Centerboard Troubles

[TIM WEBB]

GL, I think what John means is that some DS2's have a CB pivot bolt, and some have wedges/plates/pivot pins that hold the CB in position. Dunno if the pivot point is in the same location for both. I'm not familiar enough with the wedge system to know if the boats with that system use a through-board pivot pin or not, or if it's in the same location as the pivot bolt boats. ChrisB?

[GreenLake]

How could they be class legal if geometry is different for some angles? How would they fit the same slot?

[Alan]

I've got a wedge DSII, so I can tell you that there is a through-board pivot pin, but it doesn't penetrate the sides of the centerboard trunk like the pivot bolt on the earlier models. It only goes into the wedges.

[GreenLake]

But the place where the board pivots is the same in the plane of the board right?

[Alan]

It makes sense that they would all have the same pivot point, but all I know about from my own experience is the wedge design.

[OldandBusted]

Here are some photos:

[jeadstx]

It does make sense that the pivot hole would be in the same place, but I have to wonder why D&R sells the DS1 CB with it's square hole and the DS2/3 CB without a hole drilled in it.

John

[kokko]

Yikes! You need to grind out the cracks and fill it with a marine epoxy filler. You might want to cover it with epoxy and glass tape too.

[OldandBusted]

That's what I was thinking. Could these cracks have a large impact on performance?

[GreenLake]

U bet. Destroy the flow over the foil. Lots of drag and no lift...

Use polyester marine filler. Probably cheaper and cures faster. Try bulk up then sand a better foil shape before glassing

[OldandBusted]

That would explain several problems and thank you! Is there a place to read more a out the correct shape/ dimensions for the foil?

[UCanoe_2]

Your centerboard definitely did not come that way from the factory!

There are lots of threads on the forum about centerboard repairs. Here are links to mine, which are current this year:

http://forum.daysailer.org/forum/viewto ... =11&t=4266
http://forum.daysailer.org/forum/viewto ... =11&t=4356
http://forum.daysailer.org/forum/viewto ... =11&t=4374
http://forum.daysailer.org/forum/viewto ... =11&t=4432
http://forum.daysailer.org/forum/viewto ... =11&t=4469
http://forum.daysailer.org/forum/viewto ... =11&t=4466

Also see my photo gallery.
http://forum.daysailer.org/forum/galler ... bum_id=120

There is a dimensioned drawing of the centerboard profile (side view) in the DS class rules here on the forum.

The stock cross section is pretty inefficient. The ideal is supposed to be a NACA airfoil, developed IIRC in the 1920s or 30s for slow speed airplanes. You can do a web search and find lots of information for creating one of these shapes. Since we live in the Computer Age, most of the methods you find will involve computers in the guise of various programs or Excel spreadsheets.
Here is one from Duckworks:
http://www.duckworksmagazine.com/07/how ... /index.htm

All that seemed overly complicated to me. After all, in the 1930s before computers were invented, draftsmen plotted these foil shapes using compasses, straightedges, French curves, and wooden battens. I used a graphic solution to make a template for the foil shape of my board. The critical dimensions are chord length (fore-and-aft width of CB), leading edge radius, thickness of board, and distance of maximum thickness from leading edge. Unless you are racing it doesn't have to be perfect -- mine certainly is not. Almost anything would be an improvement over the very flat factory shape. As you may have read elsewhere, it is important for the trailing edge of the CB to be squared off about 1/8" thick, and not tapered.
http://forum.daysailer.org/forum/galler ... ge_id=1537


My new foil shape turned out almost 1/2" thicker than the stock CB. I spent a lot of money on epoxy before realizing I could build up the thickness with wood strips. Also, I filled in a lot of the missing pieces with epoxy putty, about $6 a tube in the plumbing department at Lowe's. I probably could have saved a lot of time and money by building a new CB. You may decide the same depending on your skills and tools available. There is another recent thread on building a new CB, but I am too tired and cross-eyed to find a link at the moment.

You are fortunate to have lots of helpful people on this forum with lots of knowledge. It is a great resource.

[GreenLake]

This thread has lots of my input : Severely cracked leading edge of centerboard DSII

[OldandBusted]

Wow! You guys are amazing and I couldn't agree more about this forum. Thanks to everyone!

[OldandBusted]

By the way, what is a PO?