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**Jeff H** · 20-04-2006, 04:20

At least when I was with Charlie, he did not recommend foam spraying. In those days there were a lot of good reasons he chose not to foam a hull. Certainly a major issue that is still true is that you cannot easily inspect, and maintain the water barrier protecting the interior of the hull.

Using the technology of that era, the foam did not adhere uniformly to the hull and so would create a series of capilaries and air chambers against the steel that allowed water to get in but not get back out very easily. This held water against the steel ranter than keeping it away. This created a situation where heating/cooling cycles were believed to create very high moisture pressures, and condensation, which were thought to increase the likelihood of corrosion, and versions of crevice corrosion. During that era the foams being sprayed were quite flamable and outgassed carcenigenics.

My own experience during that era was consistent with the commonly held viewpoint on spraying foam on steel hulls. I had looked at a steel boat being refit (this was at a time when I was a big fan of steel construction). Sections of the spray foam had been removed and deeply rusted fish eyes and worm trails followed those areas where the foam had not adhered. The hull had been painted with a barrier coats which according to the owner was an epoxy barrier coat.

From the discussions that I have been reading lately my sense is that the technology of spraying foam may have changed, either that or the negative impact of spraying foam is simply being downplayed. I don't have a way to evaluate that situation.

Jeff

Dman · 20-04-2006, 04:43

Does anyone have any thoughts on using the spray on bedliners that are used in trucks.Now that stuff is tough,repells water and does not chip.The one thing that always bothered me when dicussing rust on steel boats is that there is always someone who wants to have a contest to see how long they can neglect a boat and than criticise it when it fails.I have metal micrometers that i have to protect from corrosion and like any tool if you fail to look after it ,it will fail to look after you.Having a steel boat to me suggests that if you are not willing or capable of taking care of it than it is definitely not for you.Sort of reminds me of the guy who drives a white car that is 2 years old that was scraped down the door when he first bought it and watched it rust away.With proper construction you should be able to access all spots that could prove potential corrosion areas.You will always have someone saying this is the poster child of metal cars when buddy goes to sell his rusty car with the rust stained white door.

Yachts66 · 20-04-2006, 08:37

Good idea, hadn't thought about that, particularly for the chain locker....not sure what the cost would be though. I've also heard they spary vehicles in Iraq with the stuff because it's near bullet proof, but I don't know if it's true.

Regards,

TJ

Brent Swain · 20-04-2006, 13:52

This makes it clear why steel boats have to be heavily epoxied inside before sprayfoaming. The reason steel boats have a reputation for rusting from the inside out is because too many people don't adequately paint the inside before foaming. They all too often spray foam over bare steel.Foam is no protection for the inside of a steel boat.If they didn't paint the outside and they had a reputation for rusting from the outside in, would these same people be able to figure out why?
A steel boat in a cold climate without sprayfoam is unliveable.Nothing stops the condensation as effectively ,altho the ceramic super insulating paints look very promising.I've tried fibreglass and sheet foam ,all with miserable results. Sprayfoam has made my boat bone dry inside , year round.The new ceramic super insulating paint looks very promising and may make fibreglass batts a viable option for the first time.
Drag your fingernails over any spray foam. Where it has detached you will hear a distinctive hollow sound. That is where you should chip it out and have a look. If it is not painted beneath the foam, walk away.Primer is nowhere near enough protection.
Brent

**Alan Wheeler** · 20-04-2006, 14:28

Just to confirm Brent on his comment about Primer. Primers are porus. They will NOT prevent rust. They MUST have a topcoat.
Spray on foam his NOT water proof. In fact, it will allow water to slowly run under it and contact steel. There is enough oxygen in water to rust steel. It does not need total clear exposure to air. Yes steel is slower to rust underwater than above it, but rust it will, especially if it is salt water. The initial hull needs adiquate preping before any paint system is applied. As soon as it is prepared, it needs a primer application applied within hrs or sooner. An etching type primer is best. Apart from hot dip Galv, I have never yet seen a good cold paint on Galv really efficienetly work in an environment like boat bilges. The epoxy tars are not quite what they are cracked up to be. They are good at producing a very good membrane, but poor at adhesion to the steel. Once they allow moisture underneath, it creeps under further and the moisture can not get out through the membrane. But good epoxy paints are great adhesives and excellent binders.
BE VERY WARY of the Rhinocoats and other truck bed liners. They are poor adhesives. They are very tuff and durable, but poor at adhering, and do eventually wear through. There are touch ups in a can that you can repair damages, but once it starts to lift and peel, it quickly becomes a mess. You need a very bullet proof paint system underneath first. The stuff is excellent at noise reduction. But then there are also very good noise reduction systems available as paint on's as well. Also those liners are darn expensive and require special equipment for application. High pressure and heat.
Not to mention, is is quite easy to mix in compounds to epoxies and paint on to achieve insulation and noise reduction.

DeepFrz · 20-04-2006, 15:00

Alan, what would you recommend, a good epoxy undercoat and then several high solids barrier coats?

Steve Dashew has an interesting write up on insulation of his new boat at
http://www.setsail.com/dashew/hull_insulation.html

They decided to go with "Armaflex" on thier aluminum hull. I suppose with a good barrier coat it could be used on steel as well. It would make it easier to inspect or repair the hull down the road.

I wonder if anyone here has tried this approach with a steel hull.

