papering problems of sheeted wing

[Scott Richlen]

I need some help.  I am papering a sheeted wing (no open bays) and having a very un-fun time with the paper.  Two others that I know say they have had the same problem and with different brands of light silkspan, so maybe we are using the wrong technique.  I am using light-weight plyspan and running the grain spanwise.  I wet it, blot it, set it on the wing (which has been previously doped about three times with light sanding between each application of dope) and then I use thinned dope to brush through the paper to adhere it.  The dope seems to expand the paper resulting in wrinkles in the undoped portions of the paper.  This results in smooth application of paper initially, but pretty soon I get substantial wrinkles in the paper as I try to dope it down.  I end up with a lot of wrinkles towards the edges of the paper.

I tried a small section running the grain chordwise and the paper laid down nicely.  But I'm not sure what will happen if I try this over a large section of wing.  (I may soon find out!)

I have papered a lot of open-bay wings and never had this problem.  So what am I doing wrong on this solid surface?

Thanks,
Scott

[steve bittner]

Scott
 You prep right with 3 or 4 coats dope about 50/50. The method that has worked for me is to hang the tissue up after wetting so the water drips out and wrinkles come out. Then I dope the perimeter of the wing, an inch or so on the leading edge, just the edge of the tip of the trailing edge and wing tips, and about 1 inch in the middle of the wing. Next if you can get a helper to grab 1 side of the silkspan and hold it above the wing while you lay the center section into place. I then grab the ends from helper an lay it down on the wing. You shouldn't have a lot of wrinkles at this point. Stretch it out dopping the leading and trailing edges as you gently pull the wrinkles out. Dope it good like you started the perimeter in the beginning and let dry. When dried it will be nice and tight, then dope the whole tthing with liberal coat of dope not dragging the brush a lot. Is this over a sheeted foam wing? There is other good methods to finish which you may or may not been exposed to. Have fun

[George]

Another way is to do as you did before until you have applied the dope to stick the tissue in place. At that point move your thumbs over the surface as if you are removing bubbles from under the covering. Since it is a wood surface a little pressure won't hurt. Essentially you are pushing out the wrinkles as the tissue expands. Work quickly and be ready to re-wet the surface with thinned dope as necessary until you have worked out all the wrinkles.

Of course there is never only one way. Good luck. Let us know what works for you.

George

[john e. holliday]

Put your poly-span/sillk span on like you would an open surface wing.  Have an iron or hot air gun to help get the poly-span around the tips.  Once the edges have dried shrink the poly-span.    Silk span put on wet and smooth it out as much as possible.   Keep spray bottle handy to keep it moist and dope the perimeter.    If the surface is smooth it should shrink just fine.  Make sure dope is thin enough to go through and soften the dope under neath.

[FLOYD CARTER]

deleted

[FLOYD CARTER]

"Plyspan" and "Polyspan" are not the same.  Polyspan is put on dry, while paper-based coverings go on wet.  Paper expands with water, and it also "relaxes" with clear dope- and tightens up when dope dries.  Over wood, if "nailed" down at first, the tissue is constrained from tightening up.

Even shrinking dry first, and then doping the stretched tissue, it can "relax" enough to make wrinkles.

I have avoided this common problem by using carbon veil over wood.  It doesn't expand.

Floyd

[Randy Cuberly]

First, I don't use polyspan over sheeted areas.

Silkspan can be applied without the difficulties you have encountered by simply stretching the wet silkspan in place as it is applied.  In otherwords after your preparation, which is fine, just pretend you're applying the silkspan over an open bay structure and keep lifting small areas if necessary and stretching the silkspan in place just as you would over open bays.  apply very thin (30%dope, 70% thinner) dope and continue to stretch in place with tension on the edges of the sheet, again, just as you would for an open bay wing.  Dont allow any wrinkles to accumulate in the silkspan as the dope dries.  It will dry very quickly because it's mostly thinner.  When partially dry switch to 50-50 dope and thinner and continue the process as before.  I always do rounded tips with a separate small sheet so the silkspan can be worked in both directions to get it around the tip.  Just overlap the edges about a quarter inch and the overlap will disappear as finishing filler is applied and sanded.  This sounds a lot more difficult than it is...just keep stretching the silkspan as necessary...which should not be very much at this stage.  Let it dry, trim the edges and apply a coat of 50-50 dope.  Three coats of 50-50 dope then switch to spraying.  

