2 Narrowboating trials with Alister Hodgson-Jones

We wish to thank you for choosing us to trial your new propeller during the past summer. Hopefully this ‘layman’s’ report on its performance will be of use to you in your development programme.
Boat specifications. 58 ft semi-traditional narrow boat ‘Caromanda’ with 43 hp beta engine and bow thrusters fitted. Hull by Graham Reeves factory fitted ???? Marine screw propeller. Fitting out completed in April 2008.
Original expectations.We were experiencing propeller noise at various levels (mostly at unacceptable levels) at lower engine revs – 1100 to 1500. The ‘gravelly’ noises largely ceased at revs over 1600 although returning at high revs – over 1900. Our expectation was that your propeller would greatly reduce and hopefully get rid of this noise problem.
In addition and based on your advice we looked to your propeller for improvements in the following performance areas:
Fuel consumption 5% improvement
Acceleration
Steering- response to turning and less straight-line tiller vibration
Reverse handling – straight-line reversing without bias.

Initial controlled trials. We carried out the controlled trial over a measured course on the River Nene in the middle of May 2008. You will of course have all the results of these trials at which we tested the existing marine screw prop and then the Axiom 1 prop fitted for our summer 2008 cruising.

TRIAL 1: Summer 2008 trial – Axiom 1 propeller. (Stainless steel test propeller.) We set out from our base at Islip wharf on the River Nene on 20th May and cruised more or less continuosly using the Axiom 1 until the end of August 2008. During this time the boat covered 666 miles travelling the Rivers Nene and Weaver, and canals Northampton branch, Grand union, Coventry, Ashby, Birmingham & Fazeley, Staffs & worcs, shrop union Liangollen, Montgomery, Middlewich branch Macclesfield, Peak forest, Ashton, Bridgewater, Trent & Mersey, and up the caldon canal. This gave the prop a workout in every water condition possible from wide & deep river water to narrow, shallow and weed clogged canal water.
For our first criteria of noise reduction the Axiom 1 was of limited success. It got rid of the low rev noise but introduced a new gravely noise at higher revs around 1600 although not as loud as with the marine screw. In addition both props were lible to temporary noise generated in certain water conditions. This noise seemed to be associated with propeller shaft vibration but was impossible to exactly identify.
Our unscientific, seat of the pants, fuel consumption rate for this period equated roughly to 5mpg with lock time and other engine idling time taken into account and roughly 7.5 mpg for cruising time only. The River runs with wider, deeper water showed results closer to 10 mpg.
It was not discernable that the Axiom 1 gave improved acceleration. Improved steering and reverse handling were discernable.

On the negative side it was quite obvious that in reduced water conditions (narrow and / or shallow water) the Axiom 1 was unable to maintain speed in comparison to other boats around which it can only be assumed used marine screw props. Obviously, in these situations it was tempting to increase revs to maintain speed but this was generally counter-productive. The worst condition was in a tunnel or aqueduct with restricted water where headway was reduced to a crawl. In ‘normal’ and generous water conditions headway was maintained best at 1650 to 1700 revs with a ‘sweet’ engine noise.
By mid-summer it was obvious that some improvements to the prop were desirable. From our experiences and your own development programme you prepared a new prop. Axiom 2. For our boat. As we understand the development the new prop with slightly larger diameter and alteration to blade attack and shape was expected to improve thrust at lower revs and consequently resolve on the original criteria.

TRIAL 2: Axiom 2 trial. (Nickel Aluminium Bronze (AB2) cast propeller. The Axiom 2 was fitted on 3rd sept. While the boat was on the ‘river’ section of the Caldon canal. It was used for the rest of our boating season (boat returned to Islip wharf for winter mooring on the 16th Sept during this period the boat did 138 miles on canals and River Nene back to homeport.
Improvements over Axiom 1 were immediately evident. Propeller noise simply disappeared as did shaft vibration noise and in this respect we can ask for nothing more.

Performance in all categories improved:
• Fuel consumption appeared to improve from 5 to 6 mpg but with limited figures we like to revisit this item next year.
• Improved acceleration was very noticeable
• Although Axiom 1 was good with steering / manageability, the Axiom 2 seemed to have added benefits of reduced vibration on the tiller during normal cruising.
• Reverse handling, with limited trial time appears to be further improved with even less effort from prop torque when reversing in a straight line. Reverse speed is excellent.
• Acceleration was immediately noticeably better then Axiom 1.

But the improvement is the speed in all conditions and the headway now achievable in the poor water conditions. Not once during this trial did we fell that other boats had a performance / speed capability better than ours. In re-tracing sections of canal that we had noted in the boat diary as being previously difficult, with the Axiom 2 passage was made with no realization that the water conditions were different. With Axiom 2 the engine sounded ‘sweetest’ at 1600 R.P.M, less than previous, for comfortable cruising speed.

Other comments. An unexpected and very welcome side effect with the Axiom 2 was its performance in respect of picking up ‘weed’. It may have been purely luck or it may be the prop design, but during the passage of 138 miles using Axiom 2 we only had to clear the prop on three occasions, only one of them which was serious and this was during passage down the Northampton branch which anyone who has used it will know is extremely congested with plant life.
Although we were unable to carry out a controlled trial on the River Nene with Axiom 2 at the end of the season for comparison with the beginning trials, we would hope to do this during the winter.
As you know, we were unhappy with the weight of ballast we were carrying this year. We have now lightened the ballast load and look forward to next years cruising with expectation that we will have a further improvement in performance.
We look forward to a continued mutually beneficial relationship with yourselves and any further developments with Axiom propellers. It’s a great product and we trust it will be successfully brought to market.