Paint "Goose-Bumps"??

[Knotty1]

Hey all.

I recently flipped my glass runner over on the grass so I could start working on the hull. It was over for about a week or so. Yesterday, I flipper her back upright... as I was cleaning it off from the grass etc, I noticed in a few areas what I can only describe as "goose bumps"??? These were not there when I flipped it over!

Any clues? Would this be from moisture trapped in the paint/fiberglass?? Should I be worried? (Other than having to sand - again.)

Thanks for all your input.

 

[allpoints360]

Re: Paint "Goose-Bumps"??

Could it be blistering? Can you post a few pics?

 

[drewpster]

Re: Paint "Goose-Bumps"??

Blistering or "boat pox" Shows itself in the form of small raised areas or blisters under the gelcoat. It is can happen when the surface of the fiberglass is in direct contact with water for long periods of time. Tiny amounts of water penetrate the gelcoat where it comes in contact with the underlying layers of resin and fiberglass. There the water reacts with the resin and turns in to glycol. This in turn attracts more water that gets trapped under the gelcoat. The resulting pressure raises the gelcoat surface causing the blister. It occurs most often in older boats that have been exposed to water for long periods of time. In recent years boat builders have tried to eliminate the problem by using higher grades of resin then in the past.
Fiberglass is highly water resistant but not impervious to water penetration.
The good news is that the problem is only cosmetic. The problem is far more common in larger boats that stay in a slip the majority of the time. It does however happen to trailer boats as well, especially older ones. My tri-hull is at least 33 years old. I found some blistering on the bottom of the hull where the boat contacts its trailer's bunk boards. My guess is that the water trapped between the hull and the bunks caused it.
You have a couple of options on how to deal with it. Now that you have the boat upright I suggest you buy a tarp to cover the boat. I also suggest you raise the boat on stands so that air can keep it dryer. If you can keep the area effected dry long enough the blisters will most likely just go away. Over time the area will dry and the blistering will disappear.
The best option is to fix it for good. To do that you will need to grind out the effected area a little, let it dry completely, and replace a layer or two of fiberglass or epoxy filler. After fairing it you can repaint or re-gelcoat the area. This will eliminate the blisters in the repaired area but it will not prevent them from coming up in other areas.
You best bet, if only a small area is affected, is to keep the boat as dry as possible when it is not in use. If you keep it covered and dry as possible when it is at home, the "pox" will probably not come back.

BTW- I plan on switching to rollers on my trailer to prevent trapped water. You could also possibly drill some weep holes through the trailer bunks so the water can drain and the bunk carpet will dry out better.

 

[ondarvr]

Re: Paint "Goose-Bumps"??

You said paint, does that mean it has been painted? Many types of paint will blister when exposed to water, or water vapor for extended periods of time. It may be from the type of paint, or from the prep work done before painting.

 

[thrillhouse700]

Re: Paint "Goose-Bumps"??

Odd, I have some of those blisters where nothing touches it, re moved and flipped it yesterday and where the bunks were touching the gel coat looks brand new! Probably due to it being stored in havasu where it likes to get very very hot.

 

[Knotty1]

Re: Paint "Goose-Bumps"??

Wow - A lot of information!
Thank you all!

drewpster: Sounds like you've probably nailed it right on... Thanks for all the info! Unfortunately, I'm in Southern Ontario and our weather changes dramatically all the time... currently we are waling up every morning to a lot dew. I plan to bring it into the garage very soon for the winter... I just want to get the hull sanded and painted then bring her in and on stands. Do you think that the heat of the sun will just settle these bumps on their own? What about heating the area a little artificially?


ondarvr: It's only been primed, roughly and sanded...

allpoints360: I'll see if I can capture them on film.


Thanks again to all!

 

[drewpster]

Re: Paint "Goose-Bumps"??

