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Dec 08, 2011, 05:31 PM
Flying high
billwhit's Avatar
I use Polycrylic and coffee filters to cover my planes. The filters don't shrink when it dries so I haven't experienced warping of parts and I've covered at least 8 planes this way. It makes me wonder if the unprinted newspaper would be the same using polycrylic? I guess it depends on if it's the nature of the paper or if it's the water causing the shrinking...
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Dec 08, 2011, 06:04 PM
Space Coast USA
hoppy's Avatar
I'm sure it's the nature of the paper. Newspaper and paper bags can be "stretched" when wet which allows them to form to slightly curved surfaces. The paper shrinks when it dries causing warps if not done on both sides or held in a flat position with weights. When I use to do one side at a time, I'd put the wet side up with several weights on the corners. As it dried, I'd move the weights a bit so the wet part could dry.
Dec 08, 2011, 07:30 PM
Flying high
billwhit's Avatar
Hmmmm, maybe I'll have to try a combo next time. Filters for the flat surfaces and newsprint for the curved areas...
Dec 08, 2011, 08:34 PM
Space Coast USA
hoppy's Avatar
I spend more time trying different things on scrap foam then I do building.

Back in 2002, I was experimenting with Aleens Stretchable-Flexible glue (now avaialable at Michaels). https://www.rcgroups.com/forums/show...threadid=59805

It has the advantage of also being heat activated. Going over the surface with an iron really makes it stick.

Most any stuff works if the surface is lightly sanded and wiped with IPA before applying the glue.

I tried Freezer Wrap, the heavy stuff with that very slick plastic finish, applied with the Aleens F/S glue. Gives a really nice surface which can be painted for a monocoat type of finish.

I'll weigh my WACO wings tomorrow and report on the weight of the finished wing.
Dec 09, 2011, 06:02 AM
Vertical approach specialist
potshot's Avatar

Tulle anyone?


Has anyone used tulle (or toule)? It's a very fine, light netting found in fabric stores. It's fairly light, inexpensive and seems to conform to compound shapes. I have some but haven't decided what kind of liquid to apply it with. Maybe the 50/50 glue or Polycrylic woud be a place to start.
Dec 09, 2011, 08:23 AM
Space Coast USA
hoppy's Avatar
Sounds good potshot. Give it a test and let us know how they compare.
My test method is to take a piece of foam about 2x12" and apply 2" test pieces next to each other. After drying, pull the test piece off and see how hard it is to remove and if it takes a lot of foam off with it. If the test piece comes off with a white coating on it or tears it's a winner.

If you have the time I'd like to see you run a test like I did in the OP. The piece I used was $Tree foam about 7x7" and see how well the tulle stiffens the foam. I was just looking at the cost of that stuff....YIKES, cheap and in colors.
Dec 09, 2011, 09:02 AM
Space Coast USA
hoppy's Avatar
As promised, I weighed my WACO top wing.

Weight of wing covered with newsprint paper and painted is 4.5 oz.
Its a symmetrical wing with $Tree foam on the top and bottom, a foam main spar with a 6mm carbon fiber tube inside of it, and ailerons which are also made from 2 pieces of foam.

Wing is 48" with an 8" chord, 384 sq in and weighs 4.5oz.
That figures out to 2.6 oz/sq ft.
Dec 09, 2011, 09:22 AM
Flying low is expensive.
pdiddyg40's Avatar
I'm looking to cover the bottom of my skywalker to help with ding resistance. I know that polycrylic dries clear, but is there any material that I could use a a covering that dries clear asl well?

Thanks, guys!
-P.D.
Dec 09, 2011, 09:36 AM
Registered User
larryross,

Your remarks re Dollar Tree paper-covered foam clearly show that you have a lot more experience with it than I do.

Thank you much.

Jim R.
Dec 09, 2011, 09:55 AM
Space Coast USA
hoppy's Avatar
Quote:
Originally Posted by pdiddyg40
I'm looking to cover the bottom of my skywalker to help with ding resistance. I know that polycrylic dries clear, but is there any material that I could use a a covering that dries clear asl well?

Thanks, guys!
-P.D.
My favorite clear covering is Frost King packing tape form $Tree. It is very thin and very sticky. Be sure to clean surface with isopropyl alcohol before applying any coating. The oil from fingers/etc can prevent a good adhesion. The tape will also make the structure much stronger with little weight gain.
Dec 09, 2011, 10:16 AM
I used to like trees
rchank's Avatar
Quote:
Originally Posted by potshot
Has anyone used tulle (or toule)? It's a very fine, light netting found in fabric stores. It's fairly light, inexpensive and seems to conform to compound shapes. I have some but haven't decided what kind of liquid to apply it with. Maybe the 50/50 glue or Polycrylic woud be a place to start.
Here's a post on the use of tulle.

https://www.rcgroups.com/forums/show...&postcount=369
Dec 09, 2011, 10:19 AM
Vertical approach specialist
potshot's Avatar
Quote:
Originally Posted by hoppy
...Give it a test and let us know how they compare...
Yeah, I'll try it with Polycrylic and 50/50 water-glue. May be a few days 'til I get to it, but I'll report.

What I'm hoping for is that it will be light enough to put on both sides of blucor or Readi board for a super stiff laminate.
Dec 09, 2011, 11:29 AM
just Some Useless Geek
hoppy, et al: We appreciate you guys doing research on what makes foam stiffer, stronger, etc. Knowing the after-process weight of parts is good, but we also need to know the before process mass to have a comparison. When I weighed Owens-Corning Pink versus Dow PB III (with film) I found them to be almost identical at about 20 grams per square foot. Depron is just a few percent heavier. When peeled Pink comes out nearly three grams lighter, but PB III is only down a gram.

So, if we can know what this stuff weighs once any particular finishing material is applied then we have a basis of comparison. Knowing what hoppy started with versus what he ended up with lets us know what we can expect. I'd like to be able to calculate ahead of time what a plane will weigh so I know what motor to use, what servos, what battery size, yada yada yada. If I am dealing with straight-up Depron or FFF I can tell how heavy the thing will be just based in its surface area. If I'm adding strengthening materials I can't know the final weight [shovelmode] unless one of you kind, generous, resourceful people is nice enough to tell me [/shovelmode].

-- Marty, scratching head and shrugging shoulders --
Dec 09, 2011, 11:38 AM
Flying high
billwhit's Avatar
If it helps at all, I just covered my Redi-Jet Sport with the Polycrylic and coffee filters. I know this isn't an extremely popular method, but it's what I do. Anyway, this 25" WS jet gained about 2 oz from the covering. Also, the Filters become transparent once applied. The photo attached is fully covered.
Dec 09, 2011, 12:13 PM
I used to like trees
rchank's Avatar
Quote:
Originally Posted by billwhit
If it helps at all, I just covered my Redi-Jet Sport with the Polycrylic and coffee filters. I know this isn't an extremely popular method, but it's what I do. Anyway, this 25" WS jet gained about 2 oz from the covering. Also, the Filters become transparent once applied. The photo attached is fully covered.
Looks good Bill. How do the filters work in an area with a compound curve?


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