who wants a aircraft based creative challenge?

[vavet]

I'm building a Sonex kit aircraft. It's made mostly of 6061T6 aluminum. I've had some of these parts for 22 years!

The part in question is a rear wing spar. It's 8 feet long and about a 3" wide C-channel with 1/2 inch flanges and 0.025" thick. It is covered in a white protective film, HDPE, i think. This film normally peels off pretty easily, but due to age, thermal cycles, other factors, combination of all of the above, it doesn't want to come off.

I've tried acetone, MEK, tolulene, xylene, and wallpaper stripper. The wallpaper stripper does pretty well if I let it soak for about 15 minutes and then go at it with a plastic razor blade. I've tried using a heat gun. That doesn't touch it. I've tried a heated razor blade scraper from Harbor Freight. I think that helps, but any little mis-step results in a scratch on the aluminum, which is bad. This is an airplane so every scratch is a potential stress riser that would need to be sanded/buffed out.

The wallpaper stripper does pretty well on the 3 inch side part, and even on the flanges, but the bends are a pain, so I'm wondering if there is a better way.

I've thought about connecting battery charger leads about a foot apart to use the aluminum as a big resistor. I could let it heat up enough to hopefully soften it more and maybe scrape away the film with the plastic razor. The problem is that the rest of the aluminum is a giant heat sink and aluminum is a pretty good thermal conductor. Not sure how well that would work and if it would, how much power would it take?

I have to be careful not to overheat the aluminum and have it lose the temper, which I understand starts to happen above 350 degrees F. The higher the temp, the shorter the time it can be exposed to higher temps before it loses temper.

Aluminum is a pretty good electrical conductor too...so it seems like I'd have to push a LOT of current through it to get it to heat up, right?

 

[macgee]

Have you tried Goof Off sticker adhesive gunk remover yet?

It can work really well but best to let it soak in first, a little heat really helps as well. A sharp razor held by hand at about 10 degrees to material to avoid any scratches, this is to start things, and then use plastic Spudgers used on computers to avoid scratches after the Goof Off has soaked in, the key thing is to get some of the the top layer of material off and then reapply and let it soak in again. Its worked for me when nothing else has.

Agree that avoiding any scratches or effecting the heat treatment is key.

EDIT: 3M makes a vicious industrial adhesive remover that works extremely well but forget the model number for it and pricey. Goof Off is cheap at HomeDepot

 

[cvairwerks]

The Van's guys that have had this problem say that a good hit with a heat guy works the best. Heat a general area and slowly peel away. Just don't get it so hot that you can't touch the material.

 

[MatBirch]

what about an eraser wheel? body guys use them to remove vinyl decals.

 

[C91x]

I dealt with that on a workbench top i built and never found an easy way to get it of so I don' have any advice.

What are you planning to power your Sonex with? A couple guys on the field here have the jabiru setup and I know another one a a different field had a VW conversion.

 

[vavet]

Have you tried Goof Off sticker adhesive gunk remover yet?

It can work really well but best to let it soak in first, a little heat really helps as well. A sharp razor held by hand at about 10 degrees to material to avoid any scratches, this is to start things, and then use plastic Spudgers used on computers to avoid scratches after the Goof Off has soaked in, the key thing is to get some of the the top layer of material off and then reapply and let it soak in again. Its worked for me when nothing else has.

Agree that avoiding any scratches or effecting the heat treatment is key.

EDIT: 3M makes a vicious industrial adhesive remover that works extremely well but forget the model number for it and pricey. Goof Off is cheap at HomeDepot

I don't think I've tried Goof Off. There are a bunch of different flavors, but it's cheap enough that it's worth trying. I'll stop and get it container on my way home tonight.

The Van's guys that have had this problem say that a good hit with a heat guy works the best. Heat a general area and slowly peel away. Just don't get it so hot that you can't touch the material.

Doesn't help. It might peel a little, but it breaks up into tiny pieces so it's hard to get much off.

what about an eraser wheel? body guys use them to remove vinyl decals.

I haven't considered this...and I think I have one on my toolbox at home. It's worth trying.

I dealt with that on a workbench top i built and never found an easy way to get it of so I don' have any advice.

What are you planning to power your Sonex with? A couple guys on the field here have the jabiru setup and I know another one a a different field had a VW conversion.

