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Old Nov 01, 2012, 04:42 AM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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Just checking here: Do you mean that you pressured the bladder up with your compressor while the whole mould was in a vacuum bag?? If so, what pressure etc.?

It's not clear to me what you did here Jordan.
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Old Nov 01, 2012, 04:56 AM
Alphabets make great soup
Hamburglar's Avatar
Australia, ACT, Canberra
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Yes that's what I did. See pics I posted earlier.

Moulds at 25"Hg, bladder at 10psi. Total pressure on the layup is about 22psi.

It works but as Matin predicted earlier, a bladder failure is catastrophic as the moulds lose clamping pressure.
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Old Nov 01, 2012, 04:33 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
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Quote:
Originally Posted by Hamburglar View Post
Yes that's what I did. See pics I posted earlier.

Moulds at 25"Hg, bladder at 10psi. Total pressure on the layup is about 22psi.

It works but as Matin predicted earlier, a bladder failure is catastrophic as the moulds lose clamping pressure.
I see now! I had assumed you were just going to vent the bladder to atmosphere like the option discussed in the Inflation Bladder thread. Goes to show, assume nothing....
I cannot imagine why you would try that. Must be some advantage I'm still not aware of??

Jim.
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Old Nov 01, 2012, 04:51 PM
Alphabets make great soup
Hamburglar's Avatar
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Quote:
Originally Posted by Jimbello View Post
I cannot imagine why you would try that. Must be some advantage I'm still not aware of??
Mould only has to cope with 10psi yet the layup is pressurised at 22psi.
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Old Nov 01, 2012, 09:28 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
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Quote:
Originally Posted by Hamburglar View Post
...........
Mould only has to cope with 10psi yet the layup is pressurised at 22psi.
There's the reason! I had not thought it through completely.

So why did it blow out the flange etc.?
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Old Nov 01, 2012, 09:52 PM
Alphabets make great soup
Hamburglar's Avatar
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Quote:
Originally Posted by Jimbello View Post
Why did it blow out the flange etc.?
Here's what I reckon happened- The bladder burst so the pressure from compressor had a direct path into the vac bag. So it lost vacuum in the bag and the clamping force on the moulds disappeared. Air was still flowing into the bladder, I guess faster than it could escape, so the bladder blew up further pushing the moulds apart and the seam out through the gap. The vac bag was starting to inflate when I got into the shed and shut down the compressor

I'm still trying to come up with a solution as I really like the idea of being able to use low-tech moulds and still apply a reasonable amount of pressure to the layup. Maybe double-bagging might work. So if the bladder pops the moulds won't lose clamping pressure. I guess the inner bag would need to be ported to atmosphere so air can escape when the outer bag gets sucked down..... maybe.
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Old Nov 01, 2012, 09:54 PM
Just Toss It !!!
MATIN's Avatar
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A small suggestion here.......Go back and edit the thread name......Take out the "L-39"......Take out the "Low fat" ........Give it a new name......
It doesn't matter what the name is, you can call it an Emu for all I care!

It's a beautiful plane and it doesn't need to tow another planes name ..........

Oh!.....and put one in the mail for me....

Matin
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Old Nov 01, 2012, 09:56 PM
Alphabets make great soup
Hamburglar's Avatar
Australia, ACT, Canberra
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But in saying that..... the seam on the fuse I just pulled is fantastic. And that was just with the bladder ported to atmosphere.
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Old Nov 01, 2012, 09:58 PM
Alphabets make great soup
Hamburglar's Avatar
Australia, ACT, Canberra
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Quote:
Originally Posted by MATIN View Post
A small suggestion here.......Go back and edit the thread name......Take out the "L-39"......Take out the "Low fat" ........Give it a new name......
It doesn't matter what the name is, you can call it an Emu for all I care!

It's a beautiful plane and it doesn't need to tow another planes name ..........

Oh!.....and put one in the mail for me....

Matin
Yeah it's really not very L-39 is it?

Name suggestions anyone?
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Old Nov 01, 2012, 09:59 PM
Just Toss It !!!
MATIN's Avatar
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Emu....
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Old Nov 01, 2012, 09:59 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
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[QUOTE=Hamburglar;23160841]Here's what I reckon happened- The bladder burst so the pressure from compressor had a direct path into the vac bag. So it lost vacuum in the bag and the clamping force on the moulds disappeared. Air was still flowing into the bladder, I guess faster than it could escape, so the bladder blew up further pushing the moulds apart and the seam out through the gap. The vac bag was starting to inflate when I got into the shed and shut down the compressor

...............QUOTE]

Ahh! Now I see the meaning of post #133.

I'll have to have a long think about your "double bag" idea though. I've just caught up with your single bag method!
At times like this, I think I'm getting slow in my old age.

However, your plane looks simply fantastic Jordan! Well done. I can visualise it doing pumps on the western launch out at Borah already.

Jim.
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Last edited by Jim.Thompson; Nov 01, 2012 at 10:00 PM. Reason: italics
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Old Nov 01, 2012, 10:18 PM
Alphabets make great soup
Hamburglar's Avatar
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Still trying to get my head around the double bag thing too.... the more I think about it, the less I think it'll work as I'd like it too. I'm pretty sure the vac wouldn't inflate the bladder as it does with a single bag.
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Old Nov 01, 2012, 10:21 PM
Alphabets make great soup
Hamburglar's Avatar
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Quote:
Originally Posted by MATIN View Post
Emu....
Is that E-Moo or E-Mew?
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Old Nov 01, 2012, 10:24 PM
Just Toss It !!!
MATIN's Avatar
United States, CA, San Diego
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Quote:
Originally Posted by Hamburglar View Post
Is that E-Moo or E-Mew?
I guess it depends on the continent you live on!
You put down Emu, let them pronounce it however they want....
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