Fabric and finish weights

Discussion in 'Tube and Fabric' started by fly2kads, Jun 17, 2016.

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1. Jun 17, 2016

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One question that comes up from time to time is how to estimate the weights of aircraft fabric finishes. I was going through my copy of K. D. Wood's Airplane Design (eighth edition, 1947), and found the following data. I thought I'd post this here for comment and reference.

 Airplane Cloth, Merc. Cotton lbs./sq. ft. Grade A (all but 90" widths) .028 Grade A (90" widths) .031 Grade B (all but 90" widths) .031 Grade B (90" widths) .033

 Coating lbs./sq. ft. Clear nitrate dope .0052 - .0076 Pigmented dope .0056 - .0083 Lacquers .0056 - .0090 Synthetic enamels .0049 - .0069 Primers .0035 - .0069

Fabric and Dope
The approximate weight of fabric, tape, dope finishing material, and attaching parts as used in control surface covering varies from .070 lbs./sq. ft. of fabric area.
___________________________

Not too many people are finishing their aircraft in Grade A and dope these days, but I thought this would still serve as an interesting historical reference, one that might serve as a decent starting point for estimation.

Adding some more modern references, here are the Ceconite fabrics presented in the same format.

 Ceconite fabric lbs./sq. ft. 102-5 (standard weight) .019 101-4 (heavy duty) .024 Uncertified light .013

I haven't seen anything definitive about the weights of more modern finishes, such as Poly Fiber, Stewart, etc. I have seen comments to the effect that the total weight of all required coats wind up being roughly the same for the different systems, as there is a certain mil thickness required to fill the fabric weave and present a nice finish, regardless of the thickness of the individual coats. The assumption is that more coats of thinner dope vs. fewer coats of modern synthetic chemicals still wind up about the same mil thickness and weight in the end. I'd be interested in seeing some actual data to back that up.

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Added 6/17/16: Poly Fiber completed weights, from Poly Fiber via Rockiedog2

 Poly Fiber, Medium 5, fully finished lbs./sq. ft. Polyspray .063 Polytone .069 Aerothane .076

Last edited: Jun 17, 2016
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2. Jun 17, 2016

BBerson

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So, after about three coats the coating weighs more than the Dacron fabric. (Light fabric)

3. Jun 17, 2016

TFF

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The Polyfiber manual uses a Cub as weight change example. Polyfiber system is something like 25 lbs less than cotton/ dope. Cotton absorbs the dope. Dacron it just attaches. Stewarts is probably the heaviest modern. Polyfiber is mid and Dope on Ceconite/Dacron can be lightest of not going for super smooth polished look. The smoother and glossier you want it, the heavier it gets for all processes.

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4. Jun 17, 2016

Them

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Interesting numbers. I hope the following is a useful addition:

Oratex claims that their UL600 covering is 0.019-0.025 pounds per square foot, and their heavy duty 6000 cloth is 0.029-0.032 lbs/ft2, completely finished (color included).

For an "independent verification" they quote Bob Barrows (of Bearhawk fame) as saying that, measuring three identical size test panels with Oratex 6000, Ceconite with "light coatings", and Ceconite with "normal" coatings, they came up with weights of 12gm, 20gm, and 30gm respectively.

They don't say exactly what the size of those panels is but - if we believe the numbers - that would mean finished Ceconite would weigh 1.67 times more with "light" coatings, and 2.5 times more with "normal" coatings. So finished (including color paint) Ceconite weights would be 0.048-0.053lb/ft2 with "light" coatings and 0.07-0.08lb/ft2 with "normal" coatings.

I don't have any cross-check on those numbers so the usual warnings apply.

5. Jun 17, 2016

N8053H

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I would like to have seen the Stewards System in this comparison using the ecko-fill as the final finish with no paint applied.

6. Jun 17, 2016

N8053H

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I purchased a Legal Eagle built by an aeronautical engineer for Boeing. This Legal Eagle had folding wings and a center fuel tank and weighed 240 lbs. He used the Stewards system ecko-fill for the final finish. He said he did this to save weight.

7. Jun 17, 2016

Rockiedog2

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This from Greg at Polyfiber.
weight of 2.7oz fabric cover job. (that's the medium weight that most "real" planes get; non UL)

9 oz sq yd Polyspray only finish
10 oz sq yd Polytone finish
11 oz sq yd Aerothane finish.
That includes all finish tapes, rib lacing, reinforcing patches etc etc

So looking at reply #4 above with the Oratex weights for their 6000 fabric
.032 #/sq ft x 9sq ft is .288# x 16oz is 4.6 oz sq yard or about half the Polyfiber weight. Pretty big around here.
do we know if their weight includes the weight of rib lacing, tapes, patches etc?
And do we know how the cost compares to a PF cover job?

