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First rocket build - need some advice

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JimiB

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Not sure whether to post here or in another forum section, but since this is my first post about my first rocket build I figure this is the right place.

Like many here, I'm coming back to Rocketry as a grownup after dabbling in it as a kid some 50 years ago. Selected the Screamin Green Meanie kit from Apogee just because it looked fun and was a bit more advanced than the Estes kits I did as a kid. So far I'm pretty happy with my results. I know I've made mistakes so far but it's a learning process and I've got some time to learn with future rockets.

Here's my question. I basically followed the instructions that came with the kit and the video instructions that Apogee kindly provided on a DVD with my first order. When I built Estes kits as a kid, I knew nothing about hardening balsa fins with wood putty or fillets when you join fins to the body. Seemed simple enough and I did an ok job on both, but I can tell some experience will help me improve my techniques.

Now I'm at the point of painting. I applied several coats of a wet sandable primer, at what I thought would be thick enough to fill imperfections and sand. But, after just a little bit of very light wet sanding with 400 grit paper I can see some bare wood and a bit of the white on the tip of the plastic nose cone. Photos are attached.

Should I back up and spray on more of the sandable primer? I used Krylon ColorMaster Gray Indoor/Outdoor Primer. Is that a decent choice? How important is the primer? Seems like it is not just to build a base for the final paint but it may add to the overall strength of the rocket and help fill in little imperfections which I assume improves aerodynamics. I guess the real question is, is the primer more about the look or is it important to how well it flies and recovers?

SGM-NoseCone.jpg


SGM-Fin2.jpg


SGM-Fin1.jpg
 

Rex R

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I am not familiar with that primer, what sort of recoat times does the can list? those areas you're showing are notorious for sand through because a) you're probably not getting as much primer there and b) the amount of sanding pressure per square inch goes up drastically when you try to sand them. I generally do 2 coats sand down to where the high spots start showing through, then one or two coats more, followed by sanding with very light pressure. think most folks use 'automotive filler primer'.
Rex
 

samb

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Welcome back to the party JimiB. Finishing rockets is always a great conversation on the ol' forum. The Apogee tutorials are a great reference. You'll find that the TRFers have a variety of techniques and favorite materials as well. Definitely not one size fits all. I have a couple of suggestions based on your pictures.

Hit the bare wood spots with filler - Elmers Carpenters Wood filler or Bondo Spot putty

Don't spray any more until you've done some more sanding. I like those 3M sponges for curved surfaces and regular sandpaper (not wet/dry) on a block for the flat surfaces. I tried wet/damp sanding early on but it just doesn't work for me.

Your pictures show a pretty grainy surface, that looks like dry spray. Happens when you hold the can too far away and the paint partially dries before it hit the surface. Generally, 6-8 inches works for me with Rustoleum Painters Touch and it's just a feel thing that takes practice. Anyway you'll want to get that surface smooth to the touch before you put another coat on.



On a different subject, where are you flying ? Art Applewhite has a nice website with Texas club launches listed. I think you're in a good spot to visit some of them sometime.

http://www.artapplewhite.com/launches.html
 

Nytrunner

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Finishing isn't my area of expertise, but I've learned a thing or two through trial and error and listening to people debate it on the forum.

Primer is Not a structural element. Adding a lot more will likely just add weight to your rocket which could easily outweigh (hah) any benefit from the smoother surface.
Here's a link to a cool blog post about that very thing http://rocketn00b.blogspot.com/2016/11/the-weight-of-paint.html.

There are also competing schools of thought to primer. A) spray on some coats, then sand Almost All of it Off. That leaves it filling low spots. repeat a couple times as necessary.
B) Spray on coats, sand smooth (not sanding most of it off, but allowing it to sand through high spots), Evaluate and either recoat/sand or spot putty/sand/recoat etc.... Like school A, repeat until you're happy.

The primer phase does prep for paint adhesion, and is also a good time to hit those imperfections like you mentioned in your post. Filler primer can get light stuff, but prominent dings, or scrapes, or grain marks will need some woodfiller or spot putty.

Perhaps the best advice I can offer is......Don't let this be your last rocket. Experiment, try out what we say (or 1 of the 5+ options you'll be presented with on here, heh), see how it turns out! If you don't like it, the next rocket is a great place to try something different.

