Steel Hull insulation after 36 years

[Mara Mae]

I have a PhD in English Language Arts and a k-12 teaching certification. I found the OP's post informative and useful. The lack of punctuation and paragraphical style did not bother me in the least. Thank you original poster you helped me look for potential problems I may encounter as I shop for a steel boat.

[hpeer]

I am recovering from a reposting exercise since my above post. This is on our small boat, 1982 10gage mild steel, urethane sprayed foam that extended well below the water line.

I had a leak in a vent near the bow and the water found its way under the foam, routed by stringers. I found a blister in the paint that, when investigates turns out to be two tiny holes. It was pretty thin there so I went with replaying.

I had to remove the holding tank and scrape out the old foam. What a mess. Luckily I had pretty good access to the inside hull. Had this occurred on the stb. side the story would have been much different.

The interior, 1982, appears to have been painted with that yellow/green zinc oxide primer. It didn’t do a real good job of protecting the steel.

The actual cutting and welding took maybe 30 hours, the prep and recovery twice that easy.

[Mara Mae]

I am staying on a 40 Lod steel ketch this weekend that I am considering purchasing. It is 6mm steel built in 1965 and still has no visible rust. Survey will include multi-echo sounding but in the meantime I want to have a close look. It is not insulated and I have almost complete access to interior hull. I wonder if I will have to insulate for my purposes offshore cruising both northern and southern hemis. Sprayed in means I lose the access for inspection I now have. Armflex looks good but I worry that seal will not be as complete as with sprayed in. I am also wondering if closed-cell foam pads could be held in place with magnets or tape to facilitate periodic inspection.

[Salmoneyes]

Originally Posted by hpeer

I am recovering from a reposting exercise since my above post. This is on our small boat, 1982 10gage mild steel, urethane sprayed foam that extended well below the water line.

I had a leak in a vent near the bow and the water found its way under the foam, routed by stringers. I found a blister in the paint that, when investigates turns out to be two tiny holes. It was pretty thin there so I went with replaying.

I had to remove the holding tank and scrape out the old foam. What a mess. Luckily I had pretty good access to the inside hull. Had this occurred on the stb. side the story would have been much different.

The interior, 1982, appears to have been painted with that yellow/green zinc oxide primer. It didn’t do a real good job of protecting the steel.

The actual cutting and welding took maybe 30 hours, the prep and recovery twice that easy.

This is a story that makes me think long and hard about spray foam...

We are fully sandblasted inside and out, and doing our metal repairs now. We plan to weld up all the jib track holes and through bolted hand rails and toe rails and replace those items with welded on pieces.

Definitely trying to reduce the amount of holes drilled in the topside...

[Fore and Aft]

I am far from an expert but If I ever owned a steel yacht I would like removable insulation panels. They could be easily cut and wedged in-between the stringers and frames.
Whatever you do it would be well worth your while to find a company who could inspect the inside of your hull with one of these machines.
https://www.elcometer.com/en/holiday-detector.html
I am a NACE coating inspector and have inspected miles of gas pipelines with one of these machines and you would be amazed how it can pick up pinholes or thin coatings. It would be well worth it since steel yachts rust from the inside out and getting your interior coating close to perfect would be a good head start on keeping rust at bay.

Cheers

[RaymondR]

I owned and maintained a steel boat for about 30 years and learned a lot about their construction and maintenance during that period.

One of the most consistent lessons was that much of the maintenance problems experienced could be prevented by better design.

One of the primary design rules is that any sort of inaccessible crevice must be avoided.

A second is that all steel structures must be either sealed against moisture ingress or be readily accessible for inspection and maintenance.

It should be a criminal offence to put stringers in a steel boat - they are the most prolific creators of water traps.

[Salmoneyes]

Originally Posted by RaymondR

It should be a criminal offence to put stringers in a steel boat - they are the most prolific creators of water traps.

If by stringers you are referring to the longitudinal framing members then I agree... Hot topic and a lot of NA's will have opinions. Our boat was built frameless then transverse members added. The boat is extremely fair and it circumnavigated with out issues.

Unfortunately, they used wood nailers between the transverse members which trapped water from leaking windows. Those caused some issue.

It will go back together with the nailers on top of the framing members so no water traps.

[RaymondR]

Originally Posted by Salmoneyes

If by stringers you are referring to the longitudinal framing members then I agree... Hot topic and a lot of NA's will have opinions. Our boat was built frameless then transverse members added. The boat is extremely fair and it circumnavigated with out issues.

Unfortunately, they used wood nailers between the transverse members which trapped water from leaking windows. Those caused some issue.

It will go back together with the nailers on top of the framing members so no water traps.

Wood onto steel is definitely a nono, it absorbs and traps moisture and invariably corrodes the steel under it.

I found that the best material to seal and fix to steel in order to minimize maintenance was aluminium. I eventually installed thin alloy gaskets, sealed with Sikaflex, under every piece of equipment on the deck which was not actually welded to the steel plate.

[MicHughV]

this is an interesting topic.

I built a Roberts 38 out of steel back in the late 70's...launched early 80's.
Additionally, I got to know several other steel boat builders and different models.

My own boat, I insulated the hull with 1" thick styrofoam panels on the inside. These could be bought in 4'x8' panels and could be easily cut with most anything to fit between frames, etc. I glued to the styrofoam panels to the hull with a wood glue that could be placed in a caulking gun type of dispenser. I only placed these insulated foam boards down to the waterline as I wanted easy access to the hull for inspection and in case of an emergency. Below the waterline, I figured the ocean water would provide sufficient insulation.

I lived on and sailed that boat all over the place for many, many years and never ever had any problems with heat, cold, moisture, nothing...not once, not ever.

The 1" foam panels were relatively inexpensive..... and even scraps of the foam could be wedged in wherever needed.

I've been on some steel boats that had the injected foam insulation pumped in from a gun. While there is no disputing the better thermal qualities, that foam has to be trimmed back and shaped, a giant pain the rear end.

Additionally, the deck on my boat was covered in 1/4" thick " deck tread", which also assed to the insulation properties.

All told, summer or winter

[MicHughV]

I should add, that the interior of my boat was sand-blasted and painted with " coal-tar" epoxy, prior to the panels. The outside of the hull was also blasted and had a whole paint system on it, zinc primer, various undercoats and several finish coats.

Not once, not ever, did I ever have a rust problem. Rust usually starts on the inside. The coal-tar epoxy is a thick 2 part gooey epoxy that hardens like steel.

Once in a while, I would nick the paint on the topsides, but a quick touch up would take care of the problem.

As an aside, I recently discovered my old boat, now on it's 3rd owner. So we are talking 40 years here. The outside had been repainted in a different color scheme, but the interior still had it's original coal-tar epoxy coating....still going strong !!

[hpeer]

Originally Posted by RaymondR

Wood onto steel is definitely a nono, it absorbs and traps moisture and invariably corrodes the steel under it.

I found that the best material to seal and fix to steel in order to minimize maintenance was aluminium. I eventually installed thin alloy gaskets, sealed with Sikaflex, under every piece of equipment on the deck which was not actually welded to the steel plate.

That sounds like it makes a lot of sense.