ConstraintFix is a small companion mod that repairs a critical bug affecting airships and any structure containing rope_connector, rope, spring_connector and spring blocks from Create Aeronautics.
The Problem
When you copy a structure that contains ropes or springs — for example an airship whose balloon is connected to the hull by ropes, or landing gear attached with springs — and paste it using a Structure Block, a Create schematic, an NBT file loaded by another mod, or any template system, here's what happens: The rope or spring looks intact (the knot/anchor texture and attachment points are visible) But the rope or spring doesn't physically exist — you can't grab it, it doesn't swing, compress, or stretch, it has no physics This happens because Create: Aeronautics saves rope and spring strand data using absolute world coordinates.
When the structure is pasted at a new location, those coordinates still point to the original build — the engine destroys the strand immediately, but the visual knot/anchor survives, giving the illusion of a working rope or spring.
The Fix
ConstraintFix intercepts rope and spring data at load time, detects that the connector was relocated (its saved anchor no longer matches its real position), strips the broken strand before the engine ever sees it, and automatically re-creates the rope or spring at the correct position on the next server tick. Physics assembly (Sable sub-levels) is fully handled: the mod recognises world↔plot coordinate transfers and leaves them untouched, so assembled airships keep their ropes and springs through physics simulation.
Issues
please, report any bugs or else here (https://github.com/emariduble-cmd/Constraint_Fix/issues), I will fix it as fast as possible
Requirements
(https://www.curseforge.com/minecraft/mc-mods/create-aeronautics)
Notes
Structures pasted before installing ConstraintFix can't be auto-repaired — re-paste them once with the mod installed.
How to Install Create Aeronautics: Constraint Fix (Mod)
Create Aeronautics: Constraint Fix by duble is verified for Neoforge across Minecraft versions 1.21.1 (latest release: 1.6.0, file size: 21 KB). Follow the steps below to install it safely from ModCraft.tv:
- Click the Download button above and select your Minecraft version (1.21.1) and platform (Neoforge).
- Make sure you have the compatible loader or environment installed for Neoforge.
- Move the downloaded Create Aeronautics: Constraint Fix file into your Minecraft
.minecraft/modsfolder and launch the game.
All Versions
+ Add Version
- Fixed ropes and ziplines breaking during chunk load/unload with a new 100-tick
- Fixed server crash (IllegalArgumentException: the second position is in the plotgrid) when a block on a flying ship carrying rope connectors is broken
- Crash is now caught at the physics tick level — affected rope goes slack for that tick instead of killing the server****
- Fixes**
- Fixed server crash caused by Create Aeronautics 1.3.0 API update
- Ropes are now correctly recreated when pasting structures and during Sable assembly
- Resolved "connection lost" error when spawning simulated structures
- Compatible with**
- Create Aeronautics 1.3.0+
- Sable 2.0.3+
remaps the strand anchors (START/END + points) by the block's own move delta instead of
letting Simulated destroy them (ghost knot: rope rendered but attached to nothing, wrench KO).
Edge case: copy of a connector roped to an already-assembled ship → ghost knot stripped
(wrench usable again).
World→world structure-block copy: unchanged (strip + re-link).
- Fixed a rare NullPointerException (NPE) that could still occur during Sable movement updates when a connector had a null rope strand.
- Added a safety guard in makeUpdatePacket(): if no server-side strand exists, an empty rope data packet is sent instead of crashing.
- Added accessor for the private owned server strand field.
