The Gun project: 3D glassing techniques on the 16-021



3D glass has about eight times the resistance to buckling as the same weight of conventional glass. The reason for this is that it creates a beam structure, with two layers of cloth separated with an air gap and connected by glass fibre pillars. This is similar in principle to  composite skins commonly used on surfboards. Examples of these skins being layers of glass or other cloth with high density foam or balsa wood sandwiched in between. The aim is to increase the thickness of the skin structure without increasing the weight.

Rows of figure eight shaped pollars act as spacers and springs to absorb impact. Capillary action makes the resin rise up the pillars to wet them out. The fabric was invented by a velvet manufacturer who was looking for a new market due to low sales, it's the same weaving process used for velvet except that in the case of velvet the pillars are cut, to separate the top and bottom layers, leaving a cut pile.

An advantage of 3d glass over other composite skins is that it can be applied in one go, and there's no issue with bonding between layers as the top and bottom layers plus pillars are all woven together and are wet out at once with the same batch of resin.In this case the 3D skin is 3mm thick.

Fairing of the 16-021 surfboard hull

Issues with the process so far have been:

• The cloth has a distinct weave texture which requires more filler coats
• Drapeability is not good. The cloth itself seems stiff until wet out, and only drapes gradually. Our 3D cloth is from a Chinese company and has a different internal structure to cloth made by Parabeam in the Netherlands. Parabeam claim that their cloth has excellent draping quality.
• When applying pressure to the cloth to get it to stick to the foam on the rails, one has to be careful not to compress the 3mm layer down, it's ok as long as the resin has not reached the tacky stage, but unfortunately the tacky stage is when the cloth is able to be stuck down to the foam, so there's a conundrum there. For future boards we intend to apply resin to the board first, wetting out only the bottom layer and getting that to stick before adding the top layer of resin.
• Lap joins cant be used as the cloth is too thick and has an internal gap, so a butt join must be used instead.

Structural epoxy fairing compound is applied to fill the 3D glass weave pattern.

In spite of the above difficulties we'll be continuing to use 3D glass as the strength to weight ratio is impressive and it has some interesting visual effects.. The job is time consuming and not for the faint of heart however.

The soft, rounded hull shape of the 16-021 gun surfboard.

Read more about the 16-021 Gun design here