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RE: Is dope & fabric covering dead? - 2/6/2006 9:02 PM   
vintageflyer


 

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From: kaneohe, HI, USA
Status: offline 		Richard,
Sounds like you know exactly what results I'm looking for for my Falcon. I'll use the silk on it. Now it's off to the Sig web site!

David

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RE: Is dope & fabric covering dead? - 2/10/2006 3:55 AM   
2fast


 

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Sig Koveral is great stuff for open areas like wings. Attach with Nitrate dope. But for sheet balsa portions like fuselage sides, I cover with silkspan. Adds strength to the balsa, is easy to attach and is very light. This method will weigh less than the plastic iron on stuff.

I'm sure you can find Nitrate dope in Hawaii. Most airports have an aircraft supply store nearby, they will have the dope and thinner. If not just call around to the airport maintenance folks they will know where to find it. Focus on the smaller fields that cater to smaller planes. Next shot is to find the local chapter of the EAA. This group enjoys building full scale planes. They will know where to find the dope.

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RE: Is dope & fabric covering dead? - 2/13/2006 12:50 AM   
H5487


 

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Status: offline 		Thanks, Guys, for your replies. I guess fabric covering is still alive, if only with the true model builders (as opposed to model BUYERS!)

Now if my memory serves me, the proper procedure is to first apply a coat of nitrate dope to the bare fabric (since butyrate dope doesn't normally stick well to fabric) and then follow up with several coats of butyrate. If this is true, why does Tower stock only butyrate? Is the nitrate step skipped nowadays?

And finally, can someone recommend a book that explains how to fabric cover a model? It's been 25 years since I did one. (Yes, I've already got the Stits Polyfiber book but it doesn't address "real" dope.)

Thanks!

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RE: Is dope & fabric covering dead? - 2/13/2006 9:23 PM   
tweedy



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Status: offline 		There are as many ways to cover with silk and dope as there are model builders but I will try to explain the process. First if you are covering with silk or silk span you do not need to use nitrite dope to attach the covering butyrate will stick well enough, if using koverall or nylon you must use nitrite or some other proprietary adhesive. Sand the structure very smooth and finish sand with 320 grit give the structure at least 3 coats of dope thinned 50/50 lightly sanding between coats you want to be able to see a sheen on the coated surface if you wish you may use a balsa filler coat for the second coat of this process, but sand most of it away. Cut a piece of silk about an inch larger all around than the surface to be covered you need to wet the silk some people dip the silk in water and squeeze out the excess the drape it over the surface to be covered others drape it over the surface to be covered then spray water on the silk, stretch excess wrinkles out of the silk and attach to the perimeter of the framework by flowing dope thinned 50/50 through the silk and rub it in with a finger tip keep the silk wet by respraying, pull and stretch the silk around compound curves cut darts if necessary at wing tips and at nose section to facilitate covering compound curves, after the water and dope dry the silk will shrink tight the dope will be a milky white. Trim off excess silk with a double edge razor blade tape up one edge to protect your fingers rub in one more coat of dope around the parameter of the framework to help seal down loose edges and to give the next piece of overlapping silk something to stick to. Begin the finishing process by brushing on thinned coats of dope (40% dope 60% thinner) until the weave of the silk is completely filled if you use unthinned dope before the covering is filled it will flow through the covering and create unsightly puddles and blotches, sand very lightly between coats (400 or 600 grit) but be careful not to sand into the silk especially at the ribs and sharp corners, if a light structure you might want to switch to SIG Lite-Coat once the desired shrinkage is achieved. one method that some builders use is to size the silk before covering they do this to make the silk easier to handle, take a piece of silk and iron out any wrinkles then hang it up by one edge or attach it to a square frame and brush on one coat of very thin dope (90% thinner 10% dope) let it dry and then use the silk as above to cover your model this makes the silk much easier to work with it keeps the fibers from shifting and makes crating clean lines in the silk without unraveling. I could go on and on but this is a start.

