Author Topic: Poly-Span covering problem (Read 11201 times)

Marvin Denny · « **on:** May 15, 2009, 11:17:40 AM »

What happened guys?

?? I cut and covered my NEW Novi IV wing panels and tail surfaces (all open bays) with poly span. It was cut from the same end of the roll and applied using nitrate dope.
I prepared the surface with three coats of nitrate, a layer of carbon fiber mette, three more coats of nitrate. area sanded and wiped down well. I double checked to be sure the shiney side was up on each surface. All turned out really nice except the bottom inboard stab and elevator. The poly span went on nice with no "fuzzies where I stuck the stuff down around the edges. Three coats of VERY thin nitrate to stick it down. All tightened really tight EXCEPT the lower inboard stab and elevator, which tightened "fairly well" but not as good as the other surfaces.
When I doped the overall covering, all coated nicely and smoothly EXCEPT the lower inboard stab and elevator. All were doped with the same nitrate. The affected surface looked like there was a reaction between dope. similar to painting nitrate over enamel!! All krinkly. It was some smoother over the open bays than over the balsa, but still "not good". The area just off the span near the fuselage was still very smooth.
WHAT HAPPENED to that one surface.
On another plane some time ago, i had a similar thing, but that was just a spot out in the middle of a wing panel and not nearly as bad as this.
I have stripped that section and am getting ready to re cover it.
Bigiron---- a perplexed bigiron I might say

Busby · « **Reply #1 on:** May 15, 2009, 03:20:18 PM »

Is it possible that you mistakenly used a brush that had been used to apply butyrate and no throughly clean?
Don't ask how I know not once but twice ion separate planes.
Busby

John Miller · « **Reply #2 on:** May 15, 2009, 03:46:16 PM »

I had a similar problem with my Torino. I attribute it to using Nitrate in the beginning. I know many have done so, but for me and my buds, it's been a problem. I now use Butyrate from the beginning.

Bob Reeves · « **Reply #3 on:** May 15, 2009, 04:48:42 PM »

Quote from: John Miller on May 15, 2009, 03:46:16 PM

I had a similar problem with my Torino. I attribute it to using Nitrate in the beginning. I know many have done so, but for me and my buds, it's been a problem. I now use Butyrate from the beginning.

Same here, I always used butyrate but decided to see what all the hype on nitrate was about and used it on a stunt ship. Turned into a nightmare of wrinkles and other issues I won't be repeating. And yes I used a new brush that had never seen butyrate.

Wished I could help you Marvin but have no clue.

Marvin Denny · « **Reply #4 on:** May 15, 2009, 06:45:59 PM »

I don't think it could be the brush as I had put the covering on the wing panels and one of the stab/elevator panels before the problem showed and the two panels following the affected panel were good. All were pre doped and currently doped with the same jar of nitrate and thinner. That is why I am perplexed. I bought a 50 yard roll of the stuff some time back (to get a good price break) and have covered five planes previously and only had one small area that gave a slight problem. I laid that one on using a monocote iron that may have roughed up the "fuzzies" on that panel and have been using a heat gun ever since.. Can't be non compatable materials as all of it has been nitrate dope and nitrate thinner all the way so far.
I just got the panel recovered and will dope it in a few hours.

Bigiron

Allan Perret · « **Reply #5 on:** May 15, 2009, 07:21:25 PM »

Quote from: Marvin Denny on May 15, 2009, 11:17:40 AM

What happened guys??? I cut and covered my NEW Novi IV wing panels and tail surfaces (all open bays) with poly span. It was cut from the same end of the roll and applied using nitrate dope.
I prepared the surface with three coats of nitrate, a layer of carbon fiber mette, three more coats of nitrate. area sanded and wiped down well. I double checked to be sure the shiney side was up on each surface. All turned out really nice except the bottom inboard stab and elevator. The poly span went on nice with no "fuzzies where I stuck the stuff down around the edges. Three coats of VERY thin nitrate to stick it down. All tightened really tight EXCEPT the lower inboard stab and elevator, which tightened "fairly well" but not as good as the other surfaces.
When I doped the overall covering, all coated nicely and smoothly EXCEPT the lower inboard stab and elevator. All were doped with the same nitrate. The affected surface looked like there was a reaction between dope. similar to painting nitrate over enamel!! All krinkly. It was some smoother over the open bays than over the balsa, but still "not good". The area just off the span near the fuselage was still very smooth.
WHAT HAPPENED to that one surface.
On another plane some time ago, i had a similar thing, but that was just a spot out in the middle of a wing panel and not nearly as bad as this.
I have stripped that section and am getting ready to re cover it.
Bigiron---- a perplexed bigiron I might say

