Surf skis are mainly made in wet layup or infusion technology, only a few brands use the Prepreg to make surf skis, the reason is the prepreg way is more expensive and requires a lot more up-front investment in facility and equipment. This article is just to show you how the Haocomposites make prepreg surf skis for Nordic kayaks.
Need the right Mold to be satisfied the Prepreg production.
Prepreg is the common term for a reinforcing fabric that has been pre-impregnated with a resin system. This resin system (typically epoxy) already includes the proper curing agent. As a result, the prepreg is ready to lay into the mold without the addition of any more resin. For the laminate to cure, it is necessary to use a combination of pressure and heat.
Normally, the heat temperature is around 120 degrees, which means, the surf skis’ production needs a mold that can suffer a temp as high as 120 degrees and even high(considering the molds have been heated time and time, so normally above 120 degrees). Haocomposites make the mold in a resin infusion way, the epoxy resin can be heated to 150 degrees. And to pursue a better finish for the surf skis surface, we use the “mold gelcoat”. Then makes the unique “naked” construction possible(about this construction, can find more details later).
Laminate process for a Prepreg surf ski.
Once the mold is ready, then can start the laminate.
- Step 1, is to use a CNC router to cut the Prepreg materials into pieces based on designed patterns. Those patterns were tested several times before applying on the final skis, the purpose is to control the materials to use, neither more nor less than what is needed;
- Step 2, is to pre-forming the PCV foam core. Yes, Haocomposites use the Divinycell as the core material, which meets the demands in higher temperature processing, just ideal for our low-medium temperature prepreg systems. We use a heat gun to pre-form the shape of PVC cores on the molds first, to avoid any “break” during laminate;
- Step 3, is to put Prepreg materials and PVC foam core together. We use the sandwich construction, out-skin and inner skin use the UD carbon or fiberglass prepreg, in the middle is the PVC foam, reinforce the areas with extra materials, then vacuum bagging.
The Autoclave is a weapon to cure the surf ski.
The ideal curing environment is an autoclave which has both temperature and pressure controls, although prepregs are commonly cured in ovens. Haocomposites has 3 autoclaves, to cure the surf skis is the one in a 8m long, although it is a process often used for the space industry and F1 cars. Normally cure the skis with 3x atmospheric pressure, the temperature is 120 degrees, for 4 hours.
The key to making a prepreg surf ski is above, then do the bonding deck and hull, sanding and painting, and parts on, in the end, a light and stiff prepreg surf ski are done. The lightest construction, for a complete ski, is only 8kg, possibly the lightest one in the market, but yet still super strong.
