Estes Pro Series II Doorknob Build

[Spitfire222]

Hi everyone,

I’m a recent BAR, and I’ve been expanding my new fleet over the last few months. So far, I’ve only launched small low power rockets in local parks, but I’m slowly moving my way up the chain of engine sizes with the hope of making it to a club launch sometime in the near future to really let go my rockets on larger motors. That’s a long way to say I’m going to take my time building this, and probably won’t be able to fly it as soon as it’s finished.

I know many people likely have experience with Estes Pro Series kits, but this is my first. I don’t commonly do build threads, but I figured as a brand new kit, why not. I hope no one minds me sharing this rather typical Estes build process with a few twists.

The kit comes in a nice box instead of a bag. Below is a layout of the kit contents. The body tube has shallow spirals, so not much filling will be required. The nosecone is the same as the Big Daddy one, so it will likely get a “taper-delete” treatment later. It has the standard 24” Pro Series nylon parachute. In addition to the waterslide decals, chrome vinyl stripes are included for the scale paint scheme. An engine retainer and some clay weights round out the usual kit contents.

 

[lowga]

Watching this one with great interest. The kit is in my build pile as well.

 

[Spitfire222]

I like to begin builds by spraying on a coat of filler primer on the bare body tube in order to reduce the risk of over-sanding into the glassine and getting the dreaded “fuzzies” during spiral filling, etc. It also helps to begin filling the spirals, which will get fully filled with CWF. I also begin to prep the nosecone. I sand down the mold seamlines, and apply some Bondo Spot Glazing Putty along the seam to smooth it out and fill any low spots. More sanding, and the seam has been eliminated. After a quick coat of primer and wet sanding, the nosecone is ready to accept paint after we do some more work on the shoulder section later.

 

[Spitfire222]

Next I worked on creating 1/8” plywood centering rings to replace the cardboard ones. Obviously, Estes engineering must have determined that cardboard rings are sufficient, but for some reason, I can’t stand them. I’ve replaced the centering rings on every Estes kit I’ve built as a BAR, down to my Baby Bertha (with appropriately thick aircraft-grade plywood, of course). I’m not interested in maximum performance and altitude, since where I am in the mid-Atlantic, adequately wide open areas are kind of difficult to come by, so I don’t mind a little extra weight. As this model is a bit longer than the Big Daddy, and designed for E and F motors, I’m pretty confident it will handle this extra mass well.

I’ll need four plywood blanks, three for the centering rings, and one to be used later for a nosecone bulkhead. After tracing the outline from the kit cardboard rings, a drill press + forstner bit is used to remove most of the inner material, and a band saw makes quick work of the outer material. To get the rings to their final size, ideally a belt sander would be used, but since I don’t have one yet, a Dremel works just as well. I opened up the motor tube holes first, then sanded down the outer edges of all three centering rings simultaneously while they were on the motor tube to ensure concentricity.

 

[mikewrt]

Subscribed. Never worry about sharing a build around here and the upgrades are a nice bonus. Raising a young family I have little to no time to actually build anything (my 7 month old son is on my lap as I try to type this). Right now I have to scratch my rocketry itch through build threads like yours. Build on my friend.

 

[Spitfire222]

Subscribed. Never worry about sharing a build around here and the upgrades are a nice bonus. Raising a young family I have little to no time to actually build anything (my 7 month old son is on my lap as I try to type this). Right now I have to scratch my rocketry itch through build threads like yours. Build on my friend.

Thank you, and as someone who is expecting his first in about three months, I'm trying to get as much building in now!

 

[neil_w]

Obviously, Estes engineering must have determined that cardboard rings are sufficient, but for some reason, I can’t stand them.

The through-the-wall fins, which are glued to the motor mount, take much of the load off the centering rings.

That said, cardboard rings make me itch as well.

 

[gldknght]

Subscribed. Never worry about sharing a build around here and the upgrades are a nice bonus. Raising a young family I have little to no time to actually build anything (my 7 month old son is on my lap as I try to type this).

[/QUOTE]

Thank you, and as someone who is expecting his first in about three months, I'm trying to get as much building in now!

I think I started teaching my son about model rocketry when he was three or four. Lol, the earlier we start with our kids, the earlier we can get back to the hobby after they arrive, right?

 

[AfterBurners]

The through-the-wall fins, which are glued to the motor mount, take much of the load off the centering rings.

That said, cardboard rings make me itch as well.

No Estes is cheap and over priced and made in china. That's why you get card board rings. Their early kits were much better. I stopped buying their kits years ago.

 

[o1d_dude]

Gotta buy a Doorknob...that 25% coupon from my Rockets by Nadine calendar will just go waste otherwise.

...and then there’s the VanderBurn plywood upgrade kit...

 

[Mugs914]

Thanks for doing this thread Spit! Like the others said, build threads are ALWAYS welcome around here.

I'm going to get one of these kits, but haven't yet so I'm really enjoying seeing how it all goes together.

 

[lowga]

Where does one get the VanderBurn plywood upgrade kit? I'd love to beef up my Doorknob a bit. Also need to add an antenna at the top of the nosecone to make it truly sport-scale.