Not very difficult actually and fairly foolproof!

Randy Cuberly

[Balsa Butcher]

I think the issue is the material, not the technique. Silk span (the old stuff anyway) is porus. Thinned dope goes through it and adheres it to the surface. Plyspan is not nearly as porus. The thinned dope is not going thru the material so there is not a good bond between the wing and the tissue. I have had this issue before.

Since I'm out of old style light silk span I used domestic tissue (Peck Polymers) on a recent plane. It is porus but has no wet strength. Prepared surface the usual way then applied dope around the edges of the surface to be covered. Carefully laid the dry tissue over the surface to be covered then wet it with water. Wrinkle city, however it smoothed out after drying. Then very thin dope. It went through and bonded the tissue to the surface where Plyspan and Esaki tissue did not. Might be worth a try. 

[Randy Cuberly]

Well you just learned a very old lesson.  Don't try to cover anything with wet TISSUE!

Get some SILKSPAN and do it like I said.  Sand off the mess you have and do it right!

Actually your problems are manyfold and a combination of using the wrong materials and the wrong processes.

Thin dope will flow through Polyspan...I've done it many times...but it is not a good material to use on sheeted surfaces.

Randy Cuberly

[Carl Cisneros]

Hey Scott (he is in my club by the way folks)(our ex and a great Pres.)

I got a number 7 wool roller and some Behr house paint with the primer already mixed in the paint you can use.

(slapping ones own hand:  bad host, bad host..........)  

when I did F3A, before I ironed on the film for the wings (sheeted foam), I used a similar product to the polyspan in England and applied it DRY using thinned Dope.
never had any wrinkling problems. I just kept everything taut while doping the tissue.

[Scott Richlen]

Many of you seem to think I have made a typo and meant to type "polyspan"

Nope.  Nada.

I typed plyspan and meant it.  This is Sig's lightweight silkspan that is made in Japan.

I'll try running it cross-grain and see what happens.

Maybe get some Weatherbeater primer on it....

[Steve Helmick]

Plyspan sux. I recall trying it once with similar results, in 1981. I think I tore it off and chucked it out. I believe it is truly 2 plys of tissue, cross grained, leading to uncontrolled "billowing", if that makes sense. Domestic tissue (like Peck Polymer's) isn't too bad for your use. Fades like crazy, so don't use it for a clear finish. In actuality, you can apparently get the same stuff from the gift wrapping or craft store, tho I have not. I certainly would, if I had no silkspan or Japanese tissue and needed some for a purpose like yours.  Steve   

[Randy Cuberly]

Plyspan sux. I recall trying it once with similar results, in 1981. I think I tore it off and chucked it out. I believe it is truly 2 plys of tissue, cross grained, leading to uncontrolled "billowing", if that makes sense. Domestic tissue (like Peck Polymer's) isn't too bad for your use. Fades like crazy, so don't use it for a clear finish. In actuality, you can apparently get the same stuff from the gift wrapping or craft store, tho I have not. I certainly would, if I had no silkspan or Japanese tissue and needed some for a purpose like yours.  Steve   

Exactly what Steve said...I did not mistake ply span for polyspan in my reply to you but I did say use SILKSPAN...I guess I didn't whant to actually say plyspan sux but it's a fact!
 Actually I thought just about everyone knew that by now!!!   .

So again, USE SILKSPAN on sheeted surfaces!

Randy Cuberly

[Carl Cisneros]

Scott:
OR, use the K&B or who evers' 1/2 oz FG cloth and apply it dry using a 50-50 mix of dope and thinner.

