Qndy's Quixotic Quest #2: Estes Hi-Flier XL conversion to dual deploy

[atrobinson]

After the successful (more or less) build but catastrophic first flight (due to low altitude arming limit on TeleMetrum, not the build) of my Aerotech Strong Arm 38mm/DD conversion, I've decided to scale back my ambitions.

My newest windmill to tilt at: Estes Hi-Flier XL (HFXL) Conversion to Electronic Dual Deployment

YOUR INPUT SOLICITED! I am going to post the steps as I conceive them, rather than as I execute them, so if anyone has constructive suggestions please post them! Be quick though--given my patience, the delay from posting to implementation will probably average around 3 hours with a standard deviation of 1 hour.

The choice of the HFXL is primarily driven by cost. I overreached with the Strong Arm. The total cost of the build was somewhere around $700 including the TeleMetrum (fortunately I recovered all but about $100 of that investment).

Zeroth, I'm implementing dual deployment for two reasons. 1) it's cool and I've launched hundreds of single deployment rockets. It's time for something new. 2) I want to know how high the rocket really goes, so I can judge the accuracy of my design files and simulations. Third (did I say there were two reasons? just call me the Spanish Inquisition), I have a relatively small field and I am keen to recover my rockets when they start getting to 1,000 feet and above.

First, I am not going to try to scale the motor in this one. It comes with a 24mm mount. The main tubes are Estes BT-60 which is slightly too big to turn it into a minimum-diameter 38mm. I could sleeve the lower end of the tube with a 38mm tube from LOC or Blue Tube. I could do that, and then build a 29mm motor mount to fit inside the 39mm sleeve. Given that one of my goals is to get the rocket back (which in my field means the ability to stay well under 1,000 feet), 38mm seems like overkill. Even 29mm seems like overkill. I'd have to make the nose cone out of lead or something. I've RockSimd my design so far and I can get 400+/- feet with a D15, 900 +/- feet with an E18, and 1600 +/- feet with an F39.

Second, I'm going to use an RMS 24/40 case--so all all my motor retention is based on this case.

Third, I'm not going to use the TeleMetrum. I love the TeleMetrum, but I'm going to save that for my level 1 rocket (which looks to be a Mad Cow 4" Patriot at this point). Instead, I purchased a FeatherWeight Raven with 38mm avbay. All told with a 38mm av bay and power perch the FWR costs about the same as a TeleMetrum (sans starter kit). It's not so much the cost of the FWR that attracted me, but the simplicity and lack of RFI susceptibility. Granted, I won't be able to get telemetry or tracking with the FWR, but given my stated goal of keeping it within my private field that shouldn't be an issue.

STEP 1: BUILD THE AV BAY COUPLER. I lied, I've already done this part--but I can discard it if someone gives me a killer idea to implement instead. The FWR 38mm av bay fits in a 2" section of 38mm coupler. It has no wires. I chose a piece of 38mm Blue Tube to hold the bay, but of course that has a good 1.5+mm of free space around the circumference to slide around in the BT-60. So I took the Estes-supplied BT-60 coupler, cut it to slightly longer than 2", and epoxied the Blue Tube coupler inside. There is a slight overhang on both ends that will conveniently retain the FWR av bay bulkheads. The av bay goes together slicker 'n snot and fits well inside the BT-60.

STEP 2: MOTOR MOUNT--PLANNED. This kit is rated out of the box for E motors, but I'm planning to push it to F which is technically MPR. This kit is definitely not designed to MPR standards. Unable to find sturdy 24mm/BT60 centering rings, I'm going to use the cardboard ones from the kit--but I'm going to double up each centering ring with spares I purchased from the local hobby shop. I plan to epoxy them together.

STEP 3: MOTOR RETENTION--PLANNED. I purchased a Rocketarium 24mm threaded retainer. It doesn't fit well on the Estes 24mm motor tube, but with some sanding and CA reinforcement it should be fine. There is positive retention in both directions so I don't need a thrust ring in the MMT--but should I install one anyway?

