3” Frequent Flyer build

[Bill Hanson]

All the parts for this design came today. Mike at MAC Performance made this into a kit for me.

I had heard great things about MAC Performance kits, but getting the real thing was quite impressive. All parts fit with very tight tolerances. I’ve heard the joke about flying it without gluing it together, and the reality isn’t far off.



The included electronics bay has a 3D printed sled, plus high-quality hardware all around, including forged eye bolts and nylon locknuts. Couplers were “stepped” to fit nicely.



Mike also included a pre-done forward centering ring with Kevlar harness already installed, plus a boat-tailed aft ring. I’ll have to do a little sanding to fit the motor retainer, but that looks like the only sanding necessary.



The fins were already beveled, and made of canvas phenolic, just like the body tubes. Everything is already nice and smooth — no spirals to fill in.



I’m impressed with the completeness of the kit — all hardware was included and was top quality. I only have to add the retainer plus my existing electronics and ejection charge cups for a fully-flyable model. I’m aiming to fly this the 3rd weekend in January, and this looks like it will be a quick build.

Kudos to Mike for turning my .ork file into such a high-quality kit — and at a very reasonable price. I’ll start the assembly tomorrow!

Bill

 

[Bill Hanson]

Woke up to snow on the ground this morning — and I live 10 miles north of the Mexican border. Gone by noon, but first order of business was to dig out the space heater.

Did some light sanding on the end of the motor tube to fit the motor retainer, but I didn’t like how far it stuck out behind the boat tail/thrust plate.



Got out the dremel and sanded a recess in the back of the boat tail so the retainer fit into it with only the threads showing. Much better.



With that complete, I saw that there is a 1/4” space between the boat tail and where the back ends of the fins will go, so ordered another centering ring to make everything fit snugly. That should show up by the time I finish mounting and adding fillets to the fins.
(Started to say “filleting the fins,” but I knew someone was going to ask me what kind of fillet knife I was using, and how I was planning to cook the fillets)

Then I gave the motor tube a light sanding, and epoxied the forward and middle centering rings to it, being careful to make sure the middle centering ring allowed enough room for the fins. I will add fillets to the centering rings tomorrow.

I left off the aft CR so I can do internal fillets on the fins.



While the epoxy is curing, I washed the fins with warm water with iso alcohol plus some dawn to remove any residue. I wasn’t sure how the canvas phenolic would do in water, so I just scrubbed them rather than soaking them. I sanded the fins tabs lightly and sanded the nose cone with 220 grit to rough it up a little and remove any mold residue.

Last task for the day was to cut out a fin jig.
https://www.payloadbay.com/page-Tools.html has a nice set of custom template generators, which I then used to cut the jig from a piece of foam board.



Next steps will be to epoxy the motor mount into the airframe and start mounting the fins.

 

[Bill Hanson]

Was watching the Alabama-Oklahoma game (used to teach at OU), but once the Sooners spotted ‘Bama 4 touchdowns, I figured my time was better spent working on my rocket.
To prep the tube, I used some sandpaper wrapped around a dowel to rough up the inner part of the tube for the motor mount. I then carefully used the opposite end of the dowel to spread RocketPoxy just above the fin slots.
I then slid the motor mount into the tube, working and rotating it once the centering rings reached the epoxy to make sure the centering rings were completely glued in. Then I carefully made sure no epoxy had gotten into the fin slots and cleaned off the excess, then left the rocket slightly nose down for the nite.
Today was fin day. First, I test-fitted the fins with the jig. One fin fit better in one slot than the others, so I numbered the fins and slots to make sure the right fin got into the right slot.

Then I put some blue tape around the aft part of the motor mount to make sure that no epoxy got on to that area which would interfere with the future installation of the aft centering ring and motor retainer.

It was another cold day, so I preheated the work area with a space heater, and I put my RocketPoxy in a hot water bath before mixing so it wouldn’t be too thick.
Then I spread the RocketPoxy on the fin tangs and the base of the fin, then installed the fin and fixed it in the correct place with the jig. Then I repeated the process for the other fins.

Because of the tight fit of the fins, some RocketPoxy was pushed up, and I moistened the tip of my glove with iso alcohol to make the Joint nice and smooth. I’ll make larger external fillets once I complete the internal ones over the next few days.

