Sanding Question

Discussion in 'Low Power Rocketry (LPR)' started by jammer, Oct 15, 2003.

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  1. Oct 15, 2003 #1

    jammer

    jammer

    jammer

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    Got a newbie question on sanding fins. How many times should I seal and sand fins to get a good looking and good flying rocket. I think I remember the Stine book says three times, but want to make sure. Also, how do you know when the fins are good to go and are there any other fin tips or good advice prior to installing them? I already have a fin jig made so at least I know they'll go on straight (lesson learned as a child).

    Thanks in advance!

    Doug
     
  2. Oct 15, 2003 #2

    Ryan S.

    Ryan S.

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    Another Doug!!!! lol


    You can seal the fins alot untill you cannot feel the grain or see and depressions in the fins surface then you will get a glass smooth finish right away. Or, you could partially fill them then let the primer and paint fill in the rest this being the easiest was because you are going to have to prime the rocket anyway. Last you could no seal them at all and have some grains lines in there
     
  3. Oct 15, 2003 #3

    Stymye

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    on balsa
    one thick coat of thinned Fill n finish seems to work well enough
    so far
     
  4. Oct 15, 2003 #4

    Quasar

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    This has been my experience, also. After the Fill n Finish, one good coat of primer, lightly sanded, gives me a perfectly smooth surface ready for paint.

    Mike Fields
     
  5. Oct 15, 2003 #5

    jflis

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    Fill-n-Finish has gotten a lot of good press in the forum here. I also love the stuff, but find it hard to get. It's an Elmer's product and Home Depot type places *should* carry it.

    As for sanding sealer, what I do is apply 2-3 coats, sanding lightly between coats. After I've sanded, I hold the fin under a light, tilting it untill it reflects the light back to my eye. In this way, I can see if there are any imperfections requiring an additional coat.

    Some balsa absorbes more than others, for an *established* number of coats isn't really a good idea. I've had hard-balsa that only needed one coat, so it has to be looked at on a case by case basis.

    hope this helps and welcome to TRF!
    jim

    (SEE!? Do you *see* guys?? I did that WHOLE post without one single plug for my rocket company FlisKits, Inc. at http://fliskits.com/ ! I was good. I didn't decribe our great rockets or wonderful customer service or nothin'! Lordy, but I feel vindicated now!)

    :D :D :D :D
     
  6. Oct 15, 2003 #6

    womblegs

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    I've been reading a lot about fillers, and most of it was in this forum. Can anyone recomend a filler to those of us in the UK?
     
  7. Oct 15, 2003 #7

    cydermaster

    cydermaster

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    I've been using "Fine Surface Pollyfilla", to fill the wood. Then applying a coat, or two, of Sanding Sealer over the top. Prior to priming etc.

    Results have been good, so far; its very effective in filling dents & blemishes in balsa nosecones.
     
  8. Oct 16, 2003 #8

    powderburner

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    There are several old threads on this subject here on TRF.

    The approach I like to use for smooth surfaces is to laminate the balsa fin with copier paper. For extra strength you can laminate with card-stock.

    I pre-fold the paper cover so that it wraps around the fin leading edge. I cut the paper so it hangs over the trailing edge and tip and root by 1/4 or 1/2 inch. I use thinned white glue (Elmer's-type glue) to cover both sides of the fin and then quickly perform the following steps. I insert the glued fin into the folded paper cover and place everything between two small sheets of waxed paper (the kind that your Mom uses in the kitchen) and slip it into the back pages of a thick telephone book. I leave it for a day or so and then begin trimming off the excess paper.

    If you use this approach it helps if you move quickly once the paper becomes wetted with the glue. The longer you leave wet paper laying around, the more it swells (as it absorbs the water) and bubbles up.

    After everything is dry and trimmed, I like to sand lightly, soak the edges with CA, and continue with building the rocket. These laminated fins resist warping and breaking, and sand out quite smoothly after one coat of sealer or primer.
     
  9. Oct 16, 2003 #9

    bsexton

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    The "dry rub" process described by Carl Tulanko looks interesting. I think I will try it on my next balsa project.

    Carl Tulanko's Dry Rub Process
     

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