Thread: Rudder End-plates on Bolger Micro

Take them off.
I tried it years ago on our 42 ft cat. What I found was it wore out our bearings in the rudder gudeons very fast and then the rudders began to "knock". Drives you mad when your trying to sleep!!. We also found we had to replace them every 4 months.

When I took them off, I found immediatly that the steering was more responsive and also easier to steer and, our bearings didn't need to be replaced until 2 years later - in normal maintanence.

Never again

Thanks Mark

Yes, well I guess it may depend on what is meant by end-plates. The end-plates as designed are quite narrow so maybe they wouldn't put much pressure on the rudder fittings, but as to whether they will actually do very much in a positive sense, that's still a question.

I put this same question on the Bolger Yahoo Discussion Group and one guy said his work fine on his Micro Navigator and another said that after 10 years he put them on his Micro but he couldn't see any difference.

Anyway, it's done now, so I'll report back after getting the boat back in the water.

GregF

Howdy Pindimar,

They have proved effective on other of Bolger's boats to allow a very shallow rudder to have a reasonable "bite".

However, my experience of the Micro and the Oldshoe is that the rudder behaves quite well. I have not been out to sea in 25 plus knots either.

What are you trying to fix?

I think it is a worthy experiment too, but like Mark says, if they cause problems you can just lop them off.

I would guess that Mark was using his to help prevent the nose of the cat from being pushed under in certain conditions as skiff moths which are similarly narrow used that trick for a number of years before they became completely foil borne. I would expect them to work quite well, particularly on smaller lighter cats. However when winged keels were suddenly the rage in the early 80s boats on the ocean found that they made the boats a lot more hairy going downwind with waves behind - the boats would surf down the faces of waves and when they got to the bottom of the wave they would keep going in a straight line and not rise as they met the back of the wave in front.

On a rudder it is a completely different animal and in this smaller size AND lower speed I suspect it won't be an issue. However a report would be nice after some sailing around.

Best wishes
Michael

As with most things in yacht design, end plates (on any appendage or foil including sails) are accepted trade offs.

End plates, as I'm assuming most understand prevent pressure bleed off, work fairly well across a narrow S/L range. Below the target range, flow isn't sufficient enough to make a noticeable difference, above the target range they're making more turbulence then they're worth and bring other issues to the table as well. Within the effective range, the plates do work well and keep the rudder "engaged" longer.

Unfortunately, the vast majority of boats need to be quite flexible in regard to the S/L ratios they operate in. Except some racers or other specialized machines, the end plates will be operating in less then desirable conditions most of the time, on most boats.

So, why do we use them? Well, like most everything in yacht design, we have to accept trade offs. Some times, when we've elected to employ low aspect rudders or appendages, it would be nice to incorporate a trick or two, maybe some other magical NA wand waving thingie, to get a marginal improvement in these "challenged" appendages, so an end plate gets drawn up or maybe some chine runners, etc. in an effort to squeeze a touch more out of the design brief's limitations.

Well, thanks for the input from the experts Thanks Mik & PAR. What I was trying to 'fix" was that my Micro is not so good at tacking in lighter wind strengths. I thought that maybe if the boat came around a little bit quicker the tacking ability may improve, hence the idea that rudder end-plates may help. I know that Micros are not prone with this problem and my boat has KA sails so I think they would be well cut. I have to admit that I'm not talking about lots of testing of this but the last time the boat was in the water this was a real problem.

Before that, I could not recall a problem actually? But on this last occasion I had a very experienced ocean cruising sailor helming the boat and he found the same problem.

Anyway, since then, whenever I've had the opportunity where I could have been sailing I've been building another boat instead so now I've decided that even though the boat project has dragged on and on, it's about time that I sailed the Micro again, and to heck with how long I'm mucking around with building the "project".

So next time we're up at the house I'll be sailing the Micro - even with the new rudder bracket unpainted! So, I'll report back if it makes any difference. But other Micros I've seen sailing don't seem to have this issue - especially Paloma Blanca which I've seen in some video footage that was taken by Duck Flat when Graeme ?????'s Martha Jane (unpainted) was sailing with it. Wish that was on youtube so all could see it.

I was very impressed by the way that boat handled in that video. John Mann's Micro here in Sydney also seems to have quite good sailing performance.

As I said before, maybe it's just me!

Greg

Actually we did it because back in the early 90's , an article in some magazine at the time mentioned about by adding an end plate, it theoretically lengthen the rudder. ( I'm not going to get into technical jargon here as it's not warrented)

So a mob of us experimented with the concept. It did nothing for the boat's action when at achor as the plate itself was far to small in this regard. So, yes, while parked or should I say beached on an island, I ripped the rudders off, started my generator and cut them off with a jigsaw. Then reglassed and reattached to the boat.

Funny though about the endplates, Hitchhiker cats have been using them for years. So go figure.
regards
Mark

Often odd features have been used for a long time because they have never been carefully compared with the more conventional way of doing things!

Interesting story Mark!

MIK

End plates aren't anything new and have been around for several decades. Henry Scheel was noted for it's use and appendages bare his name for it, but the adaptation is nothing more then end plate theory in practice. STOL equipped aircraft have employed end plates since just before WWII and the winglits appearing on the ends of commercial aircraft wings in recent years, is an indication of their effectiveness. Side by side comparitive study has been preformed by several comminuties and institutions over the years. They do work, but you have to be fairly clever to dimention and place them.

Finally got the Micro in the water with the rudder modified with end-plates. I may just be kidding myself perhaps but I do feel that they have made a difference. In any case the boat seemed to be tacking more reliably than last time it was in the water, and this was even in quite a light breeze??

This was the same weekend that the Bolger Memorial event was being held in Gloucester, Massachusetts, Phil Bolger's place of birth and residence for most of his life. So we did our own little sail past even though there were no other Bolger boats around - apart from our Brick, that is.

It just happened that the weather was perfect and the tides were, too - just right to launch the Micro on the beach on Saturday morning and retrieve it on the Sunday morning.

Just had a week at Port Stephens where we hoped to be able to really test the rudder mods on the Micro. Well, luck would have it that the weather was just atrocious the whole week. We got the boat in the water but never felt like taking it out or even getting the masts up.

Oh well, next time! It sat on its anchor for a couple of days waiting for a break in the weather but it got worse not better, so eventually we took the boat out. Here's a photo from the week at low tide with a kangaroo whizzing by, funny how the weather looks OK here but the reality was quite different:

GregF