STEM 4: FIN REINFORCEMENT AND MOUNTING. Given that I'm going to push this to F ("but it goes to 11!"), I'm not comfortable with the strength of the light balsa fins. Short of making my own fins there is no way to get these through-the-wall. I am planning to use CA and possibly tissue (or some other material) skinning the fins to reinforce them--as well as some of my patented, heavy-duty epoxy clay fillets that held up so well when my Strong Arm dirt darted. But... I've gone through the forum and I'm not comfortable that I know how to use CA to reinforce the fins. Everything I've read says "get water-thin CA and brush it on the fins." My experience with CA is that it cures almost instantly so how do I avoid getting my brush stuck to the fin, or my fin to the work surface (wax paper?), etc.?

STEP 5: DEPLOYMENT DESIGN. I want to have the choice to switch between single and dual deployment, and the use of motor- or electronics-based ejection. For motor-based ejection I have a spare BT60 coupler and I can just put the rocket together the way it was originally designed. For dual-deployment I have a couple of choices. 1. Blow everything out one end of the bay at apogee using an Archtype Cable Cutter to release the main. 2. Use two-compartment DD with the drogue in the aft section and the main in front. This would also allow a motor-based charge to provide redundancy for apogee deployment. For single deployment I'd use plastic rivets (as sold by Apogee) to hold the both body tube sections to the coupler. For dual deployment I'd either go with a friction fit for two-compartment DD or plastic rivets holding the av bay in the aft section for single compartment DD.

STEP 6: RECOVERY SYSTEM RETENTION. The FWR has an ingenious method of connecting the shock cord to unused terminals of the av bay. I can't really think of any other way to do it as I can't really drill the FWR av bay bulkheads (they're circuit boards). But I'm not sanguine. Suggestions?

That's all for now. I promise not to implement any step after STEP 1 for another 10-20 minutes.

 

[atrobinson]

Completed so far:
STEP 1 -- Avionics Bay
STEP 2 -- Motor Mount
STEP 3 -- Motor Retention

W&B information:

Following is measured information--remainder if design using RockSim database values

STEP 1:
Blue Tube 38mm Coupler 2" + BT60 coupler 2.125" . . . . 0.51 oz / 14.5g
Raven 38mm Av Bay including all hardware . . . . . . . . . 0.92 oz / 26.1g

STEP 2/STEP 3:
Estes BT-50/24mm cardboard centering rings x 2 . . . . 0.05 oz / 1.4g (forward)
Estes BT-50/24mm cardboard centering rings x 2 . . . . 0.05 oz / 1.4g (aft)
Rocketarium 24mm two-piece retainer . . . . . . . . . . . . 0.27 oz / 7.6g
Estes 24mm motor tube . . . . . . . . . . . . . . . . . . . . . 0.18 oz / 5.0g
Aerotech 24/40 RMS case . . . . . . . . . . . . . . . . . . . 0.69 oz / 19.6g

NOTE: Current design w/ F35 is marginally stable (stability margin .81); Add .5oz/14g nose weight brings stability margin to 1.12

Modifications
STEP 1 - Still an air gap (.5mm +/-) between Blue Tube and BT60 coupler on one side, filled with epoxy & CA
STEP 2 - Doubled rings with healthy coating of epoxy, drilled pilot hole for small eye-bolt for shock cord retention

 

[chadrog]

Pictures! Pictures! Pictures!

 

[atrobinson]

Did someone say pictures?

Picture 1 -- This is how I built the FeatherWeight Raven 38mm av bay housing: by using a Blue Tube 38mm coupler to sleeve an Estes BT60 coupler. There is an air gap, so a healthy coat of epoxy is required, and I sealed any spaces with CA



Picture 2 -- Shows how the Estes 24mm motor tube is deformed by the Rocketarium 24mm retainer. It really doesn't fit. I had to sand most of the tube material away after attaching the retainer in order to be able to insert and remove the motor casing--so I used CA and some epoxy to reinforce the sanded ares.



Picture 3 -- Shows the Estes 24mm motor tube w/ retainer attached, before sanding. I would sand, test-fit, reinforce w/ CA, and repeat until the motor fit. Took some of the black coating of the inside of the retainer but I'm not worried about that.



Picture 4 -- Assembled motor tube with doubled centering rings for reinforcement, and complete retainer (both halves) attached.



Picture 5 -- Shock cord retention step 1 -- drill a pilot hole for the screw eye.



