Keels and Rudders: Engineering and Construction

[Eric Sponberg]

To all:

My article "Keels and Rudders: Engineering and Construction" has just been published in Professional Boatbuilder, Vol. 96, August/September 2005, page 72. Have a look if you are interested. It is also available on the PBB website at www.proboat.com. Enjoy.

Eric

[WildCherry]

Good Article. Congratz

[mojounwin]

Thanks for the read Eric,
Very interesting stuff.
Cheers
Mike

Eric, I enjoyed the article very much.It's a keeper and a great reference.
I was very intrigued by the story of the trim tab being accepted as an emergency rudder!
Would you expect that some of the current crop of canting keel boats with a somewhat forward foil that use a fixed foil/flap combinaton would be able to steer with it as well? ( with the rudder neutralized or not there)

[yipster]

looking forward, probably in the mail tommorrow

[Eric Sponberg]

Doug,

I would have to look at a specific design in order to judge the turning ability of a forward foil. One can expect that any foil at some distance from the longitudinal center of buoyancy and the center of the lateral plane area which can act at some adjustable angle of attack to the flow will generate a turning moment. So on that principle, yes, such a foil should work for steering.

Eric

[Lew Morris]

Thanks for an interesting read. It was especially helpful to me since I'm now up to my neck in rebuilding the swing keel on my old McGregor 17.

Of particular interest to me is Bagatelles keel bulb/blade pictured on page 87. If I may, for the moment, assume that the bulb is lead, what surface preparation was performed to optimize adhesion of the laminate?

I visited West System's website and checked their information and it would appears that a pretty good joint can be made directly to lead. Is this your experience?

Specifically: I have stripped the entire FRP skin off the the .56" x 4.0" steel armature down to the lead bulb. I have left the remains of the molded FRP skin that surrounds the bottom of the bulb (leaving about four inches of lead exposed).

It would simplify my life, immensely, if I can go from my new wood/foam blade structure directly onto the exposed lead, and hence onto the old FRP.

With the understanding of no liability whatsoever, your opinion would be appreciated.

Regards,

Lew

[Eric Sponberg]

Boat builders bond FRP onto lead all the time. The lead casting needs to be properly sanded with coarse grit sandpaper and lay up directly onto the lead. Epoxy resin works best, but polyester boats have FRP bonded onto lead regularly.

Eric

[Lew Morris]

Thanks for your input Eric.

Muchly appreciated.

Lew