Kick-up rudder design options

[montero]

If bungee/spring will be act like above tiller will be prone to kick-up during sailing.That's switchblade rudder.

 

[laukejas]

If bungee/spring will be act like above tiller will be prone to kick-up during sailing.That's switchblade rudder.

The bungee is holding the blade both in down and up positions. With current design, the blade would have to lift up at least 30° to overcome the neutral point and have the bungee start pulling it up. I don't think it should lift that much during normal sailing, especially if I tension the bungee enough

 

[messabout]

You had it figured out all along. My apologies for doubting the facility of that clever design.

 

[Herreshock]

The bungee is holding the blade both in down and up positions. With current design, the blade would have to lift up at least 30° to overcome the neutral point and have the bungee start pulling it up. I don't think it should lift that much during normal sailing, especially if I tension the bungee enough

An usual important thing i think about kick up systems (they can be used for centreboards or leeboards too) is keeping working in storm weather loads and only folding on collision rather than wave pressure.

An automatic safety system to reef the sails and drop a wave orientation buoy from the stern (always a wave system instead wind orientation) and a bell with an automatic safety pulley system after folding the ruder or centreboard, etc, no need for electronics

 

[laukejas]

You had it figured out all along. My apologies for doubting the facility of that clever design.

No need to apologize, it was a valid concern. Like I said, I only discovered a solution to it by accident

An usual important thing i think about kick up systems (they can be used for centreboards or leeboards too) is keeping working in storm weather loads and only folding on collision rather than wave pressure.

An automatic safety system to reef the sails and drop a wave orientation buoy from the stern (always a wave system instead wind orientation) and a bell with an automatic safety pulley system after folding the ruder or centreboard, etc, no need for electronics

Fair point. In this case, I suppose it boils down to how tight that bungee is tensioned. I think I should be able to tension it quite a lot, because doing that kick-down movement with the tiller should be easy enough due to how long the tiller is, giving lots of leverage. I'm actually more concerned about how easy/difficult it will be to lower the blade, since for that you do need to push the tiller, there is no leverage to help with that.

 

[Herreshock]

No need to apologize, it was a valid concern. Like I said, I only discovered a solution to it by accident



Fair point. In this case, I suppose it boils down to how tight that bungee is tensioned. I think I should be able to tension it quite a lot, because doing that kick-down movement with the tiller should be easy enough due to how long the tiller is, giving lots of leverage. I'm actually more concerned about how easy/difficult it will be to lower the blade, since for that you do need to push the tiller, there is no leverage to help with that.

Maybe a rope with a mini pulley bellow the hull holding the blade from the tip

 

[laukejas]

Maybe a rope with a mini pulley bellow the hull holding the blade from the tip

Lol, now that would be a proper fish striker!

Alright, thank you everyone for the suggestions and advice, it was really fun and educating. I think this last solution is good enough for my case. The only inconvenience that remains is removing that blade from the tiller, I will try to use a pin there but if I'll see that it's not strong enough, then I'll just go with a bolt and a large knob so it can be undone without tools. When it's all finished and I'm sure this rudder works fine, I'll post the files on Thingsverse. Thanks again!

 

[Herreshock]

Lol, now that would be a proper fish striker!

Alright, thank you everyone for the suggestions and advice, it was really fun and educating. I think this last solution is good enough for my case. The only inconvenience that remains is removing that blade from the tiller, I will try to use a pin there but if I'll see that it's not strong enough, then I'll just go with a bolt and a large knob so it can be undone without tools. When it's all finished and I'm sure this rudder works fine, I'll post the files on Thingsverse. Thanks again!

I think kick up rudders can fold on storms so i already though of a rope from the bow holding the blades, maybe with a spring that releases when theres a collision load so the rudder folds, kickup appendages should be the norm and is mostly appropriate for safe cruising besides in dinghies

 

[SolGato]

My experience has been that a kick up rudder tends to want to kick up both at high speed and when tacking, especially with a buoyant blade.

You can always add an adjustable trip cleat to keep it down.

Beach Cats designers have figured out a few good methods, and I e always thought there was room for improvement with the classic Hobie design using better material and more precision engineering. When they work they work well.

 

[tdem]

I'm a bit late to the party, but here's my two cents. I personally don't like the "move tiller to disengage rudder" solution as it's too easy to accidentally activate while sailing, and could easily lead to breakage. Your mechanism seems pretty neat though. I think you could combine the principles of your design with the principles of the goat island skiff style cassette rudder. Basically, build the GIS style tiller / rudder box which is structurally very good. Place your pivoting rudder blade inside this, but use a separate arm to activate it. This could be thin and lighter, and offset sideways to lay flat against the rudder blade for storage.

Since you now have a strong rudder box you no longer need an axially strong pivot, which makes quick release solutions for the blade very simple. My previous dinghy just had a pin on a bungy. Put the pin through, and wrap the bungy around the other side of the box and over the same pin. Very simple and works great.

As a potential extra feature, I think I've also seen a beach cat solution where a similar rod was used to hold down the rudder. It was a bit springy, so with a big force on the rudder blade it would bend and pop out of its socket, allowing the blade to pivot up.