Teardrop End Plate On NACA Flat Bottomed Fin Keel ??

I agree that the endplate should extend aft of the keels trailing edge, but one span length?! Are you referring to the span of the keel or?

 

My bad,... the span of the plate, i.e. if it sticks out 50mm from the trailing edge of the keel, then set the plate trailing edge 50mm aft of the trailing edge of the keel.

 

Rounded keel bottom vs shaped flat plate ??

Very interesting. :idea: The rounded-bottom, "extended keel", vs the current flat-bottom keel, would have the least surface area and related drag, but would it also significantly reduce flow from the high pressure to low pressure side of the keel, minimizing vortex generation?

Captain Rich

 

No, the keel foil should almost always have a square cut tip. Rounding the tip planform of the keel reduces the effective span and effictive area (i.e. reduces aspect area) in relation to its draft and rounding over the tip section increases the detremental effects of the tip vortex. The best "rounded" tip is to cut the planform square and develop a tip cap based on the foil section at at the tip with a 2:1 or 3:1 thickness:span ellipse following the foil thickness.

What Hoerner shows is that for the same drag, extending the foil generates more lift because there is more planform area. Conversely, for the same lift, a foil with less planform area and span but an end cap has more drag because the end plate generates wetted drag without generating lift (induced drag assumed to be the same for a given lift). Therefor if draft is unlimmited, extending the foil is better than putting on an end plate.

 

Rough Night...

Hello...

Sun is coming up (all week it rained) and I am sober - think I will go sailing after a coffee with whiskey...

Try these....

http://www.ventureyachts.com/ph40shoalkeel.html - my hero Henry Scheel

http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=2;t=003236 - further discussion

http://www.vacantisw.com/keel design.htm - crap code

http://www.sponbergyachtdesign.com/Repairs.htm - Eric Sponbergs site and mods for same

OK suns up - I am going to get out of here - go for a sail and then a BBQ on the hook off the dog beach - got my spy glasses - yippee - you may want to also look at some newer Precision Yacht keels - can't vouch for them - also IACC experiments...

Also - you might find Copernic Basic useful - still free - local DL search engine that collects from all data bases (basic only 12) rather than what the one you may be currently using has rights to - see http://www.copernic.com/ ...

Attached thumbnail is from Eric Sponbergs site per above...

SH.

 

Soren...

Hello...

Is there some Microcrap add on that will convert my keyboard and add three keys for the (agoos and nanoos) - so I can type to my Great Aunt Binna in Helsingor that you might know of...

I use a standard US 101 keyboard - she speaks English as anyone does - but I cannot find a full Danish alphabet for same (sp)...

Call me stupid - cause I am - but I just now cannot DL a Danish alphabet for a 101 keyboard - yet I see your mods...

WHAT....

SH.

 

There's two things you can do:

1: Have your great aunt buy a Danish 104-keyboard and send it to you. BTW: You'll need to install a Danish language pack from Micro$oft.

2: Use the "umlaut" (that's the German word for it - I don't know the English!). This way you can type "ö" for "ø" and "ä" for "æ". Now you just need the "å", but this is easy: Up until somewhere in the fifties, the correct Danish way to write this was to use "aa".

 

Infinitely long keel the best

:?:

Okay, so an infinitely long keel would (theoretically) be best, since all of the wetted area contributes to "lift", and the amount of tip vortex created would be insignificant?

 

RDKinard; Correct, if draft is not an issue, then sailboat keels would be long and narrow like an aircraft wing (but no sweep) with as much weight as possible conctrated at the tip in a bulb. Much like an Open 60 ( http://www.seglermagazin.de/rr-o60s-index.html ) or a model yacht ( http://www.amya.org/size.html ).

Sean Herron;

Here is the easy way to add a Å or æ. I know this works for at least 3 platforms (dos, windows, SUN) and should work for most others. I will give how to find the UNIcode address easily for a windows platform, but once you know the code address for a character all you need to do is enter the ALT+ code address.

1) Run the program charmap.exe; it should be in the C:\windows directory

2) Select the font to be SYSTEM. This brings up the standand UNIcode font set.

3) Select and highlight the character you want.

4) Now down in the lower right corner of the pop-up is a box that says Keystroke: Alt+XXXX where XXXX is 4 numbers. This is the UNIcode address for the character rendered in decimal (as opposed to hex).

