Madcow 2.6" FG Nike->Deacon Build

[markg]

I picked up the $99 Madcow Nike->Deacon during Madcow's sale a couple of months ago. I have built and successfully flown two HPR 2 stage rockets. I'd consider this more of an MPR 2 stage, as I'll likely fly it on G/F motors.

Due to it's small size it will be a bit more of a challenge to get built and fly than the other two. The booster is 2.6", so no problems there. It will have an Eggtimer Quantum in the av-bay which will have redundant apogee charges. Combined with a JLCR and motor eject backup, the booster will have an easy return to earth.

The sustainer @ 29mm with a 24mm MMT is the challenging part. I plan to use a Raven 4 in the sustainer to provide the separation charge, sustainer ignition as well as apogee and main charges. There is enough room (barely) between the MMT and the BT to thread CAT5e cable for the ignition/separation charges so I won't need to deal with HEI.

Here is a .ORK file with stock components as weighed from Madcow. The one component I added is an additional stepped coupler in the booster in order to change the coupler into an AV bay. I'll also added some basic parachutes and harnesses so I could run some simulations. I'll pick the actual chute or maybe streamer when the build is complete and I have the final weight.

I am going to further modify the sustainer by adding a 2" coupler and cutting about 4" off the top of the BT. The 2" coupler will be glued into the 4" of BT to make it a standard DD. There is not much room in the nose for HED and the BT is plenty long enough that I don't have any problem chopping it down a bit. I will likely have it come down drougeless with the main in the BT aft of the the Raven, blowing the nose at apogee, but that is not set in stone yet.

I have to order a 2" coupler for the sustainer, but I figure I might as well wait for Madcow's BF sale so I can save on shipping. In the meantime I'll get started on the booster.

 

[BradMilkomeda]

Subscribed! I’m trying to figure out the sustainer too. I was pondering just using a streamer for it since it is so small.

Looking forward to how you tackle the challenges.

 

[Fattbank64]

Subscribed.

I am also considering Raven 4 for the sustainer.

 

[markg]

(FWIW, as I said in 1st post, I don't have all the parts in hand for this yet. It likely won't be finished up until December)

As with all FG kits, I started this one by giving the components a bath with dish soap. Any FG part that is going to be epoxied will be sanded beforehand with fine grit sand paper, then wiped down with a rag. I use a combination of BSI 5/15 min epoxy for attaching parts. Fillets are done with West Systems 105/205/404.

Starting from the bottom up. The MMT will be mounted 5/8" in from the aft end of the booster. After adding the Aeropack retainer, this will place the back of the motor approximately level with the rear of the BT. I slid the MMT 5/8" in from the aft end and used a permanent marker to mark the end of the fin slots. This shows the location of the CRs on the MMT.

Next, I measured out some 1/2" kevlar (overkill for this rocket) that I had on hand to mount to the booster MMT. I size the length so that the top of the loop terminates just inside the booster airframe. The theory is that any wear between the harness and the airframe should be on the easily replaceable harness that is attached to the permanent one bonded to the MMT. The short MMT with this kit means that the kevlar will have to pass through the forward CR.

The kevlar is mounted to the MMT with BSI 15 min epoxy. After applying the epoxy I wrap the MMT in electrical tape (which doesn't stick to epoxy) to keep epoxy from dripping. Kevlar is mounted on opposite sides to MMT which will place it in between fin slots.



Once that dried, I used it to mark the forward CR for where to cut slots to allow the kevlar to pass through. I clamped the CR in a vise and cut the slots with a file.



The CR was secured to the MMT with BSI fillets on the top. A wrap of paper around the MMT ensures the CR is perpendicular to the MMT.



Once that was dry, I used a bit of electrical tape to cover the bottom of my slightly oversized slots and filled them from the top with epoxy.





MMT is now done and ready to be mounted in the booster. The rear CR will be glued in after I do the internal fillets. I won't be putting external fillets on the booster.

