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Old 09-06-2007, 08:03   #106
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My thoery about autoprop

Dear Alan

Before buying The prop handbook by Dave Gerr I have a theory of what is happening but I didnt want to advance a fake technical issue before being informed.

As you know I'm an enthusiast Yatch amateur and not a professional. Anyway I have some tech skills to understand problems.

So i wanted to read that book before saying what I have in mind.

The problem with the self pitch coincept is that is probably perfect in a water tank test but could not work in many modern sailing hulls.

As the prop rotates the blades open and find their balance between the forces in the prop blades. i will not discuss this issue as I dindt read the AUTOPROP patent claims and is out the scope of this post.

Lets go to the ponit.

In modern hulls like the one of my HANSE 531 designed by judel and vrolik the skeg is probably optimized for sailing. i.e. is a straight skeg with a cutlass bearing on the bottom that is essentially flat.

That skeg is straight with no fairing at all and the exposed botton IS STRAIGHT like a WALL viewed to the prop side,

As the prop rotates at lets say 2800 rmp what is happening is:

The shaft is rotating at 1068 rmp because the 2.62 gear ratio of the Yanmar gear box.

As the prop is three blade three times a turn one blade is facing the wall of the straight skeg bottom.

That cause a high flow disturbance wich changes the pressue in the blades which means the prop CHANGES THE PITCH OF EACH BLADE AT

1068 times 3 = 3204 times a minute.

You can imagine the stress is unbearable for a cutlass bearing leading to be sanded like balsa wood in two hours.

Read pages 84 and 85 of Prop hanbook by Dave Gerr for a futher exsplnation about water flowing disturbances

The vibration at 2800 engine rpm was unbeearable because all the three blades are changing the pitch at 3204 times a minute.

The frecuency unit is the Hertz which is cicles per second.

One minute is 60 seconds

The frecuency of the vibration shall be 3204 times 60 = 53,4 Hertz.

Which is dominating very low frecuency strong vibration and sound we problably heard blasting in the hull.

This issue will not affect any other folding or feathering propeller with blades not hanging free...i.e. it only affect the AUTOPROP, because the blades are moving freely without an end stop.

the AUTOPROP can only work in

a) Optimized faired skegs with overhanged cutlass bearing housings

b) Long shafts with thin single shaft strut ( as far as possible to the hull and the skeg)

c) The clearances to hull and skeg should be maximized anyway to the extreme.

d) In well designed saildrives when the boat is less than a 47 footer so the engine is less than 75 HP and the saildrive neck is as long and as thin as possible, but also has a strong bearing on the shaft tip. This last issue is a bit misleading in mmarketing terms as the price and design of the AUTOPROP call for larger yachts and not for small sailboats

What is really upsetting to me is BRUNTONS is a world leading prop manufacturer and they know what is happening but they are selling the props anyway regadless of what is you yacht shaft claerance or hull skeg shape.

They should list an incompatibilty list ASAP but they are not playing fair.

Your feedback and opinions always appreciated

Best regards to fellow sailors

JOSE
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Old 09-06-2007, 14:28   #107
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It is too easy and totaly unfaior for me to simply write words based on assumption rather than practicle knowledge. To make a fair call as to what may or may not be happening, I really need to see and experiance the prop to know for sure what is happening.
What you have said above could be true. But as all "self feathering self pitching" props are based on the same design concept, I doubt that any other design will be any better. A fixed pitch self feathering prop may, but they have their own draw backs with less effiency in the design.
What I do know is, Bruntons themselves are not amatures. They have a very long history and a a noted reputation in the industry. They build a very high quality product. In saying that, I know mistakes can always be made. Without knowing how they manufacture and QC their product, I can't comment on why a mistake can or could be made. Maybe it never was.
There product range is large and each design suits a certain criteria.
In Dave's Case, The US rep seems to be letting the team down, not Bruntons themselves. I am not sure whom you dealt with. Was it Bruntons or the US rep?
To sum up, it is a complex situation and personly, I think a technician from either parties should be going out to the boat and taking a look at the situation and advising on the best course of action. Especially if a problem does exist with the prop, they need to remedy the issue in the factory. If the problem exists with the boat design, they need to know that info for future sales knowledge and not have this happen again, which only serves to damage a reputation.
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Old 09-06-2007, 15:20   #108
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I have a sneaking suspicion that you may be on the right track. In my situation had we had a 3:1 ratio in the reverse gear all would have been perfect. I had the extreme vibration and it was enough to shake the boat at about 1400 rpms on the engine and 700 rpms at the shaft. It was so extreme I had discovered that the seal between my stern bearing and the hull had been effected enough that I was taking on water between the two surfaces. Something else to fix when I haul (I've since sealed it using underwater epoxy but don't know how long it will last).