The last 2 F3A ships I built I used this method on all the plane and it turned out BEAUTIFUL. I looked up in my old build book
on the Loaded Dice that I used this method on and total weight added INCLUDING K&B Super Poxy sprayed on was 3.2oz.
The plane was bigger then your big green monster in the basement. It had a wing span of 68" and fuse was 68" also. Power was
an OS Hanno Special 60 on pipe.

just something to think about is all. 

[Randy Cuberly]

Scott:
OR, use the K&B or who evers' 1/2 oz FG cloth and apply it dry using a 50-50 mix of dope and thinner.

The last 2 F3A ships I built I used this method on all the plane and it turned out BEAUTIFUL. I looked up in my old build book
on the Loaded Dice that I used this method on and total weight added INCLUDING K&B Super Poxy sprayed on was 3.2oz.
The plane was bigger then your big green monster in the basement. It had a wing span of 68" and fuse was 68" also. Power was
an OS Hanno Special 60 on pipe.

just something to think about is all. 

I would add that this method works very well and is pretty light.  The only downside is that if the weave of the fiberglass is not completely fill it will bleed out in the sun and the fabric texture can be seen!  Of course a lot of things bleed out in Arizona sun!!!!
Don't ask me how I know!

I have seen it done without that happening however.

I first learned about this method about 25 years ago from Mike Pratt when he build and finished one of his Magnum's for the AMA Museum.
It gave a terriffic finish and the big surprise is that it actually finished lighter than his previous finishes.  He published it in one of the magazines at the time!

Randy Cuberly

[Motorman]

So do you use Nitrate dope to stick the fiberglass on and fill it before spraying with Superpoxy? Butyrate keeps gassing off for years right? Are you talking about the old two part superpoxy or the new stuff?

MM

[Carl Cisneros]

Randy
As I remember back in 93-94 when I did this is that I did it in multiple pieces, i.e., top fues and rudder one side, then the other,
next, both sides and bottom at the same time. and then 2 pieces on the wing (one piece wing tho).

Then shot it with the K&B Primer, sanded it down GOOD, then shot on the colors I used.


Scott can do the same thing on his Mustangs wing and would turn out a treat.

What say you Scott?  Want to give it a try?  I can come over and help out.

[Randy Cuberly]

Randy
As I remember back in 93-94 when I did this is that I did it in multiple pieces, i.e., top fues and rudder one side, then the other,
next, both sides and bottom at the same time. and then 2 pieces on the wing (one piece wing tho).

Then shot it with the K&B Primer, sanded it down GOOD, then shot on the colors I used.


Scott can do the same thing on his Mustangs wing and would turn out a treat.

What say you Scott?  Want to give it a try?  I can come over and help out.

Hmmm....Actually this conversation has inspired me to try this again...think I'll use it on the foam wing Genesis I'm getting ready to start.

Only problem is it's one of Bob Hunts wings and it's so pretty I hate to cover it up...

Randy Cuberly

[Carl Cisneros]

Motorman
It was the OLD K&B Super Poxy  not the KAYRAP Ultrapoxy they finally went to.

I used the K&B primer before the color paint

[Scott Richlen]

Plyspan sux

Oh-oh!

Actually I thought just about everyone knew that by now!!!

Okay, so you guys are falling down on the job!  Who's turn was it to get me straightened out on plyspan??   

Thanks for all your input!  If I can get this plane done, I'll post some pictures.  Wrinkles and all! 

Scott

[Steve Fitton]

Scott, regular silkspan should work fine.  I use medium or heavy on my foam wing planes and don't have any trouble with wrinkles, except small ones on the compound curvature of the tips and they sand right out.  Sounds like that Plyspan is the source of the trouble.

[Motorman]

Motorman
It was the OLD K&B Super Poxy  not the KAYRAP Ultrapoxy they finally went to.

I used the K&B primer before the color paint

How did you get the fiberglass on and what did you fill it with?


