[NRV Rocketry] Suggestions for good L2/L3 Rockets?

Sun Jul 13 19:55:55 CDT 2014

Good comments.  It is always educational to see what other people are doing
and there is always something to learn.  I'll share just a little bit of my
experience and tailor the suggestions to our current flying field at
Kentland Farms.

I have thought several times of building two rockets of equal mass with
different body diameterts.  When you start to get into level 2 and 3
rockets, the diameter becomes more of a factor in the altitude than mass.
 Many east coast flyers have to deal with limited launch sites and waivers
so they tend to go 'big and slow'.  My L3 rocket was 7.5" diameter and
weighed in at 69 pounds on the pad.  I flew it on a 76mm Kosdon M??? and it
went around 3500 feet.  Make a 69 pound rocket in 4" airframe and your
altitude will be much higher.

My general recommendations for cert flights:
  L1 - 3-4" airframe
  L2 - 4-6" airframe
  L3 - 6-9" airframe

Yes, you can always add mass to try to reduce altitude, but this causes a
domino effect where more mass requires a larger parachute and a larger
parachute may require a larger air frame.  Many successful certifications
have been made with large diameter airframes and motor deployment only, but
I would always recommend dual deployment if possible.  I would suggest a
target altitude for Kentland farms of 3,000 to 5,00 feet.  We had some
great luck contributing to having 3 successful level 2 certification
flights last month.  I will always try to maximize the possibility of
getting the rocket back.

Hope that helps a little.

Bob

On Sat, Jul 12, 2014 at 9:35 PM, Thomas Weeks <tweeks-junk2 at theweeks.org>
wrote:

