Estes Pro Series II Doorknob Build

[Spitfire222]

No disrespect taken... I finally got to open the sim (didn't open when I tried to download it first time). Looks like you've taken a lot of the steps I have implemented in my work to heart (Imitation is the sincerest form of flattery). I love that you seem to have the fin decals figured out. That took me a long time to work out on my own. Decals on fins with tabs were a major PITA for me.

You might want to look at some of my most recent sims as I've got some really detailed sims of the Estes Retainers out now.

It's a really nice looking sim. Good Work!

Thanks! I did look at several of your previous sims to get an idea on how to do things, so I will take a closer look at the Retainer. The decals were definitely an iterative process, requiring lots of back-and-forth between OR and Photosohop. I think I got it close enough in the final version. I just hope I got the entire thing correct enough that it yields usable and accurate sims for other building and launching this rocket.

 

[Spitfire222]

Next up to install is the middle centering ring. This is an easy task now due to the upfront work done earlier of locating the green spacer ring. All I had to do was mix up some epoxy, apply some to the body tube and motor tube approximately 2.5” in, and slide in the centering ring until it stopped against the spacer ring. To ensure everything was in the correct position while the resin cured, I partly inserted the fins and rested the entire assembly on the bench facing up so that the fin trailing edges rest flat and even.

I printed out a fin layout diagram from PayloadBay.com, and used spray adhesive to attach it to a sheet of foam board. I cut out the diagram using a brand new #11 blade, as dull blades tend to tear up the poster board. After a dry-fit, I mixed up some 30-minute epoxy, and brushed it onto the middle centering ring, the motor tube, and the fin root edges (being sure to get epoxy on the forward part of the fin root that contacts the now-hidden green spacer ring). Once all four fins were in place, I added the fin holder along with some rubber bands to hold the fins tight to the body and motor tubes for a good joint.

At this point, I decided to just glue in the aft centering ring too, since I had enough leftover epoxy. Originally, I was planning to use some leftover fiberglass and lay that up inside the fin root joints to reinforce them before closing it up. But perhaps it was just getting late, or that I’m on the tail-end of this build, but I opted to not do this, figuring that the epoxy alone is more than strong enough. I double checked that the aft centering ring was correctly placed by test fitting the engine retainer, and then left everything to cure overnight.

 

[lowga]

Excellent. Fiberglass reinforcement of the fin joints would have been overkill. Also would have added extra weight where you often need it least--the aft end of the rocket. Really great looking build and will be super-strong.

 

[Spitfire222]

Excellent. Fiberglass reinforcement of the fin joints would have been overkill. Also would have added extra weight where you often need it least--the aft end of the rocket. Really great looking build and will be super-strong.

Thank you! Glad to have back-up on the no fiberglass decision. It also eliminated more time-consuming steps.

I have a quick question regarding shock cords. An all of my BAR builds, I've been using a length of kevlar attached to a long piece of elastic cord, with the kevlar terminating below the end of the body tube to prevent zippering (so far, so good for this method). I know that some modelers use long lengths of kevlar only for shock cords, but I'd rather not. I figure I get some ejection charge resistance inside the tube with the kevlar, while still getting some shock dampening from the elastic cord, and it also allows me to use less kevlar per model. Out of curiosity, could I prevent zippering by using a length of rubber tubing (fuel line for nitro RC engines) at the body tube end? (I would secure it with knots above and below to ensure it wouldn't slide up or down the cord. Thanks for any input/advice.

PS: I'm using a chute protector in this rocket, so the length of rubber tubing would be buried in it during ejection.

 

[lowga]

I'll let those with knowledge of the use of rubber tubing speak to that. While kevlar is super strong, the thin string can act like a knife, cutting through the tube. Wider nylon or kevlar cords spread that force out over a wider area.

