Has anyone else ever had problems with corrosion of the rudder fixing bolts on any of these boats? I plan to write a short note for the newsletter complete with frightening photographs but I am just wondering first if I am the only one to suffer! Just back from the annual rudder fixing bolt maintenance session...
Rudder fixing bolts on FWB28
Brian, I looked at some of the bolts a couple of years ago and they were as new. I haven't thought to look again, it will have to be next year since Aeolus has just been out for 3 days for antifouling and I didn't inspect the bolts.
Even if they were bad the pintle would remain in place and no water would enter the boat. Can't understand why you are having this problem and I am not (so far !).
For others concerned, there is a lot of info on the web, just google Crevice Corrosion.
Way back I meant to post a pointer to pictures of the rudder fixing bolt that I took off my previous boat. I haven't let any of the bolts on Victoria Ruth get this bad as I now inspect every year. The nut and bolt in the pictures had probably been on for 2 or 3 years without inspection - this was before I realised the need. See http://s562.photobucket.com/albums/ss65/nealeb/Boat/ for documentary evidence! Had this bolt fallen out it would have left a 10mm hole through the hull deep and out of reach in the bilge...
Any other "28" owners seen this? How's Aeolus, Steve?
The older bolts and the strap were galvanized. The new bolt looked stainless and would have only been 2 years old - it looked fine. The older bolts (10 years) were a bit ragged, but still looked like they could go a few more seasons with no worries. So, I'm not sure why the one bolt was replaced, but it may have simply not been sealed well. I got the boat with the new bolt in place and before she had ever been in the water again. There were stains on the paint suggesting that water had gotten along the bolt hole...
Bottom line for me... the galvanized bolts look just fine. Maybe pulling them at 10 years or so is a good idea, but replacing them with more galvanized bolts and sealing them well seems like the way to go (and way cheaper!). I filled the holes with Boatlife Black Life Calk Sealant.
After reading the posts on the forum, I pulled the bolts from Phyllis May's lower rudder pintle (28', launched 1996) for inspection. Two out of three were a bit ragged looking, but still had plenty of life left in them. The third was nearly new - I suspect it was replaced in 2004 following a survey comment when I bought the boat. Of course, Phyllis May sits in fresh water now - and only for 6 - 7 months a year. I replaced the bolts with new galvanised ones.
To be quite fair to Classic Marine, Roger, I must say that those were just prices that I picked off their web site for standard items of roughly the right size. I suspect that they are also a lower limit on what bronze replacements are likely to cost! Double that for a special?
The three year lifetime figure is purely my own working number and based entirely on observations on my own boats. That's three times the inspection interval, which seems to include a reasonable factor of safety. I'm not sure when the boatyard (Martin?) will hear about this unless he also reads this forum, but I would certainly mention it to him if I bumped into him one day. But given that he went to stainless apparently because of difficulties in getting decent quality galvanising done, I'm not sure what the alternative would be, short of bronze.
Bolt replacement takes me about a fifth of the time that antifouling takes, and about the same proportion of the cost, so it really isn't a big deal. I have spent more time trying to fix a faulty battery switch than I have on rudder fixings (and replaced it with a completely different system but that's another story) so I just try to keep things in perspective. And I spent longer this year changing the anode as a result of a nut seized on to a through-hull stud as well!
The point about the threaded/smooth-shanked bolt was much to do with the fact that a threaded bar presents approximately three times the surface area of a smooth surface. If, of course, the enclosed surface can be protected by Sikaflex or the like, then all well and good. I am surprised at the costings you were quoted and the fact that three years is regarded as a reasonable life for such material, even if it is underwater much of the time. I will be interested to hear what the boatyard has to say about this subject.
Well, as an engineer I have to accept certain compromises, and given that the observed lifetime of the bolts is about 3 years and I inspect them each year, and it doesn't cost an arm and a leg to do it, I shall continue to use stainless. Unfortunately, it just isn't possible to avoid at least one screwed end and if you have one, does it matter if you use two? It is the actual thread inside the nut that goes rather than the "shank" inside the hull. I need a new tube of Sikaflex each year anyway, and this gets to be the first job that uses it! Needed to change one of the anode bolts this year as well, as the nut had seized when I came to change the anode.
