Estes Indicator-2 build thread

The Rocketry Forum

Help Support The Rocketry Forum:

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Hi! Thanks for stopping by. This thread will be covering the build of a new Estes Indicator, #7244, which I don't think anyone has written about building yet. Normally, I don't mess around too much with mini-engine size models. But, like a lot of people, when this one was announced, I thought is was pretty neat. I also thought (and probably others did too) that the design would make for a pretty cool gap-staged design, assuming it would be stable adding another motor to the tail without too much modification. So that's what I set about doing (thus the "-2" added to the name). The first thing I did was open the package, measure the parts, and dive into RockSim:




I admit that I don't have the skill at creating nice renderings like certain OR ninjas do, and I didn't put the time into splitting up the colors on the fins per the face card, but you get the idea. The bottom line is that this will work pretty well, with just a couple of modifications. The rocket has a ton of fin area, comparatively speaking, so even adding an 18mm mount to the tail, it still has a high stability factor. I've elected in the modification to move the included 13mm mount to the upper tube for the sustainer, and use (as mentioned) an 18mm mount for the booster. The catch here is that the 4-second delay on an A3-4T is limiting, and the delay on the A10-3T is worse. According to the sim, it'll work pretty well combining an A8-0 booster motor and a 1/2A-4T in the sustainer. But putting a B6-0 in the bottom or the full A3-4T in the top results in an early deployment, while the rocket is still going up pretty quickly. So, that's an issue, but maybe not a big one. I think I can appreciate a rocket that stages and deploys within about 400', and you can see the whole flight.

Anyway, although the rocket is pretty far along in the build as I write this, I'll be adding to the thread in bits and pieces as I have time. Next update will be going through the parts in the kit and what was added to make the modification.
 
Last edited:

GlenP

Well-Known Member
Joined
Oct 4, 2014
Messages
2,228
Reaction score
516
Could you fit an 18mm in the sustainer and use an A8-5 for a slightly longer delay and heavier sustainer? Or, add some ballast/payload weight or fin drag pods to slow it down on the booster stage. Just some ideas. Looks like you have room to add a transition cone for a nozzle on the booster for some more base drag, and it might look neat to match the nozzle shape with the transition shape, or split the booster from the sustainer at the bottom of the transition, so you have some extra base drag on the sustainer.
 
Last edited:

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
I could make the sustainer minimum diameter and use an 18mm motor in there, but I wouldn't be able to attach the booster in the way I'd planned (and have already built). More on that later, but the transition is part of the booster and the separation is between the BT20 tube and the transition. I may add a cone to the booster yet, but I have reasons for not doing so for now. I don't want to change the basic look or shape, so adding pods won't cut it. Right now, the sim predicts ~50 fps at deployment if I use either a B6-0 & 1/2A-4T or A8-0 & A3-4T combo, though either would put it to about 700'. OTOH, the A8-0 & 1/2A3-4T pairing is good for about 400', which the sustainer alone on either an A3-4T or A10-3T would also achieve (roughly). Keep in mind that the sustainer will be substantially lighter than the original Estes configuration, so it would go a bit higher on the same motor than their claim. Anyway, like I said before, I'm not sure that a 400' two-stage flight is a bad thing.
 

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
OK, phase two. Let's take a look inside the package to see exactly what Estes is giving us:


There's a 5" segment of BT50 for the lower body, a 12" segment of BT20 to form the upper, a plastic nose cone, a plastic transition, a 13mm motor mount with cardstock centering rings, the usual Estes recovery supplies (in this case, with a 9" chute), and also typical of Estes, a nicely laser cut fin sheet made from a nice firm 1/16" balsa. All of the parts are good quality, but in my kit, both body tubes suffered a little in the hands of the shipper. The BT50 tube was slightly ovalized but still usable once the motor mount and transition are glued in. The upper tube was squished at both ends, and partially creased:


So, I cut a replacement tube from my stockpile. To this collection of goodness, I'm adding the following bits:


