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 Post subject:
PostPosted: Mon Aug 13, 2007 9:05 am 
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Site Rank - Captain

Joined: Wed Aug 02, 2006 4:53 pm
Posts: 58
Wow! That is beautiful. Where's that at?

I plan on trying to hit Elkhorn, LochLemond, Sausalito, and Clear Lake before summer's end. Not sure if I can do it all, but will squeeze in what I can.


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 Post subject:
PostPosted: Mon Aug 13, 2007 1:05 pm 
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Site Rank - Old Salt

Joined: Thu Jul 27, 2006 4:50 pm
Posts: 461
Location: sacramento california
Hey Ya Nu-Too.. :)
Thats the east side o' Lake Tahoe on the Flume trail and then up on the Tahoe Rim Trail at EL. 8800 feet looking south west toward Emerald Bay and also the north shore. Good places to yak and ride bikes
...........Kepnutz.......

North Shore and Incline Village from Flume Trail
Image


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 Post subject: Winglets
PostPosted: Thu Oct 04, 2007 6:09 pm 
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Site Rank - Deck Hand

Joined: Wed Aug 01, 2007 5:59 am
Posts: 3
Hey Roadrunner,

I have been reading your posts about mods. Great ideas. Will be implimenting them on my AI.

Have you experimented with the angle of attack for the winglet yet?

How did you come up with the width dimentions?

I am building a winglet this weekend. Figured I would start out with a wider version and sand as I go.

From your experience, is there anything I should avoid?


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 Post subject:
PostPosted: Thu Oct 04, 2007 11:37 pm 
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Hobie Approved Guru

Joined: Sat Nov 12, 2005 10:46 pm
Posts: 2416
Location: Escondido
Hi fla and welcome to the forum.

I have three sailing rudders, each now using the winglet -- am quite pleased with their performance.

There are some things the winglet will do for you and some things it won't. It increases the authority and sensitivity of the rudder, especially at higher speeds. Thus, when sailing the AI, you can trim the boat with less rudder deflection and this has a slight positive effect on speed. It also seems to help some in tacking. Finally, it provides better broach control and stability during wake rides, where speeds often get up into the 8 to 9 MPH regions. It should also help control broaching in downwind sailing with swells.

IMO, it does not lift the bow, nor is the rudder system designed to support vertical loads. To the extent the bow lifts, it is the hydrodynamic result of the higher speed. This can also be accomplished with a weight shift aft. Any appreciable departure from 0 degrees for the winglet adds additional drag and increases stress on the rudder system and the probability of shearing the rudder pin.

My winglets do not help keep the rudder locked, nor do they hinder it. With the winglet, it's not hard to unlock the rudder. But with some speed, the winglet will keep the rudder from rotating up and out of the water. There are no miracles here.

I obviously try to keep the winglet close to 0 degrees AOA. When not turning, you want minimum drag. A couple of degrees variation doesn't seem to hurt and may be hard to avoid. Better to point down slightly than up slightly, as the water flow past the winglet may actually be rising slightly.

I guessed at the original shape and size based on what I've seen and what little I know about aerodynamics. My objective was to increase rudder authority in the pre-stall realm while minimizing drag (and snags) -- that's what came out.

I accidentally made the second and third winglets 1/8" narrower than the first, but was too lazy to start over. I also made them 1/4" longer (on purpose) to see if the change would "help" lock the rudder down. When all was said and done, they seemed to work about the same. I like your idea of trying something a little wider -- you might get better control in the higher deflection zones.

Some people have made a little deck cushion for the stowed winglet. I haven't done so but have had no problems so far.

Finally, to maximize performance I blunt the leading edge of the rudder to make it more elliptical, sand the rudder, taking out some of the warp on the trailing edge to neutralize any directional tendencies, and finish it off with about 400 wet dry paper. Take care not to round the trailing edge.

If you're familiar with the feel of the (new) standard sailing rudder, I think you'll notice the difference. Good luck with the project! 8)


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 Post subject: Winglet
PostPosted: Fri Oct 05, 2007 4:58 pm 
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Site Rank - Deck Hand

Joined: Wed Aug 01, 2007 5:59 am
Posts: 3
Hey Roadrunner,

Thanks for the advice. I didn't think about any additional stress on the rudder system. I agree with you that it probably would not out last the forces.

Running up to Cocoa Beach tomorrow to throw down some baseboards and then hit the surf. Supposed to be 4 to 6. At least that is what the homeowner told me.

Am taking the project with me so I will be ready for Sunday. Winds supposed to be 10 - 15 so it should be good conditions for a trial run.

Will post a new thread then.

Thanks again


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