Oblique/(Offset) Paper Cones?

TopRamen · Feb 28, 2016

I've read everything possible about making the oblique paper comes that I will need for my SA-5 Gammon build, and then I even fidgeted about with some paper and made something that would work with a little extra help from finishing methods.
However, does anyone simply have a template or pattern to share with me.
I read the Apogee Newsletter Article by TVM about making them, and it gave me a headache, which is what happens when I think about math.
In the article, all sorts of math gets talked about, then finally, on page five, there is a pic of the cone, but you can't "Save Image As" on those articles.
I gues I could take a picture of the screen, then mess with that image. :facepalm:

This is kind of a yes or no question, but if you have a really simple method that does not require me to get a math headache, I'd welcome any suggestions.
I'm also ordering 3" BT-55 nose blocks from BMS, so if I have to i'll just shape them by hand from the Balsa stock.

Thanks in advance for any suggestions or advice, but what I'd love the most would just be a scan of something like what comes with the Fliskits Thunderbird, then I can just resize it and mess with it til I get some nice ones.

Dave

McKailas Dad · Feb 28, 2016

TopRamen said:
I've read everything possible about making the oblique paper comes that I will need for my SA-5 Gammon build, and then I even fidgeted about with some paper and made something that would work with a little extra help from finishing methods.
However, does anyone simply have a template or pattern to share with me.
I read the Apogee Newsletter Article by TVM about making them, and it gave me a headache, which is what happens when I think about math.
In the article, all sorts of math gets talked about, then finally, on page five, there is a pic of the cone, but you can't "Save Image As" on those articles.
I gues I could take a picture of the screen, then mess with that image.
This is kind of a yes or no question, but if you have a really simple method that does not require me to get a math headache, I'd welcome any suggestions.
I'm also ordering 3" BT-55 nose blocks from BMS, so if I have to i'll just shape them by hand from the Balsa stock.

Thanks in advance for any suggestions or advice, but what I'd love the most would just be a scan of something like what comes with the Fliskits Thunderbird, then I can just resize it and mess with it til I get some nice ones.

Dave

Oblique, or -ogive-? I'll get you some links in a minute, but if you want to look in the meantime, check out my '10" diameter paper rocket' and a couple others I posted. Search 'paper ogive nosecones' too, that's one I did a while back...

https://www.rocketryforum.com/showthread.php?26305-Paper-Ogive-Nose-cone

Sooner Boomer · Feb 28, 2016

McKailas Dad said:
Oblique, or -ogive-? I'll get you some links in a minute, but if you want to look in the meantime, check out my '10" diameter paper rocket' and a couple others I posted. Search 'paper ogive nosecones' too, that's one I did a while back...

https://www.rocketryforum.com/showthread.php?26305-Paper-Ogive-Nose-cone

He needs a conical NC whose point is off center (not centered in bore of body tube).

I've made my own. It just takes some playing around. There's a thread on it somewhere (scratch build? cardstock?).

Crumb fire · Feb 28, 2016

3d printed helped in my case. Not very expansive. 29mm.

rocketguy101 · Feb 28, 2016

You can layout an ogive graphically...you will probably end up needing a way to draw big arcs (like McKailas Dad discussed on some of his build threads)...that is why I went with the "math route" in the PoF articles (#409 and 410)...

Here is the basic layout of the tangent ogive (that SA-5 looks like it might actually be a secant ogive but this would be close, most people use a tangent ogive for Phoenix models). You will know D from your body tube, and L will be scaled from the photos. Draw two intersecting lines (L1 and L2) which will be the centerpoint of your arc

EDIT: doh! I see now you are talking about the side pod cones...sorry...yeah the layout is pretty complicated! https://www.apogeerockets.com/education/downloads/Newsletter127.pdf

danielsadjadi · Feb 28, 2016

3D printers are everywhere now. I'd bet somewhere there's someone who has one and is able to lend you it. Just make a file on a program like TinkerCAD, print it out and sand it down. Hope you find someone.

rocketguy101 · Feb 28, 2016

OK, I made a BT-55 cone, with a 30 degree angle (best measure from one of your photos in the build thread)...due to the CAD limitation, I can't make it go to a complete point and still get the flat pattern, but see if this helps...the pdf should be printed full scale (or no scale for letter sized paper)

View attachment ObliqueCone.PDF

rocketguy101 · Feb 29, 2016

I worked on the modeling technique, and got a little longer, pointier end. Those circled dimensions are the main cone dimensions like I said scaled from one of the photos...I cut one out and rolled it, and it seems to fit a BT-55 OK. Plus I put 4 patterns on one sheet of paper so you'll use less paper...

View attachment ObliqueCone_rev A.PDF

MCriscione · Feb 29, 2016

To get a cone like the one shown in Crumbfire's post, You actually use a 'right circular' cone (i.e., they type most people think of when you say a 'cone). The reason is that when you cut a section across a cone at an angle, you don't get a circle (to match your BT diameter); you get an ellipse instead:

What you actually need is an oblique cone. As it turns out, there's no convenient formula for calculating the surface area of an oblique cone. There's some formula involving an elliptical integral (see here, it's too much math for me: https://mathforum.org/library/drmath/view/55017.html)

The method described in the apogee newsletter for creating an oblique cone using radial line length is probably your best bet. It is also described in the following video (although not really any clearer, and apparently without sound or narration) https://www.youtube.com/watch?v=KxXl35SXPAs Alternately, perhaps this would help: https://local.ecollege.ie/Content/A...es/module6/Radial Line Development_M6_U11.doc

Good Luck

TopRamen · Mar 1, 2016

rocketguy101 said:
I worked on the modeling technique, and got a little longer, pointier end. Those circled dimensions are the main cone dimensions like I said scaled from one of the photos...I cut one out and rolled it, and it seems to fit a BT-55 OK. Plus I put 4 patterns on one sheet of paper so you'll use less paper...

Just printed a sheet, cut one out, formed it and held it to some BT-55.
These will work great!!!! THANK YOU!!!

The base is actually the slightest bit small, as it fits into the BT-55, but that's fine, as I can enlarge them 1% or just add a millimeter or two as I cut them out.
I'll be making a few different "Test Boosters", til' I get something that looks good, so now I don't have to worry about the Cone part, or hacking up a bunch of balsa nose blocks or foam while honing my sculpting skills.
Paper cones will also mean I can keep it light.
I have a "Thing" for paper cones, as I use enjoy using them on the TLP Kits.

I owe you one!

Dave

Thanks to everybody for the responses, and for not telling me "Go back to school and learn Trigonometry".

rocketguy101 · Mar 1, 2016

TopRamen said:
The base is actually the slightest bit small, as it fits into the BT-55, but that's fine, as I can enlarge them 1% or just add a millimeter or two as I cut them out.

Yeah, for some reason the CAD program formed this gap...if you make a glue tab that fits inside, you can widen the bottom to fit correctly...I intended to put this image on that PDF, got excited, and posted it too soon :eyeroll: sorry for that...glad they work

TopRamen · Mar 1, 2016

rocketguy101 said:
Yeah, for some reason the CAD program formed this gap...if you make a glue tab that fits inside, you can widen the bottom to fit correctly...I intended to put this image on that PDF, got excited, and posted it too soon :eyeroll: sorry for that...glad they work

No worries, they are better than I hoped for.
I found a new "Hot Water Method" for shaping the cones too.
I use 110# Cardstock for cones.
I am sick with a fever, so after I cut out the first one, rather than expend my strength going to get some hot water to hold it over, I simply stuck it to my forehead for ten seconds to soften it. Worked perfect.

Oblique/(Offset) Paper Cones?

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