Bonjour

With the two long and flat bilge keels, the skeg and the small rudder Mingming has a tendancy to go strait ahead. It's nice when you sail offshore.

With such a long low profile surfaces the efficiency of the rudder will anyway be limited.

I added some camber (beheind the mast)  in the (flat) sail by using flexible battens and a double sheeting system. When I sail headwind, the helm if not firm at all but set far to windward (about 40°). It induces heavy turbulences.

To tack, I must take some speed and inertia and then put the helm slowy almost awarship. At the end of the tack, the speed is almost to zero and the boat drifts until the speed increases to allow the keals to grip on the watter.

Some improvements could be made :

- add some stuff (epoxy foam for example) on the inside of the keels to provide some ort of (assymetrical) profile.

- add endplates to the lower part of the keels but they should be sufficiently solid to support the grounding efforts.

- add some stuff(epoxy foam for example)  to the skeg and ruder to provide some sort of profile.

-extend the ruffer downward (balanced towards in front of the lower part of the skeg) to the level of the keel and backward to increase the rudder surface.

- add endplates to the lower part of the rudder.

Eric

Anonymous wrote:

If your boat is unbalanced, is a bigger rudder the best answer? 
surely you should aim for balance first. 
i do recall my flat sail Coromandel was well balanced 

The mast is fairly far aft on the boat.

The rudder is fairly small due to the default location of the engine. I moved the engine aft as I hardly use it -: we sailed about 35 days in 2023 and sed about 5 liters of fuel. Compared to a Westerly 22 rudder it is tiny.

The standard flat sail was somewhat better balanced than the current SJR but not much. To get the sheet to tiller arrangement going also required me to move into the cabin.

Another sail is always on option but I must say that I am fairly pleased with the current setup and how it performs compared to the flat sail.  There are a few options to move the whole sail forward a bit and keep it there while sailing upwind. That might indeed improve balance.

If your boat is unbalanced, is a bigger rudder the best answer? 
surely you should aim for balance first. 
i do recall my flat sail Coromandel was well balanced 

Well I tried the knowledge base with only a few references. The IRA magazine issue 74 page 26 has an article on one rudder mod that adds end plates. Also issue 80 page 8 talks about a new rudder but gives no details about size or shape, just the rudder response before and after.

However, I remember quite some discussion about rudders, both about size and end plates. So I went to the technical forum and used the google search box.

This: looked like it might be helpful:

Endplates

However, it seems to have been split off from another thread and that thread is not referenced and remember much more discussion than that.

try: General rudder endplate specs too

Anyway, maybe try your own searches as well, my ability to form good search phrases tend not to get the best results and I am sure there are more threads that talk about rudder size, modifications and end plates.

Also remember to search rudder balance. Making a bigger rudder, if the addition is all aft of the pivot point, may make the rudder harder to control. I have a book called "Self Steering for Sailing Craft" That I thought I downloaded from the JRA web site, but I can't find where... so maybe from somewhere else. In any case, the author does go into a lot of detail about rudder size and balance (though not end plates) as compared to keel size and rudder placement. Ah, found the link:  self steering for sailing craft

As to the problem of end plates being a problem when drying out, I find that confusing. I would think end plates would be a plus as they allow a shorter rudder to act as if it was larger. So the bottom of the rudder should be able to remain at the same draft as the original. At the same time, if the rudder does contact the ground, the end plate would offer better support in any case (he says from his armchair). I am not familiar with this boat (even though there seem to be a lot of them around) but unless the rudder is transom hung there would only be a bottom end plate as the hull deals with the top end. On a transom hung rudder it is also worthwhile adding an upper end plate at hull draft.

Len

Anonymous wrote:

Goodmorning,

As you may know a Coromandel has a fairly small rudder.  Many people mentioned that increasing ruddersize might be a wise thing to do when looking to increase balance while under sail. So this is one of my winter projects.

But how much bigger is big enough and when does the rudder get too big?

I took out the rudder this week and I am now increasing the rudder size by 12cm on the lower end of the rudderblade and 10cm on the upperside of the rudderblade. And this decision is really no more than a wild guess.

Again: is this enough or maybe too much?

Your input is very much appreciated!

Best regards,

Antoine

That's interesting, Antoine. Why do you find Siskin needs a bigger rudder? My Emmelène is the other split junk Coromandel, (33% balance), and I find she steers easily, except that her head tends to pay off to leeward as she comes out of a tack, unless I check her.

If I wanted to improve the rudder, I'd fit a horizontal end plate, which should be less vulnerable to damage.