The following testimonials to our products and service are true to the original writer. They are not edited in any way beyond correcting the occasional spelling mistake and removing private addresses.
Our thanks to Jeff Phillips for this very informative feedback... Jeff has a Jensen Sunyachts Imp Catamaran, 37ft, 7 tonne
I can advise of the following performance figures.
Previously sailing at 4 knots is now 6 knots (in a 8 - 10 knot breeze)
Previously sailing at 6 knots is now 8 knots (in a 12 - 15 knot breeze)
The previous maximum speed of 9-10 knots is now 11-14 knots (with a 25 knot breeze, flat water)
The boat will go about much easier and sails closer to the beeze. Previously any closer than 45 degrees and the boat would stall rapidly and go into irons. Now sailing too close to the wind sees the boat slow steadily allowing plenty of time to readjust back to a good sailing speed at 45 degrees or the choice of sailing closer to the wind than the previous 45 degrees at a reduced sailing speed.
I am currently motoring at 6 knots on one motor and 7 knots on both. Engines are twin Kubota D950 diesels 20HP. This is an improvement of a knot over previous. I had hoped for more speed motoring, but the engines are only spinning at 1,900 rpm not the 2,600 rpm maximum power. The props are a little over pitched for the application I think but I don't intend to change the pitch. The motors are quite tired, so there is a chance I will change them out at some point for 27 - 30 HP motors instead.
The Slipstream propellers cost roughly 50% more than the quality fixed propellers being considered (note my previous props threw a blade each so needed replacement anyway). For a minimum 25% increase across the sailing speed range, it works out to be an extremely cost effective improvement.
On checking if it was OK to post these comments on our website Jeff added the following...
It's ok to use any of the information provided below in a testimonial. I am also happy to be emailed by prospective clients with further queries.
I should add that there were some major factors influencing the purchase of the propellers. I was very concerned about reversing, having done some research into folding props. My concern proved unfounded for maneuvering. I would be kidding myself if I was to say I can pick the difference between the folding props (19 x 14" 3 blade) and the previous fixed props (18 x 13" 3 blade). Idle in reverse on one motor with the other motor in fwd will still turn the boat on the spot.
Picking up weed also influenced the decision. This is where the folding prop has an advantage over a feathering prop. In this type of sailing catamaran the props are not far below the surface, which means they tend to pick up any floating weed quite easily. We haven't had any major winter storms yet but I expect the folding propellers to be better than the previous fixed props.
Another factor in the purchase decision was that Max O'Grady's were able to offer me a prop to borrow while waiting for the new ones. It was a power boat prop, being a 17 x 17", but was sufficient to get me in and out of the harbour until the new ones arrived.
I had originally thought to fit the props under water. Luckily I took the more conservative path and lifted the boat out for fitting. There was some cutting and grinding down of the key required, and the grub screws need Loctite to lock in place, so the installation would have been far more difficult to complete underwater.
A further advantage over the previous fixed props is that they used to rotate while sailing at speeds greater than 5 knots, which would put a just noticeable vibration up through the boat. The faster the speed, the more noticable the vibration which became quite significant at 7 - 8 knots. With the folding props there is no rotation, no vibration, and nowhere near the amount of wash that existed before.
Attached is a photo of the boat when I purchased it.
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