(also, don't wetsand primer. It's porous and will have a party with cardboard/paper tubes)
 

Scott_650

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Couple of things to keep in mind - website photos tend to "smooth out" the subject so looking at the Internet to see what a finished rocket looks like is a little deceiving. Secondly, for the majority of us hobby rocketeers, the performance gain from a smooth finish on our rockets is irrelevant - unless you're contest flying does the handful if extra meters of altitude a mirror smooth finish can provide really matter? Third, it takes lots of practice to achieve the kind of results you see experienced modelers produce. To me, the big difference between model rocketry and say building plastic aircraft models, is our models DO something - and while doing that something they make fire and smoke! Just too cool! Bottom line: build and launch as much as you can and you will find what works for you and your skills will improve.
 

JimiB

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Thanks everyone for the suggestions. Very helpful and I feel a bit more confident that at least I haven't screwed up completely.

The Krylon ColorMaster Primer can states "Dries in 10 minutes or less. Handle in one hour. Recoat or topcoat anytime." I gave several hours between coats and overnight before sanding. The automotive primers I found nearby all seemed to be for metal only. This was the only one I found that stated it worked on wood, paper & plastic. I'll try some different primers on my next build but think I stick with this to be consistent for this rocket.

The Apogee video only mentioned wet sanding for the primer but I was worried about that while I was doing it. Think I'll dry sand this coat, then add a couple more coats with light dry sanding until it's almost finished and then a quick wet sand for the final primer coat. I did notice the grainy texture of some coats I applied. I'll try spraying closer to the surface and see if that works better.

Thanks, NYtrunner for the blog link, that was incredibly informative. I had no idea how much weight paint could add. I'm not going for performance here, just wanting it to look decent and hopefully not fall apart on launch so I won't worry about added weight affecting performance. I'm surprised that paint doesn't add strength, just seemed like it could. I'm planning to start with a D motor for first launch and then work up to F if it holds together. None of the rockets I built as a kid flew with anything near that powerful so this is pretty exciting.

I live in downtown Austin and I've gone to several launches (just observing for now) with the Austin Area Rocketry Group - AARG.org. I've looked at Art Applewhite's site too. The San Antonio club has launches about the same distance from me as the AARG launch sites, only in the opposite direction and on different days. Maybe I'll go to both and get in 2 launches/month - WooHoo!

D
on't worry, this definitely will not be my last rocket. Seems I've caught the bug and I'm already looking into what I want to build next.
 

Tonimus

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I dry sand my primer as well. I very rarely wet sand anything. Ultimately my rockets are coming down in the desert at about 20 feet per second, so after their first flight they are going to have some imperfections. Static models I make get the really meticulous finish. Flying rockets get a working finish. Hell, my biggest rocket, I didn't even fill the spirals before painting.

As far as the bare spots you have sanded to, those are extremely common. The paint is the thinnest at points, so it is easy to sand through. My best paint job on a rocket looked like a mottled mess before I laid the first coat of color.
 

Bdpeters

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There is nothing wrong with wanting a smooth nice finish and there are some modeler out there that exemplify craftsmanship and artistic ability. Just keep in mind that after flying the rockets tend to start getting scuffed up. We can be proud to show off a dirty scuffed up rocket that has survived many flights and landings. Keep working on your finishing technique and soon you will start seeing results.
 

Nytrunner

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Ehh! I've got one of those! Now THAT was a prime example of how Not to paint a rocket. I knew nothing back then.
Prime/mask/paint a 4-color scheme in a week? Sure! Cure time? Fake news!

Fortunately the build was better than the finish, and the cert went smooth. Needs some cleaning after a few flights though, and I'm considering stripping down the paint and redoing it.

IMG_20170823_204435845.jpg
 

JimiB

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Back again. After some trial and error I've learned a few things about finishing and painting. Thanks again to everyone for the helpful hints and support.

My next build will go faster and perhaps better, but I'm pretty proud of this one. My first rocket build in almost 50 years and the only one I've ever done with a custom paint job. Hopefully it will actually fly - I'll find out next Saturday.

For those that are interested, here's the final look. I call it the "Nuclear Scream", with apologies to Edvard Munch.

NuclearScreamFinalPaintWebsized.jpg
 

JStarStar

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Looks sharp!! See if you can get a pal to help you shoot video of the launch!
 

samb

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That's beautiful. Those graphics really stand out. DIY ? Freehand ?
 

GlenP

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with that large diameter tube use lots of wadding to protect the chute, don't worry about the fallout.

Really nice artwork.
 

Pem Tech

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Back again. After some trial and error I've learned a few things about finishing and painting. Thanks again to everyone for the helpful hints and support.

My next build will go faster and perhaps better, but I'm pretty proud of this one. My first rocket build in almost 50 years and the only one I've ever done with a custom paint job. Hopefully it will actually fly - I'll find out next Saturday.