It seems the factory has shifted most of their support to UL Power instead of Jabiru...and there are certainly more options. I love the idea of EFI for ease of operation. If I had to pull the trigger today, I'd probably get the Aerovee turbo. It's a nice compromise between lower cost and decent power.

Thanks for the ideas everyone. Keep them coming!

 

[iajonesy]

How about denatured alcohol ? I t works pretty well on other adhesives.

Mike

 

[Bigblue&Goldie]

Plastic razor blades and Rapid Remover have done well for me on difficult to remove vinyl. I think the problem you're experiencing is getting a chemical to penetrate the plastic, and I'm not sure what will work best, but I can say this stuff has always done better than GooGone in my experience.

https://www.amazon.com/dp/B01MSFD50H/?tag=atomicindus08-20

 

[macgee]

I have to concur with Bigblue,

The biggest problem is getting past the outer layer to reach the adhesive below it. Plastic razors which I called them Spudgers are great and can be used in anger without hurting the aluminum.

Haven't tried Rapid Remover but Goof-Off has introduced more products and changed things up which their product line which has been confusing but the amber colored spray seems to be better than the original, its like a gel. For tough situations I heavily coat the item and then covered it with a totally soaked paper towel with same Goof-Off so it doesn't dry out and let sit overnight. Usually that works really well, the adhesive usually comes right off with a plastic tool. Yours is a tougher material and the trick is reaching the adhesive. Good luck


PS> Here's 3M's version, they have several different types:

https://www.amazon.com/3M-General-Purpose-Adhesive-Cleaner/dp/B00ZIM9XPI/ref=pd_sbs_6?pd_rd_w=rJYtm&pf_rd_p=c52600a3-624a-4791-b4c4-3b112e19fbbc&pf_rd_r=JXX4XY8D4SMNAV1WM7XG&pd_rd_r=fb30d71a-b15a-4a72-be9d-858fe5929fd3&pd_rd_wg=qocyU&pd_rd_i=B00ZIM9XPI&psc=1

 

[shedfullatools]

I've gotten some really stubborn ones off with an eraser wheel on a drill. It sometimes leaves residue on the more stubborn ones but that's where your solvents come into play.

 

[APEowner]

There's a good chance that Toluene would dissolve the coating.

 

[RPH]

Don’t use the battery conduction heating method. Good chance the film will be the only thing left. No control on current flow or pattern makes this dangerous.

 

[IndyGarage]

the resistance process would not be my choice.

I like the eraser wheel idea - it creates its own heat from friction - but you said heat doesn't touch it.

I have a steel scraper blade for my recip saw that I used to take the glue remnants off my pontoon deck - at low speed it works pretty good - and doesn't gouge a flat surface.

They make a tool with a bunch of barbs on it that you roll over the surface of wallpaper so the wallpaper removing solution can get behind the surface - works pretty good. That might help some of the chemicals to soften the stuff up.

 

[PDX]

I'd try a section doing this - lightly hit the top of the film with some sandpaper or something similar (obviously you don't want to go through it), this might allow solvents to penetrate down to the adhesive from above and hopefully make this a lot less painful..

edit: basically similar concept to what was just posted above!

 

[danski0224]

Hand held propane torch, followed by those plastic razor blades or plastic chisel.

Maybe start about 2" off the surface and move at about 1 foot per second. It shouldn't take much. Adjust as required.

Follow with solvent cleanup for remaining residue.

 

[Old Man Roger]

what about an eraser wheel? body guys use them to remove vinyl decals.

Beat me to it, mine works great. The trick is finding just the right speed. Slower is usually better for anything I've used it on.

A magic eraser pad might work in the nooks and crannies too. I've taken pinstripes off cars using both products.

 

[charbar]

Brakleen. Its my go-to for sticky stuff underneath, but I'm not sure if it would work to get the actual plastic film itself off. Might not penetrate the film. Might be worth a shot. Spray it on thick, let it soak for a bit and then hit it with a razor blade. If you're worried about scratches then use a plastic razor blade or a wide plastic trim removal tool. Might need to do it twice. For me it seems to take off stuff better than anything else Ive ever tried. I only use 3M brand brakleen, everything else is a waste of money.

Eraser wheel as others have stated.

