Estes Argent Dual Deploy - build thread

[dward]

I saw one go up this weekend but failed to meet up with the owner to get the lowdown on his mods. I have never done DD and thought it could be fun to try on my new Argent. Here are the parts for reference. The upper tube is 50 mm OD/49.2 mm ID, and is the tube I figured the ebay would be installed. The extra BT-55 and coupler (non-white and red) are not stock and is for a baffle. Ideas?

 

[dward]

Thinking it over, maybe the best way would be to use the coupler on the fin can. Might have to buy another coupler and scrap a little from the 2nd 2.5 " tube to fuse the two couplers together. A 12" nylon drogue in the fin can would probably fit, even with the baffle I am putting in. Will have to take some measurements, but that seems like the way to go. The downside is that it adds a lot of weight on the wrong end of the rocket.

 

[chadrog]

My first instinct would be to go traditional, make the transition your av bay.

 

[Handeman]

I would tend to agree with that, except the air flow over port holes wouldn't be very smooth at or below the transition. You could put the ports a inch above the start of the transition, but that is a more difficult build.

Using the coupler on the fin can can work, it depends on where your CP is at. You might need to make the fins bigger to lower the CP so the CG stays far enough ahead of it.

You really might want to try a different kit as your first DD, like the LOC Vulcanite and the 2.14" electronics bay

 

[dward]

I just changed this to a build thread. Details to follow, but I took chadrog's advice and decided to use the transition for the AV bay.

 

[gsquared]

Did you buy your electronics yet? If not, you could use an accelerometer-based computer for apogee deployment. Then you don't have to worry about airflow. You would still use barometric pressure for main deployment, but airflow past the transition won't be an issue then. Gwiz and picoalt have such units available. I have one of each

 

[WillMarchant]

These are awfully small rockets for a first dual-deploy effort. I'm not saying someone can't do it. But a 4" rocket is a whole heck of a lot easier to wire up. And I suspect that that will make for a more reliable venture into electronic deployment. But only the flier really understands their own skill and comfort level...

 

[Handeman]

These are awfully small rockets for a first dual-deploy effort. I'm not saying someone can't do it. But a 4" rocket is a whole heck of a lot easier to wire up. And I suspect that that will make for a more reliable venture into electronic deployment. But only the flier really understands their own skill and comfort level...

Good point Will. I completely agree. I've done DD with 2.25", 3", and 4" OD and the 4" is definitely the easiest. I understand wanting to do DD with smaller rockets, I used the 2.25 with DD for my L1 cert, but depending on the field and weather conditions, it doesn't provide much benefit below 2,000 to 3,000 feet. Now I've seen DD setup on 29mm minimum diameter rockets so it can be done, but as Will said, only the flier really understands their own skill and comfort level...

 

[chadrog]

The only thing more difficult is fitting the needed components into a smaller place. If it crashes for some reason, you're only out a little rocket, not a big one. I say give it a shot. Being your first DD setup, I would suggest using motor backup for your apogee event, with a decent sized drogue chute just in case you have issues wit your main event.

 

[Handeman]

I understand where chadrog is coming from, but I don't necessarily agree. If you do sufficient ground testing of the altimeter and the charge sizes, you should get to know your altimeter pretty well. You should also be confident in the charge sizes for drogue and main. I would highly recommend testing the altimeter and the matches you plan to use be drawing a vacuum on the av-bay to simulate a flight. It is usually easier to test the sizes of ejection charges by using a 12V controller, or even just toughing the match leads to a battery. Once you've done all that, I would recommend testing the whole system with the right size charges and test by drawing a vacuum on the av-bay.

Once you've done all that, then decide if you still want to use motor eject that might go early, or a large drogue that can drift much further then a small one.

 

[dward]

Did you buy your electronics yet? If not, you could use an accelerometer-based computer for apogee deployment. Then you don't have to worry about airflow. You would still use barometric pressure for main deployment, but airflow past the transition won't be an issue then. Gwiz and picoalt have such units available. I have one of each

Yes, already bought the electronics. I got the Entacore AIM. It has a peak velocity ejection option, but I'll have to go into the software to see what options are available.

 

[dward]

The only thing more difficult is fitting the needed components into a smaller place. If it crashes for some reason, you're only out a little rocket, not a big one. I say give it a shot. Being your first DD setup, I would suggest using motor backup for your apogee event, with a decent sized drogue chute just in case you have issues wit your main event.

