[DG] [DG11] Linear type 2 short or can I use a long with a 10 inch tiller arm

[simon Pachunter]

Hi ,
I’m upgrading my wheel pilot to the linear system on my 25,000lb sail boat 42 ft long . I’m going to install a Edson tiller arm , The issue I’m having is the length of the tiller arm . From the center of the rudder shaft there is a bulkhead 12inches away , meaning the longest tiller arm I can use is a 10 inch . The second problem I have is a divider between my lazaret and my quadrant . The ideal system because of the length of the ram would be the linear type 2 long . But when I was going through the manual , it states that the tiller arm has to have 14 inches radius . I can’t get that because I run into a bulkhead .

The reason I want to use the long liner is so I can pass through the lazarette locker with a 2 inch [censored] rather than cutting the entire lazarette locker for the size of the linear motor body .
I guess my question is , will a type 2 long work with a 10 inch tiller arm , since my boat is only 25,000 lb anyway ?

Second question :
Is the type 2 short the exact same unit only shorter and only reason it’s rated for 44,000 lbs vs 33,000lb is that it has 4 inch longer tiller arm needed , More leverage over the rudder shaft ?

Last question :
Do I have to worry about the length of the ram being too long since it will only be pushing a 10 inch arm ? And it’s going to be pushing up against the quadrant stops before it gets near its own ram stop ?
Thanks for any advice

[Derek - Raymarine - Moderator]

Hi Simon,

Thank you for your enquiry

The T2 Longstroke will be fine on a 10" couple radius - given the displacement of the boat, although not important in your case, it should be noted that we use the actual boat displacement as a guide, not the design displacement, since the actual displacement can often be as much a 20% greater than the design displacement.

Using the 10" couple radius will in effect make the T2 Longstroke perform as a T2 Shortstroke and so should be fine for your vessel.

With regards to your 2nd question - you are correct, it has the same motor as the T2 Long stroke and so the same thrust, the difference is entirely due to the geometry of a shorter stroke and shorter tiller bar radius.

With regards to the mechanical rudder end stops, it is essential these are strong enough to stop the drive BEFORE it reaches it own limit of travel, this is clearly stated in the installation handbook.



The reason for this is that when the autopilot is not being used, the rudder must not rely on the drive unit limit of travel as a means of stopping the rudder moving hard over, for example when reversing the wheel can sometimes bang hardover and this shock load can cause damage to the drive unit unless the rudder is stopped by the mechanical endstops. The torque from the drive will be much less than the shock load force exerted by the sea in some situations.

Regards

Derek

[billc42]

My dealer installed a Type 2 Long with a 10 inch tiller arm (in 1992) on a Catalina 42, and the boat yard says it weighs 25,000+. Set up works fine - only issue is keeping up with heavy following seas (which any pilot dreads). I also have the Rudder Reference Transducer and one incident where the rudder was slammed hard over the transducer apparently went beyond its design limit and I had to replace it. Otherwise a very rugged and reliable system.

[Derek - Raymarine - Moderator]

Hi Billc42

Thank you for your feedback,

Although you do not mention which autopilot system is being used, ir SPX, EVolution etc . . in general the pilot performance may be improved in following seas by increasing the rudder gain and changing the mode type to performance in the EV pilot or equivalent in the earlier models. May also be a good idea to check the deviation measured by the compass - since large compass deviation can impact autopilot performance.

regards

Derek

[simon Pachunter]

Thanks for the feed , I’ve ordered my 10 inch arm from Edson and will be installing the new system in April .

[Derek - Raymarine - Moderator]

Hi Simon,

Glad to be able to help,
All the best
Derek