Kickup rudder critique

wet feet and rob:

The hinging of the kick-up transom on the tri isn't clear from pics on his website. Based on other photos of the boat in build and being modified over time, the designer looks to be a very competent fabricator.

The design has virtue of a naturally wide hinge base at deck level. Any deck curvature at the joint would certainly complicate the hinge design - pivot axis needs to be positioned such that the hinged portion clears any fixed portion of the boat. With composites and SS pins, you can certainly make that work and distribute the loads into the main hull.

Look closely at the pic -there is a rebate molded into the perimeter of the kick-up portion to key it to the flange formed by the hull skin extending beyond the fixed transom/bulkhead. You could also solve the problem by just having a pocket with a corresponding boss between fixed and pivoting bulkheads to insure alignment and resistance to shear when the kick-up transom is hauled down.

I do like the IMOCA twin rudders. It'd be a trick to adapt that structure to a narrow transom and keep a spot wide enough to use as a swim step. In the end the two approaches converge: High pivot axis with widely spaced hinges + key or boss for lateral load resistance when rudder is down.

 

Thanks!

Always nice when a design/plan comes to fruition and works as planned.

I take that boat up all our rivers until they turn into rocky streams, so having full motor trim-ability with a push of a button on a wired remote that can be used anywhere on the boat ensures my plastic props will remain intact!

Thanks. Yes I’m familiar with the wireless controllers. Have used them on other projects. In this case having the actuators wired with the buttons located on the handheld remote that also has the throttle controls means I can control thrust, steering, and trim all from the small wired remote. Being able to walk to the bow with the “helm” in hand makes narrow shallow navigation, docking, etc.. a breeze.

I do use one wireless 4-channel wireless controller on the boat for the solar bimini top which has independent actuators for the front and back so you can orient for sun, wind, rain and lower for trailering.

https://youtube.com/clip/UgkxJlc_JsOVSl-_HqS3u7i5wGgW8ZSn1_4Y?si=Xv5GGHc0NdzWnoY8

Regarding your 18V bilge pump battery powered system (sounds like a fun project) -leave yourself some voltage headroom when choosing components. I have designed products around using Makita 18V batteries and have discovered a lot of batteries exceed 20V when fully charged. A lot of the inexpensive electronic stuff on Alibaba or Aliexpress isn’t very forgiving if you exceed component specs.

 

Back to kick up rudders, here’s my “emergency” rudder on the solar electric boat in case I lose propulsion from one of the motors.

I cheated and used a spare Hobie Classic casting and blade assembly and fabricated the center mount and double jointed tiller so it can be steered from either lounge seat.

 

No problem when they are in the water. The problems arise when the rudder is kicked up but still in or near the water and waves and/or heavy steering loads are applied on a much longer arm than when they are in normal position. This is arguably more potential load than while sailing. The wide hinge resolves this, but it needs to be very strong, as does the box.

Sol,
Cool boat. Well done.

 

Returning to the topic rather later,I have seen a Class 40 rudder that is braced laterally by dyneema strops as it transitions from raised to deployed -or vice versa.On the same day,I also saw an IMOCA rudder with a fence,which seems a little odd given the presence of a hull surface just above,but I suppose there could be a leakage of air around the hull insert.