View Full Version : Roachwerks Pershing 1a
I spent the day building a Roachwerks BT-80 sized Perhsing 1a.
Really a very fun, quick build, with enough minor challenges to keep it interesting.
The kit comes with everything you need, including decals and parachute.
All the parts are Roachwerks usual outstanding quality.
First up is construction of the motor mount.
Sandman pretty much figures you know how to build a motor mount.
I really like the inclusion of the kevlar shock cord anchor.
Motor mount is 24mm, E sized, but Sandman says the kit flies best on a D12-3.
He thoughtfully includes an engine spacer in the kit so you can use a D.
Next is marking the body tube for the fins, conduits, and launch lug.
Typical Sandman quality.
Once the motor mount is dry, it gets installed in the body tube with the end of the motor hook flush with the aft end of the Pershing. This is a really thoughtful touch since the completed rocket is, of necessity, quite nose heavy. Allowing the kit to sit flat keeps it from falling over.
Once the motor mount is installed, it's time to build the fins.
There are 3 forward and 3 aft fins. The forward fins are wedge shaped and the aft are diamond shaped with a central bulge.
I had thought these fins would be very difficult to build but was surprised at how easy and sturdy they are with Sandman's recommended technique. Simple cardstock, balsa strip, and white glue construction. Took just a little over an hour to complete all 6 fins.
Sandman thoughtfully includes a whole second set of fin stock in case you mess up, but I didn't have to use it. His instructions are very good and the templates allow you to make the balsa pieces very quickly.
Photo below shows the internals of the fins and how the diamond ones look completed.
On the real missile there were plates that the fins attached to and Sandman includes these as cardstock cutouts. His instructions say to glue these in place on the body tube and then attach the fins but I thought it would be easier to attach them to the plates first and then attach the completed unit to the rocket.
Sandman glued his fins to the plates with white glue and found it worked well.
I preferred to fill the root edge portions of the diamond fins with gel CA which I then positioned on the fin plates. I then used thin CA to fillet the fins to the plates. Worked very well and allowed me to make sure the fins were at right angles to the plates.
I did the same with the wedge shaped forward fins.
The alignment markings Sandman put on the fin plates made this very simple to do.
Once the fin units were complete it was a simple matter to attach them to the body tube. I used white glue to give me a little extra working time so I could make sure the fins were properly aligned.
A very simple conduit runs up one side of the rocket and it took about 5 minutes to shape and apply.
Then the only thing left is to assemble the 3 part nosecone.
A rocket with aft fins this small and additional forward mounted fins needs a ton of noseweight.
Sandman supplies a slug of noseweight he casts himself so it will fit in the middle section of the nosecone. I had to sand out the hole just a smidge and I had to knock a few rough edges off the casting, but then it fit the cone like a hand in a glove. Really outstanding work on Sandman's part.
The slug is held in, and the upper nosecone is secured in place, with a small amount of epoxy.
Sandman recommends not gluing the bottom and middle sections of the nosecone until after they've been painted.
The nosecone pieces are typical Roachwerks turnings, just amazing how well they fit together.
Once the nosecone is complete, you're pretty much done.
The kit comes complete with a Mrs. Sandman X-form ripstop nylon chute and Excelsior decals.
In light of the weather here it will be some time until I can get around to painting and decaling but at least the build is done.
Really a great kit, which is also available in a BT-60 C6-3 sized version.
Thanks, Sandman!
dwmzmm
01-01-2009, 12:17 AM
Nice build, Gus! I like the fact the nosecone has three parts. The quality of the entire kit looks first class. Can't wait to see the finished model and (of course) the flights! Keep us posted.
chanstevens
01-01-2009, 08:18 AM
Wow, that does look like a nice day's build/project. Almost tempts me to pull mine out and work on it, but I'm a snob and think a fine kit like a Roachwerks has to age first, so I typically let 'em sit a year or so in the build queue, then I scramble to put 'em together right before a NARAM or some other contest...
sandman
01-01-2009, 09:19 AM
Gus, great build thread!
Although I show it on the alignment pattern sheet and include it in the kit, thanks for not mentioning I neglected to include the launch lug in the instructions. :o
Like you guys have never forgotten a launch lug before! :rolleyes:
Chan, you crack me up! The kit is soo easy to build I expect you to build it at the field, not he night before!
I would really like to see you enter a model with a "wet paint" sign on it! :D
MarkB.
01-01-2009, 09:52 AM
Very Cool . . .
After I finish the Delta II, I'm going to have to get one.
Sandman, now how about a Pershing II?