Picture 6 -- Shock cord retention step 2 -- insert screw eye. This seems like overkill, but the smaller versions seemed too fragile to me. Couldn't find any closed-loop screw eyes at Home Despot [sic].



Picture 7 -- Shock cord retention step 3 -- create an epoxy clay thread well for the screw eye to provide a slightly stronger retention base. I started doing this after a screw eye pulled out of a fiber bulkhead in an Aerotech kit. I've had these mounts pull out of a fiber centering ring on an MPR kit rather than the eye itself coming out, so it really does add some strength.



Picture 8 -- Shock cord retention step 4 -- put epoxy over the epoxy clay fillet and over the upper junction of the screw eye and the centering ring. Can you tell I've had issues with screw eyes and centering rings? ;-)

 

[atrobinson]

Some pictures of the av bay, because it is _wicked_ cool... Kudos to FeatherWeight for their 24, 29, and 38 mm av bays.

Picture 9 -- The naked FWR 38mm avionics bay. This is really a masterpiece of engineering. The altimeter, battery, and terminals for all four outputs are available on one end, and the three inputs on the other. There is no need to penetrate the rocket body for switches or static ports (though I will probably add a static port just because--there is a baro sensor on the FWR)



Picture 10 -- One end of the completed 38mm av bay. What looks like an air gap is actually the recessed Blue Tube coupler slightly exposed because I didn't tighten the nuts all the way down. When properly aligned each bulkhead is slightly recessed within the BT60 coupler and has a pretty good seal against the Blue Tube. Still thinking about some kind of gasket material to keep gasses out of the av bay... Suggestions?



Picture 11 -- Elevation view of the completed 38mm av bay. The 4 threaded aluminum rods double as terminals for three of four outputs to the raven. The fourth is available by adding a small screw to the bulkhead you see in picture 10 where it says "4th."

 

[atrobinson]

Windows decided to install some "critical updates" last night/this morning while I was working on my RockSim file. Net impact: all the changes I made yesterday were lost when Windows decided to reboot without asking me. I've been saying it for 23 years: Microsoft must die.

More W&B stuff:

- Mass of screw eye . . . . . . . . . . . . . . . . . . . 0.14 oz / 3.9g
- Mass of epoxy clay (screw eye retention) . . . . 0.03 oz / 0.8g
- 3 x balsa fins BEFORE reinforcement . . . . . . . . 0.81 oz / 23.0g

 

[atrobinson]

It's a good thing I have 100 1/2" brushes, because applying CA with a brush comes out to about one stroke per brush. Not really that bad, but each side of each fin takes up a brush--so 6 brushes minimum, and I've already gone through 6 including some test brushes.

Anyway, I hope I am doing this right: slathering thin CA on the balsa fin with a brush and then letting it dry. Somehow it seems like thinned epoxy would be a better way to go here--but we shall see I guess.

Since I'm only in the testing stage, it's not too late to share fin reinforcement techniques (including how to apply CA, what kind of CA to apply, etc.)!

Andy

 

[atrobinson]

Pictures! Pictures! Pictures!

So it is written, let it be done...

 

[jsargevt]

Windows decided to install some "critical updates" last night/this morning while I was working on my RockSim file. Net impact: all the changes I made yesterday were lost when Windows decided to reboot without asking me. I've been saying it for 23 years: Microsoft must die.

Rocksim works wonderfully on Mac OSX. Sadly, the Raven FIP does not (but booting into windows via bootcamp does the trick....)

Couple of thoughts you can take or leave. Forgive me if any of this was covered above.

