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dannparks
Unregistered
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 Posted Sunday, May 17, 2009 @ 01:56 AM
I am moving closer to recovering N2188. The last thread that I remember about coverings was recommending the Polyfiber system. There are some new water-based systems out now (Stewart). Are there any additional thoughts or new insights on covering (without rib stitching) and painting?
Also, I will not be recovering the fuselage, just repainting it. What systems will be best for painting over the existing fuselage covering?
Thanks for any suggestions.
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SteveBeaver
Unregistered
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Posted Sunday, May 17, 2009 @ 03:11 AM
This is a subject that people seem to feel passionately about. It's like asking a programmer what his favorite editor is, or a cook for their favorite chocolate chip cookie recipe.
Covering is a sizable investment in time and money so I would recommend going with something tried and true. If you follow the procedure manual, you will get good results whatever system you choose. But since you asked, these are the systems I prefer:
For a "vintage" appearance, shiny, but not glossy I like to use the Stitts Polyfiber "alternative" system. I use a minimum of Polyspray (to save weight) a coat or two of white Polytone with the optional UV additive to fill the weave, and then finish with colored Butyrate dope. I feel this system is one of the least expensive and easiest to apply. Very forgiving of mistakes and gives a beautiful appearance.
For a modern "wet look" gloss, I prefer the Air Tech coating system with no substitutions. The adhesive is particularly good and I would have no hesitation using on the Fournier cap strips.
Good luck,
Steve
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Sam M.
Unregistered
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Posted Sunday, May 17, 2009 @ 05:23 PM
We recently recovered our RF4. We used light weight glider fabric and nitrate and butyrate dopes. This is my favorite method, and I would say much more forgiving than polyfiber. You do spray more coats, but the finish is nicer with less work. See N1700F. (As Steve says, people are passionate about one method over another, I have been covering airplanes for close to 20 years, dope is my favorite. Rowena Mason)
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dannparks
Unregistered
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Posted Sunday, May 17, 2009 @ 08:34 PM
Thanks for the information. I hope my recovering and paint comes out half as nice as 1700F. You mention lightweight glider fabric. Is that similar to the uncertified light fabric that Polyfiber sells? It seems that the parts of the airframe that are actually covered with only cloth are very low-stress areas and the light fabric could save some weight. Have you noticed any issues with the lighter cloth?
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dannparks
Unregistered
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Posted Monday, May 18, 2009 @ 08:12 PM
Eugenio, you can probably answer this. What were the original RF4's covered and painted with? What is the most chemically similar system available now? What do you cover your rebuilds with?
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Sam M.
Unregistered
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Posted Monday, May 18, 2009 @ 11:27 PM
Polyfiber and Ceconite both make an uncertified light weight fabric 1.7oz. They come off the same mill and are exactly the same. The only difference is in the finish coatings. Polyfiber versus Nitrate and Butyrate Dope or some other process. The original RF4 covering was cotton. The glider cloth is lighter and stronger than the original cotton. We have had no signs of any problems with the light weight fabric. I do not know what the original finish on the cotton was because ours had been re-painted. Under the paint, however, was dope. We were able to soften and remove the cotton and dope from the wood using a combination of heat and thinner. Good luck with your project.
Rowena
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eugenio
Unregistered
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Posted Tuesday, May 19, 2009 @ 02:45 AM
Originally the RF's were covered with cotton. On the fuselage, wing box, stabilizer and fin it was a lightweight (50g) cotton fabric, on the wing it was grade A cotton (about 90/100g). First coatings were nitrate dope (standard procedure for most covering sysrems), then, instead of aluminium dope they used a yellow/green primer that I suppose is something like zinc chromate, then the finish was two components enamel.
My standard process is to remove the whole cotton from the aircraft (on the fuselage and other plywood covered parts is a neverending job), recover all plywood with 50g glass fabric and epoxy, and wings and control surfaces with Diatex 1500 EV3, a 90g dacron fabric equivalent to lightweight ceconite or similar. Glue is standard nitrate, no rib stitcing or lacing is needed. I do not use butyrate, but only nitrate, three to five coats, then I use 2K sealer primer, plasticized (a light coat, otherwise it will be prone to cracks), then the finish is polyurethane enamel, plasticized too. The fiberglass covered parts should be treated as it were fiberglass, so you need only 2K sealer and polyuretane finish, no need of plasticizer (but if you use the same plasticized products is the same).
