What causes hull blisters in Fiberglass/Gel?

[craze1cars]

1992 Rinker 181 runabout, white hull. Seems to have had a fairly abused life. It has quarter sized hull blisters every 1 foot or so, some cracked/popped, some not there yet. Most are running along the keel and the two smaller side keels (the long pointy ridges that run front to back parallel to the keel...sorry I don't know all my boat technical terms yet)<br /><br />I have my own theories, but would like to hear from others with more experience before I plant any ideas. Mostly concerned if this is just cosmetic and failing from the outside, or structural and failing from the inside.<br /><br />Thanks!

 

[Boomyal]

Re: What causes hull blisters in Fiberglass/Gel?

The only thing I can say with certainty is that over the years, especially during the first energy crisis, some boats were plagued with fiberglass blisters. It had to do with an inadequate amount of resin used in the construction. I don't know what a solution would be if yours is one of those.

 

[CalicoKid]

Re: What causes hull blisters in Fiberglass/Gel?

If the boat sits in the water all summer tied to a dock the blisters are likely from water intrusion. Water penetrates gel coat and fiberglass by osmosis. It then wells up and drives the gelcoat away from the fiberglass. So the damage is mostly on the outside. I think if you cut open one of those blisters you'd find delamination over an area about twice the size of the blister. This is mostly cosmetic but check out the inside structure of the hull carefully. Water sitting inside a hull over time can cause bigger problems.<br /><br />The 'side keels' on your boat are either the strakes or chines.

 

[craze1cars]

Re: What causes hull blisters in Fiberglass/Gel?

OK...that certainly makes sense, and based on the extent of hard water deposits and algea I've been removing the past week it's very clear that this boat has spent a large amount of it's past just floating around in a slip somewhere.<br /><br />And yes, there was evidence of water in the hull, I've done some structural repairs on the inside over the winter. Unlike prior owner, I'm a "trailer it to different lakes on weekends" kind of guy, so this boat won't just sit & soak water much this year. I'll ignore the blisters for now, but maybe next winter I'll tackle them if I feel this beater is worth keeping.<br /><br />This was a great starter/learning boat that I got for a steal. Might upgrade to a better cared for "trailer queen" now that I've learned a lot of what to look for during my winter restoration project that I undertook. This site has been very helpful as well...thanks to all.