My thinking exactly. I am using motor backup for the drogue. Any size suggestions? I think the main is 24", but I'd have to double check.

 

[dward]

I understand where chadrog is coming from, but I don't necessarily agree. If you do sufficient ground testing of the altimeter and the charge sizes, you should get to know your altimeter pretty well. You should also be confident in the charge sizes for drogue and main. I would highly recommend testing the altimeter and the matches you plan to use be drawing a vacuum on the av-bay to simulate a flight. It is usually easier to test the sizes of ejection charges by using a 12V controller, or even just toughing the match leads to a battery. Once you've done all that, I would recommend testing the whole system with the right size charges and test by drawing a vacuum on the av-bay.

Once you've done all that, then decide if you still want to use motor eject that might go early, or a large drogue that can drift much further then a small one.

I tested the altimeter when I got it. First test was with christmas lights and then with Quest igniters. I also pulled a vacuum on the sensor to simulate. I have not tested the charges yet, but soon. I'm not sure how to safely simulate launch with live charges. Maybe a shop vac??? I'm sure as hell not going to stick my face over the vent holes and suck!!! I suspect if I did and told someone, I might be up for an ignoble prize. Seriously, though, if you can point out a thread with details on full simulated launch tests of an altimeter, I would appreciate it.

 

[chadrog]

Yes, already bought the electronics. I got the Entacore AIM. It has a peak velocity ejection option, but I'll have to go into the software to see what options are available.

Great choice! I have an AIM USB one and two, great units with awesome features. If you put you're vent holes in the upper air frame above the transition, you should have no issue using the baro function.

 

[chadrog]

I tested the altimeter when I got it. First test was with christmas lights and then with Quest igniters. I also pulled a vacuum on the sensor to simulate. I have not tested the charges yet, but soon. I'm not sure how to safely simulate launch with live charges. Maybe a shop vac??? I'm sure as hell not going to stick my face over the vent holes and suck!!! I suspect if I did and told someone, I might be up for an ignoble prize. Seriously, though, if you can point out a thread with details on full simulated launch tests of an altimeter, I would appreciate it.

I've done this with 1/4" aquarium tubing taped into a vent hole, with the other holes covered with tape. It's cheap at pet shops, and is (usually) sold by the foot. Twenty feet should do it.

 

[dward]

I am way behind on my build threads, so I better get to it.

Summary of build thread:

1. Unpacking
2. AV Bay Construction
3. AV Bay Electronics
4. AV Bay Hardware
5. Motor Mount Assembly and Motor Ejection Baffle
6. Fins
7. Filling and Surface Preparation
8. Assembling the Fin Can
9. Fin Fillets
10. Attaching the Eye Bolt to the Nose
11. Drilling Holes
12. Priming and some minor tweaks
13. Painting
14. Launch Preparation
15. Maiden Flight

The unpacking step is listed at the top of the thread.

 

[dward]

My first solution involved putting the AV bay ahead of the transition. I made a bay from 2" body tube. There were several problems. First, the bay was too tight. There was no way the electronics, a battery, wiring harnesses, etc were going to fit. So I have a nice payload bay for a 2" rocket now. I discussed the problem at a local CMASS meeting and decided to go with the way chadrog recommended, making the transition the AV bay. So here we go.

Parts:

• 4" of 2" body tube (Estes part # 030615)
• 4" of 2.5" body tube (Estes part # 031390)
• 2.5" tube coupler (Estes part #030189)
• 2" tube coupler (Estes part #030618)
• 2"-2.5" plastic transition (Estes part #072657)
  
• 2 pieces of 12 " long 5/16"-18 all thread
• 2 1/4" eye bolts with nuts

Supplies/Tools:

• 1/4" thick Birch plywood
• Jig saw with scrolling blade
• 100 grit sandpaper
• Dremel with cutting wheel
• 3/8" and 1/4" Drill bit
• Createx black paint
• Carpenter's Wood Glue

1. Assemble and glue the AV bay chassis
I used West Systems epoxy with the 206 slow hardener. A 4" section of both 2" and 2.5" body tube are first glued onto the transition. Next the tube couplers are inserted 2" into their respective tubes. The completed chassis looks like this:



2. Make the bulkheads for the AV bay
I used the tube couplers as a template for the bulkhead components. This step involves four circular disks to be cut from the birch plywood. The first two disks have an outer diameter equal to that of the 2" and 2.5" tube coupler outer diameters such that they will fit snugly inside the 2" and 2.5" body tubes. The last two disks have slightly smaller diameters such that they fit snugly inside the tube couplers themselves. I also cut an extra of each of these last two disks to be used later. Once the disks were cut, I sanded them to fit. It was a lot of sanding.


