Sea Tiger

Discussion in 'Low Power Rocketry (LPR)' started by Bruiser, Jul 12, 2019 at 2:26 AM.

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  1. Jul 12, 2019 at 2:26 AM #1

    Bruiser

    Bruiser

    Bruiser

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    Having finished my latest design (Tempest in the multi stage forum) I have been deciding what to build next. I have been thinking about picking back up a project that stalled or building an upscale Shrox design. Earlier today I gave up on finding a file for one of the Shrox designs that I liked and I started working up my own design inspired by the Shrox's designs.

    I am calling it the Sea Tiger. It's BT60 sized, just under 24 inches long and has a 24mm motor mount.

    My build should start tomorrow. I'm very excited!

    BTW, the engine pod under the body tube is the "scale" location. The mount is in the main body tube.

    Sea Tiger 2.JPG

    -Bob
     
  2. Jul 12, 2019 at 7:09 AM #2

    kuririn

    kuririn

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    Looks like a sea borne cruise missile. What's up with the naval designs? Are you a Navy vet by chance?
     
  3. Jul 12, 2019 at 1:39 PM #3

    BABAR

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    Cool!
    Gonna put a motor in the pod and cluster it?
     
  4. Jul 12, 2019 at 2:09 PM #4

    Bruiser

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    What's up with the naval designs?
    I don't know. I didn't even realize it until you mentioned it. Maybe I've been listening to the Village People too much lately :)

    Are you a Navy vet by chance?
    No, I'm actually retires Air Force. Almost joined the Navy though right out of high school but the recruiter pushed too hard and spooked me :)

    Gonna put a motor in the pod and cluster it?
    No, but it was tempting. I've read up on offset thrust lines and such but I am going to save that for when I build the Interceptor with the booster :)

    -Bob
     
  5. Jul 12, 2019 at 7:05 PM #5

    BABAR

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    That minimal an offset isn't much of a problem, in my experience. That's my routine with long gap stage rockets.

    It's when you put motors in pods at the outside edges of the fins that you get into trouble.

    Problem with your design (if you cluster) is the open forward end of the tube. Best be would be plug the tube forward of the tube and eject the motor, use zero or short delay (best bet, even a zero delay motor should eject and that's less mass slowing down the rocket, dumps it on the upward trip before the main engine deploys the chute).

    If you use a long delay and deploys AFTER the main deploys the chute, could potentially get "interesting."

    "interesting" is generally not a good thing in this scenario.
     
  6. Jul 13, 2019 at 2:22 AM #6

    Bruiser

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    I'm not going to cluster or stage this one. Once I graduate to electronics I will probably stage this:
    Estes Interceptor with Booster Page.PNG

    In the meanwhile, I'll just plug away at my simpler models.

    I bought the motor mount today. I made the centering rings from a couple layers of poster board and I bent up a motor retention spring thingy

    I also cut out the wings and fins. I papered them with Avery label paper.

    I filled and sanded the spirals on the main body tube.

    I built the "engine pod" and have it ready to primer.

    I also made a "coupler" from a couple layers of poster board. It' not going to be used as a coupler though. It will be a ejection baffle instead.

    Sorry no pics. I'll get some Monday.

    -Bob
     
  7. Jul 13, 2019 at 2:22 AM #7

    kuririn

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    This actually looks more interesting than the Tarmon. I see you've replaced the big ventral fin with the faux motor tube. Will be looking forward to this build.
     
  8. Jul 13, 2019 at 3:51 AM #8

    Bruiser

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    I went to the Space Museum yesterday to look at the Lance on display, but that's another thread. While I was there I noticed this rocket.
    XQ 4A.jpg


    I had already been thinking off designing something like the Tarmon, Sea Snap or DetlanX. When I saw this display, I decided my design would have a engine pod like this.

    -Bob
     
  9. Jul 15, 2019 at 1:17 AM #9

    BABAR

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    The pic makes it LOOK like there is a big CHAD staged Estes cardboard motor in the pod!
     
  10. Jul 15, 2019 at 2:11 AM #10

    Bruiser

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    The front looks just like the back. I thought about some sort of boat tail on my rocket but the CP and CG were just right without one. If I had added a chopped off nose cone back there I am sure I would have needed more weight up front.

    Some of these type of drones/test rockets had both a rocket motor and some sort of jet engine. The rocket motor would fire to help get it up to speed then the same jet engine would take over flying it.

    -Bob
     
  11. Jul 15, 2019 at 8:58 PM #11

    Bruiser

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    I have glued in the motor mount and the baffle. I didn't take pictures of the mount but here's the baffle:
    Sea Tiger Baffle A.jpg
    Sea Tiger Baffle B.jpg


    I also have the fins on and am working on the fillets now.
    Sea Tiger Fins On.jpg

    -Bob
     
  12. Jul 15, 2019 at 9:57 PM #12

    neil_w

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    In the current design it appears as if the rocket has no fin area extending below the rocket, although it's hard to tell exactly what's going on with the tail there. You will have the pod hanging down there, though I haven't figured out from discussion above whether it'll be open or closed (or if it's long like the photo it may *behave* like it's closed; that's pretty long and skinny for a tube fin. Either way I suppose the pod will pull the CP down a bit, maybe not too much different from a fin (depending on final shape).

    I'm never quite sure how much of a problem this might be. The good old Estes Firecat has only a pod hanging down, but it is short and open and should be functioning as a pretty effective tube fin.

    Just pondering.
     

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