Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Noisy Boat - Help!  (Read 1258 times)

Sam-R

  • Shipmate
  • *
  • Offline Offline
  • Posts: 4
  • Model Boat Mayhem is Great!
Noisy Boat - Help!
« on: January 23, 2025, 03:47:57 pm »

Hi everyone!
I'm new to this forum - a newbie boat builder. Nice to be here :) So far I've build two Aeronaut Divas (one for my dad) and in the process with an Aeronaut Jenny.


I was hoping for some advice. My previous two builds (the Divas) both suffer from sounding like a bag of spanners. I've just tested my current build - the Jenny - and it's sounding pretty much exactly the same. I'm bench testing and not under load - because I'm reluctant to glue everything in place, then get stuck with is as with the Divas.


The prop alignment seems to be good (not perfect) and I'm using a JP universal coupler. I've tried also adding a bit of marine grease to see if that helps but no joy / difference. It's very much a vibrational sound and pretty loud, not the sort of thing in align with the relaxing days boating I had in mind.


I've had a look at some posts on this forum but thought it might be helpful if I posted my specific issue to see if anyone spots anything obvious with the build.


There's a short video here:
https://vimeo.com/1049709508/24ae397693?share=copy


And I've attached some pics! Any advice would be very much appreciated.


Thanks,
Sam


Logged

Terry

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 211
  • Location: Ebenfurth Austria
Re: Noisy Boat - Help!
« Reply #1 on: January 23, 2025, 04:50:06 pm »

I had exactly the same problem with a Jenny and came to the final conclusion that the sterntube and shaft supplied with the kit was the culprit, not good enough quality for high r.p.m. but it was already glued in place. Just live with it now, but it´s not quite so bad in the water.


Cheers, Terry.
Logged

Colin Bishop

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 12,405
  • Location: SW Surrey, UK
Re: Noisy Boat - Help!
« Reply #2 on: January 23, 2025, 05:45:16 pm »

Terry is probably right but it could be the coupling. Those HUCO clones are often bored out of true which causes a lot of vibration at high RPM.

One trick is to use a length of thin wood such as dowel and place one end in your ear and the other in various places along the drive train while you rev the motor. This can give an indication of where the vibration is worst and a clue to the cause. Unfortunately with some of the cheap tubes and shafts the shaft itself may not be perfectly straight. Rolling it on a sheet of glass or similar can show up any irregularities. On one of my boats the tube itself was out of true and had to be replaced which was a major job.

These things can be very frustrating, it's bad enough when you don't get things quite lined up yourself and a lot worse when you can't rely on the accuracy of the individual components.

Oh, and the motor itself can make a lot of noise at high revs!

Colin
Logged

dodgy geezer

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 4,014
  • Location: London
Re: Noisy Boat - Help!
« Reply #3 on: January 23, 2025, 06:29:03 pm »

The noise does not seem too bad to me - as has been stated, it will be lower in water under load. That will be because the motor will be running slower, and the hull skin vibrations will be damped.


The hull acts like a drum, and amplifies the sound. I glue expanded polystyrene chunks to unsupported sections of hull skin to give extra buoyancy and to suppress sound. Luxury car manufactures do something similar with heavy foams to stop car panel resonance...


I see that the motor is mounted on one bulkhead, allowing a single resonance mode. Try holding the back of the motor when it is running and see if that affects the sound. If it does, then it may help to add an extra mount at the back to lower vibrations.
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 4,215
  • Location: North London
    • Dive-in to Model submarines
Re: Noisy Boat - Help!
« Reply #4 on: January 23, 2025, 07:35:54 pm »

Use a rubber drive coupling and rubber mount the motor, then all you'll hear is the water rippling past the hull.
Logged

Sam-R

  • Shipmate
  • *
  • Offline Offline
  • Posts: 4
  • Model Boat Mayhem is Great!
Re: Noisy Boat - Help!
« Reply #5 on: January 23, 2025, 08:39:04 pm »

Thanks so much for everyone’s help! I think I might try a combination of these tips, hopefully they will do the trick. Luckily the prop tube and shaft are still removable. Would anyone be able to suggest a good brand or make of prop shaft please?  The motor un-coupled is running pretty quiet so I’m leaning towards it being the prop shaft. Thanks again 🙏
Logged

Colin Bishop

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 12,405
  • Location: SW Surrey, UK
Re: Noisy Boat - Help!
« Reply #6 on: January 23, 2025, 09:08:24 pm »

Sometimes the shaft and tube is a bit too lightweight construction and suffers as a result. An 8mm tube with a 4mm shaft is pretty solid if the boat will accommodate that. Some tubes are 6mm with a 4mm shaft and they are really only suitable for light duty.

For example Model Boat Bits:
https://www.modelboatbits.com/Model-Boat-Propshaft/

There are other suppliers.

Colin
Logged

Sam-R

  • Shipmate
  • *
  • Offline Offline
  • Posts: 4
  • Model Boat Mayhem is Great!
Re: Noisy Boat - Help!
« Reply #7 on: January 23, 2025, 09:18:45 pm »

Thanks a million Colin!
Logged

mbm999

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 100
  • Model Boat Mayhem is Great!
Re: Noisy Boat - Help!
« Reply #8 on: January 23, 2025, 10:41:06 pm »

I put a 6mm/4mm slimline prop shaft in my Diva and have no noise issues (tho I am a bit deaf  :-) ).

The one supplied in the kit had a bent shaft but I had decided to go 4mm and brushless anyway - more choice of props/couplings too.

Cheers,
Mark
Logged

roycv

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,509
  • Location: S.W. Herts
Re: Noisy Boat - Help!
« Reply #9 on: January 24, 2025, 09:48:11 am »

Hi I have stopped using the plastic parts of the Huco couplings.  Just the brass inserts with a 2 inch length of thick walled tubing joining them.  The plastic tubing should be a tight push on fit for the brass serrated connectors.

This will also show if one of the brass pieces is on at an angle.  If the brass part that screws onto the prop shaft thread is even slightly misaligned you can see it as a blur when the motor is spinning.  What can help here is a tight washer that goes over the threads but not the shaft, then screw the nut on, and then the brass part and lock them up against the washer.

If the brass part is held on to the plain prop shaft then check it is a firm push on fit as otherwise the grub screw will force it out of true.
 I usually go for silent running!
All the best
Roy


Logged

Sam-R

  • Shipmate
  • *
  • Offline Offline
  • Posts: 4
  • Model Boat Mayhem is Great!
Re: Noisy Boat - Help!
« Reply #10 on: January 24, 2025, 07:16:42 pm »

Thanks Roy and Mark! Both v useful comments. I felt the Diva supplied prop shaft was pretty flimsy. I heard that heating the epoxy with a heat gun might allow me to remove and replace the stock shaft. I might give that a go.


A new prop shaft ordered today for the Jenny 👍



Also the plastic tubing is a great idea!


Thanks again.
Logged

Colin Bishop

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 12,405
  • Location: SW Surrey, UK
Re: Noisy Boat - Help!
« Reply #11 on: January 24, 2025, 07:33:50 pm »

If you can heat up the prop tube without damaging the surrounding area it should be possible to extract it. A soldering iron on the tube is another option which worked for me.

Colin
Logged
Pages: [1]   Go Up
 

Page created in 0.095 seconds with 21 queries.