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Rudder optimization - always a grateful job with significant changes in performance.

Updated: Jul 21, 2023

The rudder insures that the yacht is easy to maneuver in all conditions. A rudder also can produce lift on an upwind course. Ideally without increasing the drag. A rudder give the helmsman feedback about the balance, the trim of the yacht. A good rudder provides a lot of sailing fun. In the last years we developed quite a lot of rudders, for news boats or as tuning/update. Depending on the budget we used CFD simulations and structural engineering to find the best solutions. For projects with limited budget we can estimate based on the past projects and keep a bit more security in strength and behaviour. Check out our parts/repair services here >>

Some months ago we got a request to repair a rudder for a nice classic Ron Holland IOR half ton design, a Golden Shamrock 30, built in 1976.

The yacht design is based on the prototype 'Silver Shamrock', winner of the 1976 Half Ton cup. With only 3,3t a competitive race boat for the conditions in the UAE. Here are some impressions about the work:

The new rudder fresh painted. The whole boat is in very nice condition and well maintained. The refit at Riviera boat in Hamriyah Free Zone is just finished.

But before ... this old rudder was in a really horrible condition. Inside totally wet, full of water, and it smelled horrible.

The rudder stock had compressed the foam in some areas and the rudder surface was bended, too.

The profile was asymmetric and the shape was a bit strange, far too thick at the aft end of the "profile". This rudder design is stalling very early and has a lot of resistance. We measured the rudder stock and built up an exact 3D model.

To optimize the rudder performance we increased the depth, the shape and the profile, so the rudder works better in bad weather/extreme angles.

The boat, an IOR design, requires a quite big rudder to control the boat with Spinnaker in heavy wind.

We used the old rudder stock to reduce costs. We thought about producing a carbon rudder stock, but with a composite shaft we need new rudder bearings, ball bearings or a stainless steel surface on the shaft. Carbon is strong, but abrasion damages the surface faster. Means both a bigger diameter and also modifications at the boat.

There was a lot of corrosion on/in the shaft inside the rudder, but we were happy that almost no corrosion was outside. We have done some welding and polishing at the shaft to fill uneven corroded areas. The rudder shaft was also a bit bended. We corrected it.

The core is made of high density foam and shaped with the help of templates. The lower stainless steel bands needed a little welding, but most of the old steel structure has fit perfect in the new profile. We embedded the steel structure from inside and outside, so we get a smooth transition of forces in foam and surface.

Most of the lamination we have done in carbon.

We suggested to align the rudder on site at the boat. So we kept the upper part a little bit longer to trim it. We reduced the gap between hull and rudder as much as possible, which means the resistance is less and speed better. At race boats we have only 1mm. gab between hull and rudder.

Optimized shape.

The boat with the new rudder. The installation was a challenge due to the summer heat of appr. 45 degrees. LOA: 29.68 ft / 9.05 m LWL: 24.50 ft / 7.47 m

Beam: 10.17 ft / 3.10 m

Draft: 5.75 ft / 1.75 m

Displacement: 7,055.00 lb / 3,200 kg Ballast: 3,108.00 lb / 1,410 kg Lead Sail Area 382.00 ft² / 35.49 m²

Rigging Type: Masthead Sloop

First Built:1976, 10 built by Southcoast Boat Works (IRE) Designer: Ron Holland

A cruising version with a much larger cabin house was called the CLUB SHAMROCK and built by Southern Shipyard, (UK).

The owner also bought a new super nice tiller.

Nice IOR design. Only 3.3t weight.

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