Bargebuilder

They don't!

RS500P repels water during application, displacing it not mixing with it. It may be no better than the Jotan equivalent, but it is very good indeed. This is how Chemco describe the properties of RS500P on their website: Epo-chem™ RS 500P is a unique solvent-free, wet & rust tolerant epoxy primer or primer/finish protective coating. The system’s long-term performance is based on completely sealing the surface and arresting the rust totally. The use of sacrificial fillers enables it to be applied to surface standards as low as Sa 1, WJ-4 or St 2. It can be utilised as a one-coat system by brush, roller or airless spray.

I would have agreed 100% had I not watched the Chemco product be applied to wet, gingered steel in the rain and then monitored it's performance over the following three years. A single coat held perfectly without any top coat. The other advantage of the Chemco system is the minute platelets of glass that are included in the coating, which lay against the steel plate forming a very hard layer which is highly resistant to abrasion and only easily removable with an angle grinder and grinding disc if you get it wrong! Back in 2011 I bought and applied by roller 80kg, 2 coats of RS500P and 5 coats of RA500M, so not only can I state from first hand experience that it performs superbly and is highly scratch and scrape resistant, but also that it is very easy to apply by ordinary roller, so no need for an airless sprayer. I should also mention that my barge is coastal and moored on a salt marsh, a salt water environment that is probably much harsher than fresh water. I'm sure the Jotamastic will be fine and in 5 years Rusty69 will confirm this to be the case, but I can vouch now from first hand experience that the Chemco system is excellent, having applied it to my barge 12 years ago with no sign anywhere of failure or corrosion.

Absolutely right, compared to blacking it is expensive, but I thought you said that you had excluded Chemco glassflake, but applied a different two pack epoxy coating. Is the Chemco surface tolerant primer very much more than other 2 pack epoxy hull coatings? I was trying to highlight that the Chemco product can be applied to relatively poorly prepared surfaces and in atrocious weather conditions, two attributes that might have made your life a bit easier.

Just in case readers are looking to undertake a similar operation, I wouldn't exclude the Chemco surface tolerant primer on the basis of cost. Given the massive effort required and/or cost involved with preparing the steel, a primer that covers and seals as well as the Chemco product, although pricey, may be seen as excellent value, especially in hindsight! When my boat was ashore in the boat yard, there was an old steel motor launch next to it and he prepared the hull to a fairly high standard, but by the time he got round to priming it with Chemco primer, it was brown with rust all over once more. The chap arrived with the two pack product, a tray and rollers and set to work. After an hour or two it started raining and he continued to paint the wet, rusty steel hull. The rain worsened and the paint in his tray began to cover with rain water. He carried on, pushing the roller through the water to pick up the primer. I watched with interest as he finished painting the wet hull and drove off. The boat looked great in its new silver/grey livery, but I thought to myself, it'll never last. That boat remained untouched in the yard for about three years and I kept an eye on the paint job all that time. It only had a single coat of primer and in those three years it never had a top coat, but when I saw it last there was no sign of rust anywhere. If anything can be learnt from this, it is that if you are not sure about how well you are going to be able to do the preparation work, or simply don't intend to spend the time necessary to achieve a perfect finish, buy the best surface tolerant primer. I applied the Chemco glass flake primer/topcoat combination to my barge in 2011 and there is zero corrosion anywhere so far. The manufacturer suggests it could be good for 25 years and given its performance so far, I wouldn't be at all surprised.

If one replaces the Volvo seal at the recommended interval - if only to ensure that a potential insurance claim is paid out in the case of failure - then the saving over a Volvo seal could be many hundreds of pounds over the lifetime of a stuffing box. Of course many people are happy with their dripless seals, but the stuffing box itself will probably outlive the narrowboat, is a simple and cheap diy job to maintain, will still work successfully on a worn shaft and there are no lip seals or bearings to wear or fail. A friend of mine had a PSS seal that caused serious crevice erosion of the stainless shaft from the deoxygenated water trapped after an extended period of boat inactivity. I reiterate, dripless seals work well for many, but for many others, stuffing boxes are still the best option. -