I spent the time between fin mounts removing my altimeters and switches from an old 4” electronics bay, and planned how to fit them all on the 3” sled. Since I intend on flying this one a lot, I sprung for 2 new 3/8” Kevlar recovery harnesses with custom pre-sewn loops and swivels from MAC Performance.

Here’s a question: I’m thinking about getting a large custom decal for the rocket. Can anyone point me to someone who does that kind of work? Or should I just discuss this with one of the local printing shops?

 

[blackjack2564]

Good looking job so far and the perfect all around rocket for fun flying on huge variety of motors!
Everyone should have a 3inch like this for fun!

We as a group have depended on Mark at Stickershock for years for all our decal/vinyl needs.Unfortunately his site is closed for awhile due to personal reasons. He may be back in a few weeks or ?
It would be advisable for this project to seek local option. Remember this: the more work on sizing and content you do in advance the cheaper your vinyl will cost. Spend some time Googling clip art and images to find something close to what you are after, The shop can then take your clip art and make decals a reality at very reasonable price. The more time they spend, more cost it will be. [at most shops]

Keep up the great build and have fun!

 

[Bill Hanson]

Good looking job so far and the perfect all around rocket for fun flying on huge variety of motors!
Everyone should have a 3inch like this for fun!

We as a group have depended on Mark at Stickershock for years for all our decal/vinyl needs.Unfortunately his site is closed for awhile due to personal reasons. He may be back in a few weeks or ?
It would be advisable for this project to seek local option. Remember this: the more work on sizing and content you do in advance the cheaper your vinyl will cost. Spend some time Googling clip art and images to find something close to what you are after, The shop can then take your clip art and make decals a reality at very reasonable price. The more time they spend, more cost it will be. [at most shops]

Keep up the great build and have fun!

Thanks very much for the good words. I’m intending to fly at least once or twice every month through April/May while I’m working up my L3 for May/June. Got a whole box of I and J motors on order and have an I245G on hand in case they don’t get here in the next 3 weeks. The only fly in the ointment is that I just figured out that I don’t have a Aerotech 320 case — got a 720 plus adaptor kit for my L2, thinking that would cover me, but (duh) that only works for 720, 600 and 480. I have it on order, so should work out without having to borrow it.

Thanks for the advice on the decals. I saw that Stickershock is on hold for now. Good point about pre-doing as much as possible. I’m not planning anything cosmic — just a backwards-leaning “Frequent Flyer” with some kind of broken racing stripe, along with a block/shadowed FF for the tail (hearkening back to my AF days). I’m pretty good with Photoshop from my other expensive hobby, so should be able to whip something together in a format they can work with.

Bill

 

[Bill Hanson]

Started on the internal fillets today. As before, I kept my RocketPoxy in a hot water bath to make it flow better. I also glued two hobby sticks together to make them long enough to reach all the way to the front of the fins.


With the stand holding the rocket nose down, I used an oral medication syringe to push the epoxy into the fillet areas. I then used my glued-together hobby sticks to help push the epoxy all the way to the front of the fins. Then I let gravity spread the epoxy all the way down the fillets.


LESSON LEARNED. I used a 2 ml syringe because that’s what I had on hand. That is too small for the job and led to getting epoxy where I didn’t want it. Will have to run into Tractor Supply to get some 10ml ones before doing the next ones.

Good thing I had plenty of iso alcohol and shop towels on hand to clean off the errant epoxy!

LESSON 2. Along those lines, while I was careful to put blue tape on the end of the motor tube to keep epoxy off there, I also needed to mask off the inside of the body tube to keep epoxy out. Otherwise I could easily make it difficult to fit in the aft centering ring once the job was complete.

Once gravity had done its work, I leveled the rocket to allow the fillets to level out. Notice that I put in some blue tape along the bottom to make sure the epoxy didn’t get to where it would interfere with the aft CR. I will mask off the rest — which I should have done earlier — once the epoxy cures.
.

Looking ahead to my L3 build, which is a 4” airframe with a 75 mm motor, the above procedure won’t work very well — not enough room to work with. I’m either going to have to use a large syringe with some tubing, or inject the fillets through hole in the airframe. I think I will try the first method on the remaining internal fillets and see how well that works.

