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Gotta finish a SUPER rough tube in record time... HELP!!!

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BsSmith

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Well, I kinda messed up my fiberglassing with my scratch rocket. (Running With Scissors) Stucturally, it's great, but finish wise, not good at all. I want to launch the rocket at NSL in May, plenty of time for some people, but for me, I am an extreme perfectionest whan it comes to finishing rockets, and I don't have much time to sand/paint every day. I'm trying the Kilz-sand down-repeat method now, but that's taking it nowhere fast. I have Aeropoxy light filler, I could use that, but it doesn't go on all too smooth. the fins are another problem. Instead of putting fillets on them, I decided to use fiberglass to bond them to the motor tube and I use a bit too much glass. The filler I put on the fins isn't helping too much and if I sand down the glass, the fins will probably shred off on it's transonic flights to come. It seems like I have a lot of work to do... Any suggestions to speed up the process a bit?

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stickershock23

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heres my jig for sanding. I use an old corded drill and some 60 grit sandpaper, it will cut through junk in no time flat.

be careful sometimes it goes to fast, I have sanded all the way back to cardboard once. LOL

one things for sure, super smooth super fast. I finish it up with one of those sponge block sanders. about 220 grit. prime and sand lightly!

http://www.youtube.com/watch?v=t8g_kdUlqJ4
 

troj

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Auto body filler is the answer to your woes. If you use the two-part stuff, you can vary the amount of hardener, to control how fast it cures, and thus how soon you can send.

Use it outside and wear a respirator!

Once it's cured (it gets hard, but in my experience, the surface stays slightly tacky), wet-sand it down to the level you want.

As you get practiced with the applicators, you'll find that the spots on your tube require minimal sanding afterwards.

Spot putty works, too, but it has a longer drying time.

-Kevin
 

stantonjtroy

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BONDO my friend. There is another product that goes by the trade nam "Top Stop Gold". The top stop rocks. Cures in about 10min and sands like balsa with a 120 grt dry. Then clean out the scratches with 320. You can get it at any of the better auto body suppliers.
FWIW

Troy
 

Pat_B

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StickerShock has the right idea. Somehow you'll need to get the tube rotating in order to keep it looking round. Otherwise, you'll end up with a lumpy looking tube if you just sand without rotating it.
 

BsSmith

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StickerShock has the right idea. Somehow you'll need to get the tube rotating in order to keep it looking round. Otherwise, you'll end up with a lumpy looking tube if you just sand without rotating it.
If I could rotate it, I would. The rocket is already built with the fins, motor mount, and coupler installed. Making something to hold it would be difficult and it wouldn't be sanded around the fins.
 

Pat_B

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You could make a mandrel that fits inside of the engine mount then gets larger inside the main tube (coupler stock). Then, hand sand the part around the fins.
 

stickershock23

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Just name the rocket "Lumpy" and fly it like that... LOL

(Sorry I just had to say it)

sounds like bondo is the answer. next time smooth the tube before you build in the fins.

good luck!
 

BsSmith

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I put a coat of Aeropoxy filler on the tube, seems to be doing a good job. I will still need work though, lots of primer.
 

troj

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You can get away with not spinning it by using a flexible sanding pad that you put behind the sandpaper. This will allow you to flex the sandpaper to match the curve of the tube, and spread the sanding surface area.

Trying to use just your hand results in uneven pressure and bumps.

-Kevin
 

Graham Orr

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If you go the sanding route:

Be sure to wear gloves and a particle mask. That stuff will really irritate your skin and tear up your lungs.
 
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