What about paint stripper/remover? Might want to double check that its not going to hurt the aluminum though.....
I use it in an aerosol can to remove hard/stuck on paper gaskets. Spray it on, let it soak a bit, then hit it with a razor blade. Really softens up old paper gaskets on cars/equipment.

 

[matt_i]

My idea in combination with above is to machine a sharp outside corner on a piece of delrin/acetal and use the essentially negative angle to push material off as a hand scraping tool (push scrape ala machine alignment scraping) The delrin holds "machined features" very well and resharpening the tool just means taking another cut.

If you don't have Delrin, lexan works reasonably well, not quite as tough but will work. The 1/4" wide edge on a 1/4" thick sheet for example.

my go-to for sticky stuff is CRC "Natural Degreaser" which smells citrus-y. Its not the fastest stuff but if it starts to soften it then the combination of the delrin pusher and the CRC works best and fastest.

 

[vavet]

OP here....I think I developed a pretty effective technique.
The wall paper stripper with the plastic razor blade is pretty good at getting the wide sections cleared.
For the flanges, I switched to the heat gun, which softens the plastic enough to let the plastic blade scrape it, but it leaves a fair amount behind. There is a narrow temp range where it works very well, softened, but not gooey. Once I figured it out, i aimed to keep the temp at the ideal, but most of it came off as goo. It would’ve taken a lot of just right adjustments to keep things at the ideal temp.
Then I tried a variety of chemicals to release what was left. Glass cleaner didn’t touch it. Carb cleaner and brake cleaner worked, but took several reapplications because they evaporate quickly.
MEK didn’t do anything.
Acetone didn’t do anything.
The goof off worked, but slowly. Same for goo gone and paint thinner.
Xylol was the unexpected hero. It didn’t work on the larger areas, I think because it couldn’t penetrate through the film, but once I had it down to just the gooey residue, it worked well. It was a combination of continually wiping with a shop towel soaked with xylol and scraping with the orange scraperite plastic razor blade.

I’m not a chemist. I have no idea how dangerous these chemicals are to get on your skin. With nitrile gloves being scarce and expensive, I opted for these household cleaning gloves.
I still think the battery charger idea would’ve been fun to try, but it’s probably best that I didn’t.

I used a temp gun to check the temp of the aluminum periodically. I saw temps 150 to 180 F range. This aluminum needs higher temps for longer than that to lose temper, so I’m not concerned about that.

Thank you to everyone for the suggestions.

 

[macgee]

Glad to hear you figured out a way but please be very careful, you're working with some nasty stuff; Toluene/zylol has been banned in CA and brake cleaner is also nasty, so is MEK.

Please use good ventilation, a fan or something to keep you from breathing in the fumes and keep wearing the those gloves, its not good for the skin as well.

Maybe try using paper towels or rags soaking in the solvents wrapped around the aluminum and let it sit overnight so when you start the day it's all softened up, ready to remove? This works well with Goof-Off but I use a different one..

 

[BORING HOP YARD]

Hey Vavet, I would recommend these gloves for you https://www.globalindustrial.com/p/...MIqODPvpqU7wIVzD6tBh3bowMmEAQYASABEgKZTvD_BwE If you shop around you may find a better deal. These glove will protect you from the chemicals better than most. I put on a pair and then put on a pair of these https://www.homedepot.com/p/FIRM-GRIP-Nitrile-Coated-Gloves-10-Pair-5510-16/203423243. the outer glove protects the glove next to your skin and it also increases your ability to pick things up. I have been using this process for 10 years. The silver glove protection will last longer than the gloves themselves the outer gloves prolongs the life. I just leave the outer glove on when I slip out of the gloves.

 

[johno]

I have no advice, but i learned there's a plastic razor blade, and an eraser wheel.

 

[earl84]

When I was in the Army they did not allow Simple Green to be used due to some kind of embrittlement of parts. I know Simple Green has not been brought up, but please consider what some of those chemicals may be doing to the aluminum. Is there an EAA chapter near you that you can ask for techniques?

BTW, I think tha Sonex is a cool looking little airplane.

 

[Bigblue&Goldie]

I have no advice, but i learned there's a plastic razor blade, and an eraser wheel.

They sound ridiculous, but I bought a 100pk of plastic razor blades and I seem to use them more than regular razor blades.

 

[jayoldschool]

Only read the first page, but, a steamer will work. Used to remove window tint all the time.