Introduction

This report has been compiled in order to proactively respond to the current noise problems we now all face when running R/C Multi boats

This report highlights the work which has been carried out by Peterborough Model Powerboat Club (PMPBC). This can also assist other clubs who run multi boats of all classes to combat any noise problems they may have.

1. Historic usage of Osier Lake, Peterborough
2. Testing methodology
3. Remedial works carried out
4. Post remedial work readings
5. General comments
6. Conclusions
7. Photographs

Historic usage of Osier Lake, Peterborough

PMPBC have historically operated radio-controlled multi boats both in Nene Park and subsequently at Osier Lake since August 1980
These readings were taken several years ago and at that time there was not deemed to be a problem, Since then, modern boats are now much faster, with high output glow and now petrol engines being used, and the general use of Carbon Fibre in the manufacture of the boat hulls. All of these factors contribute to the higher noise now being generated by multi boats.
To this end PMPBC took it upon themselves to carry out noise tests to determine the current noise levels

Testing methodology.

A calibrated tripod mounted noise test meter was installed at 1250mm above the water level and at a distance of 10 Metres from the path the test boats will take in accordance with MPBA recommendations, Multiple noise readings were taken using the Slow setting, db(A) and with the test boats at 90 deg to the noise meter.
The initial test results were disappointing and are as follows:
3.5cc- Typically in the region of 84-884B(A)
7.5cc- Typically in the region of 83-894B(A)
Some boats were slightly quieter, and some were noisier with the above readings being typical. It was also found that the loudest tuned pipes were the CMB and Nova Rossi pipes manufactured from Aluminium with PMB steel pipe being the quietest

Remedial works carried out

3.5cc
Numerous Carbon fibre bracing ribs installed between the hull and the top deck. See photo 1
Numerous Carbon Fibre bracing ribs installed to the underside of the tank cover, See photo 2
Additional mounting screws installed to secure the tank cover. See photo 3
Softer 45 Shore rubber bobbins installed onto the gearbox
Lengths of thick wall rubber tube installed into the gap between the tops of the tank/s and the top deck will reduce the vibration and hence noise.
PMB steel pipe installed
7.5cc
Numerous Carbon fibre bracing ribs installed between the hull and the top deck.
Additional mounting screws installed to secure the tank cover,
Softer 45 Shore rubber bobbins installed onto the gearbox,
Hull fully foamed using 2 pack expanding marine quality foam.
PMB steel pipe installed
15cc
Numerous Carbon fibre bracing ribs installed between the hull,
and the top deck. Additional mounting screws installed to secure the tank cover.

Softer 45 Shore rubber bobbins installed onto the gearbox,
Hull fully foamed using 2 pack expanding marine quality
PMB steel pipe installed

Post remedial work noise readings

3.5cc – Typically in the region of 78-824B(A)
7.5cc ~ Typically in the region of 80-8 14B(A)

General comments

As can be seen from the above readings the noise levels can be reduced down to an acceptable level with some fairly minor modifications being made to the boats.

General

Hard Male / Female rubbers and Female / Female gearbox rubber bobbins were found to transmit a lot of vibration and hence noise into the hull,
Soft (Shore 45) Male / Male gearbox rubber bobbins transmitted considerably less vibration and hence noise into the hull
PMB steel pipe found to be quieter than CMB and Nova Rossi by 1-dB(A).
The 3.5cc boats were of different design and construction, ranging from gel-coat Carbon Fibre to full Carbon Fibre,
There was no noticeable difference in the noise readings between coupling and solid shaft boats
There was a 2-44B(A) increase in the noise level when running, without an engine cover

Conclusions

installing multiple Carbon fibre bracing ribs between the bottom of the hull and the top deck will reduce the vibration and hence noise from the tank cover.
1. CF bracing on the tank cover
2. Install soft (Shore 45) rubber bobbins which will transmit less vibration and hence noise into the boat. Install additional securing screws to the tank cover to reduce vibration.
3. Fit an engine cover.
4. Fit a PMB steel pipe
Installing lengths of thick wall rubber tube into the gap between the tops of the tank’s and the top deck will reduce the vibration and hence nose into the top of the hull and tank cover.
To get the ultimate in noise reduction, fully foam the inside of the boat

Prestwich Models