On the Hawk20 day boat, small items such as phones, snacks, handheld radio etc would normally be stored in the lockers mounted in the forward bulkhead (red). When sailing solo these aren't ideal and don't allow for quick access. I needed to have something closer to the aft steering position (blue).

I wanted something that didn't require any permanent attachments or new holes. The solution would need to be removable for when I have other people onboard or need to access the seat storage

Supplies

1 sturdy plastic box

2 x 160cm lengths of 1" inch wide webbing strap

4 x 1" inch snap buckles

2 x short lengths of rope

1 x length of elastic cord

hot knife for cutting ropes and straps is useful but not essential

sewing equipment

sharp knife

Step 1: Cut Holes Into Bottom of Box

I'm not too worried about the box being completely watertight at this point, just enough to prevent incidental water splashes from spray and/or rain. The straps just need to hold down the box securely. To achieve this I cut four holes in one side as shown, using a sharp craft knife. Cut another 4 holes in the other side.

Step 2: Attach Buckles to Webbing Straps and Ropes

The webbing straps though the box are made as short as possible to prevent the box from sliding back and forth. To help with this, the buckles were sewn using a sewing machine but hand sewing would achieve the same thing.

The other end of the buckle wasn't sewn, to allow for tightening and adjustments when installed.

Webbing straps are sewn onto short lengths of rope to prevent the ropes from sliding clear. The ropes will be slid down the sides of the storage seats and when the straps are tightened will jam like a bolt rope.

Step 3: Added Bungy Cord to Secure Lid

To help secure the lid and prevent it disappearing in windy conditions, I added a length of elasticated bungy cord, through a hole on either side of the box.

Step 4: Install

The box was installed with only 1 strap as a test to confirm experiment, before committing to further work. Have since added a second strap for extra security/stability.

See results video at https://youtu.be/RDejg9WzDlA