I realize I will be way out on a limb here, but it's my belief that you
could go to 8 percent and not have any problem with strength, when you are
talking carbon fiber. It's THAT strong. I think if you can find some
examples of keel failures, they don't fail in the middle, but at the top
where it attaches to the hull.
This is a very humble opinion because I don't have anything at risk here
except ridicule, which I have learned to survive -- you get plenty of it in
any marriage.
Demitri
On 3/19/08 12:59 PM, "Sneddon, Keith" <[EMAIL PROTECTED]> wrote:
> I would use the thinnest section that I could "show good" structurally
> for the loads anticipated (with a reasonable safety factor) for the
> performance I hope for out of this hot-rod. The Lift-to drag ratio at
> the angles of attack you would expect to see is always better for the
> thinner sections.
> In terms of trailing edge, the limiting factor is probably the minimum
> thickness you can expect to "hold" under the environments you sail in. A
> bent or broken sharp trailing edge will likely be slower than a slightly
> blunted one, and a crack that starts at a sharp corner may find its way
> into the meat of your section under the vibration/acoustic environment
> under your rocket ship.
>
> Keith Sneddon
> #4760 "Are We There Yet"
> -----Original Message-----
> From: [email protected]
> [mailto:[EMAIL PROTECTED] On Behalf Of tim ford
> Sent: Wednesday, March 19, 2008 11:01 AM
> To: [email protected]
> Subject: Re: catalina27-talk: Keel Design-OT-OT-OT
>
> Dave Shaddock wrote:
> NACA0012 profile, if he's carrying 150 lbs of bulb underneath a carbon
> or glass skinned fin-a profile with 12% of its chord at max width will
> withstand side loads
>
>
> Well, actually, the NACA 0012 I spec'ed was for the rudder.
>
> At the risk of incurring the wrath of the listee's who are darned sick
> of this thread, I would like to prolong it with
> 2 more issues (where else is one going to find resources like both Dave
> Sh's, Mark, Peter, Keith and Phil and anyone
> else whom I may have inadvertently failed to include, on one internet
> forum that is comparatively non-contentious,
> friendly and not full of abrasive know-it-alls, I ask you?)
>
> - section for the keel...the 0012 I mentioned is for my rudder....so,
> stick with the 0012 section for the keel? (I already have the templates
> but it's a relatively minor job to make new ones) Go with a more robust
> foil 0013? The bulb will end up being approx
> 165-170 (I need a bit more RM because my crew is lighter)...tip to root
> length, keel foil is approx 60 inches. Keel foil
> is 13.5 root chord, 12 inches tip chord. Laminated 1.25 inch sections of
>
> white oak, skinned with e-glass.
>
> - ok, and this is where it gets really murky...trailing edge
> shape/trailing edge width. There was a pretty long thread about this
> on SA (I cant find the darn thread, though) on this topic. J24
> measurer's look at keel trailing edges VERY closely. As I understand it,
> a squared off trailing edge is fast (as oppposed to one that comes to a
> point), but only fast to the extent that the width of the edge
> (measured perpendicularly to the keel chord) is the proper
> dimension...some percentage of the max profile maybe? This is where
> I cant find much info.
>
> Remember the design is a box rule and the keel and rudder design are
> completely at the discretion of the builder/designer...which
> makes it both fun and a bit frightening...the downside is, like the
> first TP52's, the first boats are likely to be slower than the later
> builds as the faster stuff shakes down and become part of the lore of
> the class.
>
> Thanks again for contributing to a project that is not particularly C27
> related.
>
> For anyone who's undies are in a knot over this thread, I can make it a
> sub-list and continue the discussion there-OR-take
> it to boatdesign.com and suffer some abuse there.
>
> tf
>
>
>
