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Discussion in 'Mid Power Rocketry (MPR)' started by James Duffy, Apr 21, 2017.
Will you be entering this model in competition?
EXCELLENT thread, James. It is ironic that I never built the Maxi-Brute V-2, but in the 1970's got some noses (Which Estes sold separately. IIRC) and BT-101 to use for other model projects. But I still have one of the re-released kits in storage.
The link that article has to Into the Wind kites, has a dead link to .370" fiberglass tubes. I found a good link on their site for .370" but holy crap their prices are insane! $25 for one .370 tube 54.5" long.
I use Goodwinds kites for my source for fiberglass tubes for tower rails. .370" is $9.99 for 54.5" ($8.99 if you buy at least 6).
My preference is .505" tubes for rails, and .414" tubes that are a perfect fit as joiners for .505" tubes (Into The Wind did not list .414"). Those .414" for joiners are what make it practical to have say 6 foot long .505" rails that come apart into 3 foot sections for transport (I like to use 12" of .414" joiner for 6" of depth into the middle joint of the .505" tubes). They also have 64" and 75" long .505" tubes.
FWIW - Link below to my website article on a contest tower using those rails, and "Omni-Pad" that I mount it to (Rather than a tripod. I use the Omni-Pad to hold all sorts of launch devices - rocket and glider towers , rail, or rod. Some which are too unwieldy/heavy for a tripod).
A recent set of photos in the image below with the original Omni-Pad (1 x 2 lumber) that holds a heavy 6 foot tall tower as much as 32" above the ground (Tower built by someone else, I recently overhauled it. First two images include a yellow T-Square for size reference). This is definitely not as easy to transport, but an example of having a pad that can hold something as unwieldy as that tower, which won't ever be transported by plane (actually that 1 x 2 wood Omni-Pad was taken for use as the 1987 WSMC, but I realized I needed to make a lighter version for the future). The third image at right shows the 1 x 2 wood Omni-Pad (black) without the tower, but with a bare wood vertical post that holds the 6 foot tower off the ground and allows for rotation for loading the model and possible piston from the tower's bottom ring. The front leg of the Omni-Pad is securely staked down to prevent falling over backwards.
Yes, but that wasn't the original plan. The Bumper project started as a pleasant, low-impact diversion from the competition scale models on which I usually focus, and for the most part it has been a simple, fun build. About half way through the project, though, I began to think of it as a viable alternative to schlepping my Little Joe model up to Michigan for the US Team Flyoffs that take place the first weekend of NARAM. A few days ago the FAI license number went on both stages, which kinda makes it official. Had the project started as a serious competition model a lot of things would have happened differently, such as a lightweight glass body tube for the V-2 and a proper scale nose for the WAC.
Come to NARAM and you can see it fly sometime Saturday or Sunday!
Interesting that you should mention that. In building this kit it occurred to me that the nose cone for this kit would be ideal for big, fat, lightweight sport models that would fly beautifully on the current 29mm BP engines from Estes. The aspect ratio of the cone is a hair over 3:1, which would make it a viable candidate for some neat scale subjects, such as Doorknob, Sandhawk, and the D-Region Tomahawk.
John Boren: is the cone mold for the 100mm V-2 kit around and in good condition?
A quick update: the exhaust vanes have been mounted in place on the model. The positioning isn't quite 100% scale, as we need to keep the vanes out of the exhaust, ironically.
James - Will the "blisters" between the fins get opened up? Aren't those some type of gas vent on the 1:1?
While it would be fun to open up the shrouds, I'm afraid that it won't happen on this particular V-2. That would have required a bit of pre-construction planning and execution, and this project didn't start out with that degree of scope in mind. I might do it on that third V-2 model that is still up on the shelf, though...
You are correct, the two long shrouds cover turbine exhaust vents, while the two short vents cover electrical pull-out plugs.
And if you are unhappy with that small amount of clearance, James can provide you with plans for a low cost adaptor to bring that down to 0.
Not quite zero. But less than the fin span, certainly.
Lol! I still have to visit the Maker Space in Mobile when I get home and wrap my head around how they work. I was just watching some YouTube videos of Adam Savage (Mythbusters fame) and his tour of some of the bigger Maker Spaces around the country. Very cool stuff.
What about opening up those vents would have required any forethought? Can't you just open them up with a Dremel? Though it would have been cleaner/safer to do prior to finish.
I've actually done a bit of a thought experiment on this subject over the past few weeks. If the turbine vents get opened up, it becomes necessary (at least in this dojo) to create a simulation of the inner workings that would be visible within. The surface of the V-2 motor nozzle would be visible, as would the actual exhaust pipe for the nozzle. That's all very doable, but I would prefer to make all of that hoohah Job #1 before the fins are mounted and the engine mount installed.
The electrical pull-out plugs would be simpler, as there is no opening associated with those features that would make the inner clockwork of the V-2 visible.
Maybe for a future project?
I didn't think anything would be visible internally, given the small size of the opening and lack of light internally. It was just an observation I made when looking at full scale images.
For those wondering, at the 2015 tryouts for the World Space Modeling Championship U.S. Team, James had a bit of fun with his scale altitude model. After setting his model up in the pad, he walked back to signal the RSO that he was ready to launch. What he forgot was that he had left his roll of tape at the pad. No big deal, he'll get it later, right? Except he had left the roll of tape on top of his launch tower. The rocket flew through it and ripped all three fins off rather neatly, and he had a cartwheeling scale model sans fins.
