Blistering Hulls

Hey Everyone,

I pulled my '76 Hobie 14 out of the lake this past weekend, and started in on the horrendous algae growth on the hulls (I keep the boat on a mooring buoy, and it was an unusually warm, sunny summer). Water and Bleach wasn't getting the job done, so my local marina recommended "MaryKate's Hull and Bottom Cleaner for Fiberglass" - it's basically a diluted acid that you brush onto the hulls, and it takes the waterline/algae stains right off. It worked like a charm, leaving the hulls shiny white.

When I was done, however, I noticed a lot of tiny "bubbles" in the fiberglass, mostly below the waterline. They look like you could pop them if you pushed hard, but they're actually very solid, and can't be depressed at all. Is this the blistering problem I've heard people talk about?

I've never noticed them before, but I haven't had the hulls this clean in a few years either. I haven't done the other hull yet, but it's so crusted with pond-scum that I can't tell if that hull is blistered as well.

So my question is two-fold. First, is my miracle-cure acid causing this bubbling, or was it already there, hiding under the green carpet? I know I was leaving the acid on a bit too long, and it took many applications to get the stains all off. (I think it's taking longer because the hulls are vertical, and the acid is just dripping off.)

Second, how do I fix it? Can I just sand the bumps down, then polish and wax, or is it more complicated? I've never had any problems with the hulls before, other than a few dings and scratches. No soft spots at all.

This boat has some sentimental value, so I'd like to keep it in good shape if I can, and any help, advice, suggestions anyone has would be greatly appreciated. Thanks a lot.

-Bill

Likely you have osmotic blisters. The hull material is absorbing water.

http://www.capsante.com/Articles/osmotic.htm

The above link has some good information about the cause and repair.

<<Osmotic Blistering is a condition found in most fiberglass boats. Blistering occurs when water penetrates through the gel coat and mixes with water soluble materials found in the fiberglass layers beneath it. The seawater then becomes a solution that will try to equalize with the seawater outside the boat. As the solution has now grown molecularly, it cannot back out of the passage it entered, it builds up pressure as it tries to escape and then it explodes, resulting in blister domes which appear on the outside of the hull.

The repair procedure is as follows, first a technician removes all of the anti-fouling paint, gel coat and any damaged fiberglass by peeling or grinding the underwater body. The underwater body is then scrubbed with a solution of TSP and water to remove any stray contaminates. Next, the boat is tented off tight around the bottom and a dehumidifier is run in the tent to keep the air as dry as possible. Once the hull bottom has dried to an acceptable level, an epoxy barrier coating system may be applied. The drying process may take from 2 weeks to 12 months.<<

Go to the link for the complete story.

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

Hi Matt, thanks for the info.

This sounds like a very involved (and expensive) repair. As much as I love this boat (My parents bought it when they got married, and it's the boat I grew up with and learned to sail on), I don't want to dump too much money into a 30 year old boat. I don't suppose there's anything I can do at home to fix the problem?

After reading your response and the article, it sounds like this is mainly a cosmetic problem, at least for now. If I decide I can live the the existing blisters, what can I do avoid getting more? I may be able to explore other mooring options to keep the hulls out of the water, but is there anything I can apply to the outside of the hulls to keep water penetration to a minimum?

I had already planned to polish and wax the boat this year. Will a fresh coat of wax do the trick, or should I be doing something else as well?

Thanks.

-Bill

If you plan on storing the boat in the water for long periods of time, you need to either paint the submerged portion of the gelcoat with a bottom paint or other suitable barrier coat. Gelcoat is not waterproof and water will get through the gelcoat, as you have seen. A treated bottom coat or anti-fouling coat will also keep the algae population down on your hulls.

Another thing to think of when mooring your Hobie is to keep the rigging tight when it is not being sailed. The loose standing rigging to allow the mast to rotate will slam around when the boat is hit by waves. This will streach out your rigging and could damage it as well.

_________________
Nick

Current Boat
In the market
Previous boats owned
'74 Pearson 30
'84 H16
'82 H18 Magnum
St. Louis, MO

Great points Hobie Nick.

We don't recommend mooring cats for those and more reasons. I suggest pulling it up on a dock or float. I have even seen blisters from sitting in wet grass (more like a swamp I'd guess).

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

Just remember if you pull it up onto a float you still need to tension the rigging so it won't bang around.

I am considering putting my H18 on a floating dock so I will actually be able to take it out at a moments notice. I was planning on using one of the trap wires to tighten up the rigging while stored. I would attach it to the shroud adjuster. Does anyone see any problems with this idea? It always helps to get a second opinion.

Thanks,

_________________
Nick

Current Boat
In the market
Previous boats owned
'74 Pearson 30
'84 H16
'82 H18 Magnum
St. Louis, MO

Thought this link may be timely.



When putting the 16 away for the season last weekend, we looked her over closely and noticed a few little blisters in the hulls. She's got some beach rash and a few gouges here and there and I'll be mixing some epoxy, sanding and gelcoating for that work next spring. With a nice dry (humidity) winter approaching I opened up the blistering spots to dry now, rather than trying to force some drying next spring when I'll be anxious to get her in the water again.

_________________
hobiejohn at earthlink dot net
Fleet 297

I have had great success with a product called Pink Stuff. It is available at most Auto Supply stores. It is biodegradeable and non toxic. It is highly concentrated and I have used it on all of my boats as well as my cars.
I have actually used it to remove #6 fuel oil off the side of a brick building much to the surprise of the State Dept of Environmental Protection.