Estes Goblin build is complete!

[smstachwick]

Well although this one was rated as an intermediate level kit and it certainly feels about that level to get it into flyable condition, this one was a challenge for me to get to look nice and present it well. I learned a ton and I’m certainly glad that I tackled this before trying something even more challenging.

First challenge I haven’t dealt with in a while: cutting a slot in the centering ring for the motor hook to sit in. Probably not entirely necessary but I decided to rise to the challenge anyway. I did a pretty sloppy job of it but towards the end of the cut I think I found a trick to make it more reliable and neat. It’s difficult to describe but I’ll definitely be using it in the future. You can see my slot job on the complete but not installed motor mount. Thankfully this part isn’t visible from most angles.



Second challenge: fin alignment. Not bad, and passable at a glance or from a distance, but noticeably asymmetrical when you look at it from the tail. I ended up giving up on eyeballing the alignment, so I bought a fin alignment jig to use for my next build.



Third challenge: a nice paint finish. The primer I used made glue residue, wood grains, and paper fibers stick out, giving the airframe a fuzzy look. I made the mistake of trying to paint it like that because I didn’t have fine sandpaper, and the end result didn’t look good at all. I broke down and got some 400 grit and sanded off all the fuzz and bumps. The spots of white primer show where they all were. I ended up putting on another coat after this.


There are still a few spots on the finish where the paint job isn’t perfect, but I figured this is the kind of rocket where I just say “good enough” once I get some noticeable improvement (and learn a few things), then move on. The next model will be better.

Fourth challenge: Decals. This one gave me the most headaches, and I ended up asking the forum for help tracking down a place to print out or buy some replacements. Bruiser was especially helpful, providing the scan himself and giving me a few tips on getting the paper ready to go. Next time I’m going to be much more patient waiting for the factory-provided decals to loosen from the backing paper themselves. Trying to rub them off is what made them rip.
This whole episode also reminded me how much I hate printers. Never let a printer know when you want something done quickly; they can smell fear.

I haven’t given this one an acrylic finish, since Estes is shipping me a brand new decal sheet and I think it would be very desirable to have a logo that’s black and clear instead of black and slightly gray. Maybe someday I’ll revisit this kit and give it the decal job it deserves, but for right now that extra sheet will sit in my range box inside a waterproof bag, awaiting its chance to replace a DIY decal that has fallen off in flight.

But overall I’m pretty proud of the way this turned out. That’s going to look badass as all hell sitting on my spike row or hooked up on the pad. Thanks to TRF for your support, getting it to this level wouldn’t have been possible without you.

 

[K'Tesh]

Congrats on finishing it...

One thing you should know about is Payloadbay's Fin Guide Tool. You enter your values, print out the .pdf that is generated (at 100% (not fit to page)), apply that to some cardboard or dollar store foam core, cut it out, and use it. Make sure that you "notch" the body tube/fin joints (so you don't accidentally glue your guide to the rocket (don't ask)), and use it. You get perfect fins, every time, and can reuse the guides you make. Some vendors (eRockets, etc.) have guides that you can buy, but, unless you can go to the shop and pick it up, you've got to wait for them to be mailed out.

 

[smstachwick]

You know, I wish I’d known about that before, I just dropped $20 for the one Estes sells. I got it at one of the local hobby shops and brought it home today, so I can use it when I start my next build tomorrow.

But if that ever breaks or “walks away” from my workbench, I’ll give that a go and see how it works. Thank you!

 

[K'Tesh]

You know, I wish I’d known about that before, I just dropped $20 for the one Estes sells. I got it at one of the local hobby shops and brought it home today, so I can use it when I start my next build tomorrow.

But if that ever breaks or “walks away” from my workbench, I’ll give that a go and see how it works. Thank you!

Ouch... I hope you have better luck with the Estes guide than I did. I was never able to get mine to work properly. It's been relegated to a glorified rocket stand.

 

[smstachwick]

Ouch... I hope you have better luck with the Estes guide than I did. I was never able to get mine to work properly. It's been relegated to a glorified rocket stand.

It’d better work, I already have a rocket stand. It’s that 2x4 with the a bunch of spent motor casings glued onto it.

 

[EPflyer]

That's a good start. I bet it flies great.

 

[smstachwick]

That's a good start. I bet it flies great.

You know, I can’t believe I hadn’t thought to do a swing test. But your comment reminded me that I should probably do that, so I put in 4 sheets of wadding and a loaded D12-5. It works great, even when starting the swing tail first it’ll come around and fly correctly after a few revolutions.

The packaging says it should fly 1400 ft on a D12, hence the streamer recovery, but I bet my primer and paint misadventures will subtract at least a little from that. The first flight will likely be on a C11 anyway, I’d like to get it back without too much fuss.