One way you could check your vibration theory Jose; is find someone with a newer model Macintosh and get the program Seismac Suitable Systems / SeisMac there you'll get real time vibration in all three planes. However when I had tried it (I do have the results) after I had made the changes to the system I didn't have the "extreme" vibrations bending of the shaft and didn't then see any differences. But I was hoping the program would show up the frequency. I'll be interested in seeing if there are any differences between the smaller one they sent me with a flatter blade profile to the one I'm sending back. Jose your idea of 3,000 + changes / minute are interesting and thus the prop may be swinging out of balance because it physically can't change that fast but the movement is analog not digital and thus the prop isn't making automatic lightening fast adjustments 3,000 + times but finding a balance. At least that is my take on it.

I do find it interesting that with these two extreme situations they haven't actually sent one of their engineers to a find out what is happening so they can fix it. I suspect that the prop turning slower would help and I believe Jose mentioned too that in reverse he had a higer rpm before the vibrations occured. That is exactly what we found too. I wonder if that's because of a free flow of water or because the prop is actually better in reverse. Simply speculation here. We do have two different underbodies, mine is a full keel with an enclosed aperature and his is I think a fin keel with the prop fully open but at a downward sloping angle.
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Old 09-06-2007, 16:21   #109
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The scientific and engineering posulations are interesting for conversation.

The problem here is customer service.

If the prop is not right for the boat and it can not be made right. The money goes back to the customer, Autoprop goes back to the drawing board, hands are shook, no harm no foul, all with a smile.

Boat owning is a financial risky proposition in itself. Money at times will be wasted and more valuablly, time will be lost. But that is sailing's nature.

AutoProp needs to stand up, take responsibility for its product. Fix it or refund it.

The boat owner needs to understand that the problem may be more complex than Autoprop can solve with its product, Take his money back and go search for another solution.

So at the risk of sounding rude, shaft vibration, Hz vs rpm's, mayonaise vs. mustard don't mean squat in this situation. It is time for both parties to respectfully do business with on another. No judgement as to who is at fault, but I think Autoprop needs to look at its customer service practices.

Carry on.
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Old 09-06-2007, 16:42   #110
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Quote:
No judgement as to who is at fault, but I think Autoprop needs to look at its customer service practices.
Yep I agree Maddog.

Dave, I would suspect the seal has failed, not due to vibration, but by the shaft bending. This is what my very initial concern was for. And the bearing as well. There is simply no way that a fibreglass structure can withstand this sort of abuse.
Again without seeing for myself, I can't give accurate advise. But going back to the original video Dave sent, the issue is more than a blade altering pitch as it passes the skeg 50 x/sec. I have some theories, but untill that prop is changed and the possibility that the prop is faulty is taken out of the equation, then there is little piont discussing possibilites that woudl thus be inaccurate.
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Old 10-06-2007, 09:55   #111
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YES I HAVE NO VIBRATIONS IN REVERSE AND OTHER THINGS

Dear Folks

I would like to thank you to those that are considering my idea.

My theory can not be exact. I will need and microphone and a oscilloscope to proof the fundamental vibration is the expected frecuency. Maybe is too much to work harder just for a prop problem. i have tried everything and learn some interesting technical issues on shafts. so overall the experience was expensive and frustating but ....I learned some interesting things.