Another tip. You can "coat' the top of the body tube with a layer of thin CA (Superglue) all the way around the tube. About 3/4 to a 1" in width. Once this dries, the top of the tube will be much stronger. This helps prevent zipper too.

The idea is to get the CA to soak into the paper, not to douse it. I do all my LPR and MPR rockets like this unless they're fiberglass.

 

[Spitfire222]

After all of the fins and centering rings had cured, I added a small fillet of epoxy to the outboard rim of the aft centering ring, and then began working on the fin fillets. I used Titebond Quick & Thick here, which I think is a perfect application for this adhesive. These fillets are only cosmetic to hide any imperfections in the fin-body tube joint where there was some epoxy squeeze out, so the Q&T will work just fine, especially on the smaller sized fillets I prefer. After running a small bead, a smooth pull using a finger yields a nicely rounded fillet.

While the fillets dried, I worked a bit on the Kevlar part of the shock cord, using 300lb strength cord from Apogee. I tied two loops on each end, which will strap around the eyebolt in the motor mount on one end and the elastic part of the shock cord on the other. I add a drop of regular super glue to the knot to secure it, then put a small length of heat shrink tubing to secure the loose end of Kevlar. I usually keep the Kevlar shock cord portion of my rockets to within the length of the fuselage to prevent the chance of zippering, but it was a little inconvenient this time. So I slipped on a length of rubber fuel tubing used for RC aircraft at the body tube lip point. I’ll try to wrap it up in the chute protector, and I’ll see how it fares and reassess if needed.

At this point, the rocket is ready to begin finish work. Before starting that though, I shoved all the extraneous pieces (parachute, shock cord, engine retainer) into the body tube and weighed it for reference, coming up with 320g, already well over Estes estimated weight of 284g.

 

[Jozef]

Try cutting the ends of your rod guides at an angle. It will give a cleaner look. Again...very nice build

 

[Nytrunner]

Are your titebond fillets purely cosmetic, or are you looking for extra structure there?

If structural, you're going to want to apply those before all the primer and filler. Its not as good a bond as to the underlying material itself

(Also woodglue isnt the best for adhering to epoxy/fiberglass)

 

[Spitfire222]

Try cutting the ends of your rod guides at an angle. It will give a cleaner look. Again...very nice build

Thanks for the suggestion!

Are your titebond fillets purely cosmetic, or are you looking for extra structure there?

If structural, you're going to want to apply those before all the primer and filler. Its not as good a bond as to the underlying material itself

(Also woodglue isnt the best for adhering to epoxy/fiberglass)

Purely cosmetic. I'm confident that the fins are securely attached to the surrounding structure, and the fin roots were clear of any primer, etc for a good bond to the body tube and motor mount. Thanks for the tips!

 

[Spitfire222]

I masked off the few areas that I don’t want paint on, such as the launch lug interiors, the rail button posts, and the protruding end of the motor tube that will have the engine retainer adhered to. First, I needed one final coat of primer to unify the surface before color coats, and I figured this was the perfect opportunity to try out my brand new pop-up spray shelter. It worked great, and I’m satisfied with the purchase! After letting the primer dry, I sanded it smooth with 800 then 1500 grit sandpaper. A quick wipe down with a microfiber cloth removes any residual sanding dust, and we’re ready for the white base coat.

 

[o1d_dude]

Thank you!

Thank you for the photo of the Home Right Paint Shelter!

I now have the Air Flow model sitting in my Amazon shopping cart waiting for it to come back into stock in mid-August.

 

[Spitfire222]

Thank you!

Thank you for the photo of the Home Right Paint Shelter!

I now have the Air Flow model sitting in my Amazon shopping cart waiting for it to come back into stock in mid-August.

You'll love it! It takes some practice to get the hang of closing it, but once you get it, it's easy. Enjoy!

 

[AfterBurners]

The build is coming along nicely. You are doing a great job. Can't wait to see it finished. BTW - Where did you get that cutting mat? I'd like to buy one. Never mind I was able to get the name off one of your pictures.