Thanks,
MM

[Ward Van Duzer]

Uh...Silk?


W.

[James C. Johnson]

"Plyspan sux."

I am with Steve on this one... I used it once and it looked real nice... went on OK... but soon after the oil from the fuel started to creep under it... and since then I can tell every plane that has this stuff on it... everyone of them has blotchy oil spots... You might get away using it for electrics but that is it...

JJ

[dennis lipsett]

Look, if your going to use 1/2oz F/G cloth try using water based urethane. I've used it for years with complete satisfaction. Dries in about 2 hours , wets and fills much better than dope, sands out nicely, and I never use another coat of the product over the F/G after it has been applied.
Big bonus, NO STINK! That makes it my go to prep method, You may not be as light as dope, but done correctly with a brushed out application over the F/G your not much heavier and the slight penalty is worth it to me.
I go right to primer, 2 coats sanded down to the weave. My only option for paint is Rustoleum, No compatibility problems either. It works for me is loads cheaper than a doped finish and while I might not ever get a 20 point finish neither is the other 99% of us.
It was good enough for Alan Brickhaus to publish the technique and I was using the method on R/C models long before he published it. It is not new and has stood the test of time.

Dennis

[John Park]

If I may just put my two penn'orth in (that "two penn'orth" shows I'm an old Englishman!), I've done a lot of tissue covering over sheeted and solid sheet surfaces, and what I've ended up with after many years of using straight thinners brushed through the Modelspan (read "Silkspan") is VERY thin dope - no more than 5% dope/95% thinners.  I apply the tissue damp only where there's a double curvature.  The thin dope goes through the tissue well, and gives you enough 'slip' to ease out any wrinkles or bubbles: I find that straight thinners dries too fast, but if I use much more than 5% dope it makes the tissue too 'sticky' and hard to adjust.  The technique also works well with lightweight Jap tissue.

Regards
John

[Lauri Malila]

Scott,

Your problem is that the paper's adhesion to base surface is not strong enough to tolerate the shear forces as paper starts to shrink. That's propably because the adhesive (dope?) is not fully cured at the moment when paper starts to dry and shrink.
I have had similar issues when putting japan paper (thin Modellspan or Esaki Lite-Flite) over carbon surfaces or Icarex in my free flight wings. I usually put only 2 coats of thinned dope (nitrate) before applying the paper.
I have found that following helps:
-In papers that have other side shiny and the other matt, like Lite-Flite, it's better to put shiny side against the base surface. That way you have the best surface contact with minimum amount of adhesive.
-Use faster and more aggressive solvent to adhere the paper to doped surface. Normally I use standard nitro thinner for thinning my dope, but for adhering, I use acetone instead.
-Now I'm just guessing, but it might be better to pre-shrink the paper before covering, by wetting it and letting it dry. That should reduce the shrinking forces.
-Also, don't wet the paper too much with water. Lots of water is good when sliding the pieces of paper in place but before starting with dope, remove the exess water with kitchen towels.

By the way, does anybody know of paper with similar weight than Esaki Lite-Flite that does not fade so much..?

Lauri

[Mike Griffin]

Look, if your going to use 1/2oz F/G cloth try using water based urethane. I've used it for years with complete satisfaction. Dries in about 2 hours , wets and fills much better than dope, sands out nicely, and I never use another coat of the product over the F/G after it has been applied.
Big bonus, NO STINK! That makes it my go to prep method, You may not be as light as dope, but done correctly with a brushed out application over the F/G your not much heavier and the slight penalty is worth it to me.
I go right to primer, 2 coats sanded down to the weave. My only option for paint is Rustoleum, No compatibility problems either. It works for me is loads cheaper than a doped finish and while I might not ever get a 20 point finish neither is the other 99% of us.
It was good enough for Alan Brickhaus to publish the technique and I was using the method on R/C models long before he published it. It is not new and has stood the test of time.

