how to apply silkspan

[Dave Nyce]

Just built a Little Jumpin' Bean kit from Brodak, which was supplied with silkspan.  Last time I used silkspan was in the 1970s.  The way I used it before was to glue down the edges with Ambroid, then sprinkle with water to shrink it.  Then apply dope. 

This time, I used tautening nitrate clear dope to glue down the edges.  After that dried, I applied clear tautening dope over the whole wing, except the edges.  But the problem is that it did not shrink the silkspan.  So, what is the correct way to apply silkspan?
Thanks.

[Dennis Nunes]

Hi Dave,

Another way it can be done is shown in a YouTube video that Sparky did:

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Dennis

[Dave Nyce]

That was a good video, but he didn't talk much.  Is that only water that he is using the whole time? Or is it clear dope?  It looks like he gets the silkspan totally tight during application, and does not have to rely on any shrinking to get out the wrinkles.

Thanks

[Chancey Chorney]

Sorry I cannot be of much help as I have not done many silkspan jobs yet, but from my experience, I try to get it on as tight as possible and then dope the edges with Butyrate Non-Tautening dope myself. Once dry, I mist it with water and let dry followed by a coat of thinned dope and cornstarch(50:50) for filler than 3 thinned coats(50:50) over the works before color. I use the same dope from start to finish and I fnd it works very well and have not had any problems. The reason I use the dope I do is that I only build small 1/2a planes and was worried about the tautening damaging the framework and warping things. Funny as this is, the last one I doped was a Lil' Jumpin' Bean also!

[Gary Dowler]

Here is how I've always done it, and it works well for me. Apply a coat of clear dope to every surface the silk will ahear to. Wet your silk (I use a spray bottle and I actually wet it prior to the initial dope application) , hang it a second if needed to allow excess water to run off, then lay it over the area you doped. Smooth out wrinkles and as soon as it's where you want it to be, brush on more dope just over the areas you had already applied it to underneath. Work it in a little as you go.
The water is what makes it tight. As you wet it, it expands slightly, then as it dries it shrinks. The dope adhears it to the wing.

Gary

[Tim Wescott]

I do what Gary does, except that I pat the silkspan "dry" -- I aim for evenly damp, but definitely not dripping.

I've never had success putting it on dry and then shrinking it later.  That works well for tissue, but I've just ended up with a wrinkled mess when I've tried it with silkspan.

[Tim Wescott]

It goes without saying, but I'll say it.  ALL surfaces to be doped should be sanded smooth like a baby's cheek. Then wiped free of all residue of said sanding.

It can't be emphasized enough that it is like a baby's cheek.  Not with a baby's cheek -- that'll just @#$% off the parents.

[Gary Dowler]

It can't be emphasized enough that it is like a baby's cheek.  Not with a baby's cheek -- that'll just @#$% off the parents.

now that there is funny stuff!!!!   

Gary

[Mike Griffin]

Guess I will add my 2 cents worth here.  I usually don't apply Silkspan to solid balsa surfaces so what I am going to say applies to built up wings and based on the chance you can actually find good silkspan like we used years ago.

Lay a towel on a flat surface.  Fill a spray bottle with some water.  Lay the silkspan on the top half of the towel running longwise.  Spray the silkspan until thoroughly wet.  Fold the bottom half of the towel over the silkspan (sandwich the paper between the towel) and press down with your flat hand and rub it along the towel soaking up the water and let the towel absorb it.  Fold the towel back down and carefully lay the silkspan over the wing and carefully pull out the wrinkles. 


Now, before you do all of the above, you should have applied at least 3 coats of 50/50 thinned dope(I use Nitrate) around the perimeter of the wing.  I then take thinner, on a brush , and brush through the silkspan around the perimeter only and keeping the paper as taught as possible while you are doing this. 


Let the paper dry and it should be pretty tight.  I then go ahead and brush more coats of 50/50 thinned Nitrate or Butyrate over the whole wing until the silkspan is filled.


That is the way I do it which is similar to what others above have written. 


Mike

[Tony Drago]

Which fills the slikspan grain  better, Nitrite or Butyrate.

[Tony Drago]

Thanks TY. Yep. Vegas is not the Vegas of old. Way,way to many free loaders.

[Dave Nyce]

Do you allow any overlap of the top panel over the bottom panel (either silkspan or silk)?

[RknRusty]

Let the paper dry and it should be pretty tight.  I then go ahead and brush more coats of 50/50 thinned Nitrate or Butyrate over the whole wing until the silkspan is filled.

That is the way I do it which is similar to what others above have written. 
Mike

So, now that it has at least one coat of 50/50 clear on the whole wing, my question is, how much sanding between rib bays before applying color, and how to NOT sand through the rib edges or capstrips? I know Sparky uses 320 over the edge pieces, but I'm wondering if 1000 or finer should be used with extreme caution across the rest of the wing.

