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Hurricane Juan has claimed my rudder and I am having dificulty finding anyone with the proper criteria to build me a new one. Does anyone have a demensional drawing I can get to make one??? Also, I have been told that a Mk 3 rudder will fit and improve the performance of the boat. Does anyone know if this is true? If so, does anyone have a drawing for this rudder?
Your question about fitting a Mk III style rudder to a I or II has been asked here before without being satisfactorily answered, but I see no reason for it not to work - there's no skeg or anything else to get in the way and anything would be better than the earlier rudder.
I don't have a drawing, but once my boat comes out in November, I'll be glad to give you dimensions and a photo. Any competent foil maker should be capable of building something from that.
Incidentally, according to a former editor of Canadian Yachting, this rudder came out of Stevens Institute research that was contaminated by a poor understanding of the scale effects. C&C wasn't the only group to get suckered by it. Cal and Ericson also built scimitar-style rudders.
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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DavidWW1, Your reply is much appreciated. I would certainly love to have a picture of your rudder and demensions if possible. I have no problem building my own if I have this info. My E mail Address is as follows: <A href="mailto:rainslie@ttlsupply.ns.ca">rainslie@ttlsupply.ns.ca</A>
Many thanks
David,
I also, would appreciate a drawing.
Do you think that you could send it to put on the "Trapper Improvement Page?
<A href="http://w1.660.telia.com/~u66006007/trapper/">http://w1.660.telia.com/~u66006007/trapper/</A>
Or, if your drawing is only a sketch, I could put it in Autocad format, and jpeg
I am investigating a folding prop. Gori come up with a size of 14" x 9 1/2", and 1.4" tip clearance. I have only 0.5" tip clearance.
I wonder if this is exacerbating the effects of wash on the rudder.
Frank Marsden
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It will only be a sketch, so putting it in Autocad format is a good idea (I'd like to put it on this site as well to avoid too much trans-Atlantic traffic in what may be a largish file).
I have never heard of a lack of tip clearance as a factor affecting the rudder -- only of prop efficiency and noise levels.
For what it's worth, many people on Lake Ontario have turned their backs on Gori props (against that, Bob Wilson has one and likes it). The consensus seems to be that they don't offer anything like the reverse thrust of their later competitors. I have a Flex-o-Fold and it has superb reverse thrust, at the hydrodynamic price of a larger cross-section than my old Martec (and slightly more than Goris for that matter).
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
Offline
David,
I had a look at Flex-o-fold at the Southampton boat show, and was less than impressed with the amount of backlash in the gears on the blades. I had the impression that they were cast, rather than machined. The prices of the two are about the same.
I mention the tip clearance as the boat seems to have a much stronger prop-walk than I have previously experienced. It does not have much vibration.
I have Turbocad V9, which can output in Autocad format and jpeg. The jpeg files are quite small. When imported into MS Word, the file size is acceptable.
Frank
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Okay - here's the story so far on the Mk III rudder...
I went down to my old club to measure rudders and came across a former 27 owner who said that he had fitted a Mk III rudder on his Mk II (I knew there had to be someone out there who had done it).
He did it because in a blow he found the scimitar rudder too hard to handle on the wind. Off the wind, he commented that half the rudder would come out of the water and the other half would ventilate, so you'd find yourself at times thinking that your tiller had broken, there was so little connection to the water. Once you lost grip, it was gone, versus the Mk III rudder, which you could "get back" (ie, restore flow on) by pumping a couple of times. (Ok - that's enough hyperbole for now - the guy's a really good, perhaps even fantastic helmsman, but he does lay it on when he gets going). He also noted that the scimitar is unreasonably heavy.
He said he was really happy with the performance improvement, but also commented that the Mk III shape does not rectify one vulnerability in the old rudder - as the Mk I and Mk II are slightly shorter than the later boat, the Mk III rudder still extends beyond the stern. A caveat but not a deal-breaker.
I have measurements, etc, which I will turn into a legible sketch backed up by photos. If you are agreeable to this, I'd like to add a page to the site that records the outcome of the two rudder replacement projects along with the Autocad file and photos of the finished rudders. This will serve as a resource for anyone else with a Mk I or Mk II who wants to make the same upgrade.
The sketch and photos will turn up here as a revision to this post, later this week.
My Flex-o-Fold was machined and was commendably snug in the fit of the gears, with no lash discernible by hand. Plus the prop walk is reasonable and it's got enough reverse thrust to suck the engine right out through the transom.
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
Last edited by (2003-10-27 10:13:54)
David Weatherston
Towser, Toronto
C&C 27 Mk IV
Offline
Ralph,
Can you, please, give the internal construction details, of the rudder, as I would like to make a MK III one.
Frank Marsden
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Frank, I have the bent shaft and half the rudder casing that we found on the breakwater. If you can give me your E mail address I can take some pictures and send them to you.
As for construction I plan to use 1 1/2" Stainless steel pipe for the shaft. This is 1.9" OD and the top half should be machined to 1.8765". A piece of metal plate 3/16" thick is then welded to the lower end . I plan to use 5/8" thick marine plywood and epoxy to build up my rudder. After the rudder is shaped and contoured it will be wrapped in fibreglass. It may be a little heavy duty but it certainly will be a lot stronger than the origonal. I'll pass on the demensions of the shaft along with the pictures. Shaft length for the origonal rudder is 40 3/4". You may wish to change this if the MK 111 rudder is longer.
Ralph
Last edited by (2003-10-27 19:44:05)
Ralph
Email <A href="mailto:fdmarsden@aol.com">fdmarsden@aol.com</A>
Frank
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David, If I remember to do it, I will take pictures of the whole construction process and if the rudder turns out decent I'll send them to you.
Ralph
Ralph & Frank (and anyone else who is interested):
There are now photos and a sketch of the Mk III rudder on the site at Special Interest >> Mk III rudder. A cross-section follows later this week.
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
Offline
Frank,
Note the postings by Ralph on his rudder and information under Black Arts. In particular note his rework by removing part of the leading edge from his original finished product. I wondered about this until I drafted the deminsions of both on one sheet and compared, it appears he made a wise move and his rudder meets the suggested balance. Ralph came pretty close to the MK III deminsions and reports good handling thru a season of sailing.</SPAN>
As for material, I would stay away from any straight wood and prefer marine ply to minimize expansion issues. Additionally I am investigating pvc foam products such as Divinycell. Since I will make it myself, cost and ease of construction will be deciding issues.</SPAN>
I plan to go the same route as Ralph, except apply the MK III deminsions more precisely with the NACA0012 foil with one exception. I plan to extend the aspect with an elliptical tip. My intentions are based on the wealth of information available on this forum and additional readings on foil design.</SPAN>
Warren Smith
Serendipity
Galveston Bay, Texas
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