This includes an 18mm motor tube, standard motor hook, appropriate centering rings for installing both mounts, an 18mm motor block, a bit of 1/8" kevlar, and a length of 1/8" elastic. So all told, this is what I'm building with:
 

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
So, I started building with the motor mounts. The 13mm sustainer mount:


Note the kevlar leader attachment. There are only a couple of options here that avoid the teabag mount. The lower centering ring is spaced a 1/2" up to accommodate the shoulder at the front of the booster. And then the 18mm booster mount:


Because it gap-staged, I can make use of engine hooks and avoid the friction fitting and taping of the motors. I realized in the process of doing this that since booth mounts used 1/4" cardboard centering rings, I did not need the thin mylar sleeves for restraining the engine hooks. So, although pictured originally, they go back in the parts bin. Also, not shown but definitely included, both mounts have an appropriate motor block glued in at this point. Here's the 18mm mount installed in the booster:

 
Last edited:

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Fins. Estes cut the fins out 1/16" balsa sheet, and the material is actually a pretty nice quality. I'll debate about papering them later, but I want to see how they fit up and feel when glued on first. This rocket has 6 fins total, but each fin is made of 2 parts each. Estes would have you glue up both fore and aft fins as shown here first:


For reasons that will become apparent later, I am only going to glue the aft fins up. Once glued, all fins were sanded smooth, along the glue joint and along the root edge.



All leading edges were rounded a bit, and a put small tapers on the trailing edges because I always feel compelled to do so (I'll have to photograph that later). I'll reinforce with CA later as well.
 

GlenP

Well-Known Member
Joined
Oct 4, 2014
Messages
2,228
Reaction score
516
Is the booster designed for tumble recovery? I have been thinking about building a Centuri Excalibur as a gap stager, but haven't gotten started, I just have a bag of SEMROC parts from eRockets and a rough idea for now, so this build will definitely be helpful.
 

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Sort of, in a worse-case scenario. Well, I guess I should explain about the booster at this point. At an URRG launch last summer, I saw a 2-stage rocket separate its booster, and watched the booster sail around gliding like a bird for several moments. In fact, I couldn't tell if it actually was the booster or a bird at first (until it struck the top of the equipment trailer with a thunk). That go me thinking - I figured out a long time ago that almost anything can be made to glide (within reason) for a least a short duration if its balanced properly. So, my goal is to try to set up the balance of the booster, such that with a spent motor in it, it will glide down. I have no idea if it'll really work, or how readily it'll transition from separating to gliding, but that's my intent.

When gliding, the booster will go backwards in relationship to the larger rocket. The fins become wings, and the motor case is nose weight. The aft fins of the Indicator help, as they are forward swept. That means that they're actually swept back in glide mode, which should help the CG placement (it won't have to be as far forward). There are few things I can do to help trim the CG location, but I'll have to experiment with it. This brings me to the forward fins; they're also 2-piece. The grain on the rear portion is perpendicular to the centerline of the rocket, straight out normal. My initial thought was to just glue them to the sustainer and have them hang off the rear, but the grain direction would make them breakage prone. However, it works in my favor if I glue them to the transition. Then, they become small tail surfaces for the gliding booster. If you look at the first image from Rocksim, you can see where it parts - the sustainer carries clipped delta fins, and everything behind the fin parting line is part of the booster. Again, I don't know if it'll really work, and I may have to change it after some experimentation. But that's where I'm going with it at the moment.
 

GlenP

Well-Known Member
Joined
Oct 4, 2014
Messages
2,228
Reaction score
516
really cool idea, it should work and look really cool. The Centuri Black Widow had a gliding booster. the key is balance, you may need to do some glide tests and adjust the location of the spent engine to fine tune by adding engine block shims or adjusting where you glue in the engine mount assembly. it also might help with one larger fin to catch more wind and act like a rudder to allow the other two fins to act like wings to give it some lateral stability.
https://www.oldrocketplans.com/centuri/cenKB-6/cenKB-6.pdf

Maybe you could change the split point of one of the sustainer fins, about 2/3 of the way up the sustainer part, attach the lower part to the booster so it slides off the sustainer asily, this won't change the overall shape appearance. then you might have enough of a rudder at the back end of the gliding booster, and still have enough of a fin on the sustainer.
 
