L2 scratch idea...

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KermieD

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I was just chucking around some stuff on Rocksim looking for a fun idea for a scratchbuilt rocket for my L2. I ended up running into a few limitations of RSim doing this (it wouldn't let me make the root edge of the fins any longer than this :( )

Anyway, this is the roughest of rough drafts. It's quite stable even without any recovery or electronics in it. I've been thinking of putting pods on the ends of the fins as well as either a) some sort of cockpit towards the back or b) using the 4" Argosy nosecone. Right now, it has 36" body tubes from Binder Design and the Binder avionics bay as well. This may change to 48" PML phenolic tubes and a homemade alt bay. Either way the tubes will be glassed.

Thoughts? Suggestions?
 
Not having attained L1, my input may be useless... ;)

The 4" Argosy NC would look kewl on that bird Kermie. Is it a stability issue or asthetics you're looking for?
 
That is one cool looking rocket...and I guess you get another vote for the Argosy cone. :D

I must be missing something with your comment about Rsim limitations. I have build large fins in Rsim and just put fins with a 30 inch root on a 3" tube. I have 6.05 but am pretty sure even the older versions would let you do this. ?????

Also, are you sure its very stable with a L2 motor installed? Just curious.

Either way, nice design!
 
The design looks pretty cool. FYI, you can get the nosecone, which looks very similar to the Black Brandt II I just built, from Scotglas. He does a very nice job with them. I've started filling mine with 2 part foam and this is what I'd recommend with Scotglas's as well. It goes a long way toward saving the nosecone if you take a core sample.

I've only built two kits in my rocketry career. 98% of my flyers are scratch from non-conventional to conventional tubing so let me know if you need any input. I'll share with you some of the lessons of what not to do as well.

Shane

https://www.scotglas.com/components2.htm
 
I had been planning on having that forward line from the fins slope all the way to the BT, but Rsim won't let me stretch it that far. No clue why. I'm still using Rsim 5 tho.

As it sits, this will be plenty stable. I haven't put a motor in it yet, but neither did I put the alt bay and chute (not to mention the 8 oz. TransBeep). As it sits with none of this in there, the CG is at least 3 or 4 calibers forward of the CP. I figure everything else, once it is in, will be a wash at worst, leaving the margin of stability pretty much as it is (unless I go with an L or something silly like that).
 
Let me offer a couple of observations. When you step up to motors lin the J,K,L range, you start to have all kinds of challenges. Fins like are on that rocket will flex wildly under the significant speed of J and up motors. In most cases a little flutter is disasterous. For an L2 Attempt, I'd stick to something really easy and proven. while scratch building one to your own specs is very cool. Just remember, stuffing a J350 or J330 pro38 up it's rear end and mashing the button gives whatever is on the other end a serious kick in the butt.

For example a friend of mind flew a 4" Armegeddon on a K560GG. Somewhat similar fin design and it was 3,2,1 sssssssshh, DISASSEMBLE. Little bitty pieces parts came floating down. Not fun.

Something to think about. Thin "root" or "tip" and long, are not good unless you do them really thick and glass them.

alan
 
I was thinking 1/4" to 3/8" ply and tip-to-tip glassing was part of the plan. My brother will probably be machining me a fin jig which will assure that the fins are both perpendicular to the BT and straight along the length of the root. With everything glassed, it will probably weigh in at least at 10 lbs or so, so I don't anticipate speed on a J to be a deciding factor (but lord knows it wouldn't be the first time I was wrong). While I would love to go with a K560, I'll probably be much closer to the J350 range, depending on where the sims work out when I'm done.
 
Originally posted by aadamson
flew a 4" Armegeddon on a K560GG. Somewhat similar fin design and it was 3,2,1 sssssssshh, DISASSEMBLE. Little bitty pieces parts came floating down.
4" rocket on a K? I bet that thing hit Mach or came close. Any rocket reaching mach but not busting through is going to come down in pieces.

Originally posted by gerbs4me
Heres a L2 idea. This bad Boy has a K560 in it.
Beautiful pic Gerbs...
 
Merry Christmas to all.

I have to say that Alan has a great point about the fins, but I also have to encourage you to be creative. There is absolutely nothing wrong with scratch building if you have very carefully simed the project and have a mentor or two to bounce things off of. Build it for the largest motor and then you have the option to back off, but you still have the option of pushing the envelope. For the L2 attempt stick to the KISS method and pop a J in it. After you've succeeded drop another motor in it an test your ability.

Secondly, I just flew a four inch Black Brandt II on a K670. I have to quote now - "you can never overbuild, but you can under power."

BTW, scratch offers tons of challenge and that's why I pursue it with a passion. It hasn't failed me yet.

Shane
 
It's not that big of a deal. I fly my PML A4 on K670GG's and it flies great. Goes about Mach .8 up to 6100ft AGL. Nice flights.

Dual deploy with an RDAS in it. Puts out a Rocketman Drouge at apogee and a R9 at 600ft. So far on five flights it has landed anywhere from 100ft form the pad to 300 ft. Not bad...

Geoff


Originally posted by PGerringer

4" rocket on a K? I bet that thing hit Mach or came close. Any rocket reaching mach but not busting through is going to come down in pieces.


Beautiful pic Gerbs...
 
Kermie, looks cool. You should be able to put longewr fin roots with rocksim. All you have to do is type the number manually, or if using the graph, change the scale.
 
Kerm,

I'm with Alan on this one. Watch out for fin flutter. My L2 was a simple 4" 3FNC weighing 9lbs w/out motor, but it's still a great flyer. I've noticed that the highly stylized rockets get a lot of attention, but post-flight... the good flyers get noticed as well. I certified on a KBA K400. Since then, I've flown it on a Kosdon J280, Kosdon K350 twice, AMW K670, AMW K950 and will next put it up on an uncertified AMW K1200. It's cardboard w/ two wraps of 3.3oz glass, glass NC, G10 fins and G10 centering rings...and most importantly an aluminum back plate.

Regards,

John
 
What case and prpellant is the K1200?


Originally posted by Herc
Kerm,

I'm with Alan on this one. Watch out for fin flutter. My L2 was a simple 4" 3FNC weighing 9lbs w/out motor, but it's still a great flyer. I've noticed that the highly stylized rockets get a lot of attention, but post-flight... the good flyers get noticed as well. I certified on a KBA K400. Since then, I've flown it on a Kosdon J280, Kosdon K350 twice, AMW K670, AMW K950 and will next put it up on an uncertified AMW K1200. It's cardboard w/ two wraps of 3.3oz glass, glass NC, G10 fins and G10 centering rings...and most importantly an aluminum back plate.

Regards,

John
 
According to Ken it's a modified Super Tiger formulation. It uses the 54-1750 case.
 
I can honestly appreciate the KISS principle and the potential fin flutter issues. However, I strongly suspect this rocket will come in at least at 9 or 10 lbs. dry. I simmed the design at 10 lbs on a K550 and top speed was only 720 ft/sec. My BBX topped that with 1/8 in fins and 1.5 oz glass. This one will have 1/4" fins with 6 oz. glass.

I'm just looking to do something a little different this time and a 3 or 4FNC rocket doesn't appeal to me for that purpose.
 
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