thermal expansion: metal / steel boats

[2020]

Hi all, does anyone have experience with metal boats and thermal expansion issues generally? wondering whether there are any noticeable impacts to be aware of? doors jamming, weld pressures, fittings joints, plate warp etc

[skipperpete]

Oh yeah, all of the above. No continuous welds, work alternately on each side of the hull, it takes great skill to create a fair steel hull….. or thick plating, that helps.
Once launched, I’ve not noticed any thermal expansion or contraction indications or problems, everything stays where it was welded, as it was welded.

[Lepke]

A dark hull color can cause enough sun to cause issues on lightly built boats. Proper welding techniques helps keep the hull straight. Lots of books out there on welding to avoid stresses. In the old days welded ships had one riveted seam. Some ships I was on had a flex joint in the superstructure.

[2020]

thanks guys, I wasn't in anyway contemplating becoming an instant competent expert welder I have far too much respect for the many years required to become a master marine welder and am always happy to pay for quality where needed.
I am however very interested in your experiences for planning in advance, it's always best to be aware of possible pitfalls and avoid them through good design / construction from the outset.
I guess it wasn't so much a concern with any hull related issues, more the finer aspects of the superstructure / doors to door frames / portholes / possible through deck fittings > movements etc. It's always the bloody little things .....
thanks for your comments so far.

[MicHughV]

Nah, never had a problem with my old steel boat of any kind. I used 3/16" plate. Thinner plate might be more problematic, but I say might. Proper welding sequence should eliminate mast any problems.

As pointed out above, welding sequence is important. Run one bead forward.....skip 5' or so, run the next bead backwards, then skip to the other side. Rinse and repeat.
It's a bit of a pain in the arse running back and forth all the time, but it's what you gotta do.

All the frames, longitudinal bars, etc, will also keep everything in check.

I should mention, I had never welded in my life before building my boat. I had "on the job training". I must have welded 100's of samples before I laid an inch of weld on my boat.

Right before I started, I lucked out and had a professional welder stop by and give me a few tips and " how to" methods. Worth his weight in gold to me, and my advice to you is seek out a pro welder for an afternoon welding session. It will be well worth it.

Building the hull and deck is the easy part. I think it took me 9 months to do the hull and deck and another two years to do the inside, etc.

[2020]

thanks MicHughV and skipperpete, i appreciate the input. as said, I am not planning on being the welder. I am having the boat built in a pro yard, not homebuilt. My questions I guess are as above re the fiddly bits where separate pieces may need to dovetail or adjoin or abut. thinking final finicky design inputs advice in advance.

[capt jgw]

I've never been involved with the construction of a steel boat, but the commercial boats I ran were all steel. I never noticed any signs of expansion or contraction in the finished hulls, which I think is what you're asking about. They were all painted white with light gray decks so the sun wasn't too much of an issue. One of my own boats was dark green and it got pretty hot in the sun, I'd bet steel would be worse. These were University research boats and a dinner cruise boat so done up to look nice, but not much interior joinery. The steel doors and framed glass windows always opened and closed properly.

[MicHughV]

For sure, I had the inside of my boat insulated. I simply bought some 1" thick Styrofoam in 4'x8' sheets, and cut pieces to fit between the frames, etc, which I glued in place using simple wood glue that came in a cartridge. I only insulated down to the waterline.
I never had a single condensation problem ever.

In later years, I added some " deck tread" material to the deck. This is a 3/16" thick cork/rubber material that comes in various colors. It's great stuff. It adds to the insulation and also protects the deck pain from getting dinged.

Don't over think this problem. I've been on a lot of steel boats of all descriptions, and expansion/contraction problems were all non-existent.

When I was ready to do the interior I bolted 1"x1" wood to all the frames. This gave me something to screw or bolt into when I added all the various wood components, bulkheads, cabinet work, etc