Answers.Body: <p>The LEGO RC boat by <a href="https://youtu.be/3hwMOtjNZAM" rel="noreferrer">Slewentogzz</a> claims to have a top speed of 3 km/h, it uses a custom propellor built out of Technic parts.</p>
  
  <p>The actual rudder parts appear to be Technic Panels <a href="https://www.bricklink.com/v2/catalog/catalogitem.page?P=87080#T=C" rel="noreferrer">#87080</a> and <a href="https://www.bricklink.com/v2/catalog/catalogitem.page?P=87086#T=C" rel="noreferrer">#87086</a>. These panels are very common and are available in over 60 sets.</p>
  
  <p>There are two more parts in a similar design (<a href="https://www.bricklink.com/v2/catalog/catalogitem.page?P=64683#T=C" rel="noreferrer">#64683</a> and <a href="https://www.bricklink.com/v2/catalog/catalogitem.page?P=64391#T=C" rel="noreferrer">#64391</a>, they are one stud longer each so you can make a slightly larger propellor.</p>
  
  <p><a href="https://i.sstatic.net/xo6uN.jpg" rel="noreferrer"><img src="https://i.sstatic.net/xo6uN.jpg" alt="enter image description here"></a></p>
  
  <p><a href="https://i.sstatic.net/5kqZr.jpg" rel="noreferrer"><img src="https://i.sstatic.net/5kqZr.jpg" alt="enter image description here"></a></p>
  
  <p><a href="https://i.sstatic.net/fUKfW.jpg" rel="noreferrer"><img src="https://i.sstatic.net/fUKfW.jpg" alt="enter image description here"></a></p>
  
  <p><strong>Images:</strong> <a href="https://www.facebook.com/slewentogzz/" rel="noreferrer">Slewentogzz Lego Creations</a></p>
  
  <p><strong>Video:</strong> <a href="https://www.youtube.com/watch?v=3hwMOtjNZAM" rel="noreferrer">"Lego RC Boat with custom built propeller (3,0 km/h!)"</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-13T22:40:31.873Z
Answers.Text: I've tried the propeller. Unfortunately, I found it still under-performs paddle wheel designs. Not a bad suggestion for an alternative propeller design though!
Answers.UserDisplayName: Alexander O'Mara
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-13T22:47:13.470Z
Answers.Text: In theory, I don't think a paddle wheel can be as efficient as a propellor.
Answers.UserDisplayName: Ambo100
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-13T23:51:48.280Z
Answers.Text: Yeah, that's my understanding too... But in practice LEGO doesn't make a proper water propeller.
Answers.UserDisplayName: Alexander O'Mara
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-14T06:34:24.943Z
Answers.Text: @Ambo100, a *properly shaped* propeller is far more efficient than a paddle wheel because it takes advantage of hydrodynamic lift rather than merely direct displacement of the water.  The hard part is getting the shape right  -- if you don't have the right curves to produce lift, you're wasting most of your energy just churning the water.
Answers.UserDisplayName: Mark
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-13T13:58:59.700Z
Answers.LastActivityDate: 2017-12-13T13:58:59.700Z
Answers.UserDisplayName: Ambo100
Answers.Body: <p>Rather than making your own propeller with piece- which might break under the stress of water- i recommend using a different propeller like:</p>
  
  <ul>
  <li><a href="https://www.brickowl.com/catalog/lego-black-propeller-with-3-blades-5-diameter-92842" rel="nofollow noreferrer">https://www.brickowl.com/catalog/lego-black-propeller-with-3-blades-5-diameter-92842</a></li>
  <li><a href="https://www.brickowl.com/catalog/lego-propellor-2-blade-9-diameter-2952" rel="nofollow noreferrer">https://www.brickowl.com/catalog/lego-propellor-2-blade-9-diameter-2952</a></li>
  </ul>
  
  <p>More propellers:
  <a href="https://www.brickowl.com/catalog/lego-parts/vehicle/propeller" rel="nofollow noreferrer">https://www.brickowl.com/catalog/lego-parts/vehicle/propeller</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-13T22:42:02.150Z
Answers.Text: As far as I can tell, and according to my one link, these propellers are actually worse than the yellow one pictured due to how small the blades are and how shallow the blade are pitched.
Answers.UserDisplayName: Alexander O'Mara
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-13T13:25:44.077Z
Answers.LastActivityDate: 2017-12-13T13:25:44.077Z
Answers.UserDisplayName: Vikhyat Agarwal
Body: <p>I enjoy making Power Functions-controlled boats to race (in water) in various LEGO convention competitions (which require 100% genuine LEGO pieces).</p>
  