I’m going to fill the nose cone with pourable foam to beef it up. Ordered some 4 lb foam from Ama$on — about the same price as other places, but free shipping vs. the $15 - $20 others wanted to charge.

[As an aside, shipping costs are weird. Needed an extra CR, but the $3.50 item had a $14.50 shipping charge. I added some extra items, and then the shipping was only $6.50 - go figure.]

I also measured the internal volume of the nose cone using a very high-tech method. Filled it with water then emptied into a pitcher — 1 liter on the nose. ;-)

 

[boatgeek]

I really like that construction stand. I might need to build one like it or adapt my prep stand.

 

[Bill Hanson]

I really like that construction stand. I might need to build one like it or adapt my prep stand.

Thanks,
They are really easy to make. Just some 1” PVC pipe plus the appropriate fittings. The ‘X’ cradles (I made 3) are padded with either pipe insulation or pieces of pool noodle.
I don’t even cement them together — that way I can easily reconfigure them, such as taking off the horizontal piece so the rocket can be stood upright.

 

[Rocketjunkie]

A word of caution. Canvas phenolic (C, CE) is strong but brittle. You don't want to drop it on a hard surface and a rough landing may crack it. Other phenolic grades (linen L, LE) and paper (all X grades) have the same problem. Great for motor liners, Aerotech uses grade XX.

 

[Bill Hanson]

A word of caution. Canvas phenolic (C, CE) is strong but brittle. You don't want to drop it on a hard surface and a rough landing may crack it. Other phenolic grades (linen L, LE) and paper (all X grades) have the same problem. Great for motor liners, Aerotech uses grade XX.

Thanks for the heads-up on that. Fortunately, the SMRA Alamogordo launch area, while desert, isn't hard pan like some places. Since the rocket is pretty light, I'm using a 36" main which gives me 19-20 fps hitting the ground.

That's of course assuming that I didn't hit any fence posts, which I managed to do on the flight after my L1 launch -- hard to design for that! LOL.

Do you think I should go with a bigger chute, then?

 

[Rocketjunkie]

Landing on the motor shouldn't be a problem. More likely is falling, having something fall on it, or flying on a windy day where it lands with a high horizontal velocity. If using motor ejection, a high speed deployment probably won't zipper, it will just snap off instead. PML phenolic tubing has the same problem, that's why they introduced the Quantum tube (which melts if too hot). Ballistic recoveries shatter into a lot of small pieces

 

[Bill Hanson]

Landing on the motor shouldn't be a problem. More likely is falling, having something fall on it, or flying on a windy day where it lands with a high horizontal velocity. If using motor ejection, a high speed deployment probably won't zipper, it will just snap off instead. PML phenolic tubing has the same problem, that's why they introduced the Quantum tube (which melts if too hot). Ballistic recoveries shatter into a lot of small pieces

Thanks,
I'm dual deploy all the way. I'm intending on flying this at least once or twice every monthly launch day until the summer -- got a box of I and J motors inbound -- so will have plenty of opportunity to check it out in flight ops. Will give a "wear and tear" report as I go. Guess that any airframe material has its strengths and weaknesses, so will be interesting to see how this one works out.
My next build (for my L3) is fiberglass -- I'm being <really> careful not to drop those pieces on the garage floor. Don't ask me how I know that fiberglass doesn't like sharp impacts.

 

[Bill Hanson]

I think I’ve broken the code on doing internal fillets.

I had a 10ml irrigating syringe, and cut off the curved part. Then cut a piece of aquarium tubing to a couple of inches longer than the fin tang. To help make sure the thing didn’t come apart at the worst possible moment, I snugged it down with a zip tie.


Mixed up the RocketPoxy and used a narrow plastic knife to spoon the epoxy into the back of the syringe. I pushed the tube all the way until it touched the centering ring, and slowly pushed out a bead of epoxy while pulling the tube aft.


This made a pretty nice fillet. Not a thing of real beauty but will do the job.


I will need more practice to make them consistent in the future. Maybe I can thin some peanut butter and use that as an epoxy simulator. I foresee lots of PB&J sandwiches in the near future.