1. Be sure to reprogram the Raven to meet your needs. Default it fires the main at 700' which isn't really saving you much if you are only pushing 1000'. I would probably go with 400 or 500 depending on how you are feeling. In fact some might recommend even a 250 main for a LPR/MPR shot but that might be pushing it.
2. With all the weight you are adding in on the back end (Metal retainer, epoxy clay fillets, large eyebolt) Be sure to check the physical balance of the rocket in full flight dress to ensure that you are good to go. While RockSim is cool and very useful for figuring this stuff out sometimes there is a "layer 8" error when it comes to adding in weights in the correct amounts and locations (don't ask me how I know!). Just a physical check is always a good safety valve (I'm sure you were going to do it but hey a reminder isn't a bad thing). If you are extending the length of the rocket with the AVbay + chute tube you should be OK.
3. Be sure to upgrade the parachute for the increased mass. Plus, I wouldn't really trust a plastic chute with 200$ of electronics on board.
4. 3dogs rocketry makes a cool anchor for 8/32 threaded rod: https://www.3dogsrocketry.com/serviceskits.php I think that the rod for the Raven AVbay is 4/40 though but it is worth a check. If you are clever you might be able to buy a 4/40 rod adapter and find a 4/40 eye bolt and use that. However, the cheap way is to do what Adrian says and pierce your kevlar with the rod and then put another nut on top. I'd probably do 2 posts to be safe but it is a clever solution and it has worked for others.
5. You will never find a welded or forged eyebolt at home depot/lowes/local hardware store. Well maybe YOU will but i sure as heck didn't. Mcmaster seems to be the most reliable place to get these https://www.mcmaster.com/#eyebolt-eyelets/=n7z65y If you live near a marina/boat repair shop they might have some eyebolts (and good epoxy). If you do some searching on McMaster Carr on here you can find a LOT of odds and ends to add to an order (PEM nuts, well nuts, Plastic Rivets, shear pins, snap ring pliers, etc, etc, etc). Good to have an option if you don't have a local place to source this stuff.
6. You probably know this but be sure to reinforce the body tubes where you are using plastic rivets. It doesn't take much to enlarge the holes on those LPR tubes.

I think that was all that came to mind. Interesting project and I look forward to hearing how it goes.

 

[atrobinson]

Thanks Jason, that was good for though... Hence more comments and questions below...

1. I've reprogrammed the Raven for a 300 foot main deployment... That may be pushing it as my current plan is to deploy the main wrapped with the cable cutter and no other drag device. RockSim predicts a 120-130fps descent rate which I suspect is high (I configured the cable cutter as a streamer that deploys at apogee), but if accurate means in 2+/- seconds the chute must either deploy or the rocket is going to go splat. Will definitely be a LALO and possibly a LANO (low altitude, no opening). Hmmmn. Maybe 400 feet is a good idea.

I have not seen static ports mentioned in the Featherweight documentation, but I plan to add one (I actually prefer three small ones to one large one). Make sense? With such a low margin for error on the main ejection I want to make sure the baro is as accurate as it can get. Although the way the av bay is designed the 4th input is a hole in the board that will be the equivalent of "ALT STATIC" in my plane--meaning it will read a lower pressure/higher altitude than ambient under most conditions (that would definitely argue for a higher main deployment altitude).

2. I'm keeping pretty detailed weight and balance notes, even in this thread. And while I've learned some important lessons about RockSim I will still do the CG/CP measurements and calculations the old fashioned way. I'm projecting, because the build isn't done (applying CA to the fins seems to add a bit more than .1 oz to the set, for example), but it looks like the rocket will have a healthy 2+ stability margin with D & E and a 1.1+/- margin with the F35 (the heaviest motor I plan to fly in this rocket). The av bay adds quite a bit of weight forward of the fins, and the entire upgraded recovery harness (including larger chute, Kevlar shock cord, and quick links) is in the forward section. Also, I'm planning to epoxy another eye bolt to the nose cone--and that .139 oz actually makes the difference between a good stability margin and a very marginal one with the F35! So it's close, and demands close attention.

3. I'm planning to use the 18" nylon chute from my Aerotech Mirage, which in "full dress" gives a slightly-higher-than 20fps descent rate. I would think that's good enough--but what do you think?

4. I'm going to have to investigate both those 3 Dogs anchors and alternatives. I'm not sanguine about the "clamp Kevlar on the threaded rods" method. I have no doubt it works, it just seems like the sort of think I'll screw up (so to speak), leaving my av bay and altimeter sitting in the middle of the field with no way to find it :-/ I wonder if there is an "o bolt" (more accurately an "o nut") for 4-40? My father has some of these that he uses on his farm equipment so I know they exist, but they are threaded for 1" rods, not 4-40

5. I'll check out that site.

6. I have thought of this, but have put it from my mind because I can't think of a clean way to do it. Some sort of grommet, preferably Kevlar, would be ideal--but I keep reminding myself that this is at the outside a mid-powered rocket, and for the first few launches (D & E) a low-powered rocket. I was thinking about those little self-adhesive grommets they use to reinforce 3-ring-binder holes in notebook paper, but the holes are too big. I was also thinking about flat well nuts--that's not the name for them: the metal or plastic inserts that (more or less) mount flush to a surface and do not intrude (much) on either side, and are threaded to receive screws/bolts.

