Under deck Autopilot drive mounting

[ex-Gladys]

Appreciate some thoughts here.

I want to install an under deck AP on Gladys, mainly because the wheel pilot is pants and secondly to give me some back up steering in the event of the Whitlock Mamba gear failing. The problem is the room (or rather lack of it) in the tiller flat



For context, the pic is looking aft in the aft cabin. there is a biggish berth on each side with locker space underneath which would allow me to cut through (LH side in the pic) to cut through to mount the end of the drive unit, but I'm concerned about dealing with the stated max load of the drive unit

(Garmin type A) of 400 kgf.

Also for context from the width between the fore and aft bulkheads is 73cm, and the "midships" length of the drive unit is 80cm, so that puts the drive unit halfway into the locker. I'm more than happy to give up the locker space (it's pretty unusable anyway) but how the heck do I construct a mount? All this area is pretty shallow, and there's nothing to brace against outboard except the hull. I did think of using the twice as expensive Jefa direct drive, but that would have to finish up somewhere half in the locker as well, is overkill, and the loads are higher (500kgf)

Answers on a postcard please...

 

[RupertW]

A mount on one side will have a big push force which is ok against the hull if you spread the load with a wide base but the pull force will be equally significant. So is there room for a beam across from one side to the other with a wide base at either end, then mount the drive on that?

 

[Fr J Hackett]

I had similar installation problems with a Whitlock Cobra pedestal and linkage I bit the bullet and bought the whitlock / Lewmar(spit) motor that fits under the pedestal and uses the Cobra linkage. I used a Raymarine controller, don't forget the sensor that you will need to fit on the quadrant / rudder shaft extension.
The Cobra linkage is very robust I have never heard of one failing nor think it likely, the weakest point is where it attaches to the rudder shaft and you will have that problem with the linear autopilot.
One thing I have found out with autopilots is that you get what you pay for and there are no shortcut or cheap options.

 

[ex-Gladys]

I had similar installation problems with a Whitlock Cobra pedestal and linkage I bit the bullet and bought the whitlock / Lewmar(spit) motor that fits under the pedestal and uses the Cobra linkage. I used a Raymarine controller, don't forget the sensor that you will need to fit on the quadrant / rudder shaft extension.
The Cobra linkage is very robust I have never heard of one failing nor think it likely, the weakest point is where it attaches to the rudder shaft and you will have that problem with the linear autopilot.
One thing I have found out with autopilots is that you get what you pay for and there are no shortcut or cheap options.

Ooops.... Just realised my steering is Mamba not Cobra...

 

[Fr J Hackett]

Ooops.... Just realised my steering is Mamba not Cobra...

Double oops I just realised I was talking about Mamba and not Cobra In my defence I have had both types

 

[prv]

I fitted a Raymarine drive in a somewhat similar (but even more constricted) space under Ariam's aft cabin bunk. Fortunately in my case there was a conveniently-located stiffening rib / bunk support which I could incorporate; the mount is made of 18mm ply shaped to fit the hull, bonded in place with thickened epoxy and also bolted through the rib.

It would be useful to see a picture of the inside of the starboard locker - after all, that's where the mount needs to be attached.

(One other thought - would there be room for the drive to fit fore-and-aft along the starboard side of the steering flat, using a second tiller at 90° to the existing one? Projecting into the other locker is probably preferable, if only to save the cost of having a second tiller made, but it's a thought.)

Pete

 

[bristoljim]

What is the radius of the arm attachment point for the pilot ?.Is there room for a dedicated arm for the pilot forward of the rudder shaft you then have a bulkhead to grow a bracket off .Pilot will be programable for LH or RH mounting & you will be clear of the two rudder stops.

Jim

 

[ex-Gladys]

I fitted a Raymarine drive in a somewhat similar (but even more constricted) space under Ariam's aft cabin bunk. Fortunately in my case there was a conveniently-located stiffening rib / bunk support which I could incorporate; the mount is made of 18mm ply shaped to fit the hull, bonded in place with thickened epoxy and also bolted through the rib.

It would be useful to see a picture of the inside of the starboard locker - after all, that's where the mount needs to be attached.

I wish. The "bunk support" on the hull side is nothing much more than a bit of 3/4x3/4 stuck to the GRP... And there's no dividing bulkhead or anything under the berth

(One other thought - would there be room for the drive to fit fore-and-aft along the starboard side of the steering flat, using a second tiller at 90° to the existing one? Projecting into the other locker is probably preferable, if only to save the cost of having a second tiller made, but it's a thought.)

Pete

I 'll need to measure that up, but my gut feel is that it would be very difficult to locate to get the precise offset for the tiller arm, but a good thought. The whole thing isn't helped by the hull angling up towards the stern and the structure in there surrounding it being furniture rather than major structure

What is the radius of the arm attachment point for the pilot ?.Is there room for a dedicated arm for the pilot forward of the rudder shaft you then have a bulkhead to grow a bracket off .Pilot will be programable for LH or RH mounting & you will be clear of the two rudder stops.

Jim

The distance required is about 22cm, from my fag packet measurements I have with me it the distance "maybe" 22.5cm.... But I would still have the same issue - which is an 800mm drive to fit into 370mm... Hence the need to go into the locker.

Thanks for all the suggestions though, it really does help to bounce this of other minds... Keep 'em coming!

 

[PaulRainbow]

This would be my first choice, assuming enough fore and aft room.

Remove the Stb steering stop, fit a 2nd tiller arm at 90° to the existing one, then put the Stb steering stop forward of the new tiller arm. Fit the drive unit to the starboard side of the flat.