Since I had to embarrass the master modeler a little, I will also say that I am very much enjoying the build and am learning a lot from your threads. Thanks for the online tutelage and awesome build thread, James.
I figured the story would come out eventually. And my imagination was somewhere along those lines. Hey, you don't become a Master without learning from your mistakes. Though it is preferred to learn from the mistakes of others. :wink:
To add insult to injury, the motor was a custom AT job that had a unit cost of about $25. No usable data was derived from that particular flight. :bang:
The flight did earn a runner-up distinction in that year's Best Midwest Qualified Flight contest, though!
Glad that you are enjoying it, Brian!
The antennas were fashioned, painted, and installed today, marking the completion of assembly for the Bumper WAC project! The trailing edge antenna details were cut from a section of 6"-long 3/32"-thick dowel supplied with the original Estes kit, and chopped into four 1.5"-long bits. Each bit was chucked up into a Dremel tool that was pressed into service as a poor man's lathe. With a dowel section in place the Dremel was turned to the low-speed setting, and progressively finer sanding sticks were used until a smooth, bullet-shaped profile was achieved. This doesn't take long, less than a minute for each section. Only about 3/4" of each section needs to be shaped.
The shaped sections of dowel were then painted with watered-down Elmer's wood filler to fill the grain (this step is not shown). After the filler dried each section went back in the Dremel for a final polishing with the finest grit sanding sticks.
The sanded and filled dowel sections were then attached to a handling stick for priming and painting. Tamiya black spray lacquer was used for the color coat.
After everything has had an opportunity to dry, the antenna sections are test fitted into the holes we created way back in Post #5, trimmed to the appropriate length, then glued into place with medium CA. (Sorry, should have snapped a photo of this operation, but I think you guys are all smart enough to figure out where the antennas are supposed to go.)
And with that, we're done! I've elected to forego the dirty wash for the airframe joint, and probably won't do a satin coat, either. I'll try and get a good picture of the complete, finished model to share sometime tomorrow.
Ok. We need some final glamour shots of the entire ensemble.
Here's the completed model, along with a few selected statistics.
Overall length: 1033.2mm
Major diameter: 98.9mm
WAC sustainer length: 309.1mm
WAC sustainer diameter: 18.3mm
Mass (less motors and recovery): 391g
Booster motor: Aerotech E15-4
WAC sustainer motor: Estes A3-4T
Avionics: PerfectFlite miniTimer 4
Come to NARAM to see it fly during the opening weekend!
That looks fantastic! And thanks to your thread I have the confidence to build my V2 and get better than satisfactory results. :wink: Thank you James! :clap:
Hopefully, for those of us who cannot witness the launch at NARAM, someone with a high quality video camera and a skilled operator will get footage for us.
A last-minute update as I prepare to pack this model up for the trip to NARAM: the gloss finish on the model was starting to bug me, so it hit it with a matte coat. Rather than use the usual choice of an acrylic overcoat through an airbrush on such a large model, I elected to try this Krylon spray product suggested by Jim Filler:
The Krylon stuff worked beautifully, and I will continue to use it on projects in the future.
Michaels stocks this product in their stores, and they also have a very handy 40%-off coupon that you can pull up on your phone. Be aware that there is a Krylon lacquer product in very similar packaging stocked right next to the acrylic stuff. I strongly suspect that the lacquer would burn a hole right through most decal materials.
Just a quick FYI: the Bumper WAC model flew successfully this past Saturday during the opening weekend of NARAM. I hope to have a couple of photos and a video to share in the next few days.
The model is also prepped and ready to fly at the Austin Area Rocketry Group launch this weekend (August 5), so come on out and fly with us!
Here are some photos of the Bumper WAC prior to flight at NARAM this past weekend, courtesy of the noble and wise Jim Filler:
That's me in the end-of-the-world cowboy hat, along with Scale Judge Bob Ferrante.
Video should arrive in the next day or so...
Here's a quick video of the Bumper WAC model flying at the Austin Area Rocketry Group launch today:
The flight and landing were perfect, although all eyes were on the booster rather than the sustainer. That means that the sustainer is still out in the field somewhere, making the decision to build a spare second stage a wise one. The booster sustained a bit of post-landing damage after the chute reinflated in the wind, but the bruises aren't anything that can't be repaired and repainted.
Just received a couple of great in-flight photos of the Bumper from yesterday's launch, courtesy of Harry Spears:
The extensible staging piston is clearly visible at the forward end of the booster in this shot Harry grabbed just after stage separation.
Fantastic! Great work and very nice flight! Congrats!
Sorry to hear that. I had a pretty decent line on it. :-(
Sorry for the confusion, Mark, as I failed to make the timeline clear. The sustainer was successfully recovered when the rocket flew at the Flyoffs last week, but was lost this week at our monthly Austin Area Rocketry Group launch.
When the bumper WAC takes off, does the engine burn the nose cone any?
Does this cause the need for a repaint of the nose cone every flight?
No, there is no damage to the V-2 nose due to the inclusion of an extensible staging piston. When sustainer ignition occurs, the piston fitted to the aft end of the WAC extends beyond the forward end of the V-2, preventing any damage. The piston needs to be replaced after every flight, but that beats the heck out of repainting the V-2.
See posts #51 and 52 for more detail.
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