Thanks again--good suggestions and some confirmation that I'm thinking about the right thigns!

 

[atrobinson]

6. You probably know this but be sure to reinforce the body tubes where you are using plastic rivets. It doesn't take much to enlarge the holes on those LPR tubes.

Something like this would also work (Standard Palnut® Pushnut Bolt Retainers) but these are way too big:

https://www.boltproducts.com/palnut...ushnut-bolt-retainers-c-215_228_229-l-en.html

 

[atrobinson]

I wonder if there is an "o bolt" (more accurately an "o nut") for 4-40?

McMaster provided the answers:

- This is called an "eye nut"
- I can't find any (anywhere) that will fit on a 4-40 threaded rod

*SIGH*

 

[atrobinson]

To adapt 4-40 threaded rod: coupling bolt i.e. https://www.grainger.com/Grainger/Rod-Coupling-Nut-1JA43
An example 4-40 eye bolt: https://www.activepowersports.com/sullivan-549-threaded-eyebolt-440-4/

Now to find these things in the same place...

 

[jsargevt]

Ok I have tried to reply to this a few times today and I kept getting interrupted.

1. On page 3 here it describes with a picture how to secure the Kevlar to the threaded rod. This looks like a pretty easy way to make this work if you cannot source the eye nuts you are looking for. https://www.featherweightaltimeters.com/uploads/38mm_instructions_June21_lower_res.pdf

2. I was thinking of just reinforcing the rivet holes with CA glue. That ought to do the trick for a few flights at least. If you are really worried about it put on another layer of something (paper, self-stick label paper), cut the hole and ca all of that. By the time they elongate you will be on to bigger and badder things.

Hope this helps.

 

[atrobinson]

Additional relevant material Seeking Hardware for Alternative Featherweight Raven 3 Recovery Retention

 

[atrobinson]

If anybody's out there:

1. Best technique for reinforcing balsa w/ CA?

2. Is it OK to use a small palm sander or random orbit sander on balsa?

 

[fyrwrxz]

If anybody's out there:

1. Best technique for reinforcing balsa w/ CA?

2. Is it OK to use a small palm sander or random orbit sander on balsa?

Yep- I'm here (he says with refrains of Pink Floyd ringing in his mind)
1) just flood the fin surface slowly and carefully with thin CA-it will wick into the grain. Not a fan of this personally, I'd paper the fins with white glue but, YMMV
2) Like using a shotgun to kill mosquitoes. A bit tedious but all you want to do is knock down the raised grain from the CA-then primer for smoothness. You don't want to blow thru the reinforced grains. 200-400 grit on a sanding block (uh- piece of wood) You can actually use a large eraser and thumbtack your paper to it. It has a bit of give, yet yields a flat surface on plane with a little care. Circular motion (oh wow-there's Frank Zappa again...)

 

[atrobinson]

Yep- I'm here (he says with refrains of Pink Floyd ringing in his mind)

Just nod if you can hear me...

Pouring CA onto balsa I can do. Using paper and white glue have always had tragic results since kindergarten.

You saved me $40 or whatever, but in some ways it's disappointing: someone really needs to invent an automated fin sander ;-)

Thanks, very helpful information!

 

[atrobinson]

So, fins... I don't like balsa. I remember this from 30+ years ago when I was building Centuri kits (never Estes; I hated Estes; Except Der Red Maxx). I didn't like attaching them. I didn't like finishing them. I didn't like painting them. Still don't.

But, one _advantage_ of age is more patience and perhaps finer motor skills, because I am a good 20% of the way to competence in dealing with surface mount balsa fins.