3. Determine width of sled
Since I already had the Entacore AIM 3.0 altimeter and a 9 volt battery I could test fit them into the chassis to determine how low the sled needs to fit. I then measured the width at that point.

4. Cut sled from birch plywood
First thing, I laid down masking tape on top of the plywood roughly where my cuts would be. I traced out 2" at ~2.5" wide followed by a 2" void and finally a 2" section ~2" wide. I sketched them from a centerline so that they would be centered. I then used a ruler to trace two connecting lines between the two dissimilar sections. I then cut out the pattern.


5. Cut sled feet from extra disks from step 2
I determined where to cut the disks by test fitting the sled into the chassis.

6. Determine the position of the all thread and drill holes in the sled feet
This was a pain since not all of my hardware had arrived yet, so I had to make some educated guesses about the sizes of the charge bays and terminal blocks. I already knew roughly where they would be located from the sled position but it was a matter of determining how far each rod would be from one another. Since I was using 5/16" all thread, I drilled with a 3/8" drill bit. Why 5/16" you ask? Well, it was a stupid decision. I wasn't aware that 1/4"-20 was the standard. After drilling, I removed the bottom portion of the hole with a dremel.

7. Glue sled feet onto sled
I used Carpenter's Wood Glue for this. Positioning was mostly guess work.



8. Glue bulkhead pairs together
I applied Carpenter's Wood Glue in between the two pieces and got the centering by coupling them into the two tube sizes they should fit into. So for the first pair that would be the 2" tube coupler and 2" body tube. I did the same with the other pair except I used the 2.5" tube coupler and body tube.

The almost completed chassis is shown below (holes not yet drilled in bulkhead).


8. Mark the bulkheads for all thread holes
I dipped the ends of the all thread into some Createx black paint. While wet I slid the sled with all thread into the AV bay chassis and pushed in a bulkhead one at a time to mark them for holes.

10. Drill the holes marked in step 9
I again used a 3/8" drill bit.

11. Mark the center of each bulkhead and drill hole for the eye bolts
Use your favorite technique to find the center. I like to use a pin and balance it. Since the eye bolts are 1/4-20, I used a 1/4" bit for a tight fit.

12. Attach eye bolts and epoxy
Applied a liberal amount of West Systems epoxy with the 206 hardener on the outside and inside of the bulkhead.

 

[dward]

Parts

• Entacore AIM USB Rocket Altimeter
• 9V battery
• 9V battery connector
• AV Bay sled
• rotary switch
• mini-clamp set
• 4 position female interlocking connector
• 4 position male interlocking connector
• 4 nylon standoffs and screws

Tools/Supplies

• Small flat head screwdriver
• 1/4" thick birch plywoood
• 4-40 tap
• #43 drill bit
• Loctite 5 minute epoxy
• Mini USB to USB adapter
• Computer running windows
• Christmas lights

1. Mark AV sled for holes
The mounting holes are 50 mm apart and I basically centered them on the sled.

2. Drill and tap holes for nylon standoffs
I used the #41 drill bit and the 4-40 tap.

3. Attach nylon stand offs.

4. Cut walls and backing for 9V battery casing
Just a couple of 1" x 1/2 " rectangles of birch plywood and another 1/2" x 1/2" piece. (see pic below)

5. Attach battery casing walls
I just used the battery itself as a positioning guide and secured them with loctite 5 minute epoxy. Care must be taken not to get epoxy on the battery.

6. Attach altimeter to standoffs
Used the nylon screws that came with the standoffs. Had no use for the nuts.

7. Install battery and switch and wire to altimeter with 24 gauge wire
I attached the 9V battery connector to the battery, laid it in the casing on the sled and secured it with a rubber band. I then wired it to the mini clamp set, rotary switch, and altimeter (see diagram below). I soldered the wires to the rotary switch, but apparently there is a solder-less method as well.


