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Old Dec 30, 2010, 11:50 AM
del
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north of Chicago
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another covering source

Howdy,

For my light balsa stick models I use the mylar preferred by indoor Free Flight folks. It's available in sub-micron thicknesses.

It weighs next to nothing. But is more delicate and can be a bit of a pain to work with.

However it's the winner in the war on wing loading..

Here's a source:

http://www.a2zcorp.us/store/Category.asp?Cguid={6CA92284-61F5-4A3F-AF71-753D38782952}&Category=BuildingMaterials%3ACoverin g

--del
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Old Dec 30, 2010, 01:17 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Del,
Good point. I just added both the TLFilm and OSFilm that A2Z carries, and two other films they don't carry to my covering weight table. I also added a column with g/M2 (grams per square meter) to the table.

The OS Film weighs about 1/3 what the WES film from Homefly weighs. On larger planes like my Airbender that difference won't amount to much and is just rounding error. On tiny planes like Joe Malinchak's 4-in version of my DR-1 tripe the relative weight savings are a bit larger. I calculated the difference in weight between the two for Joe's tripe a couple weeks ago just out of curiosity. Below some point the weight savings from lighter and lighter covering films result in diminishing returns as a percentage of the total airplane weight. The big weight savings occur as a result of going from a solid sheet foam to a skeletonized structure and substituting a film that weighs 90% to 95% less than the foam that was cut out of the structure. In otherwords, substituting ANY film in place of heavy foam is where the action is.

My Airbender has 102 sq.in of wing area, a span of 18 inches, and a total weight of 19g. Let's call it 100 square inches for simplicity. The table below shows the weight of the coverings in my table up above for a 100 square inch wing. The covering weight for the WES 2um clear covering is a total of 0.14g, and if the OS Film is used instead the total covering weight for the wing declines to 0.05g, not much on a 19g plane. On the other hand, compared to Saran or Reynolds Wrap, the weight from the covering for the wing declines from 0.91g to 0.14g for the WES film. When I built the plane I estimated that I saved about 1.5g in weight by using the WES film instead of Reynolds Wrap.

It's all about tradeoffs.

Gordon
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Last edited by Gordon Johnson; Dec 30, 2010 at 02:45 PM.
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Old Dec 30, 2010, 02:12 PM
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Gordon can anyone post there plans here?
TODD
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Old Dec 30, 2010, 02:33 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Todd,
I don't see any reason why plans can't be posted in this thread, and it's probably a good idea. In my case I merely provided the link to the threads on my planes and noted if the thread had plans. Didn't make sense to me to post the plans a second time in two different threads.

Gordon
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Old Dec 30, 2010, 03:17 PM
ICU
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You wouldn't happen to know the weight savings % of using tissue paper, would you? I just ask cause it's just as easy to get as the saran wrap and is very cheap.

I used that on a small 3D foamie I built to fly around my shop at work. I only used it on the wings. But Skeletonizing the fuse and wings I prob saved somewhere in the neigborhood of 2-3 g on a 40g AUW plane. (using 3mm depron)
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Old Dec 30, 2010, 03:23 PM
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I've had this one but haven't tried it yet. Skeleton looks pretty wide compared to yours. Thought I'd put it here in case someone wanted to try it. Sorry don't have a PDF of it or a program or knowledge to use it.(yet) Looks like you beat me to the elevon plane with your Toon Jet.
TODD
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Old Dec 30, 2010, 03:30 PM
del
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That's right, Gordon,

Comparing the weight of the covering to the weight of the un-covered model is a good way to think about it.

Can we still get Y2K film? Last time I checked with Roy White he had no more.

And we shouldn't forget tissue. Even Gampi (the lightest I've found) is heavy in comparison to light mylar. However, adding color and markings with an ink jet printer is easy and would give skeleton models less of a skeleton appearance.

A2Z sells Gampi, as do several other on-line sources. I've recently had good luck ordering from:

http://www.fineartstore.com/

Search for gampi..

--del





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Old Dec 30, 2010, 05:17 PM
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Quote:
Originally Posted by Gordon Johnson View Post
Once you have a skeletonized airframe part, fuselage or wing, or tail, you need to cover it or skin it with something. The two main choices are some sort of mylar or film covering or thin foam. Here's a table with weights per square inch for various foams and covering materials. By combining these with a skeleton ratio of how much foam material can be removed in the skeletonizing process you can estimate your airframe parts weight and how much weight you have saved.

I'll work up an example later of how to go through this estimation process.

Skeleton Ratio content for this post to come later ...

Thanks for posting Gordie. I was thinking of doing up something in Depron and I was going to experiment with one skelton layer of 1mm depron and a skin of 1mm depron. But from your chart it looks to be no better than just using 2mm depron. I'll go the easy route.

bill
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Old Dec 30, 2010, 06:33 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Quote:
Originally Posted by ICU View Post
You wouldn't happen to know the weight savings % of using tissue paper, would you? I just ask cause it's just as easy to get as the saran wrap and is very cheap.

I used that on a small 3D foamie I built to fly around my shop at work. I only used it on the wings. But Skeletonizing the fuse and wings I prob saved somewhere in the neigborhood of 2-3 g on a 40g AUW plane. (using 3mm depron)
From the A2Z Corp website they list Gampi tissue as 12g M2, or slightly less than Reynolds Wrap. Other tissues from department stores etc aren't worth categorizing because they range from really light to really heavy. One just has to weigh their own when getting from non-hobby sources.

Gordon
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Old Dec 31, 2010, 12:43 AM
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Great idea

Thanks Gordon

Watching with keen interest
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Old Dec 31, 2010, 07:24 AM
Atleast It's in one piece
United Kingdom, North Weald Bassett
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Hi Guys
I came across this table of covering weights itís been posted before so I suppose itís all right to do it again


Arcright
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Old Dec 31, 2010, 08:13 PM
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Here is one of mine. It's only semi-original. I stared out with Bill Lowe's full size Ghost, and modified from there. The wings are pretty much stock Ghost. The fuse is a cut and pieced back together variation of the stock fuse. It actually flys pretty well. It's a bit underpowered as is so it doesn't 3d well, but it's nice and slow and for mild aerobatics it works just fine
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Last edited by Bugman Jeff; Dec 31, 2010 at 08:19 PM.
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Old Dec 31, 2010, 08:15 PM
I'm a Registered User
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Here's my other skeleton. It's also based on Bill's Ghost. It's a pretty simple wing, covered in reflective mylar. It's a bit floppy in the air, but it does fly. It's nice and slow, just needs some more reinforcment
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Old Jan 01, 2011, 12:40 AM
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Wow

Thats awesome

You have link to plans





Quote:
Originally Posted by Bugman Jeff View Post
Here is one of mine. It's only semi-original. I stared out with Bill Lowe's full size Ghost, and modified from there. The wings are pretty much stock Ghost. The fuse is a cut and pieced back together variation of the stock fuse. It actually flys pretty well. It's a bit underpowered as is so it doesn't 3d well, but it's nice and slow and for mild aerobatics it works just fine
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Old Jan 01, 2011, 06:51 AM
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Bugman that modified Ghost would make a really cool looking canard plane.
TODD
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