I looked at it when it first came out and didn't like the look of it. Not traditional looking. Think I'll look at it again if I make OSH

8. Jun 17, 2016

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Good info! Putting that into the same format as above, we get:

 Poly Fiber, Medium 5, fully finished lbs./sq. ft. Polyspray .063 Polytone .069 Aerothane .076

That's in pretty close agreement to the figure of .070 that Wood listed for a completed dope finish.

I am not certain, but I think the Oratex figures are for the fabric alone. Since the process still calls for rib stitching and tapes (or screws, or clips, etc.), that would have to be factored in to get a true apples-to-apples comparison for the total finished product. Still pretty promising, though. I have not had a chance to compare the strength figures for Oratex to those of Ceconite to see how they compare. I was wondering if they were starting with the same ultralight and medium weight fabrics, and running them through their proprietary sausage grinder. I haven't seen Oratex in person yet. I am familiar with the comparable products that have been available for model airplanes for years, and I wasn't crazy about how it looked; the texture was different, and the seams had a "hard" edge to them. I'd like to see the new aviation product in person.

9. Jun 17, 2016

Dana

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It's "Stewart", not "Steward". I wouldn't think you'd want to stop with only the Ekofill, as it's really only a primer.

A lot of people (I'm not one of them) don't like the appearance of Oratex, but remember itcan still be painted. Even painted, it'd still probably be lighter than other systems with fill coats, etc.

Dana

10. Jun 17, 2016

BBerson

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Just use half the coatings and get the same look and weight of Oratex.

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11. Jun 17, 2016

TFF

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A process is only a process if you fully follow the instructions. Stopping at ecofil Stewarts is probably pretty light as the heavy comes form the Polyurethane paint which is also the weather protection. For UL planes Stits/Polyfiber says to put a coat or two of pink and go straight to 2 coats of Polytone Silver and you are done. It will not be glass smooth, has about 80% of UV protection, and if you don't like silver, you will not like the color. That is an elimination of 5 coats of product though. My Starduster hopefully will be lighter as I am doing a take on UL Stits instructions. Normal application of the pink, but I am using Silver Polytone as the top coat so I am eliminating one of each coat of polytone and polyspray. Not a show plane and if I just hate it, there is plenty of silver to sand back and paint it all red.

12. Jun 17, 2016

Rockiedog2

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When talking to Greg I specified a minimum cover job meaning just what the manual calls for and no more. So the weights I quoted have already been cut down to min required to bond the tapes and patches and stop the UV. that's one brush coat of polybrush and 2 sprayed coats(I actually use one) and 3x coats of Polyspray. No Polytone required or used on mine. I don't know where we'd cut any of the coatings and still have a proper job of it. And it still won't look like Oratex which to me has a funky look. I've been using that PolyFiber job for about 40 years on my panes and I don't much think I'm gonna be able to like the Oratex. That stuff looks like it's for those Millenials to me. LOL.

On my Legal Eagle I did one brush coat of Polybrush, 2 xcoats of Polyspray on top of the wings and one xcoat of Polyspray on the bottom of the wings. Casual use extra weight sensitive plane...It wouldn't last long outside.

13. Jun 17, 2016

Them

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For Oratex two layers = 2x the weight, whereas with Ceconite or the like 2 layers = 2 times the cloth weight + ? times the finish weight. If it is the same finish weight Oratex and Ceconite would be a wash. If the finish weight doubles with the cloth weight, you'd have a weight savings. I think lacings are a wash from what I understood in email and phone conversations, but my plane doesn't use 'em.

Materials are a lot more expensive. $75 per square yard. If you are an expert with Ceconite you probably won't see the time gains that are half their argument, so it comes down to weight. They claim materials cost about$5000 to cover a SuperCub with Otatex. How does that compare to covering and painting normally?

Here's how much of a noob I am on this: Aircraft Spruce has a listing of materials needed to cover and finish a Ceconite-covered ultralight. Cloth, chemicals, paint. I priced everything out on that list and came up to $2500. Yet I see other ultralight vendors offering to sell everything needed to Ceconite their ultralights for$500. Oratex has estimated anywhere from $2700 up into the$3500 range (depending on a few choices like premade tapes vs DIY, tool choices, etc.) for my plane, but hasn't given me a final quote yet.

I'm almost certainly using Oratex because of the weight and because I don't particularly like painting (it brings out my neurotic perfectionist side like almost nothing else)

I doubt you'll like it better now. The 600 (ultralight) cloth I'm planning on using is basically transparent.