I painted on two coats of thin CA which appear to have increased the fin strength by over 50% (based on static tests performed on scrap balsa). I then tried a coat of sanding sealer. ERROR! Maybe after a few attempts I'll get it right, but this stuff comes in a spray bottle and goes on with bubbles. The cured surface is not at all uniform as advertised. So I tried something I used to fill body tube spirals: Elmer's wood filler mixed with water and painted on. This works fairly well and after lots of fiddling and sanding with 220, 400, and 600 grain sandpaper, leaves a nice sheen. At least in some places

The fins before finishing weight .811 oz collectively. They now weigh 1.05oz collectively, so my finishing process added almost 30% to the weight of the fins. But they ARE much stronger.

I've been spoiled over my past three projects by through-the-wall fins. I haven't put on surface mount fins since 1983+/-, and I never did it well. The were never properly aligned with the roots parallel to the body tube and projecting at a right angle to the body tube. Let's say all my rockets had a built-in roll tendency, although sometimes my fin alignments canceled each other out and the rocket flew straight--accidentally, I assure you.

This time I used 5 minute epoxy rather than Elmer's white glue. After some frustration getting the first fin lined up the way I wanted, leaving some epoxy on the body tube and fin (most of which I wiped away with an alcohol wipe--I'm learning), the other two went fairly easily. They are aligned within a fraction of a degree of parallel, and within a few degrees of 120 degrees of each other ;-) The 5 minute epoxy is WAY better than Elmer's. After two or three minutes the fins will stick in the position I put them against their own weight and gravity--and after five (as advertised) they're solid enough to support weight but still malleable enough that I can move them slightly to correct their alignment (angle) with respect to each other.

I'll take some pictures in a bit. I can't see it's a clean or pretty job, but it's better than I used to do as a teenager, and that's saying something anyway.

 

[atrobinson]

PS - I did use a small palm sander I found in my tool box and it works pretty well--but you have to use a very light touch.

 

[atrobinson]

Here are some pictures of the fin filleting process. I used this filleting process on my Strong ARM where I messed up the through-the-wall mounting. The Strong ARM fins were held in place by epoxy and my extra-special epoxy clay fillets. They are very strong. How strong? The fins (unlike almost everything else) survived a 67m free fall of a 4-pound aerodynamic projectile. When I was trying to salvage the fins from the aft body tube, the 3 of 4 fins broke before the epoxy clay fillet broke.

As I said before, the fins are not quite 120 degrees apart--close but not exact (I don't have a fin jig). The fins look a little motley because I tried three or four different finishing and reinforcement techniques, but I'm actually pretty happy with the finished (so to speak) product. A very smooth finish with no rough spots or exposed grain.

Photo 12: Shows the fin assembly before filleting. The fins are quite strong and the attachment point is strong. Stronger than the body tube. The finish doesn't look great here, but as I said I'm actually pretty happy. Once painted it should look good. Not perfect, but good.



Phone 13: I learned from many attempts to mask off the fillet area on the fin and body tube. I do both sides at once. The masking tape has to be firmly pressed against the surface so clay doesn't work its way underneath. Fold the tape over on itself to form tabs for easy removal.



Phone 14: This is about the right diameter for a rope of epoxy clay for the fillets on this LPR/MPR project.



Photo 15: The epoxy clay roughed in. I push the clay firmly into the fin joint but don't worry much about appearance at this point as long as coverage is continuous. There is way too much clay on this side, but that will go away soon enough.



Photo 16: The epoxy clay smoothed with a finger dipped in rubbing alcohol. I wear nitrile gloves while doing this, and they tend to stick to the putty. Keeping your finger wet with isopropyl lubricates and makes a smoother surface. In the next step I will use the sculpting tools to remove all the excess putty. The masking tape keeps the fillet contained.



Photo 17: The almost-but-not-quite finished epoxy clay fillet. Once I removed the excess with the modelling tools, I used my finger wet with rubbing alcohol again to smooth the surface and feather the clay out onto the body tube and fin. The alcohol is an epoxy solvent and makes the surface very clean and feathered out to the surfaces.



After this fillet has cured I'll sand it. If necessary I can repeat the process to build up the fillet.

 

[atrobinson]

Sorry, photo 17 was the same as photo 16.

Here is the real photo 16:



And here is a photo of a completed fin fillet:

 

[atrobinson]

The nose cone (Estes part #072305) is another problem.