 

[Spitfire222]

The build is coming along nicely. You are doing a great job. Can't wait to see it finished. BTW - Where did you get that cutting mat? I'd like to buy one. Never mind I was able to get the name off one of your pictures.

Thank you! I'm happy with how it's progressing also, but now that I'm in the home stretch, I'm eager to see it completed. The cutting mat is the Fiskars brand, that I'm pretty sure are most commonly found in craft stores like Michael's, or Hobby Lobby, and come in a few varying sizes. I also have a small green Hobbico cutting mat that I picked up at a local hobby store just for small side cuts, and easy to move around. The big, grey mat is pretty much stationary. Get one, you'll love it!

 

[Greg Furtman]

While the fillets dried, I worked a bit on the Kevlar part of the shock cord, using 300lb strength cord from Apogee. I tied two loops on each end, which will strap around the eyebolt in the motor mount on one end and the elastic part of the shock cord on the other. I add a drop of regular super glue to the knot to secure it, then put a small length of heat shrink tubing to secure the loose end of Kevlar. I usually keep the Kevlar shock cord portion of my rockets to within the length of the fuselage to prevent the chance of zippering, but it was a little inconvenient this time. So I slipped on a length of rubber fuel tubing used for RC aircraft at the body tube lip point. I’ll try to wrap it up in the chute protector, and I’ll see how it fares and reassess if needed.

This setup gave me an idea. You used rubber fuel tubing but I bet heat shrink tubing would work well too. I'm going to have to give it a try.

 

[Spitfire222]

This setup gave me an idea. You used rubber fuel tubing but I bet heat shrink tubing would work well too. I'm going to have to give it a try.

Now that you mention it, I might add a piece of heat-shrink over the tubing to secure it and give it a bit more protection. I figured that the fuel tubing frequently comes into contact with hot RC engines for prolonged lengths of time, but a little added protection can't hurt.

On to the color coats! I’m using Krylon for the black and white, and I picked up a small can of fluorescent orange Testors from Hobby Lobby the last time I was there. Krylon also makes a similar fluorescent orange, but when it comes to special/unique colors like this, I tend to prefer to pick up a small quantity, even if it’s less cost effective. I grabbed a small scrap piece of wood to test out the colors, especially the orange, and to see how they would interact with each other. I’m satisfied with the results, and with how the orange looks in person (it’s a bit washed out in photos). The test pieces only had approximately twelve hours between spraying the white, and then spraying the orange, with no negative effects observed. I set up the portable paint booth and after two light coats of white, I put on the third and final coat a bit heavier. This was also the first time using the pistol grip adapter I picked up off Amazon, and it definitely makes using spray cans a bit more ergonomic. Per the can instructions, I will wait forty-eight hours between coats as I usually do on my other models.

 

[Spitfire222]

After two days of letting the white base coat dry, it’s time to begin applying the paint scheme. Fortunately, it’s relatively simple, and Estes provides decent instructions and layout images to mimic it correctly. The actual dimensions provided to position and size the orange areas are particularly appreciated. I randomly picked one of the fins and began masking it off to be sprayed black. After taping off the fin root, I began covering the entire rocket with masking tape and brown paper that I save from rocket packages to recycle for this exact purpose. After what felt like half a roll of tape (sorry, environment…), and a thorough shaking of the can, two quick coats were all that was needed for sufficient coverage. After a few minutes to let the paint initially dry, the several minutes of work masking everything off was undone in a few seconds, and the rocket put aside to dry further. I’ll begin work on the masking and painting of the orange sections later today, after the black has dried for a few hours.

 

[Spitfire222]

Once the black paint dried enough to not be disturbed, I began laying out the pattern for the orange sections. There are four sections of orange paint, opposite of each other, with the bottom two offset by ninety degrees from the upper two. Luckily, it’s mostly straight lines, but I still decided to do it in two steps.