Remember to make all repairs before covering the plywood, the surface must absolutely be smooth.
cheers
Eugenio
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chucknugent
Unregistered
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Posted Wednesday, May 27, 2009 @ 00:34 AM
What about the RF5b ? The past owner ran the outboard panel over a taxi marker leaving a nice hole in the leading edge. Having been hangered whole life the fabric and paint is in good shape, I just need to know whats on the ship to find a suitable system for the patch.
chuck
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eugenio
Unregistered
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Posted Wednesday, May 27, 2009 @ 01:43 AM
The leading edge is 2mm thick birch plywood. Not difficult to be repaired. For details see the AC 43-13 about acceptable repair methods. Over the repair you can use cotton or dacron as you like, then paint with dope or enamel as you prefere. The original paint was Glasurit, a two component epoxy, but a polyurethanic is the same.
ciao
Eugenio
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chucknugent
Unregistered
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Posted Wednesday, May 27, 2009 @ 09:29 PM
I dusted off my copy of AC43-13 and reviewed chapter 1 , wood structures (have not opened that chapter in 30 years ) The repair will not be a problem. I find it hard to beleve that in 1975 a manufacture would use a more costly,heavy, and less durable covering process as grade A cotton. I have used nitrate/ buteyrate, Stits polyfiber, and Cooper Superflite II, of all the Superflite II was my first choice . 30% less labor ,100% urathane (will not peel from dacron like dope) ,some of my jobs are flying around after 25 years, and still look like the day thay came out of the shop. With proper care all systems can do a fine job.
chuck
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chucknugent
Unregistered
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Posted Thursday, May 28, 2009 @ 11:26 PM
Went out to the hanger, pulled the temp. repair off the wing,( 100 mph tape) and everybody was right Cotton ! 34 years and still quite nice,
chuck
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Jorgen
Unregistered
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Posted Friday, May 29, 2009 @ 03:11 AM
Chuck,
glad to hear your fabric is in good shape! Since you´re new to this forum, you might not know that the rest of us are yet to prove Eugenio wrong in any Fournier matter. Thanks for your inputs Rowena and again congratrulations again on a splendid rebuild.
Take 5(b) just 4 fun/ Jörgen
[Edit by Jorgen on Friday, May 29, 2009 @ 03:19 AM]
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chucknugent
Unregistered
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Posted Friday, May 29, 2009 @ 10:15 PM
My fabric is a testament to fine workmanship and 34 years in dry hangers. No mater how long you are in avation there is always somthing new, or old to learn, you just have to keep the ears open. Am I correct in hearing that there will be a get together in France next year? If so I look forward to meeting some very talented restorers.
chuck
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dannparks
Unregistered
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Posted Sunday, May 31, 2009 @ 01:04 AM
I'd like to hear a little more about the process of removing the old cloth from the fuselage, HS and VS. The old covering seems to peel right off the control surfaces, but it is stuck hard to the HS, VS, and fuselage -- or maybe it is a different cloth that isn't strong enough to be pulled off. Any detailed instructions would be greatly appreciated.
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Sam M.
Unregistered
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Posted Monday, June 1, 2009 @ 03:39 AM
Soak a Rag in thinner, lay it over the fabric then cover that with Tinfoil and wait a while. come back and peel it off. You can also use a heat gun to soften up the fabric.
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eugenio
Unregistered
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Posted Monday, June 1, 2009 @ 02:04 PM
I usually use paint remover gel (is a product based on methilene dichloride and alcohol). On two components enamel thinner is not enough active. Paint remover don't affect the wood, only soften the paint. You need first to remove the paint from the old fabric, then soften the fabric and remove it. The original cotton is quite hard to remove because it sticks much better than polyester cloth, so you must soften the glue under the fabric to be able to tear it away. Anyway, whatever kind of system you use just be careful not to damage the plywood or you will loose a lot of time repairing all the scratches.