I haven’t tried the “inject into holes” method, but a) I don’t think it would be any less messy, and b) this is plenty good enough for my current purposes. This is how I’m doing it for my L3.
“Better is the enemy of good enough.”

 

[Bill Hanson]

Got a lot done today. Finished up the internal fillets this morning, next step for the fins will be the external fillets.

Then, Christmas in January! Got not one, but two rocketry-related shipments. First was the 2-part pour foam. Stuff was ice cold from being on the truck, so first thing was to put the bottles into hot water so they would come up to their 75 degree working temperature.

While things were warming up, I figured out how much of the stuff I would need — a surprisingly small amount. From earlier, I knew the volume of the nose cone was 1 liter, or about 33 ounces. Since the foam expands 15x, that meant only 1 ounce of each part (total of 2 ounces) was required. I carefully marked out 1 ounce on two clear plastic cups, then combined them and quickly poured the mixture into the nose cone.

While the foam was expanding, I held the nose cone in a bucket of water to keep it from getting too hot — and it does get hot while it’s forming.


Turned out to be almost exactly right. Only a small amount bubbled up through the hole, which I easily trimmed off.

The only tricky part of this exercise was replacing the eyebolt with a forged one. When taking the old one out, I discovered the thing was only finger tight. The trick was getting the nut and washer properly inside the nose cone with only fingertips. I ended up getting out my hot glue gun and tacking the nut and washer together, which gave me only one thing to line up. I put some blue Loctite on the bolt and tightened it all down before doing the foam.

My next shipment was a new set of recovery harnesses plus another centering ring. The rocket is a bit less than 5’ so the harnesses are 15’ long with loops at the ends and a third at 5’. Mike at MAC Performance did a great job doing the Kevlar with pre-sewn loops and swivels.


Last step was to fit the centering ring, boat tail/thrust plate, and engine retainer. As I mentioned earlier, there was about a 1/4” gap between the boat tail and the fins, so the new centering ring was to fill in that spot. The ring was just a smidge too thick, so I chiseled out some space for the fins. Had to go back and forth to get things exactly right.


I ended up putting a couple of screws part way into the ring so I could pull the thing out as I modified it.


Once I got everything fitted right, I used JB Weld to attach the “spacer” ring, the boat tail, and the motor retainer. I left the rocket nose down while everything was setting up.


Things are starting to actually look like a rocket! Tomorrow I will start the external fillets and getting a the altimeters, etc. mounted on the electronics bay sled.

 

[Bill Hanson]

I started out working on getting the altimeter bay sled laid out. I have a couple of 9v battery boxes on order. I’m setting this up with the two altimeters on “top” of the sled, with the pull-pin switch and batteries in between the rods on the opposite side.

First order of business was to position the altimeters. My original idea was to RRC3 lengthwise and the StratoLogger CF crosswise, but the threaded rods got in the way of the mountings screws. So they are going to be side by side, offset to make connecting wiring easier.


The pull-pin switch was next. It needs to sit above the rods, and be tilted a bit so the “Remove Before Flight” pin goes cleanly through the vent hole. I had some door shims on hand, so cut several pieces and glued them together to make the raised ramp for the switch. I’ll epoxy the ramp to the sled, and put a screw through the back of it just in case.


With the switch in the middle, batteries will go on either side. I have some snap-in battery boxes on order. The off-brand batteries in the pic are just place holders. I always use Duracells since the internal connections are soldered.


Once the battery boxes get here, I will refine the layout to make sure that screws from one side don’t interfere with the other, and then get everything connected up. I will also start making/mounting my black powder wells and the junction blocks.

With that in hand, on to the fin fillets. I am using the fairly standard approach of using a 1” piece of pvc for marking and shaping the fillets. First, I used a pencil to get a lot of graphite on the 1” pvc, then pulled it along each fin joint to mark the edges of the fillets, then used blue tape to mask everything off.


I then mixed up some RocketPoxy and put that in the fin joints. I waited a couple of minute to get closer to “peanut butter” consistency. After that, I used the pvc piece to smooth out the fillets. I will probably have to do some light touch-up, but the fillets are looking pretty good.


My last build, I used iFixit epoxy clay for the fillets. With that stuff, you don’t have to worry about it sagging, but it also took quite a bit of fiddly work and some bondo to get them nice and smooth. I’ll withhold judgement on which works best until I see how much finishing work I need to do.