For those that are interested, here's the final look. I call it the "Nuclear Scream", with apologies to Edvard Munch.

View attachment 329315
Congabulations!!
Your Screaming Green Meenie turned out great. Love the custom paint job.
Would you mind if we posted it to our coming Gallery Page on the Pemberton Technologies website? Post more pics please.
 

snrkl

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FWIW, I religiously filled spirals with wood filler and primed/sanded for my first few rockets..

Once I started to see the dings they get and how body tubes can flex and fins can pop off, I have taken a "30ft paint job" perspective - I make my rockets such that they look good on the pad from 30ft away (I had to mentally convert that from 6m to ft, incase anyone was wondering...) These days I don't fill tube spirals, but have found a reasonably affordable automotive filler/primer that does OK.. I am still not happy with it and will continue to experiment with easy prime/fill processes.

I have found that papering fins is MUCH easier than CWF and sanding them, so I do that on all of my rockets these days.

Mold marks in nose cones, if they are "innies", ie they are actually divots and not lumps that can be sanded out, I have found it really easy to CWF fill them, then sand the CWF smooth then drizzle some thin CA glue into the CWF, which makes the filler practically bulletproof...

That being said, one of my new MPR projects has two variants, one designed to break mach and one for max altitude, so I will likely be MUCH more focussed on a slick finish for performance reasons..

Most of all, it has to be fun, or what's the point.. There are several at my club that tell me they hate sanding and struggle with the paint job, so they just do a quick and dirty finish.. If this keeps it a fun hobby for them, more power to them! I quite enjoy the finishing process, so for me, the paint job is part of the fun, but I don't think I will ever be one of those who will spend 4 weeks sanding and painting a bird with eleventy different grades of wet sanding and polishing complex... (you know who you are, and we are all secretly jealous of your levels of skill and commitment!! :wink:)
 

JimiB

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Don't know how I haven't seen all these replies until today.

Those graphics really stand out. DIY ? Freehand ?
Thanks. The face was from an image I found online but the flames are completely freehand. My lack of true artistic skill kept them simple, which worked well I think.

Congabulations!!
Would you mind if we posted it to our coming Gallery Page on the Pemberton Technologies website?
Pem Tech! Yes! I would be honored. BTW, my next build is your King Krãken. I love those tube fins.

Most of all, it has to be fun, or what's the point..
I totally agree snrkl. Sanding and painting was more work than I expected, but I liked the end result and I had a whole lot of fun working on it and launching.

Speaking of which, the first launch went well. Flew with a D12-5 engine. Rocksim projected 330 ft but I think it was less. Recovered nicely with a very small (1/8 inch) zipper that I'm going to repair so I can launch with a bigger motor next time. Here's a couple of launch photos.

Ignition.jpg


Safe Landing.jpg
 

JimiB

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The 2nd launch of Nuclear Scream yesterday didn't go so well.

Since my first launch on a D12-5 went just fine, I thought I would push the envelope a bit with an Aerotech E20-7W. RockSim projected 785 altitude with 275 ft/sec max velocity so double the previous launch.

Nice fast liftoff but ejection occurred just about 4 seconds after liftoff while the rocket was still accelerating. I could tell when I saw that it wasn't good. Ended up with a really fancy zipper all down the body.

NuclearScream-ZipperCloseup.jpg

Correct me if I'm reading wrong. The specs give a burn time of 1.7 seconds and delay time of 7 seconds so ejection should have happened 8.7 seconds after ignition.

But hey, no pain no gain. Now I have an excuse to really learn how to repair a zipper. She may never be as pretty as she was, but she'll fly again.
 

scsager

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The 2nd launch of Nuclear Scream yesterday didn't go so well.

Since my first launch on a D12-5 went just fine, I thought I would push the envelope a bit with an Aerotech E20-7W. RockSim projected 785 altitude with 275 ft/sec max velocity so double the previous launch.

Nice fast liftoff but ejection occurred just about 4 seconds after liftoff while the rocket was still accelerating. I could tell when I saw that it wasn't good. Ended up with a really fancy zipper all down the body.

View attachment 333417

Correct me if I'm reading wrong. The specs give a burn time of 1.7 seconds and delay time of 7 seconds so ejection should have happened 8.7 seconds after ignition.

But hey, no pain no gain. Now I have an excuse to really learn how to repair a zipper. She may never be as pretty as she was, but she'll fly again.


Ouch - sorry to hear about the zipper.

