Deep keel vs centerboard

[RichH]

"Stalls usually kill because one wing stalls before the other and the plane loses lift because the airflow starts being mostly sideways over the wings as the nose drops and the aircraft goes inverted."
.... same thing happens on the big Scows, etc. when they 'trip' over their bilgeboards .... and yes they instantly can and do become 'inverted'. They are not known as 'submarines' for no idle reason. :-D

 

[COOL]

. It was different than any other keel on the market at that time.

The 32' boat was the very first small boat allowed in the Transpac and for the first 1800 miles she was boat for boat #!. The U.S Coast Guard clocked her at 16 knots going down Moloki Channel.

Teachers Pet may have sported some interesting inovations
for her time period, and certainly proved to be a capable cruising boat,
but she did not exactly set the racing scene on its ear.
TPIII managed a respectable 9th in class and 22nd overall in
the '73 Trans Pac, but finishd more than a day behind the first boat
in her class, Chutzpah the overall winner.

 

[Armychefmike]

everyone is talking about speed and efficiency as far as draft but I feel forgetting a couple of small but important considerations. When I purchased my boat, my intent was to sail around the world, not race. I wanted a full keel or close in the event that I ran her aground somewhere. Tracking straight for hundreds of miles at a time was important to me.

I think we've gotten away from full keel boats for a couple of reasons. first we built boats like this because they were initially built out of wood. When we changed over to fiberglass and could make any shape we wanted, well, there was no need to stay traditional over a design that may be faster. With faster comes compromises like tracking. If you have a boat with a fin keel it'll turn on a dime. Great for a racer, but not necessarily as practical for a cruiser. If you have a wing on the keel and you run aground, it digs in like a bruce anchor. I see other problems with a fin in the event of a hard grounding, there is a tremendous shear load in the front of the keel and a compression load in the trailing edge that transfer to the hull. On some boats with fin keels, I've seen in the yard had cracks along the leading edge of the keel where it attaches to the hull because the owner did run her aground hard sometime during the season.

The rudder was also a point of concern for me. if the rudder is longer than the keel then its the first thing to run aground and not really as structurally sturdy as the keel.

My thoughts were that I wanted a boat with a long keel for tracking, and to protect my rudder. I would compromise and get a boat with a separate keel and rudder as long as the rudder was protected by a skeg. My boat is definitely NOT a racer. She has a lot of sail out front on a long bowsprit and weighs 11 tons (for a 31 foot boat) but I've been out in gales with 20 foot seas and I've always felt safe. seakindly motion should also be a consideration in boat selection.

So since I'm not racing, I'm sacrificing a few degrees of pointing angle for simplicity, better tracking, and peace of mind in the event that I do run aground. I only draw 4 1/2 feet but I'm still fairly diligent about running aground and keep an eye on my chart and where I am. We're also not saving any money on bottom paint.

Cheers!

 

[NYSail]

First boat was a Cal 34 with a fin keel. Bought a Pearson 36-2 with centerboard. Was very leary going in, but now find the board fabulous. I changed all sheeves so that it works flawlessly ....wife can easily raise board. It is a great advantage when gunk holing or just pulling into shallow harbors.... 4'2" with board up... 8' down.

With the board my setup stays quiet.... no knocking. Boat performs well but am sure I loose a bit due to the turbulence of opening.

Had to do it again, I will go for a centerboard.

Greg
P36-2 #101

 

[Cayennita]

I raced a centerboard Seidelman 30 for any years in the Marblehead area. Anyone from that era can attest to how much higher it could go to windward than anyone else. 3'10' with the board up. because it swung and travel forward while coming up, I could adjust it to get the best trim on a reach. It was water ballasted and 5000 lbs of lead shot in the belly. Because of the hull shape I could also go up wind w/o a board.
I also raced a Hunter Legend 35 with it's 4.5' wing keel and I could go upwind better than a J-30. Again very success full in Marblehead, Hyannis, Annapolis and the Caribbean. The Hunter needed to be sailed at a 20-25 degree angle to keep it from side slipping. The bulb/wing configuration "traps" the water and reduces leeway. The point being that you must know your boat sailing characteristics and make the best of it.
Center/dagger boards are very efficient. Look at all the racing machines with canting keels. Upwind all the lift is generated by it's very deep leeward board. A sailplane has a very long wing, short cord design same as these latest racing machines. The ability to go to windward is directly proportional to the draft.

 

[DC Daniel]

Thanks

Fabulous discussion. Many things I NEVER would have considered.
Thanks

 

[Jentine]

"Stalls usually kill because one wing stalls before the other and the plane loses lift because the airflow starts being mostly sideways over the wings as the nose drops and the aircraft goes inverted."
.... same thing happens on the big Scows, etc. when they 'trip' over their bilgeboards .... and yes they instantly can and do become 'inverted'. They are not known as 'submarines' for no idle reason. :-D

RichH,
If you have time for this drivel, you have time to go sailing and prove your misguided theories.

 

[RichH]

Jentine -
Ive noticed that your 'spot location' hasnt moved in almost a month. Is it that you've accumulated too much bottom growth being MOORED in Boot Key too long???? Youve obviously been spending to much time under the "Marathon Tree of Life" too long. Besides its WARMER in the NE than it is in FL .......... nyaaaaaaaa. Good year to stay home and go SKIING.
;-D

 

[Gazuum]

Another aspect for a cruising boat. If a boat turns fast and easy, it'll probably broach just as easy. Another reason for a full keel or preferably, a cutaway with skeg and a pointy stern.

 

[tomgrigsby]

Deep keel vs centerboard, given same boat make\model.
Which is faster\better in light air? IE: cb easier to heel to get initial flow? Has less drag with board up?Is any sailing to windward performance difference significantly noticeable or just on paper? Why would a person go with a cb option, other than the foot or so less of grounding risk? Anyone who has sailed a centerboard, ballasted boat (I never have), any additional comments. Thank you

- Deep keel will point higher even in light air
Is stability difference that great? cb easier to capsize? - Deep keel always has better stability.
- Deep keel has very noticable difference. In fact a competitor of mine has a 5' keel vs my 4' and he points much better. Much faster. Very frustrating.
- A foot of draft is a big deal. My friend touches down far more often that I do in our channel. Depth in your home waters is a big consideration for keel depth and/or centerboard boat.
- Centerboard boats sail better with the board down. If you have one, raise it only when you need to.

 

[COOL]

Another aspect for a cruising boat. If a boat turns fast and easy, it'll probably broach just as easy. Another reason for a full keel or preferably, a cutaway with skeg and a pointy stern.

The reality is that the type of boat you describe above would be very
difficult to steer in big seas off the off the wind. Modern fin keel boats.
with broad aft sections steer like they are on raills, even when surfing
at speeds of over twice their hull speed.