Dennis

You are correct Dennis.  Allen Brickhaus taught me this method years ago too and it never fails.  He never used dope.  If you warm the Rustoleum up and then spray it, it will level out great.

Mike

[Mike Griffin]

If you are going to use dope, I quit using silkspan totally to cover solid balsa surfaces.  I do what Phil Granderson does.  Cover the solid balsa surfaces with two coats of unthinned nitrate dope and when it dries, sand smooth with 320 grit sandpaper (I use 3m). NOTE, YOU CAN ALSO USE KBS CLEAR COAT INSTEAD OF DOPE TO SEAL THE BALSA AND IT WORKS JUST AS WELL OR BETTER THAN DOPE.  Then thin some nitrate 50/50 and apply your carbon fiber veil.  COVER THE ENTIRE WING ALSO AND THEN CUT AWAY THE OPEN BAYS.  Then mix some talc' as much as will stay suspended in the dope, shake it well, let it settle out for about 15 minutes and then brush this slurry over the entire surfaces.  When dry, sand with 600 grit till smooth and then go from there with whatever final paint finish and clear coat you want to use.

This completely eliminates the problem with the paper you are struggling with.

Mike

[Carl Cisneros]

guys

here is the problem that Scott is having
first couple pics are the the paper set span wise
the nextcouple pics are of layed cord wise (much better results)

[Gerald Schamp]

This may not be pertinent to the topic at hand, BUT---what happened to the Heavy Duty Silkspan. I heard it is all used up coffee filters, but that was just a rumor. I like to use the heavy silkspan on wings and the medium on the rest of the plane.

After applying the usual substrate before applying silkspan, I mix up a small amount of dope( all Butyrate), thinner and retarder just to apply silkspan with. It helps adhere the silkspan better IMHO. In an open bay wing, I apply the silkspan wet, using Windex to wet it with, laying silkspan over a bath towel. Then after some blotting of the silkspan, I lay the piece over the wing and pull out as many wrinkles as I can, then brush this mixture on all the sheeted surfaces. Not on the cap strips yet, after about three coats of the above mixture has dried and sanded lightly between coats, then go over the cap strips with two or three coats, then go to regular dope thinned 60% and brush on enough to fill the weave, then and only then sand lightly the open bays with 400 grit, the gray paper that is super flexible. On sheeted foam wings, I use the retarder mixture here as well with no problems. An advantage here using the Windex, it lets you use your hands to smooth out the silkspan over the whole wing, and the retarder slows the drying time just enough to allow time to get all the wrinkles out and seems to stick the silkspan really good, and when using paint masks, this insures that there won't be any lifting of the surface beneath. I've tried to lift the base coats with Duct Tape just to experiment, and it doesn't lift. After watching all the problems that Windy had over the years with his painting, this seems to be one of the ideas that does work well, at least for me. The Windex also helps the silkspan go around wing tips very easily, must work kind of like ammonia does on balsa.

[john e. holliday]

I believe Windex does have ammonia in it

[Balsa Butcher]

All good suggestions and techniques. The problem is that the good silkspan is no longer available. The stuff being sold as silkspan is more span than silk. Substitute material all has issues...expense, wet strength, difficulty of application, going around corners etc. Polyspan is the answer for open structure, over solid components wood components the search continues. Next sheeted foam wing I build will be CF veil covered but anticipate a steep learning curve here as in any new (to me) technque.

[Scott Richlen]

Okay, for the second round (the top of the wing) I put the plyspan on with the grain running chordwise.  I also faced the shiny surface down (but I think grain direction is the controlling issue.)  The paper laid down perfectly with no bubbles or wrinkles.  I was able to "chase" away any wrinkles that appeared with my brush and additional nitrate.  Since the paper is only 18" wide, I had to overlap the edges.  Because of the grain direction I was easily able to tear the edges and they have pretty much disappeared after one sanding.

Thanks for all of your input and willingness to help.  Happily my problem areas are all on the bottom of the wing and I am sanding and sanding sealering them away!

Scott