Which is more effective - a sort of antifouling question?

T

tillergirl

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TG has a long centre keel which is also wide. So wide in fact that she will stand on it on a flat hard. The result of this is that she is always sitting on the keel when I antifoul (done again this week for the second time this year). This means that the keel bottom /forums/images/graemlins/confused.gif has not been freshly antifouled since Spring 2004 when I was ashore to do the keelbolts.

Now - is it better to get the diver to scrape off this year's crop of barnacles to expose two year old antifouling or to allow the barnacles (recently given a headache while on the hard on Wednesday) to remain thereby hoping to stave off weed growth?
 
I winter in a mud berth and only get lifted every five years or so and consequently the bottom of the keel doesn't get any attention - unless I try and sand it off by gently rubbing over the Buxey Sand! (invention that bit I'm afraid)
 
Is the bottom of the keel lead, iron, or timber? If it is either of the first two,I wouldn't worry too much, but if it's timber then the antifouling is as much to repel the dreaded teredo and gribble as much as to deter weed and barnacles.
Peter.
 
The keel of my old gaff ketch is all timber, as the ballast is all internal lead pigs. I have nailed sheet copper to the underside, and wrapping a couple of inches up the side of the keel to try to combat this problem. I haulout annually, but it is on to a railway cradle which has transverse bars to support the boat. I can't paint antifouling where the bars are, but I was able to fix a cleat to the cradle at the front and back to raise the keel off the bars sufficiently to get the copper into the gap. I have to re-do this because I hadn't seen the need to give the copper sheet its own anode, and it has eroded/corroded way in places.
Peter.
 
Now I like that idea. That could be very worthwhile for me and not that expensive given the majority of the bottom is iron. There is, however, a piece of the deadwood that is a bit uneven as though she has sat on a chain at some time which could be a problem to get a close fit. I'd have to work on that.

A couple of questions please?

Do you back the copper sheet with anything to get a watertight cover? Like you I'd have to be inventive when craned and chocked though I guess the yard could jack me and move the blocks having done the bits in between. Thickness of the copper sheet? I guess also I'd have to be a bit less blase about driving her up onto the hard. At the moment I tell myself a little light scraping on the gravel helps clean the bottom but that would clearly tear thin copper. Interaction between copper and the iron keel? Clearly it would 'butt-end' and not overlap so I guess there is a vulnerable 'edge'
 
They used to bed the copper in tar, I guess you could use the same or even linseed oil putty, thinned, maybe white lead? But Why would you need an anode on copper? Anodes dont protect copper or I didnt think they did.
 
Well, I thought that it wouldn't need an anode too. Copper sheet on a copper-fastened boat? How else do I explain the holes that make it look like it has been eaten by moths?

When coppering was a more regular practice the copper was backed by felt steeped in Stockholm Tar. The construction ndustry use a product called geotextile, which is a felt made from a rot-proof fibre. It comes in a range of thicknesses on rolls 12ft [one road lane] wide. Stockholm tar is still available. The copper sheet that I have is quite thin; about 22g, and would certainly suffer if it were landed on rocks, etc.
Peter.
 
Peter

Thanks, very helpful. I think I'm sold on that. I might just see if there are two or three others who want a crane out this year and so do the copper sheeting. I am also toying with the idea of removing the bilge plates (dead easy to do). I am coming to the conclusion that the drag is outweighing the anti-leeward effect (if there's any). In a great sail this afternoon, hard on the wind in 18-22 knots apparent, there's a great whooshing and whoomping from the windward plate in the seaway.
 
She's a mongrel (if she'll forgive me). The previous boat built was a Vertue and having spoken to the guy who had the Vertue built I have been told that the owenr who commissioned TG from Seacraft in Leigh on Sea (near Southend), wanted the basic shape of a vertue in the bow, with the Launrent Giles 'knuckle'. However, she is bigger 32' and beamier 9' 1", not a lot by modern standards but beamier than a stretched Vertue would be. Under the waterline she looks like a Golden Hind (not sure when MG did that design). Seacraft built a few MG designs apparently so I guess the idea came from that experience. They also used to build Bawleys and the transom and hind quarters are very similar in appearance. She is shoal draft 3' 9" as befits a Thames Estuary craft and had two iroko bilge plates fitted, possibly originally. However, there is also evidence of a hole in the port beam shelf in the spot where you would put legs (I've replaced the starboard beam shelf). The Iroko bilge plates went in the 1980's, last heard of in a shed in Wales where they were removed and replaced by a shipwright (who used to own Telegraph, a Boston Smack that used to reside in the 90's at Maldon). The replacement are steel plates, probably just over half the size of the wooden ones, in order to reduce drag. I am convinced the starboard plate isn't perfectly aligned (what bilge plate is?) since in a force four or five to windward there is a lot of 'thromping' going on which doesn't happen on a port tack. But then she doesn't point as well on the port tack! I would really like her to have a centreplate but I guess I'm not going to embark on that sort of change after 40 odd years. Built in 1964 when of course a certain troop of long legged luvelies jigged on stage at the London Palladium - hence the name (the girls were known as the Tiller Girls) The name results in the most shameful and appalling dishonesty on the part of SWMBO who usually can be heard fibbing about her past in any new port rather than securing lines.
 
Looked up the Good Hope. Yes similarities certainly on the bow and sheer and below the waterline, although the transom is more Golden Hind. Interesting that she had a draft of 4' 3" on a LWL of 30.5ft and LOA of 38.5. Draft was restricted to 40% of beam. TG is 41.3% I see that was launched in 1968, four years after TG.

The turn of the bilge and run aft is very similar. MG describes the shallow draft as needing a stiff vessel, never to heel far in a fresh breeze and her hul was therefore given a bold midsection with a firm turn to the bilges, almost in the manner of an East Coast fishing smack. Also to reduce leeway there was a need to make the vertical sides of the keel below the garboard as deep as permissible. Seacraft have certainly done that.

I don't think the midsection is quite as 'bold' as the Good Hope (I assume that means the very full bilge(?) of the Good Hope. TG is not quite so pronounced.

I see that according to MG, Seacraft built the Cockler Class (smaller at 25 LOA and with centreboard) and Tringa class 27.8 LOA and then the Barcarole class at 29.2 LOA with 3.2' draft. Only two Barcarole's were built by Seacraft with centreboards, others being built with "deep bilge keels". Barcarole's did, however, look like TG.

Thanks for the prompt. Made interesting reading for me as we bask in 32 degrees today!
 
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