Richard Browning


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RE: Is dope & fabric covering dead? - 2/17/2006 1:48 PM   
H5487


 

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Status: offline 		Wow! Thanks for the great info, Richard. I'm looking forward to covering my model.

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RE: Is dope & fabric covering dead? - 2/18/2006 12:01 AM   
bdavison


 

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Status: offline 		The reason why lots of people use nitrate dope vs butyrate dope isnt for sticking power....its for shrinking power.
Nitrate dope shrinks better than butyrate dope. Its easier to get that "tight as a drum" covering.

Monokote covered airplanes are nice and all......but there's just something about seeing a plane covered in "old school" tissue and dope that really demands attention and respect. Unfortunatly it is a dying art in today's age of ARF, RTF planes.

Im only in my early 30's so monokote was available throughout my life...but I still took the time to learn the old ways of dope and tissue covering just because it's still got that classic appeal. Its really a shame that these skills arent being passed on to the younger flyers.

We dont have airplane builders now much anymore...now we have airplane assemblers.



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RE: Is dope & fabric covering dead? - 2/18/2006 12:29 AM   
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Status: offline 		in fact I went to Wal mart last night and found the prettest Fokker RED matl, super thin, $1 a yard-- thaTS RIGHT, $1 DOLLAR PER YARD. now to find the best glue, have 2 quarts of Nitrate dope left to try. anybody have any ideas of a heat reactive glue, similar to what was used on Coverite? dick

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RE: Is dope & fabric covering dead? - 2/18/2006 12:36 AM   
rainedave



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Status: offline 		I realize now how fortunate I was to have met the right person when I started in R/C in 1990. The man who leased the club field and taught me to fly was one of those guys who had come up through every stage of the hobby. He flew Free Flight in the 40s and 50s, C/L in the 50s and 60s, Pattern and Pylon in the 60s and 70s and Scale and Sport in the 70s and 80s.

As soon as he had taught me to solo my Kadet MkII, he introduced me to Free Flight and the art of covering with silk and tissue. I was so taken by the satisfaction of building a model from plans, covering it with silk and nitrate and watching it fly unassisted that I began putting all of my time into it and drifted out of R/C.

My point is that this guy took the time to teach me about this stuff. I could have just as easily met another istructor and missed out on all this. Covering with silk and dope won't die as long as there are people to teach it and pass it on to newcomers.

Now that I've gotten back into R/C I have a genuine respect and admiration for building and covering. Iron-on film may be fast and easy, but there is just no equal to an open framework covered with drum-tight silk and the sheen of dope. We should all take a few silk covered planes to the field with us every time we go flying, and really take the time to teach the technique to anyone who shows an interest. Someone did it for me and I honestly feel indebted to them. This is getting off on another subject, but clubs should offer a membership discount to those who build what they fly (assuming they're physically able to).

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RE: Is dope & fabric covering dead? - 2/21/2006 11:18 PM   
tokpilot


 

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Status: offline 		Dope and fabric covering is alive and well in my work shop . I use it on all my control lone free flight and rc planes. I also am a aircraft rebuilder by trade and a pilot as well. The way I see if if plastic was suppposed to be used on aircraft coverings it would have been invented before dope and fabric type finishes. I am doing 3 antuques now to fly this summer a Dallaire a 84 inch Quaker and a Mercury ll will be done with glider cloth shrunk and doped. Glider cloth is very light very strong and you can acheive a wonderful finish with it . Sig Coverall is about the same. Will post some pictures here when I do my covering. Dont let the old ways die pass along the knoledge to other modelers about the old ways

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RE: Is dope & fabric covering dead? - 2/22/2006 2:30 AM   
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Status: offline 		Dick, round here we use a Bostik glue called '1768' or 'Multibond'. Thin it with acetone about 50% depending on how old it is, brush it on the airframe, give it 30 mins to go off, then apply your cloth, Koverall, Polyspan whatever, and heat to activate the glue.