8. Wire the igniter leads to a 4 position female interlocking connector with 18 gauge wire
These are the same connectors you see inside computers. The mini clamps won't take 18 gauge wire, which is why I chose these connectors. (see diagram below)

Here is the wiring diagram


and the finished product (note, I later removed the through-sled wiring and just kept it loose so I could easily remove the altimeter for another rocket).


9. Perform power on test
Just to listen for beeps. I also did a simulated launch with a straw over the pressure sensor to verify launch detection (beeps) and igniter wire firing (christmas lights).

10. Connect to computer and test fire igniter wire leads
Fortunately I had a mini usb to usb cable from a failed 808 camera. The software can be downloaded from the Entacore website (link above), but it only runs on windows, so I installed it on one of my wife's old laptops (vista, I think). All tests were satisfactory. I also emulated a launch using one of the sample data files provided with the software download.

Sample screenshots from the Entacore website:

 

[dward]

Parts

• Wired rotarty switch
• Terminal block
• 2 Charge wells
• 2 pieces of 12 " long 5/16"-18 all thread, 2 nuts, and 2 washers
• 4 position male interlocking connector
• AV bay chassis
  
• AV bay bulkheads

Tools/Supplies

• 18 gauge wire (red and black)
• 3/64" and 1/16" drill bit
• Loctite 5 minute epoxy
• Hobby knife
• 1/2" spade drill bit

1. Cut two terminal blocks, each accommodating two wires
I had big strips that had 12 connections, so I had two cut off what I needed. The terminal block that will go on the 2" end of the AV bay needed to be trimmed at the corners to fit. A hobby knife handled the plastic fine.

2. Drill hole through center of charge wells with 1/16" drill bit
It doesn't have to be exact, and it wasn't.

3. Dry fit the terminal block and charge well and mark their positions on the 2" and 2.5" bulkhead
I put the all threads with nuts and washers on to find the proper positions. I marked the bulkhead through the hole in the center of the charge well rather than tracing around the circumference of the well. I also marked the position for the wires to pass through the bulkhead.

4. Drill hole for charge well attachment with 1/16" bit in both bulkheads

5. Drill holes for 18 gauge wires with 3/64" bit in both bulkheads
The charts I have suggest using a #56 drill bit for 18 gauge wires, but I found this too tight so I used a 3/64" bit instead.

6. Run one red and one black 18 gauge wire through each bulkhead
I used about a foot and a half of the wire for the 2" bulkhead and 6" for the 2.5" bulkhead.

7. Attach wires to the terminal blocks
Stripped them first, of course.

8. Attach all threads to the 2" bulkhead
I used lock washers and bolts.

9. Secure bulkhead hardware with 5 minute epoxy
I did the charge well first, placing a layer on the bottom of the well and inserting the bolt through the bulkhead and securing with nut from the other side. I placed a little epoxy on the nut and inside the charge well over the bolt. Next, I put a layer of epoxy on the bottom of the terminal block and moved it into position, pulling the slack in the wires from the other side. Once in position, I applied more epoxy where the wires pass through the bulkhead on both sides. Finally, I put epoxy on the all thread nuts and around the all thread on the inside of the 2" bulkhead since they will be permanently attached to this one. I applied a little epoxy around the eye bolts at this time, too.

picture prior to applying epoxy to threads:


10. Drill 1/2" hole for rotary switch in 2" body tube section of AV bay
The position around the circumference is arbitrary and I chose to make it centered with the 2" body tube along the axis of the tube. I used a 1/2 spade drill bit instead of a regular bit.


11. Attach rotary switch
This was tricky since it is only a two inch diameter tube and you have 2" of tube coupler and 1" of tube to get through to put on the nut. The wires actually help to guide the nut into place. I used a long screwdriver to push the nut around. Once tight (sorta tight) I put a little epoxy on the nut to keep it in place.

12. Insert 2" bulkhead into AV bay and connect wires from both bulkheads to a 4 position male interlocking connector
I used the wiring diagram in step 3 as a guide for the connector.

picture before attaching the 4 position male interlocking connector:

 

[Handeman]

Everything is looking good. You're doing a great job.