I also took some time and test fit the nosecone on the forward airframe. Nice and snug — but a little too snug, methinks. I’m going to use shear pins, so I’ll sand down the ridges just a bit. Tried the altimeter bay with the airframe, and that is too loose. Will use plastic rivets on the front end so that’s not a problem.

I’ll have to add a little tape to the aft end of the altimeter bay to get the right degree of fit.

Maybe I should go with shear pins for that section as well? I know most use friction fit there, it is there any reason not to use shear pins there?

 

[Bill Hanson]

My fin fillets still feel a bit rubbery, so I took the rocket into the house where it’s a bit warmer than the garage, so they will completely cure a bit quicker.

In the meantime, I started working on the altimeter bay and charge cups. I’m following the method shown in https://www.rocketryforum.com/threads/dual-deployment-charge-cups.49878/#post-489288 These charge cups will hold small centrifuge tubes with the black powder charges.

This worked nicely in my L2 build, so I won’t mess with success. I used 1/2” schedule 40 CPVC to make the charge cups. I first drilled holes in the cup for 8-32 screws in the caps, and then used a larger drill bit to carefully make a countersink for the screw heads.


Then I drilled a hole in the corner of the caps to run the wire for the e-matches. After that, I pressed the cut tubing into the caps, and used the original holes to notch the tubing to allow the wires through, marking the tube and cap so everything lined up. Once that was complete, I used cpvc cement to glue everything together..


When the cement dried, I drilled holes into the end plate for the charge cups, and also 4-40 sized holes for the connection blocks. Then I mounted everything on the end plate and drilled a hole for the wiring to pass. I will repeat this on the other end.


Hopefully the battery boxes will arrive tomorrow, and I can get the altimeters all mounted and wired onto the sled.

 

[Bill Hanson]

Today was altimeter bay day. Those who have been following the thread know that I was planning to put both altimeters on top of the sled and the batteries on the bottom. However, after confirming the layout using the size templates from smtdesigns.com, I realized that wouldn’t work.

Instead, I went with an altimeter and battery on each side of the sled. That went pretty well, although I had to be creative in my use of standoffs to keep everything separate.

Also, to solve the “chicken and egg” problem of how to fasten stuff on one side after mounting the other, once I drilled all the mounting holes, I glued the nuts to the respective bottom sides of the sled. That way I could just mount the screws without worrying about having to hold the nuts in the 1/4” space under the stuff on the other side. That wasn’t a perfect solution, but it worked well enough.

Once I got all the hardware mounted, I used the modular wiring from my last build to wire everything up, and then used zip ties to keep the wiring neat around the sled. I have this set up so the connectors only fasten one way to prevent stuff from getting incorrectly connected in the field. I also used the brown and orange wires to connect to the drogue (pointing towards the ground and the flame from the motor) and the blue/purple (sky) to connect the main in the forward end.



Here’s a question that came up in the “Ultimate Level 3” build thread that hadn’t occurred to me, but applies to my upcoming L3 build.

Since the recovery system has to be dual/redundant, that implies separate altimeters, power sources, ejection charges and wiring. I have all that — with the exception that the dual wiring to each bulkhead passes though a single 4-wire connector.

Ultimate Level 3

Does this 4-wire connector violate the “dual/redundant” criteria? Or, do I need to split the 4-wire connector into two 2-wire connectors? Not that it’s a big deal to do that (and I would probably tape the connectors together to keep everything neat).

I don’t recall this particular issue emerging in my IREC judging. Can someone give a definite reading on this, or is this one of those “it depends on who supervises your L3” questions?

 

[boatgeek]

[some really pretty work on the AV bay snipped]

Since the recovery system has to be dual/redundant, that implies separate altimeters, power sources, ejection charges and wiring. I have all that — with the exception that the dual wiring to each bulkhead passes though a single 4-wire connector.

Ultimate Level 3

Does this 4-wire connector violate the “dual/redundant” criteria? Or, do I need to split the 4-wire connector into two 2-wire connectors? Not that it’s a big deal to do that (and I would probably tape the connectors together to keep everything neat).

I don’t recall this particular issue emerging in my IREC judging. Can someone give a definite reading on this, or is this one of those “it depends on who supervises your L3” questions?

