Window shopping for design work.

[quilbilly]

I have a twenty-seven foot trailer sailer of my own design that I am quite proud of and happy with but one can always make things better, right? It has a ballasted daggerboard that started as a steel foil shaped fabrication that I then filled with lead and epoxy encapsualted and faired. After using the boat the first year and being that the boat is only 8 1/2 ft wide I wanted to add some more ballast. So I attached a bulb on the end which brings the total weight of the daggerboard to 1850 pounds. There is a eight purchase block and tackle arrangement running to the genoa winches and I can raise it alright but it is certainly not something I do routinely. I calculated that an 1100 lb bulb on a magically weightless fin would give the same righting moment and given the choice I would actually like to raise it easier. And with a bulb I could actually stilll sail in shallower water without the fear that raising the steel daggerbord moves the c/g up much quicker than a bulb would. So my question is what would be a ballpark figure to have someone more knowledable than myself design a relatively lightweight composite fin for this 1100 lb bulb. The daggerboard itself is six feet long overall, with a two foot high retangular section that is about 5"X24" in plan view sliding into the rectangular daggerboard case itself. The foil shaped portion is all below that and fairs into the rectangular portion at the bottom of the boat.
As with most things I need to decide if I really want to redo an acceptable situation so I would like some idea of the cost of the design. I can figure the rest out from there. Thanks Todd

[Raggi_Thor]

You could ask Phils Foils, www.philsfoils.com, not tto far from you, in Canada.

Didi 26 (from www.dixdesign.com) has a 400kg bulb (900 pounds?) and I think a laminated wood foil with some glass and epoxy weighs 35kg.

You could also use this extruded aluminium foil,
http://www.mboats.no/Hardware/hardware.htm,
with some internal stiffeners.
We just sold one to a builder of a Didi Mini.

[Sean Herron]

Hello...

Also mail this post and photos to Eric Sponbergs' site ...

See http://www.sponbergyachtdesign.com/index.htm ...

SH.

[Raggi_Thor]

Sean, what do you mean?

[Sean Herron]

Hello...

I mean - oh I know - the cherry tree out front - it needs trimming...

Mind - it is the weekend - and the whiskey flows like a river...

SH.

[Raggi_Thor]

OK, it's late night here, but in Vancouver?
Saterday afternoon?

:-)

[Sean Herron]

Hello...

I start at the stroke of noon - I married British and she just stands there in front of the clock with a cork screw in both hands...

Always polite...

CHEERS...

SH.

[Raggi_Thor]

It's always five o clock somewhere in the empire, right?
Good night to you :-)
It's 0100 here and the youngest kid will wake up in 6 hours.

[LP]

You could design a steel trusswork to support the bulb and fair it with glass or ply.

[quilbilly]

Thanks for the ideas. Here are a couple of photos of the boat and keel. The one of the bare keel is before the bulb and shows the steel fin after it was epoxied and faired. The black plastic protects the steel in the daggerboard case but it is still somewhat problematic as any little ding rusts and is hard to access, which is why I am interested in a composite fin, though an aluminum one seems interesting. Todd

[Raggi_Thor]

One nice thing with the aluminium profiles is that you can use it as mold for a tight fitting case in glass and epoxy.