Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > The Doctor is In! > Ask the Doctor
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #11  
Old 05-13-2020, 01:14 PM
RobVG RobVG is offline
Craftsman
 
Join Date: Apr 2020
Location: Seattle
Posts: 101
Default Added the front fins

They reduced Cal just a bit. Adding an additional 0.1 oz brought it just above 1.0

Adding more weight increase it very slowly.
Reply With Quote
  #12  
Old 05-13-2020, 01:26 PM
BEC's Avatar
BEC BEC is offline
Master Modeler
 
Join Date: Feb 2009
Location: Auburn, Washington
Posts: 3,022
Default

100 feet on a no-wind day. That's dicey even with a 3-second delay getting a 'chute out and open before it hits the ground. D12 would be a minimum for safe flight. There also 3 second delay. I would not try a Q-Jet D16-4 until I saw it fly on an Estes D12-3.

Thinking of it as a dual egg lofter makes the numbers sound more plausible to me.

Now that Sixty Acres is open again (I had the north field all to myself on Monday from 11:30 to about 3) you could fly it over there on an E30.
__________________
Bernard Cawley
NAR 89040 L1 - Life Member
SAM 0061
AMA 42160
KG7AIE
Reply With Quote
  #13  
Old 05-13-2020, 02:04 PM
neil_w's Avatar
neil_w neil_w is offline
Mr. Cut-by-hand
 
Join Date: Nov 2015
Location: Northern New Jersey
Posts: 426
Default

Quote:
Originally Posted by RobVG
Haven't yet figured out how to add the forwad fin set . To make it look right they need to be placed on the nose cone.

If you're talking about the forward fins on the current iteration of Starship, be forewarned they will pull the CP forward and you'll need even *more* noseweight.

The way to add them in current version of OR is:
1) Split the nose cone into a cone and a transition, with the break point at the leading edge of the fins.
2) Insert a zero-length body tube between them
3) Mount the nose cone fins to that body tube.
Reply With Quote
  #14  
Old 05-14-2020, 02:29 PM
RobVG RobVG is offline
Craftsman
 
Join Date: Apr 2020
Location: Seattle
Posts: 101
Default

Quote:
Originally Posted by neil_w

The way to add them in current version of OR is:
1) Split the nose cone into a cone and a transition, with the break point at the leading edge of the fins.
2) Insert a zero-length body tube between them
3) Mount the nose cone fins to that body tube.


I was able to add them another way Neil. Clicking on the body tube allowed me to add a second set of free form fins. They ended up on the rear of the rocket and I was able to reposition them on the nose cone. I'll try your method to gain some more experience with OR.

Thanks!
Reply With Quote
  #15  
Old 05-14-2020, 02:50 PM
LeeR's Avatar
LeeR LeeR is offline
Retired with Way Too Many Kits
 
Join Date: Jun 2007
Location: Colorado
Posts: 2,729
Default

Quote:
Originally Posted by RobVG

Haven't yet figured out how to add the forwad fin set . To make it look right they need to be placed on the nose cone.


A good way to add fins to the nose cone, assuming your concern is due to them being mounted on a plastic nose cone, is to first cut fin slots. You want to make them thru-wall so they are well anchored. Have the tabs meet in the center of cone, where they can be glued together. I use a bit of epoxy at the fin-nose cone joint, if filling is needed, and follow up with putty if any additional fill or smoothing is needed.
__________________
Lee Reep
NAR 55948

Projects: Semroc Saturn 1B, Super X-Ray
In the Paint Shop: Farside-X, Tiger Shark, Super Goblin
Last Completed: Semroc Squire
Reply With Quote
  #16  
Old 05-14-2020, 03:11 PM
RobVG RobVG is offline
Craftsman
 
Join Date: Apr 2020
Location: Seattle
Posts: 101
Default

Thanks Lee. Slots sound like a good idea.
Don't think I'll be able to get the tabs to meet. It'd be hard to add the weight.

Leaving shortly to get balsa wood. No paint until it flies.

When the time comes, it'll be launched at dawn. Don't want anyone around.
Reply With Quote
  #17  
Old 05-15-2020, 12:38 PM
RobVG RobVG is offline
Craftsman
 
Join Date: Apr 2020
Location: Seattle
Posts: 101
Default

They didn't have balsa. Gonna give basswood a try.
Reply With Quote
  #18  
Old 05-15-2020, 02:19 PM
RobVG RobVG is offline
Craftsman
 
Join Date: Apr 2020
Location: Seattle
Posts: 101
Default

Well dang lol. just opened OR again and the weight "did" include engines. 10.7 oz.
Reply With Quote
  #19  
Old 05-18-2020, 01:49 PM
luke strawwalker's Avatar
luke strawwalker luke strawwalker is offline
BAR
 
Join Date: Dec 2007
Location: Needville and Shiner, TX
Posts: 5,986
Default

If nose fins are messing up your CG/CP relationship and requiring too much noseweight, you could always make them PIVOTING fins, which if done right have NO adverse affects on the CG/CP relationship and can minimize the amount of nose weight required.

Basically, only the area of the fin ahead of the pivot has to be accounted for in the stability calculations... IOW, if the pivot point is at the 1/4 chord line, only the part of the fins IN FRONT of the pivot "axle" point contributes to instability... for Rocksim/Open Rocket simulations, you basically add "fixed" fins the size and shape of the area of the fin AHEAD of the fin pivot point in the simulation, to determine what the aerodynamic effects on the CG/CP relationship are and thus amount of noseweight required...


Later! OL J R : )
__________________
The X-87B Cruise Basselope-- THE Ultimate Weapon in the arsenal of Homeland Security and only $52 million per round!
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 04:58 AM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe 1998-2021