 

[Bruiser]

Payloadbay.com has some other very useful tools as well and they are free. Check them out when you get a chance.

-Bob

 

[smstachwick]

Payloadbay.com has some other very useful tools as well and they are free. Check them out when you get a chance.

-Bob

Welp, that’s bookmark-worthy. Thank you again, sir.

 

[bjphoenix]

Second challenge: fin alignment. Not bad, and passable at a glance or from a distance, but noticeably asymmetrical when you look at it from the tail. I ended up giving up on eyeballing the alignment, so I bought a fin alignment jig to use for my next build.

If your concern is the fins not being exactly at 90 degrees I wouldn't worry about that. The most important part is that they be straight along the body tube.

Third challenge: a nice paint finish. The primer I used made glue residue, wood grains, and paper fibers stick out, giving the airframe a fuzzy look. I made the mistake of trying to paint it like that because I didn’t have fine sandpaper, and the end result didn’t look good at all. I broke down and got some 400 grit and sanded off all the fuzz and bumps. The spots of white primer show where they all were. I ended up putting on another coat after this

This is the trick- prime, sand, prime and sand again if you wish, then paint. You can put as much or as little effort into the paint job as you wish, the rocket will essentially look the same setting on the pad or flying. And they do get banged up when flying, or suffer worse damage or loss, so I can't bear to put a lot of effort into finishing because if I build it I will fly it.

Any lessons you learned- you can apply on the next build. That's the beauty of low power rockets- you can build a good fleet without going broke.

 

[neil_w]

If you're doing it right, each build will teach you something new. Sounds like you learned several things in this one. You can multiply your learning by identifying where you encountered problems and look up answers on this forum, where you will find.... "many". Occasionally they might even agree with each other.

A few comments:

First challenge I haven’t dealt with in a while: cutting a slot in the centering ring for the motor hook to sit in.

Wow, I don't ever recall being asked to do that before. Looks like you did fine.

Given that the ring is so far from the base of the motor mount, what I probably would have tried in that situation is to simply "notch" the inside of the ring, enough so that the hook could bend enough to allow the motor to go in and out. A small diamond file is a great tool for making notches like this.

Second challenge: fin alignment. Not bad, and passable at a glance or from a distance, but noticeably asymmetrical when you look at it from the tail. I ended up giving up on eyeballing the alignment, so I bought a fin alignment jig to use for my next build.

Fortunately, that sort of misalignment has no effect on the flyability of the rocket. Over time you'll find your preferred method of fin alignment. There are *many* folks around here who use the Estes jig with great success, and many more who make theirs from the Payload Bay tool.

Third challenge: a nice paint finish. The primer I used made glue residue, wood grains, and paper fibers stick out, giving the airframe a fuzzy look. I made the mistake of trying to paint it like that because I didn’t have fine sandpaper, and the end result didn’t look good at all. I broke down and got some 400 grit and sanded off all the fuzz and bumps. The spots of white primer show where they all were. I ended up putting on another coat after this.

If you're like me, getting a nice paint finish will remain a challenge forever. However, the one rock-solid piece of advice I can give you is: don't spare the sandpaper. You'll use tons of it over the course of your rocket-building career, and 400 grit is probably the most-used when working with low-power. Always have plenty on hand. I use lots of 800 grit as well.

Ultimate paint finish is almost completely dependent on quality of the prep you do to the surfaces before and during. Paint will never "fix" a rough undercoat.

Fourth challenge: Decals.
[...]
Trying to rub them off is what made them rip

If they've soaked long enough they should slide off with little effort. If they don't, then soak them longer. All waterslides are pretty delicate and demand careful handling.

All these things are skills that get better with practice. Best way to practice is to just build more rockets.

If you haven't checked out Chris Michielssen's blog, I would suggest you do so. It is a treasure trove of great advice on build techniques.

 

[smstachwick]

Hey thanks, to both of you. I appreciate the input.

I’ve flown before, years ago. I’m just getting back into it more seriously and more independently than before. I still remember at my very first launch being really upset about losing my newly-built Alpha III, but it was there that a very wise man taught me the importance of learning something from each build, each launch, and each failure. Successes are fun but they’re not learning opportunities, so they need to balance. A truly spectacular failure can also become a funny story later.

That’s the goal here. Learn a little bit from each build and flight.

Example: That transparent one that you can see sitting on my spike row is actually an Estes Phantom, basically an Alpha III made of transparent plastic instead of the typical materials. It’s a classroom display model that clearly says on the packaging that it’s not a flying model. I’m gonna try to fly it anyway. Either I learn that the warnings were right and it’s somehow unairworthy, and it should just sit on the spikes where it looks nice, or I learn that I can fly it after all and get some nice data on its performance. I’m betting on the latter but it wouldn’t surprise me in the slightest to see the plastic motor mount tube melt.

