weird bubbles in my gelcoat

Hi all,

Since last week, small bubbles have popped up in the gelcoat of my Nelo 550. The bubbles are all on the seam between deck and hull and appeared almost overnight on several regions of the seam, front left, front right, near the cockpit and at the rear, too.
Any idea what this could be?





To make matters worse, just after I was done taking pictures and had put the ski back in its quilted protective cover, a wind gust picked it up and dropped it from the garden table into the grass. The only visible damage was a 10cm strip of seam that came loose (last picture). Is it just a coincidence or a sign that the seam as a whole is not adhering so much to the rest of the boat?



I emailed the dealer here in the Netherlands (if you are from around here, Arjan Bloem). They usually offer very good service and they sent me the address of a good repair shop in their neighborhood and proposed to take the ski to them first if I preferred. They are, however, closed until the end of the month.
I'll bring the ski tot them to see what they can do in early February (the ski was bought in December 2012, so I am hoping the warranty could cover a part or all of the repair - to be seen).

But I thought I could use the time to educate myself on the issue before going there. Any expert here that could shine a light on what's going on?
Could it be osmosis? In case it matters, it has been very mild winter here so far with a lot of rain the last 6 weeks. The ski is stored under a bike shed in a protective cover, but not entirely dry.
Many thanks in advance for any insights.

Nelo uses paint rather than gelgoat, so yes those could be osmosis bubbles, though the location is unusual. Usually osmosis bubbles happen in an area that is wet constantly such as when water gets trapped under a seat pad or under some tape. In my experience the bubbles can disappear over the course of a few days of hot dry sunny weather once the tape or padding is removed.

Hi Zach,

Thanks for the reply.

So, you'd advise me to just fix the damage at the front and leave the bubbles for what they are until summer?

Nelo uses paint? My 520 is definitely gelcoated, but it's 10 years younger than OPs, not sure if things changed since then.
A Think Evo I had had paint.

Indeed, on my WWR 550G2, the seam is clearly gelcoat.
Nelo's method to create this invisible seam is to have an internal seam and a thin layer of gel coat on the outside.

If the repair falls out of warranty, I planned to first suck some epoxy in the seam, and then cover with a new layer of gelcoat. An maybe put a new Nelo sticker over the repair to hide it, if needed...

I'll probably leave the bubble alones and hope they disappear in summer.

If I were to DIY these bubbles I would be inclined to puncture/grind off one of them to see what's going on there. If it's a cavity in the gelcoat it wouldn't be a big deal to fix especially that you will be repairing the seam and will have the gelcoat already mixed up and ready to go. If this is something under gelcoat you probably want to see what exactly what it is and if it's structural in any way.

To my knowledge epic, fenn, stellar, and carbonology use gelcoat. NK, nelo, ozone, and think use paint. I owned a nelo 550 g2 that was definitely paint. I believe the nelos are made in some sort of neutral color and then they are painted once a customer picks the color they want. I don’t think gelcoat can bubble like that as it is a thicker more rigid substance once cured. I have seen vinylester gelcoat flake off when it separates from the epoxy based cloth underneath. But then again, maybe things have changed, and I am just a customer without insider knowledge. I would ask your dealer.

zachhandler wrote:

To my knowledge epic, fenn, stellar, and carbonology use gelcoat. NK, nelo, ozone, and think use paint. I owned a nelo 550 g2 that was definitely paint. I believe the nelos are made in some sort of neutral color and then they are painted once a customer picks the color they want. I don’t think gelcoat can bubble like that as it is a thicker more rigid substance once cured. I have seen vinylester gelcoat flake off when it separates from the epoxy based cloth underneath. But then again, maybe things have changed, and I am just a customer without insider knowledge. I would ask your dealer.

I did a couple of gelcoat repairs on different 520 (current gen), both certainly gelcoated.
Not sure if the factory offers custom/paint options, but all the dealer had in stock was boats each gelcoated uniformly and with large stickers. Base colors were white, grey, blue and red, all gelcoat.

