Irritating fan motor resonance!! Help.

[healhustler]

The last time anchored out, our genset went down and we got stuck with power-sucking house fans to keep some air flow going in major heat and humidity, so now I’m installing these super quiet (selected especially for that quality) Caframo 12V boat fans. Of course, with boat bulkheads and walls to mount upon, one might as well be mounting them on the bell of a guitar!

This is ridiculous. I’ve got a full inch or foam insulation beneath each fan mount now, and each mounting screw resting in foam washers. I’ve also tried through bolting with foam padded backing plates, but they’re still pretty noisy. Anybody come up with a better way?

Here’s a pick of the fan type. This is with a half inch pad, a half inch pad backing plate, holes oversized so bolts wouldn't touch the wood, and rubber washers on the bolt heads. Still pretty loud on both sides of the bulkhead.
Admiral doesn’t approve.

 

[Larry M]

Larry: Have you tried a Hella 2 speed Turbo fan? We went through the same think and found the Hella’s to be quieter than the Caframos. We have nine fans on Hobo. I have had to adjust the prop on the shaft occasionally and have also returned a few because the fan blades weren’t balanced but we’re all Hellas now.

https://www.hellamarine.com/en/products/accessories/fans/turbo-fan.html

 

[Sidclark]

We had six of those fans on our last boat and by constant fiddling you could get them to quieten down for a few hours at most. The problem is they are not balanced and won't hold a balance when you do find that sweet spot. We tried everything too. New blades, repositioning and no dice. Finally, listened to the wife and bought these...

https://www.westmarine.com/buy/cafr...an-multi-position-white--17744988?recordNum=3

Pricey, but even mounted right by our head in the master cabin, we could still sleep. Wife approved, so that's all there is to say about that!

 

[Comodave]

We don’t permanently install 12 volt fans. We have 2 Ridgid 18 volt fans that can also run on 120 volts. With a 4 amp battery they will run on low for 2 days. They are deadly quiet unless you run them on high. They have a knob that adjusts the fan speed to what ever you like. And they come with a lifetime service plan. And they don’t run the house batteries down.

 

[Xsbank]

24 volt fans...

 

[Woodland Hills]

We had six of those fans on our last boat and by constant fiddling you could get them to quieten down for a few hours at most. The problem is they are not balanced and won't hold a balance when you do find that sweet spot. We tried everything too. New blades, repositioning and no dice. Finally, listened to the wife and bought these...

https://www.westmarine.com/buy/cafr...an-multi-position-white--17744988?recordNum=3

Pricey, but even mounted right by our head in the master cabin, we could still sleep. Wife approved, so that's all there is to say about that!

We have 6 of those onboard, one for each berth. Although they are 24v we have been running them at 32v with no issue.

 

[FF]

So called computer fans rated at 24V are very quiet when operated on 12v.

We have Dorade vents and cap them with 6 inch plastic deck plates.

As the computer fans are not reversible purchasing a (2) 12v units allows air to be sucked in or blown out and a 24V unit for sleeping allows rapid R&R to get just the noise and air volume / direction as desired.

 

[D.Duck44]

You may find that increasing the mass of the mount (sheet lead, or a bit of SS plate) may damp out the resonance.

 

[FlyWright]

Very timely post!

I recently mounted a 2 inch Harbor Freight magnet (painted white except for the mag surface) onto my Caframo 747 fan so that I could use the fan wherever on the boat I had mounted a 2 inch steel washer. I put these washers in the ceiling in my head headliner near the portlight, on my fwd cabinet to move heat aft and on my hatch frame to facilitate summer air circulation.

The head location in the headliner makes a racket like a banjo so I'm thinking of mounting the washer on a 2 inch rubber or firm foam mount washer. I'm hoping to isolate the vibes and noise.

Maybe a foam insulator will help in your situation in addition to the rubber washers. I figure something needs to absorb all that high freq vibe energy.

 

[Haylands]

We have one and I found it was better solidly fixed rather than isolated, then the mass it is fixed to works as a damper as well.... Worth a try...!

 

[Nomad Willy]

The fan shakes something that is resonate at half or double the frequency of the fan.
Attach the fan closer to a corner or bulkhead.

 

[healhustler]

Larry: Have you tried a Hella 2 speed Turbo fan? We went through the same think and found the Hella’s to be quieter than the Caframos. We have nine fans on Hobo. I have had to adjust the prop on the shaft occasionally and have also returned a few because the fan blades weren’t balanced but we’re all Hellas now.

https://www.hellamarine.com/en/products/accessories/fans/turbo-fan.html

Geeze, Larry....I just removed the original Hella units for the same complaint. I’m trying any and all suggestions here to make sure I covered the bases, but I’m close to throwing in the towel and spending another 10 bucks each on pro designed vibration dampers.

I began with mounting direct to the bulkhead, then half inch foam, then half inch front and back, and now it’s one inch front and half inch back with holes oversized and rubber washers. Next I’ll add a SS plate and corner mounting. These were the quietest units we tested at the display in West Marine, but of course, they aren’t mounted to wooden bulkheads there.

