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Old Oct 25, 2011, 07:19 PM
Whisper Model Aircraft
heliwill10's Avatar
Greensburg, PA
Joined Feb 2008
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Pressure bladder with a wing pylon

I’m building a mold for a one piece fuse that has a pylon. Insides of pylons are normally hollow so, how do you incorporate a pressure bladder without blowing the thing out? My plug is just about done, so anything is up for grabs.

A friend and I have come up with two ideas’… Some kind of 3 piece mold (a drawing would be nice). Or some kind of molded insert to block off the opening. Trouble with that is the pylon would not get any benefits of the bladder.

Go slow, I’m still learning
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Old Oct 25, 2011, 09:41 PM
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Ward Hagaman's Avatar
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Are you making the bladder out of plastic sheeting? Maybe you can incorporate the pylon shape into that....
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Old Oct 25, 2011, 10:27 PM
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Jim.Thompson's Avatar
Bellingen NSW Australia
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As Ward says.
I would design the mould so that the pylon will be layed up with with wing seat intact. ie. the mould will be closed allowing the use of a bladder. If you go over to the inflation bladder thread, (which you may already have done), you will find lots of discussion on methods of heat "welding" plastic sheet to form a suitable bladder.
It might require a few attempts to get the bladder template just right, but is doable I think. I would try at least one sacrificial light layup to see if the bladder holds etc. before commiting to a full one with carbon reo etc.

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Old Oct 26, 2011, 07:34 AM
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I've been over to the bladder thread, started to make me crossed eyed. I'm going to make the bladder from the drop cloth so cutting the pylon shape shouldn't be a problem.

I like the wing saddle idea closing off the top. I’d have to come up with some way to make sure that is perpendicular to the vertical axis.

Still learning to think backwards
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Old Oct 26, 2011, 07:51 AM
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I use a silicone mold of my pylon (think DLG tail mount) and insert that on top of my wetted cloth in the pylon mold prior to adding the bladder. After the bladder is inflated, it pushes the silicone into the pylon. When you deflate and remove the bladder, you can pull the silicone mold out with hemos or needle nose and reuse it.
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Old Oct 26, 2011, 11:46 AM
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Im not sure I understand your description of a pylon however I managed to use a poly bladder with success then tried some with party balloons and they also work quite nice. The entry and exit of the pylon allowed the bladders to find a comfy home and seat into the cavity
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Old Oct 26, 2011, 11:54 AM
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Old Oct 26, 2011, 02:58 PM
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heliwill10's Avatar
Greensburg, PA
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Do you have a picture of this? What psi are you running? If I understand a high psi might pop the insert out?

Quote:
Originally Posted by tom43004 View Post
I use a silicone mold of my pylon (think DLG tail mount) and insert that on top of my wetted cloth in the pylon mold prior to adding the bladder. After the bladder is inflated, it pushes the silicone into the pylon. When you deflate and remove the bladder, you can pull the silicone mold out with hemos or needle nose and reuse it.
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Old Oct 26, 2011, 03:01 PM
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Greensburg, PA
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This is close to my pylon, except it has a wing saddle. My mold will have to split vertical.

Quote:
Originally Posted by DLGjunkyard View Post
Im not sure I understand your description of a pylon however I managed to use a poly bladder with success then tried some with party balloons and they also work quite nice. The entry and exit of the pylon allowed the bladders to find a comfy home and seat into the cavity
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Old Oct 26, 2011, 03:08 PM
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No, the insert goes into the pylon opening. More bladder pressure just presses it harder into the pylon opening.

My current molds don't have the mounts molded in so I don't think I have pics.
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Old Oct 26, 2011, 03:20 PM
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Bellingen NSW Australia
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Quote:
Originally Posted by tom43004 View Post
I use a silicone mold of my pylon (think DLG tail mount) .....................
I think you mean "plug" here Tom or "insert", not mould. Is that right?
I know the two terms plug and mould are often interchanged which can lead to some confusion.
I have used two pack silicone inserts to support the bladder successfully in the wing fillet/stubs of a fuselage for a two part wing moulded plane.


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Old Oct 26, 2011, 04:37 PM
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Insert is fine.
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