I know the same dealer offers some customization for K1 boats, can't recall how they do that for sure, but suspect its some sort of vinyl wrap.

Maybe some nelos are gelcoat and others are paint? The only think ski i have is actually made with gelcoat because it is a jet made for a kids program and they wanted extra durability. And it either has a ton of gelcoat or maybe an extra layer of glass in it because it weighs about 17kg. It feels indestructible.

If it doesn't leak and is not structural, then why bother to fix it?

fitz wrote:

If it doesn't leak and is not structural, then why bother to fix it?

Well, couple of reasons actually:
1. Vanity, mainly: I like my gear to look good
2. durability: i doesn't leak now, but not repairing it means it will be more likely to leak where the seam is exposed
3. reselling value, down the line
But, all in all, vanity, basically

Hi all, With the first onset of spring over here and a couple of dry days (we haven't seen a lot of those in Belgium since the beginning of the year), I finally got around to fixing my Nelo 550's cracked gelcoat seam.I bought a RAL 9016 gelcoat kit (including hardener) online and it was only a matter of of one hour prepping, sanding down and applying gelcoat, letting it cure overnight and sand down the repair afterwards.Overall, easier than I first envisioned and certainly doable for a beginner at this kind of stuff. Some before-during-and-after pictures below for other beginners to see how final results would look like.

Pretty happy how it turned out.

Beautiful repair! Looks invisible. Was that gelcoat purchased from nelo? Usually it is very hard to match white gelcoat. Also I am still curious - do you think the whole boat is gelcoat, or is it just gelcoat on the seam as a cosmetic filler and then the rest of the boat is paint? What happened to the bubbles on the hull? Are they rigid or flexible? Did they eventually flatten out on their own?

Hi Zach,

Thanks.
In person, the repair can still be spotted, but one has to know it's there and look closely. Good enough for me.

The boat is definitely gelcoated. There was another defect on the bow deck, like a stone chip where the gelcoat thickness could be observed. Also that disappeared nicely when repaired.

As predicted by others on the forum and by the dealer, the bubbles on the seam are disappearing now the weather is getting drier. It was probably some humidity retention due to the constant rain here during winter and the fact that the boat is kept outside in a Burnham cover. First time it happens in ten years, though. On the other hand, this winter was the first time in 20 years we had groundwater well up in the cellar...So much for global warming...

Bubbles were rigid to the touch, but I did not dare prod them too hard, for fear of having another repair on my hands. After all, I'd rather be paddling than repairing gelcoat...

So on the deck chip was it a thick layer of green gelcoat or a thin layer of green paint over white gelcoat? I think you are saying it was green gelcoat from surface down to the composite fabric.

Yes,
It was thick white gelcoat (only the nose is green on this ski). Id say about 1 mm thick. The underlying layer was black: black resin, carbon layer?I am not sure how the deck is laid up.

The ski is WWR lay-up, mind you. If weight needs to be reduced, there is more potential around my mid-section than on the ski...

My guess is that they make the boats with white gelcoat sprayed in the mold, then do a coat of paint over the gelcoat to achieve all of their color and design options. I think that would explain the apparent osmotic bubbles. I don’t think gelcoat forms osmotic bubbles, and i think gelcoat is stiff enough that it would crack if it were deformed as much as those bubbles are.

I also find it strange that gelcoat would bubble up like that without cracking.
On the other hand, only the seam bubbled up.

Perhaps the material of the seam is not gelcoat, or gelcoat with some additive to give more flexibility and avoid cracks at the seam line.

Well I am glad that despite the smartphones always in our hands there are still mysteries in life!

I would like to resurrect this topic. I noticed something similar on my Nelo 550.
On the right side of the rear deck it seems like the gelcoat was raised from the surface in a length of about 8-10 cm.
There is a short cut or crack around the middle of it. When I pressed the raised area water came through the crack.
I will certainly repair it, but I don`t know how urgent it is. Can I wait until the end of the season or will it get worse?
here is the raised area

and the crack