You absolutely need to ground your aluminum arch for safety reasons. Both your solar panel and wind generators are connected to you
batteries via charge controllers (all 12v), but your 120 AC
power battery charger is also connected to your
batteries as well. While rare, either a
lightning strike, or more likely a voltage spike, or
malfunction can cause a short/ issue with the battery
charger (especially transformer-less 'switching' chargers) which can result in lethal 120 voltage 'leakage' into its 12v DC line. Anything that is metal on a boat that has either DC devices (or AC devices) connected/ mounted to it must be grounded to the ship's ground (usually the
engine block). It is also the attachment point of your electrical panel green (ground) wire. Every solar panel,
wind generator, sat/ TV/
radio antenna is designed knowing if it is mounted to metal, it is ground to the ship's ground. This ensures that all metal objects on a boat that you can touch with wet feet/ hands are electrically bonded together and at the same zero potential. Keeping everything bonded actually reduces electrolysis issues.