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 Post subject: Learning To Sail Again
PostPosted: Sun Jul 08, 2007 5:13 am 
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Site Rank - Deck Hand

Joined: Wed Jun 27, 2007 5:43 am
Posts: 17
Location: Hammondsport, NY Finger Lakes
A couple of weeks ago we bought a new 2006 Tandem. Have pedaled it for a couple of weeks and love it. Yesterday, for the first time, I tried the sail kit in light flukey winds. Two 200 pound people aboard. I could not sail closer than 110 degrees to the wind. If I went toward the wind, the boat would immediately weathervane, solidly in irons, and the rudder could not be used to avoid this. I am an experienced small boat sailor, having owned 80+ small sailboats, the best of which was a new Hobie 18. I am trying to figure out the combination of fins down, what to do with the rudder, and why it sails so weird. Maybe a larger rudder (we have the old style), and steadier winds. Any and all advice or help appreciated.

Thanks, Bill


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 Post subject:
PostPosted: Sun Jul 08, 2007 7:23 am 
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Site Rank - Old Salt

Joined: Thu Jul 27, 2006 4:50 pm
Posts: 461
Location: sacramento california
Hi Ya OhBee Wan :)

:wink: :wink:


Last edited by kepnutz on Tue Sep 16, 2008 5:27 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sun Jul 08, 2007 9:27 am 
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Site Rank - Deck Hand

Joined: Wed Jun 27, 2007 5:43 am
Posts: 17
Location: Hammondsport, NY Finger Lakes
Kepnutz, thanks for the comeback, as the CBers used to say. They had very colorful language. Your replies are very helpful.

Per my sailing problem, generally what I am trying to resolve is the lack of rudder authority (I think I will make a rudder sock), and trying to figure out the relationship between the center of pressure and center of lateral effort. That is, do I raise or lower which set of fins to get the desired effect. I was hoping to be able to sail towards the wind. The British say "a gentleman does not sail to windward".

Thanks, Bill


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 Post subject: ruddy rudder
PostPosted: Sun Jul 08, 2007 7:42 pm 
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Joined: Thu Jul 27, 2006 4:50 pm
Posts: 461
Location: sacramento california
Bak-At-Chew Ohbee Wan
I


Last edited by kepnutz on Tue Sep 16, 2008 5:28 pm, edited 1 time in total.

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 Post subject:
PostPosted: Mon Jul 09, 2007 6:04 am 
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Site Rank - Deck Hand

Joined: Wed Jun 27, 2007 5:43 am
Posts: 17
Location: Hammondsport, NY Finger Lakes
Kepnutz, thanks for the reply. Do you sail with both sets of fins straight down?

Thanks,

Bill


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 Post subject:
PostPosted: Mon Jul 09, 2007 6:56 am 
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Joined: Thu Jul 27, 2006 4:50 pm
Posts: 461
Location: sacramento california
Hey Oh
[/img]


Last edited by kepnutz on Tue Sep 16, 2008 5:28 pm, edited 1 time in total.

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 Post subject:
PostPosted: Mon Jul 09, 2007 7:46 am 
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Site Rank - Deck Hand

Joined: Wed Jun 27, 2007 5:43 am
Posts: 17
Location: Hammondsport, NY Finger Lakes
Kepnutz - thanks again for your input. It looks like you are doing very well at enjoying life.

Bill


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 Post subject:
PostPosted: Mon Jul 09, 2007 10:06 pm 
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Hobie Approved Guru

Joined: Sat Nov 12, 2005 10:46 pm
Posts: 2388
Location: Escondido
Kep,

Your improvements look really nice. I still have to rig the Oasis -- was going to use a clam cleat, but I like your arrangement better! 8)


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 Post subject:
PostPosted: Tue Jul 10, 2007 7:33 am 
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Joined: Thu Jul 27, 2006 4:50 pm
Posts: 461
Location: sacramento california
Hi Ya Roadie..
:? :twisted: :!:


Last edited by kepnutz on Tue Sep 16, 2008 5:28 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Jul 10, 2007 9:06 pm 
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Joined: Thu Jul 27, 2006 4:50 pm
Posts: 461
Location: sacramento california
:)


Last edited by kepnutz on Tue Sep 16, 2008 5:28 pm, edited 1 time in total.

