Axiom Propeller

[Farey]

I decided to fit an Axiom prop to my boat, and thought I'd share my experiences with the forum. The boat is a 60' narrowboat built in 2005 by Piper boats. It has a Vetus M4.17 engine and is fitted with an Aquadrive. These are my subjective impressions of the way the boat behaved after fitting the prop. I have not performed any objective measurements, and I have no connection with Axiom.

 

I got the propeller fitted a couple of weeks ago, and took the boat out for a 10 day trip cruising the Leicester Loop and the River Trent as far as Gunthorpe. We were travelling with a 70' boat hired from Alvechurch at Gayton.

 

The first thing I noticed was that the boat seemed to turn better. Doing a sharp turn out of the marina was easy, as were junctions, where we turned a lot more easily than the hire boat, and usually without needing to use reverse or the bow thruster.

 

The next thing we noticed was that the wash seemed less. This was particularly noticable passing moored boats, where disturbance was minimal, even if we didn't slow down quite as much as we normally would. Crusing along a straight stretch at 4mph, there was very little wake, whereas the hire boat travelling behind at the same speed was towing a significant wave.

 

Reversing also seemed better and more controllable, as Axiom claim. Stopping in locks seemed more precise, and it seemed to stop more quickly without needing so much power. Even reverse as tickover seemed to have an effect.

 

The only area where it seemed to perform less well than before was at high revs going at speed. In deep water on the river, it didn't seem to have quite as much 'grunt' as previously, although we still managed a ground speed of 5.5 mph against the current on the Trent, so this is not really a problem.

 

Axiom claim the prop is less likely to get fouled, but I couldn't verify that. In fact, we got very badly fouled on the Nottingham canal, when we picked up a large sheet of heavy plastic, which took a good while to clear. Axiom also talk about a reduction in noise and vibration; this has never been bad on the boat, and I didn't notice any difference. I wasn't able to reliably measure fuel consumption, and I've never had a problem with tiller pulsing or virbration, so I can't comment on those claims.

 

Overall I'm pleased with the end result. The boat does seem to handle better, and since we typically cover quite a few miles when we go out, I appreciate that.

[Proper Job]

Can I ask why you fitted the Axiom prop in the first place?

 

Where you having problems with the 'standard' prop?

[alan_fincher]

A counter to this, (and I admit I have not studied the reasons), is that well known blogger Sue of "No Problem" has recently had theirs taken off again....

 

"No Problem" blog link

[Farey]

Various reasons for fitting the prop. The boat handled well before, but I felt any improvement was worth it. I frequently go out with friends, who steer the boat, and anything that helps them stop seemed worthwhile. I've driven quite a few hire boats that handled very badly, and I appreciate having a boat that handles well.

 

Just read through the No Problem blog. Up to the point where he says he's having it removed, he seems to have been fairly positive about it. His single complaint seems to be down to lack of thrust in some circumstances when going forward. As I said in my first post, I noticed a slight reduction at high revs, but at low revs, e.g. going in and out of locks or general crusing it seemed fine. One interesting thing I found was that in some circumstances the RPM seemed to peak at around 2000, and that increasing the throttle made no difference. That wasn't the case with the old prop.

[RLWP]

<snip>

 

One interesting thing I found was that in some circumstances the RPM seemed to peak at around 2000, and that increasing the throttle made no difference. That wasn't the case with the old prop.

 

That sounds like over-propping. Did you get a lot of black exhaust when this happened?

 

Richard

[mrsmelly]

I decided to fit an Axiom prop to my boat, and thought I'd share my experiences with the forum. The boat is a 60' narrowboat built in 2005 by Piper boats. It has a Vetus M4.17 engine and is fitted with an Aquadrive. These are my subjective impressions of the way the boat behaved after fitting the prop. I have not performed any objective measurements, and I have no connection with Axiom.

 

I got the propeller fitted a couple of weeks ago, and took the boat out for a 10 day trip cruising the Leicester Loop and the River Trent as far as Gunthorpe. We were travelling with a 70' boat hired from Alvechurch at Gayton.

 

The first thing I noticed was that the boat seemed to turn better. Doing a sharp turn out of the marina was easy, as were junctions, where we turned a lot more easily than the hire boat, and usually without needing to use reverse or the bow thruster.

 

The next thing we noticed was that the wash seemed less. This was particularly noticable passing moored boats, where disturbance was minimal, even if we didn't slow down quite as much as we normally would. Crusing along a straight stretch at 4mph, there was very little wake, whereas the hire boat travelling behind at the same speed was towing a significant wave.