The only thing I would do different is, I think you really over did it with the all thread in the av-bay, 5/16"? I think 1/4" would have been too much. You will have about a 3 lb rocket. 3/16" would have been plenty and 1/8" would have been sufficient. If you size your charges correctly, use a drogue chute to keep the main above the fin can to avoid a huge shock when it reaches the end of the cord after main deployment, the biggest shock on the system would be the main opening and the weight of the rest of the rocket hitting the ends of the shock cord. The only time that should be large enough where a pair of 1/8" rods wouldn't be enough is if the drogue never deployed and the main did deploy while the rocket was coming in ballistic. Even if that did happen, I would expect the main to shread, BTs to zipper and other damage before I would expect a pair of 1/8" all thread to fail on a 3 lb rocket.

I say all that because I did the same thing. I do hope someone reads this and doesn't make my mistake. I used very large all thread on my L1 cert rocket. By the time I built my L2 cert rocket, I use smaller all thread on that one then the L1, even though it weighs three times as much. Just something to consider for your next build.

 

[dward]

I say all that because I did the same thing. I do hope someone reads this and doesn't make my mistake. I used very large all thread on my L1 cert rocket. By the time I built my L2 cert rocket, I use smaller all thread on that one then the L1, even though it weighs three times as much. Just something to consider for your next build.

glad to hear I'm not alone on this. I took it to a CMASS meeting and they said as much. Next time I'll know better.

 

[Handeman]

glad to hear I'm not alone on this. I took it to a CMASS meeting and they said as much. Next time I'll know better.

Yes, and next time you'll be able to pass your wisdom on to the next guy that over builds.....

I made a lot of poor choices when scratch building my L1, but despite the pitfalls, it still turned out to be a great rocket that I flew a lot. I used it for my L1 cert, but the cert and the next 6 flights were all with I motors. I finally put a H motor in it just because it hadn't flown on one yet. My plan was to scratch build my L1 with DD and learn as much as I could. I guess that is why I ended up liking that rocket so much, I learned more building and flying that rocket then any I ever did before or since.

Hope your's works out as well as mine did.

 

[patelldp]

I've recently taken to using aluminum all-thread. My 3" Performance Rocketry Intimidator 3 (a 12# rocket when loaded) uses 2x 10-32 aluminum pieces of all-thread on its altimeter bay. These have flown twice now without any evidence of any issues.

 

[dward]

Motor Mount Assembly

Parts

• Argent motor tube
• 6" of BT-55
• Estes large red tube couple (#030175-5)
• 1/4" eye bolt, nut, and washer

Tools/Supplies

• 1/4" Birch plywood
• thin CA (Bob Smith)
• 3/8", 1/4" drill bit
• aluminum angle
• BT-55 tube cutting guide
• 100 grit sandpaper
• 1" spade bit
• Dremel with sanding drum (rough grit)
• West Systems epoxy with 205 and 206 hardeners
• Loctite 5-minute epoxy
• hobby knife
• West Systems Colloidal Silica (406)

1. Dry fit centering rings on motor tube and tack down forward two with CA
The aft ring(not shown in picture) is about 1/2 inch (just enough room for the motor retention system to mount) from the back. The next fin is the length of the fin tabs away from the first. The forward most ring is 1/2" from the top. Apply a small amount of CA to the joints on the two forward centering rings. I am leaving the aft ring off until the fins are mounted so that I can apply internal fillets. This rocket doesn't really need it, but I am practicing the technique for my L1 build (Super DX3). The CA is just to keep the rings in place while dry fitting and moving the mount around.



NOTE: I should have sanded the glassine off the motor tube where the centering rings go, but I didn't for some reason. Maybe I did, but from the pics, it doesn't look like it.

2. Fit BT-50 onto top of motor mount tube with red tube coupler and mark for length and cut
The size of the fin can is really the limit as to how long the motor mount can be extended. I cut it at about six inches. The BT-55 is 32 mm and the motor tube is 29 mm (ID), so the coupler is needed to make it fit. It fits inside the BT-55 and outside the motor tube. It's not a tight fit, but with some epoxy it'll work.


3. Cut 2.5" diameter baffle from birch plywood and drill 8 holes uniformly around the perimeter and one hole in center with 3/8" and 1/4" bits, respectively
I cut this with a jig saw with a scrolling blade. Considerable sanding is required to make a clean snug fit inside the 2.5" body tube.


Please don't give me any crap about the non-forged eye bolt. Yes, I have heard they will bend open in time.