However, I have had a quick look at Classic Marine's fittings, and a single strap pintle fitting in bronze of about the right size would cost about £100. Maybe £300-£400 for replacing the whole set in bronze - possibly more if they have to be custom-made to fit. Is it worth it if on inspection next year I need to replace one of the straps? Still, they would match my nice bronze winches, if anyone cared to look!
Whether the section through which the bolts securing pintle-strap is hollow would almost certainly depend upon how high the strap was set; according to my frequent observations of the yard's building techniques, the depth of GRP in the lower-aft sections of the keel is so thick as to be solid for a large proportion of the area concerned.
The use of threaded rod for areas which are continuously submerged invites the ingress of water unless (as brian has done) one fills the thread with some impermeable substance such as Sikaflex. As has been stated, earlier models were normally furnished with galvanised iron, partly because of cost and partly because it was the traditional fisherman's way of doing things but, even then, one had to check for corosion. In the hope of slowing the rate of corosion, several boats had the lower hull-fixed pintles encased in fibreglass filler which, as well as protecting the iron from the salinity of the water, also gave the fitting a somewhat streamlined section; I copied this idea for both "Daisy" and, more recently, for " Mr. Toad"
I am no metalurgist, but long ago I was strongly advised that, if I chose to use s/s fittings underwater, to firstly ensure that it wasn't cheap Chinese stuff, but special marine-grade marine grade s/s; not to use threaded bar, except as a last resort but to use "proper bolts with a smooth shank and a thread only at the very end; and to then seal it with mastic. It seemed such a fag I have since kept to jolly old galvanised. Given the choice... Bronze every time for me, though I guess that the same problems could be found with that too.
One final point which does concern me: sea-water is not, nor ever has been just water and salt. Just a few years ago the whole of the Carrick Roads and its neighbouring creeks turned a deep reddy-brown colour for sevaral weeks. One of the disused tin mines had flooded and spilt its residue in to the river. The water became a soup made of Arsenic, Cobalt, and goodness knows what else; it killed much marine life and corroded anchor-chains in a matter of weeks; fortunately the water is now (relatively?) clear of such polution. So, undoubtedly the composition of the water in which you keep your boat will be a variable factor in respect of the rate of corrosion.
Just don't waggle the rudder too violently, Steve!
Actually, I suspect that the rudder is unlikely to actually drop off in practice. Worst case maybe that one or two of the nuts fall off, and experience suggests that the studding through the hull is not going to slide out by itself (I needed to drift the originals out with a spare bolt and a hammer - not super-tight in there but too tight to force by hand). The bit of thread left will stop the pintle strap sliding off and anyway once the nut has gone, so has the crevice and the corrosion will stop...
Is Aeolus coming out at Mylor? I'm sure that the chandler there will carry 12mm studding and nuts and washers to suit - they seem to be fairly standard items in South Coast chandlers - in case of urgent need!
Colin,
Both Victoria Ruth and Steve's Aeolus were built by Martin at the same time, around 5 years ago, and were launched within a week or two of each other. I seem to remember talking to Martin at the time(1) about the use of stainless fittings and there is a strong possibility that these were the first 28's to have so much stainless on them. Until this time, Martin had used galvanised fittings but had had a lot of trouble getting decent quality galvanising, hence the changeover. So the underwater rudder straps, like the other rudder hangings, sheet horse, and so on, are also stainless and are held on (we hope!) with stainless bolts. With Victoria Ruth and her predecessor, I have been living with "underwater stainless" for more than 10 years and while I am not overjoyed with it, I feel that I can live with it for something as easily inspected as the rudder fixings. As mentioned, at worst I can replace the lot with the boat out of the water in an hour or two, for a cost of around £10 or so. A fraction of the time and money spent each season on antifouling! If these were keel bolts it would be a very different story...
My preference, in order, would probably be something like bronze, good hot-dip galvanised iron, and then stainless, but experience to date with stainless says that it is acceptable subject to above provisos.
(1) but I am relying on my notoriously unreliable memory here, so please don't quote me on this! Perhaps Steve can add something?
