Monday 27 October 2008

From rudder to rudd

While gathering courage to start on OB’s mast I wanted to do something about her rudder. I reduced the size of the foil some time ago but, being in a hellfire hurry to get on the sea, didn’t protect it adequately. The smaller rudder has performed well but after much use water penetrated the single coat of epoxy and black spots of rot dotted the trailing edge.

I was about to build a new blade but instead decided to lop the back edge off. I’d been toying with the idea for some time but admit that I based this possibly rash snip to OB’s nether parts solely on intuition. I doubt the logic is sound but it goes as follows. Unlike me, OB is a well-balanced craft; she can sail herself on all points of sail to windward of a beam reach. By sheeting in the mizzen sail she will turn into the wind and by backing the mainsail before she stalls I can make her tack. I can leave the rudder tied off amidships and sail without having to touch the tiller. I can even raise the blade out of the water and still sail in straight lines, albeit with slightly less speed and windward efficiency. Sailing off the wind I need to steer and it is when the breeze is healthy that the helm becomes uncomfortably heavy. In a small, flat-bottomed boat with low freeboard it is as well to reef early and a weighty rudder is one of the boat’s ways of asking for less sail. By reducing the size of the foil I hope to delay reefing every so slightly on downwind runs.

A boat that’s trimmed with weather helm, as OB is, will try to turn towards the breeze when sailing downwind. OB can be given some lee helm, thus enhancing her performance when sailing broad, by striking the mizzen sail—though I would expect it to make more difference than it actually does. When sailing downwind the tiller needs to be held strongly to prevent the bows swinging round into the breeze, the question is, exactly how much foil does she need to stay on course? I have no idea. But I was lucky enough to do a fair amount of downwind sailing over the summer and my feeling is that OB champs at the bit. She could hold on to more sail for a tad longer without putting excessive strain on the masts and sails. I know I’ve had one mast failure but that was due to an unfortunate grouping of knots in the laminate and not to the stresses of the wind. What is more the new knot-less mast will be slightly more robust.

Of course boats also depend on the balance between the centreboard and the rudder for lift and lateral resistance and I don’t want to interfere with OB’s performance on other points of sail. So, will OB be freer, looser and faster off the wind with a smaller rudder? Or will she be unmanageable? Will a snip to the blade sweeten her or make her crank? I can’t wait to find out.

However, to test the new rudder I shall need to sail and to sail I shall need a new mast. And before I build a new mast I still have to find my boatbuilder’s hat.


Anonymous said...

Hello Ben - I hope all is well. How did the job go in the city? Good to see you back on the boat.

I always enjoy reading these pages, but I must confess, once you start talking in detail about finer points of sailing, this is what I read:

"Граждане Азербайджанской Республики и постоянно проживающие в Азербайджанской Республике лица без гражданства, совершившие деяние (действие или бездействие) вне пределов Азербайджанской Республики, подлежат уголовной ответственности по настоящему Кодексу, если это деяние признано преступлением в Азербайджанской Республике и в государстве, на территории которого оно было совершено и если эти лица не были осуждены в иностранном государстве.

12.2. Иностранные граждане и лица без гражданства, совершившие преступление вне пределов Азербайджанской Республики, могут быть привлечены к уголовной ответственности по настоящему Кодексу в случаях, если преступление направлено против граждан Азербайджанской Республики, интересов Азербайджанской Республики, а также в случаях, предусмотренных международным договором Азербайджанской Республики, если они не были осуждены в иностранном государстве.
стязание, морское пиратство."

But it's no less imressive for all that :)

Ben said...

Hi Anon, you know me but I can only guess at who you are. Yes, I’m afraid that sailspeak forms an occasional part of this blog. It has been a while since I delved into technicalities and I realise that a jargon filled discussion may not be as readable as other content. But I am interested in boat design and the all the factors that enhance or impair performance and I think it’s a valid topic. Then again I don’t think there are any terms in this post that haven’t been used several times before on the blog.

It took me a few searches to decipher what I had hoped was an interesting passage—the criminal laws of the Azerbaijan Republic make pretty glum reading. Come on Anon, I expected something that warranted the cloak of a foreign language;)