4. Cover the baffle with epoxy and attach eye bolt
I used 5-minute epoxy for this. Also put a little epoxy around the threads after the eye bolt was attached.

Where I'm going with this is a baffle system I am stealing from my US Rockets 2.25" V2. Here is a picture of that baffle system:


5. Cut two symmetric 1/2" x 1" slots into the BT-55 an inch from one end
Will look like the V2 picture above. I cut it with a hobby knife and use a BT-55 tube cutting guide and aluminum angle to mark the slots.

6. Seal top of BT-55 with epoxy and drill hole
This step is required because the fit was just too close and if the BT-55 hangs over any of the holes, the whole purpose of the baffle is defeated. I used the west systems with the fast hardener (205). I also smeared some epoxy on the inside of the tube to protect from ejection particles. Here is the result:


I did this by setting the tube on a piece of wax paper and pouring some west systems epoxy into the tube with a large plastic syringe through the slots. After it cured, I cleaned up the outside edges with 100 grit sandpaper. Here it is after drilling with a 1" spade bit and sanded with a dremel sanding drum. The baffle I cut earlier will sit right on top of this.


I dry fit the whole assembly at this point to make sure the filler was good.


7. Put two small screw eyes in the remaining centering ring
This is so that I can remove it from the body tube if necessary during installation. Once the ring is seated properly, I will remove these screw eyes and seal up the holes.


8. Attach BT-55 and apply fillets to the centering rings
I mixed up some west systems with the slow hardener. I applied a light layer of epoxy without filler on all joints discussed below before mixing in about 30% by volume colloidal silica (406). I smeared some outside the top of the motor tube (liberally) and inside the BT-55. Pushed the red coupler into the BT-55 and then over the motor mount tube. I then applied fillets on both sides of the forward most centering ring and on the side facing the top on the second centering ring to avoid interfering with the fin seating later. Though I didn't put the epoxy with filler on the fin-side of this CR, I did apply some unfilled epoxy here. I let cure overnight.

 

[dward]

Fins
Parts:

• 3x Argent fins

Tools/Supplies:

• Masking tape
• Sanding block (100 grit)
• 3M sanding sponge (150 grit)

My plan is to just round the leading and trailing fin edge. These fins would take a nice airfoil, but I just couldn't bring myself to do the work.

1. Tape off fins
Since this is not an airfoil, I just taped off leaving about a quarter of an inch from both fin edges.


2. Sand each fin one edge and one side at a time
The reason for only one edge at a time is so that each fin can be made identical. I started by sanding one side of the leading edge on each fin with a 100 grit sanding block. When all fins were done, I lined them up to compare and made adjustments as necessary.

Then I moved on to the trailing edge, same side of each fin.

3. Sand the other side, forming a 'V'
Same procedure as before, but on the other side, comparing when done and making tweaks to get uniformity.


4. Round edges with 150 grit foam sanding sponge
Now that all edges have a 'V' sanded into them, I just rake back and forth over the edge to round it out. The 3M sanding sponges work well for this until you get a tear in the surface and then it starts hanging a bit.

 

[nute]

That looks great!
I could never get that uniform of a bevel. Congrats!

 

[dward]

Filling

Parts:

• Argent body tubes
• Argent Nose
• AV bay
• Fins

Tools/Supplies:

• Bondo Glazing and Spot Putty
• Minwax Polycrylic
• Foam staining brush
• 3M 150 grit sanding sponge
• 320 grit sand paper

1. Fill tube spirals with glazing and spot putty
I find this stuff much easier to apply than the Fix-it epoxy clay. The results are comparable, but the glazing and spot putty is just easier. By the way, I have no idea what the difference is between professional and regular glazing and spot putty.
Here is a side-by-side comparison with my Leviathan. The gray filler is the epoxy clay, and the red is the glazing and spot putty.


This stuff dries very fast, whereas the epoxy clay takes at least 12 hours before a second coat can be applied (24 hours for full cure). As far as technique goes, I apply a bead to my index finger and press it into the spiral, dragging along, and wipe up excess with my middle finger as I go. The downside to the quick set time is that if you don't clean up your excess immediately then you will have to sand it off later.


2. Fill in gaps in AV bay
I actually think the epoxy clay would have done a better job for filling the large gaps than the glazing and spot putty since it is more easily shaped--it is clay after all.