 

[MushuTheGreatStoneDragon]

Looking good so far! Excited to see where this goes.

 

[David Schwantz]

I got the Nike apache, using a Qurk in the booster and a Quantum in the nose for both ign and seperation charge.

 

[markg]

I got the Nike apache, using a Qurk in the booster and a Quantum in the nose for both ign and seperation charge.

Are you putting another altimeter in the sustainer for deployment or using motor deploy? I'm going with the Raven since a Proton won't fit. I suppose I could go with a Quantum/Quark combo in the sustainer, but the Raven will be much easier.

 

[markg]

Time to get the fins into the booster. I 3D printed a fin guide (https://www.rocketryforum.com/threads/3d-printable-component-generators.148308/). As per usual, sand the root of the fins where the epoxy will be going. I sanded the MMT before putting it in the rocket.



I used BSI 5 min epoxy on the edge of the fins to tack them in place. An elastic and the fin guide lock them in position while the epoxy sets. I surround each fin slot with masking tape, put the epoxy on the root edge of the fin and slide the fin into place. Take the masking tape off and wipe off any extra epoxy from the exterior of the fins/BT. (No picture as I was working with 5 min epoxy)

 

[markg]

After the 5 min epoxy sets, it's time for the internal fillets. To prevent epoxy from seeping out through the fin slots, I cover the fin/slot interface with masking tape. I've had epoxy leak through before and it's a real PITA to clean up.

Internal fillets are done with West Systems 105/205/404. I use disposable shot glasses and wooden stir sticks from the dollar store for my mixing. I'm using 1g of 205, 5g of 105 and then add 404 until the epoxy starts to hold it's shape. I measure the epoxy with an inexpensive 100g scale from Amazon (https://www.amazon.ca/gp/product/B06Y61YW7S/).







Applying the internal fillets is a little bit like playing the game 'operation'. I load up the end of the dowel with a bit of epoxy, carefully slide it between the BT and MMT, then spread it onto the fin/MMT or fin/BT intersection. I'll do 4 fillets at a time, two on the top fin/MMT and two on the bottom fin/BT. Wipe off any excess epoxy from the MMT or BT aft of the fins. I need to slide the rear CR back in so everything needs to be clean back there. I'll repeat this procedure 4 times, rotating the rocket 90 degrees each time. I'll let the epoxy completely harden in between, usually 24 hours.

I'm not injecting the fins as I like the clean look of no external fillets for this rocket. It's small enough that the double internal fillets offer enough strength. When I do injected fins I inject the epoxy through holes drilled right beside the fins which are then covered by external fillets.

 

[David Schwantz]

Was going to use motor eject in booster. Like your fin guide. Where do you get them? Dave.

 

[markg]

Was going to use motor eject in booster. Like your fin guide. Where do you get them? Dave.

I printed the guide in my 3D printer, design file here : https://www.rocketryforum.com/threads/3d-printable-component-generators.148308/#post-1824443

How are you deploying in the sustainer? You said "using a Qurk in the booster and a Quantum in the nose for both ign and seperation charge" - since Quantum only has two channels, what are you using for separation? Or are you igniting sustainer from booster?

cheers - mark

 

[David Schwantz]

Quantum wil do airstarts.

 

[Keenan Cox]

How much design has gone into the sustainer layout so far? Seems that the biggest hurdle with this kit is the limited space. Recovery, electronics and a 6g Pro 24 would fill that airframe nearly all the way. Certainly less of an issue on smaller motors, but if you're looking for maximum altitude out of it, space is going to get very tight very fast. I'm excited to see this build chug along and maybe snag a couple ideas for my Nike-Asp along the way!

 

[David Schwantz]

I also have the 6g 24mm. I will use a streamer for recovery and a rocket hunter. Have taken it to the belt sander and have made it about as small as I could. Actually had to order another case as I broke the first one it got so thin. Will use friction fit and aluminum tape to hold motor in. Made the coupler fit as smooth as I could. Should drag separate. Anyone know how to ground test drag separation?

