S2 7.9 Meter Class Association

http://www.sailinganarchy.com/cgi-bin/o ... read=89157

Someone's getting a new rudder..... read 2 posts down where he states it's a 7.9.

Proof positive that we need to get a weight limit on these buggers

There is no indication that this rudder is light. However, I've contacted Phil (the builder) to inform him that the class is likely to set a min weight very soon. In the mean time, everyone should be aware that there are two class rules which apply -
PART 2: RULES AND SPECIFICATIONS:
2.1. All modifications to the original design., layout and equipment are expressly prohibited, unless specified in these rules.
Nothing is optional in these rules and specifications unless so stated.AND
A.1. PROHIBITED MODIFICATIONS:
A1.A. Hull, Keel, Rudder (See Plan A and B)
A.1.A.1 Reshaping, filling in, drilling out, relocating of the hull, keel, or rudder.

Any rudder which is built significantly light fails both of these. True, the rules do not yet quantify "significantly", but they will soon.

Thanks for the tip-off Tom.

I wasn't out to get anybody with the post - does S2 still offer replacement rudders, at a decent price?

Getting an actual minimum weight limit set on the rudder would definitely erase the abiguity of the rule. Is 10% lighter too light? 15%? Or simply rephrasing to equivalent to stock weight?

We specificy cushions can't be lightened. I'm surprised it's gone this long without rudders being scrutinized.

As someone who just built new rudder, (working on a second one now) I am very interested in what we decide is an appropriate weight. I have heard that a good (dry) rudder blade should weight about 30 lbs. My old one is about 55 lbs and I believe this is a common weight for 'old' rudders from the earlier boats.
The corecell rudder blank that we are talking about here probably weights 3-5 lbs or less depending on what density Corecell foam he used. The final weight will come from the resin and glass used to cover it.
If anyone would like to weight their ruder blade and post the weight (or e-mail me) I would really appreciate it.
Thanks
Frank Foote (smooth79@mnsi.net)

I posted my blade weight on the old forum in Jan 2002 as 57Lbs. I did some work on my blade again last winter and it weighs about the same (I wrote it down but can't find it at the moment). The rudder spent the winter in a dry basement and had no signs of moisture. I recently helped launch a '94 vintage boat and was surprised to see the blade floated up like a cork, while mine (1982 vintage) is nearly neutral. So I would not be surprised to find different weights.

In response to Tom Line's question about getting a replacement rudder from S2 (Tiara): I contacted them and was quoted a price of (sit down now) $5000 over the phone.
They followed up with an e-mail stating 'At this time we are unable to produce the rudder for the 7.9. Our supplier of the core material has discarded the patterns necessary for fabrication. We are currently weighing our options to continue production of these rudders, but its future is uncertian.'
After hearing that I promptly tracked down Mat Dubois and purchased the rudder mold that he built several years ago. I used that to build my own rudder. A lot of work but worth it.

Frank
Yawanna #122

"I have hull # 154 with a rudder weight of 33 lbs
stock. I have an 1/3 interest in Hull #115 and Its rudder weighs 53 lbs. Large difference in weights."

This was a quote from Ron Pool from "Keel and Rudder weight" posted on the old S2 7.9 Forum at:

http://www.boatsit.com/discus/messages/106/106.html

Frank as you know my rudder weight is 50 lbs. from hull #108.

I launched my boat last week, and took the opportunity to weigh the entire rudder assembly before shoving it into the water.
Everything, blade, head, tiller, right down to the new rudder bushings came to 65lbs. Everything is original except that I painted the side plates white a while back. I didn't bother to pull the blade off and weigh it seperately.

Barry E #11 Aeolus
Hey Barry, thanks for posting this info.
Tom Elsen.

Why all the worry about rudder weights? If the replacement rudder weighs less then you get to carry lead to make up the weight.

Tim - look at the weight differential.

We see some at approximately 60 pounds, and one report of 33 pounds. That's 27 pounds of weight from the absolute end of the boat that could be moved to the bilge. That affects both righting moment and for/aft inertia of the boat.

For instance, most anchors + lead + rope probably weigh in close to the same, and I doubt many people race with those in the bow.

The moment arm from having the weight in the bilge won't make much of a difference: maybe 90 ft/lbs of righting moment at best. But it's still something.

Moving the weight from that rudder probably does more than centering all your extra sails in the boat.

I weighed my rudder blade this morning - 37 lbs Hull #100. The blade is original and it has had some repairs done so 30 to 33 certainly is in the ball park of what it was when it was new.

tfennell1@msn.com

My blade weighs 38 pounds. 1990 built boat.

My rudder (which has broken twice over the past 4 years) from hull #211 weighs about 35 lb, as does the rudder I borrowed from #406. I have heard that somewhere around #300, S2 switched builders for the rudder to Harken (?) and these hold up much better. Phil's Foils is building me a red cedar/fiberglass blade, I'm told it will weigh about 30 lb.

Hope nobody minds me popping in and expressing an opinion on rudder measurements.

Since the class is now discussing a minimum weight, as a builder it would also give me greater confidence that my efforts will result in a class legal rudder if the class rules were to specify measurement tolerances for the rudder.

I have in front of me the official drawing - it shows the general shape of the wetted section (it doesn't show the head), and has two cross sections, A and B, with a set of offsets for each to describe the foil section.

What would be great for anyone building foils (and in reading this forum I know that some of you have built your own) would be a bit of text along the lines of:
- leading and trailing edges between sections A and B may have no more than .125" variance from a straight line
- chord lengths at sections A and B may vary by as much as 0.125" from noted dimensions
- offsets at sections A and B may vary by as much as 0.0625" from noted dimensions.

Those are just suggestions, I'm sure you get the point.

You may also wish to describe the rounding of the tip of the foil, and the thickened trailing edge up near the tip. These details are no where to be found on the plan drawing.

Setting a minimum weight will eliminate any need for a rule prohibitting exotic materials (kevlar, carbon fiber) since their use would then be pointless.

Cheers
Phil
www.philsfoils.com