 

[o1d_dude]

Where does one get the VanderBurn plywood upgrade kit? I'd love to beef up my Doorknob a bit. Also need to add an antenna at the top of the nosecone to make it truly sport-scale.

He’s active here on TRF under the user id @Big_Red_Daddy or you can find him on the Book of Faces where there is a rocketry user group for VanderBurn owners/builders.

Since I last posted here in this thread, I have in fact ordered the Estes Doorknob from Estes World Headquarters AND the VanderBurn upgrade package for it.

And...I just came in from the garage where I was doing some internal fillets on my Panavia clone from VanderBurn.

 

[Bruiser]

Is it a 24" chute? Estes website has it as a 18" nylon chute.

-Bob

 

[Big_Red_Daddy]

It's an 18" chute. I was surprised it wasn't 24" but that's for the bigger PSII rockets.

 

[Spitfire222]

The through-the-wall fins, which are glued to the motor mount, take much of the load off the centering rings.

What's more, if you notice, the middle centering ring has notches (that I have yet to cut out) that interlock with notches in the fin roots, which is definitely a strong bond. Still moving ahead with plywood though!

I think I started teaching my son about model rocketry when he was three or four. Lol, the earlier we start with our kids, the earlier we can get back to the hobby after they arrive, right?

Right! I really hope my son develops a passion for flying like I did!

Is it a 24" chute? Estes website has it as a 18" nylon chute.

-Bob

It's an 18" chute. I was surprised it wasn't 24" but that's for the bigger PSII rockets.

You are correct, my mistake, it is an 18" parachute. Speaking of which, I didn't really work on the Doorknob yesterday, preferring to spend my first Father's Day launching some rockets and putting the finishing touches on the nursery. But in the evening, I did take some time to prepare the parachute shroud lines using split rings and swivel hooks. Might be a bit overkill, but I'm satisfied with how they turned out.

 

[lowga]

Are there any good images of the prototype sounding rocket that can be shared? My Google searches are not turning up much. How accurate is the paint scheme shown on the kit?

 

[Spitfire222]

Are there any good images of the prototype sounding rocket that can be shared? My Google searches are not turning up much. How accurate is the paint scheme shown on the kit?

I assume your Google search yielded the same two images I found below. It's evident Estes based its model on the single stage one which is all orange, while the two stage one appears to have black on the nosecone. The layout looks decently accurate, but of course the colors are more difficult to discern. I wonder if there are any Doorknob rockets in museums? Personally, I consider this a sport-scale model, so the Estes paint scheme appears to be close enough for my taste.

 

[Spitfire222]

Everyone’s favorite step: body tube spiral filling! As previously mentioned, the spirals are relatively shallow out of the box, and the primer got the filling started. After re-hydrating some CWF, I smeared it into the spirals, let it dry, then sanded it all smooth. I find that 400 grit works well here for me, with a final pass of 600-800 grit. (You can see that even with these high grits, the primer has been removed in some areas, but the glassine is still intact). This is as far as I go with spiral filling, i.e. I don’t do multiple CWF applications. Another final primer coat plus the color coats yield a smooth enough finish for me. The body tube is put aside while we work on some other things for now.

 

[Spitfire222]

I got started working on the fins a bit. After cutting them loose, I enlarged the slots in the roots to match the 1/8” thickness of the new plywood centering rings. I also cut out the slots in the middle centering ring, using a combination of the band saw, needle files, and sanding blocks for both tasks. I went slowly here, making sure the fits were tight and even for all four fins, doing lots of test fitting along the way.

 

[Spitfire222]

As is the case with many (maybe most) of you, I don’t generally follow the instructions or their order exactly, especially as slight changes are made to kit components. As seen below, you’re directed to assemble the motor mount fully before insertion into the body tube. However, I’ll only glue the forward centering ring before installing the motor mount into the body so that I have access to the internal fin joints (temporarily using one of the aft rings to keep the motor tube concentric with the body tube). In order for this deviation from the plans to be successful, I’ll need to ensure that I can get the middle ring in the correct position, since originally it is positioned based on the aft ring and fin root lengths. I’ll accomplish this by gluing the included green ring in position while the entire assembly is out on the bench so that it will correctly set the location of the middle centering ring when it’s installed into the body later.

Curiously, the builder is meant to position the aft centering ring along the motor mount tube using the green spacer ring, but I figured I can use the included engine retainer instead, since that is the part that will be attached here later anyways. So, for now, I did a dry-fit only of everything to make sure all joints are tight, and to ensure my planned order-of-operations will work as intended. You can see how the forward section of the fin roots is slightly shorter in the radial direction than the aft section so that it sits on top of the green ring. I’m not entirely sure exactly what is the purpose of the green ring, or why it was designed this way, but the green ring did at least serve a useful purpose for me.

To recap, my planned order of operations is as follows:
1. Glue forward centering ring and green ring to motor tube.
2. Install motor mount into body.
3. Glue in middle centering ring.
4. Glue in fins (when they are complete). Ensure proper adhesion between fin roots and motor tube.
5. Glue in aft centering ring.
6. Glue in motor retainer

This should help me keep track of what I'm going to do, and if anyone foresees any issues with this, please let me know! Again, I believe that the key to being successful here is making sure the green ring is located precisely. And as long as I use the actual components to position it, I believe it should work ok.