 

[Cameron Anderson]

I also have the 6g 24mm. I will use a streamer for recovery and a rocket hunter. Have taken it to the belt sander and have made it about as small as I could. Actually had to order another case as I broke the first one it got so thin. Will use friction fit and aluminum tape to hold motor in. Made the coupler fit as smooth as I could. Should drag separate. Anyone know how to ground test drag separation?

Unless you have a wind tunnel, you don't.

 

[cerving]

Since the booster is so much larger (and draggier) than the sustainer, it should drag separate just fine assuming that your fit into the interstage is nice and smooth. My Double Shot drag separates readily... 4" to 54mm, not much different than 2.6" to 29mm really. If push comes to shove, your sustainer ignition will certainly separate it!

 

[markg]

Just a couple of little things to finish on the bottom of the booster. I drilled and tapped for 1010 rail buttons (https://rail-buttons.com/3p1010.html). Tapping gives the mounting screw a really good connection and on a rocket this size, no need for epoxy. This also makes them removable so no need to mask for painting.

I mounted the rear CR with 15 min BSI epoxy. There was a bit of cleanup needed on the airframe to get the CR in, I just chipped out the epoxy with a small chisel.

Once that was in place, I filled the holes left by the hooks I used to remove it and glued in the 38mm MMT with JB weld.





I'm not putting external fillets on these fins, the internal ones offer plenty of strength for a rocket of this size, so the bottom of the booster is done. Let's get the AV-bay taken care of next.

 

[David Schwantz]

I once had a turbine that would flame out on the take off run during the winter. Thought it was the cold air stream causing it. So we took my pickup with me in the back at -20 and drove down the road at 60mph to simulate the take off roll. She ran flawlessly. As it turned out, the nose ski was causing just enough snow to get ingested into the intake to cause the flame out. Fix was just a little tape over the lower edge of the intake. Guess I could do that again with the rocket and have someone slam on the brakes at 98 mph

 

[Keenan Cox]

I will use a streamer for recovery and a rocket hunter.

Streamer recovery caught my eye as well. I have been looking at thin-mil parachutes for smaller packing volume. The NC looks to have enough room in it for a small tracker (RF or GPS), just need to figure out how it would all be laid out internally.

Made the coupler fit as smooth as I could. Should drag separate. Anyone know how to ground test drag separation?

As far as drag separation, I've had good results with a strong but loose fit of the ISC. If the sustainer pulls free from the booster with no added help, but otherwise isn't wiggling around, I'd expect to see fairly reliable drag separation. When in doubt, a small separation charge, maybe 0.1g or 0.2g would probably do the trick in the small volume of this rocket.

 

[markg]

Streamer recovery caught my eye as well. I have been looking at thin-mil parachutes for smaller packing volume. The NC looks to have enough room in it for a small tracker (RF or GPS), just need to figure out how it would all be laid out internally.

The NC for the Deacon (and likely the Apache) will fit an Eggfinder Mini and a Turnigy nano-tech 180mAh 2S. Hmm, it looks like that battery is no longer available, here's a 300mAh that is just a bit longer and 1.5mm thicker, it will likely fit as well.

https://hobbyking.com/en_us/turnigy-nano-tech-300mah-2s-45-90c-lipo-pack.html

cheers - mark

 

[markg]

Time to get started on the I/S AVbay for the booster. I'll be using the same electronics sled that I fly in my other 2 stage projects, it has an Eggtimer Quantum & battery. I configure the Quantum to fire a charge at apogee and apogee + 1 for redundancy. Usually have motor eject as a 3rd chance of getting the laundry out.

When I ordered this kit I had them include an extra AVbay lid :

https://www.madcowrocketry.com/2-6-66-mm-black-g10-avbay-lid/

It will be secured on the aft end of the 2.6" coupler to seal up the I/S to form an AVbay for the booster.

