420 Tuning Information

NEW 420 Mast

During 2000, Selden developed a Cumulus 420 section. Supplied with a custom taper dedicated for the 420, this section is also proving perfect for moderate to heavy crews searching for that elusive extra medium wind power. The new section achieved instant success at the 420 European championships that year.

Why is the taper so good?

The clever part of the New Cumulus is not only in the most efficient stiffness to weight ratio section available, but the custom tip ‘tapers’ earlier and more quickly than any other mast.This leaves the sailor with a tip that ‘holds up’ in the 8-15 knot wind range, but then ‘whips’ above this range. The tip is finger-tip controllable with the cunningham.

As the taper starts earlier, the mast is therefore smaller, reducing drag over the mainsail at a point where the chord of the sail is at its smallest.


Seldén’s 2628 boom is ideal for the 420 being both light and stiff, although some of the heavier crews have chosen our 470 boom section, the Olympus, which is even stiffer allowing absolute mainsheet and kicker control.

Spinnaker Pole

We recommend either our 38mm with the NEW Seldén pole ends.


1st British Youth Championships 2003

Why Seldén?

Choose a Seldén mast and you will find many performance enhancing features unique to our products, for example:

  • The Seldén tapering system ensures that our tapers are minimum size and weight. This gives low windage, centre of gravity and topmast weight. This maximises your speed by enabling the topmast to react quickly to gusts and waves giving better acceleration, a smoother ride upwind and, ultimately, more races won!
  • Automated welding keeps excess heat out of the taper for guaranteed consistency and performance. The weld produced is so perfect that there is no need to mechanically grind the weld (which can induce inconsistencies). This means that once we have finalised a winning design, you can be sure that your spar will perform identically to the champions.
  • All masts are heat treated in our purpose-designed oven. This artificial hardening ensures that you get maximum performance from the high performance aluminium alloy.
  • Our spars pass through a purpose-developed bead-peening machine. This gives the mast a perfect satin finish that dramatically improves fatigue properties, giving you a mast that will perform reliably for many years.
  • Top quality fittings such as our fully adjustable spreader bracket and highly durable cast gooseneck ensure speed and reliability on the racecourse.

Sections Available

Mast Cumulus , Kappa
Boom 2628 , Olympus

Mast Specification - Cumulus , Kappa

The Cumulus mast is supplied fully fitted with our NEW sheave heel fitting, fully adjustable spreaders, all fittings (including a custom angled bush for the pole downhaul).

All masts are supplied with mouse lines to facilitate the reaving for a rig pack.

Boom Specification - 2628 , Olympus

Boom is supplied complete with inboard and outboard ends with sheaves, plus three boom slides and outhaul.

Spinnaker Pole Specification

Standard pole is super light 38mm tapered pole, supplied complete with wide based uphaul eye.

Rigging Specification

Includes kevlar main halyard and pole uphaul, pole uphaul hook, shrouds with swage eyes at bottom.

Tuning Tips

Crew in Boat Semi-trapezing Full trapezing Overpowered Very
Wind Speed
5-8 9-11 12-15 16-20 20+
Mast Foot Position
(from c/b bolt)
430mm 430mm 430mm 430mm 430mm
Spreader deflection
to aft side mast
Spreader L = 470 mm)
165mm 165mm 165mm 165mm 165mm
Mast rake 6070mm 6070mm 6032mm 5994mm 5994mm
Rig tension (Loos, on shroud) 38 38 39 39 39
Pre bend, natural (no chocks) 36mm 36mm 41mm 46mm 46mm
Chocks (15mm), from neutral -1 to neutral neutral to +1 neutral to +1 neutral -1
Bridles long normal normal normal normal
Centreboard full down full down 15° up 20° up 25° up
Barberhaul Yes/No Y (over pole eye) Y (normal) Y (normal) Y-N N
Kicker loose take up slack yes lots lots
Cunningham no no N-Y Y lots
Outhaul hard (15mm ease in
special conds)
hard (15mm ease in
special conds)
hard hard hard







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