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covering turning yellow

Old 04-11-2006, 09:44 AM
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bobnreg
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Default covering turning yellow

Hi guys, I have a covering problem which someone has an answer to. I covered a wing panel with Nelson Color Fab white [ an excellet material to work with] and sealed it with Minwax fast drying Polyurethane . After drying the covering has turned slightly yellow. I could live with it over a colored section but over white it stands out like a sour thumb. The problem is how to remove the urethane so that a different sealer could be used. I tried lacquer thinner also acetone neither seem to work. The last resort is to remove the covering and recover. I really dont want to do this as you all know what a pain this would be. Suggestions welcome Thx BOB D.
Old 04-17-2006, 03:08 PM
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Default RE: covering turning yellow

Hi Guys . Just wanted to share with you a solution to removing urethane sealer from fabric covering on wing panel. I metioned I tried lacquer thinner--------- well yes it does remove the urethane .Here is what I did--- I used lacquer thinner but put it on with a pad of steel wool and rubbed until it became soft then using a towel rubbed until removed. A nice way to get out of a mess. Will now reclean surface with alcohol then reseal with clear sealer. Thought you would like to know. Bob D.
Old 04-18-2006, 09:08 AM
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LesUyeda
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Default RE: covering turning yellow

Water based polyeurathane is water clear, not yellow like that you used. It is also fuel proof to at least 15% nitro.

Les
Old 04-18-2006, 09:45 AM
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Campy
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Default RE: covering turning yellow

Water base polyurethane is fuel RESISTANT, not fuel proof.

With water base poly you need to let it sit for a minimum of 7 days BEFORE exposing it to glow fuel.

Do not let the residue stay on the finish for more than 4 hours. After 4 hours the finish begins to soften.

As long as you follow the above caveats you will have no problems. I use the water base poly (Minwax Polycrylic) frequently and this is what I have found from experience.

Hope this helps.
Old 04-18-2006, 10:05 AM
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Deadeye
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Default RE: covering turning yellow


ORIGINAL: Campy

Water base polyurethane is fuel RESISTANT, not fuel proof.

With water base poly you need to let it sit for a minimum of 7 days BEFORE exposing it to glow fuel.

Do not let the residue stay on the finish for more than 4 hours. After 4 hours the finish begins to soften.

As long as you follow the above caveats you will have no problems. I use the water base poly (Minwax Polycrylic) frequently and this is what I have found from experience.

Hope this helps.
I'd sure like to know what I did wrong, then. I tried it once, let it sit for 2 weeks; the Polycrylic was gummed up and ruined after the first flight. It was exposed to the exhaust of 15% for less than 15 minutes. I'll never use it for fuelproofing again, but it is great for fiberglassing.
Old 04-19-2006, 06:36 PM
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bobnreg
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Default RE: covering turning yellow

Hi Guys thank you for the usefull info, I'll take it to heart. Campy in your thread you mentioned not to let the residue stay on for more then 4 hours. Would you expand on this ,I don't understand what is meant by this specifily , what residue stay on what finish. Thanks for your responce. Bob D
Old 04-20-2006, 09:13 AM
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LesUyeda
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Default RE: covering turning yellow

What I used was made by Behr. The plane was made in 1997, and is still holding up just fine, even in the exhaust trail. Perhaps all manufacturers are not equal?????

Les
Old 04-20-2006, 12:36 PM
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Default RE: covering turning yellow

ORIGINAL: bobnreg

Hi Guys thank you for the usefull info, I'll take it to heart. Campy in your thread you mentioned not to let the residue stay on for more then 4 hours. Would you expand on this ,I don't understand what is meant by this specifily , what residue stay on what finish. Thanks for your responce. Bob D
I am refering to the exhaust residue from the engine.

I realize this sounds gross, but there are some people that don't bother to clean their planes at the end of the day/session, they wait until just before they go out to fly - the residue may stay on the plane from overnite to several days.

Also, as with almost any finish, raw fuel on the finish is going to damage it.
Old 04-20-2006, 12:38 PM
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Default RE: covering turning yellow

ORIGINAL: Deadeye


ORIGINAL: Campy

Water base polyurethane is fuel RESISTANT, not fuel proof.

With water base poly you need to let it sit for a minimum of 7 days BEFORE exposing it to glow fuel.

Do not let the residue stay on the finish for more than 4 hours. After 4 hours the finish begins to soften.

As long as you follow the above caveats you will have no problems. I use the water base poly (Minwax Polycrylic) frequently and this is what I have found from experience.

Hope this helps.
I'd sure like to know what I did wrong, then. I tried it once, let it sit for 2 weeks; the Polycrylic was gummed up and ruined after the first flight. It was exposed to the exhaust of 15% for less than 15 minutes. I'll never use it for fuelproofing again, but it is great for fiberglassing.
I don't know what happened. It is possible that you happened to get a bad can of it.

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