Wing Keels vs. Fin Keels

Stephen Butler · November 27, 2012, 06:19:36 AM

What is the width of the wing from root to tip? Our draft with a fin keel is 67" (I have measured it twice) and am wondering what the effective draft of a wing keeled C34 sailing heeled over at an angle of say 10 to 15 degrees? I would do the calculations, but do not have the actual wing width measurement. Just estimating, with a wing width of 24", gives the difference in draft between a fin keel heeled over and a wing keel heeled over 15 degrees as not significant, as the fin keel would be drawing less, and the wing drawing more....or am I missing something. Anyway, just wondering if someone had used the actual measurements. Also wondering how the draft of the keels vs the rudders differs between the two setups.

Jim Hardesty · November 27, 2012, 07:51:41 AM

I'll say something that's just my observations i.e. never heard this from another expert

. In sloppy choppy seas, and light wind (get that a lot in Lake Erie after a storm). A fin keel tends to pitch and roll a lot more. A wing, or any shallow draft, tends to stay on top of the waves and just bob up and down. Seen this many times cruising with a group. When we motor from port to port just after a storm and usually the shoal draft boats have a much better ride

stevewitt1 · November 27, 2012, 11:23:34 AM

Jim
Interesting observation. I think it would be interesting to calculate the total surface area of both keel configurations. My uneducated guess would be that there is more surface area on the wing than fin which would provide a type of resistance to lateral or pitching motions. Sort of a static stabilizer of sorts. I knew I should have gone into engineering. Maybe not, as I'm sure you know the difference between and engineer and a cowboy.

Steve
visit us at www.ocontoyachtclub.com and www.warbirdsix.com

Clay Greene · December 03, 2012, 03:08:06 PM

The wing keel is 500 pounds heavier so I would expect that a C34 with a wing keel would pitch less than a fin keel boat, everything else being equal.

Clay Greene · December 05, 2012, 12:53:59 PM

Steve, going back to your earlier post, I believe that Catalina acknowledged that the 3 foot 10 inch draft dimension for the Mark I boat was a misprint. To my understanding, all of the wing keel C34s draw 4 feet, three inches.

I hear you about being glad for the wing keel. We're down in Milwaukee and the Lake Michigan water level is at its historical low. It's is really bad over on the Michigan side, where they have a lot of shallow anchorages. Let's hope for lots of snow up in Lake Superior and some ice on the lake to prevent evaporation. Otherwise, it may just be us and the powerboats on the water next year!

Ron Hill · December 05, 2012, 03:09:16 PM

Guys : The 3'10" depth of the original wing, Catalina admitted was a "design goal". They obviously missed that goal !!
This brought about the discussion (by owners) of what makes a boat hull "sink" further in the water?? The natural answer is that the weight of the hull is higher than that "design goal" !! Hence the C34 has a higher displacement than listed!!

As an aside, I have a 1988 wing and when I look at the wing of a friends 1989 wing they are notably different!!

A few thoughts

SailingJerry · December 09, 2012, 10:20:43 AM

Quote from: Stephen Butler on November 27, 2012, 06:19:36 AM
What is the width of the wing from root to tip? Our draft with a fin keel is 67" (I have measured it twice) and am wondering what the effective draft of a wing keeled C34 sailing heeled over at an angle of say 10 to 15 degrees? I would do the calculations, but do not have the actual wing width measurement. Just estimating, with a wing width of 24", gives the difference in draft between a fin keel heeled over and a wing keel heeled over 15 degrees as not significant, as the fin keel would be drawing less, and the wing drawing more....or am I missing something. Anyway, just wondering if someone had used the actual measurements. Also wondering how the draft of the keels vs the rudders differs between the two setups.

Steven, using a little Trigonometry a 15 degree angle of heel will produce a 9" "dip" of the outer lip of the keel if it is 3 feet from midship to the outside of the wing. If the wing is 4 feet from midship to outside of the wing, it will "dip" 12.8". That brings us to a 5' 3" draft on a hard beat.
Does anyone remember SOH CAH TOA from high school?
Jerry

stevewitt1 · December 10, 2012, 05:57:07 PM

QuoteSteven, using a little Trigonometry a 15 degree angle of heel will produce a 9" "dip" of the outer lip of the keel if it is 3 feet from midship to the outside of the wing. If the wing is 4 feet from midship to outside of the wing, it will "dip" 12.8". That brings us to a 5' 3" draft on a hard beat.
Does anyone remember SOH CAH TOA from high school?