I'm not an L3 let alone a TAP or L3CC. That said, I'd look at failure modes. If there's a reasonable failure mode where the connector failing on one of the redundant circuits would take down the other one, then you should separate them. The only one I can think of off the top of my head is if the connector might come apart in flight. If it has some sort of positive lock* and the wires are all independent, I'd still call it redundant. YMMV of course!

* On further reflection make that a positive lock that doesn't depend on skill in assembly. A connector with a clip that automatically locks everything down when it's fully closed meets that requirement. Wrapping it in E-tape may not because it may be as repeatable.

 

[Bill Hanson]

I'm not an L3 let alone a TAP or L3CC. That said, I'd look at failure modes. If there's a reasonable failure mode where the connector failing on one of the redundant circuits would take down the other one, then you should separate them. The only one I can think of off the top of my head is if the connector might come apart in flight. If it has some sort of positive lock* and the wires are all independent, I'd still call it redundant. YMMV of course!

* On further reflection make that a positive lock that doesn't depend on skill in assembly. A connector with a clip that automatically locks everything down when it's fully closed meets that requirement. Wrapping it in E-tape may not because it may be as repeatable.

Thanks for your take. The connectors have an automatic lock tab (positive “click” when seated together) and the wires are all separate. On my L2, I also wrapped electrical tape around it to make doubly sure that nothing was going to come apart. I’ll most likely keep up that practice.

 

[Cory]

I appreciate you posing this again (thread mentioned is mine). I have used the connectors on many of my HPR flights including high G flights and have never taped a connector or had one fail. Always worried the tape might actually depress the positive locking mechanism unintentionally.
The failure mode I imagine that kept me from even asking my TAPs is something, escepially a battery, breaks free under thrust and crushes the connector taking a single altimeter failure and making it a total loss.
BTW really nice build! Looking forward to a flight report on this bird.

 

[Bill Hanson]

I appreciate you posing this again (thread mentioned is mine). I have used the connectors on many of my HPR flights including high G flights and have never taped a connector or had one fail. Always worried the tape might actually depress the positive locking mechanism unintentionally.
The failure mode I imagine that kept me from even asking my TAPs is something, escepially a battery, breaks free under thrust and crushes the connector taking a single altimeter failure and making it a total loss.
BTW really nice build! Looking forward to a flight report on this bird.

Hi Cory,
You are very welcome! As it happens, I met with my L3 supervisor late yesterday to give him my preliminary package and get his go-ahead on the build, along with nuts and bolts on documenting the build process. All good. We discussed the connector question in some depth, and bottom line he did not see an issue with the single connector since all the wires are separate and the connector has a positive lock.

You could go crazy with this, methinks. After all, all the wires to the charge cups go through a single hole in the bulkhead -- what if something burned through that hole and took all the wires with it? Yikes! There are plenty of "single-point" failure modes in the recovery system (any eyebolt, any quick link, any section of shock cord, inflight meteor strikes <kidding>). If you pursued that to its logical conclusion, you would need an O motor just to get the weight of all the redundant components clear of the launch rail. LOL.

I think I'm good to go on that basis. But, I suspect that different TAPs will give different answers -- so it's best to just ask the question directly.

 

[Bill Hanson]

First off, I want to share kudos and thanks to Bill at balsamachining.com. In a great display of pre-planning <not> the only Aerotech 38mm case less than 1080 that I don’t have is a 320. The motor I was planning to fly this Saturday? Yep, a 320.

I did have one on order along with a bunch of motors from balsamachining.com, but that was on the “preorder” deal, where your shipment doesn’t go until everything in the order is there. That wasn’t happening anytime soon, so I explained my situation and Bill immediately offered to ship my 320 case anyway. Thanks and much appreciated!

Today was the day for buttoning it up for the first time and for ejection charge testing. Before I started drilling holes, the first order of business was to mark the line for my rail buttons. I used a piece of paper wrapped around the airframe to mark the locations of two fins, and then figured 1/2 of that to get my correct spot for halfway between them. I suppose I could have calculated 1/6 of the circumference of the airframe, but what’s the fun in that? I used a piece of angle iron as my straight-edge.


