Re: [electricboats] Pocket Trawler Electrification

Through this thread, I was assuming that there would be separate controls for each of the two pods.

You could almost make the argument that if you had differential thrust available through separate motor controls, you don't necessarily need the rudders.

I have experience with 3 different twin engine boats.  My current boat is a trawler with twin inboard engines.  There are twin rudders - each located behind the prop.  My previous boat had a similar setup.  The one before that was twin I/O's - so no rudders, but steerable engines.  The catch is that the I/O lower unit is located at the very back of the boat.   The other two boats had the props forward of the stern a little bit.  That made a HUGE difference.   While the I/O's were steerable, they were tied together (for steering).   I could use differential thrust - but that worked best when the wheel was centered and the I/O units were straight.  Trying to spin a boat when both of the props are at the back edge of the boat, and close together, is a challenge.   Modern I/O twin engine boats typically have separate steering, and fly-by-wire.  It's EXPENSIVE, but the software allows you to cant the engines in opposite directions to crab the boat sideways.  It's just plain cheating...  LOL!

On my current trawler - it is WONDERFUL to have twin engines!  This makes docking SOOO much easier than with a single engine and rudder!  However, my current marina has a narrow distance between my dock and the dock behind me (the fairway).  To back out of the slip, I use differential thrust only.   To get into the slip, between the competing forces of wind and current - I have found that I am most successful if I maintain a little headway, steer with the rudders, and only use differential thrust once I have crossed the entrance to the slip.   I initially tried pulling into the slip with only differential thrust.  But by the time I stopped the boat, and turned it, either the wind or the current (!! which is MUCH harder to see) would blow me off course.

On a couple of occasions, I have needed to limp back to the dock with only one running engine ("I only need one engine to get home - that's why I have two!").   In those cases I was very lucky to be able to steer into the slip with just the one engine, and no option of differential thrust.   This is the case where I would say you can "almost" make the argument that you don't need a rudder if you have differential thrust.

That having been said - I think I've seen at least one or two boats that had two props and no rudder(s) at all.

Good luck!!!

John

On Friday, January 30, 2026 at 08:15:29 PM CST, Myles Twete via groups.io <matwete=comcast.net@groups.io> wrote:

Wow---this seems risky.

 

You're saying that you are going to keep a single rudder arrangement but use 2 fixed pods.

As I see it, you'll have several situations where turning response will be pretty wanting.

I'd be concerned about rudder response in docking/undocking or generally anytime moving slowly and perhaps other scenarios, again, mostly at slow speeds.

 

I've never seen anyone do this before---when going twin prop, either you go with twin rudder or have the props steerable.  And the rudders ideally want to be configured as balanced as feasible (having some area in front of the axis of rotation so the torque stresses are minimized with prop thrust.  Even more ideally, flat rudders replaced with aerodynamic profiles are growing in popularity---Dan Pence did this a couple years ago with the rudder on his electric launch "Ginger", one of the first 2 or 3 electric boat conversions done in recent decades and appearing on www.evalbum.com .  The rudder efficiency was improved noticeably.

 

I helped build a 40ft steamboat cca 2000 that was twin-15hp steam engine powered.  Behind each prop we had a rudder.  Steering was mostly a breeze and on many trips I manned the engines and direction controls.  The ability to drive one prop FWD while reversing the other prop allowed really tight turning in docking.  This would have been seriously hampered if that boat had a single rudder---I actually can't even imagine it.

 

Anyone else with twin-screw experience want to add?

 

-MylesT

 

 

 

From: electricboats@groups.io <electricboats@groups.io> On Behalf Of maaseidvaag via groups.io
Sent: Friday, January 30, 2026 1:30 PM
To: electricboats@groups.io
Subject: Re: [electricboats] Pocket Trawler Electrification

 

I should add, the rudder as pictured in my last post is as the boat was originally constructed.  It was enlarged by a previous owner and is about 50% larger with area added both on the leading edge and trailing edge.  I may be proven wrong, but I don't believe I'll have any problems with sufficient rudder authority after the prop wash is moved off the centerline and to the pods.   And, as mentioned, I have the cheat-code in the form of a bow thruster, which does seem like overkill on a 27' boat.

 

Lars