 

Reversing also seemed better and more controllable, as Axiom claim. Stopping in locks seemed more precise, and it seemed to stop more quickly without needing so much power. Even reverse as tickover seemed to have an effect.

 

The only area where it seemed to perform less well than before was at high revs going at speed. In deep water on the river, it didn't seem to have quite as much 'grunt' as previously, although we still managed a ground speed of 5.5 mph against the current on the Trent, so this is not really a problem.

 

Axiom claim the prop is less likely to get fouled, but I couldn't verify that. In fact, we got very badly fouled on the Nottingham canal, when we picked up a large sheet of heavy plastic, which took a good while to clear. Axiom also talk about a reduction in noise and vibration; this has never been bad on the boat, and I didn't notice any difference. I wasn't able to reliably measure fuel consumption, and I've never had a problem with tiller pulsing or virbration, so I can't comment on those claims.

 

Overall I'm pleased with the end result. The boat does seem to handle better, and since we typically cover quite a few miles when we go out, I appreciate that.

 

 

MMMMMMMMmm are you posting this to try to tell yourself the outragious price you paid for the prop was worth it ?

My bruvver in law has a 67 footer which had a lister prop fitted and was hopeless at stopping, it took forever and slewed wildly to one side so he had an axiom fitted. He states it stops better and in a straight line so that is an obvious benefit.

We took him out on our 70 footer fitted with a crowther high efficiency prop and he was gobsmacked at how quickly it stops in a straight line and how well it goes also. OK so we have an instantly responding vastly superior smooth running modern engine and he has an old clunk clunk rattly jobby in his dining room but neverthe less a good prop of standard design seems the best bet and OUCH how much for the axiom.....

[Farey]

No, none at all. Engine ran fine - just no further increase in RPM.

 

That sounds like over-propping. Did you get a lot of black exhaust when this happened?

 

Richard

[carlt]

I think, until someone fits a brand new Crowther, runs it for 6 months, then swaps it for an Axiom, to compare like with like, we'll never know if the improvement is because of a ground breaking new design or it was a case of "I took an old, worn, cheap prop off and replaced it with a brand new, mega expensive one...The improvement was miraculous!"

[RLWP]

No, none at all. Engine ran fine - just no further increase in RPM.

 

That's odd. Normally with a diesel engine if the speed is below what you've set the throttle to, it will keep banging fuel in and run black.

 

It still sounds like you're overpropped if the maximum speed has actually dropped. That would explain why your low speed performance has improved.

 

Richard

[Timleech]

That's odd. Normally with a diesel engine if the speed is below what you've set the throttle to, it will keep banging fuel in and run black.

 

It still sounds like you're overpropped if the maximum speed has actually dropped. That would explain why your low speed performance has improved.

 

Richard

 

I agree that it's probably overpropped, I've always suspected that some of Axiom's claims might be down to a slight overpropping. However a properly set up engine/fuel pump/governor shouldn't 'keep banging fuel in and run black', it should just 'run out of steam' and develop no more revs which is pretty much what has been described.

 

Tim

[PhilR]

We still don't have any evidence of anyone changing a correctly specified conventional prop to a correctly specified (and more expensive) Axiom prop and getting any improvement. But we do have some hearsay evidence to the contrary ............... I am sure most people will draw their own conclusions?

[WotEver]

... he has an old clunk clunk rattly jobby in his dining room...

[Speedwheel]

I think, until someone fits a brand new Crowther, runs it for 6 months, then swaps it for an Axiom, to compare like with like, we'll never know if the improvement is because of a ground breaking new design or it was a case of "I took an old, worn, cheap prop off and replaced it with a brand new, mega expensive one...The improvement was miraculous!"

 

The words 'nail, head and hit' spring to mind.

[WJM]

This is an excellent thread - thank you Farey. I am tempted to treat the 'Gadget Man' in me with a new propellor!

[WotEver]

I am tempted to treat the 'Gadget Man' in me with a new propellor!

Crowther or Axiom?

 

Tony

[Gibbo]

A counter to this, (and I admit I have not studied the reasons), is that well known blogger Sue of "No Problem" has recently had theirs taken off again....

 

"No Problem" blog link

 

Hmmm

 

I don't thihk I read that blog the same way others might. It seems very confused within itself and the timing of events seems to jump backwards and forwards...

 

They had an Axiom on and were happy.

 

They had a new gearbox fitted, the boat started making noises.

 

They then could no longer duplicate this fault.

 

So they removed the Axiom prop.

