Insulating with wool?

Hello all.
I’m currently restoring a 1949 german built fishing cutter into a houseboat/costal cruising boat. I have worked as a boatbuilder/ rigger and sailor for the past 8 years so I have a pretty solid handle on most things. I am pretty confused about the insulation.
Because my hull is riveted and has some pitting on the inside I would like to be able to oil it about once a year. My idea is to put plywood over the hull creating a 15 mill air pocket, then to lay the insulation (sheep wool) over that. I would have some sort of plug at the top what is airtight that could be opened to allow oil to be sprayed in. I’m planing on also insulating the floor. Thoughts?

 

The oil is thought to prevent further corrosion of the inner surface of the hull I suppose. But - will it distribute evenly if you spray it in small openings? You wouldn't be able to control the distribution optically. What will the oil do with the backside of the plywood panels? It is not easy to manage airtightness along the hull of an old boat. Even small leaks will be sources of air humidity and lead to condensation in an invisible space.

I've got some knowledge about humidity in air and building physics. Contact me, if you like. Berechnung von Daten zur Lüftung http://www.hygrothermik.de/

 

Why oil ? Surely you can prepare, paint, and forget ? I'd be amazed if suitable product did not exist.

 

Iv seen many steel boats that have been painted on the inside rust, and those with fluid film or another suitable product last. Iv been told, haven’t seen it my self that fluid film has kept builders marks on steel plates in ballast tanks after a few years.

 

What is the particular oil you use ? Not a drying oil ?

 

Fluid film is what I like to use. It stays tacky, which I like. I’m hesitant to use a drying oil which I’m guessing can crack.

 

Thanks Heimfried, I’ll take a look at the tonight. My idea is to allow condensation but to keep the hull oiled and with air moving through the gap so it can drain into the bilge. As for the plywood I would paint the backside with an oil repealing paint

 

it is a "humbug'" to have to keep repeating the dose, if it were possible to avoid with a paint film, which presumably would have to include highly waterproof 2-pack products. Does that lanolin leave any odour ?

 

There are much better solutions than oil or lanolin. They were products used 150 years ago because paints and other coatings were not much better. However, nowadays sandblasting and coating with epoxy based paints will give you a superior finish. Also, filling the interior of the hull with oil will cause a problem if you ever pump out the bilges. Discharging oil into the water is illegal.

 

I really hate the idea of wool. Make the ply panels removable with screws and strips and use xps foam along the ply edges. If you don't close the hull off, though, then why insulate? You will jist create a thermal wind by a warm insideand a cool hull. It'll feel drafty. When the boat moves or bilge drafts will destroy the entire effort.

You'd be further ahead furring and closing off the hull and no insulation. Leave the air gap and drain condensation to the bilge. Seal the plywood and furring with epoxy. Or put 1/2" xps on the plywood, but still no air gap. If you want to recoat the hull with oil, unscrew the panel, or use a more permanent solution.

 

Like Gonzo said, there are fantastic epoxy paints for steel boats, in fact, the paint will outlast the steel. However, shotblasting is essential and the manufactures instructions be followed to the letter. Use compatible epoxy primer before applying epoxy coat.
The last boat, a Dix 44 I built proffesionally in 2008/9, we used a paint / spray on insulation paint which works fantastic. It is a white paint with ceramic particals mixed in and I actually tested it on 3mm steel plate by heating the bare side with cutting torch to redish glow and you could still touch the painted side with your bare hand without burning yourself. It is a clean solution without the mess and problems associated with foams and wool. Any condensation that may formed, just flows back into the bilge.
This would be your your best bet, but as mentioned, any paint system is only as good as its preparation and shotblasting critical for good result. Good luck with your project.

 

lanolin and wool does seem "olde world", doesn't it. I guess steel that has been oiled, would need particularly scrupulous cleaning before painting.

 

Any industrial detergent will get rid of waxes and oils.