mark schoening

mark schoening

Active Member
OK--I'm a klutz! on tail, flush set slipped and I now have small dent next to rivit. Wait to paint time or ? I can't think of a fix.
 
Your best bet to fill that ding is to use a good body filler not "Bondo" brand but use Evercoat or 3M body fillers. Pirana and Icing putties or surface glaze is not for filling dings, only pinholes in fiberglass or in other minor imperfections. Most automotive paint supply places carry the good stuff. AutoZone does not (well in my area). All of the "heavy" fillers work best (and should always be applied) to bare metal, besure to sand the area with atleast 80 grit before you wipe it on there, otherwise it will flake later on.
Good luck
John
 
Bondo is heavy. More modern fillers use microballoons. Just leave it for now and catch them all just before paint. There will be more.
 
OK, thanks for info, guess I'll store the piece so nobody can see the ding and deal with it at paint time. "there'll be more---???" urgh :eek:
 
More?

Some fly before paint and some paint before fly.....Now you know why.....:)

Frank
7a painted before flight.
 
PainterJohn said:
All of the "heavy" fillers work best (and should always be applied) to bare metal, besure to sand the area with atleast 80 grit before you wipe it on there, otherwise it will flake later on.
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I don't know that there is any agreement on whether to prime first. A lot of auto guys swear by epoxy first, then fill. To each his own, I guess.
 
I repair my dings right away! I hate looking at the stupid things! Also, you might forget where they all are and you will find it after its painted! You will probably make some more dings!
 
If you fill it make sure you sand the area your working on REAL good. Most RVs that I have worked on that have had some type of fill work done to them have not been sanded well. Not sanding correctly will lead to the body filler popping off. I would suggest machine sanding with something in the range of 36 to 100 grit.

Funny story. I had a customer one time insist on me using "aero-dynamic filler" on his plane. I was also instucted to purchase said filler from Cessna. For $100 Cessna sent me 1qt of DYNA-LITE. DYNA-LITE is exactly the same as BONDO. Made by the same company only a different label on the can. I could have purchased the same can of filler at the local auto body supply for $10.
 
Be Careful

KTM520guy said:
If you fill it make sure you sand the area your working on REAL good. Most RVs that I have worked on that have had some type of fill work done to them have not been sanded well. Not sanding correctly will lead to the body filler popping off. I would suggest machine sanding with something in the range of 36 to 100 grit.
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Be careful here!
This is where an auto body guy can ruin your plane. In general, the FAA only allows 10% reduction in skin thickness to remain airworthy.

An enthusiastic (but well meaning) auto body guy used to working with steel can easily remove 0.0025 inch of your aluminum skins, especially with 36 or 50 grit sanding disks. Add some power tools..... :(

I talked to my aircraft paint shop recently about hail damage repair (another Tiger... not mine) and he said it was more expensive because they strip, and then prime, and then fill. This way, when they sand the filler smooth they can see if they are sanding through the primer layer and taking metal off. Hail damage is similar to the dings we are talking about here, perhaps shallower - he said 0.020 to 0.030 inches deep on average.

Care is needed here with the aluminum - part of the reason aircraft paint shops charge more... :)

Gil in Tucson
 
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Yes, you do have to be very careful. You want to get past the point of being lightly scuffed but stop well before the point of sanding a thin spot in your skin. Using tools like die grinders and disc sanders is a good way ruin a good skin panel. Use a DA (dual action) sander for best results.
 
Test

KTM520guy said:
Yes, you do have to be very careful. You want to get past the point of being lightly scuffed but stop well before the point of sanding a thin spot in your skin. Using tools like die grinders and disc sanders is a good way ruin a good skin panel. Use a DA (dual action) sander for best results.
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KTM250guy(?)

I'd be interested in a test case measurement of your technique. It would be easy to do.

Use your DA sander with 36 grit on some 0.032 alclad, and then sand (no burnishing allowed) with a finer grit until the alum. surface is taken down to the bottom of the 36 grit sanding marks.

Then use a micrometer on the test piece... I would think you would be under 0.030 at that point, extremely close to the limit.... 0.002 is not very much metal removal.

gil in Tucson
 
The one thing no one has yet mentioned is that you should never use any Polyester based product. Bondo is polyester based. The reason for this is that it will shrink over time. Your best bet is to use West system and microballoons.
 
gpiney said:
The one thing no one has yet mentioned is that you should never use any Polyester based product. Bondo is polyester based. The reason for this is that it will shrink over time. Your best bet is to use West system and microballoons.
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Good polyester filler, applied properly, will be just fine. The entire auto/motorcycle industry uses it every day. Your new car has a bunch of it and nothing is shrinking. I really think that polyester filler has gotten a bad rap.
 
az_gila said:
KTM250guy(?)

I'd be interested in a test case measurement of your technique. It would be easy to do.

Use your DA sander with 36 grit on some 0.032 alclad, and then sand (no burnishing allowed) with a finer grit until the alum. surface is taken down to the bottom of the 36 grit sanding marks.

Then use a micrometer on the test piece... I would think you would be under 0.030 at that point, extremely close to the limit.... 0.002 is not very much metal removal.

gil in Tucson
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I think I'd like to hear from a filler manufacturer what grit is recommended for prep, and whether or not primer should be applied first. I'm sure they test this stuff for adhesion under various prep methods. Also, 36 grit and a DA on .025 skins (or even .016 elevator) sounds pretty scary to me.
 
I agree....

szicree said:
I think I'd like to hear from a filler manufacturer what grit is recommended for prep, and whether or not primer should be applied first. I'm sure they test this stuff for adhesion under various prep methods. Also, 36 grit and a DA on .025 skins (or even .016 elevator) sounds pretty scary to me.
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Steve... sounds scary to me too... I was just quoting from a previous post... :)

Also, the filler manufacture's data sheet is most likely for steel auto bodies, different techniques are probably needed for aluminum, and may not be in the basic auto body filler data sheet.

The aircraft paint shop that did my Tiger used polyester based filler... I don't agree with the previous posting that says it is not suitable...

gil in Tucson
 
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