All plywood is treated in the same way, so it is like so the stabilizer, the fin, the wing and the fuselage.
enjoy yourself with this job
Eugenio
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dannparks
Unregistered
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Posted Monday, June 1, 2009 @ 05:50 PM
I did some tests and the thinner had minimal effect on this particular paint. The only thing that seems to do it is a gel paint and epoxy remover called Jasco. I was concerned about it effecting the wood, but as Eugenio mentioned it supposedly is harmless to wood. Anyway the plane does seem to have a lot of paint in places and it will be nice to get all of it off. I am also finding a lot of hairline cracks in the fuselage paint that are all the way down through the fabric. So if I paint over it, it will just continue to crack. I guess this is going to be a bigger job than I thought -- :^)
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dannparks
Unregistered
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Posted Tuesday, September 15, 2009 @ 10:55 AM
A question about covering. Do you use edge tapes over the trailing edge seems? Or do you just let the fabric overlap at the trailing edge and call it good? Are there any edge tapes over the ribs or anywhere else?
Standard practice calls for lots of edge taping. Is this relevant for Fourniers?
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eugenio
Unregistered
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Posted Tuesday, September 15, 2009 @ 02:28 PM
No tapes at all. You only cover first the lower part of the wing and cut the fabric at the trailing edge, then cover the top wrapping the trailing edge up to the end of the wood. This way you have 2.5cm (1" overlap that is enough. Since you do not need to stitch the fabric you do not need to cover the knots, so you don't need tape over the ribs. Fabric on wings start just 5cm (2" before the end of the plywood (this means you have 5cm overlap on plywood). You don't need to cover the whole leading edge that you already covered with fiberglass.
Please note that standard covering is not for Fourniers. Like all european gliders the fabric is only glued. The only exception is on those gliders with concave airfoil where the lover part of the wing, where the airfoil is concave, is stitched (i.e K6, K13 etc.)
Also the fabric is lighter than the one used on airplanes, standard is the Diatex 1500 that is 90 g/sq.m (equivalent to Ceconite 102 or similar)
Heavier fabric means only more useless weight without any advantage.
Eugenio
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dannparks
Unregistered
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Posted Wednesday, September 16, 2009 @ 11:19 AM
When you put the fiberglass on the vertical stabilizer and the horizontal stabilizer, do you wrap it around the edge of the thin plywood skin?
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eugenio
Unregistered
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Posted Wednesday, September 16, 2009 @ 02:17 PM
No, it's practically impossible. The inside of the fin and stabilizer rear part is only painted with several coats of nitrate cement possibly plasticized.
Since the fiberglass hardly will unglue from plywood you won't have any problem there.
ciao
Eugenio
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dannparks
Unregistered
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Posted Friday, September 18, 2009 @ 00:43 AM
OK, one last question... When covering the rudder and elevators with fabric, is the seam at the trailing edge or on the front edge?
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eugenio
Unregistered
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Posted Friday, September 18, 2009 @ 11:55 AM
It is the same. If you use a single piece of fabric (more difficult to handle) for the two sides you can do the joint in the leading edge so you won't see any seam when installed (1/2" overlap is enough). If you do it with two pieces of fabric (easier and possible with small fabric scraps) you use the same technique used for the wing. In this case you can use the fabric cutted away from the wing covering. The final result is fine with all the two methods.
One more tip: before covering check at least twice that all fittings are properly fixed to the wood structure. After the fabric is on the plane you cannot anymore torque the bolts unless you cut away a piece of fabric.
When you put the fiberglass on the plywood remove all fittings in order to have the fiberglass under them, this is for have a complete film over the whole surface.
Eugenio
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dannparks
Unregistered
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Posted Thursday, September 24, 2009 @ 11:50 AM
I guess there are still a few more questions from a newbe fabric person...
Is the fabric glued to the ribs before it is shrunk, or after. The elevator, rudder, and ailerons are fairly flat. If the fabric stretches over the ribs without touching them after it is shrunk, how do you glue it to the ribs? Does this happen?
