Rebuilding a 44' sailboat

[tcpbob]

Greetings Wynand N

"Shouts home builder"? A round bilge steel boat? Pretty ambitious home builder, especially since the boat was Corten steel. For those that don't know the stuff, it's a low carbon, high tensile alloy developed for bridge building back in the (nineteen) thirties. Resists surface corrosion and twice the burst strenght of mild steel. Very difficult to work though. Also doesn't like a stick welder. Developed for rivetting. A MIG is the way to go.

WhiteBird is a John Bennent design, profesionally built at a ship yard in Kent, England "Steel Fields LTD" which was, from my research a ship building concern that in the last days of shipbuilding in that area, took on steel pleasure craft.... in desperation perhaps. I contacted the designer a few years ago (delighted he was still around) looking for sister ships and he reported that the design was sold to a professional operation who produced them from there and he didn't know how many were launched. WhiteBird was launched in 72, commenced in 70 I think. I found a stamp on a piece of the sole with that date.

The steel was well prepared. This is evidenced by (among other things) the fact there was some black paint that I assume was the good old cancer causing coal tar epoxy in the bilge and everywhere that paint was the steel was absolutely virgin while a spot within an inch that missed that paint was holed from rust. If they hadn't been so stingy with that paint I would have had less work.

under the foam was a layer of what was probabaly zinc oxide primer. In other words, to popular standard. BTW, the foam wasn't in the bilge.

She was built with "best practise" for the period by pros, right down to the teak deck (stupid stupid stupid!!! see Ian Nicolson, "Small Steel Craft" 1971) My experience strongly suggests that NOTHING replaces a well applied paint system and even a well applied system should never be covered by fit out or insulation to the point it can't be readily inspected and serviced.... period! A steel boat done this way and looked after, should never in a hundred years (or more) require gross repair. Anything less..... it's just a matter of time and how much water finds it's way below deck.

When I redid the fitout i did it so everything came apart with a screw driver and a 7/16 wrench, including access to the new SS water tanks. I recomend this highly to any builder or refitter.

There is nothing that will give you a strong opinion like a year and a half of hard labour. It isn't who builds her but HOW. I mean no offense or insult but in my opinion...

[tcpbob]

Hey Wynand N

sorry i got wound up with too narrow focus in response earlier. You do make points I agree with, for example, concerning the miracle cure stuff, converters and such.... absolute rubbish. The darlings of the hardware store guys that don't know boats. And also concerning proper application and interval of paints, including induction period for most eopxy's.

However... there are times and places where grit is impossible on spot jobs and i have found methods to deal with weathered steel that work well. I published the feature in issue #27 this link is a pdf of about 2 meg for the curious.
The article is entitled "Perfection is only 90% effective OR painting on rusted steel and making it stick".

but i still don't like the foam.. :-)

[Wynand N]

Hi tcpbob,

I hear you, but if one look at photo 13 from the top, one with lady in left upper corner, and look at the sea cock that is surely below waterline, one can sea remnants of foam to the hull, especially in the foreground. BTW, most keel boats have their floors below waterline....

As for Corten, this is no wonder material with magical properties and is grossly overrated in the boat building business. I had built three boats in Corten, one with round bilge, and found it no harder to work with as mild steel. Cuts the same, roll and bend the same, weld the same.
The alleged copper in it to combat barnacle grow is also a myth as the copper content is so little it can be ignored. In fact, the hull get painted before the anti fouling is applied, so what is the purpose of the copper if it is covered by epoxy My humble opinion is that Corten is not worth the premium it commands over mild steel.
However, having said that, Corten does have excellent tensile and yield strengths over commercial quality mild steel, and for some people that is worth the extra premium.

As a point of interest, Corten is usually hot rolled and Corten A cold rolled. Specifications differ though - look at the attached graphs.

