Rocna Anchor

Rocna Anchor – Performance and Reliability for Recreational Boating

This version of the Rocna anchor has been designed for personal use on a 5-meter boat. It is made from 8 mm thick S355 structural steel, hot-dip galvanized, with a total weight slightly over 13 kg.
The goal of the project is to keep costs down compared to the often high prices of commercial anchors, while still ensuring excellent performance.

Main Technical Features

The Rocna anchor stands out for its high holding power and quick setting ability. It is one of the most versatile anchors, suitable for various types of seabeds.

Ideal seabeds:

• Sand: rapid penetration and excellent holding.
• Mud or compact silt: good setting and holding performance.
• Fine gravel or mixed sand: maintains a good grip, even if penetration is more difficult.
• Light seagrass: capable of digging under the grassy layer, unlike many traditional anchors.

Problematic seabeds:

• Bare rock or very hard bottoms: difficult to penetrate, like most anchors.
• Coral or fractured rocks: may get stuck; caution is advised to avoid damage to the anchor or the environment.

For rocky bottoms, a second anchor is recommended, such as a grapnel or a model specifically designed for rocky terrain.

Materials and Construction

The anchor can be built using stainless steel, marine-grade aluminum, or structural steel. Below is a comparison of weights and characteristics based on material and sheet thickness.

Stainless Steel or S355 Steel (requires hot-dip galvanizing)

Thickness	Estimated Weight
8 mm	13.5 kg
10 mm	17 kg
12 mm	20 kg
15 mm	25 kg

Technical note: S355 is prone to corrosion, so it is recommended to:

• Sandblast and hot-dip galvanize (galvanizing is effective only if applied on a surface free from mill scale).
• Alternatively, sandblast, pickle, and paint using epoxy or polyurethane coatings.

Marine Aluminum (5083, 5052, 6061, 6063 alloys)

Thickness	Estimated Weight
10 mm	5.7 kg
12 mm	6.8 kg
15 mm	8.5 kg

These magnesium-based alloys are ideal for marine environments due to their excellent corrosion resistance.

Recommended Rocna Anchor Weight Based on Boat Length

Boat Length (m)	Recommended Anchor Weight (kg)
5 – 7	7 – 14
7 – 9	14 – 22
9 – 12	22 – 36
12 – 15	36 – 55
Over 15	55+

General rule: approximately 1.5 kg of anchor per meter of boat length, with higher weights recommended for challenging seabeds or severe weather conditions.

Assembly

The anchor components are laser-cut or CNC-machined from sheet metal and include interlocking tabs to ensure correct assembly.
Once cut, the pieces must be carefully welded according to the specifications of the chosen material.

Legal Notice

This project is intended for private and recreational use only.
It is ed under the domain LDpro3D, owned by Lombardo Davide.
Any commercial reproduction, full or partial, is strictly prohibited. Violators will be prosecuted under applicable law.
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Final Technical Note

Laser cutting and CNC milling parameters vary depending on the machine and operator preferences.
Universal settings cannot be provided, but suitable equipment must be used for the materials and thicknesses specified