I don?t think heating the area will help. The water needs to dry for the blisters to go away. It may take a long time. If you are going to sand and paint anyway I recommend you go ahead and open them up to allow them to dry. If you are going to garage the hull during the winter you have some time.
Generally all that is needed is a light touch with a grinder or a sander to open them. They will be just under the surface of the gelcoat. When you start your prep for paint get some epoxy filler. You can use the filler to fill the depressions left in the gelcoat after you grind out the blister. Very small blisters can be dried using a wipe down with acetone. Anything larger than your thumb should be allowed to dry thoroughly before you fill them. Blisters concentrated in a small area can indicate that the fiberglass laminate has water in it. I would go ahead and do your prep on everything else and come back to that area after you open the blisters. This will give the greatest amount of dry time. While the area is drying it is a good idea to periodically wipe the area down with clean water. Water!? you say? Yes...water. It is the best way to remove the glycol as it dries out of the surface. Blisters are most common on hull bottoms of larger boats that are kept in a slip. It can take months for a large area to be dry enough to recoat. It sounds like your blisters are far less pervasive. Just make sure you allow plenty of time for the area to dry before coating it with anything. Otherwise you may have problems with adhesion down the road.

Here is a good filler, I use it often

http://www.iboats.com/Interlux_Interprotect_Watertite/dm/*******.230859299--**********.877574498--view_id.350658


drewp

 

[ondarvr]

Re: Paint "Goose-Bumps"??

ondarvr: It's only been primed, roughly and sanded...

Gel coat won't normally blister in just two weeks of contact with wet grass, paint, or in this case primer, can blister over night.

Take a putty knife or something similar and pop open a blister and see how deep it is.

Just letting the area dry out may allow the blister to lay back down, but there will be no bond where the blister was, it is separated from the substrate, so as soon as it see's water or high heat the blister will return.

 

[SBTOM]

Re: Paint "Goose-Bumps"??

I had a similar problem a few years back when I went to paint a motorycle tank. I was dead-on sure I had done everything right so I went down to the paint shop to see if they knew why my $250 per quart paint was coming through textured. As it turned out, I had chosen to go with a rattle-can automotive primer as opposed to a catalyzed primer.... the guy at the shop said that the rattle-can primer tends to absorb a little bit of water if you try to wet sand it. Long story short, the moment the first layer of clear started to gel, tiny bumps started to form... Ohh man I was kicking myself for being too lazy to set up the HVLP and going with a two part primer! At least you caught it while it was still in the primer stage!

 

[drewpster]

Re: Paint "Goose-Bumps"??

Just so we are clear,
Knotty1, the blisters I am talking about occur in the gelcoat layer. (the outermost layer of resin covering the fiberglass itself) The blisters ondarvr is talking about occur under the primer. Two different problems.
If the primer has blistered it is a much easier repair that will not involve grinding in to the fiberglass. If the blisters are under the gelcoat then you need to grind them out and let the fiberglass laminate dry.

We (ondarvr and I) are talking about two separate issues.

enjoy
drewp

 

[ondarvr]

Re: Paint "Goose-Bumps"??

Just so we are clear,
Knotty1, the blisters I am talking about occur in the gelcoat layer. (the outermost layer of resin covering the fiberglass itself) The blisters ondarvr is talking about occur under the primer. Two different problems.
If the primer has blistered it is a much easier repair that will not involve grinding in to the fiberglass. If the blisters are under the gelcoat then you need to grind them out and let the fiberglass laminate dry.

We (ondarvr and I) are talking about two separate issues.

enjoy
drewp

Correct....primer is the easy fix....gel coat is much more involved.

 

[Knotty1]

Re: Paint "Goose-Bumps"??

Hi guys,

I have a feeling it is the gelcoat as the blister bumps aren't really under an area with any or much primer... they are popping up on the original painted area (it has been sanded though).

Here's a pic, not sure you can really see them...

 

[ondarvr]

Re: Paint "Goose-Bumps"??

Can't see anything in those pics. Did you dig one out to see how deep it is?