Thread: Centreboard material

So how should I shape the edges of my TS16 centreboard (in simple terms or preferably diagrams )?

What is allowed under class restrictions for racing?

And where can I get it done in Adelaide? Please! Boatmik?

If only 38mm fairing is allowed from any edge, I would rough out the fairing with an angle grinder, then finish with files. Use a straight edge such as a 1m rule to ensure the fairing is flat. I will state that I have never constructed a centreboard, but I have ran an engineering business for a few years.

There are a number of galvanising places in Adelaide that would then be happy to galvanise the board. These can be found in the yellow pages.

38 mm from each side is a pretty thick board (about an inch and a half) which sounds about right for a foil section on this size boat. This offers a lot of foil shape options, though the slab sided foil will be the easiest to make.

I don't have an image handy, maybe Mik can post one to show how simple this shape is to make. I would use foam to bulk up the board on each side, then shape it with a sander, then sheath it with a few layers of fabric. You could use wood to bulk it out to the 38 mm dimention, though it's harder to sand then foam.

Unfortunately (perhaps), if the boat is to be built within class specs, it has to have the plate CB. If not built to A-class specs, it will probably be worth less, even if it does sail better in every way.

The rules clearly state 38 mm from any edge, which suggests considerable latitude in shaping the plate. The obvious option is to discuss this with the class racers. They'll have crossed this bridge, likely several different ways, in regard to bulking out the sides of the plate for a foil section. Then again, you have to ask yourself how much class racing you'll be doing.

it is expensive but, when a designer stipulates a metal centreboard, I use bronze....

Expensive is not my favorite word at the moment. I think I will stick to Galv.

The folks at Duck Flat are sourcing a quote for me and I have asked a few more engineers. Though they dont seem to eager to do such a small job.

Originally Posted by PAR

The rules clearly state 38 mm from any edge, which suggests considerable latitude in shaping the plate. The obvious option is to discuss this with the class racers. They'll have crossed this bridge, likely several different ways, in regard to bulking out the sides of the plate for a foil section. Then again, you have to ask yourself how much class racing you'll be doing.

class measurement rules:
http://home.iprimus.com.au/youngenr/ts16/TS16MF.pdf item #27.
Explanatory drawing on sheet 8 ...
i.e. the 8-10mm max thickness plate can be shaped to 38mm from its edges.

Dunno about the USA, but here in Oz, adding cheeks to fatten the board would
be regarded as 1. exceeding 10mm max thickness & 2. 'fairing' or shaping more
than 38mm from the edges.

As a non-racer, I don't care. If the effort to build something better returns
worthwhile results, then I'm all for it. As I've said before, if I ever own
another, I will take it waaaaay out of class to make it a more comfortable &
covenient cruiser. But for TS16s, being a non "A-Class" (out-of-measurement)
boat devalues it a lot if ever the owner sells it. From $6K - $9K down to $2K-$4K.

There are a bunch of engineering shops just off South Road thru Melrose Park
& St Marys area. I got some coloured anodising done at one of them, but not
cheap. Those places' bread & butter is production runs of hundreds or thousands
of widgets. One-offs are a PITA, & lots of places don't want to do them.
More trouble than they are worth.
Good luck !!

Originally Posted by PAR

Lastly, I've made boards (rudders mostly) from HDPE and UHMWPE. These are high modulus plastics and completely inert and also neutral buoyant (doesn't float, but doesn't sink either). They are easy to machine, but you have to setup some sort of way to cut them into a foil shape. I use a template system for a router, which amounts to foil shaped ramps the router base rides on. This is really easy and fast, but these materials aren't cheap. They make perfect rudders because they need only a tiny weight to sink them. As a centerboard they are self lubricating materials, so jamming in a case isn't going to happen or sliding in a kickup rudderhead. They don't take fasteners well so through bolts are the only fastening options, but not a deal breaker in these applications. They don't promote sea life growth either, which is way cool too. If I could afford it, all appendages would be made from this stuff. In fact, I have a supply of cutting boards I get from the local discount store. It's HDPE and I use it for making all sorts of things, like linings for bee holes or fairleads, blocks sheaves, bushings, mast steps, handles, etc. Any place I need something that will rub against something else, bear weight or offer a sanitary grip. It also makes a nice cutting board for filleting fish.

Hi Par, yes I find HDPE useful stuff. One question, how do you find it lasts with UV exposure? I had a couple of Yost style HDPE kayak frames I didn't need any more, I left them outside for a couple of months as a test, they deteriorated, became quite brittle from the sun exposure.

Ian

There are different formulations of HDPE and it naturally goes that UV stabilized material are the obvious way to go. In lue of this, a cover or the new "plastics" paints such as "Fusion" will keep UV from depolymerizing the HDPE. When in doubt, I use Fusion paint (a Krylon product), just to be sure.

Originally Posted by hereselmo1

So how should I shape the edges of my TS16 centreboard (in simple terms or preferably diagrams )?

If you are going to glass over, I'd use a tapered bull nose on the leading edge (think about the shape of an aircraft propellor's nose cone if that makes sense). You could use timber screwed to the plate and glass over.

For the trailing edge you are better off with it left square across so it works as a turbulator. It will actually produce less form drag than a knife edge would.

Elmo, First contact the association in your state and others ( may be a drive to fetch a freebie?) - someone may have an old board. thats how I got mine when i built a TS16. Bit of a cleanup and galv good as new nearly. Second failing that make a template and find some engineering place to laser cut it for you then galvanise it. If you can build a boat then this is easy. You'll save Duck's overheads. My mainsail ( for a feather pram) was half price sourcing it myself !!! Dont try and get fancy it'll be a PITA if it goes wrong. I used to drag my board through the sand, bang it on rocks, raced with it ( unsuccessfully ) still looked good after. Stay within the rules. The racing guys will be only too happy to supply info if you ask. BTW racing is the best way to improve your overall sailing, just dont take it too seriously. Sorry cant advise on fairing except that mine was rouded at leading edge and vaguely knife like on trailing edge. Do NOT put a slot for pivot pin. Boarrd can fall out.
I think I used a piece of SS rod for pivot, just put a dab of sealant behind the pivot covers in the case logs, then you can check it every now and then