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Old Aug 28, 2009, 08:43 PM
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Greygoosegregg's Avatar
United States, CA, Simi Valley
Joined Feb 2008
258 Posts
According to the pump I have, 5 X 10-4 Torr is = to -29.36psi. I don't know, but that is what the pump data sheet claims...

Rotary Vane Pumps
Two Stage
5 X 10-4 Torr
0.5 Microns
800 litres/min.
28 CFM
48 m3/hour
Rotary Vane Pumps
Two Stage
5 X 10-4 Torr
0.5 Microns
200 litres/min.
7 CFM
12 m3/hour
3.5 CFM 7 CFM
21 CFM 28 CFM
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Old Aug 28, 2009, 08:59 PM
Registered User
Wichita Falls, TX
Joined Oct 2005
155 Posts
Quote:
Originally Posted by flyonline
after balancing the wings so that the CG of the WING is just ahead/on top of the pivot point you rebalance the entire PLANE so that it has the original CG before balancing the wings.
I had just assumed that the wing should pivot at the computed Neutral Point of the airframe. I had not considered that the mass of the wing, which depends how the wing is built, could affect the final placement.

Thank you.

Frank
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Old Aug 28, 2009, 09:01 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
Quote:
Originally Posted by Greygoosegregg
According to the pump I have, 5 X 10-4 Torr is = to -29.36psi. I don't know, but that is what the pump data sheet claims...

Rotary Vane Pumps
Two Stage
5 X 10-4 Torr
0.5 Microns
800 litres/min.
28 CFM
48 m3/hour
Rotary Vane Pumps
Two Stage
5 X 10-4 Torr
0.5 Microns
200 litres/min.
7 CFM
12 m3/hour
3.5 CFM 7 CFM
21 CFM 28 CFM
Vacuum Conversion Chart
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Old Aug 28, 2009, 09:03 PM
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Greygoosegregg's Avatar
United States, CA, Simi Valley
Joined Feb 2008
258 Posts
Ahhh.... I see. I did not understand until just now. Read up on the perfect vacuum. Like I said, first time. lol
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Old Aug 28, 2009, 09:08 PM
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Greygoosegregg's Avatar
United States, CA, Simi Valley
Joined Feb 2008
258 Posts
Anyway, I didn't even come close to that at 4 psi. Thanks of the lesson wyowindworks.
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Old Aug 28, 2009, 09:25 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
Quote:
Originally Posted by Greygoosegregg
Anyway, I didn't even come close to that at 4 psi. Thanks of the lesson wyowindworks.
I used to get them all mixed up too. I used to call them "atmospheres" which is psychotically off.

Adam
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Old Aug 29, 2009, 12:23 AM
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screamin' eagle's Avatar
Pacific Palisades, CA
Joined Jul 2004
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Reason I mentioned the vacuum level is because in some of the photos, it looks like the surface of the bagged wing is textured like the cloth. Ideally you want it pressed down flat, and 4 inches is hardly pulling a vacuum. I usually bag carbon over blue foam at about 18 inches and can go up to 24 inches without ill effects using 5.7 oz carbon twill.
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Old Aug 29, 2009, 01:50 AM
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flyonline's Avatar
Joined May 2003
4,353 Posts
Quote:
Originally Posted by Frank Jarratt
I had just assumed that the wing should pivot at the computed Neutral Point of the airframe. I had not considered that the mass of the wing, which depends how the wing is built, could affect the final placement.

Thank you.

Frank
Technically I think the wing should pivot on the NP of the wing (or tail for a FF stab) but as Adam pointed out earlier the NP changes with AOA for a cambered surface but for the low cambers we usually use I suspect it probably won't change to a large extent though I have no proof or formal knowledge on this - hence my decision to use the 25%MAC point as the wing CG.
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Old Aug 29, 2009, 04:09 AM
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United States, CA, Simi Valley
Joined Feb 2008
258 Posts
Quote:
Originally Posted by screamin' eagle
Reason I mentioned the vacuum level is because in some of the photos, it looks like the surface of the bagged wing is textured like the cloth. Ideally you want it pressed down flat, and 4 inches is hardly pulling a vacuum. I usually bag carbon over blue foam at about 18 inches and can go up to 24 inches without ill effects using 5.7 oz carbon twill.
Yea, The layup is textured. =( I was just afraid to crush or distort the wings. I wish I had known... My willingness to try new things, over shadow my experience. Live and learn. Maybe I'll start searching for a new set of wings or cut some new ones and re do them. Don't get me wrong, I'm gonna fly these, but I'd like to make them right. Thanks for the advise Screamin Eagle!!!
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Old Aug 29, 2009, 10:04 AM
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screamin' eagle's Avatar
Pacific Palisades, CA
Joined Jul 2004
9,253 Posts
I feel like kind of a pest with all my posts - I'm glad they are at least somewhat helpful. I think the plane will fly great irrespective of any bumps in the road...
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Old Aug 29, 2009, 03:21 PM
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United States, CA, Simi Valley
Joined Feb 2008
258 Posts
Hahaha Your not a pest at all. I really appreciate your experience, and great input. I definitely don't know it all, and am not afraid to ask for help. I should have posted the question about laying up the carbon fiber. Just a bit to anxious to get her done.

I put a light layer of glass over the carbon fiber. Should I attempt to sand it down and put a light coat of thinned resin over the wing to try and smooth it out? BTW, I'm sending you a PM.
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Old Aug 29, 2009, 03:28 PM
The Legend continues
CR_Aircraft's Avatar
Carlsbad, Calif
Joined May 2009
530 Posts
Nice looking plane Gregg,

Not sure we ever determined what your airfoil was,...could you post a profile picture of the wing root? Let's see if they used the RG15, 8020, 3016, 3021, etc...
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Old Aug 29, 2009, 03:54 PM
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United States, CA, Simi Valley
Joined Feb 2008
258 Posts
Quote:
Originally Posted by CR_Aircraft
Nice looking plane Gregg,

Not sure we ever determined what your airfoil was,...could you post a profile picture of the wing root? Let's see if they used the RG15, 8020, 3016, 3021, etc...
Hey CR Aircraft! Yea, It's no FG Turbo, but it's gonna look pretty good I think. I will post some pics of the root later tonight. I have my daughters this weekend, so trying to get some plane time in might be rough. lol I'll definitely have them post by Monday if not sooner.

Gregg
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Old Aug 30, 2009, 09:14 AM
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Sleedo's Avatar
USA, CT, Fairfield
Joined Jul 2004
2,600 Posts
A detail somewhere in my kit said E387, I have a different wing though-it is hollow molded FG.

Oh, re: vacuum level on the wings, I think less is more with these as from what I've seen they use very low density white EPS. Any more pull and you may have crushed the wings altogether.
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Old Aug 30, 2009, 11:24 AM
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screamin' eagle's Avatar
Pacific Palisades, CA
Joined Jul 2004
9,253 Posts
Quote:
Originally Posted by Sleedo
A detail somewhere in my kit said E387, I have a different wing though-it is hollow molded FG.

Oh, re: vacuum level on the wings, I think less is more with these as from what I've seen they use very low density white EPS. Any more pull and you may have crushed the wings altogether.
White foam is fine up to 12 inches - and am I imagining it or were these wings sheeted already? Ya need enough vacuum to pull the cloth flat!
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