First, I measured up from the bottom of the tube, and down from the top to mark off the upper and lower limits of the body’s orange sections. I cut out a thin strip of paper, and wrapped it around the body tube, securing with tape. I marked off the fin locations, then removed the paper strip. It was then easy to measure the distance between the fin marks, and mark off the midpoint, which will delineate the side edges of the orange section. I re-attached the paper strip to the rocket, re-aligned the fin marks with the fins themselves, and then transferred the midpoint marks to the tube. Using these marks and the piece of aluminum angle stock, I drew a line up the body, which helped guide me to keep the masking tape straight. After yet another half-roll of tape, I sprayed on the blaze orange, let it dry a bit, then removed all of the tape and paper.

 

[Spitfire222]

I made sure to let the orange paint dry long enough that placing masking tape on it would not disturb it. The lower sections of orange stop well short of the end of the body tube, so the upper sections of orange span both the nosecone and the top few inches of the body. To make sure everything lined up, I painted the rest of the orange with the nosecone on the rocket so that I could mask those areas simultaneously. Further complicating things is that the upper sections of orange stop about 1” from the tip of the nosecone. The easiest way I could figure to properly mark and mask off that tip section was to drill a 7/8” hole in a scrap piece of thin plywood, place it on the nosecone, level it as best as I could, then pencil the circumference on the nosecone for reference. I taped off the tip using 3M FineLine tape, which allowed me some stretching to conform to the slopes of the nosecone while following my reference line. I calculated the circumference of this circle, since I knew its diameter, divided it by four, and placed marks there as reference for the tape line. I lined up these upper tip marks with the body tube marks with the help of the 90 degree angle and some string, and then finished off masking the orange sections off. After covering the rest of the rocket with more brown paper and a plastic bag for the fins, I finished spraying the orange, using up the remainder of the paint in the can.

(Sorry I did not get as many photos of this part).

 

[DMehalko]

Looking great!

 

[Theory]

VERY NICE!!!

 

[Spitfire222]

Thanks guys, in the home stretch now!

After the paint was sufficiently dry, I worked on adding the decals. The chrome strips along the upper side of the body tube are self-adhesive stickers. I trimmed out the decals using a new, sharp blade, and applied them with the help of some Mr. Hobby solutions, specifically Mr. Mark Setter to help position the decals during initial placement, and then Mr. Mark Softer to blend the decals into the structure and make them look more painted on than decals.

I ran into two minor issues: first, I accidentally cut through one of the black stripe decals when my straight edge slipped, and second: I found the adhesive on the chrome strips to be pretty weak, and they peeled of pretty soon after application. Regarding the chrome strips, I probably should have very lightly wet sanded the paint before applying for a smoother surface to increase adhesion. Not a big deal, as both are easily solved. For the chrome strips, I luckily have some chrome self-adhesive Trim Monokote. I cut out the required strips, and applied them, and these seem to adhere to the body much better. For the black stripes, I don’t have black Trim Monokote, so I borrowed some black vinyl from my wife’s CriCut stash. I considered painting on the black and chrome stripes, but I didn’t feel like doing more masking at the moment, so self-adhesives it is. I can always remove the vinyl in the future and repaint if it they begin to peel or I regain the will to mask them. Everything will be coated in clear coat, which should help secure the self-adhesive parts and protect the paint and decals.

I have to say, I’m really liking this paint scheme. The day-glo orange combined with the white and black, and the chrome stripes really makes for an attractive, “loud” rocket. Hopefully it helps make it easy to spot in the sky, and on the ground!

 

[neil_w]

Beautiful!!!

