Quantcast

Most Kick in a tube?

The Rocketry Forum

Help Support The Rocketry Forum:

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
Alright, this question may be dumb to extents...but Im lost.
Im working on making a new scratch build..somewhat heavy..simmed about 9 oz.
So im trying to find the most economical way to launch it..and assure its recovery.
I.E.- I wanna keep it really low flying..but It has to has enough punch to get off a 3 ft rod with enough speed.
So my question to the wise RTF community is...

Which engine(s) Give enough punch for this..I've tried just about everything on Space cad but i Just can't figure it out.
Im Also looking to try to use A-C's if possible, and I'm no stranger to clusters either.

If you need more info ask..or IM me on AIM
Thanks!

-matt
 

DJ Delorie

Well-Known Member
Joined
Apr 2, 2004
Messages
221
Reaction score
1
In general, small letters with big numbers (Think A10, not C2) give you an initial "punch" off the pad, without boosting the rocket to higher altitudes.

For a 5x margin, a 9oz rocket wants at least a "12" (A D12, three B4's, etc). If you've simmed the model, just sim it with various engines until you find one you like ;-)
 

powderburner

Well-Known Member
Joined
Jan 18, 2009
Messages
7,356
Reaction score
4
If you try to double-up (or even a cluster of three or four) the little A10 13mm motors in a big/heavy/slow design, you can end up with a thrust profile that peaks and dies while the rocket is still on the launch rod. Not good. Run your sims carefully.

If you design for 18mm MMTs you will have the future option of using whatever impulse you need for a given situation. You may want to fly at a big field sometime and it could be good to be able to stick in three C motors.

Also, if the motors are closely clustered, don't overlook the option of flying an A/B combo (or a B/C, etc). You will have to plan carefully to account for burn time as well as delay time, but you can still get a combo cluster to work.
 

DJ Delorie

Well-Known Member
Joined
Apr 2, 2004
Messages
221
Reaction score
1
If you had four 13mms, you could do two A3's and two A10's.

What size BT *are* you working with?
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
BT size is 2"....
so i can cram just about anything and everything in there....unfornatuley the bt is made of incredibly dense 1mm plastic which makes just this 2ft long tube about 4oz. :eek:

my only other problem here is finding a nose cone with a 2" diameter that is 14in long or slightly longer for realtively cheap..
(im not kidding when i say cheap...I mean like under 10 bucks)
that doesn't weigh more than about 2.5-3 oz.

I've posted a pic of the design and a Space Cad blue print which show CG and CP (CP has a small dot in a circle-CG is checkered)
Any comments or anything on this are welcome and greatly appreciated.

-Thnx
_matt

....- I'm pretty sure I got the idea for this from the Space Cad Library I just tweaked it a bit..and its to no comparable scale.
 

Rocketjunkie

Addicted to APCP
Joined
Jan 19, 2009
Messages
4,121
Reaction score
348
I recommend a 24 mm mount and a C11-3. When conditions permit higher flights, there are composite 24 mm motors through G.
 

mge55389

Well-Known Member
Joined
Aug 9, 2009
Messages
212
Reaction score
1
It might be difficult to find a commerical nosecone that long and still weighs about 3 ounces or less. Plastic cones that size might be 10oz. +
Check out the issue of Sport Rocketry featuring the " Paper V-2" on the cover. I think it was the May- June 2004 issue. I read the article on the flight to the TARC Finals. In this article someone made a 4" dia.( or was it larger?) V-2 that was under 3.3 pounds. I don't have my copy handy, but I believe the nosecone was made out of card stock/ tag board, including a shoulder to go inside the body tube. There was also instructions on making a loop to attach the shock cord to. There was also some foamboard used in the rocket's construction, but I don't remember exactly what. It might have been the centering rings.

Good luck,
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
alright...I really spent some time looking at this because the whole planning thing was going WAY to easy, I knew something had to be just not right.
So i figred what it is.


So far i have two B-14's in there which give plenty kick.
problem is.... the Cp and Cg are incredibly close to the center point of the roc. which could make this a little wind cocky?
And i can't really add anymore weight or ill have to start adding more engines..which inturn will eventually mean higher altitudes.....any ideas?..or is this even a problem?

-matt
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
a better blue print pic....the other was slightly small?
 

BlueNinja

Well-Known Member
Joined
Jan 18, 2009
Messages
2,690
Reaction score
1
B14s are OOP now. If you cna get some, however, wowee!


I know apogee used to make a pretty fast motor, the B7, but haven't heard anything for a while about those.
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
what about balsa?
I've never done a NC this big would balsa give a closer number to 3oz?
Im no good at making my own NC's they all turn out lopsided

-matt
 

mge55389

Well-Known Member
Joined
Aug 9, 2009
Messages
212
Reaction score
1
A good source of premade balsa nosecones is Balsa Maching Service ( BMS).
www.balsamaching.com
The longest one that is a "stock part" is BNC80K which is for a BT 80 tube. It's O.D. is 2.6 ", I.D. is 2.588"
Length is 8.25" Price is $8.95 + shipping
I happen to have one of these cones. I weighed it on my scale. It weighs 1.6 oz.
The one you designed is about 6 inches longer and a little narrower, so you should be able to make one around 3 oz.