With that out of the way, I calculated the size of holes for the altimeter bay — 4 holes of 1/8”. Then I drilled those holes, as well as the holes for 4-40 rivets and 2-56 shear pins with a 5/64 and 5/32 drill bit, respectively. Then I wicked some CA glue (super, not California) into the holes to harden the edges. I don’t know if that’s strictly necessary with the canvas phenolic, but didn’t see how it would hurt.


I was thinking about getting fancy and using a dowel or something to “key” the coupler, airframe, and nosecone alignment, but I really couldn’t figure out the mechanics in terms of anything I knew how to do. So I went “old school” with witness marks.



As I was lighting up everything in the altimeter bay, I discovered that the 9v battery that was mounted crosswise was too high and wouldn’t fit. Fortunately, I was able to move it about 1/2” forward, which allowed me to mount the clip without standoffs. I also slightly enlarged one of the vent holes to allow my arm/disarm pin to go in a bit easier.

The moral of this story, is when you are really crafting a minimum-space bay, keep in mind that your allowable radius goes in all directions — not just sideways and up and down.

I had previously calculated the required amount of black powder, .6 and .8 grams respectively, so I measured those out and then prepped my centrifuge tubes for the charge. I drilled a small exit hole the the wires at the bottom of each tube, and threaded the e-match wire down through the bottom of the tube. I use blue stick to make sure the bottom is tight, and a disposable earplug to tamp down the powder around the e-match.


After that, I inserted the centrifuge tube into the charge wells, feeding the wires through the hole at the bottom. I left those disconnected until it was time for the actual test.


With that complete, I attached the chutes to the Kevlar recovery harnesses, packed the chutes using the burrito fold method, and rolled the harness into 3” (just under) flat “pucks.” These provide a controlled deployment, and allow packing into a very small space.


I then connected the harness to the respective eye bolts using 1/4” quick links and used the rivets and shear pins to button everything up. I also put a plugged engine casing into the engine mount. Oh yes, I did hook up the e-matches to the junction blocks.

On to charge testing. So as to not put any voltage spikes to the altimeters, I wired directly into the bulkhead connectors, and ran the wire out of the vent holes. This way I could trigger the charges one at a time by simply touching the wires (wire extended 20’).

Kicked off the drogue charge — meh. Probably would have been okay, but a little iffy. Kicked off the main, ‘whomp’ and the nosecone barely budged. Not good.

Try number two. Up by 0.2 grams for the charges. Drogue went about 12’ (15’ tether) and laundry came out. Main charge — ‘pop’ and nothing. That’s not right for 1 gram of BP.

In one of my D’oh! (I mean learning) moments, it occurred to me that this was the 4th e-match ignition on the same battery. Plus I had been using the same one for testing switches and altimeters previously. I’m pretty sure the battery was tired, and when I redid everything and used a new Duracell, everything worked perfectly.

With all that complete, we are GO for painting!

 

[Bill Hanson]

Started the painting process. Since I’m planning to launch on Saturday, I don’t really have time to do a really slick paint job. There is simply not enough time to allow coats to thoroughly dry before sanding. So it’s getting a basic rattlecan paint job.

Given my painting skills, this may be a lesson on how not to do it.

To prep the nose cone, I used Duplicolor adhesion promoter, which is used to prep flexible plastic parts on cars. After 3 coats of the adhesion promoter, I used Rustoleum 2x primer for another 3 coats. After plugging vent and other holes, I also gave the rocket body 3 coats of primer.


After letting everything dry for a day, I carefully sanded everything with 220 grit sandpaper. Clearly, everything needed more time to dry — my hands ended up white from holding the pieces as I sanded. But, “needs must” if I wanted it to be any color other than primer white.

I wanted a high vis paint scheme, so I got some Rustoleum fluorescent orange, along with candy apple red. The nose got the red paint, and the rest got the orange.


Important lesson learned! The orange fluorescent doesn’t cover very well. The sanding job left a few darker streaks, and even after 6 coats, they still show through the paint. Not good!

My plan is to try to paint the fins red, but that’s pretty iffy— the orange paint may not dry enough to be masked without the tape pulling the paint off. I’ll wait until Friday, and test to see if the tape removes the paint before I try anything.

After flying on Saturday, the rocket will “earn” a better paint job. More important, I’ll have enough time to do it better.