I'm only upset because the customer service issue. Thanks to remind me that. It is true the issue is a bad customer service and nothing else.

Boats are a complicated environment. I have a high respect for BRUNTONS as a excellent design product company, I still remember my first impression about the prop when we opened the box at the yard...wow...everybody said!........ but its service is dismayal

Alan... the most frustating relationship was with the US rep Geoff. He misleaded me with a inexistent whippping problem. That was AFTER the seatrial sheet The problem is not whipping but the change of pitch that completely unbalance the prop.

David the BRUNTONS engineer at the UK headquatrters was a great help as he confirms the flow disturbance due to the straight skeg was problably an fact impossible to resolve.

The first clue about the skeg disturbance theory was the no vibration issue on reverse. we hit 8 knots at 3000 rmp IN REVERSE which is unveliable. then I have stopped reeving up in reverse as I was unsure of keeping the wheel on the way... too much pressure on the rudder.

Overall I think the important lesson is BRUNTONS have to act and do something to prevent other cruisers to follow my "via crucis" as I'm sure they know what is happening.

Unfortunatelly they are still refusing a cash back trying to sell me a four blade VARIFOLD prop ...which I dont like. I'm thinking into a GORI PROP.

Thanks again

Jose




Quote:
Originally Posted by Alan Wheeler
Yep I agree Maddog.

Dave, I would suspect the seal has failed, not due to vibration, but by the shaft bending. This is what my very initial concern was for. And the bearing as well. There is simply no way that a fibreglass structure can withstand this sort of abuse.
Again without seeing for myself, I can't give accurate advise. But going back to the original video Dave sent, the issue is more than a blade altering pitch as it passes the skeg 50 x/sec. I have some theories, but untill that prop is changed and the possibility that the prop is faulty is taken out of the equation, then there is little piont discussing possibilites that woudl thus be inaccurate.
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Old 10-06-2007, 10:11   #112
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Jose, when diplomacy fails...sometimes one has to remind a merchant that here in the US, we have warranty laws. Federal and state laws. Among them the Mangusson-Moss Act and the Uniform Commercial Code, and they both create statutory warranties of "fitness for use" and against manufacturing defects, among other things.

If the goods are not suitable for the intended use, and they do not perform in the way that they were marketed for, the merchant is required to take them back and make a refund--with very few limitations.

If a prop sold for use on a specific boat produced damaging vibrations, or simply excessive vibrations, and putting another prop on the boat confirmed that the rest of the system worked--they'd be obligated to correct the problem, make a refund, or face legal consequences.

Usually when you mention the magic words from above, they realize they're not going to snow you and they reluctantly do what the law requires: Make it right.
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Old 12-06-2007, 19:05   #113
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Dear Hellosailor

Thank you for your feedback. Yes I'm requesting legal advice as BRUNTONS in the UK as per their last e mail yesterday is still refusing a cash back and trying to sell me a new four blade propeller whose only feedback is their own one.

About Geoff from AB Marine their US rep his mailbox is bouncing my e mails. I think thery have a virus on their host. What a mess!

I really appreciate your support.

Jose
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Old 12-06-2007, 20:11   #114
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Your reply

Dear DkALL


Yes you are right there is some computer software avalaible that made FFT ( fast fourier transform) analysis. Anyway you need a good microphone to pick up 50 Hz, Capacitor microphones are cheap and can pick 50 Hz, Cheap dinamyc microphones can not pick so low frequency.

Some manufacturers use FFT analysis to troubleshoot systems like compressors, engines, shafts and other gear as is an inexpensive way to see what is happening.

A vibration is a wave that changes amplitude versus time. That is called domain time.

The spectrum analysis of this vibration is called frecuency domain, and can be easily obtain by an FFT analisys of the domain time.

Amplitude versus frecuency is called frecuency spectrum.

The variation of pitch in the AUTOPROP is an analog pulse each time one of the prop blades is disturbed by the skeg turbulence. The pitch variation creates a bending torque stress on the shaft. The bending torque can wear the cutlass bearings in hours.

