Boat Performance Change With Foil Rudder?

[capt_nemo]

Haven't yet read a post that provides information needed to make an informed decision whether or not to change the rudder on my Com-Pac SunCat to a Foil.

It would be greatly appreciated if someone would clearly specify, describe in detail, or better yet, actually quantify the change in boat performance as a result of a change to a Foil Rudder.

Thank you.

[Bob23]

Nemo:
   Last winter I built a wood foiled rudder blade for my 1985 23/2 using a template graciously supplied by Doug here at the site. Prior to that, I used the original flat aluminum blade that came with the boat.
   I instantly felt a difference mainly in 2 areas. Previously, "Koinoina" had a very strong weather helm, something that the 23's are known for. Granted, I am using original sails which, although in great condition for 26 year old sails, are still mis-shapen and that contributes to the weather helm in my boat. After installing the foiled blade, I'd say that the weather helm is ruduced to about a third of what it was.
   Secondly, I would experience frequent rudder stall as we were coming. The foiled blade all but eliminated that. Now I can tack through almost 90 degrees regularly. Even out with the main only, I was able to come about.
   This is the first rudder I've ever made and couldn't have done it without the help of my fellow Compac-ers here at the site. In hindsight, I made the blade a bit too wide so in adding wetted surface to the rudder, I inadvertantly added to the weather helm issue a little.
   I think "Koinonia" can also point a bit higher, too. Here are a few photos:

[capt_nemo]

Bob23
Thanks much for the info and photos. Very nice job on the wooden foil. I made a 12' wood & epoxy sailboat from plans which included both centerboard and rudder foil shaped.

I'm just trying to justify changing from blade to foil in my mind's eye. Some SunCat Owners have in fact reported a strong (heavy) weatherhelm in moderate winds. I've sailed mine often this past year in various conditions and for whatever reason have not experienced an extraordinary or otherwise noteworthy weatherhelm. In strong winds under full sail it does of course feel stronger. I do ensure that the rudder blade is all the way down (and slightly forward) as far as it will go before snugging down and that the c'board is also all the way down.

Based on your comments I will pay closer attention to my rudder performance during tacks in various wind conditions.

As for pointing, with Cat rig and Gaff Headed Main'sl to boot, by design my boat doesn't point very high.  I'd really like to compare two SunCats going to windward, one with foil and one without.

[Bob23]

Nemo:
  What with the Suncat Regatta just past, I'm sure there are lotsa skippers over at the Suncat section who will provide info. I know the new 23's and others come stock with a foiled rudder...maybe the new Cats do too.
Bob23

[LConrad]

A foil rudder on my 23 was absolutely the best upgrade ever.

[kchunk]

It's hard to "actually quantify" many things on a sailboat. Hull speed is hull speed, and a tack is a tack. Just about any user feedback you get regarding performance will be subjective.

That said, I suppose one of the closest comparisons I can make to actually quantifying the performance differences would be at both maximum hull speed and minimum (or very slow) hull speed. As the boat accelerates, weather helm (which is normal and a good thing on a sailboat) requires more rudder input to continue on a straight course. The faster the boat goes the more you need to pull that tiller to windward. Eventually, and it's not uncommon with my 23, the un-foiled "plate" rudder will be at such a high angle of attack, or high angle relative to the boat's direction of travel, that it creates so much drag that it's actually holding the boat back. Or in the case where the winds are higher, the rudder will actually stall and the boat will round up or partially round up until you ease the tiller and the rudder once again has authority. In this instance, a foiled rudder will be able to "hang on" a little longer before stalling and actually increase the performance envelop of the boat.

On the opposite end of the spectrum, on really light wind, slow days, a foiled rudder can make it through a tack where the plate rudder will either lose authority leaving you in the eye of the wind or worse, tacking you through the wind and not being ably to stop on the other side, leaving you doing a tack/jibe 360. A friend of mine has an old Macgregor 23, a nice salty looking boat. His rudder looks like a mahogany 2 X 12! He likes it because he says it adds to the look of the boat (which it does, I suppose). However, if you don't have 2 or 3 knots hull speed going into a tack, once the boat starts turning, that big dumb rudder can't stop it and it goes all the way around. Of course this example exaggerates the effect of our plate rudders but it's a graphic picture of how the lack of any foil can effect performance.

Now getting back to subjective opinions, I don't think anyone here upgrades to a foiled rudder for the marginal higher performance increase..."high performance" and "Com-Pac" are words not normally used in the same sentence. However, and I think everyone here will agree with me, the foiled rudder just feels like power steering! Do I need it? No. Do I got it? Yep. Did I pay extra for it? Yep. Would I do it again? Sure would.

On a quick side note. The alloy used to make my older IdaSailor rudder is a bit softer than the stock Hutchins rudder and after being in some really nasty conditions I've bent my IdaSailor rudder a couple times. So, if I'm heading out into the ocean or into conditions where things might get rough before I'm back, I'll change the rudder back to the stock rudder, but 95% of the time I leave the foiled rudder on. Joel at Ida sailor gave me the alloy data on the two different rudders and has told me that his rudders have since changed to an alloy that's not so soft.

[HideAway]

I ve delayed building a foil rudder because we have had such improved performance with a loose footed main.  We did not use our genny all summer!  However as the wind picks up you have to flatten the main and when you do that excessive, in my book, weather helm comes back. 

I think the combination of a foiled rudder and the loose main would be ideal.  My concern would be balance at lower wind speeds.   The helm has a very light touch until the wind gets above 15.   As it approaches 20 we reef and that helps a bit but under those conditions sailing gets physical so any method to make it less so becomes important on a longer cruise.   

The other thing we learned about sailing with a loose foot is you have to move the outhaul control line closer to the mast.   I nearly went swimming one rough day trying to adjust the outhaul with the boat heeled over.  Just yesterday I made the conversion - my control line is now just abaft the vang near my reefing system.  It will make sailing less exciting but much safer.   Matt

[Shawn]

"The other thing we learned about sailing with a loose foot is you have to move the outhaul control line closer to the mast. "

Good point. At the factory location it is tough to adjust the outhaul and can't do it with the bimini up or on a run. I'm changing around my outhaul this winter and will move the cleat forward as you did.

I used my old main loose footed last season along with the Ida rudder and didn't notice any balance problems in light air. That would have been with a 110 or 130 up and also an asymmetric.

Shawn

[curtisv]

This is what I wrote around 2002 or so:

A lot of Compac sailors have made very strong positive comments about the IdaMarine foiled rudder. Claims include less tiller effort and better windward performance. There is a noticable improvement in tiller effort. We are able to point better, though the extent to which the rudder contributes is uncertain because in that same season we bought new headsails.

Now that I have quite a few seasons with it, I think the Ida rudder has made a big improvement.  There is less weather helm and seems to be less drag.  The foiled rudder won't stall where the flat blade would at times.

There is still too much weather helm as the wind picks up and I have considered building a longer bowsprit to move the headsail area forward and also to improve angle of attack and windward performance.

Curtis

[Bob23]

   Interesting, Curtis as I've also toyed with a longer bowsprit. Especially after looking at a Flicka last week. Let me know if you persue that route as I'd be curious as to how you'd do it. I wonder if we'd need a custom stainless steel bracket to mimic the shape of the original?
   My foiled blade works great although if I build another one it will be much narrower. Like most projects, it just sorta grew!
Bob23

[curtisv]

Bob,

I wouldn't have time to build the bowsprit myself if I wanted it this season and I missed my window to talk to someone local about that and some other work.  I'm in sunny California right now which puts me a long way from my boat.  Work I have going on at my house is also a distraction.

So many project ideas and so little time.

Curtis