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 Post subject:
PostPosted: Tue Jul 10, 2007 11:37 pm 
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Joined: Sat Nov 12, 2005 10:46 pm
Posts: 2388
Location: Escondido
Looks great! I hope you'll post a "How To" when done. It should make a huge improvement sailing! 8)


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 Post subject:
PostPosted: Sat Jul 21, 2007 3:45 am 
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Joined: Thu Jul 27, 2006 4:50 pm
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Location: sacramento california
Hi ya Roadie-Oh
:oops: :P :x


Last edited by kepnutz on Tue Sep 16, 2008 5:29 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sat Jul 21, 2007 9:50 pm 
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Hobie Approved Guru

Joined: Sat Nov 12, 2005 10:46 pm
Posts: 2388
Location: Escondido
Hi Kep,

I've also been working on a new winglet for the Oasis. I was already using a modified rudder -- it worked great except it wouldn't hold when we hit the high angles on the wakes.

So I modified a sailing rudder, moving it forward like the new Hobie sailing rudder, except with a more custom fit like yours. Will expect that plus the new winglet will give more bite.

BTW, the winglet is similar to the older one, but extended aft another 1/4" (see pic).
Image

This extension probably won't make any difference on the Oasis, but might with the AI (helping to hold the rudder down, not that it's had a problem so far). I had hoped to have it ready to test tomorrow, but alas, I had to sail and kayak today and didn't have enough time! 8)


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 Post subject:
PostPosted: Sat Jul 21, 2007 11:51 pm 
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Joined: Thu Jul 27, 2006 4:50 pm
Posts: 461
Location: sacramento california
Hi Ya Roadie


Last edited by kepnutz on Tue Sep 16, 2008 5:29 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sun Jul 22, 2007 10:15 pm 
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Hobie Approved Guru

Joined: Sat Nov 12, 2005 10:46 pm
Posts: 2388
Location: Escondido
When rudders are deflected, not all water flows across the blade; some "spills" over the bottom. This reduces the effectiveness of the rudder and creates additional drag, specifically called a tip vortex. A winglet's function is to keep more flow over the rudder, increasing its effectiveness and reducing any tip vortices. In order to so this, the winglet is positioned at or near the bottom of the rudder where it can act sort of act as a fence. Many airplanes have similar devices on their wing tips, though they look different.

Of course, when the boat is going straight (or no lateral forces like a sail), there is no need for a winglet -- it just adds extra drag. In other words, if the rudder is doing the job well, there is no benefit to having the winglet. But if your rudder needs more bite, a winglet can make it more efficient without increasing the rudder size.

For the Oasis, this winglet's job will be to help keep the boat from broaching on high boat wake angles. For the AI, it will be to add low speed rudder authority where weather helm is an issue (not referring to rudder balance), and as insurance against high speed rudder pop-up.

As to size and shape, I am no expert by any means. There are, no doubt more efficient shapes, but there are some practical matters to be considered:

1. You don't want your winglet to extend forward past the rudder lest it might snag seaweed or other debris.

2. You want it as small as practicable to minimize drag but not effectiveness.

3. It should be joined on both sides so strength and alignment can be achieved relatively simply.

4. (AI only) the winglet also seems to help keep the rudder down at high speeds, so the longer back tab should help. This would be a waste on other rudders though where kick-up is not an issue (except that it helps prevent it from splitting while you're building it).

Theoretically, I think it should be wider near the front (where the rudder is widest), tapering aft. I don't have the skill to make it that way, so it looks more boat shaped instead. It seems to work well enough though!

I'll add a picture when done. 8)


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