Cruisers Forum
 


Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 24-03-2021, 11:09   #31
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by Compass790 View Post
Maaate I think his prop blades are composite, hence the black colour but I can see your other points.
Sometimes ya just need to have a bitch about it.


No, I donít have to have a bitch about anything.

Read the question I asked. Look hard at what I actually posted not what someone with comprehension issues thinks I wrote.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 24-03-2021, 11:11   #32
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by MicHughV View Post
I did remember once seeing a guy building up a " fairing" in front of his prop behind the keel...it's something that has to be "shaped"...I seem to recall closed cell foam was used and it was shaped with a rasp...prior to the foam, some small holes were drilled into that flat surface behind the keel and some screws or bolts were epoxied into the holes...this gave the foam some " grip" to the back of the keel, the foam was also glued here....WEST maybe, I don't recall.....after shaping it was glassed....but I think a coat of WEST epoxy would likely also work.
My recollection is that it made a world of difference in performance and noise.


Yes, building things up was one of the options I was considering.

If there was a significant risk of damage to the prop or drivetrain I would go that way.

Nobody is suggesting I need to worry so I will just put up with the noise since, as I mentioned, I motor very rarely anyway.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 24-03-2021, 11:12   #33
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by MicHughV View Post
my english is terrible....sorry.....was trying to describe the turbulent water seen behind a a plank moved thru' the water..the prop has to grab ahold of this " turbulent" water to move forward, not good.....clean water flow is the happy medium.


Your English is fine, and your reading skills are way better than some members of this forum.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 24-03-2021, 11:17   #34
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by FPNC View Post
What is the diameter of the propeller and what is the gear reduction ratio?

About 19Ē with a two to one gearbox.

I did discuss the option of a smaller prop and a lower reduction ratio with the prop vendor but we couldnít come up with an option that would not have lead to very poor performance. Given the weight and windage of the boat we felt the loss of power would become a safety issue. As it is, Iíve put in the smallest engine I dared.

The thing is, the Kiwiprop is perfect for my needs. The feathering aspect really helps in light winds, but the reverse is fantastic and has made manoeuvring the boat much, much less stressful.

In the face of this, the slight noise is a minor concern. Particularly if no damage is likely to result.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 24-03-2021, 11:21   #35
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by Wotname View Post



However surely that section of the hull would be solid glass, no?

:

Oddly enough, given how the boat was constructed, no it isnít. Itís actually very cleanly moulded there. Still thick as a brick sh-t house (like some posters really) but not thick enough to grind back in any significant manner.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 24-03-2021, 14:11   #36
Marine Service Provider

Join Date: Sep 2014
Location: Auckland, NZ
Boat: Compass 790 , 7.9 metres or 26 ft
Posts: 2,542
Re: Propellor interference noise

Quote:
Originally Posted by GILow View Post
No, I donít have to have a bitch about anything.

Read the question I asked. Look hard at what I actually posted not what someone with comprehension issues thinks I wrote.

OOOHH quite the sensitive one.
Ok I apologise for the bitch bit.
As for the rest I do think I understand what more space means but yet you go on to say "Yes, building things up was one of the options I was considering" Which is it then? That does not require an answer.



However I will not post any more as I've upset you. Good luck with sorting it
Compass790 is offline   Reply With Quote
Old 24-03-2021, 14:20   #37
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 12,984
Re: Propellor interference noise

Quote:
Originally Posted by GILow View Post
Oddly enough, given how the boat was constructed, no it isn’t. It’s actually very cleanly moulded there. Still thick as a brick sh-t house (like some posters really) but not thick enough to grind back in any significant manner.
Interesting.....

Now I don't know if you are hurting anything but I do have opinions on how to change stuff - I luv changing stuff .

If I was altering the 'square' aft section of the hull, I would glue on a block of wood, grind / sand to desired shape and glass over (with epoxy) assuming there is room to do so. If not enough space, then consider filling the void in the interior section of the hull before shaping. But I dunno how Swannie built the boat, how the cutless bearing is supported, how the stern tube is arranged (if any) and so on.

I'm sure you know these things or can suss them out so I have nothing meaningful to add ATM.

We know the existing tip clearance is well before the benchmark minimum and maybe would be very difficult to change so I would look at making everything else as close to ideal as possible. Is the 'chittering' noise detrimental - again I dunno but I personally would find it very annoying and a distraction; both in a calm or a gale - times when the engine might be running.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 24-03-2021, 17:19   #38
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by Wotname View Post
Interesting.....

Now I don't know if you are hurting anything but I do have opinions on how to change stuff - I luv changing stuff .

If I was altering the 'square' aft section of the hull, I would glue on a block of wood, grind / sand to desired shape and glass over (with epoxy) assuming there is room to do so. If not enough space, then consider filling the void in the interior section of the hull before shaping. But I dunno how Swannie built the boat, how the cutless bearing is supported, how the stern tube is arranged (if any) and so on.

I'm sure you know these things or can suss them out so I have nothing meaningful to add ATM.

