Day 157, 7/6/24 Autopilot re-adjusting, addind end switches to autopilot drive, molding mounting plates to windlass mount, temporary fuel tank .

Autopilot

During sailing  7/6 with autopilot had two malfunction situations when autopilot drive overrun travel distance of the rudder turn side to side and the steering arm slipped on the rudder shaft. I have no key installed on the shaft, it was done intentionally to prevent any mechanical damage in case if autopilot gets out of control without end switches.

I will cut key way after I will be 100% confident in autopilot. For now slipping is better then attempting to fight.

End switches. 

Originally I thought about industrial grade heavy duty switches, even sourced them, but ended with just magnetic switches used in home security setups.

 There several reasons to use magnetic switches.  

1. They are totally encapsulated and no way to be compromised by weather.
2. No mechanical contact with moving parts, no way something get stuck.
3. They have reliable by design, no mechanical parts. 
   
4. Dirty cheap and easy to source anywhere on the planet.
   

Cons and mitigation.

1. Not designated to be mounted on metal. [ i made mounting plates to install them on steering cross member]
2. Pretty fragile  design [ I installed them out of place where they may be damaged mechanically]
3. As soon as they controlled by magnets, magnets may interfere with compass. [ I have tested  if magnets make any deviation to pedestal compass, no issues at all]
   

Some other concern I have about my installation. 

Sensors mounts mounted on the cross member with one screw. I added super glue on the thread and surface under bracket to prevent them loosing. Maybe just locktite will be enough. 

Open wires without external jacket. I ziptied  them to metal cross member.  very unlikely they get loosed and will be damaged . Form other hand all these wires are sensor wires and no way to make any fire or other thermal event due to current over then restricted by motor controller.

 Bolt on steering art to linear drive is mounted nut up. If nut get loose bolt may drop out from place. will be nice to drill bolt and put pin in or just put locktite on this bolt.

Windlass mount build.

After a lot of thinking I made decision to bolt windlass mount to chain/anchor locker. 

Way of thinking:

Load to windlass should not exceed it Max pull capacity * safety factor (lets say 2). Pull capacity 300 kg so load to mount will be below 600kg. 6 of 5/16 bolts will be absolutely overkill to keep it on place, however chain locker made from 5-6mm fiberglass and I need to distribute load. Bolts will prevent to slide mount in up direction only. Main shifting load will be sustained by locker frame due to it's shape.  But, due chain will come about 4 inch higher than plane of mount it will result in lifting up aft side of the mount plate. I would estimate maximum about 1/2 of main force to try overturn plate. 

Due to 2 bolts on each side load will  not estimate more than 300 kg force shear the bolt. from other hand FG laminate may withstand 1000-2500Mpa. With 5mm thickness and 5/16" bolts section  is 0.00004m2. even at 1000 Mpa it gives strength about 40KN -> about 4 metric tons. So, we should be good.

So, i decided to use existing chain locker a a mold to make mounting plates. Pates will have exact matching surface to locker walls to distribute load equally.

 

I masking taped the area and covered locker surface with PVA mold release, then glassed  2 layers of 1708 to walls and went all way to the top of the mount.

General mounting plates build idea here.

How it looks in life. Only corners are visible :-)

Bottom view during first step layup.

Mount removed from "mold". Now i have perfect matched base to build mounting plates.

Cutout on one side is for black water tank vent. But splitting the mount plate should not be an issue.

TO BE CONTINUED....

Fuel tank

I am looking to rebuild my encapsulated fuel tank. It may take several weeks.  BUT, i want to be able to get out for sailing. I installed 2 gal "spare" tank inside motor compartment . It is "one tome use type one, but I hope it can survive couple docking-undocking motor runs.

should not be too bad as short term solution.