I'm not sure how much a balsa block costs, but you could shape your own nosecone using a drill press or a wood lathe. This forum is a great place to find other methods as well.
Bill at BMS also does custom nosecones for a fee. The best way to find out the actual cost would be to call or e-mail him for an estimate.
 

DynaSoar

Well-Known Member
Joined
Mar 15, 2004
Messages
3,007
Reaction score
0
Originally posted by moocrew
Alright, this question may be dumb to extents...but Im lost.
Im working on making a new scratch build..somewhat heavy..simmed about 9 oz.
So im trying to find the most economical way to launch it..and assure its recovery.
I.E.- I wanna keep it really low flying..but It has to has enough punch to get off a 3 ft rod with enough speed.
So my question to the wise RTF community is...

Which engine(s) Give enough punch for this..I've tried just about everything on Space cad but i Just can't figure it out.
Im Also looking to try to use A-C's if possible, and I'm no stranger to clusters either.

If you need more info ask..or IM me on AIM
Thanks!

-matt
A C5-3 would just about do it, but they're OOP. A C6 won't.

I think you'd be happiest with a 24mm mount for Estes 'E' size (3.75") motors. You can use a 1" spacer for C11 and D12 motors. For birds this weight I almost always fly an E9 after testing on a D12. If by "getting it back" you're concerned about drift, try an X-form chute.
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
Last night I email BMS about a custom NC so hopefully I'll know a little more about that by the end of the day.

And as far as power goes on this thing. Im thinking D's are probably a good way to go..atleast then weight won't AS big of a problem.
DynaSoar- I know I've heard of X-Form
But what exactly is so great about them...obvoulsy in this case the drifting...but can you add anything?

Thanks again for all of your help!
-Matt
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
Also...is there a list anywhere of motors that are STILL IN production...this OOP stuff kicks my butt everytime...

thnx
-matt
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
what about C-11's?
Still in production right?
But I don't have a WRASP file or Space cad file for it. :(
 

DynaSoar

Well-Known Member
Joined
Mar 15, 2004
Messages
3,007
Reaction score
0
Originally posted by moocrew
DynaSoar- I know I've heard of X-Form
But what exactly is so great about them...obvoulsy in this case the drifting...but can you add anything?
Way less drift than a hex or octagon the same size, and still nearly 90% the surface area so almost as "slow". The reason being a full chute has an airfoil shape and will actually generate some lift as it drifts. Thus, it'll fall slower with more wind and drift more than just windspeed carrying it along.

I find them *lots* easier to fold and pack, and I just think that probably makes them unpack and deploy more easily. They don't oscillate as much (do the pendulum bit) because they spill more with less tip, and that makes them less prone to spinning and thus tangling, but more spillage means it'll fall faster if it does tip.

If I didn't tend to prepack 8 ot 12 birds at a time the night before a launch, I'd just keep me half a dozen of these on clips and swap them onto all my rockets as I prepped them. If it called for a 12" I'd go one size up to a 15" X-form. My upscale Rock-A-Chute weighs 11 oz. with a spent E9 in it, and the fins are swept WAY back, meaning it always lands on a fin-tip. It's never flown with anything other than a 12" X-form. If I flew it where it might land on pavement I'd go up to a 15". The time its kevlar shock cord burned through, the nose and chute came loose and I was sure it was going to sail away with my custom turned, authentic Sandman autographed nose cone. It didn't.
 

moocrew

Well-Known Member
Joined
Apr 8, 2004
Messages
275
Reaction score
0
Alright, I got an email back from BMS they don't do "complete" custom work. you pretty much get to chose from some other sizes..and the one that is long enough isn't even wide enough and is already $30+ ...thats a bit much for me...
DS- you said sandman does cones?
I might have to see what he says.
anyone know where I can get an updated Space Cad or WRASP file with a C-11 in it?

-matt
 

DynaSoar

Well-Known Member
Joined
Mar 15, 2004
Messages
3,007
Reaction score
0
Originally posted by moocrew
Alright, I got an email back from BMS they don't do "complete" custom work. you pretty much get to chose from some other sizes..and the one that is long enough isn't even wide enough and is already $30+ ...thats a bit much for me...
DS- you said sandman does cones?
I might have to see what he says.
Yes, he does. Very well. Not just "standard" sizes or shapes either. He did the 2.2" upscale in this picture for me, and is doing a 3" version now.

Do a simple line drawing in Paint. It doesn't have to be a great drawing, but does have to have all the exact dimensions. He can give you an estmate for different woods based on that. Heck, you've got the shape from your sim. Just give OD, ID, shoulder length and nose length with it. If you could blow it up to exact full size to use as a template, that'd probably be even better.
 
Top