Last edited:

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Good thoughts, though at this point its actually already mostly built. I'll have to play around with it to see how it balances, but so far it looks encouraging. That's possibly another reason to limit motor combinations, so that the CG of the booster doesn't move around - though, probably any spent 18mm Estes case is going to weight about the same.

Anyway, I left off last with the fins. The small fins on the sustainer were tricky to use with my fin jig; they're barely tall enough to engage the rails:


And all three on:


As you can see, I didn't taper the trailing edges of these fins, as they will fit up against the taper fins. Obviously, at this point I'm deviating pretty far from the printed instructions (which I only referenced once or twice). Tied to that, I should explain what I did with the transition piece. This will be the coupling from the booster to the sustainer and will be attached to the booster. As mentioned previously, the small segments of the forward fins will be glued to the transition, and everything from there back will be the booster assembly. So, to prepare the transition, I first cut the end off of the front shoulder with a razor saw, since it was molded with a closed end and a loop for shock chord attachment.



The end was then trimmed up and sanded. Since we're gap staging, I'll need vent holes somewhere on the top end of the booster. Since closer to the 2nd stage motor is better, I decided to drill the transition. And in keeping with the sets of three fins, I decided three holes, spaced between the fins, would be aesthetically pleasing (as much as holes in the side of a rocket can be). So I marked the piece and drilled three .080" holes. The diameter was based on which bit I found first, all told three holes that size should be overkill for the need.



You can see where I remarked the transition with reference lines for attaching the small fins. With that done and the fins glued to the upper tube, its time to attach the fins to the booster. Unfortunately, the booster is too short for my fin jig as-is, so I needed a temporary extension. This is one of the many uses of spent motor casings:


The extension piece is just an extra segment of BT50 that I had in the box. The first booster fin on:


As a side note, I had an extra tail cone nozzle like what's used in the Crossfire kit, and it is a real nice fit onto the booster. It does a good job of cleaning up the look of the tail end, which strikes me as unfinished appearing its stock configuration. I'd suggest anyone else building one - stock or not - to consider using one. Whether I do will depend on how the booster balances, per the previous post.
 

neil_w

Good at some things
TRF Supporter
Joined
Jul 14, 2015
Messages
11,710
Reaction score
4,513
Location
Northern NJ
This is a really interesting build. Very nice work so far.
 

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Update time. The sustainer is all assembled:


Its a fairly handsome little rocket on its own, and the sim projects that it ought to be good for 400-450' on various mini engines. The thing that bugs me slightly is the fit of the nose cone. The shoulder to tube fit is actually pretty good, but the base diameter of the outside of the cone itself is visibly larger than the tube. This cone is the harder, injection molded polystyrene, and although I've tried sanding it down, it'll take a lot more work and material removal to get it to match. I may just pick another cone for it. Maybe I have a similar sized balsa cone, though I'd have to check the influence that has on balance.

With the fins on the upper body tube, I used that as a guide to attach the finlets to the transition. Basically, I lined up the transition in the rear of the sustainer, and (one at a time) placed and held the finlets where I wanted them. Then I applied a drop of thin CA to glue them. I made sure to keep the nose pointed up, so that the CA wouldn't run up and stick the transition to the sustainer. But once in place, I removed the transition piece, applied glue to the other side to make sure I had a good bond, then repeated the process.


