Rudder redesign / upgrade on swan 38
Hi All,
I have been thinking about upgrading the rudder on my swan 38 and thought I’d canvas some opinion among the expertise and experience here.

The proposal is to profile the skeg a little and rebuild the redesigned rudder on the original stock. The new rudder would be deeper but not as wide (far aft) giving a similar wetted area. The design would be sympathetic to the original shape of the boat so as not to look out of place.

The hope is to improve performance generally and particularly on a run and close hauled.

Half of me thinks: these boats are well built and well designed and ‘if it isn’t broken don’t fix it’.

The other half thinks: Things have moved on, why not benefit from the improved performance a reshaped rudder could offer.

Any views / comments would be much appreciated.

Pete

Dear Pete
If you extend the rudder consideration has to be given to the blade bending strength at the recessed lower straps holding the blade to the stock. The blade is much narrower between the straps, pls see this thread http://www.classicswan.org/forum/post_thread.php?thread=1681
If you could give the thickness between the straps, and the proposed shape of the extended blade some load estimates can be made.
Kind regards
Lars

Thanks for the reply Lars, will post details of the shape when I can.


Do you see it as being a potentially worthwhile modification?


Are changes such as this likely to have a negative effect on the future value of the boat?


thanks


Pete

Thanks for the reply Lars, will post details of the shape when I can. Do you see it as being a potentially worthwhile modification? Are changes such as this likely to have a negative effect on the future value of the boat? thanks Pete

Dear Pete,

here is the story how S&S went about modifying the rudder of S&S 47 ‘ARISTEA‘:

http://sparkmanstephens.blogspot.de/2010/08/modifications-to-swan-47-design-2201.html

My wife and me saw ‘ARISTEA‘ in Whangarei in 2008. It was in bristol shape with the new high performance rudder, new toe rail, new Harken winches, a carbon mast, new engine, new teak, new paint and more etc.

3 years later it was for sale in the US. In the end, the asking price dropped so ridiculously low, that it was embarrassing, below the price of a new carbon spar.

Imho, these kinds of modifications are not worth the effort. After the deed is done, you cannot really compare the boat to its sisters anymore. The S&S 38 in its original configuration is a great boat, fast, beautiful and seaworthy. What more can you ask for?

Kind regards, Michael (47/013 VERA)

Pete
I am aware of a Swan 38 with a rudder modified to narrow spade with the same depth as the original keel, and also the keel has been made deeper. This was clearly done to increase performance on the wind, and can be considered to represent the ultimate for that purpose.
It is assumed you do not want to go that far, but the aim is better control downwind. Extending the rudder provides more power, and the difference can be estimated by calculation.
Upwind a deeper rudder contributes by providing more lift with less drag, helping the keel to reduce leeway, provided the rudder is turned to the optimum angle - around 5 degrees. Proper sail shape and sheeting is required for achieving the correct balance with this rudder angle.
For the Swan 38 five degrees of rudder angle corresponds to 45.3 degrees angle on the wheel.
Rudder lift can also be improved by minimizing the slots between rudder blade and skeg, and against the hull. If there are big gaps they should be attended to.
Kind regards
Lars

Hi Pete,

I wondered about this, I had a few issues with the rudder stock on my boat and when we removed it there was sufficient problems which led to making a replacement. I spoke with a reputable designer and had a new rudder built along the lines which you are considering. I did look at the Aristea job, and I broadly agree with Michaels comments, but I do think improvements can be made which should not de value your boat. On Aristea, they removed the bustle altogether, building a carbon spade rudder, which probably improved short turning and better response, but there is so little space between the hull and cockpit floor, that the strengthening would need to be immense, and following Michaels view, I thought that was too much for the integrity of the design and hull.
We simply added a bit of depth and reduced the width, maintaining the same area tho. The best improvements we have noticed is going downwind in seas, where we feel we have more "bite" and a bit more control - we do offshore racing.
Rob
Sarabande 47/029

Rob, Lars & Michael,
The changes made to Aristea were certainly drastic and I guess opens up a wider discussion about what are acceptable modifications to these beautiful yachts. Just like classic cars there is a real danger of spoiling them by trying to modernise them too much. (Although S&S appear to approve of such modifications)

Rob it's interesting to hear the benefit you have experienced from the higher aspect ratio of your new rudder, the design looks very sympathetic to the boat too. This is similar to what I have in mind.

Lars do you have any photos of the swan 38 you mention with the modified rudder?

cheers

Pete

Pete
Have no photos, but it is narrower than Aristea's.
Modification not done by S&S.
Lars