Any tips on slotting tubes?

Discussion in 'Low Power Rocketry (LPR)' started by Gunstar, Jul 10, 2019.

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  1. Jul 10, 2019 #1

    Gunstar

    Gunstar

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    I want to add slots to a BT-80 so I can have through the wall fins. Any tips or tricks on doing that well?
     
  2. Jul 10, 2019 #2

    kuririn

    kuririn

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    After you've measured and marked your slots on the tube:
    1. Use an angle tool to get straight cuts with your knife.
    2. Use a sharp, preferably new, #11 blade.
    3. Make several passes, cutting deeper with each pass.
    4. Since the standard BT-80 is not a thick walled tube like the midpower ones consider using a sacrificial coupler inside when making your cuts. This supports the inside of the tube and guards against paper tear through when the blade goes through the inside.
    I look at slotting tubes like I do assembling plastic parachutes: not particularly difficult but B-O-R-I-N-G!
    I tend to use pre-slotted tubes and assembled parachutes whenever possible. Cheers.
     
    hcmbanjo likes this.
  3. Jul 10, 2019 #3

    K'Tesh

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    For me, I mark the tube with a mechanical pencil, using the appropriate guide. To insure that the lines are straight, I use a piece of angle aluminum. I then mark top of the slot and the bottom of it. I cut the tube along the marked line, then use the fin (pressed into the slit) to mark the width of the slot. Finally I cut the other slit... Taking care to make sure that I stay on the same side of the slits for all the slots... and finish the slot.

    It is important to use a sharp Xacto blade, and make several light passes to cut the slits, rather than trying to cut it in one single hard pass.
     
    Last edited: Jul 10, 2019
  4. Jul 10, 2019 #4

    JJSR

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    Inside I use rolled up newspaper or old catalogs, so not too tear through.
     
  5. Jul 10, 2019 #5

    JonathanOtt

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    Once you have measured and marked, measure again, then once again.

    I measured and marked a 4" tube out for three 1/4" slots. I cut it, and when finished and doing a dry fit, realized that when marking the tube, I somehow got 1/4" off...resulting in one slot 1/4" off, and the third 1/2" off.

    Turns out that once I marked the three lines on the tube, then went to mark another line 1/4" from each line, I apparently marked 1/4" to the right of my mark for one slot, then marked 1/4" to the left of the next one. :eek:

    Yeah.

    :mad:
     
  6. Jul 10, 2019 #6

    heada

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    Backing up the cut with either a coupler or something like rolled up newspaper will give a much cleaner inside surface and help prevent crushing the tube if you use too much force. Much easier to make several light passes that way too.
     
  7. Jul 10, 2019 #7

    rharshberger

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    +1, I keep a few extra couplers of each size on hand, both for cutting slots and for cutting tubes in my jig (Kuhn-style jig?). The coupler makes for nice clean cuts and no tearout on the interior of the tube.
     
  8. Jul 10, 2019 #8

    neil_w

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    What I like to do is make a plunge-cut at each end, and then put in the coupler (or whatever) and do the long cuts.
     
  9. Jul 11, 2019 #9

    A & B Model Rocketry

    A & B Model Rocketry

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    I did those on a build and I used part of a toilet paper roll cut to size and mounted inside to fortify the body tube walls. Also helped to give a little more strength to the fin attachment.
     

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