Cosmetic Blisters?

[Booda]

Well, we have been looking at alot of boats lately, and found one that definitely went to the top of the list, until the broker told me that the bottom was covered with small blisters, the boat was recently surveyed and the surveyor said that the blistering was cosmetic and not a problem, then I found out that the blistering problem was know 3 years ago when the boat was last hauled and bottom painted with four coats of bottom paint. The broker said that the blistering isn't any worse than the last time the boat was hauled. I do really like this boat.

I have a few of thoughts.

1. I really like the boat and it fits my needs, maybe I should get it surveyed again and get a second opinon, on the condition of the bottom.

2. Walk away and keep looking.

3. Make a offer with the knowledge that eventually I'm going to have to deal with this bottom problem, and adjust the offer accordingly.

Any thoughts...

Thanks

Still looking.....

[Plumper]

1 and 3. Get another survey and if you still like the boat then haggle and buy.

[Jeff_H]

There are few cases where blisters are only strictly cosmetic. For blisters to be 'only cosmetic'I can only think of two possible cases;
1. Where there was a failure to bond between the gelcoat and the laminate and the laminate needs to be something impermiable like vinylester resin. In that case the blister is strictly in the gelcoat and not an issue.
2. Where the blisters are only in the barrier coat or the bottom paint, and does not extend into the gelcoat and laminate.

The first case is not very common but may become more common as vinylester resin and infusion become more common. The second case is more common, but is pretty easy to detect by flipping open a couple blisters and you should see clean intact gelcat.

Anything else, the laminate is involved and blister repair will continue to be a part of your general maintenance regime. Over time blister problems usually become more extensive. So I think if it was me, and I really liked the boat, I would probably get a second surveryor to only look at the blister problem, and depending on what he says, if he thought it was minor but in the lamimate, I would probably follow your option three. If it was more widespread and deeper in the laminate, then I'd follow your option 2. Major peel type blister jobs are the only way to really make a permanent repair and peel and repairs are a pain in the butt with the boat out of commision for a long time.

Jeff

[chris_gee]

There was a good thread on osmosis reently with a good article cited. Ideas on osmosis seem to heve changed with experience in treating it.
The cosmetic idea and just grinding and filling doesn't seem to resolve the problem, which seemingly is of certain chemicals dissolved within the laminate. To remove them involves removing the gelcoat then flushing and drying. Then restoring the thickness and applying barrier coat. That would be very much more expensive and make the venture uneconomic on a cheaper boat. The owner broker and some surveyors are likely to take the cheap grind fill and cover up option and you may have to take some photos and seek specialist advice or make up your own mind.

[KeelHaulin]

I would like to make a comment regarding hull blisters and the determination of if they are cosmetic or not. I would say that 99% of blister problems that are seen in hull bottoms are "cosmetic"; because they are formed in the layer either directly beneath the gelcoat or in the first layer of fiberglass called "strand-mat".

The strand-mat is a non-structural layer of fiberglass; it is placed beneath the gelcoat and usually sprayed on via an air gun that sprays resin and fiberglass strands (known as a chopper-gun). When the strand mat is applied it does not wet out fully and and/or traps air bubbles; and this is where moisture can penetrate the layer and cause blisters to form because the fibers are not directional and there are voids/dry spots.

The reason strand-mat is used is that it prevents "print-through" of the woven cloth in the gelcoat. If you see a gelcoated surface that looks bumpy in a pattern; that's print-through showing the woven cloth beneath the gelcoat. Strand-mat is used to prevent this; and for that reason it is a "cosmetic" and definitely non-structural layer.

The strand-mat is one of many layers of fiberglass that make up a hull. The layers beneath the strand mat are directional woven cloths that are much more impervious to water and in general are immune to forming blisters because the resin wets the fibers more uniformly and the ends of the fibers are not exposed to allow water to penetrate them. They are much stronger mechanically than strand-mat and make up the structural component of the hull. It is very rare that a blistered hull will have blisters beneath the strand-mat layer; if it does, then the blisters -may- be structural in nature.

While I agree that a blister repair job is both costly and/or time consuming in terms of labor; I don't consider their presence a death sentence for a hull; certainly not if the hull is otherwise sound in construction. A bigger (and certainly structural problem) with modern fiberglass hulls are cored hulls that have failed by delamination or rot; and that is both dependent on construction technique and if the hull has ever had impact damage or water penetration into the core.

There are methods to prevent future blisters that involve barrier coating the hull after grinding and re-fairing the blisters and allowing the hull to dry thoroughly. Many people who have done this have reported excellent results; both with paint-based barrier coats, or coating with straight epoxy. Do a search on the gear/maintenance forum to get more info. I'd say that if you are serious about wanting to buy the boat; decide if you want to get a reduction in price and have the blisters repaired or DIY the job. If the boat is in fine condition otherwise; upon a good survey you should not let the blister issue stop you from completing the purchase; especially if there are not many other boats like it (that fit your needs) on your "A-list".