Since, unfortunately, my fin alignment on the sustainer isn't perfect (refer back to the jig fit issue), the sustainer and the transition only align one way. When aligned, it looks perfect, but if rotated 120 degrees either way, you can see the misalignment. So, I'll be making sure that things are indexed properly while flight prepping. Here is the finned transition:


These short, stubby fins are actually pretty robust it seems. Anyway, the taller fins of the booster were much easier to align accurately. Here's the mostly-completed booster:


I'd mentioned before about using the molded nozzle tail piece from a Crossfire kit. Here it is fitted in place on the booster:


Like I said before, I think this has a much more finished look, and that JumpJet should really think about adding this to the design. I'll revisit this in a bit. So here's the booster assembly with the transition set in place:


I admit that its a bit unconventional looking, but as such, the sustainer drops a lot of mass when staging, as well as the launch lugs. I then proceeded to attempt some simple glide tests of the booster with a spent motor case installed. I both hand tossed and flung (using the kit-supplied rubber shock cord and the engine hook) the booster into a pile of unfolded laundry. The CG seemed a bit far aft, being just ahead of the rear fin split line. By "ahead" I mean closer to the nozzle end - forward on the gliding booster, but rearward on the assembled rocket. So, I added the plastic nozzle piece, which brought the CG up some. A little better, but still needed to come up. So, I also shortened the rear shoulder on the transition, which is already really long, relatively speaking:


That helped some, but obviously we're talking grams here, not ounces. I'm not sure if I'll be able to get it balanced correctly to glide well without adding a bit of ballast to the nozzle end. That, of course, would have repercussions on the overall rocket balance as well. I think that, as a glider, the booster's wing loading is pretty high. It seems to glide less than it darts. So, maybe this just isn't the platform for a gliding booster. But we'll see, more testing is in order...

The assembled-up rocket (still looks like the Indicator):


 

neil_w

Good at some things
TRF Supporter
Joined
Jul 14, 2015
Messages
11,710
Reaction score
4,513
Location
Northern NJ
Looking fantastic. Did you use any other glue for the fins on the transition, or just the CA? What will you use for fillets there?
 

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Thanks. I used super-thin CA to attach them, since it could really wick into the thin wood. I'm quite certain that there is a glue bond along root edge. I'd also roughed up the plastic surface, so it appears that they're quite well attached, even after some fast glide tests. I'm considering mixing a small of epoxy up to put little fillets on them, but I'm concerned about adding that weight to the tail end of the glider. But we'll see...
 

samb

Lifetime Member
Joined
Jan 22, 2009
Messages
3,946
Reaction score
352
Location
Plano, TX
Really nice build thread here. I have used CA of the gel consistency for small plastic/plastic or plastic/balsa joints like that transition. Lay it in and quickly swipe it with a suitably protected pinky. Or unprotected if you're brave. Just an alternative to consider. A good build thread is a elegant, economical, and organized and this one is good ! :) I wish I had the knack.
 

GlenP

Well-Known Member
Joined
Oct 4, 2014
Messages
2,228
Reaction score
516
...I'll need vent holes... So I marked the piece and drilled three .080" holes...
Not sure if those will be large enough. They should be large enough such that they won't get plugged up with any chunks of propellant. Typical rule of thumb is one vent hole of 0.25" diameter. The area of a hole that size is 0.049 sq in. you would need three holes of diameter 0.144" to get the equivalent area of the one quarter-inch diameter hole. Maybe you can find a 5/32-inch drill bit and make those 3 holes a little larger, or even a 3/16-inch bit (0.1875").

The Crossfire nozzle looks great!
 

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Thanks for pointing that out, Glen. I went back and opened the holes up with a 9/64 bit. That ought to be close enough. I was still working on trying to get the CG farther forward, so I drilled holes in the shoulder as well. I really don't think it made a significant difference (it really didn't remove much mass), but I felt like I was doing something about it...


That's as much as I can practically lighten the tail end of the glider. Further changes need to be made by adding ballast to the nose/nozzle area. To this end, I also stuffed some epoxy clay into the void between the motor tube and nozzle shell:


It doesn't look like much, but there's also some back inside the shoulder of the nozzle piece. That seems to be enough to put the CG where I need it. At least, in glide test, the tail doesn't drop anymore. But, its hard to say if it'll actually "glide" or still just tumble. I'm not sure how to test what it'll do after separation - will it just destabilize and fall, or will it enter a dive and glide out of it? I suppose I could try to fling it on a ballistic path and see what it does... Anyway, it'll either work or it will fall to the ground, but either way it doesn't impact how it flies as a rocket (other than being a somewhat heavier). So we'll see. The completed booster, save lugs:



One other change made is the nose cone. I replaced the one in the kit with the same type, which came out of the Designer Special (circa 1990). This one is a good match to the tube diameter, whereas the stock one was bigger than the tube. It also appeared to be slightly asymmetric, the shoulder didn't seem concentric to the cone base diameter.



