The manufacturing process

 

 

There are three different processes to laminate a carbon mast :
  • Filament Winding
  • Molding on a Male mandrel
  • Molding in Female tooling

A.Filament winding

Process description

A carbon thread, impregnated with resin is rolled up on to a rotating  mandrel of the same section as the mast interior, with an angle varying from 90° to 7° compared with the mandrel. Once the winding is finished, the mast is cured under pressure to compact the different carbon layers to eliminate any voids.  A more sophisticated method would be to use a pre impregnated thread and curing in autoclave under pressure. All the patches for local doublers are placed on the outside of the tube. This process is mostly used for mass production, such as for windsurfing masts or smaller size yacht masts.

Advantages

  • This process is less labor intensive than the others and therefore more economical.

Disadvantages

  • The compression load of the mast is in the vertical axis and therefore it’s critical to have most of the fibers directly in line with the vertical axis of the mast and not at an angle of 7° or more.  This means more fibers will be required to obtain the same stiffness leading  to a heavier tube.
  • By compacting the carbon towards the mandrel, the exterior layers are reduced in diameter, the fibers are not under tension and lose a part of their efficiency.
  • The finish after curing has a weaving aspect with all the patches visible and in order to obtain a perfect smooth finish requires a lot of fairing, which again increases the weight of the mast tube.

B.Molding on a Male mandrel

Process description
Pre- impregnated carbon fibers are positioned on an aluminium mandrel of a similar section to the interior of the mast. The tube is then debulked by winding it in several layers of shrink tape  to compact the different carbon layers and  to eliminate any voids. Once these operations are finished, the mast is cured under pressure in autoclave. Patches for local reinforcements are placed on the exterior of the mast tube.

Advantages

  • This process requires less capital investment than the female tooling process.

Disadvantages

  • By compacting the carbon layers towards the mandrel, the exterior layers are reduced in diameter and like in the filament winding process you end up with fibers not perfectly tensioned, therefore the full benefit of the fibers is not used.
  • The finish of the spar is very similar to the filament winding with the same disadvantages mentioned above.

C.Molding in Female tooling – AXXON process

Process description

Pre- impregnated carbon fibers are placed into aluminium female tooling.
The two halves are debulked several times under vacuum in order to compress the material toward the tooling and to eliminate any voids. Patches for all the local reinforcements are placed on the inside surface of the mast tube. Once the laminating process is finished, the two halves are put together with an overlap of the fibers and cured under pressure in autoclave.


Advantages

  • By compacting the carbon layers toward the tooling optimizes  the tension of all the off axis materials and by using aluminium tooling which expands with  the increase in temperature  to 125° during the curing process, all the unidirectional fibers are perfectly aligned and tensioned.
  • This process leaves a perfect tool finished exterior surface with all the local doublers inside and does not require  any filler or fairing prior to painting.

Disadvantages

  • This process is more labor intensive than the previous processes and requires more initial capital investment in toolings.