5) Now in your application, to type that character by holding down the ALT key and entering the code address on the number pad.

so ALT+0197 = Å
and ALT+0229 = å
and ALT+0230 = æ
and ALT+0216 = Ø
and ALT+0248 = ø

Now remember, the problem with this is that there are several different code sets, many based upon the original 255 character ASCII set (ALT+ 3 numbers) which were language font specific, whereas UNIcode has been expanded to include many different languages like arabic and kanji. So in UNIcode ALT+0233 = é while I could also enter ALT+130 also gives me é because I'm using the system font.

And how do I know this......my wife's name is Renée.....

 

So what else could this thing on the bottom of the keel be expected to improve?

Well, would it reduce hobby-horsing? A foil located down under the boat could be expected to provide some longitudinal stability. Yes it would be more effective if it was on the rudder. But, could it be made to reduce pitching?

And what about lift? I guess I have been reading too much of the moth foiling thread. Would some minor amount of lift on a keelboat provide some minor improvement in performance? Planing is defined as lift from hydrodynamic form rather than from bouyancy. I would not expect to lift the lead-belly free of the water, but I could dream of reducing the bow wave.

 

No - this "thing" would be located too close to just below the longitudinal center of flotation to have any effect on pitching.

The "thing" is too small to create any useful lift at the speeds you're sailing. And what's worse: The lift when heeled would act in the wrong direction, so you'll point lower.

 

I let this run ...

Hello...

Copernic Pro kind of runs on its own and then gives you a list when you stumble through the door - thanks for those Danish bits - can't find the executable...

See http://www.angelfire.com/fl4/mft/wing.html

http://www.esotec.co.nz/condorkeel/Html/condor_F.html

http://www.sailboat-technology.com/links/online_articles.php - yikes - this should keep you busy...

http://www.mathscoacher.com/articles/35/winglets-geometry.html

Long day - in reviewing this post - I think you need to kill that weather helm before you start thinking about major keel mods - until you can run all points without guessing how much your cocked rudder is contributing to overall drag you will never have a good reference point - with my little O'day 22 the balance just killed me - drove me nuts - but I now have it set up such that I can tack out of my local bay with just a few finger flicks on the tiller which is bound by a simple bungee chord to some coaming cleats - balance is the best and the first thing to tackle - it varies per point of sail yes - I just got my boat to hold against local prevailing westerlies...

Anyway as I said before - and who really cares what I have to say - just do it - you are obviously intrigued enough with the idea and have yet to dismiss it or you would not have created this thread - just make it removable per above link - easy to modify and reposition - keep a log of progress against position - when it is sweet - lay it up...

Also I feel the need to repost 'hardimans' link to the AMYA 'footie' class - http://www.amya.org/size.html - this footie class sits well with me, and they jog my sense of visual humour - I have been just lately doing research into Hugo Vihlen and other mad men - I will say that those footie pictures just sit well with me and my mad mind set ...

And my own 'fat egg' - my Raven 22...

Yup...

SH.



SH

 

Weather Helm for O'Day 37 ..... Yes !!

It's good to compare notes about weather helm.

We can trim the sails to within 2 degrees of neutral helm, then a gust hits. The autohelm swings the rudder 5-10 degrees, slowing boat speed.

It's one reason we cannot use the autohelm in winds gusting over about 20 knots, the autohelm can't see the gust coming.

I thought the skeg rudder was "a feature", in that it is more resistant to impact with "things".

You say there is a way to minimize it? I don't understand your concept, but it sounds intrigueing. Does the bungee provide "reverse weather helm", so a gust only creates 1/2 weather helm?

Captain Rich

 

Bungee and drink holders with suction cups...

Hello...

I didn't say anything about modifying that rudder skeg - don't get crazy...

The bungee chord is just holding the tiller while I am away pouring a drink - or evacuating my bladder due to having drank too much...

SH.

 

Cutter Rig Configuration

I was surfing thru a few keel discussions this morning and took note of your willingness to experiment, and in particular your observation about pointing higher with the 'newer configuration' cutter rig.

Would you have more to say on this subject?

Perhaps in a different thread related to sailing rigs rather than keels? You might chose one by utilizing the 'search' function in these forums for 'cutter rig' discussions. And I might also suggest you have a look at my predominately headsailed rig (cross between a cutter and a ketch) at http://www.boatdesign.net/forums/showthread.php?t=623&highlight=aftmast rig ," One might equate the twin headsail portion of my rig to the old ‘cutter’ arrangements. In fact the old cutter rigs many times demonstrated a superiority to the standard sloop when a reasonable open slot was designed between the two sails (too close a slot was an Achilles heel of the cutter arrangement)"