster white work on an older sailboat deck? Couldn’t see the actual colours on here so guessed.

  34. Sean Tiffin on May 30, 2017 at 1:02 am

    Will the oyster white work on an older sailboat deck? The deck is white but faded. Could not see the actual colours on this site so I ordered 3 tubes of the oyster.

  35. C. McPherson on June 4, 2017 at 11:54 pm

    I have a light grey Awlgrip finish on the deck of my boat , over non skid . I have some cracks and crazing in areas, but none of your colors match. Can they be blended, can the tubes be reused, and how long does one have to blend the colors, if possible? Thanks.

  36. Greg Gunn on June 7, 2017 at 2:54 pm

    Do you have a New Zealand distributor.

  37. MagicEzy Customer Service on June 8, 2017 at 12:13 pm

    Hi Sean, we have emailed you a response, however please see http://magicezy.com/hairline-fix/ for example photos of boat colours,
    Wishing you all the best

  38. MagicEzy Customer Service on June 8, 2017 at 12:14 pm

    Hi Sean, we have emailed you a response, however please see http://magicezy.com/hairline-fix/ for example photos of boat colours,
    Wishing you all the best

  39. MagicEzy Customer Service on June 8, 2017 at 12:16 pm

    Yes, all of our colors can be blended together to make a perfect match for your boat. Try mixing midnight (black) with a white or cream depending on your boat – they can be mixed easily in a small zip lock bag until you get your perfect color. The tubes can most definitely be re-sealed and as long as they are kept in a cool environment they will last for years. I hope this helps, if you have any more questions please feel free to email info@magicezy.com
    All the best

  40. MagicEzy Customer Service on June 8, 2017 at 12:19 pm

    Hi Greg,
    Our original three products (9 Second Chip Fix, Hairline Fix and Mega Fusion) can be purchased from Burnsco in New Zealand. Please visit http://magicezy.com/find-a-stockist/ and put in your suburb to find the closest store to you.
    Our newest products UV Shield and Tile Fix can only be purchased online at this point in time however can be shipped to New Zealand. Please see https://www.nanotechrepairs.com/ to shop online
    All the best

  41. Dan Burke on June 21, 2017 at 10:50 pm

    The photo of the tubes show 4 white to beige colors.
    I have a Silverton from 1985 and it’s off white ( oyster)
    Can I get the colors and do you use a Pantone chart for comparison ?

  42. MagicEzy Customer Service on June 22, 2017 at 12:55 pm

    Hi Dan,
    Please see http://magicezy.com/hairline-fix/ for a full color chart plus images of the most popular boat colors.
    If you have any more questions or concerns please feel free to contact us at info@magicezy.com
    All the best

  43. David Clark on July 22, 2017 at 1:21 pm

    I have a fiberglass hood on my car that is painted vermilion red. Can this product be used to repair the cracks around the hood pins?

  44. MagicEzy Customer Service on July 25, 2017 at 2:39 pm

    Hi David,
    MagicEzy Hairline Fix is designed for use on fiberglass cracks so it should work perfectly on your hood. If it is a bright red we would suggest you use our Strawberry color, however the colors can be mixed together to create the perfect color for you. Please see http://magicezy.com/hairline-fix/ for more information including where to buy.
    Wishing you all the best

  45. Nancy on September 4, 2017 at 7:16 am

    I would like to use this on a few hairline cracks on the crosshatch textured bottom of my fiberglass tub. Would this product work? Would 48 hours be enough time to wait before getting it wet? The website mentions somewhere waiting 14 days before getting it wet, but it is my only bath/shower. I don’t think the duct tape over plastic would work due to the surface being highly textured.

  46. John on September 4, 2017 at 8:53 am

    I have a 37 year old canoe that has crazing every direction from bow to stern. How much product would I need to repair a 16 ft canoe and will this stand up against the constant flex of use?

  47. MagicEzy Customer Service on September 4, 2017 at 2:01 pm

    Hi Nancy,
    Yes, Hairline Fix is perfect for use on fiberglass. The repair will be touch dry after two hours. Full strength is ACHIEVED in 2 weeks. We suggest that after 2+ hours cover the repair with clear scotch/sticky tape. Keep sealed for 2 weeks until full strength is achieved. if you are worried about the water getting under the tape simply towel dry the area after you use the shower for those first two weeks.
    If you have any further questions please email info@magicezy.com. Thanks and all the best

  48. MagicEzy Customer Service on September 4, 2017 at 2:09 pm

    Hi John,
    In short – A little goes a long way and you will be surprised just how much you can repair with one tube. There are many variables which can influence how much you will need, but generally, one tube of Hairline Fix will repair 15-20 6 inch long stress cracks.
    Please remember before you begin the repair that MagicEzy products require a clean surface or they will not adhere to their full potential. Solvents remove grease very well but misses cleaning dust and grime. A few drops of Kitchen Dishwashing detergent in a cup of water is all you need. If the chips looks dirty or black use a paint brush to agitate inside the chip. To finish, rinse out the hole with fresh water and allow to dry before repairing.
    MagicEzy products have ultra-strong adhesion that provides tough, long-lasting repairs while remaining flexible. If you follow the instructions we guarantee that MagicEzy Hairline Fix will provide a strong, long-lasting repair for at least 3 years or your money back. This is all possible due to the advanced technology used in the production process.
    I hope this helps, if you have any further questions please email info@magicezy.com. Wishing you all the best