I do have a few final tasks. First will be to re-weigh all the components, and the rocket as a whole. Then I can double-check the CG and stability margins. With the relatively small I245 motor, I don’t anticipate having to add any additional weight, but I will make sure before taking it out to fly. Along the way, I’ll pack up the chutes and shock cords and prep the ejection charges (leaving them out of the rocket, of course), and assemble the motor.

From my flying days, I’m a great believer in checklists. I will run my packing and final prep checklists to make sure everything is ready before heading out to the launch. I have additional checklists for prep at the field, launch, recovery, and emergency situations. Good practice for my L3 package!

In other news, I went over my L3 plan with my L3CC and am good to go to start my build. Woohoo!

 

[Bill Hanson]

While I complained last post about how poorly the fluorescent orange paint covered, it does dry much faster than the gloss red. So I was able to mask off the tail and put red tips on the fins. Here’s the completed look.


After weighing everything and checking the CG, it all looks good. Right at 2.0 calibers of stability, and it will come off the rail plenty fast.

Those who have followed this thread from the start will recall that my original goal was to design something that weighed in at 1500 grams. After a lot of iterations, it was clear that it wasn’t going to happen — particularly once I added the redundant DD stuff, so I didn’t worry about saving weight during the build.

Maybe I should have. Cheops’ Law (everything takes longer and costs more than you plan) and its first corollary, “and weighs more,” was clearly in effect. The thing weighed in at 2935 grams —almost 2x the original plan idea. Key weight additions:
- using expanding foam in the nose cone
- redundant DD setup (added a lot of weight right there)
- heavy-duty Kevlar recovery harness

The bright spot is that most of the weight gain was forward of the CG. As I originally laid it out, using a heavier motor (like a J420) was going to require a little extra nose weight. As it is now, nothing extra needed for any motor that will fit into the thing.

I’m flying it tomorrow, and will give a report after that completes.

I intended this to be a “warts and all” build thread. Both to help me think through things I could have done better and to help others to learn from my mistakes. I greatly appreciate the comments and input I have received along the way. If anyone has additional thoughts or advice, I thank you all in advance.

 

[Bill Hanson]

Success! The maiden flight went well enough, and everything worked as advertised. Rocket recovered in perfect condition despite major league operator error.

However, not a nominal flight. Some person who will remain nameless, but whose name rhymes with "Bill" allowed himself to get diverted during final assembly and forgot to attach the quicklink at the front end of the electronics bay. So the front part descended on the main, and the fins plus electronics came down on drogue -- both parts landed in the desert within 25 feet of each other.

Even so, definitely NOT A GOOD THING -- I really screwed the pooch on this one, and am lucky that no harm or damage was done. Big-time lesson here, and fortunately it wasn't an expensive one.

The aft section survived without a scratch -- no damage at all. For those in doubt about the durability of MAC Performance canvas phenolic, doubt no longer. Descent rate on drogue was about 50 fps, per OpenRocket.

 

[Bruiser]

Hey Bill,

I was getting worried that I might be distracting you, but I know I was gone before final assembly The launch was pretty awesome. Looked pretty fast off the rail to me and it had a lot of "presence" in the air. Not having much experience, I was wondering if it was supposed to come down in two pieces.

It was nice meeting you today. Your rocket is very impressive and I hope to see it again next month.

Thanks for your help getting my Tomahawk in the air today. That was very exciting for me!

Bob

 

[Bill Hanson]

The rocket needed a better look now that it has proved itself.

I had Mark at stickershock23.com make me a set of Frequent Flyer logo decals plus tail numbers. I used the old Santa Fe railroad logo and paint scheme as a point of departure.



It needs some clear coat yet, but IMHO it all came out pretty sharp.

Bill

 

[Bruiser]

Came out real nice Bill. Are you planning on coming over next Saturday for another launch?

-Bob

 

[Bill Hanson]

Came out real nice Bill. Are you planning on coming over next Saturday for another launch?

-Bob

You bet! I have an I180W ready to rock. Should be about 1600' per OpenRocket

Hopefully my box of J motors (along with my M1350 for my L3) should get here soon.

 

[crossfire]

Nice looking build. What are planning for your L3 flight?