Hot Tub Construction
Acrylic hot tub shells are usually contructed using a layering process. Firstly a layer of acrylic is vacuum formed into the shape of the hot tub. Then a layer of vinylester bonding resin, a liquid plastic that acts as both a bonding agent and a barrier to moisture, and fibreglass matting is applied. A mixture of polyester resin and chopped fibreglass may then be sprayed on and the whole shell will be oven-baked. Finally, in good quality hot tubs, a thick layer of closed cell foam insulation is also sprayed on to the rear of the acrylic shell to minimise the heat loss to the cabinet.
The plumbed shell is then mounted in a cradle robustly constructed with pressure treated timber. The corners of the frame are re-inforced and cross bracing and seat supports are added for strength. The weight of the spa, water and people is equally spread by using blocks that are fibreglassed under every seat.
Most hot tubs are fitted with a fibreglass base which is securely attached to the frame to provide a waterproof barrier to protect the hot tub equipment. Often, the base is internally sprayed with a thick layer of foam insulation to stop heat loss to the ground..