Hi All,
As I’m working through my L3 planning, I’m also scratch-building a 3” DD rocket with a 38mm motor tube that will be a “frequent flyer” for everything from G-J. I’m trying to make it light enough to fly under a Class 1 waiver with a G or small H, but robust enough to handle high transonic/supersonic with a J. I’ve attached my OpenRocket file with my current thinking FYI.
Nothing too cosmic about the design, but making it both light and robust enough for supersonic flight is the main challenge.
I haven't completely decided, but I’m pretty sure I’m going to go with canvas phenolic (MAC Performance) for my airframe and fins. That will make it light enough to fly as a class 1 and strong enough for supersonic. I’ve heard great things about their kits, and that if you custom order stuff they will make it just like one of their kits. I’ll probably order it right after Christmas (once I decide on the final design).
If you look at the .ork file, you will notice that it gets less than 1 cal. stability margin with heavier I and J motors, so I’m adding provisions for removable weight in the nose. Depending on how much I need, that may be as simple as adding a quick link with some large flat washers (I’ve found a size where 2 washers = 25 grams, so easy to adjust) to the nosecone eyebolt -- okay up to about 150 grams. If not, I’ll probably “roll my own” version of a removable nose weight system – thinking a threaded rod with swappable weight cylinders made from epoxy and lead. Or, I may just go really modular with two different nose cones of different weights. Hmm.
Please feel free to kibitz on the design -- prime directive is to make the thing work the way I want it to. Any and all suggestions are welcome! I'm pretty close to happy with it, but not entirely.
<brace for incoming>
Bill
As I’m working through my L3 planning, I’m also scratch-building a 3” DD rocket with a 38mm motor tube that will be a “frequent flyer” for everything from G-J. I’m trying to make it light enough to fly under a Class 1 waiver with a G or small H, but robust enough to handle high transonic/supersonic with a J. I’ve attached my OpenRocket file with my current thinking FYI.
Nothing too cosmic about the design, but making it both light and robust enough for supersonic flight is the main challenge.
I haven't completely decided, but I’m pretty sure I’m going to go with canvas phenolic (MAC Performance) for my airframe and fins. That will make it light enough to fly as a class 1 and strong enough for supersonic. I’ve heard great things about their kits, and that if you custom order stuff they will make it just like one of their kits. I’ll probably order it right after Christmas (once I decide on the final design).
If you look at the .ork file, you will notice that it gets less than 1 cal. stability margin with heavier I and J motors, so I’m adding provisions for removable weight in the nose. Depending on how much I need, that may be as simple as adding a quick link with some large flat washers (I’ve found a size where 2 washers = 25 grams, so easy to adjust) to the nosecone eyebolt -- okay up to about 150 grams. If not, I’ll probably “roll my own” version of a removable nose weight system – thinking a threaded rod with swappable weight cylinders made from epoxy and lead. Or, I may just go really modular with two different nose cones of different weights. Hmm.
Please feel free to kibitz on the design -- prime directive is to make the thing work the way I want it to. Any and all suggestions are welcome! I'm pretty close to happy with it, but not entirely.
<brace for incoming>
Bill
