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  1. #1
    Join Date
    30th May 2017
    Posts
    40

    Estes Indicator Midpower Upscale

    Of all the LPR rockets in the Estes arsenal, the Indicator is one of the most visually appealing rockets to be developed in recent years. Ever since I first laid eyes on it, it cried out to be upscaled The 4:3 ratio between the lower body tube and upper body tube is a perfect fit for existing mid-power rocketry body tubes (BT-70 and BT-60) as well high-power rocketry using 4" and 3" tubes. Eventually, I want to bring the Indicator to life as a HPR, but baby steps first. The task at hand is to upscale the original to a 50" dream machine.

    I spent the evening taking measurements of original and coming up with an OpenRocket model of the upscale that will be 2.3x the original size:

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    The airframe will be built from cardboard BT-70 and BT-60 tubes, the TTW fins will be 3mm plywood, and it will sport a 29mm motor mount. I'm not sure what motor will carry this bird aloft yet, but I should have a variety of options in the F and low G range that I will narrow down as I start building the rocket and get a better handle on the final overall weight. Simulations will only take you so far until you start adding things like paint and epoxy. So I'm not too terribly concerned about the simulated stability at this point. The rocket will have a customizable ballast system built into the nose cone that will help me fine tune the CG later.

    The recovery system will be a custom-made, single deployment parachute. However, because of the considerable weight that the large fins and motor casing will add to the booster tube, the rocket will also incorporate a zipperless design with the harness attached two-thirds of the way up the BT-60 tube anchored to hardware in the modified bulkhead that will act as a baffle.

    I'm inclined to keep the color scheme true to the original, as seen in the design image.

    Parts for this rocket have not yet been ordered, so it may be a little while before this thread really gets moving, but I can start on some tasks with materials that I have on-hand (like cutting out the fins). Wish me luck!


  2. #2
    Join Date
    26th January 2010
    Location
    Northern California
    Posts
    13,167
    Looks like a fun project! I like the design. I'd want to go right to 3" to 2.2", but that's just me.

    NAR 91107, Level 2

    I really, really hate bugs.

  3. #3
    Join Date
    30th May 2017
    Posts
    40
    I spent a few hours this weekend laying out the fins on a piece of plywood from the hobby store that I had laying around. I picked this piece out months ago without an immediate use for it, but I had a feeling that I'd need it at some point. I'm glad I did. Some of the smaller 6"x12" boards that I had weren't large enough to fit these giant fins. I'm always daunted by the amount of work that a custom fin set from plywood involves, but the end result is incredibly satisfying. The process is as follows:

    1. Measure out a 1cm x 1 cm grid on a sheet of plywood with a plain graphite pencil.
    2. Lay out the x and y coordinates of each of the vertices of the fin using a blue pencil. Where the blue vertical and horizontal lines cross are the vertices of the fin polygon.
    3. Finish by connecting the vertices with a red pencil.

    Click image for larger version. 

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    Next time: Cutting and sanding the fins.

  4. #4
    Join Date
    26th January 2010
    Location
    Northern California
    Posts
    13,167
    Why didn't you just print fin templates from Rocksim or Open Rocket?
    NAR 91107, Level 2

    I really, really hate bugs.

  5. #5
    Join Date
    30th May 2017
    Posts
    40
    That would be too easy.

  6. #6
    Join Date
    30th May 2017
    Posts
    40

    Progress

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    Updates:
    It's been a while since I last posted this build. Progress in the Fall stalled due to various and sundry events that occupied my time otherwise spent on building rockets. The fins were completed shortly after the layout phase in my last update. The motor mount and booster tube were completed over the last several days. It was satisfying to see it start to come together in the dry fit in the final photograph.

    Notes:
    1. The design will need to change slightly from the plan in my original post. I didn't count on just how difficult it would be to find BT-60 to BT-70 transitions. I'm going to have to end up making the transition myself, since the forward fin set is meant to fit against the transition and are therefore cut to a very specific angle. I can't substitute a transition of a different length without substantial aggravation and reshaping of the forward fins. I'd rather just make the transition from scratch.

    2. I originally had three centering rings in the plan, but when I got to the motor mount I decided to eliminate one of them since I couldn't really remember at this point why I chose three to begin with. Sure, with three centering rings, the fin tabs would end up being shorter in length and save me a couple of grams, but oh well.