Now, my next question is: how snug should the fit between the booster and sustainer be, keeping in mind that we're gap-staging, not directly taped together?
 

GlenP

Well-Known Member
Joined
Oct 4, 2014
Messages
2,228
Reaction score
516
image.jpg
If you find that you are weight limited and can't change the glide balance by ballast alone, you can still adjust the glide by moving the c.p. back if you split the sustainer fin differently and add that fin area to the booster. you probably have enough stability margin on the sustainer to reduce the fin area a little bit. Just an idea .... Might only need one odd fin. You could hand toss glide test the booster with some extra fin just taped on to see if there is any difference at all. You could also play around with a booster-only model in RockSim, if you can adjust the engine weight to an empty casing weight, to see where c.g. and c.p. are located.
 
Last edited:

brianc

Well-Known Member
Joined
Jan 18, 2009
Messages
3,242
Reaction score
3
Like minds think alike!

It's been *forever* since I built a modroc and a day longer since I had logged into TRF.
But when Estes sent the eNewsletter featuring the Indicator, I immediately ordered one
from jonrocket.com - with the full intention of converting into a two-stage. (and later
upscaling to HPR :) )

Searching for a 'stock' RS file led me here. Great job on the build thread! Looks like you've
considered most of the challenges that I've thought of so far. I'm leaning towards cutting
the transition upper tube 1/2 way, adding a stage coupler, then hanging the upper motor
out the aft end (Tulanko Tail style) to provide the connection...

I'll be watching.
 
Last edited:

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
Brian, if you want, I can post my modified Rocksim file and you can rework it back to a stock configuration, or whatever direction you want to take it. All of the important bits are in there, primarily the measurements of the fin segments.
 

brianc

Well-Known Member
Joined
Jan 18, 2009
Messages
3,242
Reaction score
3
I already have a good start on the stock RS file (attached). But if you want to post yours, we can compare notes. :)

The fins are where I last left off and I'm sure the points need some adjusting.

[removed incorrect RS file - so below]

Estes_Indicator_7244_stock.jpg
 
Last edited:

brianc

Well-Known Member
Joined
Jan 18, 2009
Messages
3,242
Reaction score
3
Here's my 2-stage RockSIM file (it's also on RocketReviews.com) and a couple of WIP shots...

I went with the staging coupler option I mentioned earlier. This allowed the gap staging holes to be placed perpendicular to the airframe (vs. in the transition).

I also moved the upper stage fins up from the aft end- this required a small piece of balsa scrap to fill the gap.

IMAG2035.jpgIMAG2038.jpgIMAG2041.jpg

Rick- Hopefully we'll meet on a field somewhere and get the chance to compare our builds (and maybe even drag race :) )


EDIT: Gaaah! discovered I inadvertently uploaded the wrong RS file. Corrected.
 

Attachments

Last edited:

Trident

Retired, plenty of kits
Joined
Jan 18, 2009
Messages
862
Reaction score
9
Your gliding booster is a great idea. Here is an Estes design I built as a kid, called the Tiger Shark. The booster glides. A few months ago I looked this up, with the idea of upscaling it to D power. May just build one as-is. I'll definitely be interested in how yours flies.

https://www.spacemodeling.org/jimz/eirp_22.htm
 

EXPjawa

Well-Known Member
Joined
Jan 27, 2015
Messages
2,205
Reaction score
57
Location
Finger Lakes, NY
That's interesting. I probably have and am overthinking the glider aspect, but if nothing else, the sustainer will shed a bunch of weight and drag after staging, so it ought to really scoot. What I don't have a grasp on yet is how determine if it'll even transition from falling to gliding. Also, I have to remember to post my Rocksim file, which is on my tablet, not my work PC...
 

Latest posts

Top