The vibration fundamental frequency is about 50 Hz at 2800 rpm with a 2,62 gear. but shall be different on other rpms and gear ratios.

The vibration amplitude peaks up rapidly when reeving up as the pitch variation ( vibration amplitude) grows probably non linear but exponentially ( that is the reason we start to heard the vibration only at 1600 RPM)

I dont think the vibration is a pure sinusoidal form, probably its wave is heavily distorted. The blade once pitched down while opposing the skeg will bounce and pitch up and after stabilize on its "real pitch" position. That means the vibration will carry Harmonic frequencies i.e. 100 Hz ( second harmonic ) 150 Hz third harmonic ... and so on.

The fundamental vibration can be distorted by the blade, shaft, strut or hull resonances...but still the 50 Hz fundamental vibration has to be there.


Over the sea trials with the AUTOPROP, we have heard a strong hull resonance at about 3000 rpm. We never revved up more as the stanchions were shaking in the aft. That is probably a hull resonance in some of the harmonic freciencies.

We tryed to identify the source of the vibration, The source was NOT the shaft, the hull, or the engine, the vibration came from the propeller. We make diffrent trials with the panels out and all gear exposed.

In one of the sea trials we had 8 persons on board, the "newest" in the business was me, and everybody said, Jose....buy another prop.

My hull is not fiberglass. The hanse 531 is built in epoxy wich is stronger than PRF, but the vibration destroyed the cutlass bearings in two hours of seatrials.

I just receive an e mail from Palma fron a German engineer who helped me. He was researching after the AUTOPROP as he was interested in the subject after spending three days changing the cutlass bearings while in the hard.

He said he discover AMEL was fitting the AUTOPROP on his Super Maramu 53 for a couple of years.

The Amel is one of the nicest cruising boats I have ever seen. They have a beautiful own developed saildrive for a 100 HP engine. This saildrive is known to be silent and vibration free.

Well I have been told the Saildrive bearing worn on those AMELS in just ONE YEAR.

They have a vibration but it was acceptable. That is normal as the saildrive minimizes water flow disturbance, so change of pitching is minimal if hull to prop tip clearance is kept.

Amel discontinued the use of the AUTOPROP after many trials.

I'm still trying to get a chash back from BRUNTONS. Now they are upset with me because I have disclosed their problem on the Forums...bad for them.

I'm just trying to avoid others to follow my path....


Jose





















Quote:
Originally Posted by Maddog
The scientific and engineering posulations are interesting for conversation.

The problem here is customer service.

If the prop is not right for the boat and it can not be made right. The money goes back to the customer, Autoprop goes back to the drawing board, hands are shook, no harm no foul, all with a smile.

Boat owning is a financial risky proposition in itself. Money at times will be wasted and more valuablly, time will be lost. But that is sailing's nature.

AutoProp needs to stand up, take responsibility for its product. Fix it or refund it.

The boat owner needs to understand that the problem may be more complex than Autoprop can solve with its product, Take his money back and go search for another solution.

So at the risk of sounding rude, shaft vibration, Hz vs rpm's, mayonaise vs. mustard don't mean squat in this situation. It is time for both parties to respectfully do business with on another. No judgement as to who is at fault, but I think Autoprop needs to look at its customer service practices.