Phil

DeepFrz · 23-04-2006, 19:03

CaptainK, have you checked out Dix's designs. I know your fist question was about the cost of steel, and I think this site would be able to give you more info. http://www.metalboatkits.com/index.htm
Scroll down and click on the Dix 35 for some building pictures from the precut steel.

Having seen other people building from plans I know that it is a long laborious process. Building from precut steel is very much faster.

Phil

CaptainK · 23-04-2006, 19:12

Yes Phil.

I have been to this site before.

I still have it bookmarked in one of my folders in "favorite places"!!

Brent Swain · 27-04-2006, 12:59

Etch primers are a disaster.
On a steel rudder on my first boat I tried an etch primer. The instructions said to let it dry overnight. Within an hour of putting it on it was rusting heavily. I tried coating it with epoxy tar before it rusted and that fell off in sheets. I took the etch primer off and epoxy tarred over bare steel. That worked much better. I sandblasted and epoxy tarred my next boat, over freshly sandblasted surface. That worked well . A friend blasted and etch primed his hull before epoxying it and the epoxy fell of in sheets. The etch primer still has acid in which causes corosion beneath the epoxy. It is vinyl , which nothing but Vinyl will stick to, and is much softer than epoxy.Sort of like puting cement over rubber.I've never in 30 years of steel boatbuilding seen etch primer be anything but disasterous on steel boats.
Sandblasted steel needs no etching.
Zincs wil protect steel from rusting below the waterline. On my last boat the bottiom of the keel was never painted, yet looked like new metal after ten years. My current boat has rarely had any paint on the keel bottoms as it grinds of quickly when I dry out, yet looks like new metal, no corosion or pitting of any kind. I've ground spots and left them bare for years with no visible corrosion or pitting.Unfotunately there is no similar simple solution above the waterline other than keeping your paint thick and intact.
If you have rust below the waterline you are definitly doing something wrong. Correct your mistake and you'll see no more rust underwater.
Brent

**Alan Wheeler** · 27-04-2006, 13:23

Something is not right with the the primer you have used then. It should never rust. But yes you are correct about epoxy over the EP's. You should never put a two pot anything over a single pot anything. Epoxy should have a "system" that start's with an epoxy primer.
You have to be very careful in using epoxy tars. It's great stuff, but there are very little other coatings that will adhere to this stuff.
I have never been a fan of using Zinc rich primers under anything. Rich Zincs tend to be soft in nature. They work becuae the Zinc effectively works in a "Sacrificial" way, much like an anode. It's hard to get top coats to adhere, and in an extreme situation, the Zinc can actually "work" like an anode and the top coating will fall right off.
It is also important to understand, most Primers and undercoats are Porouse. They will NOT stop moisture penatration and WILL end up with rust coming through if left for anytime unprotected. It is essential that the undercoats are thoroughly dry before applying a top coat or you will trap moisture underneath in the porouse surface if the undercoat.

CaptainK · 27-04-2006, 14:30

Quote:

Louis Riel once whispered in the wind
On my last boat the bottiom of the keel was never painted, yet looked like new metal after ten years. My current boat has rarely had any paint on the keel bottoms as it grinds of quickly when I dry out, yet looks like new metal, no corosion or pitting of any kind. I've ground spots and left them bare for years with no visible corrosion or pitting.Unfotunately there is no similar simple solution above the waterline other than keeping your paint thick and intact.
If you have rust below the waterline you are definitly doing something wrong. Correct your mistake and you'll see no more rust underwater.

WHAT!!!

Are you telling all of us in here. That if you do not paint the metal that is submerged underwater. Like on the keel bottom. Even with a zinc anode installed onto the hull, it won't rust? I'm finding that very hard to believe, Brent!!

With all due respect, Brent. Do you have any photographic evidence backing this all up?

Hey Alan!!

Do you think what Brent mentioned, is possible?

**Alan Wheeler** · 27-04-2006, 16:28

Ummmm, I hadn't read it that way. I just presumed Louis was talking about no etch primer. But on second reading, I am not sure and a little confused.
OK, so steel won't rust under water as to the extent it will when exposed to air. But it is rusting and eroding. I suspect that it is looking so new, because it is actually eroding away. Of course, if it looks "shiney new" then it is definately eroding away, but if that was the issue, I think you would be resting on the bottem permanantly by now.

CaptainK · 27-04-2006, 19:57

Yessssss?

But is it the anode protecting the steel. The unpainted steel on the keel. That Brent mentioned about.

How does it keep itself from rusting, without any paint on it?

**Alan Wheeler** · 27-04-2006, 21:00

Rust type corrosion and electrical corrosion are two different things. Rust is the process of the Iron surface turning to Iron oxide due to the presence of oxygen. As water has disolved oxygen and not free oxygen as in our atmosphere, Iron will not rust as freely underwater as it will in the air. Zinc anodes on protect from Galvanic corrosion. Galvanic corrosion can produce rust, because it is an electrolytic process. The electrical current produces hydrogen and oxygen. Of course the oxygen is going to react with the steel and cause it to oxidise. Having an anode protects you from one form of corrosion. So how steel can look as good as new after 10yrs under water is a mystery to me. Except for one point. If electrolosys is bad, it can actually make steel look shiney new. but it is actually the surface eroding away faster than what any oxide is forming. That is bad and I doubt any hull would last 10yrs.