What are the pitfalls of a wooden superstructure?

[David Mack]

New steel is not cheap, but dismantling the interior of the boat to a point where it's safe to weld a new cabin on and rebuilding it again afterwards is the really expensive part of having a cabin replaced in steel.

 

Some boats have had wooden cabins skinned with welded steel with no interior dismantling. I believe President's butty Kildare has a 3mm steel skin fitted over the wooden cabin, with little preparation beyond removing the exterior fittings, handrails and slide rails. The steel skin provides the waterproof envelope, but relies on structural support from the wodden cabin below. I guess the old wooden cabin skin must be a bit charred along the weld lines.

[Teadaemon]

Some boats have had wooden cabins skinned with welded steel with no interior dismantling. I believe President's butty Kildare has a 3mm steel skin fitted over the wooden cabin, with little preparation beyond removing the exterior fittings, handrails and slide rails. The steel skin provides the waterproof envelope, but relies on structural support from the wodden cabin below. I guess the old wooden cabin skin must be a bit charred along the weld lines.

 

That would require a very brave (or foolish) owner, and a welder that wasn't put off by the prospect of being sued in the event that they burned out the boat.

 

Whilst it may have been done in the past, there's no way that as a surveyor I could ever condone that method, as sooner or later it's bound to result in a serious fire.

[GSer]

Cygnus came with two parts of the hold converted with wood under the cloths (only recently added) a quick inspection revealed rot in the corners where it met the steel on the rear conversion and where it met the cratch board on the front conversion, i'm only guessing but I think the conversions were done in the last few years, it appeared to be down to water ingress on the joints, but steel screws didn't help and the whole kit and caboodle did not appear to have been treated with any sort of protection other than having some builders paper between the ply and the supporting structure. It was built with what appears to be mostly pitch pine but elements of the framing appears to be of a lesser pine.

 

So there are good and bad wooden tops, i met a small cruiser a few weeks back that was built in teak and magogany ply I think it was at least 60 years old but still looked great and the owner assured me it was (mostly) water tight.

 

good luck

 

paul

[Neil2]

Teadaemon makes an interesting point but I don't think it stacks up nationwide. I've seen wooden boats in the North that have been completely rehulled in steel and if you go to the midlands or yorkshire or any of the shipbuilding towns you will find legions of welders for every wooden boatbuilder. It may well be very different in East Anglia. Also, the point at which a cabin needs replacing is probably about the same point at which a refit becomes necessary, so the interior gets stripped out either way.

[carlt]

Also, the point at which a cabin needs replacing is probably about the same point at which a refit becomes necessary, so the interior gets stripped out either way.

Perhaps, in your steel hulled, ply lined, mdf clonecraft but look inside the derelict wooden boats at various Broads yards and you will usually see a perfectly sound interior wrapped in a rotten hull and topsides.

 

My 53 year old wooden boat is getting new cabin sides but the 53 year old fit out will outlast me.

[camboater]

There's nothing intrinsically wrong with a wooden superstructure if they're done well, and as others have mentioned, they can have advantages over all steel construction.

 

The hull to cabin joint is a critical area - it needs to be made in such a way that water can not get into it, and if the bottom of the cabin does end up sitting in water then there's a good chance it's going to start rotting. If it is sheathed with glass cloth, then epoxy is a much better resin to use than polyester, as it's far less permeable to water and sticks to wood a lot better. Beware any patches or repairs - a patch has to be very well done to last more than a few months, and if one area has needed a patch, there's a fair chance that other areas will need patching in due course. In that situation, it's often easier to bite the bullet and re-skin the whole lot, rather than keep patching it up. Look carefully around window frames and at any point where anything is screwed or bolted on to the superstructure.

 

In addition to the above, when I'm surveying a wooden cabin I look for blistered or flaking paint, grain visible through the paint, sealant or other signs of running 'repairs' (as they're normally temporary bodges at best), and any signs of water pooling on or around the superstructure. Inside the boat look for water marks on the ceiling or walls, any visible mold, and have a good sniff - you can often smell rot even if you can't see any sign of it. I have a good moisture meter (a Tramex Skipper, designed for marine use) which can tell me if there's moisture deep inside the wood, and I use that to get a general idea of moisture levels, as well as to confirm my suspicions after a visual observation. If I can probe any suspect areas without damaging the finish, then I normally use the tip of my swiss army knife's small blade - if it slides in with little resistance then the wood's definitely rotten (if I'm unsure about an area I often try first with the blade parallel to the grain, and then in the same place across the grain, if the resistance is similar both times then the lignin is being broken down, normally by rot).

 

Cambridge and surrounding area is somewhere I'm happy to travel to, so if you're looking for a surveyor then feel free to PM me.

 

Thanks, very helpful. The particular boat I'm looking at is in West London (I would be cruising to Cambridge over the summer), so presume rather a long way for you to travel.

[Teadaemon]

Thanks, very helpful. The particular boat I'm looking at is in West London (I would be cruising to Cambridge over the summer), so presume rather a long way for you to travel.

 

Depending on how big the boat is (and therefore how much I'd charge) I may still be able to give you a competitive quote for a survey in the London area, and if you wanted me to do the job then I'm happy to travel there.

[koukouvagia]

I must admit I like wooden cabins, butthe one on the butty has been a real pain. The problem is not so much wood per se, but it's where wood and metal meet. In the end I got fed up with dealing with this, so now the cabin is clad in resin with fibre glass tape along the joins.

 

I spent yesterday dealing with the join of the wooden handrail and steel roof on the motor. This had a Sikaflex bead to stop water getting in, which has worked well for a number of years. However, I noticed that this was breaking down and damp was beginning to penetrate. I've now used the West system resin and fibre glass to run along the join. Once it's been sanded down, the join will be invisible.

 

 

[Chris Pink]

Real sikaflex 291?

 

How long did it last? Is it coming away from the substrate? And is it a failure of the substrate rather than the sikaflex?

[koukouvagia]

Real sikaflex 291?

 

How long did it last? Is it coming away from the substrate? And is it a failure of the substrate rather than the sikaflex?

 

It's been there for twelve years - so I suppose I can't complain. I can't remember what kind of Sikaflex it was. I didn't know there are different varieties. You may be right about a failure of the substrate.

Edited June 2, 2012 by koukouvagia

[smileypete]

Real sikaflex 291?

 

How long did it last? Is it coming away from the substrate? And is it a failure of the substrate rather than the sikaflex?

I'd say a well made expansion joint would have been ideal, but frequent repaints can help too.

 

A lot can be learned from reading the forums of the lumpy-water boat brigade, also poking around failing wooden boats, helps build a good understanding of things.

 

cheers,

Pete.

[Caprifool]

My Ålandssnipa with a Albin 23 engine was all pine and spruce. Built in 1923. Had her for 8 years and sold her for a profit.

[smileypete]

Just remembered, a good lasting 'temporary' repair (cough cough! ) for these sort of cracks at joint lines is to burnish down a couple of layers of 2" aluminium tape on the paintwork then paint over with topcoat. The layer of thick alu foil takes movement a lot better than paint film alone.

 

cheers, Pete.

~smpt~