Carry on.
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Old 13-06-2007, 00:02   #115
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Jose, I am a professional sound engineer. It is my main profession and I was at the leading edge of the sound industry for some years. Without going into a lot of depth, I have to say you are slightly muddled with the assumptions, facts and terms in your above statement. I am not saying this in a slamming way, it is not what I mean. I am simply failing to convey more appropriatly with my words.
There are some very clever software programs out there that will tell you not only the frequency, but also the position of the source of the noise. But they are very expensive. I paid $8K for just one of mine and I have three different programes, each doing something just a little different.
The next issue is interpretation of the information the machine spits back at you. You need to be well trained in the system to understand the data. A simple free program off the net and a microphone may tell you a frequency, but so what? For that matter, the sophisticated program I have may tell you a frequency and where it is coming from, but once again, so what? We know the issue is due to the prop in some way. But is it a fault with the prop? or a fault with the prop/hull match? or operational fault that the manufacturer is simply trying to cover? It will never tell us that. By the way, I think the later is NOT the problem. Bruntons are clever and make a good product. They simply would not be in business if there was an issue. In all fairness, they get to play with much bigger boy's toys than we have and fitting even just one bad prop to a mega yacht would have them bounced around a court room like a rubber ball.
Please please be very careful about hearsay. You have only heard these examples. You can not prove. If you can prove, then great, please do so. That will give some good hard fast ammo to then throw at Bruntons. But with out factual proof, it can be considered slanderus and Liable and is also against our board policy.
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Old 13-06-2007, 11:51   #116
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Mr Vigil states:
"The Amel is one of the nicest cruising boats I have ever seen. They have a beautiful own developed saildrive for a 100 HP engine. This saildrive is known to be silent and vibration free.

Well I have been told the Saildrive bearing worn on those AMELS in just ONE YEAR.

They have a vibration but it was acceptable. That is normal as the saildrive minimizes water flow disturbance, so change of pitching is minimal if hull to prop tip clearance is kept.

Amel discontinued the use of the AUTOPROP after many trials."


I have been following the discussion regarding the AUTOPROP with interest.
I am not an engineer, so I can't speak to the theories expressed above but I can report my experience with regard to Amel and the Autoprop.
I had one on my last boat an Amel Super Maramu which was factory installed as an option. I had the boat for four years and put 12,000 miles and about 1000 engine hours on her. I no problems with the prop at any time except when it was dirty from marine growth after eight weeks inactivity in the Caribbean. These props are very sensitive to marine growth and must be kept scrupulously clean, though I suspect that this not contributing to the above problems.
Amel recommends changing the propshaft bushings at 800 hours or two years. Mine had minimal wear.
Mr. Vigil is not correct when he states that Amel has discontinued the use of the AUTOPROP on their boats, I will have one on my eagerly awaited Amel 54.
I would agree with him, however, that they are excellent cruising boats.
MDL
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Old 13-06-2007, 13:29   #117
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Thanks MDL. Amel is a boat with a fine reputation and pedigree. I envy your fine choice of vessel.
The reputation of Amel is such that they simply would not allow and inferior product to be placed and/or even kept on there vessels if there was such an issue. And I know that these boats are still shipped with the Autoprop. So Jose's comment is totaly false.

I would like to invite Adrian Miles of Bruntons to post. Adrian, I know you are reading and have held back as not wanting to step out of line as a manufacturer posting. But please feel welcome to reply.
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Old 15-06-2007, 20:14   #118
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Alan reply

Dear Alan

Thanks for your reply.

I'm happy that you are a sound engineer so you understand perfectly how FFT analisys can help to trobleshoot a vibration problem.

Sorry. I'm do not agree that a free FFT software can not work out to troubleshoot. We are not proposing anything high tech at all.
You dont need a sophisticated srt up to see an audio frecuency spectrum and check how the fundamental and the harmonics of the vibration shift with the revs up and down the screen.


Alan I have said I have a theory. I had one idea and I wanted to share it for open discussion here.

But the idea is not mine. It is also discussed in pages 84 and 85 of the propeller handbood by Dave Gerr. This is a well known and reputed book.

The "skeg water flow disturbance" posibility ( as called in that book ) was also mentioned by BRUNTONS engineer David on his e mail. He stated that this kind of problem has no solution for the AUTOPROP. Size or recupping is no solution.

I'm very happy that you have invited BRUNTONS to this arena. I think you have got a good idea, I expect they will participate with intelligence, and honesty.

And I repeat again I know BRUNTONS is a reputed company. But their customer service is still refusing a cash back today......Three thousand dollars..... Can you imagine this?

