Blister repairs General Forum Forums

Some notes on our experiences with blisters on several boats over the years!

One good thing, is that they won't sink you! However, they will slow you down for two reasons - the hull is a lot heavier with all that water in the lay-up, and the lumps themselves create more friction. You may not have noticed that immediately after hauling, the blisters are a lot more evident than a few days later ( when you may conclude that you don't realy have a problem!!). In the early days of fibreglass boats in the '60s, one of the first indications of the problem was with the newly asigned Soling which replaced the Dragon in the Olympics. After a while they realized the the boats that were kept on moorings were consistently slower than the ones lifted out after each race. At that time blisters didn't show up - I'm told, because the early gel-coats were different and water was freely moving in and out of the hull. After the 60s with different gelcoats, water was less able to get out - hence the blisters. Hulls can hold an awful lot of water. After we did a major treatment on our Peterson44 - she popped up out of the water by nearly two inches!! We were next to another Peterson in Berkley CA once, that had a fairly airtight skirt around her (after a single, shallow peel) and several dehumidifiers running day and night for 6 months and the water that came out of her was unbelievable.

We double peeled our 44 to get past the wet stuff, believing that it's almost impossible to dry a boat out just be waiting (however long). We then layed-up two layers of a heavy mat/biaxial cloth, using vinylester topped with a vimylester barrier coat. We followed Bumgarner's ( of Zahnizer marine, Solomons MD) recomendations. He seems to be one of the main authorities on this. Vimylesters are somewhere in between polyester and epoxy both pricewise and ease of use (much easier than epoxy). Two of us did the lay-up and barrier coat in a day and a half.

On a previous boat (an Ingrid), which hadn't ever hit the water for some 15 years after the hull was made, we used International's Interprotect system before launching and had a lot of blisters afrter three years (in the tropics). Their system is user friendly but not as affective as really sealing the hull with epoxy/vynilester (after getting rid of the water). With that boat, I ground-off the whole bottom, dryed-it out as best as time would alow, and put on 6 coats of straight epoxy (then a barrier coat, to which bottom paint will adhere). The problem with epoxy is that it dimples and the more coats you put on, the worse it gets. Sanding off between coats is an awful task (it's so hard) and you end-up with half as much epoxy as you put on! If you are prepared to be up half the night, as I did - you can put layer on layer without prep. as long as you time it when it is still 'green', but you still have the dimpled 'orange peel' affect, which is difficult to get anything to stick to!

Spot treating blisters is a temporary fix which is OK until you want to sell the boat, when it will probably be discovered and reduce the sellin price by about $10,000 - the going cost of getting a yard to do a proper job!

Not having water inside the boat is said to be half the battle to avoid water saturation. It is possible to have a dry boat these days with foolproof sealers and dripless shaft seals/stuffingbox packings. It also eliminates the mildew problem even in the tropics. We left a (dry) boat in the water in the Rio Dolce, Guatemala for six months - sealed-up - and came back to a boat that was as fresh as when we left her ( evryone else had paid hands opening their boats up and/or running dehumidifiers continually).

Tim - 'Pelli'  DE32