Question about hull blistering

[surban21]

Looking for some advice ... I have a 1978 15.5 ft Challenger Mark VI tri hull that that I was given. It'll need to be restored (Stingers and what-not). One of the issues with it is basically 60% of the hull below the water line has what I believe to be vary small blistering bubbles and a few larger ones with hair-line cracks on the edge of them. I've read some of the posts here about these blisters and know that it is caused by water getting trapped between the gelcoat and resign? layers. Almost all of these blisters are about 1/16th inch in size or so, but a few of the larger ones are about 1/2 inch size.

My question is: Since most of these blisters are the smaller ones which cover almost the entirety of the hull bottom and sides below the waterline, do I need to concern myself with the thousands of smaller ones? - or - can I just repair only the larger ones that have the cracks and any others that are obvious problems? Would it be better to completely resurface the bottom of the hull?

The bottom of the hull in various spots feel firm and I cannot detect any soft spots from underneath. The boat is trailered and as far as I know from the previous owner it has always been a trailered boat.

I've attached pics which hopefully will help. Thanks for your help.

 

[tpenfield]

The big ones are the mommy & daddy blisters and the little ones are the children. They will grow up to be bigger, but it is hard to say how long that will take.

 

[jbcurt00]

Yep ^^^

I'll add that its mostly an all or nothing proposition

Leave them all alone

Or

Grind all the gelcoat off and reapply, hoping for the best that the grinding releases all the trapped moisture or blisters will return..

 

[surban21]

Thanks for the replies .... so if the blisters/bubbles aren't open and peeling away from the hull then no real action needed until such a time when they do break open? Does that go for the one's that have the hairline cracks in them too? If it does, then is it because they are shallow cracks that aren't down to the level of the fiberglass so water really isn't doing any damage to the glass (yet)?

Thanks again for the fast responses.

 

[tpenfield]

In a word no . . .

The ones that have 'cracks' have broken open. If you peel the gelcoat away on some of the larger ones that have cracked open, you should be seeing the fiberglass layers.

Each year the small ones will get bigger and eventually will crack open like the ones before them.

You can continue to chase the larger ones (cracked or not) , grind them open and fix them. . . but the full remedy would be to grind off the gelcoat and re-finish the bottom.

 

[surban21]

Thanks tpenfield ... that helps but I'm sure there will be more questions I'll have when I actually get to that phase. Right now I'm trying to get a "guestiment " on what I'm in store for in addition to all the structural work needed.