HD Carbon Extension 32cm

Some of the main differences of this extension is the slightly increased diameter of 32.5mm over the standard 31.5 to 32mm to reduce play inside the mast creating point loads and turning the holes 90° so they are length wise in stead of across. With aluminium extensions that were bent you can clearly see all RDM extensions bend sideways. So the biggest forces on an extension is side ways from getting washed in waves, not from the downhaul tension. Strength analyses show that by turning the holes 90°, the highest force in the tube (where it will break) is reduced by 46% (1494 MPa against 797 MPa). So that alone makes it 87% stronger, without increasing weight. See pictures of the analyses using finite elements below.
Having the holes side-ways simply creates a massive weak spot. These analyses were done with 6,5mm holes, with bigger holes the difference is even bigger.

Probably the strongest extension ever.
Not one breakage since 2013 and counting.

Weight: 492 gr

195 €

2 years guarantee

The extensions have an outside diameter of 32.5 +/-0.1mm to fit in the standard internal diameter for RDM masts of 32.8 to 33.2mm. If in doubt about your mast, please check your masts diameter before ordering that it has at least 32.8mm inner diameter.


For a given bending momentum and wall thickness, the tension inside a Witchcraft HD carbon extension is 46% lower due to the correct alignment of the holes:

If the bending momentum is on the holes, the peak tension (shown in dark red) is 87% higher direct next to the holes which are the points to fail: