LA Class Scratch build using arduino and pistons

[cdivine]

I do not know if a sharp edged propeller is better than a rounded off edge.

I did study the Wright brother's build of their airplanes.
They made a water tank that they could put various items in and see the water flow around and over these items.
The water had some sort of particles in it to show turbulence.
Contrary to what I would have thought, the rounds edge was not the best shape to reduce turbulence.
It turned out from their testing that a square strut with rounded corners disturbed the flow less than the others.
They tested for strut and framing issues and not as much for airfoil shapes.

Airplane propellers have a rounded leading edge and may have a sharp trailing edge.
The idea is to displace a lot of water or air at the leading edge and then have two surfaces. One that is straight or con caved to give the shortest distance for medium travel. The other side is convex to make the medium travel farther and faster to create a low pressure area which pulls the propeller towards the low presser.

A sharp edge trying to split the medium instead of pushing it away and around the edge can create harmonics. (not necessarily good for propulsion. very noisy)

Something I remember from my early years.

Wow cool stuff I didn't know. I guess we're seeing this on modern subs with more blades with flat edges running along the inner side of a shroud to eliminate cavitation increase propulsion efficiency at higher speeds. So now they can move faster with fewer tuns on the prop thereby quieting the sub even at higher speeds. Really cool stuff.

[Guest]

Using an aerofoil shape on the outer edges of a prop can be too much of a good thing with the large pressure differential created giving rise to early cavitation. Thus a ogival section tends to be used with sharp leading and trailing edges. As the blades narrower in towards the boss, they can be given a more aerofoil shape.

In model form I guess this less likely to be an issue, but worth bearing in mind if scale authenticity is your goal.

[johnredearth]

Hi all



I have not been posting much due to a few challenges, but I am proud to announce that the LA is finished, including all the videos. They are all on my web page for you to see. (Please note that ScratchbuildwithJohn is completely free). The first few videos (LA 2-3b) are in fact the latest, summarising what worked and what didn’t, quirks in sailing in and of course ‘how it works.’ I have also loaded the circuit diagrams and the arduino code, which does all the magic. I am particularly pleased with the depth keeping system.

I have some new projects ahead one of which relates to subs in that I will be providing some info on using Orange 433 units. There is already lots of good stuff out there, but even using that I spend days of frustration. I will share everything I have learned and use other resources which I think are excellent.



For more on new projects check my latest blog.

Also, I now have a Patreon page. I have described why this page exists ‘on the page,’ but in short I have been diagnosed with Cancer. It is a brain tumour. The good thing is that I am doing very well, and I am the fair haired boy at the hospital. But we know this will not go away and the significant issue is I can’t work. Unfortunately I always thought of myself as indestructible and now I can’t provide for my family. I can play however. So visit my Patrion page to find out more about all this.

Also, the idea of crowd funding is about a little bit of support from lots of people. So could I ask you to share my Patreon page with your friends and contacts. It’s only partly about models.