Steel centreboards

[GarryR]

Can anyone tell me at what number of Nat 12 steel centreboards were discontinued.  Also is there an easy way of raising and lowering these boards as there seems to be some discussion about the difficutlies of doing that.  If you need a replacement steel plate were the templates similar.  I assume that the steel plate made the boats less tippy - would this be correct?

[tonyelgar]

im not sure what the 12s with steel plates were like, but we have bosun dinghies at work and they have a purchase from the plate forward to a stong point, then aft to the deck and up through a cleat at the centre thwart. the weight of the plate should lower it as you release.
Hope this is of some use.

[johnk]

[JohnMurrell]

Thats a good question!!!!!!!

The class changed from steel to alloy before going the wood route. I know that 2234 definately had an annodised alloy plate and that 2368 was definately wood board. So between 1964 and 1966. Looking at some pics of Lucky Number, 2274, she had a board and was built in 1965.

I stand to be corrected but I believe that a Firefly plate would fit a Twelve. As to the problems of lifting / lowering, its all down to the free running of the blocks - from memory there was a single block attached directly to the top of the plate and two down either side of the hog, just in front of the mast. The plate uphaul line was then lead from a 'V' cleat on the side deck down to the hog block, back up through the plate block and then back to the hog etc. Remember that in those days there were no such things as BB blocks and the old tufnoll ones were (still are!) prone to jamming.........

And Garry, why not give Spud Rowsell a call. He and Brian built loads of boats with plates and might even still have a pattern lying around or know where to get one made. Possibly Clive or Paul Jacobs at South West Metal Finishing in Exeter?

[Richard]

  Garry whats the number of your boat? The class was expecting a rule change from steel to wood and some of the builders built boats with wider boxes to allow wooden boards. Athough the wood boards were a bit thin back in the sixties.N2134 built in '63 had a steel plate now has a wooden board but this might change to carbon after a winter/spring rebuild.
Richard
N2134

[Lukepiewalker]

As a convert to Finn sailing I have experience of shin worrying metal (in this case, aluminium alloy) centreboards. Ours are bolted in as normal, I have a thick (mainsheet/Jibsheet thickness) line going through a block on the front of the centreboard, to blocks forward and then led through cleats on either side to a turning block on the gunwhale. This is then tied to the other end of the line coming from the other gunwhale to form a continuous (as continuous as it can be with a big knot in it) control line. A thick shockcord leads from the front of the board, back to a through deck block, forward around the front of the centreboard case, then back up through the centreboard case again to join the top of the centre board again. The elastic is there hopefully to stop the centreboard retracting in case of inversion. Not sure how applicable this would all be to a vintage twelve, but it works for us.

[Tim Gatti]

Garry - the original steel plates weighed about 50lbs and all the things people tell you about them falling out if you invert - and forget to tie stopper knots in your lines are true!  Ask Ian Purkis who's plate plummeted to the bottom when he capsized at Ripon in July.  

Are you looking for a steel plate?  If you are I've still got the original that came out of N341 - let me know if you want a paper pattern or the plate itself.

The mechanism on N341 was quite complicated with many tufnoll sheaves and yards of hemp rope.  That's the other difference - apart from ball blocks, the rope in the 'old days' turned stiff when it got wet and didn't run through the blocks well so it must have been quite a job to lift the plate with all that friction.

Robin Steavenson discounts the 'righting moment' advantage of a heavy steel plate.

[joneurope]

Hi,
At sea cadets we use Bosuns, they are a tubs, and the centerplates weigh an apsolute ton. I think the centerplates for the 12 were desighned more around the lark centerboard, not the bosun centerboard, so many times have had the cleats or blocks pull out due to the weight.

Jon

[MikeDay]

Re the last message, of course the Lark appeared in the mid 60s, designed by Mike Jackson and based on his March Hare Nat 12.  Twelves with steel centreplates originated in 1936 - and had the only centreplate technology there was at that time - heavy steel ones.  So (pedantically) the design influence was the other way round.

My first 12 - N1766 - a Proctor Mk 6 that wouldn't go at all, had a 30lb plate.  I don't think it provided any righting force at all - unlike the keel of a yacht.  By then (1968) the new boats had wider plate cases for wooden plates and older boats with narrow cases were being converted to aluminium plates.

Mike D
N3496 (with 3kg Kevin Driver c/board!)

[Mikey C]

[quote by=Tim_Gatti link=Blah.cgi?b=Cool1,m=1194880828,s=6 date=1194916598]

Robin Steavenson discounts the 'righting moment' advantage of a heavy steel plate.

 [/quote]


Thats because it's only righting moment if the boat is heeled. We all know flat is fast!

[Ken Goddard]

Garry,
I know of a 'late model' steel centreboard weighing about 35lbs, which I think is still available. I also have a sketch of the type of hoisting arrangement which several respondents have described.

Ken Goddard
N.2300, which definitely has a wooden plate!

[ChrisBerkley]