Brian, you are right about the cause of crevice corrosion which is also correctly highlighted in the link given by Mike. Because it is very difficult to predict the reliability of the oxide film on the stainless steel there is a high risk of crevice corrosion. So, the normal advice is never to use stainless steel, of any grade, below the waterline. Yes, there are always cases where there are no problems, but in the few cases where there are, corrosion is very rapid, may sesult in danger or even sinking if you lose your rudder and your insurance company may not pay out for a claim because they may say this is normal wear and tear when you use these risky materials. I am surprised your bolts are stainless steel. Did Martin Heard fit them?
I assume your rudder brackets are galvanised, so I strongly recommend you use hot dip galvanised (NOT electro zinc plated!!) bolts. I replaced the lower rudder pintle on my Heard 23 due to wear and when I removed the original galvanised bolts, fitted by Martin 11 years before, they were still in very good condition and probably had at least 5 years life left in them, although I did fit new hot-dip galvanised bolts.
If you use stainless steel bolts you will have to withdraw and inspect regularly.
It's one of those situations where whatever you fit, you are still going to want to inspect it each year! In my case, the bolts weren't quite as bad as those in the link - but they were definitely going that way...
Given that I can buy what is probably 316 grade in my local chandlery very easily, I am happy to settle for that plus "fill the threads with Sikaflex" and annual inspection. I have a reasonable idea of how quickly the stainless does get eaten away, and the better grades are not going to give me more peace of mind as well as being more difficult to source. By "more difficult", I do mean more than crossing the road from where the boat is on hard standing at the moment to the front door of the chandery!
Now, I do have some titanium rod in the workshop at the moment - wonder if I could machine a thread on that?
Higher grades of stainless are more resistant to crevice corrosion - 2205 is better than 316 which is better than 304.
A startling example of crevice corrosion here:
http://www.alberg30.org/maintenance/Steering/CreviceCorrosion/
Mike
Steve,
I first came across this problem on my previous boat, a "baby" 16' gaffer, where the rudder fixing bolts went through a hollow keel section out of reach from inside the boat. Not only would you lose your rudder, but you would have ended up with a couple of 10mm holes in the bottom of the boat. At least on the 28 the bolts go through a solid section! Still, I was sensitised to the possible issue...
On the present boat, the corrosion was eating away the threads of both the nuts and the studs through the hull. There was significant loss of metal involved and there is no way that you would have missed it on inspection - but only when the nuts were removed. From the outside, they looked perfect apart from a slight rusty weep or two. Fortunately, they are easy enough to replace. I used a length of 12mm stainless studding from my local chandler and with the aid of hacksaw and file it only took a couple of hours to replace the lot. The bolts through the rudder are just that - bolts - and I think 10mm but I replaced them as well.
Don't quote me on this, but my understanding of the issue is that it is crevice corrosion. Stainless is only stainless in the presence of enough free oxygen to create and maintain a microscopic oxide layer but in closed spaces like that between threads, the air can't get in but the corrosive stuff in seawater can. At this point, it stops being stainless and just corrodes away... I think that I replaced mine last year and I inspected each and every nut by removing it last weekend. They were all pretty well spotless and shiny new, and I put this down to the fact that I now always fill the threads with Sikaflex before fitting the nuts. Plenty squirts out round the edges and it is a bit of a mucky job but it seals the threads and stops seawater getting in. However, I see possible signs that the rudder strap itself may be being affected and I shall probably remove it completely next year to check the surfaces which mate against the hull. Also, this year, I am not going to put antifoul on the strap itself as I see signs that some corrosion has taken place where the AF has stopped air getting to the steel even on the surface.
I'm definitely no expert on this subject but I have read up a bit on it, and my "fix" is both consistent with my understanding of the symptoms and also seems to work. On my first boat, when I first realised that there was a problem, you could almost have pulled the nut off the end of the bolt, there was so little thread left.
I shall post some pictures on my web site when I get a chance to take them - I still have the old nuts and studs in the garage in the "black museum".
Hi Brian, as you know Aeolus is the same age as Victoria Ruth so I am Alarmed by your post. I shall be lifting her out for a couple of days soon. Do you have any more info? I am trying to get the forum sorted so we can post pictures but not having much luck so far. Steve.
Posted on 23 Feb 2011 - 9:09pm
I noticed signs of rust staining around at least one of the nuts when I was antifouling the other day (VR is usually out of the water for a few months at this time of year) so I shall be inspecting closely this coming weekend.
Maybe it's an allergy or something!