Pitch in Bottom of Steel Boat

[dpal]

We purchased a 34 foot steel Van Dam sailing boat built in 1974. It has a ¾ keel with a smooth chine. Under the cabin floor are two steel tanks, one for fresh water and one for grey water with a small main bilge between them which holds the batteries. The sides of these tanks are formed by the hull. The bottom of the hull (and hence the bottom of the tanks), where the Vee shape joins the keel is filled with pitch, I imagine about 6” deep.

Being zealous in our maintenance this winter we decide to face the ugly task of removing the 78 rusted bolts holding down the grey water tank cover plate. I suspect that nobody had done this for 20 years, judging from the state of the bolts and the inside of the tank.

What we found is a whole horror story but the immediate concern is what to do about the pitch. Inside the tank it appears to have deteriorated in places into a sandy granular material. In scraping out this material I end up with a very uneven surface with some holes up to 3” deep, a bit like a deteriorating asphalt road surface with other spots relatively hard.

Can I melt it with a blow torch so that it melts down to a level surface? If so what do I then put on top; more pitch or can I use a cement grout? I need to grade the bottom to a well for the suction hose. The pitch is obviously a protection against corrosion and where it is still sound it appears to be doing a good job. I suspect that cement grout would not offer any corrosion protection and may just mask the corrosion that takes place. Is there another material that could be poured on top of the pitch to serve the same purpose?

This is somewhat urgent as I need to move forward. Any suggestions would be appreciated.
Thanks
David Phillips


<hr width=100% size=1>

 

[Birdseye]

I suspect that the best approach is to use more pitch. At least that way you wont have probs of water getting in between old and new.

Am sure thast the old will melt but how do you avoid setting it on fire / inhaling the fumes?

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[jfm]

dpal:
somewhat guesswork, hard to evaluate this by email. I would think a blowtorch has nowhere enough power to make a largish quantity of pitch molten. It will just melt little bits locally. To get a large quantity hot, you need a bigger gas burner imho, then you get into issue of access, ruining the rest of your boat, etc

If I were you I'd look at chucking away the tank lids, flame cutting away any bulkhead-like pieces that form the tank ends, so as to remove all trace of the tanks, as far as possible. Flame cutting is dead easy for a skilled operator, and doesn't create loads of residual heat. Then get tek tanks or someone to make you some custom sized new plastic tanks to fit in the same spaces.

Also, depending on where you use the boat, you could dispense with grey water tank altogether. (you did mean grey didn't you, not black? Grey is for sink, shower, washing machine, dishwasher waste. Black is for toilet waste. I assume you meant grey, as a mild steel black tank would be madness, due to corrosion). Many boats have just black tanks and freshwater, but no grey.

<hr width=100% size=1>

 

[PaulJ]

David,

There are several very helpful and knowledgeable people on this forum but as you have no doubt already discovered, metal boats do have some very specific problems. Another very useful source of knowledge on metal boats is the Metal Boat Society. There is a wealth of information already on their website and if you can't find a suitable answer you can always ask the question there:-

www.metalboatsociety.com

Paul

<hr width=100% size=1>I used to have an open mind but my brains kept falling out.....

 

[tugboat]

As a steel boat owner myself you have my sympathies being faced with this. I have thoughts on the subject but no experience with pitch so will refrain from tendering advice. Regarding the handling of pitch, you might consider consulting fishing boat builders/repairers. It is my belief that they still use it when they lay wooden sheathing on their working decks. I am told that when they replace the timber the steel underneath is like new, so that bodes well for the condition of your steelwork. Incidentally, cement wash is a traditional treatment for bare steel in fresh water tanks.

<hr width=100% size=1>

 

[PaulJ]

Tugboat, do you have any experience of cement wash or cement for encapulating ballast for that matter? I have heard that cement can be used for these things but I also read somewhere that it can cause corrosion....

Paul

<hr width=100% size=1>I used to have an open mind but my brains kept falling out.....

 

[tugboat]

My only actual experience of the use of cement was using a slurry of Portland cement to coat freshwater tanks, and the use of 'cement boxes' as a form of temporary repair to steelwork defects until the next drydock. Regarding the encapsulating of ballast I can only pass on what I have read. It was a common practice years ago when converting wooden ship's boats into yachts that the bilge would be ballasted with boiler punchings and it would be secured by cementing it in place. Trouble was these boats used to leak, so water got between the cement and the planking, the cement not being impervious so the punchings got wet and rusted and the ensuing mess eventually had to be hacked out the hard way or the boat was scrapped. I notice from your bio that you are fitting out a steel boat so if you are thinking of using this type of ballast it is my understanding that it can be a successful method for a steel boat. It is advised to plate over the top of the keel afterwards to prevent any water ingress. The cement adheres well to steel but any impact damage to the keel would possibly destroy the adhesion and could cause some crumbling of the cement. The books 'Steel Away' and 'Own a Steel Boat' have useful contributions to make on the subject.