3. Sand and fill grooves in nose cone
The grooves are the casting marks, and the glazing and spot putty fills them beautifully. Sorry, no pics.

4. Let dry and sand
The sanding sponge works nicely conforming around the body tube.


5. Apply sanding sealer to fins
I think from now on, I'll save this step until the fins are on the can. You want a rough surface where the fin fillets will go, so you have to be careful to not apply sanding sealer there. It would be easier to just wait until the fins are on the can and the fin fillets are done. Hit this with several coats of the water based sealer. Sanding with 320 grit between coats.

 

[dward]

Installing the Fins

Parts:

• Argent pre-slotted body tube
• Motor mount assembly
• Ejection baffle
• 3x Argent fins

Tools/Supplies:

• West Systems epoxy with 206 (slow) hardener
• West Systems 406 colloidal silica
• Poster board (Staples)
• Fin template
• Rubber cement
• Hobby knife
• Rubber bands
• Great planes paint mixing cups
• Long wooden dowel
• Denatured alcohol

1. Construct fin alignment guide
Read my blog (https://rockets.davidward.org/Tools/Entries/2013/9/29_Fin_Guide_Tool.html) on this tool from payload bay. After printing it out, I paste it onto a piece of poster board with rubber cement and cut with a hobby knife. I have yet to try this technique on a small rocket, but it works beautifully on larger ones.

2. Dry fit everything including fin alignment guide
It's best to make sure your plan is going to work before mixing up the epoxy.


3. Mix up epoxy
No fillers yet. I use these paint mixing cups from great planes. I rarely need as much epoxy as is dispensed by the West Systems mini-pumps. The mixing cups are graduated and I can measure out the 5-1 mixing ratio of epoxy to hardener manually for a smaller batch. After mixed thoroughly, I separate into two batches. One I will add filler to and the other is without filler. The filler is 30% by volume 406 colloidal silica. This will be used for the internal fillets to prevent running.


4. Apply a bead of unfilled epoxy in the positions for the forward two centering rings
Remember, I am leaving off the aft CR so that I can apply internal fillets. A long wooden dowel gets the job done. Positioning is mostly eyeballing and not precise measurement. Here is a pic from the same step on my Leviathan.


5. Insert motor tube assembly

6. Apply epoxy to fin tabs and fin portion in contact with body tube exterior

7. Apply internal fillets with colloidal silica epoxy
The long wooden dowel from before works well here.

It's not pretty in there, but it gets the job done.

8. Mix up JB Weld for motor retention system
Scuff up the inside of the male portion of the retainer and have everything standing by. The JB Weld is used due to its temperature resistance.


9. Apply a bead of epoxy for aft CR and insert CR
Once the fit is good, I removed the temporary screw eyes (See previous post) and filled in the holes with epoxy.

10. Apply colloidal silica epoxy fillet to aft CR

11. Apply JB Weld to end of motor tube and interior of male motor retention ring and insert onto end of motor tube
This stuff is messy. After adding the retention ring, I gave a spin to ensure good surface coverage with the JB Weld. Wipe away excess with paper towel soaked in alcohol. Alcohol is good for epoxy clean up too.

12. Attach fin alignment guide and secure fins in place with rubber bands
play song on rubber bands if so desired!


13. Apply bead of epoxy for ejection baffle and insert ejection baffle
Also, applied epoxy directly to the sides and bottom of the baffle itself. Once the baffle was in, I applied an epoxy fillet.


14. Let cure 24 hours

 

[dward]

Fin Fillets

Part 1

First a quick comparison with my undocumented Leviathan build. For that, I used Fix-It Epoxy clay. Basically you roll out (like dough) these long strands of the clay and lay them into the joint between body tube and fin.


Press them in hard, wetting your finger so as to keep a smooth surface. After about an hour you can start to shape it. Wet finger and rub to desired shape. Maybe if you were really gifted in crafts class--the ashtray I made looked like a crashed flying saucer--this would be easier than it was for me. After 24 hours, it's hardened and you're ready to start the sanding phase. I used a sanding dowel and this was less painless than I thought it would be, but it still took a good bit of time. Finally, I filled in the low spots with Carpenter's Wood Filler Max and sanded again. For me, the hardest part was rolling out the snakes and shaping the clay. Here's a pic of my V2 fin fillets after applying a bead of the epoxy clay. The V2 wasn't so bad, because it was a smaller rocket. However, the weak spot for me is the leading and trailing edge of the fin.

