Scratch Build - Delta II Rocket - 56mm tube

Discussion in 'Low Power Rocketry (LPR)' started by ToneDeafJunior, May 4, 2019.

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  1. May 4, 2019 #1

    ToneDeafJunior

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    So, I've been trying to figure out, do I want a lathe or do I want a 3D printer? I've done nothing but go back and forth in my head for months and months and months. I figured I would not have the patience or the know how to make rocket parts I wanted on a 3D printer. Most of the parts on Shapeways and other sites are so expensive. Thus the dilemma. Well, I finally broke down and purchased a small lathe to turn nose cones/fairings. The first rocket will be the Delta II in the 742X-10C configuration. I'm using the Delta II Pathfinder paper pdf I downloaded for the skins and up scaling them to fit the main body tube of a BT-70. This should make the rocket a little over 36 inches finished. I understand the Pathfinder rocket was a 79 configuration, but I cannot find a paper model with the 74. I'll just do my best. I do plan on blocking out the Pathfinder logo but will probably keep the 298 number and the stars.
    I went around my elbow to my arse, but, here's what I did to make the below files. I took a screenshot of whichever page from the pdf and pasted it into MS paint. I know, old school. This is the only way I knew how. Anyway, I cut out each of the 4 skins and then created .pdf to print from. I could not get the alignment right with adobe up scaling so I just inserted them one by one in MS Word, centered them and then increased the print size. Since my shaky hands could not cut them out all the same size, I had to print on B&W paper, altering the percentages and test fit them on the 56mm tube. The percentages were between 222 and 225 percent of original.
    I've done the maf and BT-50 tubes are super close to scale for the 4x Graphite-Epoxy Motors. I have some 12 inch balsa blocks on order and should be here sometime next week. That's what I'll make the fairing out of with the new lathe. Wonder how many I'll screw up before getting it right/acceptable enough for a model rocket. I'll CWF the fairing, sand and then paint. Don't how much nose weight I'll need. I guess I'll have to figure out how to attach it to the balsa too. Plus the weight will not be at the forward end of the rocket. I haven't done the maf on the fairing yet, but, I bet it'll be 8ish inches long. CP and CG might be awfully close. I'm sure I'll have a few people suggest openrocket ,but, OR doesn't support boosters. I ran into the same thing making the SpaceX/Boyce Aerospace FH. I digress.
    I plan on using a 24mm motor mount and adding 3x clear fins to the bottom for stability. Any suggestions you might have will be appreciated but might not be used with my limited abilities. Let's see how it goes.
     

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  2. May 4, 2019 #2

    ToneDeafJunior

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    Here's what the sheets looked like after printing. Constructed the 4x GEM cones to be placed on the BT-50 tubes.
     

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  3. May 5, 2019 #3

    ToneDeafJunior

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    Most of the easy work is complete. Motor mount finished and glued. I decided to go with the ICEsat-2 decals since the rocket is the Delta II 742X-10C configuration. I printed one extra sheet and covered up the Boeing and Pathfinder logo. I added the flag and the ICEsat logo. All in all, I'm pretty happy with the progress. Now to work on the GEM's. Hopefully the balsa will be here this week. We'll see how my first turning job goes.
     

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  4. May 7, 2019 #4

    ToneDeafJunior

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    Working on the 4x motors. Sized the BT-50 tubes, glued the cones on and let sit. Used the centers of the 24mm centering rings as the bottoms of the motors. Glued and let sit. Applied CWF to the cones. After drying, I'll sand and see how they turned out.
    Going to cut down the small block of balsa on the table saw in 4 pieces to turn the 4 nozzles on the lathe.
     

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  5. May 9, 2019 #5

    ToneDeafJunior

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    The GEM's turned out okay. I'll need to spray again and sand lightly. Started my first lathe project this afternoon. The nozzles are coming along. As soon as I get 4 that I like, I'll CWF, lightly sand and paint.
     

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  6. May 9, 2019 #6

    linville86

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    Looking good so far. That will be an impressive rocket for display and flight. What paper are you using for the wraps?
     
  7. May 9, 2019 #7

    ToneDeafJunior

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    I'm using PACKZON®️ Shipping Labels Full Sheet with Self Adhesive, Square Corner, For Laser & Inkjet Printers, 8.5" x 11" White, (100 Labels) ordered from Amazon. I'm finding that the corrections I made, stickers over stickers, with the flat spray on the labels, doesn't stick very well and I'm having to use white glue to attach and a damp rag to wipe off the excess. I believe I sprayed my labels too much. I needed to take a brush to brush off the prints afterward. Model and learn I guess...
     
  8. May 11, 2019 #8

    ToneDeafJunior

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    I'm really happy how the nose cone/fairing turned out. Many calculations to get the scale right and I'm satisfied with the product. CWF'ing the cone tonight and sanding tomorrow. Still working on getting 4x nozzles that are acceptable. Going to start the clear fins tomorrow.
     

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  9. May 12, 2019 #9

    ToneDeafJunior

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    I'm pretty happy the way the fairing turned out. A first lathe attempt in which I am satisfied. As for the nozzles, wishful thinking that 4 small blocks were enough. I went through 10 to get 4 similar. I attached 8 small pieces of balsa to the GEM's to secure to the first stage. I'll let dry, glue on the nozzles and then paint.
    Wondering what shape fins would be best for the clear plastic? I plan on making 3.
     

