Vent opens while in motion- well, HELLO, Mr. Bernouli! - Fiberglass RV


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Old 10-24-2018, 02:25 PM   #1
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Name: Francesca Knowles
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Vent opens while in motion- well, HELLO, Mr. Bernouli!

Ever arrive some place and find your top vent partly open when you were pretty sure you'd closed it nice and tight just like all the windows in the trailer? I have lots of times and finally figured out it's probably just the immutable laws of physics in action and not my own creeping absentmindedness.
The phenom seems to me to be a perfect illustration of what's called a discrepant event caused by the good old Bernouli effect, see illustration. Higher pressure inside, lower pressure outside: BAM the vent's pushed open.
WHEW!

Source of image Discrepant Event: Bernoulli Effect
(Thank God for online 8th grade physics classes!)
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bernouli effect.JPG  
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Old 10-24-2018, 03:09 PM   #2
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If it there is a constant pressure differential the hatch would not open unless it is really high. HOWEVER, add some turbulence to equation and it can!
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Old 10-24-2018, 05:27 PM   #3
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Francesca,

What vent are you referring to?
Bathroom?
Do you have a picture?

The vent in our bathroom was normally just held down by friction.
We cut a small (2"-3") piece of pool noodle and fit it in above the vent handle to prevent air pressure difference from opening the vent.

Good luck!

Ray
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Old 10-24-2018, 08:48 PM   #4
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In addition to those mentioned, add the effect of road induced vibration!
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Old 10-24-2018, 10:29 PM   #5
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Or, just get a MaxxFan, which locks in any position.
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Old 10-24-2018, 10:50 PM   #6
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Name: Francesca Knowles
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Quote:
Originally Posted by rdickens View Post
Francesca,

What vent are you referring to?
Bathroom?
Do you have a picture?

The vent in our bathroom was normally just held down by friction.
We cut a small (2"-3") piece of pool noodle and fit it in above the vent handle to prevent air pressure difference from opening the vent.

Good luck!

Ray
There's just one in my Trillium, it's in the front third of the trailer roof. It's not really a problem as far as I'm concerned, just one more thing to keep an eye on. Fascinating to see science in action though.

Per the Maxxair suggestion, main reason I wouldn't consider one is that as things stand I'm within a fraction of an inch of breaking the overheight limit on Washington State Ferries and I'm not willing to pay the upcharge associated with that. Can't risk losing my cheapskate credentials!
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Old 10-24-2018, 10:51 PM   #7
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Name: Fredrick
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Wink noodling

[QUOTE=rdickens;721861]Francesca,

What vent are you referring to?
Bathroom?
Do you have a picture?

The vent in our bathroom was normally just held down by friction.
We cut a small (2"-3") piece of pool noodle and fit it in above the vent handle to prevent air pressure difference from opening the vent.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Great Idea...tho our BR vent has yet to suck open as of ~~6000 miles this year.
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Old 10-25-2018, 12:50 AM   #8
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[QUOTE=Francesca Knowles;721903]There's just one in my Trillium, it's in the front third of the trailer roof. It's not really a problem as far as I'm concerned, just one more thing to keep an eye on. Fascinating to see science in action though. /QUOTE]

I've got a couple enclosed cargo storage trailers that the vents go from just cracked to full open even with the Maxair outer covers on them because of the high desert winds I get. I put a mini bungie cord on the handle and the other end under the trim ring....solved it.
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Old 10-25-2018, 07:20 AM   #9
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My Scamp's escape hatch vent does the same- a combination of air pressure and vibration, as others have said. So far, just cranking it down tightly has been enough, but Dave's suggestion is one of several I've read.

The rear sliding windows also like to vibrate open, since the latch mechanism doesn't have a positive catch. Small bulldog clips on the window tracks work for that.

It's all part of the 360 walkaround I have trained myself to do before I get in the vehicle to drive with trailer attached: windows, vents, door (give it a tug), tires, curbs, overhead obstructions, under the trailer, and of course the hitch itself.
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Old 10-25-2018, 11:27 AM   #10
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Name: Wayne & Barbara
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Don't equate the MaxxFan with the MaxAir. The former's cover cranks down and locks by pushing the knob up. Is has a lower profile.
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Old 10-26-2018, 07:07 AM   #11
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Speaking of Mr Bernoulli, his theorem explains why airplanes fly and why baseballs curve.
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