 

[Scott_650]

I’m not entirely sure exactly what is the purpose of the green ring, or why it was designed this way, but the green ring did at least serve a useful purpose for me.

I assume the green ring is used to keep the centering ring square to the motor tube - those thin card stock rings can get a little wonky sometimes. Reading your build and Chris Michielssen’s on his blog plus Tony Vanderbeek’s available upgrade rings and fins has me interested in maybe building a couple of these.

 

[Spitfire222]

I assume the green ring is used to keep the centering ring square to the motor tube - those thin card stock rings can get a little wonky sometimes. Reading your build and Chris Michielssen’s on his blog plus Tony Vanderbeek’s available upgrade rings and fins has me interested in maybe building a couple of these.

I suppose that makes sense, though if it was thicker it would be even more effective in that regard. In the end, I don't need it for that purpose. And yes, you should get a Doorknob too, join us! haha

 

[Spitfire222]

As previously mentioned, the nosecone is the same exact one as the Big Daddy’s. Now, there has been a lot of discussion about these nosecones and the shoulder shape and potential consequences of it. I’ll only say that I personally am modifying this nosecone to have a bulkhead + eye bolt, similar to my Big Daddy. However, I wanted to try a different (and admittedly, more difficult) method. On my Big Daddy, I cut off the taper completely, leaving only a short shoulder. Others have simply attached a bulkhead onto the bottom of the stock nosecone. I wanted to try something else: replacing the tapered section with a curved piece of styrene to eliminate the taper, yet maintain most of the shoulder length. I was emboldened by the fact that if this attempted modification didn’t work, I could always turn to the back-up plan of doing it like the Big Daddy nosecone and trimming it down to fully eliminate the tapered section.

First, I cut off the bottom using a sharp Zona razor saw (I love these things) and some masking tape as a guide, and then the taper, cleaning it up with the Dremel and sandpaper. To create the new section of nosecone, I cut a piece of 1.5mm thick styrene to size, softened it with a heat gun, then carefully formed it to the inside diameter curve of the body tube. It took a few cycles of heating and forming before the styrene held the proper shape. I laid it against the opening where the taper was in the nosecone, traced the outline, and trimmed the new piece to shape with lots of test fitting along the way. When I was satisfied that the fit was good enough, the new piece was glued to the nose cone with plastic cement, and it was secured with tape and small clamps.

 

[Spitfire222]

I let the nosecone surgery cure overnight and sanded the joint smooth, then used some Bondo Spot Glazing Putty to blend it all in. After a coat of primer, it looks like it turned out well enough, and the fit to the main body is just right. I then turned my attention to the new bulkhead. After drilling a center hole for the eye hook, I began shaping it to fit into the nosecone using the Dremel. This was a bit more challenging than the centering rings, as those fit into perfect circles (i.e. the body tube). Unfortunately, the nosecone thickness varies around the circumference, and my grafted-on piece doesn’t help the situation. What I ended up doing was marking a reference line so that I could always re-align the bulkhead as I trimmed it down to fit. Eventually, after a lot of trial and error, a good fit was achieved, but I won’t glue it in until towards the very end of the build in case nose weight is needed. After trimming down the eye hook, I bolted it into the bulkhead, using JB weld to secure it. At this point, the nosecone assembly was complete until finish work later.

 

[o1d_dude]

Top marks, Spitfire!

Well done.

 

[mikewrt]

Nice job! Big thumbs up on the mods!

 

[dpower]

No Estes is cheap and over priced and made in china. That's why you get card board rings. Their early kits were much better. I stopped buying their kits years ago.

Cardboard rings are plenty sufficient to fly this kit on any recommended Estes motor. Nothing wrong with beefing them up, but it’s not needed unless you plan to use much higher thrust motors.

Nice build thread! I see this kit in my future. The nose cone mod is a good idea, almost the same method I’ve used, except I just use coupler or a bit of BT cut to size.

 

[o1d_dude]

My VanderBurn Doorknob Upgrade package arrived a few days ago but my Estes kit is being carried by mule train to Denver.

“On the way but arriving later than expected”

Was promised by Friday (yesterday) but sat a few days in Penrose post office before being shipped out to Denver post office where it currently resides.

 

[Spitfire222]

Thank you for the comments! I haven't worked much on the Doorknob these past few days. I'm trying to figure out how to taper the fin LEs. Specifically, if I should create some kind of jig for repeatability, or just free-hand it and hope for the best (<--will most likely do this, since I'm not sure what kind of jig to make).

Cardboard rings are plenty sufficient to fly this kit on any recommended Estes motor. Nothing wrong with beefing them up, but it’s not needed unless you plan to use much higher thrust motors.

Nice build thread! I see this kit in my future. The nose cone mod is a good idea, almost the same method I’ve used, except I just use coupler or a bit of BT cut to size.

Yup, I realize that the cardboard rings are sufficient, but I enjoy the build process of modifying the kit and making it my own! Glad you like it!