Tuesday, December 16, 2014

New Long Boat Tail Design? FAIL!

I was playing around with a new design.
Sort of a Sci-Fi V2 style with a much longer tail cone.
This sketch is just a rough starting place.

I'd seen pictures of nose cones being made from body tubes before.
Long triangular pieces are cut out and the long edges joined.
Can't be too hard - right?
The low end of the drawing shows a BT-70 tapering down to a BT-50.

I won't go into too much detail, the end result wasn't that good!

The BT-70 tube was marked for four sections, much like marking for fins with a wrap around marking guide.

The BT-50 engine mount tube was marked in quarters and those measurements made on the low end of the BT-70.

I tried curved cuts first, there was too much overlap at the centers.
Straight cuts were tried and those edges matched up pretty well.

Here's why you've never seen this type of long boat tail in a kit!

The internal and external body tube seams show up when the tube sections are pulled in and joined up.
Oh well, lesson learned. One 9" tube tossed. Back to the drawing board.


  1. So, are you throwing in the towel on this method in favor of something else or are you going to try again?

    I have never tried a tail cone but made one reasonably nice nose cone using a sectioned tube. It is not as uniform as a commercial or home turned cone but looks OK from a distance. I tried this mostly just to do it but it yielded a long L/D cone that would have been hard to make from wood or foam.

    The difference is that, on my cone, I didn't try to get the cuts to line up. I glued the tip together and then used intermediate spacers to set the form. This left gaps that were supposed to be filled with 2-part foam from the inside and then sanded. My foam was old and I ended up filling the gaps with fill'n'finish.

    Here's a link: http://rocketdungeon.blogspot.com/2011/07/nose-cone-from-tube-experiment.html

    PS - I'd lie to see you keep working on this technique. US Rockets had some posts about this on YORF IIRC.

    1. Hi Dick,
      This was something I was trying for a possible new Odd'l kit.
      If it wasn't easy enough I wouldn't put it in a kit.
      I'll check your link and see if I should give it another try.

  2. Yeah, I am not sure about using the techique that I used on a kit. It was a fun experiment though.

  3. Hi Chris, This may work better if you have some supports under each section...like a balsa in the shape of the curve you're trying to achieve and glued to the BT (almost like an internal fin, but only for support purposes). I know that alternatively you can use a nosecone for a boat tail (the Estes Silver Comet did this); however that can be cost prohibitive and also heavy. Regards, Ken (Ken E. Coyote)

    1. Hi Ken,
      I know I could have used internal balsa rib supports. I was experimenting with an idea for a possible new Odd'l Rocket kit. If I couldn't do this easily I doubt another person could comfortably do it either.
      Internal ribs or not, the inside spirals were the weak point
      I've used plastic nose cones for tail cones before but I wanted this one longer than the nose cones that are available.

  4. Hi Chris,
    I just recalled that I tried the same myself last year and it resulted in an ugly mess. The curved tube just doesn't want to bend downwards...the edges become a crimped mess and the spirals also start folding up. Still, kudos to you for trying it... outside the box (or straight tube in this case) thinking is always awesome in my book.
    BTW - Your rockets definitely are "outside the box" and I love them too! :)
    Best Regards,

    1. Hi Ken,
      Well, we both gave it a good shot and had the same results!
      This just shows why the big rocket vendors haven't introduced this method in any kits.