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Dec 14, 2011, 12:22 PM
An itch?. Scratch build.
eflightray's Avatar
A good few years ago there appeared a small article in one of the model mags on covering using 'nylons',.........that's nylons as in a pair of nylon stockings or tights.

The idea was to use a stocking, (or one leg of a pair of tights), as a complete nylon sleeve to slip over a wing or fuselage. The material design made it ideal for fitting a tapered wing all in one go, or a fuselage that doesn't have any convex curves. Though I believe even that can be done using one of the spay on adhesives first to bond the nylon into the curve.

The 'material' is probably one of the lightest, depending on the 'denier' chosen, (not your Gran's old thick wrinkly ones ).
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Dec 14, 2011, 12:46 PM
IAMCANADIAN
Grejen's Avatar
Quote:
Originally Posted by vtdiy
You can't just predict weight based on glue and paper choices. Various papers have different thicknesses, finishes, fillers, and absorption rates,for the final finish materials. When you add the filler coats and paint coat, you can add as much weight as the paper and glue sometimes, depending on the paper thickness and absorption, glue, etc. Your methods and desired finish will be different than hoppy's

If you want to predict weights, you need to not only glue paper down, but finish to whatever level you like, using whatever method you like (sanding between coats?, how much?, polycrylic? talcum?, acrylic finish?, enamel?, lacquer? number of coats? etc.) and do that the same for two samples you want to compare.

Comparing your results with different kinds of coverings to hoppy's won't mean much unless you finish each, the same way, with the same materials to the same degree of opacity and shine. Then the practical weight difference can be seen.

Two guys finishing the same tissue covered balsa model, using the same finish, dope, can come out with greatly different model weights.
Hmm.. all that plus we each have to consider what sort of mess and odors we like to (or don't like to) deal with in our workshop and the time and skill level involved with each method.
Dec 14, 2011, 01:14 PM
Registered User
Quote:
Originally Posted by Grejen
Hmm.. all that plus we each have to consider what sort of mess and odors we like to (or don't like to) deal with in our workshop and the time and skill level involved with each method.
Those are very important considerations. I'd add cost and availability of materials too. Every material and method has it's advantages and disadvantages.

At some point you have to find a system that works for you and get good at using that material and method. There is no magic bullet.......
Dec 14, 2011, 02:07 PM
Vertical approach specialist
potshot's Avatar
Quote:
Originally Posted by pmullen503
...At some point you have to find a system that works for you and get good at using that material and method. There is no magic bullet.......
Wow, great answer, pmullen503. This could apply to so many things we do. It settles all the arguments about which method of <name the issue> is best.
Dec 14, 2011, 03:01 PM
Space Coast USA
hoppy's Avatar
Quote:
Originally Posted by pmullen503
Here are some of the weights I've recorded for various coverings and materials (YMMV). Sometimes I'll use several materials on the same airplane in different areas. When I use paper, I apply it wet with WBPU. Generally, I'll use FG on compound curves (fuselage), paper on wings. Lately, I've been using liquid sheeting II (Styrospray 1000) for certain things with some success.

I'm building scale models, not flat foamies and tend to favor durability and quality of painted finish over absolute lightest covering.

Units are gram/square foot, one surface covered unless otherwise stated, covering ready to paint.

The "light" brown paper is very similar to newsprint, the "heavy" is more like a grocery bag.

covering g/ftsq
1/16" Balsa 21
FFF` 19
DT Foam 12

Brown paper (heavy)+wbpu 20
(light) brown+ Poly 11
Thanks for the info.
The DT is $T foam? I got 18g/sqft, with the paper covering torn off dry.
I'm surprised at the difference. Did you remove the paper dry or with a solvent?

Regarding the adhesive/covering, can I assume the light brown paper/Poly (polycrylic?) adds 11g or 23g/sqft on $T foam?
Dec 14, 2011, 04:27 PM
Registered User
Quote:
Originally Posted by hoppy
Thanks for the info.
The DT is $T foam? I got 18g/sqft, with the paper covering torn off dry.
I'm surprised at the difference. Did you remove the paper dry or with a solvent?