    3. Once the fins were dry fit and the motor casing was installed, it was immediately obvious just how much weight would be carried in the booster. Obviously this is why the rocket is so long, but I was still surprised by how heavy it felt. I weighed it just to make sure it wasn't way-off from what it was supposed to be and it's tolerable, albeit a bit heavy from the epoxy. I'm very glad that I chose to go with a zipperless design for this rocket, as the risk of zippering would otherwise be very high.

    4. I chose the Madcow retainer for this project to save a little bit of weight. But man, those brass inserts--Holy cow Madcow! They just don't want to go in straight, and trying to drill the massive holes for them in the plywood centering rings without blowing out the inner perimeter of the ring was crazy difficult. It didn't help that I laid them out in the least optimal manner when it came to the grain direction of the top and bottom layers of the three ply wood and started drilling before I realized my mistake. I ended up blowing out a lot of the wood in those layers. I was generous with the epoxy around the inserts to make up for it. In the end, they are very secure and I'm confident that they'll hold.

    5. I'm going to work on the nose cone next while I wait on some centering rings to arrive for the custom transition. I can tell this is going to be a little heavier than originally planned, so I'm working on an adjustable ballast system in the nose cone to make up for additional weight in the booster. It was originally designed to fly on a high initial thrust F-motor and stay under 1,000 feet since it is single deploy. I'm a little bit concerned about the velocity off the rail with the F-motor and the G-motors will put it too high. I'll have to figure something out, but I'm thinking the worst case scenario is I just fly this sucker on a 6 foot HPR rail even if it looks a bit silly.


    Next Up: A Nose Job

  7. #7
    Join Date
    30th May 2017
    Posts
    40

    Nose Job - Part 1 & Centering Tube Construction

    A few quick operations today. First, the nose cone. The nose cone will need to be modified in order contain an adjustable ballast system. Like just about every Estes kit, the original Indicator uses balsa wood fins resulting in a booster tube that is still relatively light considering the size of the fins. In last week's post, I noted that the plywood fins on the upscale make the booster tube quite a bit heavier, thus lowering the center of gravity significantly compared to the original model. I'll need some weight in the nose cone to compensate, but hopefully not too much. Therefore, I'll be epoxying a threaded bolt into a compartment just ahead of the nosecone that I can screw some nuts onto as needed to adjust the weight. How much weight? I'm not exactly sure yet. The OpenRocket file has gotten complicated since I discovered a custom transition would be necessary. I need to go in and make some adjustments, so for now I'm leaving the nose cone unfinished. I'm just going to perform the basic task of prepping the nose cone by removing the plastic shoulder, removing some material along the inner diameter with the hobby knife, and fitting a coupling tube into it that will contain the ballast. Nothing here is being glued together yet, just dry fit.
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    The second thing I completed today was construction of the centering tube. The transition requires fitting a BT-60 into a BT-70. Since this rocket is so tall, it's vitally important the tubes be concentric. Otherwise, it's going to end up looking like the Leaning Tower of Pisa. Because it is that important, I decided to bite the bullet and buy some laser cut rings instead of trying to make them myself. I don't want the finished product looking like garbage because I didn't spend a few bucks on proper centering rings. This will also poke out an 1/8" above the lower booster tube so that I can mount the bottom of the transition to it. If you're curious about the process for the transition, I'll be following the same steps described in the Apogee tutorial on YouTube. For now, there's not much to the first few steps. Just gluing some pieces together, nothing more.
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    With these new additions, I can dry fit a bit more of the rocket and the scale really begins to become apparent at this point. My apologies for the lighting.
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    Next time: I tackle the custom transition.

  8. #8
    Join Date
    15th October 2016
    Location
    Huntsville AL
    Posts
    1,880
    Looking really good! Rockets of this size are super convenient (Except when they go a little.bigher than expected and send you searching for them lol. Chute release is your friend )

    Is Apogee BT-60 stronger than the brown Estes bt-60?

    How heavy is it so far? There are some punchy F motors for the 29/40-120 case, and more for Pro29-2g case.
    (For your next paper/play upscale, try wood glue. It'll save you some weight on the back end and still be stronger than your tubes)

    I believe in your ability to make it fly!

  9. #9
    Join Date
    30th May 2017
    Posts
    40
    Quote Originally Posted by Nytrunner View Post
    Looking really good! Rockets of this size are super convenient (Except when they go a little.bigher than expected and send you searching for them lol. Chute release is your friend )

    Is Apogee BT-60 stronger than the brown Estes bt-60?