> Awesome awesome tips guys! Exactly what I (and others probably) were
> looking for. It will be a while for me thoug. I enjoy doing research,
> slowly build and solve design challenges, all while learning from othes
> like this, so I'm going to take it slow.
>
> Thos who have not been doing or hanging our with High Power folks very
> long might find this book a great resource for tips like the ones voiced in
> our thread:
> http://www.amazon.com/gp/aw/d/1412058104?pc_redir=1404837764&robot_redir=1
>
> I was just browsing through it the other night and saw a caption showing
> the ebay of our friend Chuck Neff's (from VAST) L3 flight in there. They
> were showing the pristine wiring of his altimeters and ebay systems is his
> L3 flight at LDRS (iirc). That was awesome!
>
> Anyway, thanks for all the great tips. I think while I am going to "keep
> it simple", I'm not going to hold back by making it fat, low and slow just
> for the sake of local flights. I barely got my 3kft L2 flight back at
> Kentland. I can't imagine a 5, 6 or 8k foot flight around here (and getting
> it back). I think a road trip will indeed be merited. :)
>
> Thanks again all for the tips. Good info! I'm saving this thread.
>
> BTW.. just fyi.. all posts on this list are automatically archived and
> indexed by google. So anything ever posted here can be quickly found by
> simply googling for "nrv rockerty" + whatever key term or thread subject
> you're looking for and , you have it. I ought to make a google search
> tool for the list on the web site I guss. Anyway.. in case anyone was
> interested.
>
> Tweeks
>
>
>
>
> -------- Original Message --------
> From: bruce fette
> Sent: Sat, 12/07/2014 15:51
> To: nrv rocketry
> CC:
> Subject: Re: [NRV Rocketry] Suggestions for good L2/L3 Rockets?
>
> Tweeks,
>
> As I did my L3, I was guided over and over to make it really strong, and
> really simple!
> Everything must be redundant and everything must work exactly as planned!
> Yes Tripoli rules are slightly different from NAR rules, so read up!
>
> So let me tell you what I did to make everything simple.  for example 3FNC
>
> 1) I used LOC tubes, but if you can find a good nose cone to match the ID
> of a "concrete sonotube", then you can simply fiberglass the sonotube and
> have a really strong design. My most recent visits to Home Depot and Loews
> I didnt find any decent sonotubes. They were all warped out of round and
> beat up. It may be better in Blacksburg.
> I used two pieces of Loc precision 5.5" tubing, for which it is easy to
> find a matching Loc nose cone. I bought a rotisserie and made cardboard
> inserts to the tubing diameter so that I could use that to rotate the
> tubing while glassing and painting.
>
> 2) Since the LOC tubes are not particularly thick, I lined them full
> length with another piece of loc tubing cut down to coupler thickness.
>
> 3) I made a 6 tube fin design where the tube fins were bolted to the frame
> with 8/32 TNUTS and bolts = 6TNC. When it lands, if you break a plywood
> fin, you have to do it all again. If you only bend a tube fin, you can
> straighten out the bend and you are ready to fly again. (Its all about the
> rules). If you choose to do plywood fins, be sure to use 1/2" birch plywood.
>
> 4) Dual deploy is a must so that you land at or below the 15 f/s landing
> velocity. Use two different types of altimeters so there can be no common
> design fault (have one use beeps and the other use LED flashing so you
> don't get confused about the eventual altitude). Use a big chute for the
> main and pop at 500-600 ft so it has enough time to open. And good strong
> risers, and good strong welded eyebolts.1/2" plywood and good big fender
> washers. 1" risers at least 20 feet long and sewn really well by a shoe
> maker.
>
> 5) Motor mount was redundant, both at the nozzle and up at the forward
> closure.
>
> 6) You must be able to shut off the redundant electronics without moving
> the rocket, and you must be able to validate that each squib has fired
> without any danger to the reviewer. So you need to be able to ascertain the
> charges shot without moving the rocket in any way.
>
> 7) With care you can also make the motor igniter redundant.
>
> 8) So my L3 was a single purpose built. But I have recently determined
> that there is a high value in supporting a rather larger diameter motor,
> and doing your construction so that you can insert various motor adapters
> and thereby adapt the motor mount to smaller diameters. I do that by
> inserting a plywood centering ring to adapt the diameter, a smaller motor
> tube and a plywood thrust plate that can bolt to the original thrust plate.
> So I can adapt to various motor plans including clusters with various
> arrangements.
>
> 9) Sure bigger diameter, more drag, lower altitude. The alternative is to
> do your L3 elsewhere (Arizona, Colorado, Las Vegas, Blackrock etc  =
> ROADTRIP :)))!)
>
> Good Luck,
> Bruce
>
>
>
>
>
>   ------------------------------
>  *From:* james desposito <jdesposito69 at hotmail.com>
> *To:* nrv rocketry <nrvr at nrvr.org>
> *Sent:* Saturday, July 12, 2014 1:55 PM
> *Subject:* Re: [NRV Rocketry] Suggestions for good L2/L3 Rockets?
>
> NO it can be a kit
>
> ------------------------------
> From: maier.chris at gmail.com
> Date: Sat, 12 Jul 2014 08:58:07 -0500
> To: nrvr at nrvr.org
> CC: tweeksjunk2 at theweeks.org; nrvr at nrvr.org
> Subject: Re: [NRV Rocketry] Suggestions for good L2/L3 Rockets?
>
> Go motor mount-less.  Fixing a motor mount tube in large airframes proves
> inflexible if you happen to attend an LDRS or big waiver type of launch.
>  You end up having to build another purpose but rocket instead of just
> swapping in a 98mm motor.
>
> I would recommend against any cluster that lacks a central motor capable
> of lifting the rocket solo for a cert flight - too much could go wrong for
> a cert flight, and the highest priority is safety when launching the larger
> L3 type rockets as well.  Air start your clusters to minimize issues and
> provide better distance between the rocket and spectators in case there is
> an issue like one of the motors doesn't light or come up to pressure at the
> same time as the others.
>
> Don't the rules still specify an L3 project has to be scratch built?
>
> Chris
>
> On Jul 12, 2014, at 7:23, james desposito <jdesposito69 at hotmail.com>
> wrote:
>
> After a lot of homework and building a 5'' Big Nuke kit from Loc for my
> level 3 i found out it is going to hit a altitude of
> over 10,200 feet and not to many places to fly. know I''m thinking more
> toured a 7.67'' rocket like the  Bruiser-EXP - 3"
> <http://shop.locprecision.com/product.sc?productId=157&categoryId=17> from
> Loc that will stay under 10,000 feet with the smallest M. You have a better
> chance of keeping your rocket with an 8'' just my opinion. jimmy d
>
> > From: tweeksjunk2 at theweeks.org
> > To: nrvr at nrvr.org
> > Date: Sat, 12 Jul 2014 02:00:08 -0400
> > Subject: [NRV Rocketry] Suggestions for good L2/L3 Rockets?
> >
> > Hey all..
> >
> > So we've had a lot of people certing up as of late. They've got their
> Level-1
> > (H-I motors) and Level-2 certs (J-L).. and some are trying (or at least
> > starting to think about) their Level-3 now (M-O motors).
> >
> > I'm thinking my next big rocket will probably be a 5" (dia) airframe,
> probably
> > all fiberglass or bluetube. Maybe scratch built (with a nice big ebay
> for lots
> > of electronics and HAM radio gear).. maybe a kit. I like the flexibility
> of a
> > multi-motor cluster, like what Giovanni had on his black momba:
> > http://nrvr.org/photos/2012-02-04-5_NRVR-VAST-VT-Launch/IMG_2421.JPG
> > http://nrvr.org/photos/2012-02-04-5_NRVR-VAST-VT-Launch/IMG_2422.JPG
> >
> http://nrvr.org/photos/2012-02-04-5_NRVR-VAST-VT-Launch/video/MVI_2435.flv.html
> >
> > or maybe a just a more traditional single 75mm:
> >
> http://nrvr.org/photos/2011-09-10-11_NRVR-VAST-Launch-WEB/2011-09-10-11_nrvr-
> > vast-launch/img_1053.jpeg.html
> >
> > Suggestions.. thoughts.. related questions?
> >
> > Tweeks
> > p.s. we're working out the final details for another Kentland launch in
> two
> > weeks (26th).
> > _______________________________________________
> > NRVR mailing list
> > NRVR at nrvr.org
> > http://nrvr.org/mailman/listinfo/nrvr
>
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