Nautilus Drydocks ALVIN (3D printed)

[gboxwood]

That's perfect! I got carried away by your setup in your video...

[He Who Shall Not Be Named]

As your ballast water quantity is small and gear-pumps leak internally, go with a peristaltic pump and eliminate the solenoid valve.

The best part is no part (I'm channeling Elon Musk here).

Peristaltic type pumps have a very low CFM rate, but your ballast tank will be small so a slow fill/drain will not be a big deal with this model. And these pumps are true positive displacement types -- they don't leak internally no matter the backpressure.

However, it's good engineering practice to provide your tank with a pressure relief valve or you'll eventually rupture the thing (something simple, like a whoopie cushions 'splatter valve'), as peristaltic pumps can reach ruthlessly high backpressure if not monitored by you or a pressure activated switch.

Nuts!... now we're back to a two-component system. Sue me.

David

[Subculture]

As your boat is printed you should be able to slice the 3d file at the intended waterline, and have the software give you the volume of the material above the waterline, which will give you a good benchmark for the ballast tank requirements.

Peristaltic pumps

3d files- I'd use a smaller geared motor though.

https://www.thingiverse.com/thing:4653708

Off the shelf. Pay the extra for the Pharmed tubing, it's worth it.

https://www.aliexpress.com/item/32817707131.html

Use with a flexible bag and an esc, and you'll have a very good system that gives excellent control.

A bit ghoulish, but they're strong. If too big or too small, there are alternatives.

https://www.aliexpress.com/item/1005004377774454.html

[gboxwood]

Perfect, this is golden. I had already selected a peristaltic pump and that specific one in particular. I think I got lucky with it.

One last question: any advice/preference for the solenoid valves you typically use?

In the meantime I'm designing the equipment and ballast tank WTC's, sizes are going to change but I want the overall setup in place so I can test print a couple of components and check their tolerances.

ALVIN-013 by Giacomo Bosso, su Flickr

I could source a 78/85 tube which is currently 300mm long for a volume of approx. 1.4 liters (endcaps excluded).
I will definitely check the more exact volume as you suggested.

[Subculture]

You shouldn't need any valves with a peristaltic pump, they're self-checking.

[Subculture]

Your design looks similar to Bob's. Bob can answer this better than I, but I'm guessing the C.G was far forward on his build, which will work, but will make the dynamics of the boat different to a more central c.g and the thrusters will be acting behind instead of on or just slightly ahead of the c.g.

You have a very short and fat hull with the Alvin, so if you favour a fixed (hard) tank have you considered using a large diameter but short length tank, which minimises sloshing when filling and takes up less room longitudinally.

[gboxwood]

Your design looks similar to Bob's. Bob can answer this better than I, but I'm guessing the C.G was far forward on his build, which will work, but will make the dynamics of the boat different to a more central c.g and the thrusters will be acting behind instead of on or just slightly ahead of the c.g.

You have a very short and fat hull with the Alvin, so if you favour a fixed (hard) tank have you considered using a large diameter but short length tank, which minimises sloshing when filling and takes up less room longitudinally.

Yes, you are right about it and I have experience with this (less favorable) setup on one of my turbine jets, where the previous owner used 2 soda bottles as fuel tanks with a detrimental impact on the CG.

Senza titolo by Giacomo Bosso, su Flickr

I changed the setup and molded much higher and shorter tanks which I located as close as possible to the CG location.

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

I could do something similar with the ALVIN but first I want to understand how big of a problem the current setup is.
I also do not plan on using functional thrusters at the moment, something for later maybe.

[gboxwood]

Today I did some experiments and mocking up...

First of all, working with the tubes is much easier than I expected and the first test prints turned out to be of a great fit:

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

[gboxwood]

Then I tried to fit the battery and the two tubes one on top of the other... I coudn't.

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

The tubes fit if they do not rest on top of the battery and this is the way I think I'll go.

Senza titolo by Giacomo Bosso, su Flickr

I change battery sizes and locate two of them next to the WTC assembly so I can also shift them to the front and to the back as required.

[gboxwood]

The rest of the day was some painful sanding of the bottom hull exterior and some CAD work.

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

I decided to reinforce the outside of the joints as well, I'm worried this boat will be quite heavy in the end...

Senza titolo by Giacomo Bosso, su Flickr

[gboxwood]

I'm updating the CAD design as I learn new things. I also started populating the equipment WTC and everything will keep changing until I modeled it all and I found the optimal positioning.

ALVIN-015 by Giacomo Bosso, su Flickr

ALVIN-016 by Giacomo Bosso, su Flickr

[RCSubGuy]

Looking great so far...!

[redboat219]

Do you really need those screw holes near the edge of your cylinder?

They have the potential to start a crack in your cylinder wall.

[He Who Shall Not Be Named]

Do you really need those screw holes near the edge of your cylinder?

They have the potential to start a crack in your cylinder wall.

No ****, Sherlock!

David

[gboxwood]

Do you really need those screw holes near the edge of your cylinder?

They have the potential to start a crack in your cylinder wall.

Yes, I'm worried about that... I put them on the outside so that any leakage between the bolt and the tube is protected by the O-rings.

I'm not using countersunks... maybe that helps...