centre board

Talk about the older Telstar 26 and 8M
petrel
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centre board

Post by petrel »

Joe,

My boat a Telstar 8m has a centerboard without the large curved quadrant that I think you are referring to. Unfortunately I will not be getting to my boat for at least a couple of weeks so I will try to describe it. It is simply a rectangle with a half circle top and the pivot bearing at the center of the half circle. It has the advantage of not requiring the curved trunk protrusion below the table as in the earlier model Telstars. But I think this curved section of the centerboard has the advantage of closing the back of the centerboard slot? My centerboard requires a mechanism to raise and lower it. The original had a small diameter drum several inches above the centerboard inside the trunk which is rotated by a crank from inside the boat. The small diameter drum has several turns of line wrapped around it to prevent slippage. The line ends then extend to either side of the centerboard and are fastened. The whole system effectively becoming a small pulley driving a larger half pulley which is the top semicircular section of the centerboard.

My boat's centerboard system has been modified with a stainless steel chain as a substitute for the line and a small sprocket which is substituted for the small drum. I use a looped bungie chord on the end of the crank to hold the centerboard down. Curiously it is not needed in the up position as the centerboard floats! The system works very well with the bungie chord allowing the centerboard to also act as depth finder in the shallow waters of the Chesapeake Bay.

The only problem is one has to go into the cabin to raise and lower the centerboard. To avoid this I had considered a modification of attaching an uphaul and a downhaul to the centerboard, running them through some pulleys then inside a tube attached to the mast post and exit through the cabin top and back to the cockpit.

I hope this helps
Geoffrey
JoeWalling
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centre board

Post by JoeWalling »

Geoffrey

That was really kind of you to go to all that trouble to explain it. I think I more or less have the picture now, with your explanation and by looking at the T2 centreboard replacement video. I'm guessing your design was a forerunner to and similar to this. I still can't square my new understanding with Jonathan's photo though. ( Hey, Jon, my wife tells me you popped into the yard today and that she showed you HUSH. Sorry I missed you).

My first thoughts are that I like your stainless chain and sprocket system - I would not like to be worried about wear and tear on ropes and pulleys inside a not very accessible and somewhat water exposed trunk. I don't know if this has been a problem to T2 owners or not, though. I also like the idea of running uphaul and downhauls out through a tube and along the coach roof.

I don't like the fact that I'd have to make up a new shaped rudder and several other new bits ( pulley etc ) and maybe a new mast support (although I'm think of having a new one anyway). I also don't think I'd like a winch handle in that position while I'm sailing. HUSH is a MK2 so not so roomy down below.

My system is simplicity itself. The top of the centreboard has an eye in it. To that is attached a small rope loop with a hardwood handle. I just push or pull the handle and the board stays where I leave it - it being a pretty tight fit. So I'm minded to keep the guts of the current centreboard and trunk arrangement and beef up the rear table support so it can take the weight of a pulley which I would need to fit on it to operate the downhaul - I may also need an idle wheel lower down on the casing to get the right pull - and then build a lightweight rectangular cabinet around the trunk to hide the plug ugly quadrant. The uphaul pulley might be a problem - it will be very close to the centreboard eye. We'll see.

Thanks again.

Joe
petrel
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Joined: Mon Mar 16, 2009 9:29 am
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centre board

Post by petrel »

Joe,

I composed a very technical email and lost it all when selecting preview. It has now happened a couple of times. Very annoying and a waste of time. :evil: :evil: :evil: Here is an abbreviated version.

I realized that in my last email I did not mention that the centerboard is part of an assembly with a frame containing both the centerboard and the pulley/drum. And that the whole assembly is installed from underneath the boat.

I did find Tony Smith's video "Telstar 28 - Centerboard Assembly and Replacement" which illustrates it well and looks identical to the centerboard on my 8m. In the beginning of the video you will see the frame made of white "King Starboard" a polyethylene sheet product available in the U.S. Tony refers to it as starboard which should not be confused with port and starboard. He also mentions how the assembly slides up into the centerboard case.

I prefer the simplicity of the sprocket and chain design over the drum with its many wraps of line, and holes and pins. The frame pieces on my boat have a cross piece fastened at the top making it a more sturdy assembly. Also the sprocket is self contained in the frame and does not require any pins to be added and knocked out. A square drive hole in the center of the sprocket fits a corresponding square drive on the crank which is fitted after the centerboard assembly is in the boat.

If you have any questions regarding the video refer to the time position of the scene and I will try to answer them.
ajaxpc
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Joined: Mon Aug 10, 2009 12:25 pm
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centre board

Post by ajaxpc »

The 8m centreboard must be a good deal more complicated than the one in the MkII.

I've just taken Trina's out - to change its shape and to get a pattern for a new one. I've posted one or two pictures on my blog (http://telstartrina.blogspot.co.uk/)

I can remove Trina's from inside the boat (I need to remove the table first). It was very stiff at first until I realised that the way the boat was sitting on the yard trailer was distorting the hull slightly and pinching the centreboard in the slot.

It took a while to figure it out ...
Hull52
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Re: centre board

Post by Hull52 »

Thought I'd post a shot of my finished centerboard. Four coats of epoxy and ready to be fitted and coated with anti-fouling paint. It has a nice shape. The picture shows the taper at the trailing end of the centerboard.
Image

Here is the leading edge of the centerboard blade. It's barrier coated with 2 coats of fairly thick west/additive. The shape is easier to see with the gray color.
Image

Ready for a final fitting in the case. The case and the board will be coated with black bottom paint for antifouling.
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