Below deck AP drives with wide spaced rudder stops

[exMaggieDrum]

I am getting ready for the addition of a below-deck drive for a new autopilot, either electric linear or hydraulic cylinder/pump. I will be installing a new Simrad AP computer system for whatever I choose. This is on a 1981 Goldenwave 42 built by Cheoy Lee and designed by Bob Perry.

One of the big issues is how to fit a linear electric or hydraulic drive to a rudder arm that I will add to the rudder shaft. I currently have chain and cable steering with an Edson pedestal. The cable goes to a heavy-duty steel quadrant that is 90 degrees from edge to edge and about 11" from the rudder shaft center to the end that hits the stops hard-over to hard-over.

The issue is that the rudder stops are 180 degrees from each other, i.e. directly opposite each other lined up with the rudder shaft. Given the 90 degree quadrant that means the rudder turns 45 degrees from dead center to either stop.

I have been told by every drive maker that I have been able to find that that you cannot fit a linear drive or cylinder that will work with a 45 degree range. The max seems to be 37 degrees with 35 actually better. You can't push a drive or cylinder beyond its rated stroke as it will destroy the drive or cylinder. So the stroke has to be greater than the stop to stop range of the rudder. With stops opposite and a right angle quadrant you would need a 20"+ stroke with a 10" tiller arm (shaft center to drive attachment). You can fit a progressively shorter stroke with a shorter tiller arm but you give up effective leverage multipliers for the drive power. E.g. you would need a 6" or shorter tiller arm for a 12" stroke. 12" is a large stroke for most small boat (not large yachts or commercial which would usually have hydraulic drives anyway) drive options, except I have found that Raymarine has an electric linear drive with a 16" stroke with would mean a 7" or less tiller arm.

So if this is true (feel free to point out any errors in the above), then I would need to effectively narrow the hard-over to hard-over angle via new rudder stops. Rudder stops have to be really, really strong. I would like to hear any ideas of potential workable solutions on how to do this from all you who might have dealt with this.

I am discussing this with Edson Marine right now and they say they are confident that they can recommend a workable solution. They have some of the longest and best experiences with steering issues there is and their customer support is phenomenal. But other thoughts would be great to have. I'll post what options they come up with after I go through this. It seems this is not an uncommon situation. Edson has specific experience with the large angle rudder stops so I am looking forward to their comments.

Thanks.

[deblen]

http://www.cruisersforum.com/forums/...nt-140087.html

I don't understand why you are being told that you cannot get +/- 45 deg of rudder movement.
If you make the "tiller arm ram attachment point to center of rudder stock" distance the same length as one half of your ram stroke,the rudder must turn +/- 45deg.
Many lobster boats have +/- 55-60 deg steering,albeit,they are very ruggedly built power steering systems.

Make sure the ram piston cannot contact the rudder stock or anything else in it's travels.

If you set it up for +/- 45,you can leave the rudder stops as is.

As in the past,I still recommend the Ray M81130 or long stroke electric ram -as opposed to electric/hydraulic systems-because of quietness,current draw,less expensive to purchase & maintain. You can buy two Ray linear drive rams for the price of one decent hydraulic system.

Len

[exMaggieDrum]

Originally Posted by deblen

http://www.cruisersforum.com/forums/...nt-140087.html

I don't understand why you are being told that you cannot get +/- 45 deg of rudder movement.
If you make the "tiller arm ram attachment point to center of rudder stock" distance the same length as one half of your ram stroke,the rudder must turn +/- 45deg.
Many lobster boats have +/- 55-60 deg steering,albeit,they are very ruggedly built power steering systems.

Make sure the ram piston cannot contact the rudder stock or anything else in it's travels.

Len, Thanks for your comments. I have found a line of heavy duty cylinders that have much wider articulations, including some that are suitable for 45 degrees. They are very heavy with 2" bores, large volumes, and large rods. They require a larger pump. The pump I have is suitable for them.

If you set it up for +/- 45,you can leave the rudder stops as is.

As in the past,I still recommend the Ray M81130 or long stroke electric ram -as opposed to electric/hydraulic systems-because of quietness,current draw,less expensive to purchase & maintain. You can buy two Ray linear drive rams for the price of one decent hydraulic system.

