How can you seal "sanded-into" cardboard?

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Retrospace101

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Hi there, Apparently during a wet sanding session i accidentally sanded into cardboard, Apogee tells me to seal it using CA, but I want to see if you guys have any other ways. I have never sanded into cardboard before and are unsure of what to do.

The black dot you see is a hole plugged with Epoxy, and the white area above is the sanded cardboard. Thank you for your help and good day!
 

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neil_w

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CA. It has become my go-to for fixing scuffed cardboard or paper.
 

neil_w

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Loctite superglue is OK but it is medium viscosity. I too would recommend thin if you can get it, although medium would probably work if you apply it really thin.

Thin CA is typically available at hobby shops or through mail order. Lately I've been using BSI SuperGold, which is expensive but mercifully fume free and give a few seconds to work. I apply with a cotton swab (quickly) in this sort of situation.

Regular thin CA (e.g., BSI Instacure) really hardens fast and fumes like crazy. Gotta be super careful with it.
 

Retrospace101

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Loctite superglue is OK but it is medium viscosity. I too would recommend thin if you can get it, although medium would probably work if you apply it really thin.

Thin CA is typically available at hobby shops or through mail order. Lately I've been using BSI SuperGold, which is expensive but mercifully fume free and give a few seconds to work. I apply with a cotton swab (quickly) in this sort of situation.

Regular thin CA (e.g., BSI Instacure) really hardens fast and fumes like crazy. Gotta be super careful with it.
Some guys tell me go to spray primer over it, is that okay too?
 

mbeels

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I think a layer of primer would be fine. Did it sand through because that part of the tube is raised? Or just a bit too much sanding?
 

Retrospace101

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I think a layer of primer would be fine. Did it sand through because that part of the tube is raised? Or just a bit too much sanding?
Too much sanding...I tried to sand the blob of epoxy to conform with the tube, I sanded the cardboard in the process. it’s also not too deep
 

dr wogz

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CA can also be hard to sad, because it is so hard once cured.. (you can end up sanding away all the stuff around the CA spot as you try to sand the CA spot)
 

Retrospace101

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CA can also be hard to sad, because it is so hard once cured.. (you can end up sanding away all the stuff around the CA spot as you try to sand the CA spot)
Btw, could you (possibly) use wood glue then to fix it?( as a substitute) Like I said its not deep, its as deep as the thickness of one ( or two) paint coats.
 

neil_w

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CA can also be hard to sad, because it is so hard once cured.. (you can end up sanding away all the stuff around the CA spot as you try to sand the CA spot)
That's why thin CA is good for this sort of thing. Rather than building up a bump that needs to be sanded down, it soaks in an hardens so that you just need to gently sand the surface smooth.

But many of the other suggested approaches should work as well.
 

jrap330

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Btw, could you (possibly) use wood glue then to fix it?( as a substitute) Like I said its not deep, its as deep as the thickness of one ( or two) paint coats.
Yes, wood, white or just paint......my concern..what about the hole......intended for something?
 

Steve Shannon

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If you ever get a blob of epoxy again try to chip or cut it off. You'll sand thru almost anything before you sand thru epoxy
Exactly. It’s a klinker! The best way to take down a hard CA or epoxy spot is by filing or using a rasp. There is no conformal tool like sandpaper that doesn’t damage the surrounding material.
 

PatD

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Exactly. It’s a klinker! The best way to take down a hard CA or epoxy spot is by filing or using a rasp. There is no conformal tool like sandpaper that doesn’t damage the surrounding material.
Or if you are lazy like me, a 1/8" rasp bit in a dremel. Gotta keep good control tho, or you won't like the result. :oops:
 

Back_at_it

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If it's not too badly roughed up I would simply prime it a couple of times and move on. What you're going to find is the first coat of primer will create little furry strands that stick up. Do a second coat of primer then knock the furry off with some 400 grit and do a final prime before paint.

If you have gone deep into the paper where it is weak you will need to address that with thin CA or possiably a patch on the inside of the tube. Yours doesn't look that bad but it's hard to tell from the pic.
 

Retrospace101

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If it's not too badly roughed up I would simply prime it a couple of times and move on. What you're going to find is the first coat of primer will create little furry strands that stick up. Do a second coat of primer then knock the furry off with some 400 grit and do a final prime before paint.

If you have gone deep into the paper where it is weak you will need to address that with thin CA or possiably a patch on the inside of the tube. Yours doesn't look that bad but it's hard to tell from the pic.
Exactly. It’s a klinker! The best way to take down a hard CA or epoxy spot is by filing or using a rasp. There is no conformal tool like sandpaper that doesn’t damage the surrounding material.
I think a layer of primer would be fine. Did it sand through because that part of the tube is raised? Or just a bit too much sanding?
[/QUOTE
STATUS UPDATE:

ok guys, I went ahead and sprayed a little primer on the spot, the furry little strands noted By Back at it were taken down by light 320 and 400 grit sandpaper....I also filed the epoxy blob.......However, I ended up sanding the primer exposing more cardboard ( No, the cardboard is just exposed, NOT sanded) and apparently this poses a uncertainty, I have 2 things I can do, either spray more primer or just go with it ( the affected area is on the Launch Rail facing side aka “The Ugly Side” which will anyways be coated black.
STATUS UPDATE :
I went ahead and primed it again, and some furry things came up, but were sanded down, I used sandpaper tightly wrapped around a metal rod as a file, and it worked really good, however, it exposed some cardboard, but I think that can be painted over... however I have 2 options:
Either just go ahead and paint it: It’s gonna be black and it’s on the rail button side, so it doesn’t matter that much




OR



seal it again: Spray more primer and make it perfect



just to notify I am on a big time crunch as I need it to be flyable by this weekend ... the club launch may be cancelled but it may not so.
 
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lakeroadster

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STATUS UPDATE :
I went ahead and primed it again, and some furry things came up, but were sanded down, I used sandpaper tightly wrapped around a metal rod as a file, and it worked really good, however, it exposed some cardboard, but I think that can be painted over... however I have 2 options:
Either just go ahead and paint it: It’s gonna be black and it’s on the rail button side, so it doesn’t matter that much




OR



seal it again: Spray more primer and make it perfect



just to notify I am on a big time crunch as I need it to be flyable by this weekend ... the club launch may be cancelled but it may not so.
Don't "seal it". Just primer it again, lightly sand it with 400 grit, then paint it. You may need 2 additional coats if after the next coat there is an obvious visual indication of where the repaired area is.

Black will show up everything.
 
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