The US Oratex distributor lists the following figures for Oratex 6000 and Ceconite 101:

 Oratex 6000 Ceconite 101 Material Polyester Fabric Covering Polyester Fabric Covering Mass per unit area (there is a note that this is the cloth PRE-coating. Finished Oratex is 140g-160g) 98.7g 110.41g Maximum force: warp/weft 1613.3 N / 1412.10 N 792.59 N / 1353.73 N Elongation at max force: warp/weft 20.50% / 18.10% 41.14% / 23.34% Tear Strength: Warp/weft 80.50 N / 74.30 N 57.30 N / 31.65 N Bursting Pressure / Bursting distention > 750 kPa / >4.80 mm 778.60 kPa / 24.5 mm Shrinkage warp/weft (170c) 13.5% / 10.0% 13.2% / 15.0% Burning Behavior Incombustible Incombustible
Obviously that is metric so Grams, Newtons, Millimeters, etc., but should give you an idea.

14. Jun 17, 2016

N8053H

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Everyone that I know who fly an EAB do not let said EAB sit out in the weather let alone any Ultralight. So weather protection is really not an issue. Seeing how the ecko-fill is used for a UV blocker UV rays are not an issue. If applied correctly once you apply your final coat of ecko-fill you see no weave. Works good on these applications.

Dana I really careless how it's spelled but thanks for correcting me.

15. Jun 17, 2016

Pops

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On my JMR, I used one brushed coat of Poly-Brush, one light sprayed coat of Poly-Brush then two sprayed coats of Poly-Spray. Then 2 light cross coats of Poly-Fiber Urethane.

Last edited: Jun 17, 2016
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16. Jun 17, 2016

TFF

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I have to disagree that UV is not a problem. It is a slow problem. You don't know when it will be a problem. A friend was flying his little biplane having fun and he started to have an elevator jam. Nothing felt right and sounded right, but he was able to land. Hopped out and all of one side of the fuselage fabric was wrapped on the horizontal stabilizer. His dad grounded all the family fabric airplanes. He had let the covering degenerate too much even though it looked good. The dad was a past Oshkosh Grand Champion Winner so they were not crappy condition airplanes. I don't know if this plane was cotton or Dacron but it was not the original covering. The problem with leaving it at the primer stage is it is not meant to do anything but absorb UV and make the next stuff stick. It can work for you but it also can look like a 86 Chevy with the clear coat pealing. It is experimental airplanes; that is fine. I just don't get shortcuts, to not make things as good as you can since your but is in it and you are spending all you time building it. 4-5 coats of paint. I get all the angles; I even research them. I don't want to do stuff over more than anything.

17. Jun 17, 2016

Pops

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I may be over during it but when I'm covering I put cardboard over the hanger shop windows to block the sunlight until after the silver is on.

18. Jun 18, 2016

Peterson

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So in a thread with fabrics/materials/weights, has anyone compared weights of Hipec products? Manufacturer usually instructs to use them with Lincon or Ceconite cloths.

19. Jun 18, 2016

Rockiedog2

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I noticed a while back when looking up thru an inspection plate in the bottom of the SS1 wing with the light just so that there was light showing thru adjacent to the edges of the tapes. That with the specified 3 xcoats of Polyspray. Those who have sprayed much paint know that it doesn't like to go in corners. I guess thats what's going on there...there is something of a minute corner to the edge of the tapes. I know I didn't sand thru as I don't sand much atall anymore; mostly just knock the nibs off with 400.
anyway, so I intend to spray some more Polyspray along those tape edges. any knowledgeable or experienced amateurs(I'm not exactly a newbie at it but sure don't know everything) or pros feel free to comment on what's going on there with that. I have talked to others who have had the same thing. First time I've noticed it. So what prompted me to tell about that is what Pops said about covering his windows...my plane is hangared but has fiberglass skylights which I assume will pass UV please speak up if you know for sure. And my plane has been sitting under those skylights for about a year w/o much Polyspray along the tapelines. So theoretically anyway that might be a problem. I've never worried about short term exposure on unprotected fabric as all the tests I'm familiar with put samples out on the fence or somewhere for about a year then do their tests. Well, dunno but am gonna add some silver and carry on. My Legal Eagle fabric is 14 years old and has been sittin under the same skylights all that time not to mention several weeks sitting out at various flyins. When I get around to resurrecting it from retirement I'm gonna do a punch test on it. No, not a Maule test tool. I used one of those one time and never again, terribly abusive tool I thought I was gonna bust a rib. I'll just take a finger tip and put increasing pressure on the wing upper fabric and see what happens. Just thoughts added to Pops he' and I think alike most of the time we're both old and have made most of the mistakes and actually remember some of the lessons learned. I'm relearning some of em

20. Jun 18, 2016

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