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Old Dec 10, 2012, 11:16 PM
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Congress, AZ
Joined Sep 2001
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Sam,

It would be really tough for Doug to do tests now, in the winter. It hardly got above 72 today, in Phoenix

Couldn't resist.

Gary
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Old Dec 11, 2012, 01:19 AM
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ron gijzen's Avatar
Liempde, Netherlands
Joined Jul 2007
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[QUOTE=samc99us;23494801]... According to the ASTM standards, s glass contains twice as much aluminum oxide as e-glass. That would be a concern from an rf standpoint for sure, I use aluminum enclosures to block rf...QUOTE]

Aluminum oxide is not conductive, so I don't expect RF signals will be blocked.
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Old Dec 11, 2012, 09:54 AM
Composites guy
North OC, Ca.
Joined Jun 2005
1,172 Posts
S-2 glass is fine. Many structures are made from S-2 and it is electromagnetically transparent- nuff said.....

Aluminum oxide and aluminum metal are quite different.

S-2 is higher purity and more difficult to make= higher cost/higher performance.
Less heat cleaning typically when woven and some types are not heat cleaned at all to preserve strength.

Good strain to failure and impact/fatigue performance.

Just wish they had some in lighter weights for our use that was not a special order.....$$$$

Scott
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Old Dec 11, 2012, 09:57 AM
Composites guy
North OC, Ca.
Joined Jun 2005
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Astroquarts is still used for radomes for those applications that can afford it. $^3.
Scott
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Old Dec 11, 2012, 09:58 AM
G_T
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E glass is for electrical insulation. S glass is structural, and more expensive to produce. Those are the two common glass fibers. Quartz, and various others, are hard to find. A light thin weight quartz cloth would be excellent, if one existed.

Gerald

(Fast posting this morning! Mine is redundant)
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Old Dec 11, 2012, 10:01 AM
Composites guy
North OC, Ca.
Joined Jun 2005
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Doug-
If structure weight and crush/oil can resistance is an issue, you may consider and internal iso-grid design where you take some of the skin thickness and convert that into internal ribs so that the wall thickness "appears" thicker than it is. Stiffness is a cubic function of the wall thickness and iso-grids and sandwich structures are easy ways to get this effect.
I made 1 sloper with a sandwich body where the inner shell was spaced using a Rohacell spacer from the outer body- worked great- came out too light( needed ballast all the time).
clear?

Cheers,
Scott
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Old Dec 11, 2012, 10:23 AM
G_T
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The fuselage of the Fireworks 5 Flo does this, and perhaps some others do as well.

Gerald
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Old Dec 11, 2012, 11:00 AM
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Glendale,Az.
Joined Oct 2004
3,532 Posts
The strength is no the issue with the conventional layups, it is the beautifully poor design and surface area from the canopy back to the boom end. I designed it and will have to modifye layups and fabric placement and type to get in the 48-50 g range. I will try the 1 ounce kev with the 4.1 hm uni next, need to find some reasonable first.

Thanks for everyones help.

Doug

55g is easy.
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Old Dec 11, 2012, 09:32 PM
Aurora Builder
United States, MD, Lusby
Joined Nov 2003
3,408 Posts
Gary, sometimes the details slip through.

Doug, good luck, I apologize for not taking a closer look at this before the molds were cut. A 48g fuselage is still very nice!
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Old Dec 11, 2012, 10:40 PM
dougmontgomery's Avatar
Glendale,Az.
Joined Oct 2004
3,532 Posts
Sam,
At least the molds will last forever......and slope guys love me!!!!

It is not really that big of deal because I really just like building, I can make this work for me and it is equivalent to a couple of Concepts.

this is more enjoyable to me then just competing with a store bought model.

I pick up my Veloxcnc when we are at the Jem next month so I should be good.

doug
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Old Dec 16, 2012, 01:35 PM
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Glendale,Az.
Joined Oct 2004
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Quote:
Originally Posted by sarmoby View Post
Doug-
If structure weight and crush/oil can resistance is an issue, you may consider and internal iso-grid design where you take some of the skin thickness and convert that into internal ribs so that the wall thickness "appears" thicker than it is. Stiffness is a cubic function of the wall thickness and iso-grids and sandwich structures are easy ways to get this effect.
I made 1 sloper with a sandwich body where the inner shell was spaced using a Rohacell spacer from the outer body- worked great- came out too light( needed ballast all the time).
clear?

Cheers,
Scott

Scott, I did a couple tests with 1mm depron strips down each side, tapered.

They are super strong with minimal cloth, the second test I ran the depron dart into the front canopy region, this made for a super strong front front area.

I do like this method though it is more challenging to get placement and no movement of the depron when closing the mold.

I also do no know if the depron is corking my seam and not allowing all the excess epoxy out before I close the mold.

doug
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Old Dec 16, 2012, 11:11 PM
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There shouldn't be as problem there as the bladder is pushing against the depron as well as the fabric.
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Old Dec 18, 2012, 02:19 AM
Meek A Mouse
Deutschland, BW, Stuttgart
Joined Aug 2004
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Source: AGY
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Old Dec 20, 2012, 06:26 PM
Composites guy
North OC, Ca.
Joined Jun 2005
1,172 Posts
Gideon-
room temp, 9.4 ghz- Astro quartz II- dielectric (Dk) is 3.78 for comparison- from the JPS manual( public domain)

Doug-
The depron is similar to the Rohacell and I understand your comments about positioning...

Still a cool way to stiffen with less fabric.

You may consider a braid or twisted tow as a "wall thickener" to increase stiffness without weight increase of the entire skin. Sometimes easier said than done.

Have you weighed the dry fabric and compared to the final airframe? This can give you a rough idea of the resin content you achieve.

BTW- some of my slopers have Pushrods that weigh more that 50g....

Cheers,
scott
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Old Dec 20, 2012, 06:30 PM
Composites guy
North OC, Ca.
Joined Jun 2005
1,172 Posts
Doug-
the only other thing that comes to mind is to put a porous armalon( teflon coated fiberglass) and bleeder material adjacent to the bladder to scavenge any excess resin. Peeling those out of a stick-like fuse may be tough but would would be suprised how much resin can be pulled out when the resin viscosity is really low.
One time I did this with a envelope bag in an oven cure- made myself an airplane shapped bleeder- could have put that together and flown it.
Scott
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