Thanks for this too. My concern was comments I have heard (not necessarily reliable) as to poor reliability of electric rams. I have since had more than one good recommendation for them so I will start looking in to them. As you note, they are a heck of a lot easier to install. I have extremely good reliability with my previous hydraulic system but that is not a good reason not to consider a very reliable electric one. I'll take a look at the Ray M81130 now.

Len

See my notes imbedded in your quote.

[exMaggieDrum]

This is copied from the Raymarine installation manual for the M81130 series of pumps:

Steering check
When you have mounted th e drive unit, turn the boat’s steering wheel from hardover tohardover and check that:
• Angular movement of the ball end fitting is less than 5 degrees (see Figure 5 ). If youexceed this 5 degree l imit, the drive will catch on the tiller arm/rudder quadrant and theball joint will bind.
• No part of the drive unit fouls the boat’s structure when the push rod moves in and out.
• The total rudder movement is limited to +/- 35 degrees b y the steering system end stopsrather than the linear drive’s end limits (see Figure 7 ).
Figure 7: Total rudder movement


I am going to call Raymarine and ask them about it.

[ramblinrod]

Originally Posted by exMaggieDrum

I am getting ready for the addition of a below-deck drive for a new autopilot, either electric linear or hydraulic cylinder/pump. I will be installing a new Simrad AP computer system for whatever I choose. This is on a 1981 Goldenwave 42 built by Cheoy Lee and designed by Bob Perry.

One of the big issues is how to fit a linear electric or hydraulic drive to a rudder arm that I will add to the rudder shaft. I currently have chain and cable steering with an Edson pedestal. The cable goes to a heavy-duty steel quadrant that is 90 degrees from edge to edge and about 11" from the rudder shaft center to the end that hits the stops hard-over to hard-over.

The issue is that the rudder stops are 180 degrees from each other, i.e. directly opposite each other lined up with the rudder shaft. Given the 90 degree quadrant that means the rudder turns 45 degrees from dead center to either stop.

I have been told by every drive maker that I have been able to find that that you cannot fit a linear drive or cylinder that will work with a 45 degree range. The max seems to be 37 degrees with 35 actually better. You can't push a drive or cylinder beyond its rated stroke as it will destroy the drive or cylinder. So the stroke has to be greater than the stop to stop range of the rudder. With stops opposite and a right angle quadrant you would need a 20"+ stroke with a 10" tiller arm (shaft center to drive attachment). You can fit a progressively shorter stroke with a shorter tiller arm but you give up effective leverage multipliers for the drive power. E.g. you would need a 6" or shorter tiller arm for a 12" stroke. 12" is a large stroke for most small boat (not large yachts or commercial which would usually have hydraulic drives anyway) drive options, except I have found that Raymarine has an electric linear drive with a 16" stroke with would mean a 7" or less tiller arm.

So if this is true (feel free to point out any errors in the above), then I would need to effectively narrow the hard-over to hard-over angle via new rudder stops. Rudder stops have to be really, really strong. I would like to hear any ideas of potential workable solutions on how to do this from all you who might have dealt with this.

I am discussing this with Edson Marine right now and they say they are confident that they can recommend a workable solution. They have some of the longest and best experiences with steering issues there is and their customer support is phenomenal. But other thoughts would be great to have. I'll post what options they come up with after I go through this. It seems this is not an uncommon situation. Edson has specific experience with the large angle rudder stops so I am looking forward to their comments.

Thanks.

Well, the first issue one needs to ask themselves is, "Is a 45 degree rudder angle essential?" The answer in almost all cases should be, "No".

So if to install the unit in compliance with manufacturers recommendations (which may be important for warranty if required), new rudder stops need be installed at 35 degrees, so what?

I had one customer who insisted his rudder angle not be reduced.

(I later found out that the rudder had been modified from original design that eliminate the natural hydrodynamic balancing force, and required much more rudder than normal to overcome "weather helm".)

With the customer not wishing to have the rudder fixed, we shortened the tiller arm pivot point as required to meet his rudder angle expectations, with the knowledge that it could possibly cause some warranty issues if he ever attempted to make a claim.