By expensive, I meant £20 for a length of stuffing material every 10 years compared to £120 (plus labour perhaps) every 5 years for a Volvo seal. I'm guessing that many people would pay someone to replace a Volvo seal, whereas re-stuffing a box is a quick, simple, diy operation. I watched my new Volvo seal being installed and I can confirm that the seal protector was used, the shaft was in excellent condition and it was measured with digital calipers to make sure that the correct size seal was obtained; it still spattered water! It never failed, but I got fed up with it and lost confidence in it and after two years and 600 hours use, I had it replaced with a stuffing box. My stuffing box gets a turn of the greaser at the end of each day's cruising and the collar may need adjustment every two or three years. I have used PTFE stuffing and although the dripping is minimal, the box doesn't warm up. The bilge doesn't get wet because I have a small dish to catch the drips. There really isn't anything to fail and over the years it will be much cheaper than any 'dripless' seal.

The Volvo 'dripless' seal is popular with some, but I inherited one when I bought a second hand boat and it dripped, in fact spattered when the shaft rotated. Imagining it to be old and worn I had it replaced, which wasn't cheap. Upon launch it was 'burped' to ensure there was no trapped air and greased with Volvo's special grease. The shaft, prior to fitting the new unit was inspected and found to be in excellent condition. The new one also spattered water when the engine was in gear! Perhaps I was unlucky, but I never felt confident in the Volvo seal. Do Volvo not recommend replacement every 5 years or 500 hours? I do 300 hours cruising in an average year, so Volvo would have me replace it every 2 years! It may last longer for many, but it if failed and the boat sank, I wonder what an insurance company would say if a claim was made. The two lip seals that stop your boat from sinking are tough, but incredibly fine. They may spatter or drip with age or wear, especially in silty, abrasive water. Replacement may, for some people, need to be frequent and is expensive. I've replaced mine now with an old fashioned stuffing box. No chance of a catastrophic failure, just a few drips of water into the tray beneath whilst motoring and completely dry when the shaft isn't rotating. Very easy and cheap to re-stuff every 10 years or so: I feel a lot happier now.

Very useful. Thank you for that.

I watched it on iPlayer.

When I enquired of learned folk, I wasn't expecting a reply from a scholar. Thank you so much for the information and the link. I was hoping to take the ebb from the Dog-in-a doublet, spend the night on the free waiting pontoon just past Sutton Bridge and do the Wash leg to Boston the following day: any suggestions concerning timings would be appreciated.

Would any of you learned folks know how much later high tide is at the Dog-in-a-Doublet lock than it is at the Wisbech cut for which I have a tide table?

I am impressed with your depth of knowledge and deep interest in the subject. Thanks for being so generous with your expertise.

I imagined, obviously incorrectly, that the minute droplets of water caught on the filter surface would, with time, get larger and fall off, but remain on the 'dirty' side, but you are saying that once large enough, they push through the filter to the 'clean' side. That certainly would explain the recommended flow direction.

Hi Tony, thanks for the reply. I agree with you, that the fuel should flow as you describe. The CAV filter body I am looking at has two inlets and two outlets identified by arrows and the inlets open directly above the filter element. I have a filter element that is punched with holes at the top and has baffled, directional slots at the base. The filtered fuel having passed through the element top to bottom into the water bowl at the bottom, passes up the tube in the centre of the element and on towards the engine. That is the way the arrows intend it to work. I would prefer to plumb it the way you recommend in your first paragraph for the reasons you mention, but this seems not to be what the manufacturer suggests. Can you think of a reason why the fuel flow cannot be reversed so that it is introduced down the centre tube and into the water bowl first?

This is a very old thread, but can anyone think of a reason why a CAV filter/water separator couldn't be plumbed in in reverse, so that incoming fuel first enters the water bowl, passes up through the filter element and out through its top on its way to the engine? The arrows on the filter head indicate the reverse, but maybe drops of water and bits of muck would be better held in the water bowl before the fuel passes through the paper element; any thoughts?

If it's on the market, it's very well hidden. I think it's a Frobisher class. It looks like it has a steel hull with possibly a grp top, but that's a guess based on appearance. If it has a grp hull then it might be a find, but it doesn't look like it.

Just found it here: https://waterfreedom.co.uk/ Under: Frequently asked questions, Water, Can I drink the water? With the filter they suggest using, after a few weeks of use, you'd have to wait a very long time for enough water to fill a kettle.