What is a faired keel worth?

Nov 26, 2012
1,653
Hunter 34 Berkeley
I opted not to take the time to fair my iron keel this time around due to life and stuff. I am considering making another go at it in the fall. The question is: what is it worth? Faster? Better pointing? I race my Hunter 34 in PHRF races against similar boats. I have read that a smooth, symmetrical keel provides as much improvement as a new racing jib. My keel is a bit rough. Not the worst but not as smooth as the hull or the rudder. So, compared to other improvements like racing sails or a folding prop where does a faired keel rank?
 

JRacer

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Aug 9, 2011
1,331
Beneteau 310 Cheney KS (Wichita)
Faster, generally. Better pointing, likely.
It's an incremental improvement that when added to the other go-fast incrementals add up to make a difference.

And, faired doesn't mean just smooth. It means smooth and made to the proper symmetrical shape, i.e. not fat on one side and thin on the other or wavy from top to bottom. With the J24, we used class templates to make the size and shape correct (class legal) at specific points measured down from the hull and then faired between the measurement points. Not really a difficult job but time consuming. Good news is that we only had to do the job correctly once.
 
Sep 25, 2008
7,077
Alden 50 Sarasota, Florida
No definitive answer but you can get a good idea of how ( not how much but how) it affects drag by quantifying the percentage of wetted area on the keel compared with hull and rudder. If it’s 10% for example, you have an approximation of how it might affect performance.

The better question is what that effect might be. On drag? On lift?
 
Mar 26, 2011
3,401
Corsair F-24 MK I Deale, MD
Google aerodynamics and you can find many studies. It's not so much about drag as lift-to-drag at higher angles of attack and when it is loaded up. The difference between rough bottom paint and polished paint can be quite material.

Don't forget the trailing edged. It needs to be cut off square (not rounded) and not to wide (1/4" is about right for cruising boats). Again, this might seem minor, but up wind it pay benefits in lift.

This is even more important on the rudder. Lift up wind, and control off the wind in strong conditions. The difference in maximum lift (turning force available) between a rough rudder and tuned rudder can be as much as 40%, but typically 20%. Really, I've seen it. I think that is a big deal even for cruisers. Who couldn't use more control?

It's up to you, but racing, it's a big deal.

https://www.practical-sailor.com/issues/37_67/features/Fairing-the-Keels_12039-1.html
 
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Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
In terms of boat speed and all other things being equal a well faired and templated keel and rudder will help you win races. It is the "all other things being equal" that is the catch.

The time spent fairing and templating the keel might be better spent with crew training, improving tacks, spinnaker sets and douses, and learning tactics. Dick Besse, a well respected sailor and I were talking about fairing the keel on my Tanzer 22, his comment was "lots of guys spend a lot of time fairing their keels and then then they lose an excuse about why they aren't winning." Dick was a skilled and enthusiastic sailor and was presented with the US Sailing W. Van Allen Clark Award in 1996. https://www.ussailing.org/competition/awards-trophies/w-van-alan-clark-jr-trophy/
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
winners do it!
Yes they do, because they are looking for every small advantage to add to the skills they already have. My point is that fairing your keel will have less effect on the boat's performance than a well trained crew and a good understanding of tatics.

A skilled skipper and crew can finish higher in the fleet with a boat that has average preparation than a average skilled skipper and crew in a well prepared boat.
 
May 25, 2012
4,333
john alden caravelle 42 sturgeon bay, wis
all true, but in the real world a skilled skipper and crew will not show up with an average preparation to the vessel they are sailing. it takes all the ingredients to win.
as far as the faired keel goes, very important for quality sailing.
do you drive your car with bald tires? never tune the engine?
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
The bigger question the OP is asking, is what can I do to improve my performance on the race course, where can I get the biggest bang for the buck. For most of us, improving skills will have a bigger bang than fairing a keel. Unless of course the keel looks like the dark side of the moon and cratered. If you are losing races by seconds not minutes, then a fairer keel will help, if you're at the back of the fleet then working on skills will yield better results than a fairer keel.
 
May 25, 2012
4,333
john alden caravelle 42 sturgeon bay, wis
the OP asks about the prep of the vessel for racing. hence my comments. foils are very important. crisp sails too. clean bottom. tuned rig. you will never win with a rough keel as the OP mentioned he had.
plus it's more fun to practice on a boat that sails well :)
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Might be more (or less) but Figure 3 seconds a mile. In a 3 mile race that’s nine seconds. Most people lose that in a bad start, a bad rounding, or a few bad tacks.

So think like this, is this your next step, or is the time and money best first invested elsewhere?
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
Might be more (or less) but Figure 3 seconds a mile. In a 3 mile race that’s nine seconds. Most people lose that in a bad start, a bad rounding, or a few bad tacks.

So think like this, is this your next step, or is the time and money best first invested elsewhere?
That's the trouble with PHRF, everything costs or favors you by 3 seconds a mile. :)

Spin pole too long, 3 sec penalty, fixed blade prop, get 3 sec, oversized Genoa, another 3 sec penalty....
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Indeed, if you’re racing with a fixed prop you’re kind of wasting your time. You might get 6 seconds for it, but it’s costing you 30+
But is it really? Especially in SF Bay where the winds are consistently in the high 20s. My feathering prop gives me a HUGE boost over similar boats at low wind speeds. Like pass em right by. But at higher wind speeds where sails are producing big power, the advantage fades away. I don’t race, don’t have a rating, just lots of observed.
 
Nov 26, 2012
1,653
Hunter 34 Berkeley
Great input. Thanks. The topic comes up because the boat is out of the water and getting a bottom job. I enjoy all the technical stuff and the science that goes into the sport. One interesting thing I came across is the practice of fairing the through hulls. This is to use filler to build up a tear-drop shape fairing around each through hull kind of like wheel pants on a sporty airplane. Anyone out there done this?
 
May 25, 2012
4,333
john alden caravelle 42 sturgeon bay, wis
gunni's observations are spot on. the reason is that the water next to the hull is moving with the hull from the friction of the hull. if the water is moving with the hull it will not be dragging on the prop. remember how nasty the old IOR boats were to drive in a big blow. the water was being dragged along with the hull and was not by the same volume passing by the foil that is trying to steer it.