 

[prv]

Fit the drive unit to the starboard side of the flat.

Yes - possibly with a bit of reinforcement depending on the strength of the existing bulkhead - the GRP fillet bonding it to the hull only seems to exist at the forward end so it might be worth adding a bit more of the same.

The picture of the drive in the OP looks very long though.

Pete

 

[FullCircle]

You can borrow my spare Raymarine electric Ram and mounting bracket/swivel to give you some ideas on mounting. Boat is in Brightlingsea....
I mounted mine in fresh air on Full CIrcle by creating a bolted in bulkhead from 7/8" ply. I see no reason why you would not mount it on an extended spigot above the current tiller arm?
Send PM if you want the parts to play with!

 

[ex-Gladys]

This would be my first choice, assuming enough fore and aft room.

Remove the Stb steering stop, fit a 2nd tiller arm at 90° to the existing one, then put the Stb steering stop forward of the new tiller arm. Fit the drive unit to the starboard side of the flat.

Yes - possibly with a bit of reinforcement depending on the strength of the existing bulkhead - the GRP fillet bonding it to the hull only seems to exist at the forward end so it might be worth adding a bit more of the same.

The picture of the drive in the OP looks very long though.

Pete

The Garmin drive is longer than the tiller flat is wide unfortunately, there also has to be a defined offset of the drive base from the rudder stock, and I'm not sure how that will work out... so for my rudder angle, I need the AP drive base to be only about 22 cm outside the stock... As the tiller flat is 73 cm wide at the stock, bit tapering in, I'm not sure that by the time we get to the 800 mm distance from the stock that either the heights or the widths align, but it's all good stuff! Can't get back on the boat to measure up with these ideas in mind for 3 weeks now, but it's enough to stop me shelling out the hard earned at SIBS this weekend

 

[ex-Gladys]

You can borrow my spare Raymarine electric Ram and mounting bracket/swivel to give you some ideas on mounting. Boat is in Brightlingsea....
I mounted mine in fresh air on Full CIrcle by creating a bolted in bulkhead from 7/8" ply. I see no reason why you would not mount it on an extended spigot above the current tiller arm?
Send PM if you want the parts to play with!

Thanks Jim, I may well take you up on that when I get back from all these weekends away...

 

[Baggywrinkle]

I guess the nightmare scenario is that it drives the rudder hard against one of the end stops, rudder siezure would cause the tiller connection to give.

With this in mind, what about making up a sturdy steel bracket that attaches the Autopilot ram to both end-stops for the rudder, taking care to make the part connecting the end stops together far more robust than the part securing the end of the ram. Pushing the rudder hard against the end stops would then cause all the load to be transferred though the bracket and not the boat superstructure. The bracket to pop-off or break at the far end of the ram, meanaing no fiberglass damage and no reenforced attachment points, the attachment points for the bracket would just be for alignment and support, the bracket would take all the loads. The end-stops look pretty well attached so should be fine as an attachment point for the bracket In normal operation - difficult to tell from a pic though.

 

[FullCircle]

I guess the nightmare scenario is that it drives the rudder hard against one of the end stops, rudder siezure would cause the tiller connection to give.

With this in mind, what about making up a sturdy steel bracket that attaches the Autopilot ram to both end-stops for the rudder, taking care to make the part connecting the end stops together far more robust than the part securing the end of the ram. Pushing the rudder hard against the end stops would then cause all the load to be transferred though the bracket and not the boat superstructure. The bracket to pop-off or break at the far end of the ram, meanaing no fiberglass damage and no reenforced attachment points, the attachment points for the bracket would just be for allignment and support, the bracket would take all the loads..

Transfering the autopilot loads from the end-stops, through the parts where they are glassed into the hull, through the hull and then to another glassed support for the autopilot ram could rip out the end-stops or worse IMO.

The ram drive motion limits can be set, and advisable to use the rudder feedback option

 

[Fr J Hackett]

Still think you would be better of buying the 1/4 hp rotary motor to fit under the pedestal then choice of controller. It's a very simple installation with no drag.

 

[ex-Gladys]

Still think you would be better of buying the 1/4 hp rotary motor to fit under the pedestal then choice of controller. It's a very simple installation with no drag.

Not discounted by any means, but it does need an additional £200 on a rudder sensor, and is already small hundreds more expensive, also my Mamba is a very old Whitlock, and I'm not sure that the gearbox in question has the mounting plate, or the right number of splines... There's not much technical info available to help with the decision either, but I will visit both Lewmar and Aquafax at SBS on Sunday

 

[Fr J Hackett]

All I can tell you is that the pedestal and torque rod on the boat were of 1990 vintage definitely pre Lewmar and the motor fitted both the splines and the mounting holes for the pedestal which is what the motor fixes to. It's a heavy beast so lifting it up to the underside of the pedestal bolts was a challenge but a car jack and some packing helped.

 

[ex-Gladys]

All I can tell you is that the pedestal and torque rod on the boat were of 1990 vintage definitely pre Lewmar and the motor fitted both the splines and the mounting holes for the pedestal which is what the motor fixes to. It's a heavy beast so lifting it up to the underside of the pedestal bolts was a challenge but a car jack and some packing helped.

All noted, and definitely still in the mix...

 

[Fr J Hackett]

Just looked at your other plotter thread, I used a Raymarine controller with associated gubbins initially with a C series plotter latter an E and they both interfaced well can't remember which AIS I used but I think the auto pilot control had a NEMA which I used for it and an ICOM radio.