The Ultimate Propeller Test Review – 10 things to know

Back in 2009 the Yachting Monthly Magazine carried out a detailed test review to compare all the latest low drag propellers available on the market and the Ultimate Propeller Test is still the go to reference for many who are looking to upgrade their propeller and sail faster!

The propellers on test included:-

• AUTOPROP – H5-394mm
• AUTOSTREAM THREE-BLADE – 17x11in
• AXIOM THREE-BLADE – 16x11in
• FEATHERSTREAM THREE-BLADE – 16x11in
• FLEXOFOLD THREE-BLADE – 16x11in
• FLEXOFOLD TWO-BLADE – 16x13in
• GORI THREE-BLADE – 15in
• KIWI PROP THREE-BLADE – 16x11in
• MAX PROP THREE-BLADE – 16x11in
• MAX PROP TWO-BLADE – 16x12in
• SLIPSTREAM THREE-BLADE – 15.5x11in
• SLIPSTREAM TWO-BLADE – 16×11½in
• VARIFOLD TWO-BLADE – 15x11in
• VARIPROFILE THREE-BLADE – 16x11in

This was an interesting test which to a large extent proved what was widely known with a few surprises!

Here are 10 things to know about the Ultimate Propeller Test…

1. Maximum Hull Speed.
   This test was carried out in flat calm water with virtually no wind so 2B folding or fixed propellers excelled due to less interference between blades. However, when resistance on the yacht increases a propeller with more surface area (3B or 4B) will continue to drive the hull efficiently and be more consistent through the water where a 2B propeller will lose out.
2. An efficient and well-designed folding propeller will offer the best forward driving hull speed in flat calm conditions but not so efficient in astern. Flexofold propellers did very well.
3. Stopping Time.
   The value of this test in an emergency is obvious. Most feathering propellers like the FeatherStream benefit from efficient blade angles in astern and all showed good stopping power, better than the fixed and folding props.
4. Prop walk. This part of the test is misleading!
   It appears to show that folding props produce less prop walk than feathering ones. In practice the opposite is true. This is because the test was done at full throttle in reverse. Feathering propellers work much better than folding propellers at low throttle in reverse. The whole idea of a feathering propeller is that is does not need to be revved hard in reverse. It will produce a lot of thrust at very modest throttle, where Folding propellers have to be operated at high throttle in reverse (relying on centrifugal force) and the result is more prop walk at these high shaft speeds. It would have been better to do the same test but at a slower shaft speed.
5. This test was performed on a Beneteau Oceanis 323.
   Your hull form and installation may be very different so the results from this test are focused on this yacht only, different hull forms and installations will require very different propellers, so propeller choice is specific to your boat and your requirements.
6. All folding and feathering propellers offer a significant improvement in sailing performance due to reduced drag.
7. Pitch adjustability!
   Not all propellers tested can be adjusted for pitch. Feathering propellers such as FeatherStream can be adjusted to fine tune engine loadings which can influence cruising hull speeds for more efficient motoring.
8. No propeller is perfect in every aspect!
   Some excel in certain areas but are less effective in others. Expect a level of compromise when choosing your propeller.
9. Yacht owners have individual priorities regarding propeller performance.
   The propeller designer/supplier must identify each individual owners’ priorities and offer the propeller which most closely matches these requirements. Low drag propellers are tailor made not only for each hull form, engine, gearbox and shaft but also for each owner. We don’t always want the same thing!
10. You generally get what you pay for! Folding propellers are the exception.
    The most expensive 2B propeller (Gori) was outperformed in all tests by the less expensive Flexofold propeller, whilst the most expensive 3B propeller (Gori) trailed in all the most crucial tests. Of all the feathering propellers the FeatherStream offers the best value for money!

So there you have it, these are just a few pointers highlighting aspects of the propeller test review which will help you understand some of the performance outcomes.

Posted on Thursday, October 24th, 2019