 

[OldDan1943]

I think I have 5X12vt West Marine fans. I leave them on 24 hrs a day. My house mouse shuts off one in the stateroom, I tun it back on SMIRK
I do not find the noise level offensive but then, I am hard of hearing.
I do consider the fans a disposable item and always carry 3 spares. I replace them every 3 or 4 years.

 

[Comodave]

Guys, all the issues you are referring to are solved with the Ridgid fan I referenced above, quiet, moves way more air than the small 12 volt fans and doesn’t resonate. At the dock I can use an extension cord to power them off 120 volt and on the hook I can use the 18 volt batteries and not run down the house batteries. And you can take them off the boat if you need a fan elsewhere. I also carry it into the engine room when I am working there. One of them pretty much follows me wherever I am working.

 

[healhustler]

Guys, all the issues you are referring to are solved with the Ridgid fan I referenced above, quiet, moves way more air than the small 12 volt fans and doesn’t resonate. At the dock I can use an extension cord to power them off 120 volt and on the hook I can use the 18 volt batteries and not run down the house batteries. And you can take them off the boat if you need a fan elsewhere. I also carry it into the engine room when I am working there. One of them pretty much follows me wherever I am working.

Yes, picked up one to try yesterday at Black Friday sale. At the very least, I’ll be using it when down under the galley for machinery service. Also great for bilge painting ventilation. Ugly, but then one can’t have everything can we. Maybe I can redo the interior upholstery on orange & black!

 

[Comodave]

We love ours. We have 2. Keep one by my recliner in the house for when it gets too hot. And keep the other on the boat full time. When we are going to go overnight on the boat we take both of them. It is really handy to be able to move them around without power cords.

 

[altinr]

Quiet fans

I’ve found that larger fans, 10-12”, with at least 2 speeds, are much quieter. Most can either sit on a flat surface or u can hang them.
The O2 cool fans are quiet, cheap, and most run on 12v, batteries, or 110v if you have an inverter or generator.

For example: https://www.amazon.com/gp/aw/d/B00ATSHJ1Q/ref=ox_sc_saved_image_5?smid=AJ5IBHU2RIN49&psc=1

 

[fryedaze]

Larry we installed 4 of those fans. Two of the four vibrate bad in high speed but are not bad at slow. The other two are great in high or low. I called the company and they sent me a new blade. It didn't make any difference. I think the problem is the lack of a small bearing where the shaft comes through the housing. A simple plastic sleeve on the shaft should eliminate the wobble. That not is on my long list.

 

[healhustler]

Admiral says install two in each cabin, one in galley and one in the head. After failing with several insulating ideas, I tried screwing a 7/8” cork cored, elastomeric pad to the wall, then counter sunk two bolts into the back of 2nd identical pad to secure the fan with rubber washers and nuts, then mounted the pad with the fan to the pad on the wall with perimeter screws, separating the pads with water hose washers (which also leaves a vibration/compression air space). This way, both the fan and the mounting bolts can vibrate without a cooperative resonance path to the wall. So far, the fix comes to about $2 each unit.

I am trying one now but will also try each of the eight units we purchased before final installation, if for nothing else, to see if some are better balanced as Dave noted above. We’re also comparing one of the units Commodave talked about for sound and air movement. Likely, that style will be preferred for sleeping.

 

[FlyWright]

You'll have so many fans aboard maybe you can point them all aft when underway to help your speed, Larry.

 

[healhustler]

You'll have so many fans aboard maybe you can point them all aft when underway to help your speed, Larry.

True, but I know why she wants these kind of mounted units. We’ve got an old cat that would likely investigate anything he could reach, and having them high and in the corners will help spin the circulation in each cabin. We’ve got an assortment of worn out fans that we keep moving around, dropping, stepping on, kicking, etc.. When the Admiral says jump, ....

 

[healhustler]

You'll have so many fans aboard maybe you can point them all aft when underway to help your speed, Larry.

You know, James Krogen did do his design homework when it came to whole-boat ventilation on these Manatees. Two huge forward-facing bow hatches below the windshield open in various degrees to scoop gobs of air at anchor or underway. They fill 6’ long cabinets which can be opened at the rear to flow into the pilothouse. Two more deck hatches at the bottom rear of the cabinets open to the galley and companionway to blow through the rest of the boat.

The Admiral and I love this feature for blowing cooking odors out quickly. The system moves tremendous volumes of air so it makes quick work out of wet clothes or shower towels hanging in the veranda where the ducted air ultimately exhausts through twin saloon doors. We also find the additional hatches convenient as a pass-through for delivering coffee or sandwiches from the galley to the pilothouse.

The problem is that as efficient as it is in ventilation, if you happen to be moving through or anchoring around a flock of mosquitoes, your boat is full of them in about 10 seconds. The idea behind the fans comes from last year’s experience when we were in a really hot anchorage with no genset and dead air. Mosquitoes kept us locked up. The Admiral says tiny fans to keep the air moving throughout the boat was all she needed to make the event bearable.

I’ll experiment with placing all the fans on “high” and directed aft to see if there’s any “get home” power potential.