    How heavy is it so far? There are some punchy F motors for the 29/40-120 case, and more for Pro29-2g case.
    (For your next paper/play upscale, try wood glue. It'll save you some weight on the back end and still be stronger than your tubes)

    I believe in your ability to make it fly!
    The white Apogee tubes seem to be consistent in quality with the brown Estes tubes. I can't tell the different between the two just by feel and I have both of them in front of me right now.

    The current weight of all components is 341 grams (~12 oz.) w/o motor (but including casing). The OpenRocket design file had it coming in at 337 grams. I still haven't factored in the weight of the accessories (ballast, parachute, harness, paint job), but I'm hoping it won't come in too heavy. The plan right now is to run it's first flight on an AT F62T in a 29/60 case, both of which I currently have. The main concern will be speed off the rail, but with 1010 rail buttons, it won't be hard to find a rail with sufficient length at the club launches. 4 feet will probably be sufficient, but if it comes in too heavy or the day is particularly windy, I'll just put it on a 6 foot rail even if it looks a bit silly.

    The epoxy on this one was necessary on the lower centering ring to reinforce the brass retainer inserts. I could have gotten away without epoxy on the forward centering ring of the motor mount though. I'm going to be very conscious of the amount of adhesive that I use from here on out. The transition assembly will use wood glue and CA. There shouldn't be much stress on those parts in the first place.

    As far as altitude is concerned, I'm intentionally keeping this thing low for it's first flight (900 ft). I'm even keeping the fins square. I just love the look and design of this rocket so much, I don't want it to just be a blur off the launch pad. It's very much made for show. If this works out though, I'd like to go big and convert this into a high power DD rocket with 4"/3" tubes. There's a lot to be said for building a mid-power version of a LP rocket first before upscaling to high-power. I feel like if I do eventually turn this into an HPR, I'm going into it with eyes wide open. This design in particular is much more complex than just a 3F/NC rocket.

  10. #10
    Join Date
    30th May 2017
    Posts
    40

    Transition and Dry Fit

    Rocket Build Marathon weekend is almost over. I completed the transition and performed a dry fit of all the components. As it stands, without the fins epoxied into place yet, the rocket is 4'2" and weighs 12.2 oz. That weight will go up a bit before it's completely finished.

    I printed out a transition template from OpenRocket and followed the steps from the Apogee tutorial on YouTube for creating a custom transition. It came out pretty well. The seam is a bit of a mess, but everything will be sanded, filled, and painted before it's finished, so you shouldn't even be able to tell it's there in the end. The shape itself is wonderful. I did take the additional step of reinforcing the transition with some scrap balsa I had laying around. The reinforcement really helps to keep the shape nice and smooth.

    As you can see in the pictures below, the centering tube slips over the BT-60 and is placed at just the right height that the aft portion of the tube will descend into the lower booster and marry up with the forward centering ring of the motor mount. In this way, the ejection charge will be deployed directly into the BT-60 bube. More importantly, when I rub some wood glue onto it and I shove it into place, there will be no way for it to over travel. As everyone who's ever put wood glue on a paper transition knows, you only get one shot at inserting it. If it seizes up on you in the wrong spot, it's game over. Toss it in the trash and start over.

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    Also pictured above, the forward fin slots were cut out. The forward fins have a small tab, but will not actually join with anything inside the airframe. Nor will be attempting any internal fillets. The sole purpose is just to keep them in place to make them easier to work with when I create the external fillets. It's much easier than dealing with a surface mount.

    Here's the moment of truth. The entire airframe is completed and everything has now been assembled for its first complete dry fit. The original Estes model has been included for scale.
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    So what's next? Well, I've got a little more work to do to complete the recovery system. The rocket is single deployment and will incorporate a zipperless ejection technique. As I've said ad nauseam throughout the build, the booster tube is just so damn heavy (relatively speaking). The booster is a little less than 90% of the finished weight of the rocket without the motor. And I'll be using 100# kevlar string for the harness. I also have to finish up the ballast system in the nose cone, but that will be the final step once I have a better idea of the final weight of the rocket.

    And finally, as the cherry on top of this delightful sundae, I'll be making my custom parachute on the wife's sewing machine using rip-stop nylon in the red, white & black color scheme of the rocket. As for the painting, that will have to wait until the weather warms up.


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