You didnt mention anything about heat shrinking, did you ??
Only other thing I can think of is you got the grain in the wrong direction on the panels that had the problem.

dale gleason · « **Reply #6 on:** May 16, 2009, 07:13:42 AM »

I was thinking along Allen's lines....is there a possibilty that unequal heat on areas might give uneqal shrinking/tautnes? Then it wouldn't be a dope/thinner problem, but just a fabric problem. Or moisture? Would some moisture in the fabric turn to steam during the heat shrinking and then the dope wouldn't dry properly? Just guessing Marvin, really no clue....hope you get it figured out, dale g

Marvin Denny · « **Reply #7 on:** May 16, 2009, 08:26:33 AM »

Definitely not a "grain problem" Grain was the same as on the other panels. I don't think it was an irregular heat problem as all the panels were similary heated and no problems. I had a long discussion with bill Sawyer last evening in the stunt Hanger chat room and we more or less decided that it must be some type of contaminant that somehow got onto the major roll that I got my supply off of. That might explain why other panels were not affected. Also on a plane that was the second plane prior to this one had a spot similar to this way out in the middle of a wing panel. In that case I blamed it on my using a Mono-cote iron and scuffing the material in that area. That is when I went to using a heat gun.
This next monday or Tuesday I am going to take the roll down to a testing laboratory and have about ten feet rolled off and inspected under UV lighting to see if there is a contaminant.
I did recover that panel (at least poly span is easily stripped) and didn't have the problem this second time.

ONLY THE SHADOW KNOWS
Bigiron

Bill Morell · « **Reply #8 on:** May 16, 2009, 08:44:40 AM »

Marvin, I suspect that you got your roll from MRL? Thats where I get mine. I have never had a problem like this one that you are having. I also use nitrate to stick it down and for most of all the filler coats. Its interesting to me when some people have problems with nitrate. Maybe I have blind luck but I have had no problems with it what so ever. The only time I use a heat iron is to remove little wrinkles that may show up on the curves. At a high setting they just disappear.

Marvin Denny · « **Reply #9 on:** May 16, 2009, 10:41:51 AM »

[quote author=I have never had a problem like this one that you are having. I also use nitrate to stick it down and for most of all the filler coats. Its interesting to me when some people have problems with nitrate. Maybe I have blind luck but I have had no problems with it what so ever. The only time I use a heat iron is to remove little wrinkles that may show up on the curves. At a high setting they just disappear.
[/quote

Bill I agree. I have always used Nitrate for the first coats and never had any problems. The fact that all four wing panels and three out of four tail panels all were trouble free says that it was not the dope nor brush. Also since it showed up only after applying heat THEN dope ays it was not the heat gun. I will know by wednesday at the very latest whether the material has a contaminated spot in it or not. UV light inspection can tell a lot
Bigiron

Doug Moon · « **Reply #10 on:** May 16, 2009, 12:29:20 PM »

Sounds like there was some sort of containment on that piece of polyspan.

I love nitrate. I use SIG nitrate for all my coats up to primer then auto paint. I used butyrate on a plane ONE time. It was a beating. It weighs more and wont penetrate due to the gloss hardener. Has top be way thinner and that means more coats and more time. Who has more time? NOT me.

Jim Pollock · « **Reply #11 on:** May 16, 2009, 05:24:23 PM »

Marvin,

I have never heard of that type of problem with polyspan. Tom uses it all the time here and has never had a problem like that with it! Of course I haven't either, but I use butyrate on it only. It just has to be some sort of contamination.

Jim Pollock

Steve Fitton · « **Reply #12 on:** May 16, 2009, 07:08:16 PM »

Maybe the bat that assaulted Randy Powell's plane on the paint stand migrated down your way and peed on the roll of polyspan?