Lot's of us have been there and done that. I can tell by your post above, you have the "right stuff" for this hobby. :cool:

You are also correct about how the delay works. You'll probably be able to rebuild and make the rocket as-good-as-new. There are also ways to protect against zippers, and there is even a "zipperless" design that can be built-in to the rocket.

I'd like to offer a belated "WELCOME" to the forum. I'm looking forward to a lot more JimiB posts in the future...
 

Cabernut

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Those painful reminders that with this hobby, no risk, no reward applies.

Good luck with the rebuild. It can be gratifying to see a rocket take flight again after major repair.
 

blackjack2564

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Correct me if I'm reading wrong. The specs give a burn time of 1.7 seconds and delay time of 7 seconds so ejection should have happened 8.7 seconds after ignition.
Delay time is after motor burnout, does not include it.

All delays are allowed a 20% variance. Which means a 10 sec. delay[ 20% = 2sec.] could be either 8 sec. or 12 sec.
 

IluvRocketry14

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I'm a finish newbie myself and I'm not super worried about it, most of my rockets are quite ugly, but perform wonderfully. I also use spray paint, and I like how rustoleum looks and turns out better than krylon or the generic stuff. More of a rubbery, plastic looking finish with rustoleum
 

IluvRocketry14

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Aw damn man that stinks. I like to make my shock chords very long. Also I prefer to swap out stock rubber shock Chords with tubular and braided nylon chords. I even style the half and half technique from quest kits a few times. Instead of gluing the shock chord into the airframe, I tie the Kevlar chord on the top centering ring, and then at the end I tie a nylon chord to the Kevlar chord, then attach to the nose.
 

JimiB

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Kintsugi (金継ぎ, きんつぎ, "golden joinery"), also known as Kintsukuroi (金繕い, きんつくろい, "golden repair"),[1] is the Japanese art of repairing broken pottery with lacquer dusted or mixed with powdered gold, silver, or platinum. - Wikipedia

I don't claim to be an artist and I'm not Japanese, but it seemed like a nice way to repair the zipper on my Nuclear Scream while paying homage to that well earned scar. (And if the repair turned out really ugly - it's all just Wabi-sabi.)

First step was to try and clean up the mess and neaten the edges of the zipper a bit. As you can see in this photo I cleaned but didn't neaten very much.

NuclearScreamRepair-1.jpg

Then, I applied a long piece of strong masking tape on the inside to give it some strength and provide a backing for the epoxy. I managed to apply it all the way to the bottom of the zipper with only one wrinkle. Hopefully that won't be a problem later on.

Notice in the 2nd photo below you can see the kevlar chute cord tore partway through the forward centering ring. Now it comes up about midway through the ring instead of through the slot next to the tube body. I'm not sure what to do about that so any advice is appreciated.


NuclearScreamRepair-2.jpg NuclearScreamRepair-3.jpg

For the repair I mixed some Pearl Ex Brilliant Gold powdered pigment into some 15 minute epoxy. It mixes easily and doesn't cause the epoxy to cure quickly. (Unlike my test when I added it to CR and it immediately hardened.) Then I added the hardener and still had a good 5-10 minutes working time. Seems like the powder made it cure a bit faster than 15 minutes and it was definitely thicker but still workable.

I think it looks better in person than the photo shows but maybe that's just wishful thinking on my part.


NuclearScreamRepair-4.jpg

Finally, I smeared some CR around the top inner edge of the body tube to give it some more strength and protect against further zippers. I also plan to make a bumper cushion around the kevlar cord for about an inch length where it touches the top of the body.


NuclearScreamRepair-5.jpg

I'm planning to fly it this weekend and will try to update here and let y'all know how it holds up.
 

Nathan

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Cardboard tubes + thin Kevlar shock cords = you're gonna get a zipper sooner or later.

Once you try fiberglass rockets, you never go back.
 

kuririn

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Nice kintsugi repair. Gold on black evokes memories of Japanese lacquerware. I remember watching an episode of a Japanese TV show called Soko Ga Shiritai ( translates to something like "I want to know about that") where a young housewife had broken a piece of ceramicware in a fit of rage. It was a wedding gift from her in-laws, and she wanted to get it repaired before her husband found out. So the show had it repaired by one of the few artisans left who did this work. Almost good as new, except for the gold line.
For future builds, there are a number of suggested ways to prevent zippers. One is to attach a strip of masking tape at the point where the shock cord and body tubes are even. Another is to paint the rim and edge of the body tube with CA. Still another is to shorten the shock(Kevlar) cord so it is just below the rim of the body tube, and attach the elastic. It's not as convenient, but if it prevents a zipper it's probably worth it. Welcome back to the sport and keep building and flying!
 
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