3.3 Vehicle Operations

3.3.1 Launch/Recovery

Teams are responsible for safely launching and retrieving their vehicle. You may lower and raise your vehicle from the side of the pool at your designated section (A, B, C, D), provided it can be done safely.

The pool is 7 ft (2.1 m) deep, with a 1 ft (0.3 m) drop from the pool deck to the water surface.

At each section, a 10 ft (3 m) long pipe with a four-point harness will be provided. Teams will secure their vehicle’s hard points to the harness. With two team members, lift the vehicle from its stand, position the vehicle over the water, and lower it into the water. Once in position, a team member can reach down from the edge to unhook the four connections points. To retrieve the vehicle, simply reverse the procedure.

Figure: Raising and lowering the vehicle

For Alpha (A), and Delta (D), we recommend bridging the corner to lower/raise your vehicle. For Bravo (B) and Charlie (C), a platform will be in the water for the divers to use to assist lowering/raising your vehicle in/out of the water. Someone should be in the water to help keep the vehicle off the wall as the team is lowering/raising the vehicle.

Figure: Location of launch/recovery bars

3.3.2 Harnessing the AUV

For the safety of your vehicle, all teams are required to use a harness or sling when launching or retrieving from the water. Even if the vehicle is light enough to hand-carry, a simple slip could result in serious damage — to your vehicle or equipment. Using a hoist is a much safer and more controller method. In addition, your vehicle may need to be suspended for weighing. It's strongly recommended that you — the builder — integrate sling attachment points into your vehicle's frame during the design process. This is far preferable to us (the competition coordinators) having to improvise a solution on-site at the last minute.

Figure : Examples of harnesses

What to Consider

1. Hard points on the vehicle. These are strong, secure attachment points that can support the full weight of your vehicle

2. Chain, rope, sewn slings

   • Chain: Easy, durable, and ready to go.

   • Rope: More flexible, but required good knots.

     • Any knot reduces the breaking strength, but each know effects the rope differently.

   • Sewn slings (aka "runners"): Available at rock climbing stores, REI, or online. Made from materials like Nylon, Spectra, or Dyneema — all plenty strong for this use.

3. Attachment method: The easier and quicker it is to attach and detach the harness, the better — especially for people in the water or surface operators.

Figure : Sewn slings (runners)

Recommended Knots for Rope Harnesses

If you're using rope, you'll need to tie proper knots to attach to your vehicle's hard points. Hare the the ones worth knowing:

• Figure 8 Rewoven

  • Retains ~80% of rope strength

  • Easy to tie and inspect

  • Can be difficult to untie after heaving loading

• Bowline

  • Retains ~70% of rope strength

  • Creates a secure loop that's easy to untie, even after loading

  • Great for quick setup, but be cautions of the rope ends

• Double or Triple Fisherman's (aka Grapevine) Knot

  • Best for joining two ropes together or creating a permanent loop

  • Very secure and compact.

Figure : Figure 8 rewoven knot

Figure : Bowlineknot

Figure : Double Fisherman's knot

Connecting Everything Together

To attach your harness (chain, rope, or slings) to your vehicle, use carabiners. Climbing carabiners like the Black Diamond Oval are reliable and inexpensive. You might find alternatives at your local hardware store — but make sure they're rated to handle the full weight of your vehicle, with a safety margin.

Figure : Black Diamond oval carabiner

Final Tip: Keep It Simple

Follow the KISS principle — Keep It Simple, Stupid. Your goal should be a harness system that's:

• Easy to set up and break down

• Quick to attach and detach

• Intuitive enough for someone in the water to operate without hassle.

3.3.3 Team Swimmers

Teams may have an opportunity to volunteer a swimmer(s) on their team to assist with in-water safety and operations. The volunteer swimmer(s) will be required to tread water for 1 minute each time they enter the water (reminder, the whole pool is 7 feet deep!). It is allowed for teams to use another team's swimmer to swim for their run.

For Semi-Finals, Third-Chance, and Finals, no team-provided swimmers will be allowed. Only during Practice/Qualifying runs.

Teams are asked to bring their own swimming equipment (i.e. masks, snorkels, fins, etc.). RoboNation will have a few spare pieces of equipment available for shared use.