7.5" 1/2 Scale Phoenix L2 cert project

Perhaps a little premature but I wanted to get my plans out here for scrutiny. I'm still constructing my L1 4" Madcow Phoenix which I plan to launch in March. Like many the rocket bug has bitten me good and as I used to have the Estes Phoenix and now a 1.6" Launch Pad Phoenix I'm going to keep the theme going for my L2 bird.

Outline-
1/2 Scale AIM-54C Phoenix Missle, 7.5" dia, 6.5' long, 23lbs dry, 75mm motor
Dual Deploy, with redundant electronics designed to meet L3 requirements
J-k-L Motors for L2 flights
TTW fins with fin pockets on MM
M Motor capable for potential L3 certification
Telemetry bay in nose for later use

First question of many to come, think I can use 1/4' aircraft ply for the fins w/o any glass? G10 is cool but I want some thickness to sand in an airfoil. I'm sure I'd be fine for mild J-K-L motors but the M3500 has crazy acceleration and hits Mach 1 (potentially).
Another, how come open rocket has all my deploy speeds like 60 ft/sec when the motor is set for apogee eject?

Here's my .rkt file (if I attached it right) and a screen cap of what it looks like so far. I appreciate any input, suggestions, criticisms or questions. It's my first time designing a rocket of this scale and my first attempt at open rocket. Thanks all!

View attachment My Half Scale Phoenix w 75mm.rkt



And here's a fun video I shot with my nephews last weekend.

https://youtu.be/RzZdWEQ4Z-c

-Scott
OKC, OK

1) 1/4" Aircraft Ply= yes, I used 1/8" with two layers each side for my L2 rocket, and all the Binder Design Kits use Aircraft Plywood (the real stuff like Aircraft Spruce sells, 12 ply). For M impulse motors I would glass them.

2) For L3 you will have to build a new rocket or document this one heavily including lots of photos, the L3CC or TAP still may not allow it, mainly because before you can even apply for L3 you need to be L2 (I already asked this question, since my original plan was to build one rocket for L2 and L3, I'm building something different for L3).

3) Contact your local L3CC and or TAP and see what they have to say, with prior planning on the build of your L2 they may allow the rocket with proper documentation to be used for the L3 cert. I actually can see very little reason that you wouldn't be allowed to fly it for L3 as long as its built and documented according to L3 requirements.

4) Open rocket has your deploy speeds set that way because that is the speed at which the rocket is descending under Drogue, OR doesn't tell you your drogue descent rate you have to figure it out based on the velocity at the time the main opens.

My 5.5" Phoenix could fly on M's all day long, so a 7.5" (built right) should be a breeze.

Consider fiberglass honeycomb material for the fins. You can make leading edges out of hardwood and you will save a considerable amount of weight. There was a special or clearance page but I cant find it right now. https://www.acpsales.com/Fiberglass-2-Ply-Honeycomb.html

dixontj93060 said:

My 5.5" Phoenix could fly on M's all day long, so a 7.5" (built right) should be a breeze.

Click to expand...

Indeed! Excellent build thread! Read the whole thing and picked up several good ideas. Hope to make mine every bit as nice. I'm surprised by the weight difference between the sim (14) and actual (19). 5lbs is 35% more tham protected, lots of which I guess is the ton of glass and epoxy you used?

Brent said:

Consider fiberglass honeycomb material for the fins. You can make leading edges out of hardwood and you will save a considerable amount of weight. There was a special or clearance page but I cant find it right now. https://www.acpsales.com/Fiberglass-2-Ply-Honeycomb.html

Click to expand...

Great idea. I'd like to avoid any fiberglass work if possible but I'll investigate that.

rharshberger said:

1) 1/4" Aircraft Ply= yes, I used 1/8" with two layers each side for my L2 rocket, and all the Binder Design Kits use Aircraft Plywood (the real stuff like Aircraft Spruce sells, 12 ply). For M impulse motors I would glass them.

2) For L3 you will have to build a new rocket or document this one heavily including lots of photos, the L3CC or TAP still may not allow it, mainly because before you can even apply for L3 you need to be L2 (I already asked this question, since my original plan was to build one rocket for L2 and L3, I'm building something different for L3).

3) Contact your local L3CC and or TAP and see what they have to say, with prior planning on the build of your L2 they may allow the rocket with proper documentation to be used for the L3 cert. I actually can see very little reason that you wouldn't be allowed to fly it for L3 as long as its built and documented according to L3 requirements.