Sorry to bump an old one, but this is what I'm about to do for the first time. I'm finally stocked up with colors and clear, and have a brand new airbrush and compressor just dying to get in on the action.
Rusty

[Ken Culbertson]

Hi Rusty.  I assume you mean the silk span between the ribs?  I don't sand there until at least three coats of tautening dope had been applied, then I use 0000 dry steel wool, gently. I say dry because some has oil for use in machine shops. 0000 can be found in unfinished furniture stores, etc. I go lightly on the cap strips, if used, as well.  Yet, I still go through the paper in some places. Nature of the beast.  I keep small torn pieces of silk span for patches. The torn edges blend better. I never use a shrinking dope on the wood as it, as I mentioned above, NEVER stops shrinking and the wood grain pops out after only a few months. If it's for a banger or trainer, no worries, use shrinking dope.  Hope this helps.

Do you slightly round the edges of the sheeting and cap strips before covering or keep then sharp from the sanding block?  I did my last ship in coverite.  It came out OK but as long as there is silkspan to be had I will never do that again.  I just spent 3 evenings and a quart of Nitrate thinner getting that diabolical stuff off of an old wing.  Try and pull it off and you have a bunch tiny strips, sand it off and you have a fuzzball, soke it off and you get a gooey mess.  I tried A & B and finally went with the gooey mess.

As for the method, pretty much like Ty's with the following exceptions.  I do not dope the open bays when I put on the first coats.  I use non-tauting on all of the framework and I DO NOT dope the cap-strips or open bays.  After it dries out and the silkspan has shrunk I dampen it again (not wet)  When that is dry I put on three coats of Tauting over the open bays and let that dry for a day or two.  last coats and filler are all non-tauting.  I am electric so it is all Nitrate.

ken

[RknRusty]

Okay, thanks guys, I can work with that. I don't have any non tautening dope, but for my little 1/2A balsa Hyper Viper it'll be just fine as a learning project.

When it comes time for my Cardinal wing, I will have had Bob Z. pick me up some non-tautening from the Brodak shop. Every time he heads up north he takes a shopping list for me... what great customer service, free delivery by the Yellow Streak!

Non tautening butyrate, nitrate, or either one? My thinner is all the same stuff that I use for butyrate, I assume it goes both ways...
Rusty

[Dan McEntee]

 Paying attention to the edges helps a lot with preventing sanding through. One thing I learned from Windy tapes, is that for each coat of dope you put on the wing, brush on another coat just on the cap strips and along the sheeting edges and such. This builds up a little extra just where you need it. Another trick I picked up from the Tom Warden's Continental article was using 1" diameter circles of sand paper and your finger tip to sand the open bays. This tended to not dig into any thing as you went along. As with anything else, prectice makes perfect!
   Type at you later,
  Dan McEntee

[Dave Nyce]

Thanks a lot everyone.  Sounds like great advice.  Now I'll be ready to try again on the next plane.  (After reading the advice and thinking about it, I probably used tissue paper on the half-A planes years ago.  That's why it shrunk with water.)

[RknRusty]

Thanks a lot everyone.  Sounds like great advice....

Yes, now that the thread is topped off with the rest of the wing story, it's a nice bit of text to cut and paste into the how-to reminder notes.

Btw, I'm using Doctor paper that I got off the exam table. Shiny side up, span-wise grain... if it even has a grain.
Rusty

[Dennis Saydak]

Lots of good advice above. Here's what I do, which works very well for me. YMMV.
1) I use nitrate dope on the bare wood to provide a base for attaching the silk span, 2 - 3 coats as necessary. I find that nitrate sticks better than butyrate for applying silkspan.
2) Once the dope is completely dry I lightly sand the fuzz (raised grain) off with 400 grit sandpaper. Vacuum or use a tack rag to remove the dust.
3) I run a couple of inches of water in my basement laundry sink and totally wet the silkspan panel by dipping or dragging it through the water.
4) I then lay the wet silkspan onto a laundry towel, fold the towel over onto the top of the silkspan and pat it dry to remove the excess water.
5) Lay the damp silkpan onto the wing and attach it along a straight edge such as the T.E or flap line using nitrate dope.
6) Work out all the wrinkles and loose covering as best you can and complete attaching the silkspan along the fuselage and wing L.E. Wing tips can be tricky to cover neatly and sometimes using a separate piece of silkspan helps. It gets easier with a little practise.
7) Let the damp silkspan dry completely and you will be amazed at how nicely it shrinks out.

I usually apply nitrate for the first two coats of paint. It keeps the silkspan nice and tight. Then I apply several more coats of low shrink butyrate. The covering always sags for me when using the butyrate and it can take a day or two to tighten back up again. Here's a picture of my Rayette wing done this way.

[Steve Helmick]

Polyspan makes more sense for open structures (less warping problems), reserving silkspan for covering the fuselage.  Steve