I can't

Jose R Vigil






Quote:
Originally Posted by Alan Wheeler
Thanks MDL. Amel is a boat with a fine reputation and pedigree. I envy your fine choice of vessel.
The reputation of Amel is such that they simply would not allow and inferior product to be placed and/or even kept on there vessels if there was such an issue. And I know that these boats are still shipped with the Autoprop. So Jose's comment is totaly false.

I would like to invite Adrian Miles of Bruntons to post. Adrian, I know you are reading and have held back as not wanting to step out of line as a manufacturer posting. But please feel welcome to reply.
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Old 15-06-2007, 21:05   #119
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Mdl post

Dear Mdl

Thank you for feedback.

The Amel 53 case is true as I have seen that yacht many times in Real Clib Nautico de Palma in Mallorca island Spain.

I'm sorry that the issue of Amel discountinuing was untrue, I will talk with the German Engineer this weekend in Palma and ask who told him that part of the story. I will edit my post to ammend that if possible.

No, my problem doesnt relate with barnacles the prop was brand new and never fouled

While reading your e mail I have felt frustation, as my dream was to enjoy the motorsailing capabilities of the AUTOPROP automatic pitch at low revs.

Enjoy your new 54 in my opinion the best option in the market for the extended cruiser. Unfortunately it was out of my budget

Jose R Vigik



Quote:
Originally Posted by mdl
Mr Vigil states:
"The Amel is one of the nicest cruising boats I have ever seen. They have a beautiful own developed saildrive for a 100 HP engine. This saildrive is known to be silent and vibration free.

Well I have been told the Saildrive bearing worn on those AMELS in just ONE YEAR.

They have a vibration but it was acceptable. That is normal as the saildrive minimizes water flow disturbance, so change of pitching is minimal if hull to prop tip clearance is kept.

Amel discontinued the use of the AUTOPROP after many trials."


I have been following the discussion regarding the AUTOPROP with interest.
I am not an engineer, so I can't speak to the theories expressed above but I can report my experience with regard to Amel and the Autoprop.
I had one on my last boat an Amel Super Maramu which was factory installed as an option. I had the boat for four years and put 12,000 miles and about 1000 engine hours on her. I no problems with the prop at any time except when it was dirty from marine growth after eight weeks inactivity in the Caribbean. These props are very sensitive to marine growth and must be kept scrupulously clean, though I suspect that this not contributing to the above problems.
Amel recommends changing the propshaft bushings at 800 hours or two years. Mine had minimal wear.
Mr. Vigil is not correct when he states that Amel has discontinued the use of the AUTOPROP on their boats, I will have one on my eagerly awaited Amel 54.
I would agree with him, however, that they are excellent cruising boats.
MDL
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Old 16-06-2007, 01:42   #120
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Quote:
And I repeat again I know BRUNTONS is a reputed company. But their customer service is still refusing a cash back today......Three thousand dollars..... Can you imagine this?
I think Bruntons have gone beyond the call of duty in regards to offering you anything. It was not them that you bought the prop from. It is the US dealer that you dealt with and it is them that should be taken to task on this. I think they have so far shown that they are not offering the best of service on behalf of a fine product and manufacturer. The US distributor should be either sorting your problem or refunding your money.
In regards to FFT, I am not saying they won't tell you anything, what I am saying is, what use is the information that it will tell you. You already know there is a noise and a vibration. Seeing that on a screen is not going to help you. Either the skeg can be modified to solve the issue, the prop can be changed to suit the boat better, or if niether are possible, then there is nothing that can be done and the US supplier needs to refund you.
I confirmed that Amel are still using the Autoprop and report that they are very happy with them. They know of no issues with any of their vessels.
If the problem exists with just some boats, then it is very much only a few designs and I guess each would have to be solved on a case by case basis. As in, maybe the skeg or the prop could be altered to suit.

I also didn't understand that Dave Kall's issue with the shaft bending had actually been resolved. That is good to hear. So it is mostly a speed thing now. A smaller prop may solve that, but speed at low RPM may not be an issue as such, but just the way it works.
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