Doug Moon · « **Reply #13 on:** May 17, 2009, 11:57:22 AM »

Or it could be the bird flew into my garage and crapped on the wing of my Furias while in primer.

Bradley Walker · « **Reply #14 on:** May 18, 2009, 07:33:07 PM »

Next time skip the Polyspan.

Cover the open bay with SLC film (oversize by 1/2" all the way around). Cover with silkspan as normal. Takes about an extra five minutes.

Silkspan easy finish. Bullet proof puncture resistance. Best of both worlds.

john e. holliday · « **Reply #15 on:** May 19, 2009, 10:23:52 AM »

Also takes half the dope. Just remember to scuff up the SLC first. DOC Holliday

Bradley Walker · « **Reply #16 on:** May 19, 2009, 11:44:15 AM »

Quote from: john e. holliday on May 19, 2009, 10:23:52 AM

Also takes half the dope. Just remember to scuff up the SLC first. DOC Holliday

You feel you need to scuff for over covering with silkspan?

Marvin Denny · « **Reply #17 on:** May 20, 2009, 07:15:30 AM »

Update on the "Poly-Span problem.
Results of lab testing of the Roll for contamination was that THERE IS NO SPOTS OF CONTAMINATION ON THE ROLL". Also scraps tested that came from the edge cuttings from around the various panels was that some showed a particulate type of contaminant. That could have been dust or something from the floor as I cut the edges off in the work room.
HMMM!!! Now---- where and how did only one panel (the lower right stab/elevator? come up with contamination and the others were clean?

.

The plot thickens----------THE SHADOW KNOWS!!! I'll find out sooner or later

Bigiron---- although somewhat confused

Jim Kraft · « **Reply #18 on:** May 20, 2009, 07:41:14 AM »

Quote from: Marvin Denny on May 20, 2009, 07:15:30 AM

Update on the "Poly-Span problem.
Results of lab testing of the Roll for contamination was that THERE IS NO SPOTS OF CONTAMINATION ON THE ROLL". Also scraps tested that came from the edge cuttings from around the various panels was that some showed a particulate type of contaminant. That could have been dust or something from the floor as I cut the edges off in the work room.
HMMM!!! Now---- where and how did only one panel (the lower right stab/elevator? come up with contamination and the others were clean?.

The plot thickens----------THE SHADOW KNOWS!!! I'll find out sooner or later

Bigiron---- although somewhat confused

Been there and it don't take much anymore.

john e. holliday · « **Reply #19 on:** May 21, 2009, 07:52:51 AM »

Quote from: Bradley Walker on May 19, 2009, 11:44:15 AM

You feel you need to scuff for over covering with silkspan?

Yes, as it was as the silkspan would lift in places. This is after cleaning with alcohol. DOC Holliday

Bradley Walker · « **Reply #20 on:** May 21, 2009, 05:16:06 PM »

Quote from: john e. holliday on May 21, 2009, 07:52:51 AM

Yes, as it was as the silkspan would lift in places. This is after cleaning with alcohol. DOC Holliday

How can it lift in the open bay? You must be referring to fully covered model. Right?

Doug Moon · « **Reply #21 on:** May 21, 2009, 07:57:24 PM »

He must be talking about SS over SLC. That would make sense. He is saying the SS would lift off the SLC in the open bay areas??

John Ashford · « **Reply #22 on:** May 22, 2009, 12:39:11 AM »

Guys, I certainly don't have an answer to Marvin's problems having never experienced anything like it. In the past four years, I've built 51 planes for myself and customers. Here is my Process:

Four coats of nitrate on the bare wood to seal. Sand LIGHTLY and tack. Apply Polyspan with nitrate and shrink as per Tom Morris's instructions with a heat gun. Six coats nitrate to seal the Poly. Solid wood is covered with med. Silkspan and the same six coats of nitrate is applied. NO sanding between coats. Let the plane gas off for a couple of days and then apply fillets using Super Fil. Let fillets dry overnight. Sand lightly with 180 dry no-fill paper and tack it again.

