I drew the model in Autodesk Inventor. I can confirm that it holds at least 80kg.
I made the connectors for:
wooden sticks with a 19mm diameter
wooden board with 20mm thickness
But you can change the dimension as you like.
Assembly
Material for assembly
Screws
Drill
Wooden sticks
Wooden board
How to assemble
Cut the wooden stick to the correct length
Prepare the wooden board to your liking. I sanded the wood and applied a oil.
Drill a hole through the 3D printed part and the wood to screw in the screws later.
Print settings
Material
I used PLA but it depends on how and where you want to use the rack. If the rack will be exposed to higher heat, consider using PETG or other higher temperature materials like ABS, ASA, etc.