The nose cone comes with a shock cord attachment point designed for LPR. There is a hole, perhaps 1/4" or 5/16", in the base of the nose cone. The nose cone weighs .898oz. With my current weight and balance I needed some more weight in the nose, so my plan was to screw a .139oz screw eye into the nose cone. This provides a better shock cord attachment point and just enough weight to offer a >1 stability margin even for F35 motors. For whatever reason I thought the hole in the base of the nose cone was either sealed or small enough to offer some retention to the screw eye, but it's not.

What I did instead was this:

1. Prepare a plug of epoxy clay about 3/4" long and the same diameter as the opening in the nose cone
2. Prepare a good dollop of 5 minute epoxy
3. Insert and remove the screw eye from the epoxy clay, leaving a hole--we'll come back to this
4. Using a small dowel inserted through the hole in the nose cone, apply a heavy coat of epoxy
5. Fill the hole in the epoxy clay plug with epoxy
6. Insert the screw eye threaded portion into the epoxy clay
7. Insert the epoxy clay plug and screw eye into the hole in the bottom of the nose cone, leaving some material outside the hole
8. From hereon in, keep the nose cone vertical with the base DOWN
9. Spread the epoxy clay around the opening and the base of the screw eye
10. Coat the visible epoxy clay with a light coat of epoxy
11. Allow to cure in the vertical (base down) position

The result was a very strong attachment point. Since I can get these parts easily from a local hobby shop, I decided to see how strong. The nose cone itself will break before the screw eye pulls lose. I wiggled, waggled, hung weights from, banged on the table, and otherwise abused this attachment point. I'm confident. Can't wait until the first launch when the nose cone comes down separately But as I said, they're easy to replace.

Photo 18 is a picture of the finished nose cone. It's not pretty, but it is highly functional.

 

[atrobinson]

This will get updated, but so far this is what I have obtained for the project (all prices in approximate 2013 US dollars):

Project-Specific Supplies
If you just want to build a more rugged Hi-Flier XL with single deployment, you can do it with these items.

1. Estes Hi-Flier XL rocket kit (~$20)
2. 24mm Rocketarium Retainer (~$16)
3. Centering rings (BT 50/BT 60, ~$4)
4. 38mm Blue Tube Coupler x 8" (~$8)
5. 1mm Kevlar cord x 30 feet (~$8)
6. 1/8" screw eyes x 2 (~$1)
7. Approximate project-specific materials cost . . . . ~$60 (!)

One-Time Purchases
These are optional, and primarily for dual deployment. You can get cheaper altimeters, but few if any that are more suited for small-diameter projects.

• Featherweight Raven 3 altimeter (~$155)
• Featherweight 38mm avionics bay (~$60)
• Archetype cable cutter (~$25)
• Aerotech RMS-24/40 Motor Hardware (~$43)
• Approximate one-time purchase cost . . . . ~$300

General Supplies
You need these things for MPR and HPR anyway.

• Very thin cyanoacrylate (CA) glue
• Fast cure (5 minute) epoxy
• Cheap, disposable 1/2" brushes
• Elmer's Wood Filler
• Wax paper
• Fixit Sculpt epoxy clay ($37 for 3 pounds--enough for MANY projects)

 

[atrobinson]

The av bay will be retained by plastic rivets (get these from Apogee among other sources). I've drilled 6 holes aligned with the fins, of which I will use two upper holes for single deployment (the entire front of the rocket is ejected by the engine charge, but I'm bringing the altimeter along to get flight data). For dual deployment, two upper and three lower holes will be riveted. One hole is left open as a static port.

Photo 20: Drilling the 5/32" holes.


Photo 21: Finishing the rivet/static port holes.

 

[atrobinson]

This shows some of the final construction steps through the first coat of primer.

I like the Krylon gray primer. You can essentially drench the rocket in paint and it will dry mostly smooth and easy to sand. Not recommending you do that, just that it's a very forgiving paint.

Photo 22A is the rocket just before the first primer coat. I've masked off the Rocketarium retainer. You can clearly see the beveled launch lug here--1/4" phenolic from Apogee.


Photo 22 is the first coat of gray primer. I used a microphone stand covered with a trash bag as a paint stand. The end of the microphone stand just fits in a 24mm motor mount--very convenient!


