Stress cracks on top of hull

Hi there,

Would be ultra helpful if someone could shed some light on these stress cracks that has appeared on the top of both hulls of my Hobie 16. It stretches on for 2-3 feet and is right at the bow which seems odd as the only time we would put pressure there is when we are using the beach trailer and have to push down on the front. No soft spots and the rest of the hull has no stress cracks. We’ve had the boat for a year and loving it, it’s in good shape and is about 15 years old.

Not sure if these are just cosmetic cracks and whether I need to repair it?! Any advice appreciated!

Thanks!
Vanessa

As is often the case, your pictures didn't come through. There's instructions on adding pictures somewhere, but I've never had any luck with it. Without pictures, and probably even with pictures, it might be hard to figure out how bad the cracks are.

The very first thing I'd do is put the boat on the ground, preferably pavement. Start with lifting each hull separately by the bow, watching the crack very carefully. Does the crack(s) expend or contract? Have someone watching from the side and have them observe the hulls to see whether the hull doesn't lift evenly, both along the deck and the keel. If one hull lifts but the other hull does not, don't worry. It's an issue but only towards performance and some difference is common to most boats.

Stretch a string from the bow to the stern on the top of each hull, making it as tight as possible. Measure very carefully the drop from the string to the hull. Lift each hull by the bow and then from the stern. Measure very carefully the drop and see whether there is any change.

In both of these lifts, you can rest the bows on a block of wood while you're checking the crack(s). What we're looking for is whether the cracks are causing any flex in the hull. If there is any flex, I'd be extremely hesitant about trying to fix these hulls. This is a high load point on the hulls and if they break, you'll have the mast down and be sinking very quickly.

On the bright side, the cracks are probably confined to the gelcoat. Take a narrow blade such as a knife, and put into the cracks to see how deep they are. My guess is the blade will only go down maybe an eighth of an inch. Further checking would involve choosing one section (probably the worst area) and grind it out, going down to where the crack disappears. If you're lucky, you're not into the glass and all you've got is a gelcoat problem. Grind out the crack and patch with one of the many repair kits that are out there.

If the crack goes into the glass, then the problem is worse and more expertise is required to fix it. If the hull(s) are not flexing, it's doable, but experience helps. I'd find someone local who knows glass work to give you some advice after seeing it.

Jim Clark-Dawe

As said above - pics aren’t showing up.

Hairline stress cracks are somewhat common on Hobies. Usually they’re located towards the outer edge of the deck, right along the transition between the smooth and non-skid surfaces. This tend to be a hard spot in the hull due to the strength of the hull/deck joint so if the deck flexes a little, it will stress along that edge. Generally not a structural issue, but since the gelcoat is brittle compared to the reinforced fiberglass below, it will develop a haiine crack.

If this is the case with your boat (again, no pics), then its probaly fine and if the hull is otherwise firm and not taking on an excessive amount of water, I wouldn’t be concerned. You could grind out the crack and re-gelcoat, but the likelyhood is that it would eventually return.

sm

Image posting: https://www.hobie.com/forums/viewtopic.php?f=18&t=8574

Just has to be hosted on a public site. Copy the URL into your post and use the IMG tags front and end of the URL.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Thanks both, sorry for the late response. I really appreciate your answers. I will check the hull this weekend for flex. Fingers crossed...

I’ve also managed to get photos up in my original post.

Thanks again will report back!!

Vanessa

Thanks for the pictures. I had imagined the cracks running across the hulls, not the length of the hulls. These cracks won't cause flex. They look like the cracks that SRM described, running just inside lf where the hulls are attached on the opposite side from these cracks.

My guess is these are surface cracks. You can check this with a knife or other sharp instrument. A single edge razor is ideal.

I agree with SRM that you could grind these out and re-gelcoat, but quite honestly, I won't. As he said, a good chance they'll reappear, and it would be a lot of work to produce a reasonable looking result. I'd simply monitor and see what they do over time. If, in the unlikely case the cracks are in fact showing a structural problem, it's going to be very difficult to repair.

Jim Clark-Dawe

In the pictures, it appears like the hulls have been painted over the gel coat.
Is this true? If so, then this could be just stress cracks in the paint caused
by shrinkage. Drying out caused by sitting in the sun. Just thinking out loud.
I see bubbles. That's what makes me think it was painted. And with bubbles,
the paint was not applied properly and will soon start peeling off all over the
place.

Greg 1984 H16

I had cracks exactly like these in my 1986 H16. The boat had some hull slop/flex in it when I got it but no soft spots in the hulls. I did the epoxy frame-to-pylons job and the boat is solid as a rock now. A friend of mine has a 2017 H16 and the cracks have started showing up on his boat too. It seems that they are just surface cracks in the gelcoat. Cosmetically, the cracks bugged the heck out of me, so I used a toothbrush to scrub out the dirt and grime, then I mixed up some gelcoat and thinned it a little with acetone. Rubbed the tinned gelcoat into the grooves and wiped off the excess. They virtually disappeared.

I've sailed and raced the boat for about 4 years now since doing the repair, and the cracks have not shown up again.

Hope this helps!

My hulls on a 2008 boat are exactly the same
On purchased the boat last month and my assessment was gel coat only.
I will be doing some scrubbing and whatsch here for any solution suggestions.