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RE: Is dope & fabric covering dead? - 2/22/2006 4:17 AM   
Frank Schwartz


 

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Status: offline 		1708 or Multibond?
Where do you get it? Loew's? Home Depot?

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RE: Is dope & fabric covering dead? - 2/22/2006 2:29 PM   
j.duncker



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Status: offline 		Still alive and sticking on old style CL combat models in the UK.



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< Message edited by j.duncker -- 2/22/2006 2:35 PM >

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RE: Is dope & fabric covering dead? - 2/23/2006 12:42 AM   
dicknadine


 

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Status: offline 		took my own advise and went back to Wal Mart and found 2 rolls of Fokker Red, super thin matl @ $1.00 per running yard, ended up with 10 yards. also found a new, maybe adhesive- its called Glue Stic, comes 3 tubes in a pkg. rub it on the balsa and then rub the fabric over it, gives time to apply the fabric before it dry's out on the balsa, if so just wipe on another coat, will tell later how good it accepts clear dope. my 42" D7, Fokkers will be electric so I won't be clear coating them. also gives an athenitic look. will send photos-- once I learn how download photos from the new HP 315- its confuseing to this old bird.

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RE: Is dope & fabric covering dead? - 2/23/2006 3:12 AM   
johnvb-RCU



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Status: offline 		Frank, we buy it in 4 litre tins from a specialist supplier here in Canberra, Australia. It seems to be called Multibond if you buy it in little tubes, and 1768 when in bulk

Here is a link to an Oz site with a data sheet for this stuff: http://www.bostikfindley.com.au/pdf/datasheet/bostik_multi_bond.pdf

It's 1768, not 1708 BTW.

John


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ORIGINAL: Frank Schwartz

1708 or Multibond?
Where do you get it? Loew's? Home Depot?



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RE: Is dope & fabric covering dead? - 3/4/2006 7:42 AM   
balsaworks



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Status: offline 		I have been pushing for covering with silk over tissue a few times already on this forum, so I thought I´d post some photos to show how easy it is to do.

The wing in the photo here is already covered with tissue, which is really easy with this sort of wing which is partly sheeted.
I used gampi tissue from a local arts supply, it´s about the same as lightweight Esaki, which is available at Sig´s.
Two coats of non-shrinking nitrate dope (for the adhesive power…) around the edges on the bare wood, then the tissue was laid on, and stuck in place by flowing thinner through the tissue along the edges and smoothing down with a finger.
After water shrinking the tissue was so tight, I continued to dope with non-shrinking nitrate. Two more coats cut to 1/3 with thinner were enough to seal the tissue.


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RE: Is dope & fabric covering dead? - 3/4/2006 7:44 AM   
balsaworks



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Status: offline 		The wallpaper paste in the photo is perhaps a bit on the thick side, but it´s still easy to brush.
This wing can easily be covered with a single piece of silk, by folding over the leading edge.
I started with the bottom and attached at the center section first, by first laying the silk in place and then brushing wallpaper paste through the silk onto the wing.


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RE: Is dope & fabric covering dead? - 3/4/2006 7:50 AM   
balsaworks



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Status: offline 		Continue to brush on the paste, from the center and out towards wing tips, the leading edge and the trailing edge.
The paper covering will slacken a little bit as you can see, but that doesn´t matter.
Just make sure that no air is trapped between the silk and the paper and it will come out right.


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RE: Is dope & fabric covering dead? - 3/4/2006 7:53 AM   
balsaworks



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Status: offline 		The silk is folded over the trailing edges and wing tips, pasted down and trimmed with a sharp razor blade or X-acto. Leave the silk hanging at the leading edge so it can be folded over, as soon as the underside and all the edges completely dry.
Silk conforms very easily to compound curves such as these rounded wing tips.
White lightweight silk can simply be overlapped and pasted down around the edges for a very neat finish. If you use coloured and/or heavyweight silk, the overlaps will show, and they need to be trimmed neatly for best appearance.