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eugenio
Unregistered
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Posted Sunday, September 27, 2009 @ 12:39 PM
Yes, this happen more frequently than you can think. The first step in covering is to glue the low spots on the plywood, or you won't be able anymore to glue it when shrunk. Tis is not the case on the wing ribs, but usually happens on the trailing edge and in the D-box where the ribs start. Remember first to lay enough coats of glue on the plywood to make it appear glossy, then glue the fabric with very diluited glue in order to fully entrap the fabric fiber with glue. If you use too thick glue it will not pass thru the fabric and does not glue it to the wood, impermebilize the fabric and you won't be anymore able to glue it.
Ciao
Eugenio
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jb92563
Unregistered
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Posted Tuesday, September 29, 2009 @ 11:03 AM
Hi Dan,
I was wondering if the paint is cracked on the fuselage, whether you think it might be feasable to remove just the paint, not the fabric, or does the fabric get schreded in the process of taking the paint off?
What do you think could be done with this?
http://picasaweb.google.com/lh/photo/6s-RiGIwsEkmQk3nGie2ag?feat=directlink
http://picasaweb.google.com/lh/photo/8Y2xPiiu7-_DkuniRhqJ3w?feat=directlink
Seems like the same kind of Cracking you had?
What coving/paint did you decide to go with?
Ray
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dannparks
Unregistered
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Posted Tuesday, September 29, 2009 @ 11:32 AM
My cracking is more like your second photo, not as bad as your first photo. Unfortunately, the cracking is not just the paint. The fabric is cracked right down to the plywood. Also there are probably many places that the fabric has cracked and it hasn't telegraphed up through the paint yet. If you could just remove the paint and repaint, it would quickly crack again.
I don't think it's possible to just remove the paint with chemicals, although you could probably sand off the paint without doing too much damage to the fabric. This would probably show lots of cracked fabric, though.
Unless Eugenio has some special way to patch the worst areas, the best way to fix it is to remove everything and recover it -- not an easy job. I have not started removing the paint/fabric from the fuselage yet, but removing it from the stabilizers was a bear.
I plan to cover the fuselage with fiberglass (as Eugenio does) and paint with polyurethane. I just tried covering the vertical stabilizer with fiberglass with mixed results. I need to work on a better technique to keep the surface smooth and even with resin. I can see that it will take much more work than I thought to cover the fuselage.
Maybe some of the other members will speak up on their process of covering with new fabric.
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Bob Brock
Unregistered
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Posted Tuesday, September 29, 2009 @ 12:15 PM
Dann: Thanks for all your questions, I have learned many things by reading these questions and replies. I hope to have the wings off N7725 on Sat., so if you are going to attend the EAA breakfast at Twin Oaks, be sure an stop by my hanger or give me a call. You are well ahead of me in the process so there is much I can lean. Thanks.
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eugenio
Unregistered
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Posted Tuesday, September 29, 2009 @ 03:47 PM
If you cover the cracks with paint, every crack will sort out again sooner or later. If you use dacron to cover the plywood you have good possibilities to have cracks somewhere due to the fact that dacron is more elastic than wood and does not glue as strongly as Cotton or Fiberglass. So the best way to do it is with cotton and nitrate cement or fiberglass with epoxy resin.
Dan, if you had not good results here you are some tips:
Use light fiberglass about 50 grams sq/m
Use very thin epoxy, if it's not enough thin diluite it with nitrate thinner
Do the job in a warm environment (not less than 22/24°C)
Use a short brush roll like those used to paint with enamel
Do not try to do cover both sides in the same time, wait one side is settled to start the other
Do not put too much resin over the fiberglass, but be sure to fill the whole fibers and not leave spots
Eugenio
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Jorgen
Unregistered
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Posted Tuesday, September 29, 2009 @ 04:35 PM
Hi Guys,
I agree with Mr Brock: Super thread, every Fournieteer will sooner or later have to consider repairs involving fabric, cracks, paint and plasticized nitrate cement (would you care to explain how you mix that, Eugenio?) so the more we're familiar with this, the better we will maintain our precious ships. I would only add that a picture tells more than a thousand words, so please enclose pictures, they really help in the understanding of this.
May the 4s be with you/ Jörgen
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