Another Polyspan lesson

Stuka Stunt Main Forum · 21 of 21 known posts recovered

Bob Reeves · Jan 21, 2004 12:11 PM

Just acquired another lesson on what not to do if you cover your ship with Polyspan.

Doing a little research on this site and going by recommendations, I covered the wing before I put it in the fuselage overlapping the Polyspan in the center like the big boys do. Was so proud, it turned out really well and all the sanding on the wing (before covering) paid off in what is the nicest looking covering job I have ever done.

I doped around the edges of the Polyspan but left the open bays and part of the area over the sheeting dry thinking I would put the necessary coats of dope on after I got it in the fuselage and the fillets done. The thinking was that the epoxy used to glue the wing in and fillets would have a better chance of penetrating the Polyspan and I would end up with a better glue joint than if I put it on over a couple of coats of dope.

This ended up being a real bad idea as over the last few days of finish sanding the top block and installing fillets the Polyspan has fuzzed up in almost everyplace I didn't dope it. I now realize this was caused from simple handling of the model while I was working on the fuselage and fillets.

The lesson is (drum roll please).. Put at least two coats of dope on this stuff immediately after covering the wing and before doing anything else.

I am hoping with careful use of sandpaper and heavy coats of clear dope that I can knock down the fuzzes without having to resort to more drastic repair measures. It would be difficult to re-cover without creating a stress point as the covering is now glued firmly in the fuselage and the fillets are done.

GLBahrman · Jan 21, 2004 02:27 PM

#1 source

Also remember that there are two different sides to Polyspan and if you put the wrong side up you will have fuzzy problems out of control.

Greg L. Bahrman

Bob Reeves · Jan 21, 2004 03:14 PM

#6 source

Yep, thanks to Tom's little dots I am sure I have the right side up. I am on my second coat of dope and it looks like it is going to be salvageable. Thanks to a lesson learned on the Legacy, just sand enough to cut the fibers sticking out of the dope, any more and you are right back where you started.

GLBahrman · Jan 22, 2004 02:42 PM

#18 source

We need to learn which side is the up side. I received a batch of polyspan from Tom that had the dots on the wrong side and had to strip and recover.

Greg L. Bahrman

Bill Little · Jan 21, 2004 02:44 PM

#2 source

Bob,
I learned that putting thin CA on the fuzzies while immediately wiping it off with an ear swab cures the problem if it is a small area. If the rest of the area is ok, the thin CA hardens the fuzzies so that they can carefully be sanded out.
Bill <><

Disclaimer: I am neither a NATS Champion, engine reworker, engine producer, column writer, Hobby Shop owner, *rockeet* scientist, nor otherwise. Just an old Advanced flier.

shelby554 · Jan 21, 2004 02:57 PM

#3 source

What is Polyspan made of? Is it paper ,or is it a woven cloth type product?

Don Jones

kdheath · Jan 21, 2004 03:03 PM

#4 source

>What is Polyspan made of? Is it paper ,or is it a woven
>cloth type product?

Neither. It is polyester, but spun like silkspan. Neat stuff, once you figure out how to use it. The poly that Tom Morris sells is marked on the outside so that you can get it on right side out.

Bill Little · Jan 21, 2004 03:04 PM

#5 source

LAST EDITED ON Jan-21-04 AT 03:09 PM (CDT)

It's a polyester product, "cloth".
Bill <><

EDIT: I was typing while KDH was, so it sounds like I am not agreeing with him. Not so! It is as kdH says. I was just addressing the "paper" vs. "cloth" aspect. The "fuzzies" are the outcome of the strands of fiber being roughened and they stick up like REALLY bad wood grain, but due to their nature, they will not sand out unless they are made sufficiently "hard".
Bill <><

Disclaimer: I am neither a NATS Champion, engine reworker, engine producer, column writer, Hobby Shop owner, *rockeet* scientist, nor otherwise. Just an old Advanced flier.

Bob Reeves · Jan 21, 2004 03:20 PM

#7 source

Hi Bill,

Doug Moon turned me on to the CA trick when I was sanding through the cap strips on the Legacy, works great for a small area but this thing has many square inches of fuzz and CA would make my nice light Skylark not so light

Thanks for trying to help, I think the dope and careful sanding is going to save it, will know over the next couple of days.