(begging, pleading, wishing, hoping)
foose4string
01-01-2009, 10:22 AM
Very Cool . . .
After I finish the Delta II, I'm going to have to get one.
Sandman, now how about a Pershing II?
(begging, pleading, wishing, hoping)
Here is the BT80 Pershing II cone I got from Sandman a couple years ago. It is in three pieces, same as the Pershing 1a version. Very nice cone, but like Chan, have taken my sweet time to get to this project. I built a much smaller BT55 version using paper shrouds and a PNC20 Estes cone.
http://i5.photobucket.com/albums/y192/foose4string/PII-Sandman-cone.jpg
http://i5.photobucket.com/albums/y192/foose4string/Pershing-proto2.jpg
http://i5.photobucket.com/albums/y192/foose4string/P2-20-liftoff.jpg
MarkB.
01-01-2009, 10:48 AM
Fantastic !
How'd you do the details on the side and where did you find scale data? I've been searching the web for months.
sandman
01-01-2009, 01:09 PM
Very Cool . . .
After I finish the Delta II, I'm going to have to get one.
Sandman, now how about a Pershing II?
(begging, pleading, wishing, hoping)
Like foose shows I can make the parts for a Pershing II but as for a kit, I just don't think the Pershing II has the following that the 1a has.
Most of the details are printed cardstock.
Gus told me the fins are more of an origami project. :)
And I have quite a bit of documentation thanks to a lot of YORF members...sorry I forget all the people that send me stuff...I'm really bad remembering names. :o
Meanwhile on the Pershing 1a...would there be any interest in a BT-101 version? same size as the old Maxi Estes kit?
It would be expensive, the nose cone alone if freakin' huge!
I was thinking of either a BP cluster (no way would a BT-101 version fly on a single 24mm BP motor!). Either 3x 24mm or 4 x 24mm or maybe a single 29mm or even a 38mm version???
Meanwhile on the Pershing 1a...would there be any interest in a BT-101 version? same size as the old Maxi Estes kit?
It would be expensive, the nose cone alone if freakin' huge!
I was thinking of either a BP cluster (no way would a BT-101 version fly on a single 24mm BP motor!). Either 3x 24mm or 4 x 24mm or maybe a single 29mm or even a 38mm version???
You're trying to make my wife mad at me, right?
sandman
01-01-2009, 03:56 PM
You're trying to make my wife mad at me, right?
If it's any consulation whenever I come up with a kit that's a hit it makes my wife happy. :D
Untill I tell her she has to make 20 parachutes. :o
If it's any cosulation whenever I come up with a kit that's a hit it makes my wife happy. :D
Untill I tell her she has to make 20 parachutes. :o
They're funny that way, aren't they?
I just found where she hid my stuff for the PEPP Aeroshell. I was waiting to finish it until I had some time, now I have the time and had to promise to knock off a few honey-dos before she showed me where the box is. That's what I get for trying to do it at home.
Um...where would one go about ordering on of these beasts? I've looked around and can't seem to find it. :(
sandman
01-02-2009, 10:23 AM
Um...where would one go about ordering on of these beasts? I've looked around and can't seem to find it. :(
If interested contact me directly via email at
gagnello (at) yahoo (dot) com
Everything I do is pretty much custom made to order.
cas2047
01-03-2009, 04:46 PM
Gus told me the fins are more of an origami project. :)
First off the build comentary and pictures were great. Thanks to Gus for an enjoyable read!
As for the fins, the way they are created using the wood spars and card stock reminds me of the Semroc Sat 1-B fins. They go together the same way and are great looking and surprisingly sturdy when completed. I really like that kind of old school craftsmanship in a kit. It's one of those details that keeps things interesting for the builder.
That's one great looking kit!
sandman
01-12-2009, 10:49 AM
The next step is to see about a BT-101 version.
I've made a bunch of BT-101 pershing 1a nose cone so I thought maybe I should do a Roc Sim.
I want you Roc Sim Gurus to look this over for glaring errors.
One major change from the Estes Maxi kit besides the big balsa nose cone, a 3 motor cluster. I just don't feel a single Estes 24mm motor is going to lift this thing.
Simulation shows 467' with 3 D12-5's but HOLY SNIKES!!! 1,154' with 3 E9-6's! :eek:
And look at the chute deployment speeds. 8 and 20 ft/sec! Cool!
OK, the launch rod speeds are a bit low and one would require a 5' launch rod and the other a 4' rod.
Here's the question I have on this simulation.
Why does the 3 E9 cluster give a higher launch speed and require a shorter rod than the D12's?
46" for the E9's and 60" for the D12's. :confused:
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