Spray with Nason brand "Acrylic Laquer surfacer Primer." Sand with 320 dry no-fill paper, tack and start applying color. I use Dupont Chromabase base coat colors and then Nason automotive clear coat. BUT, I have found that with the "Aacrylic Laquer surfacer Primer" you can use Sig, Brodak dope and not have an adheasion problem. The Automotive clear coats will go over dope with no problem.

I do use recommended thinners with all of my paint and I think that is very important.

My own design "Naughty Girl" for P-40 finished today in preperation for the Brodak contest.

Later, John

Marvin Denny · « **Reply #23 on:** May 22, 2009, 03:45:52 PM »

Still no idea of the type or nature of the contaminant nor the way it got on only one small panel.
going to try some other ideas.

got to stop for now--- got a wedding reception dinner rehearsal to attend.

Bigiron

Marvin Denny · « **Reply #24 on:** May 23, 2009, 08:57:28 AM »

Thanks Ty. I don't think that it is the Carbon Fiber as it was in the open bay area between the ribs as well as over the CF. Also it did that only on a single panel and not on any of the others, all of which were covered with the same CF and same dope.
I am sure it was somehow contaminated AFTER I cut the section off the roll and before I put each individual panels on the wing and tail surfaces. The only thing to find now is HOW and WHAT the contaminant is and HOW did it get onto only one panel and not the other seven.
When I get the house returned to normal from the wedding rehersal dinner I will get back on the problem.

Thanks again to ALL the guys on here that tried to help me with the problem rather than try to tell me what OTHER material to use. IF I HAD WANTED TO USE SOME OTHER COVERING MATERIAL, I WOULD HAVE!!! Yes I'm yelling!!!

Bigiron

Marvin Denny · « **Reply #25 on:** May 26, 2009, 08:43:25 AM »

  Well, it appears that the problem is solved------ at least I think I have found the source of contaminant.
  A product titled Resolve----- for pet stainscand odors.
  My wife had used some on an area in that genreal position in the basement (because of a pet "accident". After it is applied, it dries into a powder and absorbs any moisture and odors. It is then vaccuumed up. At least that is what is supposed to have been done. When I cut the approximately 4 foot length from the roll, I laid it on the carpet to draw off the panel shaped for the wing and tail surfaces and the panel for the bottom right tail section was over the spot of carpet that was treated with Resolve, and the static electrical charge in the material drew some particles of Resolve powder that was missed in the vaccuuming. This powder is white and similar to Talc so it went undetected . When I doped the panel onto the surface and then redoped it, the dope/thinner swelled the particles and thus the grainy/rough surface appeared.
  Next time I will leave the large panel on the cutting board to draw off the wing/tail panels .
  While this is not a "positive", I believe that is what happened. There is quite a static electrical charge built up in the Poly Span material when you handle it. Just look at the way it tries to cling to your hands when you work with it.
  That charge will draw almost ANY dust or other loose particles that it gets close to.

  Bigiron

Bob Reeves · « **Reply #26 on:** May 26, 2009, 08:54:58 AM »

Hi Marvin,

My method to prevent this sort of issue is a 6 foot bench covered with a sheet of glass. Before I start cutting any covering, silkspan, carbon, polyspan, Monokote whatever. I clean the whole bench off, scrape it with a razor blade then clean the glass with Windex. Even after all this I still have to watch for balsa dust, cat/dog/human hairs and other unknowns that seem to appear out of nowhere.

Glad you may have found the problem..

Roger Vizioli · « **Reply #27 on:** May 27, 2009, 07:11:35 AM »

Marvin,
Many thanks for finding the cause and providing the update.
Many of us have pets and will remember your findings!
Roger V.
Florida

Allan Perret · « **Reply #28 on:** May 27, 2009, 10:14:55 AM »

Quote from: John Ashford on May 22, 2009, 12:39:11 AM

Four coats of nitrate on the bare wood to seal. Sand LIGHTLY and tack. Apply Polyspan with nitrate and shrink as per Tom Morris's instructions with a heat gun. Six coats nitrate to seal the Poly.

Are you adding any kind of filler material to the nitrate ?
Also, what are you using for application of these 6 filler coats,
regular dope brush or disposable foam brush like some are starting to use ?
Never heard of the Nason brand.
Do you have a link to website that shows product line ?