4) Open rocket has your deploy speeds set that way because that is the speed at which the rocket is descending under Drogue, OR doesn't tell you your drogue descent rate you have to figure it out based on the velocity at the time the main opens.

Click to expand...

Thanks Rich, good info as usual! I've already reached out to a L3CC member to find out.

sed6 said:

Indeed! Excellent build thread! Read the whole thing and picked up several good ideas. Hope to make mine every bit as nice. I'm surprised by the weight difference between the sim (14) and actual (19). 5lbs is 35% more tham protected, lots of which I guess is the ton of glass and epoxy you used.

Click to expand...

Yeah, wouldn't get too much into the original Rocksim, they are true approximations.

dixontj93060 said:

Yeah, wouldn't get too much into the original Rocksim, they are true approximations.

Click to expand...

Ugh. My design was dictated by the desire to stuff the biggest 75mm M-motor (~42") I could find into it with the hopes of cracking mach 1, if for no other reason than to tell friends it can/did/does. If my rocket turns out much heavier than the sim I might be SOL.

Check out my DD bay, it's short, so I could fit an M in the back. I planned on a mere 5" coupler length and just 8" of length for my electronics bay. I could change all that if needed tho.

Perhaps I overlooked a 75mm M-motor option? Something shorter or stronger than an M3500?
I'm going to have to build it light...

The Estes Phoenic was one of my favorite rockets!!! I think you have inspired me to build a 7.5 version for myself. How much nose weight did you use? I think all the nose weight is the only downside to Phoenix.

amarillo_rocket said:

The Estes Phoenic was one of my favorite rockets!!! I think you have inspired me to build a 7.5 version for myself. How much nose weight did you use? I think all the nose weight is the only downside to Phoenix.

Click to expand...

72oz for a giant M motor, about 1/2 that for a more moderate J-K motor. That said I've begun researching ways to get the weight down, on the fins in particular. Every ounce I save on them is an ounce I can take out of the nose. I do plan to make my nose weight removable, at least some of it.

Brent said:

Consider fiberglass honeycomb material for the fins. You can make leading edges out of hardwood and you will save a considerable amount of weight. There was a special or clearance page but I cant find it right now. https://www.acpsales.com/Fiberglass-2-Ply-Honeycomb.html

Click to expand...

Great link and great idea! However that lead to days and days of reading up on all sorts of fiberglass honeycomb, Kevlar honeycomb (aramid), CF and FG, and of course that lead to lots of searching here and then YouTube and then John Coker's site (that took days to look through) Didn't think I wanted to go the route of fiberglass but the more I read the more I think it can help.

Question, with the honeycomb materials, fiberglass or aramid is a skin necessary before I lay glass and vacuum bag it? I'd think so, something like 1/32 balsa skin would probably do the trick, just something to keep the glass cloth from getting sucked into the honeycombs under vacuum. But then why not go with a thin G10 and thick balsa skins and skip the hardwood edge I ask myself? I think my priority has to be weight. What about a solid poly foam, I bet I could skip skinning that.

I bit the bullet and ordered a bunch of epoxies and fiberglass supplies to practice vacuum bagging. Going to throw a layer or two on my 4" Phoenix fins, plus practice my filets both internal and external, and I'm going to foam the fin can, just for practice. I got expanding foam and some silica and some chopped glass and a bunch of other building supplies coming soon.

I also started using open rocket, thanks for idea John! Rocksim is great and all but the license fee, I'm going to extend it another 30 days and see if I find more value in it. I do like that I can see things like thrust and acceleration frame by frame in the animation. Does Open Rocket support that?

Here's my latest open rocket file.
View attachment My Half Scale Phoenix w 75mm.ork

I built a 5.5" blue tube rocket with a 98mm mount using the honey comb material and used leading edge stock for the edges. I didn't vacuum bag as I wasn't set up to do it at that time. I used 2 48" 5.5" blue tube sections for the airframe. It was extremely light empty. I flew the heck out of it and eventually gave it to another club member. If Dave ever does another run of the 11.5" Mercury capsules I plan on using the honeycomb material for the fins on a Redstone. There was a full scale Phoenix built years ago that flew in Amarillo at LDRS that used the stuff. I believe it is in a museum in Oklahoma now.

Another option for the fins: Balsa that is sandwiched with fiberglass or carbon fiber.

Especially end grain balsa panels.