Wood/steel composite centerboard/daggerboard

[JimD]

Anyone have any knowledge or thoughts on a heavy steel plate board sandwiched by df plywood faired to a foil? It sounds reasonable to me. The steel would expand and contract according to temperature, the plywood according to moisture, but I'm wondering if on a board of modest size for perhaps a twenty foot boat if this would really amount to much, especially as the board would never be exposed to direct sunlight or any strong heat source. My present boat has half inch steel plate for a cb. I wouldn't bother changing it but thinking ahead for ideas for the next one.

[Mike Vogdes]

Why not just fair the steel and paint?

[bainbridgeisland]

Why bother with the fir? Unless you make it a lot thicker with smaller area you are not gaining anything but drag.

You would need thickness of at least 10% of chord to measurably improve lift/drag more than the flat plate produces. In addition, it would only be an improvement if you reduced the area in proportion to the added lift.

[Venchka]

Jim,

You have to stop reading my mind. It's scary in there! :D

My thoughts:

1. In order to get a really nice foil shape, the steel would need to be cut smaller than the wood. What I'm picturing would be a wood board with a metal core. That way you could fair the leading and trailing edges more easily. Example: 1/2" steel plate, 2 layers of 1/2" plywood and 1/2" hardwood around the perimeter of the steel plate for fairing.

2. Using steel bothers me from a C.G. standpoint. The C.G. of an equal weight of lead could be placed closer to the leading and lower end of the centerboard. No matter what position the board is in, the C.G. would always be lower than the steel plate.

3. If you did use lead, it probably makes sense to connect the lead to the centerboard pivot with a piece of steel flat bar.

Having said all of that, some lead pigs down low either side of the centerboard case and a nice foil shaped centerboard with about 30 pounds of lead to make it sink makes as much sense as anything else.

But hey, what do I know?

EDIT: As usual, it looks as though I should have kept my mouth and fingers quiet.

Wayne
In the Swamp. :D

[ 01-04-2005, 03:41 PM: Message edited by: Venchka ]

[JimD]

Wayne, it looks like we have the same bad ideas :D

[Venchka]

Right, eh? It's a good thing we get them out in the open here before wasting time and money on them.

Wayne
In the Swamp. :D

[JimD]

If only I'd asked before making that osb mast

[Venchka]

Originally posted by JimD:
If only I'd asked before making that osb mastI don't even want to know. :eek: :rolleyes: tongue.gif

Wayne
In the Swamp. :D