  <p>Usually, these boats end up being paddle boats, because of how inefficient all the LEGO propellers are. Supposedly <a href="https://www.bricklink.com/v2/catalog/catalogitem.page?P=4745" rel="nofollow noreferrer">Propeller 2 Blade Twisted (4745)</a> is actually <a href="http://www.moc-pages.com/moc.php/416815" rel="nofollow noreferrer">the most-efficiently shaped LEGO water propeller</a>.</p>
  
  <p><a href="https://i.sstatic.net/oISHO.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/oISHO.png" alt="Propeller 2 Blade Twisted part image"></a></p>
  
  <p>There are a number of problems with this propeller.</p>
  
  <ul>
  <li>The blade are thick.</li>
  <li>There is no good way to attack an axle to it.</li>
  <li>The shape of the blades is sub-optimal.</li>
  <li>It's on the small side.</li>
  </ul>
  
  <p>Is there a way to build a more-efficient one, out of several pieces?</p>
  
Tags: <building>
Title: Building a more-efficient water propeller?
UserDisplayName: Alexander O'Mara
ThreadText: # Building a more-efficient water propeller?
  
  (Asked by: username_0 on 2017-12-13)
  
  I enjoy making Power Functions-controlled boats to race (in water) in various LEGO convention competitions (which require 100% genuine LEGO pieces).
  
  Usually, these boats end up being paddle boats, because of how inefficient all the LEGO propellers are. Supposedly [Propeller 2 Blade Twisted (4745)](https://www.bricklink.com/v2/catalog/catalogitem.page?P=4745) is actually [the most-efficiently shaped LEGO water propeller](http://www.moc-pages.com/moc.php/416815).
  
  [![Propeller 2 Blade Twisted part image](https://i.sstatic.net/oISHO.png)](https://i.sstatic.net/oISHO.png)
  
  There are a number of problems with this propeller.
  
  * The blade are thick.
  * There is no good way to attack an axle to it.
  * The shape of the blades is sub-optimal.
  * It's on the small side.
  
  Is there a way to build a more-efficient one, out of several pieces?
  
  **Tags:** building
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2017-12-13. Score: 5 | Accepted answer
  
  The LEGO RC boat by [Slewentogzz](https://youtu.be/3hwMOtjNZAM) claims to have a top speed of 3 km/h, it uses a custom propellor built out of Technic parts.
  
  The actual rudder parts appear to be Technic Panels [#87080](https://www.bricklink.com/v2/catalog/catalogitem.page?P=87080#T=C) and [#87086](https://www.bricklink.com/v2/catalog/catalogitem.page?P=87086#T=C). These panels are very common and are available in over 60 sets.
  
  There are two more parts in a similar design ([#64683](https://www.bricklink.com/v2/catalog/catalogitem.page?P=64683#T=C) and [#64391](https://www.bricklink.com/v2/catalog/catalogitem.page?P=64391#T=C), they are one stud longer each so you can make a slightly larger propellor.
  
  [![enter image description here](https://i.sstatic.net/xo6uN.jpg)](https://i.sstatic.net/xo6uN.jpg)
  
  [![enter image description here](https://i.sstatic.net/5kqZr.jpg)](https://i.sstatic.net/5kqZr.jpg)
  
  [![enter image description here](https://i.sstatic.net/fUKfW.jpg)](https://i.sstatic.net/fUKfW.jpg)
  
  **Images:** [Slewentogzz Lego Creations](https://www.facebook.com/slewentogzz/)
  
  **Video:** ["Lego RC Boat with custom built propeller (3,0 km/h!)"](https://www.youtube.com/watch?v=3hwMOtjNZAM)
  
  > **Comments:**
  > **username_0**: I've tried the propeller. Unfortunately, I found it still under-performs paddle wheel designs. Not a bad suggestion for an alternative propeller design though!  
  > **username_1**: In theory, I don't think a paddle wheel can be as efficient as a propellor.  
  > **username_0**: Yeah, that's my understanding too... But in practice LEGO doesn't make a proper water propeller.  
  > **username_2**: @Ambo100, a *properly shaped* propeller is far more efficient than a paddle wheel because it takes advantage of hydrodynamic lift rather than merely direct displacement of the water.  The hard part is getting the shape right  -- if you don't have the right curves to produce lift, you're wasting most of your energy just churning the water.  
  
  ---
  
  ### Answer by username_3 on 2017-12-13. Score: 1
  
  Rather than making your own propeller with piece- which might break under the stress of water- i recommend using a different propeller like:
  
  * <https://www.brickowl.com/catalog/lego-black-propeller-with-3-blades-5-diameter-92842>
  * <https://www.brickowl.com/catalog/lego-propellor-2-blade-9-diameter-2952>
  
  More propellers:
  <https://www.brickowl.com/catalog/lego-parts/vehicle/propeller>
  
  > **Comments:**
  > **username_0**: As far as I can tell, and according to my one link, these propellers are actually worse than the yellow one pictured due to how small the blades are and how shallow the blade are pitched.  
  
  ---
  
  