Autopilot Suggestions for F28 CK

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Autopilot Suggestions for F28 CK

Postby numbknots » Sun Jan 31, 2010 9:12 pm

It's time to buy a auto pilot and chart plotter that work well with a F28 ck, any thoughts on this? For once I would like to buy a decent product the first time, thanks. Numbknots
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Re: Autopilot Suggestions for F28 CK

Postby phildowney » Sun Feb 07, 2010 6:02 pm

hi, i dont know what the 28 is like but 35s kill wheelpilots , mine has destroyed two raymarine ones , the loads are too big with the big unbalanced rudders and severe weather helm when sails arnt trimmed right also autopilots are unreliable and use lots of power and struggle in a blow, just when you need them
however they steer a course under engine and no wind and can be linked to a plotter,
my solution is to buy a wind vane of some description which is a rugged deprndable piece of kit and then get the tiller ram to go with the control head for my old autohelm 4000+ and link it to the wind vane so it steers through the vane gear, which needs only the lightest toutch to give an input which the powerful pendulum servo gear will magnify to steer the boat
thus the best of all worlds, and you can use the cheap tillerpilots which means that for the cost of a below deck ram system you could buy the whole setup and a few spare tillerpilots for when the first one breaks.
i sail short handed in the english channel and my average passage is over 60 miles and this setup is what i would choose for the sort of sailig i do.
phil d, "kusi" Southampton
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Re: Autopilot Suggestions for F28 CK

Postby Michel » Mon Feb 08, 2010 4:14 am

I agree to Phil's comments and the solutions he gave. I did that on my F33 too. The F28 is lighter though, so might be easier on the helm. It wouldn't hurt to measure the steering loads with an unster (weighing device with a spring) first and then select your solution.
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.
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Re: Autopilot Suggestions for F28 CK

Postby numbknots » Mon Feb 08, 2010 10:38 pm

Well being a lighter boat doesn't seem to make much difference on the weather helm. I was in a regatta this weekend in 25knt wind with 5to 7 foot seas. The weather helm was brutal. I suppose its the style of rudder with the pivot point being the leading edge. I wonder if it would be easier to steer if somehow the leading edge could be extended beyond the pivots. Not much room behind the stern so the brackets holding the rudder would have to be extended further into the rudder. Just some thoughts I had while fightening the wheel saturday. Numbknots
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Re: Autopilot Suggestions for F28 CK

Postby Michel » Tue Feb 09, 2010 4:02 am

Hi Numbknots,

I know of a Freedom 33 centerboard version (open propellor frame) where the owner made a balanced leading edge on the front of the rudder in the prop frame. This leaves less room for the prop though. don't know if it worked. He had made a simple construction with a sheet of stainless steel bent in the middle, folded and bolted through the rudder. Inside the sheet was a block of hardwood to give the bent sheet the desired foil shape.
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.
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Re: Autopilot Suggestions for F28 CK

Postby numbknots » Tue Feb 09, 2010 2:40 pm

Michel,
That is exactly what I was thinking. My rudder is very close to the prop now so that solution will not work. Still scratching my head on this one. Numbknots
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Re: Autopilot Suggestions for F28 CK

Postby Castaway » Tue Feb 09, 2010 6:52 pm

We have the same system as described by Phil. It's a devil to set up, getting the right range of response, etc, and the correct direction of movement, but it is very powerful and seems to be unbreakable. We also have a wheel driving autohelm (Raymarine 4000), which works well when under power or motorsailing, but quickly gives up the ghost when sailing in other than the lightest of airs or smoothest of seas. The flow from the propeller means that the smallest of rudder movements produces good effect, and weather helm is irrelevant, but stop the engine and the linkage disengages in a trice.

We rarely use the Tillerpilot/servo rudder combination because it takes so long to adjust, and, when sailing, the Windpilot self steering works really well except on a dead run. However, if we were starting from scratch, instead of carrying on with the PO's sytems, we would probably go for a TillerPilot and servo-pendulum system, as it is versatile, powerful, and uses the least electricity.

Regards,
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch)
Lerwick Boating Club
Shetland Isles, Scotland
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Re: Autopilot Suggestions for F28 CK

Postby numbknots » Wed Feb 10, 2010 2:29 pm

Why do these boats have such weather helm? Is it the rudder design, the hull or the sail plan?
I was thinking of a narrower rudder that could be verticley retractable, you would have much more mechanical advandage on the pressure. Being able to set it deeper would also make up for area lost. I beleive I saw a sponberg design with 2 rudders that came thru the hull. Of course now he's was giving up that "classic" barn door design for efficency I suppose.
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Re: Autopilot Suggestions for F28 CK

Postby phildowney » Wed Feb 10, 2010 7:49 pm

re weather helm , we lock off the helm with say 3 degrees of helm then trim or ease the mizzen to steer the boat. trim mizzen increases weather helm , ease mizzen , the reverse happens.more wind, more weather helm less wind less weather helm. we have sailed hundreds of miles to windwrd with only occasional adjustments to sheet or ammount of helm set on the wheel. she self steers beautifuly to windward like this with no autopilot.or wind vane.
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Re: Autopilot Suggestions for F28 CK

Postby phildowney » Wed Feb 10, 2010 8:11 pm

idea out of one of the pardeys books is to add enough lead in he trailing edge of the rudder to counter its natural bouyancy as when the boat heels the rudder floats , the exact ammount of lead can be determined by heeling the boat and putting lead into a bag hung on a g clamp hung off the back of the rudder, weighing it and cutting a hole in the blade and installing a plug of lead and epoxy
combine that with cutting a bit off the trailing edge and that balancing bit by the prop and it could add up.

im tempted to cut a inch or so off the back of the rudder as there seems to be a variation in this measurement between models anyway.
also the front of a rudder must be half a circle in profile for optimum lift :drag and the trailing edge needs to be cut square or off to one side but never rounded off as this bizarrely creates more drag and can make the rudder vibrate.idealy it should resemble a naca 00 series foil ie naca0012

as far as im concerned though the main key to weather helm is correct trim and reefing of the mizzen
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