Rudder rake

Hi Experts: this is a question about old-school boats. I like the idea of a small (say 30 ft +/- 2 feet ) long-keel boat - following the Folkboat style ("FB"). The current edition of Good Old Boat mag compares the FB and three other boats. Interestingly, two of them are different versions of the Cape Dory 25 ("CD"). The FB has a noticeably more steeply-raked rudder than the three other boats, but enjoys (at least in Europe) a reputation for superb sea-keeping.

Can anyone comment on the basis of real experience whether the CDs or any other comparable boats have better steering capabilities than the FB?

I like the designs of Holman and Pye, and of Buchanan - both Brit designers - and have a Doug Peterson boat with a nearly-vertical transom-hung (and non-balanced) rudder - but am worried that significant rudder rake will create a heavy helm and a lack of control esp at higher speeds / greater angles of heel as the rudder comes out of the water and/or sucks air down its length.

Equally, these rudders are inherently non-balanced - why don't we hear complaints that FBs and such boats are too heavy on the helm?? I have to say, my boat is not, except when over-powered eg with a spin. up in a good breeze - she will sail to windward all day with not a touch on the tiller.

Please could I have advice?

Keith W

 

The folk boat has a reputation that is well deserved. A look at the lines of the vessel shows good balance, a reasonable amount of displacement and this is spread out, but not excessively. These are qualities many look for in deep water boats.

It's truly not fair to compare a much more modern design to the traditional elements of the folk boat. The two hull forms take a very different approach to handling the design requirements. It's like comparing a 1955 Land Rover to a 2005 Hummer. Both are well suited, off road capable, cargo carrying vehicles, but the Hummer has decades of advances in engineering, experience and materials. It's just not a fair trial.

Helm balance is more often then not, an owner issue, rather then a boat problem. It may in fact be a design characteristic, but hasn't been attended by the owner or skipper. I knew a guy who drove a popular trailer yacht, constantly complained about it's heavy helm. I checked it out with him and the boat was fine, he was the worlds worst sailor, over sheeted the boat, stored everything in the cockpit lockers, the rig was sloppy and out of tune. Sure the boat needed a tune up, but he wasn't able to understand the variables involved (including his own actions) and assumed it must be the boat. I always discount comments about a boats helm balance to little more then steering with the hand rather then the fingers.

The rake of the rudder has little to do with the balance of the helm. It is true that some appendage configurations are more responsive than others, but this doesn't mean it may be desirable in the boat you want. A boat that may engage in occasional bouts around the buoys as well as off shore passages will want a quick, responsive boat in the fleet race, but will wish like hell they'd a long keel and deadwood hung rudder when in the trade winds. It's a very rare boat that does both well. A sea boat should be steady on the helm, even self steer. It's sail area should be in keeping with the steady trades it will encounter, not the fluky in shore winds a harbor queen will endure.

In the end it boils down to the desires and needs for YOUR boat, not what others ***** about in theirs. If you want to beat the others to the windward mark, then well divided appendages of high aspect ratio and excellent sectional shape, in combination with a large sail plan and favorable rating is what you want. This boat will beat you to death in deep water, but God it will be fun, while your strength holds up. If you want a passage maker, then a higher D/L, lower SA/D, moderate keel, protected rudder and comfortable accommodations are more important to you and the 'round the buoys yacht needs to be passed by. Most folks want a little of both and the Cape Dory sort of addresses this, with the elements favoring cruising and an occasional bashing with some similar boats. It would be more cruiser then racer. There are choices that are more racer then cruiser, but there are many choices available. There are also pure cruisers, pure racers, better cruisers, better racers, passage makers, and bar hoppers. The hard part is finding one that does what YOU want.

A rudder hung behind a skeg or deadwood assemble shouldn't have balance built into it; a spade style of rudder can. To directly answer you question about why the folk boat doesn't have all the complaints concerning its balance, well it's such a well balanced shape. The underwater areas on this boat, like most of it's era, have balanced lines. It parts the water nicely, which flows easily around and rejoins cleanly astern, without abrupt changes in the direction caused by bumps, bulges or other things that can disturb the flow. This isn't the fastest shape a yacht can have, but is a very "sea kindly" shape, well incorporated by many designs for generations. You could flatten out the run, harden the bilge, cut huge amounts of displacement from her underwater areas and she may be able to get up a plane, doing double didget speeds in a decadent blow. The ride would go to hell, the accommodations would shrink, the helm would need to be manned continuously and you'd need your fillings replaced when going to weather, but she'd be faster. The question is, would she be a better boat for you with these modifications?

 

rudder balance question

I found this tread on a search and thought it best to add to it. What I am trying to find out is why haven't I seen any transom hung rudders which have a balance section on the front of them? I am designing an electric powered launch and typically we use an underbody, hydorfoiled sectioned rectangular rudder with 1/5 balance blade in front of the rudder stock and the boats steer with little tiller force. We are now building a boat with transom hung rudder and I would assume I should do about the same as shown on the attached pdf. Am I wasting my time or about right? What do you experts think? Any insight much appreciated. Thanks, Tom

 

Hi quietboats,
the rudder as you show it has some problems in my opinion. the forward rake towards the bottom is in my experience a mistake unless attached to the keel at the bottom. It will hook any debris, seaweed, ropes etc going and wedge them up in to the hull. If you go vertical, or rake aft to the bottom this will not occur. Also if the rudder top is kept close to the hull the rudder will be more efficient at low angles of incidence to the water flow as rudder angles increase the gap will also because of the forward rake on the rudder towards the foot. If you look at Jay Benfords dory yacht designs you will see what I mean.
In response to the original thread, as others have commented it is the overall combination of hull and rudder design that determines the balance of the boat. With a raked keel attached rudder the main decider is the distance from the boats turning center to the center of effort of the rudder, this is usually much less than a separate spade or skeg mounted rudder set at the aft end of the waterline and therefore requires more area and steering effort on the same hull and keel design. I know of two boats where a forward raked keel hung rudder was replaced by a spade rudder and in both cases steering effort was reduced and boat control improved, especially down wind under spinnaker.