 

I think someone might have some diagnostics issues.

Edited April 28, 2011 by Gibbo

[RLWP]

I agree that it's probably overpropped, I've always suspected that some of Axiom's claims might be down to a slight overpropping. However a properly set up engine/fuel pump/governor shouldn't 'keep banging fuel in and run black', it should just 'run out of steam' and develop no more revs which is pretty much what has been described.

 

Tim

 

Thanks Tim. How does is manage to do that?

 

Richard

[Davidss]

Hmmm

I don't think I read that blog the same way others might. ....

I think someone might have some diagnostics issues.

 

Almost similar thoughts here.

I read that blog on a daily basis, and when the 'prop off' decision was made I couldn't quite follow the logic, BUT I put it down to overlapping hassles of prop and gearbox, which when combined with moving about, forced immobility, creating fixed appointments with dry docks, and again with the gearbox specialist, just got too much for someone who really just wants to turn the key and go, at their own pace and in their own time.

I'm not being critical, each to their own, it's just that the engineer in me wanted to find out what was causing the banging. Was it an interaction between prop and box? Was it a engine or prop speed resonance issue? etc etc.

 

I've previously come to the conclusion, and the trend in this thread has reinforced the conclusion, that there is a number of frequent posters who will not allow any good mention about the Axiom propeller be allowed to pass without belittling it in some way, whether connected to the positives mentioned in the post, or not.

 

Note to self - don't get dragged into an issue where illogical feelings run so high!!

Note to others, for background information, and misquoting - "I am not, nor ever have been, a member of the boat owning party". My narrow-boating was on other peoples boats, and generally I was paid for it.

 

Regards.

[Timleech]

Thanks Tim. How does is manage to do that?

 

Richard

 

By limiting the maximum fuel delivered per stroke to what the engine can burn reasonably cleanly.

 

Tim

[RLWP]

By limiting the maximum fuel delivered per stroke to what the engine can burn reasonably cleanly.

 

Tim

 

So, it overfuels - but only by a bit, not a lot?

 

Richard

 

It has to overfuel a bit, otherwise it can't accelerate

[jonk]

Previous thread on this topic:

http://www.canalworld.net/forums/index.php?showtopic=29276&st=0&p=509762&hl=axiom&fromsearch=1entry509762

 

Axiom still looks promising but still no definitive answer to the question of like v like. I am very interested to hear if anyone does manage to do such a test - it would be invaluable information for many prospective boatbuilders I'm sure.

 

Incidentally - just how different is the price between an Axiom and a top quality Crowther? Anyone have a 'ballpark' figure?

 

John

[Timleech]

So, it overfuels - but only by a bit, not a lot?

 

Richard

 

It has to overfuel a bit, otherwise it can't accelerate

 

My reply has got lost in the aether, so I'll try again

 

The last bit is not true if the load is a propellor, because the power needed to drive the prop increases with rpm at a much more rapid rate than does the available power from the engine.

(edit for clarity - this means there's power to spare until the maximum deliverable with a particular engine/prop combination is reached)

 

I suspect that modern vehicle diesels may allow a bit of overfuel when accelerating, you'll often see a brief burst of smoke when the driver of a diesel car puts their foot down. Especially Citroens according to my unscientific observations.

 

Tim

Edited April 28, 2011 by Timleech

[WotEver]

Hmmm

 

I don't thihk I read that blog the same way others might...

Hey Gibbo, you were going to fit one in April 2009 - did you ever do so?

 

Tony

[Farey]

We still don't have any evidence of anyone changing a correctly specified conventional prop to a correctly specified (and more expensive) Axiom prop and getting any improvement. But we do have some hearsay evidence to the contrary ............... I am sure most people will draw their own conclusions?

 

I'd be very surprised if the original prop wasn;t correctly specified. Simon Piper is a reputable builder who seems know what he is doing.

 

Regarding the comments about over-propping, I'd like to understand that better. Can anyone point me at a good reference?

 

I'm guessing that its related to the fact that the pitch of a fixed pitch prop will only be optimal at a particular speed? And that over-propping is making it optimal at a speed lower than normal cruise speed? That would result in better performance at lower speeds, but a reduction in performance at cruise speed, which would seem to fit what I'm seeing.

[Gibbo]

Hey Gibbo, you were going to fit one in April 2009 - did you ever do so?

 

Tony

 

No. I still want to. It's getting round to it that's my problem.

 

What I'm hearing over and over again is "I don't understand how it works, therefore I conclude that it can't" which is an utterly ridiculous attitude.