Simple foil design for large boat centerboard ? 1

[daviedoall]

Hi, I am in need of a foil design for a centerboard for a 52' boat. If I had the foil widths for different station in percentages of length or???, then I could scale it to fit my application. Does such a thing exist?

Another way to say it is; If a centerboard was to be 3" in max thickness and 4' across, what would be the percentages of the 3" at say 10 stations across it's width?

Any clues that would fit my question are highly appreciated.

Thanks, David

 

[rb1957]

that would depend on the airfoil section you choose ...

i'd suggest a simple NACA section, NACA 0010 has it's maximum thickness at 10% chord. there are a whole family of these foils; i'd look at the NACA reference library
"

http://naca.larc.nasa.gov/search.jsp".

good luck

 

[rb1957]

search for "NACA-TN-1591" ... seems to have a bunch of profiles and refeernces that'll probably lead you to more.

 

[daviedoall]

Thanks very much! The active link you included led to a pdf file with exactly what I needed. The profile of a 0010-34 looks perfect for me and the x any y measurements are in % of chord as I'd hoped too!

I will laminate this board in plywood and the plys will make it easy to locate all the heigths wirh my power planer. A fun project!

You guys rock, thanks for being such a resource!

David

 

[GregLocock]

May be a bit late, but if this is for a sailing boat and you are interested in efficiency and performance you may not want to use a standard NACA airfoil.

The reason I say this is that in my experience racing yachts do not use foils that have a max thickness at around 30% or so, more like 50%. This may be for structural reasons.

Another consideration is that the keel has to resist the full lateral force from the sail, therefore it needs to be a high L/D device, at its operating condition.

Finally you want it to have good stall characteristics as it stalls.

The above may however be completely irrelevant, many old designs are competitive, and they were designed by eye.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[daviedoall]

Thanks for your ideas, Greg. It's not too late yet. The NACA foil mentioned has it's greatest width at 40% from the leading edge. I was looking to avoid any vibration or wobble with this percentage. My understanding with old Bonneville cars was to keep the max width ahead of 50% to avoid poor handling.

What would exhibit the best stall characteristics in water do you think. Do you have a foil shape in mind? Max speed on this boat is about 10-13 mph

 

[GregLocock]

No, sorry I don't have any feel for this. Basically I'd copy something that works well in a similar boat.

My reason for caution is that I sail a Robert Hick quarter tonner that was one of the top Australian boats when it was launched, and his designs have always used airfoils that look like airfoils, rather than flat plates with rounded leading edges and tapered tails.

Having said that there are a hundred books and websites out there on boat design, I'd have thought someone would have built a couple of diffferent sections and tried them out.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.