My first 2 stage

Ok - nearing the finish line.

I'm getting excited. Everything fits..




Booster steamer is fitted and fits.




I'm a little worried about the amount of electronic devices hanging off this shock cord - tangles are my main concern.



Does anyone else fly a JLCR and JL Altimeter on shock cord mounts that can give some suggestions?

I can't give you any suggestions about exactly how to rig up your electronics there, but John Beans always used to fly both of those devices in his rockets during the test phase of the Chute Release, so it's certainly doable.

I've flown a chute release and an alt 2 in an Estes Patriot.

My parachute attachment loop is further down from the nose (1/3 of the way to the body) and I keep the altimeter up at the nose itself. Hadn't had problems so far.

So I have been a little underwhelmed with the colour performance of the laser printer DIY clear decal sheets - I expected the lack of a white background to impact on the colour of the decals, but I WAAAY underestimated by how much...

The "Blu Fyr" logo became an almost invisible brown...




The mostly black decals worked much better.. I marked CG/CP for the combined 2stage and the sustainer (to facilitate the inevitable RSO conversations)



Something to hopefully prevent me from forgetting to hit record on the altimeter3:




And a few little embellishments...



Maybe I will add a little snorkel to the streamer pod tube with every successful flight, like a fighter pilot with enemy kills... ;^)


I've decided to try to replace the logo with a painted one, so I spent tonight cutting out a slightly larger version of the "Blu Fyr" logo in frisket film with the goal of being able to spray the logo with that same bright orange...

so I have a question for those of you that have gotten rid of decals before:

Option 1: I sand off the decal using 600-1000 grit sand paper, trying to limit the impact to the blue paint that is already there, then respray blue, then apply frisket, re-base blue, then spray orange; or

Option 2: I ignore the decal, paint blue over the top of it, and then frisket and paint as I usually would..

What are people's thoughts? My gut says option 1 is the way to do it, but I'm keen to hear from people's experience...

I tried some printable decals once. Hated them. These were inkjet and they seemed to print OK I guess. But the application was terrible. The material is too thick and feels like a thick sticker, and they pull off way too easy. Prolly would have peeled off in flight. I just never found the right material I suppose. Sandman (Excelsior Rocketry) used to sell some pretty decent ones he made for folks around here, but he's out of business. Most stuff I need these days is custom and not found anywhere, so I opted to go using vinyl. Sticks better, looks great, white IS an option and if you're like me and own your own plotter, you can make them any time you need them.

I ended up flying it as is.

Staging worked perfectly:

https://youtu.be/9MYozRTl4fo

I think I still need more practice with the chute release - it was definitely set to 300ft when I installed it.

No visible opening on decent (yes, it was on!)



Inspection of the landing site shows the JLCR open sitting on top of the chute with shroud lines to neat under it - best I can tell, the JLCR opened really near to the ground:



On powering the unit back on, it was set to 100ft open, so I'm wondering if something I did poked the button in the tube to change open altitude.

Flight went to 360m


Also, booster popped a fin on separation by the look of it - initial analysis is that the booster streamer pod shock cord struck the fin laterally on separation and popped it sideways.

I'm planning on rebuilding the booster and making the fins inline with the sustainer fins (not rotated at 45°) and using a different streamer shock cord.

Go up to 500 ft. on the chute release. I've had funny things happen when trying for a release altitude less than 500 ft (not releasing). I have heard other reports of similar things happening when set below 500 ft.

We have a guy who runs 300' consistently. That low makes me a bit nervous, but he seems to be happy with the results.

We have a tiny field, I routinely use 200' and a 100' depending on the size of the rocket, but I promise you it has a high pucker factor. 200' is barely enough time for a slow opening and time to slow the rocket down.

OK, so my booster popped a fin after staging:

Delaminated the tube despite the fillets...


Root cause: careful inspection of the fin shows a depression in the balsa, which leads me to think this is where the shock cord likely whipped past causing lateral strain on the fin itself...



So in rebuilding the booster, I wanted to make it stronger and get the fin more out of the way of the shock cord.. My previous design required the booster to be rotated 45° from the sustainer which meant this fin in question was right behind the booster streamer pod and had the shock cord running past the leading edge of the fin - essentially asking for trouble..

I have decided to return the booster fins to be inline with the sustainer fins. This means a little more clearance between the booster and the sustainer fins was needed..

I adjusted the previous fin design to make a 10mm gap between booster and sustainer fins, but I didn't like the look..

So I played with the booster fin shape and came across one that was quite visually appealing:

It kind of reminds me of an F14...







So I am awaiting more couplers from Apogee rockets, but I will start construction shortly (the coupler can be glued in post paint).

Plans for this booster build will see me using a pin to create little holes on the fin root itself, on the BT under the fin root and fillet space, to make sure the glue really has a good purchase into the BT. I will also be using epoxy for attaching the fins over wood glue..

Oh: and while I am at it, I am planning to replace the invisible decal with a frisket masked "Blu Fyr" logo...

That rocket is beyond cool, and I love the way you did the streamer pod for the booster's streamer. Other than it is just cool, and that may be reason enough, why use the streamer on the short booster? Tumble recovery seems to work well, was there a reason you opted for the streamer?

Tinker

Tinker said:

That rocket is beyond cool, and I love the way you did the streamer pod for the booster's streamer. Other than it is just cool, and that may be reason enough, why use the streamer on the short booster? Tumble recovery seems to work well, was there a reason you opted for the streamer?

Tinker

Click to expand...