Here are some pics of the Leviathan's fin fillets (post painting):


I'm not saying they look terrible, but they definitely have that hand-crafted look, though it's a damn sight better than that ashtray I made in the sixth grade. After the Leviathan, I was looking for an alternative way. I ran across Sky Pirate's website and will be replicating, to the best of my abilities, his filleting technique. I wonder if he's on TRF? If you don't know this website, then definitely check it out, it's full of good stuff. Here's some of his work from his website ((c)2002 Sky Pirate):
View attachment 151308

Again, his full technique is illustrated and detailed at https://www.skypirate.net/rocketry/con_fil_01.htm

 

[dward]

Fin Fillets

Part 2

Parts:

• Completed Fin Can

Tools/Supplies:

• West Systems 105 System
  
  • 105 Epoxy Resin
  • 206 Slow Hardener
  • 403 Micro Fibers
• Phenolic Microbaloons
• 3/8" wood dowel (~1/2 " long)
• Bondo Spot and Glazing Putty
• Masking tape
• 3/8" Sanding dowel (180 and 320 grit)
• 320 grit 3M Sanding Sponge
• Pencil lead
• Denatured Alcohol
• Paper Towels

1. Layout the epoxy system


Just out of curiosity, has anyone tried the 209 extra slow hardener?

2. Mark the fillet line
The Sky Pirate technique utilizes a piece of dowel or pipe rather than a popcycle stick because the pipe gives you more control over shaping the leading and trailing edge. Now you see why I am trying this technique. If not, reread part 1 of this post.
Warning: I think I made a poor choice with the 3/8" dowel and should have gone with the 1/2" Schedule 40 pipe instead, or at least I should have gone to the hardware store for some alternatives. The reason why will be shown shortly. Here is a comparison of the two, but at the time, I thought the dowel was a better fit for the desired curvature of the fillet. Note, the outside diameter of 1/2" Schedule 40 pipe is 7/8" or 21.336 mm.

The reason for cutting the piece so short is explained on Sky Pirates website. It should be a little longer than the diameter of the pipe. The argument is basically trial and error. Longer pieces drag to much of the epoxy along and make ruts.

I rubbed the outside of the dowel with pencil so that it will rub off easily onto the rocket. I then ran the dowel along the joints of the fin to make tape marks.


The outer marks are marks made by the 1/2" Schedule 40 pipe. The schedule 40 just looks too large for a 2.5" body tube. It would probably be perfect for a 4" tube.

3. Wax the dowel
Cleaned off the pencil lead and rubbed the circumference in automotive wax (Megars I think. I'll never wax my car again, what a pain. Still have wax streaks in some places).

4. Apply tape along the marks on both body tube and fins
I found it difficult to tape in a curve with the masking tape so I used some leftover pinstriping.


5. Mix up epoxy
I find the mini-pumps dispense more epoxy than I need, so I use these great planes paint mixing cups to do the 5-1 mix of resin to hardener.


6. Apply a light layer of epoxy to the fin fillet region
I smeared it in with a gloved finger (remember, nitrile not latex for epoxy).

7. Mix filler's into epoxy
As recommended by Sky Pirate, I added the microfibers first and then mixed in the phenolic microballoons. I used the recommended 30%-30%-%40 epoxy-microfibers-microballoons recommendation, but I think 33-33-33 would have been fine.

Sky Pirate mentions using colloidal silica as an alternative, but I can see his point about sandability as I used this for the internal fillets. Also, the red color makes it easy too see the fillet and any imperfections in it.

8. Pour epoxy pudding into joints and remove excess with finger
This is a slight deviation from Sky Pirate, but I found using the dowel first resulted in a big mess.

9. Smooth fillet with dowel
Have a little alcohol and paper towels standing by to clean the dowel. The first pass will be messy, and you know you're almost done when the dowel slides through the joint with very little build up. Here is a link to the illustration gif from Sky Pirates website ((c)2002 sky pirate):

I found that it didn't really matter wether I started front to back or vice-versa. He may be able to do it all in one pass, but I made several before it started looking good. Add more epoxy pudding as needed.



Having trouble uploading pics, so there will have to be a part 3.