To date, it has worked fine and he is happy with the installation.

But in most cases, even in close quarters maneuvers, nobody needs more than 35 degrees rudder angle between stops.

Underway, more than 15 degrees is just putting the brakes on needlessly.

(Raymarine Certified Installer.)

[exMaggieDrum]

Rod, I appreciate your feedback. And I agree with you about not needing 45 degrees. I don't know why the boat was built that way. 35 would be plenty and in most case 15-20 would be all you would ever need, certainly for an autopilot.

My manual steering would blow out the cylinder unless I have some sort of hard core stop short of 35 degrees. I haven't found an elegant or robust way to do that other than moving the existing rudder stops or putting spacer blocks on them. Which might work, or not. Moving the stops would not be easy or cheap and would be a lot of labor. One suggestion I have been given is to put "short" cables to both sides of the quadrant preventing it from going past 35. But if a big wave hits the rear end, it seems to me the cable could either break or the attachments could fail and rip something off my hull. And ruin the cylinder.

In any case without built in stops my manual steering would just pull or push the cylinder and blow it out. I'm not sure what you mean by changing the tiller arm. My quadrant is built in and no way to change that that I would do. May be I am just not picturing what you are saying. I would love to find an easy solution. Warranty is not my big concern. I want it to work beyond the warranty period.

[deblen]

Originally Posted by ramblinrod

Well, the first issue one needs to ask themselves is, "Is a 45 degree rudder angle essential?" The answer in almost all cases should be, "No".

So if to install the unit in compliance with manufacturers recommendations (which may be important for warranty if required), new rudder stops need be installed at 35 degrees, so what?

I had one customer who insisted his rudder angle not be reduced.

(I later found out that the rudder had been modified from original design that eliminate the natural hydrodynamic balancing force, and required much more rudder than normal to overcome "weather helm".)

With the customer not wishing to have the rudder fixed, we shortened the tiller arm pivot point as required to meet his rudder angle expectations, with the knowledge that it could possibly cause some warranty issues if he ever attempted to make a claim.

To date, it has worked fine and he is happy with the installation.

But in most cases, even in close quarters maneuvers, nobody needs more than 35 degrees rudder angle between stops.

Underway, more than 15 degrees is just putting the brakes on needlessly.

(Raymarine Certified Installer.)

I agree that it is best practice to limit the ram travel,by the autopilot electronics,to less than the rudder stops.
This means that the ram is never driven to it's full extension/retraction by the pilot.
I also agree that a properly functioning rudder & steering system should not need more than 15 deg or so of rudder travel while under autopilot.

However,the OP stated that his mechanical steering can drive the quadrant +/_ 45deg,which is from stop to stop.
Therefore,when steering manually,the ram must be able to allow +/- 45deg quadrant travel,without the ram being pulled or pushed beyond it's piston travel limits.

Len

[deblen]

Commercial duty steering
Heavy Duty marine Power steering

[ramblinrod]

Originally Posted by exMaggieDrum

Rod, I appreciate your feedback. And I agree with you about not needing 45 degrees. I don't know why the boat was built that way. 35 would be plenty and in most case 15-20 would be all you would ever need, certainly for an autopilot.

My manual steering would blow out the cylinder unless I have some sort of hard core stop short of 35 degrees. I haven't found an elegant or robust way to do that other than moving the existing rudder stops or putting spacer blocks on them. Which might work, or not. Moving the stops would not be easy or cheap and would be a lot of labor. One suggestion I have been given is to put "short" cables to both sides of the quadrant preventing it from going past 35. But if a big wave hits the rear end, it seems to me the cable could either break or the attachments could fail and rip something off my hull. And ruin the cylinder.

In any case without built in stops my manual steering would just pull or push the cylinder and blow it out. I'm not sure what you mean by changing the tiller arm. My quadrant is built in and no way to change that that I would do. May be I am just not picturing what you are saying. I would love to find an easy solution. Warranty is not my big concern. I want it to work beyond the warranty period.

The electric drive, does not have to be attached to the quadrant.

In fact, I prefer when it is not.

