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Old 10-09-2012, 12:36   #31
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Quote:
Originally Posted by sv Shearwater
I've seen two comments about the benefit of davits for keeping your boat out of the water. I thought it was commonplace to lift your dinghy out of the water alongside the boat using a halyard, both for theft prevention and too keep it clean. That's what we do. No need for davits to accomplish this.
Me too. spin pole, halyard and a few pulleys gets it on deck. Davits would be nice but hardly at the top of must have list. You get used to things very quick.
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Old 10-09-2012, 14:11   #32
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I have davits and while they are nice to do a quick lift for the dink for day sailing while staying in a location for awhile, davits for passage making are a no no.

My main purpose for building davits on my boat was to Crete space for solar and instruments. I have 170of my solar watts on the davits.

I have a furuno hydraulic that I love but will be adding a vane this year. You can separate the vane from the gearage by using a high quality non friction Teflon coated and sealed push pull cable if you are using trim tab rudder steerage as I do since my rudder is stern hung, which as a double ender I am assuming your is also.

My vane will be hanging of the aft end of my Dalits away from the solar but less than 4 meters via cable from the trim tab, the minimal friction should be easy to overcome with the vane.

Nice to have a non electronic solution to any critical system...but that is a whole other debate for another thread...
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Old 10-09-2012, 14:39   #33
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Re: Windvane vs. Hydraulic Autopilot

Connie and I never had davits on our Colvin, We always lifted our dink aboard or at least out of the water everyday we used it ! its easy to do with the things most all sail boats have aboard anyway !! a dink lashed on deck with proper fitting deck chocks is far and away better then davits for storage aboard at sea !!! Connies only a 100 lbs soaking wet and she can and did lift our HARD dink aboard our boat for years !!Our new to us boat has davits and a hard dink, but no Wind Vane, so no problem! If it were I, I would go with the Vane and haul the dink aboard, Im sure with a little thought and preperation you can do this with little or no extra work !! Just sayin for the avantages of a wind vane at sea get one and learn to lift the dink aboard !!!
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Old 10-09-2012, 14:41   #34
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Re: Windvane vs. Hydraulic Autopilot

Quote:
Originally Posted by foolishsailor View Post
I have a furuno hydraulic that I love but will be adding a vane this year. You can separate the vane from the gearage by using a high quality non friction Teflon coated and sealed push pull cable if you are using trim tab rudder steerage as I do since my rudder is stern hung, which as a double ender I am assuming your is also.

My vane will be hanging of the aft end of my Dalits away from the solar but less than 4 meters via cable from the trim tab, the minimal friction should be easy to overcome with the vane.

Nice to have a non electronic solution to any critical system...but that is a whole other debate for another thread...
G'Day FS,

When I built the aux rudder/trim tab vane for my previous boat I used 1/4 inch teflon tubing with a small s/s 7x19 wire inside it to drive the trim tab. This did work, but the wire tended to eat its way through the teflon in a few thousand miles of useage. So, I'm interested in what sort of cable you propose to use in yours. Could you post a link or something for me? I'm not planning to build again, but I still am interested!

Thanks, and cheers

Jim
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Old 10-09-2012, 15:28   #35
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Jim,

I can't speak for your experience without understanding your installation. Getting less than a couple years out of a cable seems a bit short, assuming you are not using it for coastal but are actively cruising. It should easily last a full pacific crossing over two years for example.

Some issues that will increase wear...

1. 1/4 inch seems very thick, was it a purpose built cable or did you self engineer?

Edit: just re read and 7x19 would be the correct cable thickness but see point #2

2. If self engineered any variation between the cable OD and Teflon ID will create wear points at all radius turns. The cable will saw through. This happens anyway but should be much, much more slowly wil a purpose built morse cable...
3. More than 360degrees of cumulative bend in all three dimensions will increase wear. It may sound like a lot but most installations are hard pressed to not exceed this in the whole length of cable
4. I used in last application and plan on using in this application 1/8" cable. Adding 50% to manufacturers guidelines for minimum radius for turns is a good idea, and trying to make the turns as large as possible is always a good idea.
5. Keep length as short as possible and keep travel distance as short as possible. This is a high frequency application and length, travel distance and bend all increase friction and wear.
6. Minimise load.
A. The vane will be very efficient, the trim tabs tend to not be so optimised
B. Make sure bearings are true and the tab moves freely. A good trim tab should move when you blow on it during a haul out...
C. Proper trim tab to rudder size
D. Proper lever arm length to trim tab

For me the biggest problem in wear that I will have in my current boat that I don't have a solution for is the fact that I have a huge rudder and I am unsure how the wear on the cable will be as it flexes slightly to port and starboard with the rudder...
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Old 13-09-2012, 12:40   #36
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Re: Windvane vs. Hydraulic Autopilot

Great discussion all. Thanks.
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Old 13-09-2012, 17:17   #37
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Re: Windvane vs. Hydraulic Autopilot

Quote:
Originally Posted by foolishsailor View Post
Jim,

I can't speak for your experience without understanding your installation. Getting less than a couple years out of a cable seems a bit short, assuming you are not using it for coastal but are actively cruising. It should easily last a full pacific crossing over two years for example.

Some issues that will increase wear...

1. 1/4 inch seems very thick, was it a purpose built cable or did you self engineer?
***
1/4 inch was the outside diameter of the tubing, which had rather thin walls (don't remember exactly, for it was over 25 years ago that I built this vane)
***

Edit: just re read and 7x19 would be the correct cable thickness but see point #2

2. If self engineered any variation between the cable OD and Teflon ID will create wear points at all radius turns. The cable will saw through. This happens anyway but should be much, much more slowly wil a purpose built morse cable...
***
As I said, this was a totally home designed and built system. I used what materials were available to me at the time and within my meager budget.
The ID of the tube was considerably larger than the OD of the wire, which was circa 3/32" IIRC.
***


3. More than 360degrees of cumulative bend in all three dimensions will increase wear. It may sound like a lot but most installations are hard pressed to not exceed this in the whole length of cable
***
total bend was less than 120 degrees
***

4. I used in last application and plan on using in this application 1/8" cable. Adding 50% to manufacturers guidelines for minimum radius for turns is a good idea, and trying to make the turns as large as possible is always a good idea.
***
Again, have you a reference to your source of cables?
***
5. Keep length as short as possible and keep travel distance as short as possible. This is a high frequency application and length, travel distance and bend all increase friction and wear.
6. Minimise load.
A. The vane will be very efficient, the trim tabs tend to not be so optimised
B. Make sure bearings are true and the tab moves freely. A good trim tab should move when you blow on it during a haul out...
C. Proper trim tab to rudder size
D. Proper lever arm length to trim tab
***
All of those factors were reasonably well dealt with. I had just a bit of balance area in the trim tab, and it was quite free running and very sensitive.
***

For me the biggest problem in wear that I will have in my current boat that I don't have a solution for is the fact that I have a huge rudder and I am unsure how the wear on the cable will be as it flexes slightly to port and starboard with the rudder...
G'Day FS,

See above comments...

As to your last consideration, the loads imposed by the trim tab should be pretty small so that the small deflections of the cable from rudder motion should in turn be within the specs of any "flexible" cable!

At any rate, I would be interested in a pic when you get it installed. I no longer have access to shop facilities so will not be likely to build another vane, but I'm always interested in how others do theirs.

Cheers,

Jim

PS Apologies for the thread drift.
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