We know the existing tip clearance is well before the benchmark minimum and maybe would be very difficult to change so I would look at making everything else as close to ideal as possible. Is the 'chittering' noise detrimental - again I dunno but I personally would find it very annoying and a distraction; both in a calm or a gale - times when the engine might be running.
It really is a juggling act.

If I build up the trailing edge then it will end up closer to the prop, possibly exacerbating the noise issue.

I am very reluctant, verging on refusing to consider removing any bit of the hull. The greatest asset this boat has is the bullet proof build that the Swansons were famous for. The construction around that bit of the boat seems pretty critical too.

No, it seems unlikely that I am doing damage. I will keep an eye on the propeller tips as per boatpoker's caution. There is no evidence of trouble so far and there's about 100 hours on the propeller now.

As for the noise itself... Not too bad... if I am not worried about it causing damage then I don't think it will worry me all that much.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 24-03-2021, 17:33   #39
Registered User
 
malbert73's Avatar

Join Date: Jun 2008
Boat: Tartan 40
Posts: 1,885
Propellor interference noise

I had same issue on my old Luders 33 with 4 blade variprop. I did grind away the aperture ahead of prop to taper it and fair it and it made a difference. You can maybe grind away the square edges and then add laminate for strength. I also was able to enlarge aperture at top and bottom in same way. It all made a significant difference
malbert73 is offline   Reply With Quote
Old 25-03-2021, 09:48   #40
Registered User

Join Date: Jan 2019
Boat: Beneteau 432, C&C Landfall 42, Roberts Offshore 38
Posts: 2,857
Re: Propellor interference noise

I can offer this.....some years ago I got interested in propellors and performance,etc...

The propellor handbook by Dave Gerr....its has a ton of information in there....everything you would possibly want to know about props, apertures,etc..

PDF Download Propeller Handbook, Second Edition: The ...mellieoglesbygunn.files.wordpress.com › 2017/05
MicHughV is online now   Reply With Quote
Old 25-03-2021, 09:51   #41
Registered User

Join Date: Jan 2019
Boat: Beneteau 432, C&C Landfall 42, Roberts Offshore 38
Posts: 2,857
Re: Propellor interference noise

I didn't attach the link right, but you can google "The propellor Handbook" by Dave Gerr and it will take you to a free download...

It is substantive and parts take reading several times to fully comprehend, but will certainly guide any decision you might want to make.
MicHughV is online now   Reply With Quote
Old 25-03-2021, 15:33   #42
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by MicHughV View Post
I didn't attach the link right, but you can google "The propellor Handbook" by Dave Gerr and it will take you to a free download...

It is substantive and parts take reading several times to fully comprehend, but will certainly guide any decision you might want to make.


Good book, but sadly lacking clear guidance on how to modify a Swanson 42.

Maybe the later edition has that chapter.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 25-03-2021, 17:35   #43
Moderator
 
Jim Cate's Avatar

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 18,505
Re: Propellor interference noise

Quote:
Originally Posted by GILow View Post
Good book, but sadly lacking clear guidance on how to modify a Swanson 42.

Maybe the later edition has that chapter.
Matt, I think that is covered in the Husqvarna chain saw instruction manual...


Hope it is goin' well, mate!

Jim
__________________
Jim and Ann s/v Insatiable II, reluctantly incarcerated in the POW marina, Hobart, where shore power is assisting our reluctant solar panels in maintaining our life style.
Jim Cate is online now   Reply With Quote
Old 25-03-2021, 18:03   #44
Registered User
 
GILow's Avatar

Join Date: Sep 2008
Location: On the boat, somewhere in Australia.
Boat: Swanson 42
Posts: 7,705
Re: Propellor interference noise

Quote:
Originally Posted by Jim Cate View Post
Matt, I think that is covered in the Husqvarna chain saw instruction manual...





Hope it is goin' well, mate!



Jim


More than likely you are correct, it seems an appropriate tool for the job.

Splashing tomorrow morning with the tide, all will be revealed to me soon.
__________________
On my way at last.
GILow is offline   Reply With Quote
Old 29-03-2021, 12:18   #45
Registered User

Join Date: Dec 2015
Location: Nanaimo BC
Boat: modified Spray 56' oa
Posts: 377
Re: Propellor interference noise

Can you eliminate other possible causes? Things like engine alignment, a whumpy shaft ,or bent at the cutlass, cutlass failing ,misaligned from birth, or lacking cooling flow due to hidden growth, damaged blade pitch.thust bearing in tranny not happy.?
topmast is offline   Reply With Quote
Reply

Tags
enc, interference, noise, rope

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
RF Noise or interference from LED bulbs Peregrine1983 Electrical: Batteries, Generators & Solar 11 20-10-2017 15:18
Want To Buy: Output / Propellor Shaft for Yanmar Mustang Sally Classifieds Archive 1 17-05-2010 09:53
Propellor BC Mike Engines and Propulsion Systems 25 27-01-2007 05:07
Bukh Propellor Marauder Propellers & Drive Systems 22 15-01-2007 21:09
Hundstadt propellor Alan Wheeler Propellers & Drive Systems 4 29-10-2006 21:29

Advertise Here


All times are GMT -7. The time now is 17:22.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.