 

[Spitfire222]

We’re into the finishing touches now. I few light coats of clear coat were applied, after I once again masked off the rail guide posts and the motor tube stub where the retainer will be attached. I installed the Kevlar shock cord by threading it through the forward centering ring eyebolt, and looping it within itself to create a secure, but easily removable attachment. I did the same thing to the elastic part of the shock cord, attaching it to the Kevlar’s loop. Total length of the shock cord from end of body tube is approximately 5’ 4”, which translates to about 2.3 body lengths. I slipped on the 9”x 9” chute protector, and looped the shock cord around once to help hold it in position along the cord. The parachute quick link was attached to a loop in the elastic, which is about a quarter of the way down the shock cord from the nosecone. The rail guides were installed, with a drop of thread-locker on the screws to prevent them from loosening over time. Finally, I scuffed up the inside of the plastic motor retainer to improve adhesion, and glued it onto the exposed part of the motor tube using JB Weld.

 

[Spitfire222]

At this point, all of the construction is finished and the rocket is essentially complete, with the exception of the remaining task of attaching the nosecone bulkhead. Before I can do that, I need to determine how much, if any, nose weight is needed. Estes provides two cubes of clay that weigh approximately 16 grams, and instruct you to place all of it into the nosecone. Considering my modifications and desire to not add any more extraneous weight, it’s time for a weigh in to refine the Open Rocket simulations and find the estimated CP and CG to determine if I need nose weight. After stuffing everything into the body, the rocket tips the scales at 358 grams, a 38 gram increase from the last, pre-paint weigh in. I used the aluminum angle stacked on some scrap wood as a fulcrum to find the approximate CG, which I found to be just under 17” from the tip of the nosecone (right at the upper rail button location).

 

[Spitfire222]

After overriding the weight and CG in OR, the estimated stability is 1.35 cal, which sounds just right, and means that I will not add the weight in the nosecone. Further, I ran the simulations using multiple different sized motors, from a D to an F. I was getting somewhat low velocities off rod, so I edited the simulations to a 48” rod, which improved the VOR. Still, it looks like my plan to have first flight on Estes BP E16s or F15s might not be feasible, and that it looks like I’ll have to pick up some Aerotech F20s and F23s. If anyone has a minute, I would appreciate any insight into my Open Rocket results, and thoughts on my conclusions for nose weight and motor selection. Thank you!

 

[Nytrunner]

Those look like awfully low exit velocities on the recommended 29mm BP motors.

Is it because of the extra fin weight?
How does your finished weight compare to the stock weight?

 

[neil_w]

Hmm, that's showing 14 oz with a D12, according to Estes spec that would be 11.5 oz. So 2.5 oz extra.

I downloaded the ORK file and tried a few other motors that weren't on the list:

Looks like the E20 comes up a bit short, but the E30, F44W, and F67W look pretty good from here (and most cost-effective at least as far as single-use motors go).

 

[Spitfire222]

Those look like awfully low exit velocities on the recommended 29mm BP motors.

Is it because of the extra fin weight?
How does your finished weight compare to the stock weight?

Yes, that's why I mentioned I doubt I'd be able to use the Estes BP motors as planned. I think the extra weight is primarily in the three plywood centering rings, the plywood nosecone bulkhead, and the eyehooks. Estes estimates 284 grams, so I'm well over, but I have no regrets (for now).

Hmm, that's showing 14 oz with a D12, according to Estes spec that would be 11.5 oz. So 2.5 oz extra.

I downloaded the ORK file and tried a few other motors that weren't on the list:
View attachment 425563
Looks like the E20 comes up a bit short, but the E30, F44W, and F67W look pretty good from here (and most cost-effective at least as far as single-use motors go).

Thank you for doing this! I didn't think to consider these motors; they're 24mm, correct? I'll have to get some adapters for them. I think I might attempt first flight with an E30, and go from there. Very helpful, thanks again!

 

[neil_w]

Thank you for doing this! I didn't think to consider these motors; they're 24mm, correct? I'll have to get some adapters for them. I think I might attempt first flight with an E30, and go from there. Very helpful, thanks again!

The E30 and F44 are 24mm; the F67 is 29mm.