Eventually I’d like to learn enough to fly scale or get a L1 certification.

 

[messedupryan]

That’s the goal here. Learn a little bit from each build and flight.

That happens to be my same philosophy! Thanks for sharing your build, I look forward to many more.

 

[mtnmanak]

First, listen to Neil. No one on this forum does precision building and finishing as well as him. Check out his many build threads for a great course of instruction on building.

Second, I will reiterate that reading Chris Michielssen's blog is invaluable. Start at 2010 and read everything to present . I keep his blog ready on my iPad at all times - especially for Estes builds. Chris is one of the folks that builds the presentation models for Estes. His builds are quite literally "by-the-book".

Finally, just want to give you another thumbs up that your Goblin will fly wonderfully even with a slightly canted fin. It may have a bit of spin on boost, but will be fine. The Goblin is a wonderful build to do when you are getting back into the hobby. It is a super flyer friendly bird. Very forgiving. As you scale up your building, you can scale the Goblins up and up. No matter how big you build them, they fly straighter than anything else in the fleet!

 

[Marc_G]

You know, I wish I’d known about that before, I just dropped $20 for the one Estes sells. I got it at one of the local hobby shops and brought it home today, so I can use it when I start my next build tomorrow.

But if that ever breaks or “walks away” from my workbench, I’ll give that a go and see how it works. Thank you!

Ouch... I hope you have better luck with the Estes guide than I did. I was never able to get mine to work properly. It's been relegated to a glorified rocket stand.

It’d better work, I already have a rocket stand. It’s that 2x4 with the a bunch of spent motor casings glued onto it.

I amended my Estes jig, as I recall... It had too much slop in it for my tastes. I think I put a half inch bolt through the center and wrapped that with a bit of tape to tighten it up. Then I moved on to self designed jigs based on what I learned on this forum, then simplified my approach from jigs that could do 3/4 fins at a time to now just using a basic jig tondo one fin at a time, straight on the tube.

Enjoy the journey! I love your Goblin.

 

[K'Tesh]

My biggest problems with the Estes fin guide are how difficult it was to attach fins accurately when they extend below the bottom of the body tube, keeping the body tube in a place where you could attach longer fin that extended below the body tube, and how much slop it had.

 

[neil_w]

When I'm not just eyeballing, I mostly use a home-made 3D jig described here: https://www.rocketryforum.com/threads/diamond-cutter-build-thread.129671/post-1520722. Given the nature of my designs, it is the one jig design I could come up with that would work in almost every situation.

I should probably update the design, given that I've used it on a lot of rockets now and learned a few things. But it's worked out remarkably well for me.

 

[gjrockets]

Well although this one was rated as an intermediate level kit and it certainly feels about that level to get it into flyable condition, this one was a challenge for me to get to look nice and present it well. I learned a ton and I’m certainly glad that I tackled this before trying something even more challenging.

First challenge I haven’t dealt with in a while: cutting a slot in the centering ring for the motor hook to sit in. Probably not entirely necessary but I decided to rise to the challenge anyway. I did a pretty sloppy job of it but towards the end of the cut I think I found a trick to make it more reliable and neat. It’s difficult to describe but I’ll definitely be using it in the future. You can see my slot job on the complete but not installed motor mount. Thankfully this part isn’t visible from most angles.

View attachment 476605

Second challenge: fin alignment. Not bad, and passable at a glance or from a distance, but noticeably asymmetrical when you look at it from the tail. I ended up giving up on eyeballing the alignment, so I bought a fin alignment jig to use for my next build.

View attachment 476606

Third challenge: a nice paint finish. The primer I used made glue residue, wood grains, and paper fibers stick out, giving the airframe a fuzzy look. I made the mistake of trying to paint it like that because I didn’t have fine sandpaper, and the end result didn’t look good at all. I broke down and got some 400 grit and sanded off all the fuzz and bumps. The spots of white primer show where they all were. I ended up putting on another coat after this.

View attachment 476607
There are still a few spots on the finish where the paint job isn’t perfect, but I figured this is the kind of rocket where I just say “good enough” once I get some noticeable improvement (and learn a few things), then move on. The next model will be better.

Fourth challenge: Decals. This one gave me the most headaches, and I ended up asking the forum for help tracking down a place to print out or buy some replacements. Bruiser was especially helpful, providing the scan himself and giving me a few tips on getting the paper ready to go. Next time I’m going to be much more patient waiting for the factory-provided decals to loosen from the backing paper themselves. Trying to rub them off is what made them rip.View attachment 476609View attachment 476610
This whole episode also reminded me how much I hate printers. Never let a printer know when you want something done quickly; they can smell fear.

