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 Post subject: Ama Vent
PostPosted: Thu Aug 04, 2016 7:44 pm 
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From a thread in the Eclipse forum that asks if there is a vent to release pressure in the Eclipse board when stored in a hot place:
mmiller wrote:
Yes, it is vented.

Sea Dog wrote:
Automatically?

mmiller wrote:
Yes, it is a Gortex patch in a small hex fitting. Below one of the pedals.

Would a fitting like this be good in place of the drain plug on our amas?


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 Post subject: Re: Ama Vent
PostPosted: Fri Aug 05, 2016 9:13 am 
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Don't think so. Venting is not an issue with amas.

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 Post subject: Re: Ama Vent
PostPosted: Fri Aug 05, 2016 11:24 am 
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Here is an idea,
Take the plug out of the back of the AMA, fill the AMA with helium, now put the plug back.
You may get way better flotation.

I never said it was a good idea, just an idea (actually I might try it, I'll wait for the next family birthday party, steal all the party balloons, and release the helium into the AMA).

Not as far fetched as people paying huge sums to fill their tires with nitrogen (the air we breath contains around 75% nitrogen already, and it's free)

FE


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 Post subject: Re: Ama Vent
PostPosted: Fri Aug 05, 2016 11:52 am 
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Location: Houston, TX
This FE Hobie Hovercraft sounds great. I always hate going around stealing little kids party balloons. Got to do what ya got to do though. :shock:

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 Post subject: Re: Ama Vent
PostPosted: Fri Aug 05, 2016 12:45 pm 
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fusioneng wrote:
Here is an idea,
Take the plug out of the back of the AMA, fill the AMA with helium, now put the plug back.
You may get way better flotation.

I never said it was a good idea, just an idea (actually I might try it, I'll wait for the next family birthday party, steal all the party balloons, and release the helium into the AMA).

Not as far fetched as people paying huge sums to fill their tires with nitrogen (the air we breath contains around 75% nitrogen already, and it's free)

FE

i believe the nitrogen thing stems from racing, tire pressure is key, so being able to control expansion from tire heat is a great idea


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 Post subject: Re: Ama Vent
PostPosted: Fri Aug 05, 2016 12:58 pm 
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Location: Bellevue, Nebraska
Carl M wrote:
fusioneng wrote:
Here is an idea,
Take the plug out of the back of the AMA, fill the AMA with helium, now put the plug back.
You may get way better flotation.

I never said it was a good idea, just an idea (actually I might try it, I'll wait for the next family birthday party, steal all the party balloons, and release the helium into the AMA).

Not as far fetched as people paying huge sums to fill their tires with nitrogen (the air we breath contains around 75% nitrogen already, and it's free)

FE

i believe the nitrogen thing stems from racing, tire pressure is key, so being able to control expansion from tire heat is a great idea

It also stems from the airline industry/ Air Force. When I was an F-16 mechanic we filled the landing gear with nitrogen because it wasn't susceptible to the pressure fluctuations associated with temperature change. Going from 2000ft above sea level to 40000+ft above sea level and back down there is a huge temperature swing. We see the same thing here in the northern Midwest between the seasons. I can confirm that filing your tires with nitrogen means that, unless you have a leak, your pressure will stay the same regardless of outside temperature.

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 Post subject: Re: Ama Vent
PostPosted: Tue Aug 09, 2016 12:46 pm 
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I am pretty sure that would violate the universal gas law, PV=NrT
a tire holds V (volume) pretty constant,
N is fixed as the number of moles of gas in the tire
r is a constant
Changing environmental temperature T (it is in Kelvin, so environmental range is a fairly small percent change) must then change P, and the change does not depend on which gas it is.
Water in the gas in the gas in the tire is a different deal, because it can change state, so if N in tires performs better, I bet it is because the gas is completely dry, unlike the air from a compressor.


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 Post subject: Re: Ama Vent
PostPosted: Tue Aug 09, 2016 12:54 pm 
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beebrain wrote:
I am pretty sure that would violate the universal gas law, PV=NrT
a tire holds V (volume) pretty constant,
N is fixed as the number of moles of gas in the tire
r is a constant
Changing environmental temperature T (it is in Kelvin, so environmental range is a fairly small percent change) must then change P, and the change does not depend on which gas it is.
Water in the gas in the gas in the tire is a different deal, because it can change state, so if N in tires performs better, I bet it is because the gas is completely dry, unlike the air from a compressor.


Probably want to include the fact that air from a compressor is a mixture of gasses and not homogenous.
Here is an article from Popular Mechanics that explains it for those of us that don't like complicated math. :D
http://www.popularmechanics.com/cars/how-to/a3894/4302788/

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 Post subject: Re: Ama Vent is useful
PostPosted: Wed Aug 10, 2016 7:00 am 
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The vent is useful. I have seen my ama get deformed in the hot sun from too much air pressure. The middle of the ama gets a little fatter and the front of the ama gets two dents in the side near the front... Initially I thought that my ama got dented somehow on both sides, weird...., but, when I let the pressure out, it's shape went back to normal. The hot sun can put a lot of pressure in those amas.


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 Post subject: Re: Ama Vent
PostPosted: Wed Aug 10, 2016 8:04 am 
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Joined: Tue Jul 19, 2005 6:29 pm
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Location: High Point, NC
The displacement of the ama will not change regardless of what you put in it. The amount of weight it needs to displace order to remain floating, of course, does depend on what's in it so the helium comment is not without technical merit. However, the weight savings between that amount of helium and normal atmospheric air isn't likely to net you anything practical.

I just crack my drain plugs when the boat is not in use and remember to close them just before hitting the water. Then again, cracking them open when I come off the water.


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