Version 1.0 | Last update: 11. November 2019

Stern Section

This section is accomodating our main propeller, rudder and dive fins.


Stern section

3D printed parts

All STL files are already oriented for generating g-code with your favorite software. Check part list on the right side of this page for best printing results.

Amethyst AUV Tail - 3D Prints

Amethyst AUV Tail - 3D Prints 2



Stern section

Assembly parts

Amethyst AUV Tail - Accessories

How manyTypeType note
16x M3x10 Stainless steel hex socket head cap screw
4x M3x25 Stainless steel hex socket head cap screw
3x M3x30 Stainless steel screw with hex head
16x M3 bolt Stainless steel
48x M3 washer Stainless steel
4x M3 spring washer Stainless steel



Stern section


Amethyst AUV Stern - Holder

Connect ring holder with main body part together as showed.

Amethyst AUV Stern - Holder orientation

Be careful orintation of holder part. Hole for motor wires above shoud face eyelet at main body on oposite side (violet arrows). Notice orientation of main body cuts (blue arrows) against holder part.

Amethyst AUV Stern - Fasten Holder

Use 4 M3x10 hex screws, 4 M3 bolts and 8 washers to unite both parts. You will find there is not much room inside the cone for work out the bolts. It needs a bit of skill and patience.

Amethyst AUV Stern - Prepare screws

Prepare 4 M3x25 screws as showed above. We gonna use them to fasten motor with propeller to main body of stern part. Put spring washer between two classic washers. Watch out, screws should not go to fare in to motor to not damage winding inside, but do not screw them too shallow as well. Adjust that by adding or removing washers if advised number of 5 washers is not sufficient. Spring washers are needed certainly, they will help avoid unwanted relese of screws due vibrations of motor.

Amethyst AUV Stern - Insert

Insert prepared screws to all four holes in Insret part. Notice orientation of Insert part.

Amethyst AUV Stern - Insert insertion

Push the screws with Insert part through the holes inside Main body part. Watch the orientation of the cut against hole of main part (blue arrow). You should already have a motor wire going through the hole and all four M3x25 screws with washers on place as can be seen on following image. This view without them is just for better visualisation of the mount.

Amethyst AUV Stern - Fasten Motor

Fasten the screws from inside of main part. Motor with prop shoud look like this.

Amethyst AUV Stern - Place Prop End

Put Prop End inside the ring fitting grooves.

Amethyst AUV Stern - Prop End Position

In to this position. And fasten srews. Don´t forget place washers under the srew heads and under the bolts as well.

Amethyst AUV Stern - Place washers

Impress washers in to holder´s arms first. It will ease work with bolts a bit.

Amethyst AUV Stern - Ring Orientation

Then arrange ring to holder´s arms, place screws and fasten ring to main part. Ring´s eyelet must be on oposite side than eyelet at main body (purple arrows). Don´t forget place washers under screws heads.



Stern section

Rudder and dive planes


 1. Assembling dive planes and rudder mounts

Dive planes are incorporated with design mainly for AUV setups without vertical thrusters. But they could be used for depth correction in all AUV configurations. Using them is up to you, regarding your planed application.

Amethyst AUV Docs - Rudder mount

Prepare rudder and mount. Mount should look like this at the end.

[picture will be available soon]

Glue the Rudder mount part with Mount bridge part as seen on picture. Notice orientation of bridge. Hole for screw shoud be orinted toward hole on bridge at the oposite side.

Amethyst AUV Docs - Rudder mount



Stern section

Attaching rudders