I started by epoxying the 29mm coupler centering ring to the 2.6" bulk plate.



Once that was dry I used a 1/4" rod and a couple of wingnuts to line up bulk plate with the AVbay lid and drilled 13/64" holes for 2x#8 stainless rods. Since I am using an existing sled, I placed the sled on top of the AVbay lid and slid #8 rods through the lugs on the sled to mark the location of the holes.



I then dry fit the coupler to mark the length of the #8 rod with masking tape. I chuck up the #8 in a drill and spin a nut onto the rod to just short of where I'm going to cut it.



I clamp the rod in a vise and cut it with a hacksaw. In the picture below I am cutting in between the masking tape and the nut. The piece I want is to the right of the vise. After the cut I remove the nut which cleans up the thread. I then use a file and/or bench grinder to further refine the threaded end as needed.


The threaded rods are now secured to the forward end of the coupler with nuts & washers, locked in place with red loc-tite.



The bulkplate and 29mm coupler CR end is now epoxied in place at the forward end of the coupler.



Here's what it looks like with the sled in place (Quantum temporarily removed) :

 

[Charles_McG]

I scratch built a Nike Apache - paper rather than fiberglass. At the PSII Nike Smoke scale, the Apache was BT55 - a hair bigger than 29mm motor tube.
It's tight to fit everything, for sure. I went with the 'fat' payload version of the Apache, since there is a legacy Estes PT5560 transition - that fits a Quantum and an Eggfinder and two batteries like a charm.

I put a Quark (and battery) in the Apache nosecone to handle main, and let the Quantum do stage ignition and drogue (streamer).

I never got drag separation to work. And blew a quarter panel out between the sustainer fins (up to the aft centering ring) twice. I think fiberglass will be your friend here.

They look sooo nice going up. Looking forward to flight pics.

 

[markg]

On the aft end AVbay lid, I put two terminal block connectors that I will connect the charges to for flight. You can get them from any electronic supplier, I get them from Aliexpress (https://www.aliexpress.com/item/32772701692.html).



The terminal blocks are secured in place with epoxy. One of the wired ends of the terminal block has a JST connector, the other is just tinned to match the connections on the Quantum. On one of my HPR 2 stage rockets, the Quantum fires the separation charge, so it has a terminal block to directly connect the igniter that fires the charge.



A welded steel eye 3/16" from Teddy (https://onebadhawk.com/welded-stainless-steel-eyes.html) and a couple of #8 wing nuts complete this part of the build.

To finish off the I/S coupler, we need to notch out the 29mm coupler that slides into the rear of the sustainer to allow room for the ignition/separation charge wires. To do this I need to glue up the MMT of the sustainer and figure out the wire channel, I'll post details about that in the next post. In any case, here is the rear of the sustainer showing with wires. Using the sustainer, I marked off the 29mm coupler where it needed to be notched to allow the wires to route through.



The coupler was easy to cut with a dremel and a cut-off wheel. If this was a larger/heavier rocket, I'd likely make this coupler out of aluminum, but with this light of a rocket I'm not concerned about the notch. After cutting, the coupler still feels plenty strong and it has a solid fit into the rear of the sustainer.



Test fit with 24mm motor :



To finish off the AVbay I/S, I epoxied the transition and notched coupler to the 2.6" AVbay coupler.

 

[blackjack2564]

well thought out for such a tiny space.

 

[markg]

Let's take a look at the sustainer build now. First off, it's tiny. When I ordered this kit I was thinking of the size of a 38mm rocket, not 29mm. 29mm is smaller than I like to build for HPR, and if I was really on the ball I probably would have skipped this kit. But since I ordered it I'm going to build it and accept the challenge. (Spoiler alert, it's not as hard as I thought it would be).