First I'll answer the question at the end, NO.
Now, if you are talking the outside of the wing from midship are you meaning the outboard edge of the wing from the centerline? If I'm interpreting you right then I think those dimensions are way too long. Help me out fellow "wingers" but I don't think my wing extends much more than 18-20" from the centerline of the boat. Yes, I could be wrong but it would be the first time since 2000 (just kidding)

As to the issue of "target draft" verses reality. Again, I'm relying on my memory but it seemed to me that when I was doing my shopping and research on the 34 the 1986 brochure specs said 4'8" then the 1987, 1988, 1989 specs called for 3'10" followed by the 1990 forward all 4'3" Given the fact that there was a significant 10" change from 1986 to 1987, 8, 9 I really felt there was a specific change in the casting of the wing or the hull. Then seeing a 5" additional draft going forward I felt it a reasonable assumption (I know, I know) that a second design configuration change was made. I don't want to sound bitter but seeing as how they made 650 or so 34's between 87-89 and published 3 model year brochures I would have thought they might have noticed the 5" miss on the target. I measured my 1989 hull 854 and it is as close to 4'3" as can be.
Steve

Fuzzy · December 10, 2012, 06:25:02 PM

Steve: You are right, the dimensions from the centerline to the outside edge of the "wing" must be around 18"-20" or so.
The boat is at the marina, not here, so I am guessing but it must be in that area.
Larry

Ken Juul · December 11, 2012, 04:53:34 AM

on my 1990 model, measured at the middle of the keel, the wing extends 16" from the vertical portion. At that position the vertical piece is probably 2" thick.

Footloose · December 11, 2012, 06:17:09 AM

I think that we are not correctly thinking about what happens when a boat heels. It does not rotate around the bottom of the keel, but around the center of gravity which is much higher. If one assumes (yeah I know) that the center of gravity is directly above the keel at the waterline, the maximum draw would be the hypotinuse of the triangle formed by the depth of the keel and the width of the wing. By my calculations that is 4' 5.5" which is significantly less than the 5'7" that my fin draws. Sorry, but the battery in my calculator is dead, however the max draw angle can had by finding the inverse tangent of 16 divided by 53.

Jim Hardesty · December 11, 2012, 06:46:24 AM

Your on the right track. Also consider the hull shape (underwater) changes as the boat heels, this changes the floatation ie. center of buoyancy. I guess to get an exact number you would need some real powerful computer modeling. Or you could at the dock tie a halyard to the shore, heel the boat with the halyard, dive and measure. And that doesn't take into consideration lift from the keel, rudder, and sails. The results would be interesting. Way too much effort for me. I'd rather be sailing.
I'd like to know. When I do go aground, knowing if heeling the boat increases or decreases the draft may be important information.
May be the designers at Catalina know the answer.
Jim

Footloose · December 11, 2012, 07:00:22 AM

Jim,

I agree that the center of gravitly moves with heeling due to hull shape. We need a marine designer to explain all of the interactions. My main point is that the draw increases by a small amount (2.5 inches) not the 1 foot that someone had suggested. BTW-using my numbers the max draw would be at 17.4 degrees. Something to keep in mind if you ground a wing keel boat.

stevewitt1 · December 11, 2012, 06:38:13 PM

Ah Ha! Part of my brain has kicked in. Bear in mind(no pun intended) that it kicked in by probably creating more questions than answers.

QuoteI agree that the center of gravitly moves with heeling due to hull shape. We need a marine designer to explain all of the interactions. My main point is that the draw increases by a small amount (2.5 inches) not the 1 foot that someone had suggested.

I believe that in a ballasted boat when the boat heals; the center of gravity and the center of buoyancy become farther apart when drawn on the cross section of the boat. This is the principle that allows for the ballasted keel to gain greater leverage the farther the boat heals. Conversely, on a scow with a center board, the farther the boat heels; the closer the center of gravity and the center of buoyancy become. The point at which these two meet on these boats is the moment at which the boat will capsize!

At least that observation requires no specific mathematical calculations! It can just be depicted graphically.

Steve

I've come to realize that when my ship finally comes in, I'll most likely be at the airport!