Quantcast

Rack Rockets

The Rocketry Forum

Help Support The Rocketry Forum:

ronhill

Well-Known Member
Joined
Jan 20, 2009
Messages
123
Reaction score
0
Thought I start a rack rocket thread and post a photo of my latest, Rack 4. Rokitflite and I accidentally hijacked a thread some time back originally dealing with tube-finned rockets.

This photo does not show the engines installed, but imagine the booster hanging in the middle of the fin booms and taped (the usual method) to the upper stage engine. This is a BT-60 design and uses a combination of D12-0 and D12-7 engines. It flew well at the Quark launch last Sunday.

The Rack 4 is not an optimum design, but I recycled the body tube from a previous conventional rocket with warped fins--too much water in the FnF on old dry plywood. I simply cut and ground off the old warped fins and attached the fin booms.

I’m not sure of the definition of a rack rocket, but this definition will do. It’s a multistage rocket with only one set of fins. Those fins are extended aft on booms to ensure stability for all stages. The booster(s) are CHAD staged and simply drop off (without fins) through the middle of the fin booms. The obvious advantage is decreased weight and drag during the booster phase. But that’s compensated for by the weight and drag of the booms. Further, the upper stage carries everything (except the booster engine) the entire flight. Another positive factor is that the fins can be relatively small because of forward CG and aft CP.

In any case, it stages high and smoothly, and the upper stage consistently goes almost out of sight—I always use a streamer. The rack rocket idea came from a 2002 TRA paper entitled, The Rack Rocket Concept, a Quest for High Altitude, by Ken Good. You can get it from his page at:

members.tripod.com/Tripoli_Rocketry_PGH/kjgboard.html

If anyone is interested, I can post photos of the since-departed Rack 1 and Rack 2 rockets or refer you to previous posts.

Is anyone else making rack rockets?
 

Fore Check

Well-Known Member
Joined
Sep 24, 2010
Messages
4,243
Reaction score
7
This is the first time I've heard the term "rack rocket."

In simple terms, it looks like a CHAD staged rocket with the fins mounted aft of the sustainer engine on dowels or "booms."

There are several plans out there with similar fin configurations. One that comes to mind is an old Estes DOM plan for the "stiltfin." This one is a minimum diameter 18mm rocket, and I know it works CHAD staged.

http://www.dars.org/jimz/eirp/eirp_48.tif
 

ronhill

Well-Known Member
Joined
Jan 20, 2009
Messages
123
Reaction score
0
Originally posted by Fore Check
This is the first time I've heard the term "rack rocket."

In simple terms, it looks like a CHAD staged rocket with the fins mounted aft of the sustainer engine on dowels or "booms."

There are several plans out there with similar fin configurations. One that comes to mind is an old Estes DOM plan for the "stiltfin." This one is a minimum diameter 18mm rocket, and I know it works CHAD staged.

http://www.dars.org/jimz/eirp/eirp_48.tif
It is indeed simply a CHAD staged rocket with aft fins. Thanks for the reference for the Stiltfin. I'd never seen it before. Rack 1 was something similar, and I've included a photo--very draggy, but it flew well. In the photo it has a 3-engine cluster and a single engine upper stage.

Your note brought back memories. I had forgotten the Estes DOM.

The term "rack" wasn't mine. Take a look at the reference I put in my original e-mail. I believe I recall the author had planned (or maybe even launched) a 7 stage rack rocket
 

ronhill

Well-Known Member
Joined
Jan 20, 2009
Messages
123
Reaction score
0
Thought I had done a search of TRF for racks, but I guess not. That was a good discussion in the previous threads. Thanks.

I wish I could find the Tripoli Pittsburgh rack rocket article that's referenced in the earlier thread. I looked but it must be buried. I'll spend more time later looking for it.

I'd like to see a photo of your 4 X D12 rack if you have one.

Attached is a photo of Rack 2 (shown only in a single stage configuration). It would handle 3 stages (D12s), but the winds never agreed so it never got above 2 stages.

One thing a rack does--avoids having to watch and track down the lower stages.
 

ronhill

Well-Known Member
Joined
Jan 20, 2009
Messages
123
Reaction score
0
Actually that last photo of Rack 2 was in a two stage configuration. It has been a while since I looked at it. I believe the lower stage was an FSI D20.
 

rstaff3

Oddroc-eteer
Joined
Jan 18, 2009
Messages
11,716
Reaction score
8
I don't have any pics of mine. I couldn't find the rack rocket article on the Tripoli Pittsburg site after they rearranged it. However, I do have it saved locally. So, if you email or pm me your email addy, I'll send it to you. A few pics are missing but most are there.
 

rstaff3

Oddroc-eteer
Joined
Jan 18, 2009
Messages
11,716
Reaction score
8
Heh, looked back a the link in the original post and lo and behold its the same thing I have :eek: Sorry Ron, I shoul dhave followed the link originally!
 

ronhill

Well-Known Member
Joined
Jan 20, 2009
Messages
123
Reaction score
0
Dick,

It's not a problem. Thanks for going to the effort of bundling up all the files and sending them to me. It's quite a good article.

Ron
 

ronhill

Well-Known Member
Joined
Jan 20, 2009
Messages
123
Reaction score
0
Originally posted by marvSRG
I made a design for a rack rocket called Moon Dog IV based on the design in sport rocketry and my friend built it. The basic difference between my design and the SR one was that I changed the fins and added a D12 booster to it...we never saw it again. What a flight. Heres a link to it:

http://www.rocketrycarolina.org/mod...ame=gallery&file=index&include=view_photo.php
Marv

Fascinating design. It took me a bit of studying to see that the fins were extended on booms parallel to the body tube of first stage. I never thought about using a conventional booster for the first stage with a rack design for the remaining stages. It has a Nike Zeus appearance.

Not surprised you never saw it again. That's probably one of the cleanest 4-stage rockets you'll find.

Ron
 

marvSRG

Well-Known Member
Joined
Mar 23, 2011
Messages
900
Reaction score
0
Thanx for the comments. It was a sweet bird. The D12 booster did help out a lot in getting it going. Due to the small fin size, it had a bit of noseweight in it to counteract that, so the D really was benificial in getting it zipping in the air, and even with that good kick, it weathercocked a bit. But once it staged it was outta there. My guess was somewhere in the 4000' range. The sound of the last stage firing was incredibly delayed and faint.
 
Top