<hr width=100% size=1>

 

[pampas]

Do not melt pitch with a flame,since you have a large quantity to heat. I would sugest heating a large steel bar (Off the boat) and stir with the hot end. extra pitch would need to be heated seperately and poured. make sure NO water is present or you will HAVE an explosion of hot pitch, wear gloves and gogles with the minimum of exposed skin. Hope that this helps you solve your problems.

<hr width=100% size=1>

 

[AndrewB]

Are you saying that the hull itself forms part of the tanks? This is incredibly bad practice. Surely the surveyor pointed this out when you bought? If you are looking for a long-term fix I would remove these tanks and replace them with proper integral ones.

It is impossible to diagnose without actually taking a look. However, it sounds suspiciously like a past bodge-up that really does need your attention. The 'sandy material' will be the remains of an old concrete base or ballast under the pitch. In grey water, the surface of this will eventually break up. Ideally you want to get out the old pitch, let the concrete dry out, chip back to sound and re-concrete the surface, then repaint with epoxy tar paint. If the condition of the steel underneath is good this will be fine, but sometimes this combination of concrete and pitch signifies a previous last-gasp solution to a failing steel hull.

If you suspect the steel underneath is going to be badly rusty, for example a lot of brown stains around, then a radical but not impossible solution would be to cut through and remove a plate from the outside, and take out the whole mess before rewelding a new plate. This may actually be cheaper and easier than attempting to tackle the problem from the inside.

 

[nedmin]

It might not work but its worth a try if your not in a hurry! Why not wait until we get some really cold weather ie, freezing hard, then you should be able to chisel it as it gets very brittle. Dont forget to wear goggles.Used to do cable jointing in my youth so have had experience of pitch.

<hr width=100% size=1>

 

[mtb]

Re: nightmare

As others have said you'd be mad to attempt trying in vain to melt the pitch as the hull will help keep it cool.
It may sound daft but if that's a big if your hull is still good I'd go for an sds with a decent tile removal attachment nicely sharpened and break it all out. Once you get a start it should come out ok.

I dought it was a bodge as I can see good reason for eliminating that area where debris would collect and would assume it's done a good job since new. As for using the tank sides as framing and so on hey boats are built on a budget and many other craft have this design

HAVE FUN
cheers
Mick

<hr width=100% size=1>

 

[PaulJ]

Thanks Tugboat. My ballast compartments are plated over but accessed through a 6" hole which has a plate bolted over it to seal it. Theoretically they will be sealed but Sod's Law states that inevitably some water will find it's way in there one day and all you say simply confirms my own fears so I think I will give cement a miss......

The ballast is lead ingots and I had thought of pouring pitch in to stop it from shifting but I think there would be so much "heat sink" that the pitch might solidify before it gets to the bottom so I am having second thoughts about that now.

I encapsulated the first compartment in epoxy resin but that was a ghastly job and very expensive so I would like to find some other way to encapsulate the remaining compartments.

Paul.

<hr width=100% size=1>I used to have an open mind but my brains kept falling out.....

 

[AndrewB]

I have this set-up, a concrete/lead mix used as ballast, with a surface skim of concrete. I can't say I like it much, but once there it is impractical to consider replacement. The concrete surface has been inclined to crumble as it got older, particularly under water at the bottom of the bilge. An attempt had been made by the builder to protect it with a layer of fibreglass, but bilge water had got underneath and eventually that too gave way.

After 15 years the steel was looking rusty in places just above the concrete surface, and I worried what it might be like beneath. Three years ago I had the yacht out for several months. Dried the bilges totally then chipped back all the crumbling concrete and about 2" into sound. To my relief the steel underneath the concrete was in perfect condition, and this was confirmed by an ultrasound test. The concrete was replaced, and in place of the original fibreglass it is now coated in epoxy tar paint and finished with Danboline. This looks to be holding well and is easily overcoated, though the treatment might eventually need to be repeated.

Incidentally, it looked as if an engine oil spill had occurred at some time and run through part of the bilge. While making rather a mess, partly soaking into the concrete, it was noticeable that the steel had kept in much better condition in those areas.

<hr width=100% size=1>

 

[PaulJ]

Andrew, many thanks for that...... now I am even more undecided!

Paul.

<hr width=100% size=1>I used to have an open mind but my brains kept falling out.....