Regarding the adhesive/covering, can I assume the light brown paper/Poly (polycrylic?) adds 11g or 23g/sqft on $T foam?
I grabbed these numbers from a spreadsheet I made to predict the weight of proposed projects. I just plug in the areas from a CAD program of the various assemblies and it predicts the weights. It's also the numbers *I* get, yours may vary. Those weights are based on multiple builds and there is always a range: say, +/- 10-20%

I remove foam board paper by spraying with $tree's cleaner (can't recall the name) and then soaking it with water. The spray cleaner just helps wet it thoroughly and the paper will fall off in a few minutes. Leaves a smoother surface than dry peeling.

Foam can vary in thickness or density. My DT foam all came from the same case I got a year or two ago so that may explain why mine is lighter. I suspect the specs on DT foam board are pretty broad.

Within maybe +/- 20% the numbers are additive. Your example is correct, DT foam (12g) covered one side with light kraft paper and poly (11g) should weigh around 23g/ft^2. Surface prep, precoating, whether the finished surface will be painted flat or glossy all make a difference in weight added.

My light kraft paper is 30lb basis weight, the heavy is 60lb (IIFC). Basis weights are not always comparable between paper types (Kraft and newsprint are so, 30lb kraft weighs the same 30lb newsprint).
Dec 14, 2011, 05:17 PM
Space Coast USA
hoppy's Avatar
If you still have some $T with the paper on, it would be interesting to see what the weight difference is between dry and wet stripping of the same material lot. I've stripped all of mine or I would do it.
Dec 14, 2011, 05:51 PM
RC Adddict
Wilfor's Avatar
Quote:
Originally Posted by eflightray
A good few years ago there appeared a small article in one of the model mags on covering using 'nylons',.........that's nylons as in a pair of nylon stockings or tights.

The idea was to use a stocking, (or one leg of a pair of tights), as a complete nylon sleeve to slip over a wing or fuselage. The material design made it ideal for fitting a tapered wing all in one go, or a fuselage that doesn't have any convex curves. Though I believe even that can be done using one of the spay on adhesives first to bond the nylon into the curve.

The 'material' is probably one of the lightest, depending on the 'denier' chosen, (not your Gran's old thick wrinkly ones ).
I just picked up a pair last week at a dollar store and cut 1 leg off to try on the mustang wing im doing . Seems light enough just have to decide what to use with it .
Dec 14, 2011, 06:49 PM
low tech high tech
vtdiy's Avatar
Just another (I hope) interesting point about fabrics -- nylon is VERY elastic compared with silk or dacron, or paper. Therefore it adds far less stiffness as a covering material. Its elsaticity is exactly why it is used for stockings. It doesn't wrinkle on compound curves, but adds little stiffness to the structure, so to speak.

As I mentioned elsewhere, on boats, nylon line is only used for an anchor rode. Dacron is the preferred material for all other running lines because of its limited stretch, by comparison.

Nylon is so stretchy, that, if you use it in a lamination (as we are in covering), chances are that it is more flexible than the the glue it is set in, or the foam it covers. As a result, when the part is stressed, the nylon takes very little of the load, the glue will probably be taking most of it. Likewise in an impact, the blow will not break the nylon, but will transfer through and crush the foam under. Nylon will hold it together afterwards, but the dent will remain where a stiffer shell might have deflected less and prevented a dent.

Dacron coat lining material is a better lower stretch covering material for larger planes. Also available at most fabric shops and WalMart.

I'm leaning toward paper myself as a covering, however, for all the reasons Hoppy has already listed. It's a nice hard easily finished coating, that adds great stiffness and impact resistance.
Dec 18, 2011, 02:07 AM
Registered User
mintie's Avatar
Here is my latest depron ,white foam and paper model.
details can be seen here
https://www.rcgroups.com/forums/show....php?t=1537554
I have used news print as a covering medium for a number of years now on nitro models and have now started using on e power models.
The orginal was all balsa and finished wt was 900 gms
This build finished at 514gms.
News print is a good cheap and strong covering material.
Dec 18, 2011, 06:35 AM
RMS
RMS
Registered User
RMS's Avatar
Quote:
Originally Posted by eflightray
A good few years ago there appeared a small article in one of the model mags on covering using 'nylons',.........that's nylons as in a pair of nylon stockings or tights.