The sustainer AVbay is going to have a Raven4 which will be responsible for igniting the sustainer and firing a separation charge. In order to do this I need to route wires from the AVbay at the forward end of the rocket down through rocket to the bottom. A 24mm MMT in a 29mm airframe does not leave much room for wiring. The easy way out would be to cut a small hole in the airframe below the AVbay and another in the booster transition. Run the wires along the outside of the airframe and tape them in place with some electrical tape for flight. Easy peasy and since I'm not going for altitude with this rocket, I should really just do it that way.

So of course I'll do it the challenging way instead. I'm ruling out HEI as I will likely use DMS motors in the sustainer and there is not a commercial 24mm HEI solution either. I'll save HEI for when I have a 38mm min dia 2 stage rocket to fly really high/fast.

I started on the sustainer by dry-fitting with the I/S coupler. The way the kit came, the I/S 29mm coupler fits just up to the aft CR on the sustainer MMT. I lined up the MMT for the sustainer up with the rear of the airframe, sustainer motor will be friction fit.



I marked the location of the couplers and fins with a pencil through the fin slots.



The fin slots on my airframe were all too narrow, so I used a thin file to open them up enough to get a good tight fit with the fins.



For the MMT, I cut up 8x1/32 balsa strips that matched the length of the fin tab.



The balsa strips will form pockets for the epoxy for the fins as well as provide a channel for the wiring needed for igniting sustainer and separation. I epoxied the CRs in place, leaving a non epoxied spot that I filed away afterwards for the wire channel. I epoxied the balsa strips on either side of the marked fin locations, leaving approx 3/16" between the strips for an epoxy bed for the fins. Make sure not to get any epoxy on the pencil lines where the fins will be going.

 

[markg]

Next I epoxied the MMT into the sustainer airframe, lining up the aft end of the MMT with the aft end of the airframe. Cat5e cable squeezes through the channel. An Estes pro sonic II igniter slides through much easier so I am going to try and track down that gauge wire.



The fin tabs are a little long on these fins, which leaves the rear of the fin away from the airframe. I hit them with the belt sander a bit at a time until I got a good fit. A pencil mark/estimate gives me a reference line so I can sand it straight and not remove too much. I numbered the fins/airframe at this point.



I notched the bottom of the fins with a dremel and cut-off wheel. There is not much room for epoxy, this increased surface area will help get a good hold between the fins and airframe.



I 3D printed a fin guide, then used West Systems 105/404, injected with a syringe to attach the fins. I did all four fins at one go.

I filled the slot with epoxy, put in the fin, pulled it out, added more epoxy, then put the fin in again. After wiping off the excess epoxy I 'sealed' each fin joint with electrical tape to keep the epoxy from dripping out. I did not put any epoxy on the aft end of the fin outside the fin slot.



After fins were dry I pulled the tape off. Fins feel really solid. I am going to add external fillets to further strengthen the join.



I need to add external fillets and epoxy in some kevlar for the harness to finish off the bottom of the sustainer. AVbay and nosecone setup are on hold while I wait for an additional 29mm coupler to come from Madcow.

 

[Chris Liddell]

@markg - I’m really curious how you approached the dual-deploy setup on the sustainer. Do you have any update you could share? I’m working on a sister kit (Nike Apache) and am struggling on the options for electronics and power that will fit in such a small configuration. I don’t have a Raven4 yet and Not sure I can pull off a setup using both an Eggfinder proton and quark with the room available.

 

[David Schwantz]

I also have the Apache. Quark went in the booster,in the transistion. Quantum goes in the sustainer, in the NC shoulder.

 

[MNay]

2.6 Nike Apache...
Smallest space I had to work with...
- interstage coupler with separation charge
- Sustainer ignition wires scored into MMT to allow space for coupler
- nose cone contains battery and Quantum
- deployment charge and Airstart wire connected to Quantum
- small chute and tracker inside tube

 

[MNay]