I haven’t given this one an acrylic finish, since Estes is shipping me a brand new decal sheet and I think it would be very desirable to have a logo that’s black and clear instead of black and slightly gray. Maybe someday I’ll revisit this kit and give it the decal job it deserves, but for right now that extra sheet will sit in my range box inside a waterproof bag, awaiting its chance to replace a DIY decal that has fallen off in flight.

But overall I’m pretty proud of the way this turned out. That’s going to look badass as all hell sitting on my spike row or hooked up on the pad. Thanks to TRF for your support, getting it to this level wouldn’t have been possible without you.

Looks good! This is one of my favorite rockets to build. To date I've made 5 replicas of this because I've lost some.
Some of the ideas I've adapted are NO engine hooks or blocks, or balsa fins!! I'm a high power rocketry guy so I just use Aeropack 24mm retainers. I've had problems with motors kicking out the back of some of the rockets which is never good. Plus I'm not limited to the size of cardboard motor casings either.
I'd also recommend getting an Aerotech 24mm reload casing. With that you can still use an engine hook (casing is same size as an Estes D motor) but fly anything from a D to an F. (I wouldn't recommend the F39 though- you'll never see it again!).
And because this is a case where the fins are even with the bottom of the body tube you could actually cut slots on the body tube where the fins are supposed to be, glue the fins directly to the motor tube as an assembly and just push that whole assembly up the bottom of the body tube as one unit. With PLYWOOD fins and that double glued assembly you'll have to replace the body tube before those fins will ever break!
My brother also has a 3D printer too so I can get nosecones printed for me. Better than a balsa nosecone, virtually dent proof.
I add more nose weight due to the larger motor types I use but it isn't necessary.
No post would be complete without plugging Mark Hayes and Stickershock23.com for decal replicas. Sure, it's cheap to print your own but Mark does an AWESOME job creating decal replicas in vinyl that are also very sturdy (?) and apply easily.

 

[OG1959]

The Goblin is a cool rocket. Best launch I got from mine was 985 feet.

You learn something new on every build. I like the yellow you chose. Yeah that ring is a pain to cut and after wards I thought "why???" Decal are all about patience.

Nice build and I hope your first flight goes well.

 

[smstachwick]

Looks good! This is one of my favorite rockets to build. To date I've made 5 replicas of this because I've lost some.
Some of the ideas I've adapted are NO engine hooks or blocks, or balsa fins!! I'm a high power rocketry guy so I just use Aeropack 24mm retainers. I've had problems with motors kicking out the back of some of the rockets which is never good. Plus I'm not limited to the size of cardboard motor casings either.
I'd also recommend getting an Aerotech 24mm reload casing. With that you can still use an engine hook (casing is same size as an Estes D motor) but fly anything from a D to an F. (I wouldn't recommend the F39 though- you'll never see it again!).
And because this is a case where the fins are even with the bottom of the body tube you could actually cut slots on the body tube where the fins are supposed to be, glue the fins directly to the motor tube as an assembly and just push that whole assembly up the bottom of the body tube as one unit. With PLYWOOD fins and that double glued assembly you'll have to replace the body tube before those fins will ever break!
My brother also has a 3D printer too so I can get nosecones printed for me. Better than a balsa nosecone, virtually dent proof.
I add more nose weight due to the larger motor types I use but it isn't necessary.
No post would be complete without plugging Mark Hayes and Stickershock23.com for decal replicas. Sure, it's cheap to print your own but Mark does an AWESOME job creating decal replicas in vinyl that are also very sturdy (?) and apply easily.

I may do that overengineered fin thing if I ever get fin damage. Also trying motors up to and including F size is very much the plan.

 

[smstachwick]

The Goblin is a cool rocket. Best launch I got from mine was 985 feet.

You learn something new on every build. I like the yellow you chose. Yeah that ring is a pain to cut and after wards I thought "why???" Decal are all about patience.

Nice build and I hope your first flight goes well.

Thank you! This was just some outdoor yellow I picked up at The Home Depot. Closest I could get to the stock look.

 

[messedupryan]

so you don't accidentally glue your guide to the rocket

fondly recalling my Estes V2 build where I let CA drip down and glue'd my Yellow Estes Fin Jig to the side of my rocket

 

[gjrockets]

I may do that overengineered fin thing if I ever get fin damage. Also trying motors up to and including F size is very much the plan.

What do you mean 'overengineered?'
If you ever do use an F BTW be sure you have lots of space and some good eyes to track it. Just for fun I simmed it it Open Rocket with a CTI F70. Over 2000 feet for that @ about 625 mph. It WILL move fast!

 

[smstachwick]

We’ve got a small field for LPR launches, ceiling about 1000 ft AGL. I’ll definitely be saving the big motors for our HPR site in the desert.