The idea was to use a stocking, (or one leg of a pair of tights), as a complete nylon sleeve to slip over a wing or fuselage. The material design made it ideal for fitting a tapered wing all in one go, or a fuselage that doesn't have any convex curves. Though I believe even that can be done using one of the spay on adhesives first to bond the nylon into the curve.

The 'material' is probably one of the lightest, depending on the 'denier' chosen, (not your Gran's old thick wrinkly ones ).
That does work. When I read that article, I tried it on my Midwest Chipmunk .15 to .25 size foamy. I used two layers.
Jan 08, 2012, 04:54 PM
Registered User

Newsprint+WBPU on Pusher nose


I've tried adding white newsprint from packing to the nose of a blue foam pusher I'm building. The nose is an irregular triangle shape about 8 inches wide by 7 inches high. I've covered both sides and a strip about 1 inch wide on the edge. The shape is pictured below. I figure it adds up to about 0.5 sq feet. I used "Deft" water based polyurethane varnish to stick the paper down, and I soaked it from the top also.

The coating added 9 grams to the nose which isn't bad for a 500-600 gram plane. This calculates to about 18 grams per square foot, and isn't much different than the value recently posted. I need the weight up front, since these pushers are pretty tail heay.

I'll be adding of color coat of Krylon H2O acrylic spray paint over it. I added a coat of red to the tail over WBPU primer, and it's a lot bumpier than the nose. I didn't want to use paper back there, since I need to keep the weight down.
Jan 14, 2012, 09:58 AM
Registered User
EdSoars's Avatar
Mintie, nice motor glider!

Are your control surfaces made from balsa, or did you take the paper-over-foam all the way to a thin TE? I'm building non-scale slope/thermal gliders, and would like to produce a very thin TE, as thick TE's can degrade airfoil performance. My tests so far have been mixed, with some gently curved, some wrinkled. I take the foam out to nearly zero thickness, and connect the top and bottom paper directly to each other on a 3/16" overlap past the foam. Maybe I need to bite the bullet and build a long clamp out of strip balsa or spruce instead of hoping that just drying both sides at once will work.

Has anyone else done very thin, very straight TE's??
Feb 18, 2012, 02:21 AM
Registered User
mintie's Avatar
Quote:
Originally Posted by EdSoars
Mintie, nice motor glider!

Are your control surfaces made from balsa, or did you take the paper-over-foam all the way to a thin TE? I'm building non-scale slope/thermal gliders, and would like to produce a very thin TE, as thick TE's can degrade airfoil performance. My tests so far have been mixed, with some gently curved, some wrinkled. I take the foam out to nearly zero thickness, and connect the top and bottom paper directly to each other on a 3/16" overlap past the foam. Maybe I need to bite the bullet and build a long clamp out of strip balsa or spruce instead of hoping that just drying both sides at once will work.

Has anyone else done very thin, very straight TE's??
sorry for the delay on your question.
My complete wing is foam right out and including the T/E ... NO balsa at all.
The finished aileron is nice and straight.
Feb 28, 2012, 12:01 PM
Racquetball Lives!
Backwall's Avatar

My two cents worth


I admit newsprint is pretty light and absorbent, but someone (don't remember who) told me to try an old telephone book (the white pages). Seemed lighter, but maybe that was just ink weight. Anyway, I cut 1" strips and prewet the foam surface with WBPU, laid down the strip and with my still damp (just barely) WPBU brush, I brushed down the strip of paper until it looked like it had picked up the WBPU from below. You do have to go back afterwards and sand to get a smooth finish. Just be careful and don't sand all the way through or you'll rough up the paper. I also found some rolls of brown paint masking paper at Lowes that seemed to weigh close to newsprint. I applied it with the same method but wasn't as pleased as it wrinkled up a bit. However, the next day, after it had dried out, it had regained much of its original shape. After sanding, as above, it worked out okay. I had applied it in bigger pieces and next time would probably cut it into small strips just like the phone book. After sanding, the WBPU felt pretty smooth and the foam could now take enamel paints as well. These paints (at least in the airbrush quality ones), go on lighter, smoother, and seem to have a better sheen than the acrylic airbrush paints. And it was all made possible with the phone book and WBPU. It also seems to add strength to those foams applied in the 3mm and 6mm thicknesses.

Dave


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