When we hauled Tango out of the water for her pre-sale survey, we noticed, after a quick look over, that she had a few blisters on her hull. For those unfamiliar, blisters are essentially boat acne. Per Don Casey “Fiberglass blisters occur because water passes through the gelcoat. Water soluble chemicals inside the laminate exert an osmotic pull on the water outside, and some water molecules find a way through the gelcoat. As more water is attracted into the enclosed space, internal pressure builds. The water molecules aren’t squirted back out the way they came in because they have combined with the attracting chemical into a solution with a larger molecular structure. Instead, the pressure pushes the covering gelcoat into a dome – a blister.” We knew that these were going to have to be taken care of once we got the boat home and out of the water.
When we hauled her for the winter, we noticed that, upon closer inspection, she had more than we expected – at least a dozen or so. She had numerous layers of old, flaking paint on her bottom, which needed to be removed, and with the blisters we were seeing, we were now faced with two different options. We could have her soda blasted (similar to pressure washing with baking soda) or we could have the first layer of gel coat and fiberglass mechanically peeled. The former option would require, once the soda blasting was complete, that all the blisters be “popped” (oddly enough this result is much like squeezing a zit, but what comes out of boat blisters is an acidy liquid that you do not want to touch), opened up, washed out, and then allowed to completely dry out, and then finish with a repair. This is a significant amount of work, and may not guarantee that you will fix the problem. With the latter option, it would be the more (much more) expensive option, would be less work for us, but would give us a better chance of not having blisters in the future. The catch here is that once she was hauled, while we saw a few more than we expected, we didn’t really know the extent of the problem and wouldn’t know until we did the soda blast. However, if we did the soda blasting and found many more blisters (hundreds instead of tens, we’d be out the money we spent for the soda blast which is, by no means, inexpensive, and may still need to have her peeled, which is quite expensive.
So, in the end we decided to just to do the soda blast, assess the full extent of the problem and repair the damage. In all the reading we’ve done, shallow gelcoat blisters will not sink your boat. They are not ideal for the hull, reducing her hydrodynamics, but they are not detrimental to the structural integrity of the boat unless allowed to go unchecked and develop into deep blisters (penetrating the second layer of laminate and beyond). She now sits in the yard, with a completely bare bottom down to her gelcoat.
|Tango before her bottom was soda blasted|
|Soda Blast Prep|
|Tango after soda blast|
We’ve discovered a lot of blisters (more than a 100), all but three of which are only through the gel coat with the remaining three only into the first layer of fiberglass. This is relatively good news, but this also means we have a lot of work ahead of us. Each one of the blisters will need to be fully opened up, grinded out and then built back up with epoxy ( a combination of resin, hardener, and colloidal silica). The down side is this may only be a band-aid if the gelcoat is prone to blistering, which it seems to be. In that case we either have to live with the blistered bottom and fix them as they come up, or go ahead and have her peeled and repaired, shelling out several thousands of dollars for an essentially new bottom. While the money set aside for her current refit is quickly dwindling, we’ll look at her again in two years when we have her hauled again.
|A couple of small, surface blisters|
|The blisters are the dark spots, her port aft hull area has quite a few.|
|One of the three bad blisters on Tango|
Surprisingly, blisters are not that uncommon and it really is a game of chance as to whether your boat will have them. Sometimes they tend to be seen on particular brands of boats, which may mean that they are due to the way in which the hulls are laid or the ingredients the manufacturer used for the gelcoat. Others seem to happen by complete chance, such as those on our Mason 44. Maybe they waited too long between spraying the gelcoat and laying the first layer of fiberglass, maybe it was a bad batch of gelcoat, but one thing is for sure; there isn’t anything you can do as an owner to cause blisters, but once you have them, they’re yours to deal with I guess when you compare our boat to others with blisters, it could be worse…
|Not our boat but an example of a serious blister problem.|
In the end, considering our boat is an adolescent (16 years old), we shouldn’t be so surprised she is suffering from an acne breakout. Let’s just hope she doesn’t go through that lashing out phase where she hates her parents.