We purchased our 1999 Jeanneau Sun Odyessey 34.2, Imshi IV, in 2004 and were extremely pleased with her apart from what we considered to be rather mundane sailing performance.
Though the suit of Elvstrom sails are original fit, they have not had a hard life and the rig set-up seemed to be OK. This led us to consider what effect our two-bladed fixed prop was having on our performance.
Our previous boat, a Verl 900, was fitted with a two-blade folding prop so we were well aware of the pros and cons of these: minimal drag when folded but with the major drawbacks of lack of thrust in reverse and less than ideal performance in anything of a seaway.
By late 2005, having decided that a new prop rather than a spinnaker was the way to go, we did the rounds of prop manufacturers at the Southampton Boat Show and amassed a sizable chunk of sales material (and hand written notes) about various products.
After several weeks of sifting through all of the literature, searching the Internet and many phone calls, we decided to go for the three-blade feathering Kiwi Prop - engineered in the UK by Vecta Marine of Pewsey in Wiltshire.
The main reasons for this choice were:
- When in the feathered position, each individual blade aligns to the water flow rather than the shaft angle, thereby reducing drag to the absolute minimum.
- The three-blade design would give maximum thrust in a seaway.
- The whole hub unit (since early 2006) is manufactured in stainless steel - this removes the chance of dissimilar metal corrosion and reduces the chance of electrolytic (pitting) corrosion.
- The Zytol (glass reinforced plastic) blades eliminate the dreaded blade pitting corrosion problem.
- If a blade is severely damaged it can be simply replaced by the owner at very reasonable cost.
- Price.
- No problem in keeping our Stripper rope cutter.
Before fitting the prop we did some engine benchmark runs (we already knew our performance under sail!) at four rev settings (2000, 2500, 2700 and 3000 - the latter with considerable vibration) and made a note of boat speed in each case.
After fitting the new prop (March 2006) as per the instructions provided and getting back in the water, we carried out the same runs (approx same tidal and water conditions) which confirmed that for the same boat speed, the rev settings were 1800, 2300, 2500 and 2800 - with no vibration at any setting.
The improvement in thrust is most noticeable in any kind of a seaway - the boat just powers her way through it and as advertised, within a couple of seconds of selecting neutral the blades feather and the prop shaft stops spinning (no more gearbox strain or shaft vibration when sailing) and virtually no prop walk in forward or reverse, which has been a big confidence booster in close quarters situations.
With regards to sailing performance we were, and continue to be gob smacked!
Before the prop change we came last in the two races that we entered. Pointing ability was awful, boat speed (especially in light airs) was frustratingly sluggish and (prop) turbulence over the rudder blade impacted on tracking ability.
Since the prop swap we have had six races and registered a 1st, 2nd ,3rd and two 6th places. On a beat, we believe we are pointing at least 5 deg higher with an estimated boat speed improvement of 1 - 1.5kt. The boat speed improvement applies across all points of sail. Turbulence over the rudder is non-existent and tracking is much improved.
I would like to add that the product, the information, fitting instructions and support provided by Vecta Marine throughout the whole process were excellent - I have no hesitation in recommending the prop and the company.
We lifted Imshi out on April 23rd this year - 13 months after launch with the new prop.
Apart from some slime on the blades we found them to be in perfect condition. There was light fouling on the hub and prop shaft, the Trilux antifouling having done a reasonably good job.
The blades were given a light rub down and given two new coats of Trilux. The shaft and hub were cleaned off and coated with Prop-Shield. We are running this as a trial - if successful, we will use it on the blades next year.