Instead, a separate tiller arm, solely for connection to the AP is attached to the rudder stock. The advantage is, if the quadrant ever breaks, the AP can still steer the boat as long as the tiller arm and rudder is still intact.

One can set the distance between the centre of the rudder stock to the centre of the AP pivot point on the tiller arm to whatever they need to get the desired rudder angles.

Just be careful the drive doesn't bind up on anything during full travel lock to lock.

As others have mentioned, during commissioning, the calibrated rudder stops are entered, so one should never reach the mechanical stops.

They are just there for belt and suspenders, to prevent the AP from breaking the boat, or itself, should something happen that it could drive beyond the calibrated stops.

[seandepagnier]

Originally Posted by ramblinrod

But in most cases, even in close quarters maneuvers, nobody needs more than 35 degrees rudder angle between stops.

I am sure glad my boat can make 55 degree rudder angle. This is very useful to make sharp turns in harbors and in this case, you want the brake effect.

Maybe some of the comments here are biased on the assumption that you use engine which makes the rudder work with less angle because of propeller wash, but engines also introduce all sorts of other problems and can fail easily. I sail in and out of any harbor even tacking against dynamic winds and 30 knots with 100 ft or even less space, and I recommend maximum rudder angle.

Some boats can turn the rudder more, and this gives even more manuverability. It is a clear advantage to have more rudder angle for any boat.

The autopilot itself might not need more than 35 degrees, but this fact should not limit the angle under manual control.

My autopilot steers very well even on a 30 ton boat using windshield wiper motor to belt to turn the wheel. This is a very convenient setup, I recommend wiper motors as they are widely available, reliable, and cheap. The course is much straighter than cpt autopilot with less power consumption. There is no limitation of rudder angle.

I tested the windshield wiper motor against raymarine, simrad, tillermaster, and autohelm tiller pilots, and it is the most efficient as well! I was really surprised. I use motor from F-150 pickup truck but other wiper motors work; it cost $6 for motor.

[ramblinrod]

Originally Posted by boat_alexandra

I am sure glad my boat can make 55 degree rudder angle. This is very useful to make sharp turns in harbors and in this case, you want the brake effect.

I know a lot of people think this, but it really isn't the case.

If you limit travel to 35 degrees, you won't be so likely to stall the rudder.

A rudder doesn't really steer at 55 degrees, it's just a drag in the water.

Place some temporary stops at 35 degree rudder angle and try it for 3 months.

I bet you will be very surprised that your vessel actually maneuvers better.

Counter-intuitive I know, but just try it before you deny it.

With a 35 degree rudder angle, one can back and fill to turn any boat (even full keel) in it's own length plus half again, 360 degrees all day (no wind).

[seandepagnier]

Originally Posted by ramblinrod

With a 35 degree rudder angle, one can back and fill to turn any boat (even full keel) in it's own length plus half again, 360 degrees all day (no wind).

Not sure how to "back and fill" with "(no wind)" on a boat that has no engine.

I can turn in my own length plus half again, but I need the rudder at 55 degrees and a sculling oar making turning strokes.

You seem to be relying on an engine. It's better to be able to manage without it.

So maybe motoring, 35 degree is all you need. Maybe more rudder would stall because of prop wash. Maybe spade rudder stalls, but a rudder on a full keel definately works a lot better at 55 degrees and speeds below 2 knots.

I am 100% certain that more rudder is useful maneuvering in tight areas under sail. The boat slows down and turns faster.

[ramblinrod]

Originally Posted by boat_alexandra

Not sure how to "back and fill" with "(no wind)" on a boat that has no engine.

I can turn in my own length plus half again, but I need the rudder at 55 degrees and a sculling oar making turning strokes.

You seem to be relying on an engine. It's better to be able to manage without it.

So maybe motoring, 35 degree is all you need. Maybe more rudder would stall because of prop wash. Maybe spade rudder stalls, but a rudder on a full keel definately works a lot better at 55 degrees and speeds below 2 knots.

I am 100% certain that more rudder is useful maneuvering in tight areas under sail. The boat slows down and turns faster.

Excessive rudder angle is not

necessary

to accomplish this.

Whether one finds excessive rudder angle "useful", is likely a matter of personal preference.