Bill Little · Jan 21, 2004 03:45 PM

#8 source

Hi Bob,
That should work. Good Luck on the Skylark!
I like the looks of that plane more each time I see it.

Bill <><

Disclaimer: I am neither a NATS Champion, engine reworker, engine producer, column writer, Hobby Shop owner, *rockeet* scientist, nor otherwise. Just an old Advanced flier.

Ty Marcucci · Jan 21, 2004 03:57 PM

#9 source

LAST EDITED ON Jan-21-04 AT 03:58 PM (CDT)

A neat trick under the polyspan or even silkspan for that matter, is to apply two or three sanded coats of Brodaks filler. Then the wood grain of the caps will not show through the silkspan or polyspan and makes for a nice clean appearance. Now if only I could get the rest of the wing to look as good!?!? Credit where credit is due. I learned this from some of Windys tapes and any guy that can get a 20 in appearance for this planes at the Nats, knows how to do it right.

Bob Reeves · Jan 21, 2004 04:55 PM

#10 source

Have the Windy tape series on "Finishing with Brodak dope" and they are excelent. When God put me on this earth he decided I had to be one that has to learn everything the hard way, watching Windy do something and me actually doing it are worlds apart

Tim McTigue · Jan 21, 2004 05:30 PM

#11 source

"Have the Windy tape series on "Finishing with Brodak dope" and they are excelent."

Amen to that! There's actually no superlative equal to the task of describing just how good these videos are...

Tim

MAAC 65703

tperry2054 · Jan 21, 2004 07:43 PM

#12 source

I have no Idea if it would help at all but I wonder if using an iron and heating the polyspan some might help with the fuzzies?

Tom

Charlie Chan · Jan 21, 2004 09:30 PM

#13 source

A QUESTION, not A SUGGESTION.
Could you lightly spray two or three coats (8 hours between lite coats)let it sit about a week the lightly sand.
Lightly means lite coats --at a distance---.
Anybody tried this?

Charlie Pate

SRiese5283 · Jan 22, 2004 01:44 AM

#15 source

>What is Polyspan made of? Is it paper ,or is it a woven
>cloth type product?

http://www.modelresearchlabs.com/

TRY THIS everything is here.

Scott Riese

mcm · Jan 21, 2004 10:04 PM

#14 source

LAST EDITED ON Jan-21-04 AT 10:04 PM (CDT)

The more I read about Polyspan, the more I like OzCover. I'm out right now though. Need to order more. Great Stuff, although I still use the tried and true silkspan for wingtips and fuse.

James C Johnson · Jan 22, 2004 09:37 AM

#16 source

I have used Brodak Primer to seal the fuzzies. Blue tape to protect areas you don't want to sand next to the ones you want to. I still think it takes more paint to get a good finish more so than silkspan, but truthfully say I am still learning as each plane gets a little better, I know this as wife complains about the time "invested" in each new project, Jim J

Bob Reeves · Jan 22, 2004 12:12 PM

#17 source

The dope/light sanding seems to be doing the trick. I put the 3rd coat of clear on this morning after light sanding and most of the real bad areas seem to be disappearing into the dope. The fillets and 3 coats of dope have added less than an ounce to the airframe even with the last coat not completely dry. Don't expect a couple more coats of clear to add any significant weight.

I thought about using OZ cover but I felt I needed to cover the wing before I put it in the fuselage and was afraid of trying to glue the fuselage to the Oz cover. I did use it to cover the rudder and it is coming out pretty nice.

Mikey · Jan 23, 2004 10:38 AM

#19 source

Bob,
What I learned (the hard way) about using polyspan is to never touch it with sandpaper until you get at least four coats of clear (thinned 50/50. Each time you give the model a coat of dope, double coat the seems at the leading edge, trailing edge, and the tips. Then use only 400 or 600 grit paper (dry). When the paint film is built up to the point you just sanding the clear and not the polyspan then shoot the color.

Mikey

Mike Pratt

Steve Scott · Jan 23, 2004 01:30 PM

#20 source

Paint? I strive for the look of colored silk or silkspan with a clear dope finish and perhaps a "little" colored trim. Since you can't get colored silkspan anymore (I not into dyes) I considered polyspan.

I've heard some varieties have a terrible propensity to fade in the sun.

I used to have nice looking results with the old Coverite Silkspun (white only) and Super Coverite materials although told they were too heavy for competition ships. Is Polyspan a good substitute for the Coverite offerings?