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  10. May 12, 2019 #10

    ToneDeafJunior

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    One suggestion when applying the paper is to remove the back and place sticky side up on the bench. Then take the backing/wax paper that was pulled off and cut in in half. Reapply the wax backing to the stickers with about 1/2 inch left in the middle. 1/4 inch extra on the sides. This will allow the stickers to be lined up accurately without worrying about the rest of the decal sticking. Soon as the pencil marks on the tube and paper line up, push the middle on the tube. Then remove the reapplied wax paper and roll the decal on the tube. This technique seems to work well.
     
  11. May 13, 2019 #11

    ToneDeafJunior

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    A bit more filling and sanding and they'll be ready to be installed.
     

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  12. May 15, 2019 #12

    ToneDeafJunior

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    The GEM's are installed. Now to work on the fins. I ran the model through OpenRocket without the GEM's of course and tried to maximize the distance between the CP and CG with fin design. You can see from the picture the distance is only 9.8 cm between the two. You can also see the fin design. I'm using acrylic sheets and will cut them to size on the table saw. Speaking of the table saw, on Sunday, my middle fingah on my left hand had a battle with the blade. It lost, but should heal in a couple of weeks. Makes typing awfully tough though. Anyway, I don't know if the drag of the GEM's will push the CP forward or back. I'd like to make the rocket as stable as possible, but, I believe it's impossible to do in OR with GEM's, boosters, etc. Anyone know the answer as to forward or back for the CP?
     

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  13. May 15, 2019 #13

    ToneDeafJunior

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    Forgot a picture.
     

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  14. May 15, 2019 #14

    Ez2cDave

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    "Split the difference" and get a CNC lathe . . .

    Dave F.
     
  15. May 17, 2019 at 3:36 AM #15

    ToneDeafJunior

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    Cut the fins out and airfoiled the leading edge. Took a drill and drilled for a 3/4 inch dowel and glued it 1 inch in the nose cone and pre-drilled for a screw eye. Hopefully this will hold.
    I also could not wrap my head around why this model is about 4 inches taller than I expected. I took out Peter's book and verified that the dim's I had on total height were wrong. That's what I get for trusting a strange internet. Model is just over 40 inches.
     

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  16. May 17, 2019 at 8:26 PM #16

    wrad

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    Fantastic build, your booster with the canted nozzles look rely great.

    I have a couple of suggestions for you questions.

    For the nose weight to get it as close to the front as possible drill a 10mm ish hole approximately 75% of the length of the nose cone into it then drop in the required amount of lead shot and chase with epoxy.

    To get a rough estimation of what your SRB's will do to the CP, sim both the rocket without any side booster and get the distance from the bottom of the rocket, then sim a single side booster and get the CP from the bottom of the booster. if you compare the two distances it should give you an estimation of which direction the CP will move. If the CP for the booster is further from the bottom than that of the main rocket, it should move the CP forward and vice versa. I hope this explanation makes sense. This method doesn't account aerodynamic differences caused when the two are combined so is just a rough estimation.

    Finally as with my Soyuz build, doing a good old fashioned swing test will tell you a lot about the stability very quickly without having to spend hours trying to get a super accurate simulation.
     
  17. May 18, 2019 at 8:23 PM #17

    ToneDeafJunior

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    I took Wrad's suggestion and drilled the nose cone. I used E6000 and fishing split shot to add nose weight. The parachute system was installed as well as 2 launch lugs 3/4 inch off of the booster with the acrylic airfoiled on the leading edge. I really 'gooped' the E6000 on the fins hoping they will hold in flight with an Estes E12-4 motor. The fins are not 120 degrees apart. I do remember reading somewhere that the most important thing is not to have them off 90 so we'll see what happens in flight.
    I haven't done through body fins on a scratch build. Seems these fins are large enough where the rocket would benefit from them. Anyone know how to install acrylic through body fins? I would not be able to use fillets due to the clear plastic. Would the fins go all the way through and glue to the motor mount or just hook in like the SpaceX Falcon 9 model? I really think these fins have a good chance of ripping right off in flight.
    Almost finished.
     

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    Last edited: May 18, 2019 at 9:45 PM
  18. May 18, 2019 at 11:01 PM #18

    Ez2cDave

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    "Internal fillets" . . .

    https://www.rocketryforum.com/threads/are-internal-fillets-really-necessary.135825/


    Dave F.
     
  19. May 19, 2019 at 12:45 AM #19

    OverTheTop

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    For working balsa in the lathe you might want to try using something like a Dremel as the tool, with a wood carving bit, at the toolpost. I usually use a flexdrive shaft for this on my metal lathe.
    26.JPG
    Would be a little different on a wood lathe, but might be worthwhile to try.

    I have also been known to use a dental drill ($130 on eBay), with diamond bit, as a toolpost grinder when working fiberglass. Toolpost grinders are an underutilised technique I think.
     
  20. May 20, 2019 at 2:16 AM #20

    ToneDeafJunior

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    Finished product. I'll post a flight video when I can.
    25 Delta II.jpg
     
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  21. May 20, 2019 at 3:26 AM #21

    OverTheTop

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    That looks seriously nice! :cool:
     

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