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RE: Is dope & fabric covering dead? - 3/4/2006 7:56 AM   
balsaworks



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Status: offline 		The silk covering is in place, drum tight and already sealed. Weight build-up so far, from the bare wood is 10 grams (the wing span is 32”). I will put on one more coat of clear (non-shrinking) dope, spray on some colour and finish with a fuel proofer.

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RE: Is dope & fabric covering dead? - 3/4/2006 8:38 AM   
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Status: offline 		I have a question. When dry does this method produce a more rigid surface, like fiberglass, or a flexible surface, like monocoat?
I am new to RC but have already decided I don't like the fact that monocoat starts to come loose and has to be ironed back down all the time. I have been looking at alternatives, but was told glass can not be stretched over an open frame, this looks as though it can, but I am looking for something that can be worked with to achieve a glass like finish.

Thanks Bob

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RE: Is dope & fabric covering dead? - 3/4/2006 9:12 AM   
balsaworks



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Status: offline 		Bob,

This technique produces a drum-tight & quite rigid, non-flexible surface, very different to Monocote.
It will not go limp with variation in temperature and it will definitely not come loose around the edges or bubble up over sheeted surfaces like the plastic coverings sometimes do.
You can modify the amount of “tightness” that you want by using high-shrinking or low-shrinking dope, Sig´s have various types here.
You can also add a plasticizer to the dope, like a couple of drops of castor to produce a slightly softer and not so tight covering if you wish.
In the example above I used only non-shrinking dope throughout, and still came up with a really drum-tight covering because the water shrinking was so effective on both the tissue and the silk. This is the first time this has happened, I normally use low-shrink dope on open surfaces and non-shrink on sheeted surfaces.
I have models covered like this that look like new after 20 years.

Tomas


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RE: Is dope & fabric covering dead? - 3/4/2006 5:49 PM   
Jim Thomerson



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Status: offline 		I've done tissue over silk, which gives a nice surface. Similar to what was said above except that the silk gets a couple thin coats of dope to provide adhesion for the tissue. Tissue is put on and water shrunk, then stick the tissue down to the silk with thinner. Never used wallpaper paste. If you dope, do use plasticized, or non-tautening dope, else you will eventually have a cracked finish. A thin coat of not plasticized to help shrink is OK. Nitrate sticks better than butyrate, and will essentially stabilize once it shrinks. Butyrate will shrink indefinitely, even the non-tautening. dope is thermolabile, so you can heat out warps, etc.

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RE: Is dope & fabric covering dead? - 3/5/2006 9:55 PM   
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Status: offline 		Great set of posts Tomas. Thanks for showing us that.

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RE: Is dope & fabric covering dead? - 3/5/2006 10:20 PM   
wildchild45177



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Status: offline 		Thank you for the info. I think I'll try to find a book that gives detail, read up then give it a shot.
Thanks Bob

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RE: Is dope & fabric covering dead? - 3/6/2006 4:58 AM   
Mike Denest



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Status: offline 		Once you get the hang of it, applying a silk covering job is easy. The art is to get your dope coats sag free. I don't use tissue at all, I give the structure at least two or three coats of nitrate everywhere the silk is going to touch and lightly sand prior to applying the silk. Then I apply the silk wet, keeping a spray bottle handy to add just enough moisture to keep it from drying too fast. My first coats are nitrate thinned 70 - 30 thinner to dope using a high quality brush applied around the edges. As I work out the wrinkles, I keep the area I'm working wet with dope. Once covered and trimmed, I apply at least three coats of nitrate minimum then go to butyrate, spraying at least four coats, lightly wet sanding between each. Since pigmented butyrate is opaque, I spray two coats of aluminum pigmented butyrate, sanding the first coat. It will protect the silk from UV light and make the pigmented colors more uniform. Then I'll spray the color. Yeah, it's a lot of work but I can show you a twenty year old airplane that still looks pretty good. Oh yeah, make sure you have lots of ventilation! Another trick working with silk is not to get it too loose or too tight. Loose, it will look like a wrinkled old elephant and will take a few days to tighten up and too tight, it will twist like a pretzel over time.

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