Boating, biking & boarding – in Southeast Asia

The Viper is proving to be every bit the exciting boat that it really is. Since we have half of the world’s production sitting in our little boat park at Changi Sailing Club, we’re in a really good position to tune the boats up, against ourselves and others.

A few questions have filtered through and so will do my best to give a suitable answer…

The QUESTION was about mast rake. How can you tell if you have the right amount of rake or not? What does it feel like? What difference will it make?

So here, a guide to mast rake.
1. WHAT IS MAST RAKE? It’s the amount that a mast is “raked” aft towards the back of the boat. Different designs like varying amounts of rake. Basics say that a mast is ‘tallest’ when it is in a completely vertical position i.e. 90 degrees perpendicular to the deck!
By gradually lengthening (adjusting) the forestay, we can allow the top of the mast to move backwards. This will do two things,
1. It will move the Centre of Effort towards the rear of the boat.
2. The mast won’t be as ‘tall’ as in the perpendicular position. 

2. WHAT DOES IT FEEL LIKE? If we ‘rake’ the mast all the way back we will move the Centre Of Effort of the sail to the rudder. This will translate into a ‘pull’ on the tiller. For those of us who have sailed Hobie 16’s, we know this feeling well i.e. H16’s tend to have a lot of rake, a lot of weather helm and therefore a big ‘pull’ on the tiller.
If we put the mast to far forward, the opposite will be true. You will then experience “lee helm” and will have to ‘push’ the tiller to compensate.

WHAT DIFFERENCE DOES IT MAKE? Sometime back we tested things out on our Taipan. The Taipan rake is ultimate when the forestay rake is set to the 4th hole from the top of the adjuster plate. On one windy day, I put it to the 5th hole and tried the boat. My GPS was averaging 10.5 knots upwind, the tiller felt positive i.e. a constant “two finger pull” on the rudder.
I returned to the beach and put the mast back to the 5th hole and the result was a bit amazing. The light “two finger steering” returned and the average speed upwind was increased by 1 knot of boat speed! 

When we set up the first Viper in Singapore, there was no benchmark for us. Greg Goodall sailed No. 1 while I observed from shore with my camera. reviewing the shots later we could see that she was indeed carrying to much rake. We then reduced the rake with each sail until it went in a ‘negative’ direction.
Once we had ascertained what appeared to be the best rake, we copied this setting onto each proceeding Viper into the fleet.

As it stands now, we measure VIPER rake by using a trapeze line and measuring to the bridle tang (where the bridle wire attaches to the hull). Using this as a fixed measure, we walk toward the rear of the boat. Pulling the line tight, the fixed measure should touch the transom approximately 25mm down from the foot strap corner.

When we sail now we experience ‘neutral’ helm until the mainsheet is set firm to its proper upwind setting.
We feel weather helm when sailing tight with the spinnaker. When we sail ‘free’ with the spinnaker, the weather helm reduces to almost zero again.

From this I know we are about spot on for mast rake. If I was to reduce my mast rake anymore I would experience ‘neutral’ helm upwind (NOT good) and even more lee-helm downwind.

Ideally, a little weather helm upwind is a good thing as long as its not more than two finger steering as this will create more drag from the rudders.

Hope that helps?

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