[Booda]

Thanks for all the replies, I have continued reading and learning about the blisters and their cause and effect. I have decided to pass on the boat. The blisters being one of the reasons, I have found another boat, much the same as the first one, but without the blister concern.

Pat

[Jeff_H]

I would have to respectfully disagree with Keelhaulin. Very few manufacturers use/or used a chopper gun for the veil coat. Most used light weight mat (a non-oriented fiberglass felt) laid up with laminating resin (rather than finishing resin) which meant that the veil coat resin was continuous with the laminate resin and that where blisters occur in the veil coat, they also tend to pierce deeper into the laminate.

While Keelhaulin is correct that blisters that only remained in the veil coat would be cosmetic, it is rare for that to be the case and so in most cases, blisters in any of the laminate is potentially structural.

Respectfully,
Jeff

[PalmettoSailor]

Although I chose to pass on the boat I was looking at that had blisters, someone mentioned previously that you'll be hard pressed to find a refrerence to a boat that was sunk by blisters. Blisters do sink boat resale values and boat sales, however, so if you elect to purchase a boat with that problem, you need to be sure you get a deal that will let you get out with out loosing too much skin.

Since the only repair technique with much chance of preventing a reoccurance of blisters
(a full peel and relam) runs around $300/ft or more X the length of the boat, it just doesn't make sense to invest for that kind of fix on a lot of otherwise nice boats. Grinding a filling as they occur will likely be an ongoing battle but may allow you to have a boat and enjoy your time on the water between blister fixes.

[Stillraining]

KH and Jeff....I highly respect both your wisdom . and I would agree with both of you....On my boat I have exactly what KH describes and the problum is exactly as he describes it...although I have Know idea if Irwin used a chopper gun or the mat technique....But if you dig out a blister on my boat ( And I have LOTS ) you immediately See glossy well saturated structural mat and the outer non structural or veil coat as Jeff describes it ( thanks Jeff ) is 100% where the problum lies....it looks so darn dry that I wonder if there is any resin in it at all ....

This is why I will some day do a peal job...to get it all off my hull bottom...on the other hand this is also why I might not do it for 15 years ( Arbitrary number ) as other then adding a little extra weight of water to the boat it ain't hurting a thing structurally..I dug out three .50 piece size ones last month and faired them back a ways...mixed up some epoxy painted on a couple thick coats ..let dry ..then Bottom painted them...leaving a definite impression because I didnt eve bother to fair them with the rest of the hull...Now I have Hail dammage..

This will be my mode of repair every year on large ones untill that fateful peal job...if I live that long..I negociated 25 K off the asking price of my boat and took advantage of every-ones else's fears on the blister bandwagon...I consider myself a shrewd negciator because of that...and the boat is exactly what I wanted...well no I take that back I wanted the 52 footer..

[KeelHaulin]

Yeah; I should have pointed out earlier that strand-mat comes in two flavors (sprayed on or in a "cloth"). Both have the same drawback of not fully wetting out when resin is added. It is still my belief that blisters that form in the outer layers are non-structural and therefore "cosmetic". There is a surveyor who has a website dedicated to blisters and such who confirms this and in some instances suggests just leaving them alone (can't remember his name/site). But they are a nuiscance and can be expensive to repair if you decide to strip all of the mat layer off. If the boat is not trailered and over 20 years old; generally there are blisters (or were blisters that have been repaired). You can't really know without stripping the hull down to gelcoat; a good blister repair/fairing will not be visible or easily found by a surveyor (without stripping off paint). The nature of all materials is for water to penetrate via osmosis; and 10+ years sitting in water is usually enough time for it to work it's way in.

I still can't envision a blister problem so bad that it causes structural failure; you'd have to have so many deep blisters that penetrate the woven cloth that it is like a honeycomb (a deep blister every 2-3 inches). Of course if that structural layer is thin (as is true of newer, cored hulls) it would become a structural issue more quickly (especially if it penetrated to the core); but again that's IF the hull blisters penetrate deeply into the structural woven cloth layer(s). The only/biggest issue I have heard of with blisters that were -potentially- structural were in the early Valiant hulls. The resin used was not the correct type and blisters formed beneath the woven cloth layers. Don't quote me on this; it's what I have heard and I don't know the entire story (if they are repairable or if Valiant has warrantied severe cases, etc). Valiants are excellent blue-water boats and I'm not trying to say anything bad about them (new or old).

Vinylester resin (used in most hulls) is not impervious to water. Epoxy resin is claimed to be; but some say that it is only lower in diffusion rate of water than vinylester.