Photo 23 shows the end of a 1mm Kevlar shock cord for mounting on a Featherweight Raven 38mm avionics bay. This is the recommended method of shock cord attachment since you can't really drill the bay and put in an eye bolt. I prized the fibers at one end of the cord apart, fitted them around the 4-40 threaded rods, then lifted the assembly off and used CA to seal the end of the cord and strategic points before and after the "holes."


Photos 24 and 25 show the installed motor mount. I used a dowel to put 5 minute epoxy about 3" inside the aft body tube. I inserted the MMT part way into the tube, and then added some more epoxy just inside the end of the tube. I then inserted the MMT all the way until about 1/4" or less of the motor retainer was showing. Because of the permanent shock cord attachment I pulled the shock cord through the aft end of the MMT to avoid getting any epoxy on the Kevlar while gluing. I painted a heavy coat of CA on the externally facing aft centering ring as additional reinforcement.



Photo 26 is a closeup of the 1/4" launch lug. I beveled both ends using a Dremel with cutting disc, sanded, and reinforced both ends with CA.


Photo 27 shows the CA reinforcement of the tube ends. Since these are LPR tubes and I'm going to be launching with MPR motors, I reinforced 1/2" or more of both ends of each body tube with CA--closer to 1 1/2" where the avionics bay lives.


Photo 28 shows the recovery configuration for single deployment (getting a little ahead of the story, but hey...). The permanently mounted shock cord is attached to a 1/8" quick link (anyone know where I can get smaller quick links?). The 24" nylon parachute (from an Aerotech Mirage kit) on a swivel also attaches to the quick link, along with the forward shock cord. The forward shock cord is secured to the Ravel av bay. In this configuration the stability is marginal (< 1 caliber), so I attach one or two quick links to the nose cone eye bolt and tape them so they don't move around. This increase the stability to about 1.1 caliber.

 

[atrobinson]

Do not under any circumstances put your rocket in the oven to accelerate paint drying.

 

[atrobinson]

Hoping to launch the MPR-modified Hi Flier XL this week.

Priming and painting went smoothly until applying the final color, for which I used Krylon Purple. This paint is supposed to be a smooth, high-gloss paint but goes on with a pebbled surface--and it doesn't dry. Now closing in on 12 hours and the paint is still tacky.

I had a plan to paint one surface of each fin with fluorescent yellow, orange, and red paint for visual tracking--but the slow-drying purple has put me off this idea. I'll probably paint the nose cone fluorescent orange as that's my daughter's favorite color, but nothing more sophisticated than that.

The good news is that I've decided I like the pebbled finish. It's certainly not the traditional high-gloss flawless finish I was going for with my endless sealing and sanding, but it looks pretty cool. Or I may be rationalizing because I don't want to repaint the damn thing again. The pebbled surface may degrade laminar flow, or it may make the surface of the rocket like a golf ball--but in either case I don't care as long as it goes high enough to successfully deploy the parachute.

Pictures will be forthcoming once the damn paint dries and I can put the parts together!

 

[chadrog]

Very cool setup, thanks for showing!

 

[atrobinson]

Back to the Pink Floyd theme, is there anybody out there? Critiques welcomed of the techniques I used here.

Some lessons I learned:
1. 1/8" screw-eyes are probably overkill--I bought some 4-40 eye bolts for future similar projects.

2. Get a fin alignment jig--my fins are within a small tolerance of 120 degrees apart, but off enough that you can tell in two of three orientations ;-)

3. Don't use an oven to dry paint--dry heat can be used for this, but a regular oven with a minimum temperature of 170F is to confined and too hot, especially when the heating elements are active (creating radiated temperatures well in excess of 170F). I deformed my nose cone and had to buy a new one ;-(

4. I'm a big fan of Krylon gray primer, but not the other Krylon paints--the white primer is OK but not as good as the gray, and the gloss paints are terrible (or at least hard to use and long to dry). There are some exceptions--Krylon gloss black is easy to work with.

(3) and (4) are not related, even though they seem like they should be.

Otherwise, I think I did pretty well in terms of technique, but I'm always happy to hear of a better way or constructive criticism.

Andy