Corten can easily be welded with normal arc welding and mild steel electrodes, but to get really full strength, it is advisable to use a low carbon electrodes such as E7018 AWS.
I attach a Corten spec sheet from our steel manufactures and if you read under the "Weathering Characteristics" heading, you will find the possible reason for the problems you had with rust. (moisture)

Bob, I agree that there are places one cannot reach with shot blasting, and the way I go about it when building a boat and find such a place, is to dry fit the plate, remove and paint hidden areas and frame/stringer etc, then tack weld in place. I use a liberal of coating in such places. Remember, any protection is better than none.

But let me pat you on the shoulder with your efforts well done as a green back when you started off and gosh, I wish I had a lady like yours that do not mind to get dirty...thats with the work on the boat. You are indeed a lucky man

[tcpbob]

Greetings again Wynand N

The photo you refer to; that is my wife Kay standing on one of the four galvanised water tanks. The "sea cock" you refer to is a filler inlet to those tanks from a hose that had been routed to the deck. The stringer that is at her feet was the point where foam stopped. The bit you might see below that is debris from the removal. For what that all is worth.

Copper in the alloy preventing growth? Never heard of that one so can't comment.

As you note, the virtue in the material is in the strength. "However, having said that, Corten does have excellent tensile and yield strengths over commercial quality mild steel, and for some people that is worth the extra premium." Mate, who DOESN'T want a tougher boat? It's not an afterthought but the central point. Also builders trying to keep weight down by using thinner plate.

You found no difference in bending and rolling? I am astounded in that I found remarkable difference. With my universal panel shaping tool (5 lbs hammer) I can bring mild to shape in a heart beat but i couldn't budge that corten stuff. I could fill a few pages with my personal experience with corten that is totaly at odds with your assesment. In brief, this is an area where I am in agreement with the writers of the book "Steel Away" see pages 28-30. Their bottom line is they don't recomend corten, especially for the amatuer builder, because of the ".. difficulty in shaping.." and the fact it requires a mig welder etc... costs more.. difficult to cut... since the book was written in 86 perhaps electrodes for stick welding have been developed that are better. Also my expereince suggests another virtue of the mig for corten is less heat at the weld.

The problems WhiteBird had with rust was no mystery. It was 25 years of having a perforated/leaking deck thus nearly perpetualy wet foam over an insufficient paint system and inaccesable bilge. I am amazed it went as long as it did.

On blasting, I agree, it is laways the best option but you need to have a plan "B" when it just can't be done. All the repaired sections I did on the boat were blasted and primed before install then all I had to paint was the weld area. I lost count of how many coats went in th bilges. The original blasting on the boat was very effective. The worst corrosion was along the tops of stringers under the foam.

And thanks for your congrats. We did learn a lot.. about the surveying business (gerrrr!) metals and how they are worked and what strategies to use to prevent further problems, questioning every dogma in the trade. Now we commence building a composite fibre glass cat... new lessons! .... I hate new lessons....

[Wynand N]

Originally Posted by tcpbob

You found no difference in bending and rolling? I am astounded in that I found remarkable difference. With my universal panel shaping tool (5 lbs hammer) I can bring mild to shape in a heart beat but i couldn't budge that corten stuff.

Hi tcpBob,

I have to confess. My shaping tools were a little bit more high tech. I used plate rolls and English wheel to form and hydraulic press brake to bend....saves some blood, sweat and tears

BTW, on Monday 14 I start with a Dix 43 radius chine hull (steel already delivered) from scratch to popping the champaign bottle on the bow. This build will be documented and photographed from lofting, through all the stages till completion. If you are interested, you can follow the progress of this project on my website link below, then just follow the Waratah pointers.

Why on earth would you want to join the Tupperware party

[tcpbob]

congratulations on the commision. Steel boat building is a dead issue here where once nearly every cane farmer had one going in the shed. The best monohull builder in OZ is Brent Martz and he builds foam core. 46 foot beauty at 9 tonne.

Tupperware? Cause my old rust bucket wasn't roomy enough to run my office out of. My hobby has turned into a nationaly distributed publication and stuffed up my retirement. So the cat will be floating, roving office. Not to mention that I have seen 25 knots under sail and I liked it! Also being beachable has advantage in GBR and Indonesia and Thailand etc..