When simulating this initially, the booster was tumbling up to 50m away. The streamer was designed to bring it down closer so there was less distance to cover looking for bits! It also aids locating it on the ground.

As it turns out, closer inspection of one of the sustainer fins showed it had also popped. (Telltale paint fracture along the root edge)

Analysis once the fin was removed (cleanly) is that there was a section of the fin can transition that had CA on it meant the front 1/2cm of the fins root edge was actually on CA. This prevented the wood glue used to secure the fin from bonding properly and allowed enough motion to let the fin start to pop.

Plan is for the fin to be cleaned up, and re-attached with epoxy this time. Inspection of the other 3 fins shows they are on STRONG so I'm thinking it must just be this one.

Tinker said:

That rocket is beyond cool, and I love the way you did the streamer pod for the booster's streamer.
Tinker

Click to expand...

Oh, and thank you! Your feedback is greatly appreciated!

I must say it again, I really really love the coloUr scheme on this rocket.

Boosters can take a hard landing depending on how they descend. Flutter or plummet. I've had a crumpled coupler or broken fin here and there on boosters.

Booster primary rebuild complete.

Changes to the process this time: better fin shape, I CAd all the paper on the fins barring the root edge, I put 1000 pin holes under the fin and fillet space on the BT, and used 5min epoxy this time. I also coated the inside of the tube that takes the ejection charge with a thin layer of epoxy.

Looks stout. I think you did right by the epoxy this time.

neil_w said:

Pictures always work better:
View attachment 322982

For the gray piece I just take a shortie piece of BT, cut out a small strip, and then just compress it into place. Doesn't matter if it fits perfectly or if there's a gap.


For your fin, *I* would cut a single piece, grain parallel to leading edge, and paper it.

Click to expand...

Or, you can just cut an eighth inch off of a coupler tube. Different application of the same idea: a small lip for the transition to sit on where it meets the tube.

snrkl said:

Decided to up the transition couplers to 40mm length overall. I ended up increasing the upper BT60 section by 20mm to compensate.

I've also decided to use CRs top and tail of each of the transition (it's a coupler sandwich!)

I've shifted focus tonight into trying my hand at hand made paper transitions.

Long story short: best results achieved by printing the OR transition templates directly onto 210GSM card stock and using a circle cutter.

Damn - once I figured the workflow out it was super easy and the fit is scrumptious.

View attachment 323334

I used the "cut off the tab completely and paste it under both halves" method using a very small amount of PVA wood glue.

Can't remember who suggested it but drying the transition on a curved surface worked a treat:
View attachment 323337

Question: do others CA soak before or after installation?

Click to expand...

Beautifully done. Love your circle cutter. For LP rockets I don't usually soak transitions with anything. The card stock is plenty strong. If I have doubts then I'll double up with another layer of paper.

timb said:

Beautifully done. Love your circle cutter. For LP rockets I don't usually soak transitions with anything. The card stock is plenty strong. If I have doubts then I'll double up with another layer of paper.

Click to expand...

To answer my own question, if you CA before installation, it shrinks slightly. If the fit is too tight, it will actually snap when you try to install... so my procedure is definitely CA after install.

Fin repair update.




Careful removal of the paint surrounding the old fin. Luckily the fillet lifted pretty cleanly, so I just had to tidy up and strip it back a little to make room for the new fillets.

Carefully scored the paint with a new #11 on the line I wanted to clear to, then cross hatched with same #11 the paint to be removed to break it up a little, then a VERY slow blade scrape to work the paint layers off. It's like geological strata - glad I alternated primer colours - made it easier to know when I hit bedrock.




This fin is going on with 5min epoxy this time.

Old fin vs new fin

Fin and fillets done - epoxy this time.



Some small BT and Fin leading edge paint job repair prep done also.

Name decal with frisket didn't work as well as I hoped. Basically the repaired underside had some paint dam seams that helped the frisket bleed, despite a base coat spray before orange.

Oh well: it's a 6m paint job (looks great from 6m!)

If I get time, I'll hand paint the fins LE repairs.

Other than that, it's just recovery installation (I'm adding more Kevlar length to the recovery) and electronics, then re-weighing and sim updates.

Perfect flight today:

[video=youtube;VqQIUsUPOsk]https://www.youtube.com/watch?v=VqQIUsUPOsk[/video]

BluFyr D12-0 D12-7
Max altitude392.3 m
Date10/09/2017 9:39 AM
ModeRocket
Duration26 mins 24 secs
Notes
Thrust time2.10 secs
Max speed158.0 kph
Peak accel6.83 Gs
Avg accel2.12 Gs
Ejection delay7.55 secs
Coast-Apogee7.85 secs
Apogee-Eject-0.30 secs
Ejection altitude391.4 m
Initial descent12.9 m/s
Landing speed6.6 m/s

Thrust time 2.1 secs??? Something is wrong there. D-12's have a burn time of 1.6 seconds. So with the +/-10% that should be 1.44-1.74 seconds of burn. So if you assume both at the lower end of the burn time that should still be ~2.9 seconds. Do you think you had wonky d-12's or do you think maybe the JL3 erred in reading the flight? The acceleration chart seems to show two burns but that 2.1 seconds is weird.

After watching the video, and counting my 1-1000's, (very precise), I would hazard to guess it only measured the thrust time of the booster as that whole system was under thrust for 3+ seconds.

Tinker

@Tinker: John Beans from Jolly Logic has confirmed two stages confuse the Altimeter3...

Here's the thrust curve from the Altimeter3 in more detail: