DER RED MAX HEAVY

[kenstarr]

We wait with bated breath and anticipation for the launch!
Ken

 

[Tractionengines]

OK... here's what you've been waiting for with bated breath... 2 flights yesterday July 2nd.

Flight 1 was the test-flight on G80. Went Really good 3 photos attached. Nice off the rail, dead straight boost with no spin. A little fast on landing.




https://flightsketch.com/flights/3623/
Then....

Flight 2... on (3) F42...not bad, but not so good. Only 2 lit, turned a little off the rail. Then went straight after that for a stable flight. (Good, shows 2 of 3 is a stable flight.) Recovery occurred at the "lower than expected" apogee (good) thanks to the Eggtimer Apogee; but the harness fouled, and the main didn't come out (bad).

Odd thing is this rocket did what I have only seen some tubefin rockets do... With the pilot chute out slowing descent, the booster stabilized in the breeze, and the assembly "sailed". So while vertical speed slowed (as shown in the Flightsketch data) under the pilot only; it landed with a considerable horizontal velocity to. Only damage was broke one fin and a stress crease in the body tube of that pod.




https://flightsketch.com/flights/3624/
Repairable. It will fly again. (With augmented starters, and bigger recovery for slower landing.)

Hope everyone has a great 4th of July.

Mike

 

[WV8KE]

Great job Tractionengines!
Hoping the repair goes well and looking forward to seeing it fly again.

Happy Fourth of July!

 

[Tractionengines]

Ok...pulled "HEAVY" out of the transport box and evaluated the current status, and started formulating the repair plans.

Short version:
One fin broke, body tube above the broken fin has a stress crease... Repair plan: Cut/sand out remaining part of fin & replace, add coupler tube inside body tube of both pods above top CR for reinforcement. Wick some thin CA into crease.

Detailed Analysis (for those who are the least bit interested)...
The same single fin took the brunt of both landings. First time it only made a small stress mark on the body tube of the pod. The fillet and fin still felt solid, hence cleared for the 2nd flight. 2nd landing hit the same fin into the ground but with more impact from fouled main chute. It was Gliding backwards with quite a bit of horizontal velocity in addition to the descent rate. The glue bond and fillets were loaded in tension from the top centering ring back, and tore off a layer of paper from MMT and Body. The fin above the top centering ring was in compression against the body tube making the crease. Adding the coupler to both pods in this area will reinforce it. If needed a section of body at the broken fin will be removed and coupler pieces and body tube pieces glued in to close the area around the replacement fin.

Photos.
Fin removed.


Fin piece remaining above top CR

Replacement fin aproximate location.


Aproximate location of where coupler will end up.

Onwards and upwards...hopefully.

 

[DirkTheDaring]

There is initial information over in the Rocketry Deals Forum on this rocket. Amazon keeps selling the Estes Der Big Red Max kit (3" version of the Der Red Max) for $21.99. I ended up with a number of kits.... then got this idea and got some more...

So this is a quick (hopefully) build thread for this kit bash. I do hope to keep this light enough to fly as Class 1, BUT with (3) 29mm Motor Mounts, and the overall size, the HPR Forum seems a better fit.

I did a bunch of copy-paste out of @K'Tesh OR design file for the original DBRM. My KitBash of 3 into 1 seems like it will work... Maybe even keep it class 1 if I can keep the glue amount under control...It sims OK on (3) F15-6 motors with a 7' launch rail. 850ft apogee. (4) original Skull & Crossbones parachutes.
[ NOT Class 1 with (3) F15's, it's over the 125gr propellant mass limit. It CAN use (3) Aerotech Composite F or G motors and stay class 1. (3) F42-Blue Thunder motors with a 6' launch rail. 1050ft apogee.]

Screen shot of initial SIM and OR Image. (Final SIM file will be posted at end of Build.) [If anyone wants me to post the initial version let me know and I can...but it's rough.]
View attachment 516702View attachment 516704

Wow, wow, wow, this is great! I'm building a scratch rocket that's kind of sort of similar (a good bit smaller) out of some shipping tubes. I'll post a picture as soon as I get a chance. The two outter tubes will hold 24mm engines and the middle tube a 29mm. I promise you it is not half as pretty as yours!

 

[Tractionengines]

I promise you it is not half as pretty as yours!

Thanks.... but, that was before the rough landing, and the current dissection to gain access to replace the fin...

It's starting to be repaired. But after I opened it up, and cut out the rest of the fin tab, etc... I have been too tied up at work to start the rebuilding process. I do have the plan worked out, and the parts on-hand. ( Just need to time. )

 

[DirkTheDaring]

Thanks.... but, that was before the rough landing, and the current dissection to gain access to replace the fin...

It's starting to be repaired. But after I opened it up, and cut out the rest of the fin tab, etc... I have been too tied up at work to start the rebuilding process. I do have the plan worked out, and the parts on-hand. ( Just need to time. )

Oh, I understand that!! Any pics or videos of it in flight?

 

[Tractionengines]

Any pics or videos of it in flight?

See Post # 32 above for screen shots, and link to YouTube Video.

 

[DirkTheDaring]

See Post # 32 above for screen shots, and link to YouTube Video.

Thanks!

 

[Tractionengines]

Ok... thinking of next flight after repairs are done... best way to get all 3 motors going. I have done BP clusters, but this was my first attempt at composite cluster. Everything is a learning experience...

I want to do (3) H115 DMS Metalstorm Dark Matter motors, but open to ideas.

Here is another poll...
1) Go for it with the H115 DMS motos, with starters....( ideas )
(or)
2) Stick with Aerotech SU / DMS Blue Thunder.. and augment the OEM starters (pro-cast, etc)
(Or)
2) same as above but get aftermarket starters from ...(who) [need to fit small nozzles (F, G, H, etc)
(Or)
3) use 29mm CTI motors since they have the "starter pellet".

THANKS for your thoughts, and input.

 

[waltr]

Augment starters with Pro-cast works well.
Another suggestion (saw this in the NAR mag) for composite clusters is to have the igniter leads long, then have them up next to the rocket ( some sort of holder) so the rocket can lift half way up the rail before the ignites pull out of the motors.
This gives all the ignites more time inside the motors even when one motor lights earlier.

 

[Tractionengines]

I have a set of clip-whips made up with 3' of Teflon wire to give a "little extra contact time". On the cluster flight above I did look at the igniter of the non-lit motor, and it was burnt, but only a little of the pyrogen at the bridge wire burnt, not the whole length. I don't see any burning in the launch video even when I zoom way in and slow it down. So I am assuming it burned inside the moter, but not long enough to get it lit.

 

[waltr]

I have a set of clip-whips made up with 3' of Teflon wire to give a "little extra contact time". On the cluster flight above I did look at the igniter of the non-lit motor, and it was burnt, but only a little of the pyrogen at the bridge wire burnt, not the whole length. I don't see any burning in the launch video even when I zoom way in and slow it down. So I am assuming it burned inside the moter, but not long enough to get it lit.

Interesting.

I had that happen with an AT igniter that came with an H238 reload (my L1 cert flight). First attempt to launch- nothing. Pulled the igniter and some of the pyrogen blew off the bridge wire and no ignition.
Then used a DIY Pro-cast igniter plus put the bad igniter (still had lots of pyrogen on it) back into the motor and ignition succeeded.
This was the first and only time I have seen this happen.

Seen lots on igniters fail to ignite motor (mainly in winter when well below freezing). Used a DIY igniters with pro-cast and motors lit.

If the motor nozzle is large enough maybe put two igniters in each motor.
It is possible that a DIY igniter may be more reliable. I've never had a failure of the ones I've made (nearly 4 dozen) and hand them out club launches when the factory igniter failed to light the motor.

 

[Tractionengines]

Ok.... since everyone does build threads, and eventually everyone has damage; (Storage, transport, flight, landing, cato, etc.) I am going to continue this thread with the "repairs". Hopefully it helps someone get ideas about how to do "involved rework". ALSO, FEEL FREE TO OFFER OPINIONS ABOUT BETTER OPTIONS.... THIS IS JUST HOW I WENT ABOUT IT. I am open to learning other ways too.

The plan:
1) Remove remaining fin parts. (I know there's more issues inside, so I need access anyhow.)
2) Sand off paint, primer, etc over the crease to, allow it to be epoxy (or CA) saturated for reinforcement.
3) Reinforce CRs, Body Tube, and MMT, as needed for new fin.
4) Fit, install, and fillets on the new fin.
5) Reinforce the pod Body Tubes above top CR, where the hard landing shows the fins push in on the body tube.
6) Permanently install the AV Bay/Coupler in to booster. (The shock loads were causing the rivets to tear the thin Estes tubes. The harness is attached to the coupling bulkhead.
7) Test smaller deployment charge to see if I can reduce shock load. (Looks overly energetic in slow motion.) Will keep motor backup as is. Maybe lengthen the harness.

 

[Tractionengines]

I "attacked" the remaining part if the fin with a number of bits in a Dremel Tool.
1) Sand off protruding fin, finish, fillets, glassine, etc. used replacement fin as reference for locations of CRs.


Used a VERY AGGRESSIVE carbide burr to get rid of internal part of fin. Then a "tamer" bit to clean up some.

I went to each CR, and down to the MMT. The MMT had a section that tore with the fin (shows I had a good bond anyhow...lol)



Talk about 3 steps back to 1 forward...

 

[Tractionengines]

Here is a piece that was cut to fit over the MMT. The glassine was peeled off Then 24HOUR cure epoxy was used to saturate fibers in both the "Patch" and the MMT. A weight and tape was used to keep it pressed together.


After it was cured the ID of the MMT was sanded until motors slide in.

 

[Tractionengines]

Now to close up the gaping slot. (2) sections of coupler tube were made that were tight fits to the mid and fore CRs. They are longer than needed, and will be trimmed to size the slot after the epoxy cures. The idea is: It goes around to the next fin. Then is pushed in so it's tight to the ID of the body tube. The slow cure epoxy allows saturation of the fibers.


After trimming the 1st side the 2nd side is done the same way.

 

[Tractionengines]

Next the replacement fin needed to have the TTW tabs adjusted to fit against the MMT with it's repairs. Slow careful sanding allowed it fit contours of the CRs, fillets, added tube piece, etc.


Then it was epoxied into place. (Triple diped to get a good amout of glue at the MMT. )


When the epoxy was cured enough to not move but well before it was cured, fillets were added. This lets the new epoxy get a good bond to the already placed epoxy.


That brings us up to date...

 

[user 35280]

Ok... thinking of next flight after repairs are done... best way to get all 3 motors going. I have done BP clusters, but this was my first attempt at composite cluster. Everything is a learning experience...

I want to do (3) H115 DMS Metalstorm Dark Matter motors, but open to ideas.

Here is another poll...
1) Go for it with the H115 DMS motos, with starters....( ideas )
(or)
2) Stick with Aerotech SU / DMS Blue Thunder.. and augment the OEM starters (pro-cast, etc)
(Or)
2) same as above but get aftermarket starters from ...(who) [need to fit small nozzles (F, G, H, etc)
(Or)
3) use 29mm CTI motors since they have the "starter pellet".

THANKS for your thoughts, and input.

https://www.frankumperformance.com/product-page/lil-jr

 

[kenstarr]

That's some good repair work there. I hate it when I break a fin. Truth be told though, I do enjoy the surgery involved in restoring a rocket, or pretty much anything.
Ken

 

[DirkTheDaring]

Thanks.... but, that was before the rough landing, and the current dissection to gain access to replace the fin...

It's starting to be repaired. But after I opened it up, and cut out the rest of the fin tab, etc... I have been too tied up at work to start the rebuilding process. I do have the plan worked out, and the parts on-hand. ( Just need to time. )

I'm finally remembering to post a picture of mine. It had 2 bad flights where only 2 out of 3 engines ignited. So it's in rebuild now, but will fly again!

 

[Tractionengines]

@DirkTheDaring : That will take a little work to fix. Definitely looks like stability issues plus not getting all the motors going.

Try to keep it so thrust and stability are good even if only 2 of 3 light. Here again speed off the rail helps. In my flight above with 2 of 3. You can see it angled a little right off the rail. Then went straight. Even with the off axis, asymmetrical, thrust; there is enough base drag, and fin area to make a safe flight. If it's marinal T:W ratio on 2 of 3, then much more likely to "skywrite".

 

[DirkTheDaring]

All good points. I was using C11 engines for the outer two and a D12 for the middle, because I wanted a lower flight for testing. But my original plan was for D12's on the outside and an E or F in the middle. If I had done this it might have recovered on that first whirligig flight, but I would have been more screwed on the second flight, because without the middle motor operating there would be no parachute (I should mention that the plan was to simply eject the outer two engines and only use the middle engine for the 'chute, that way I wouldn't have to worry about synchronizing ejection charges on different size engines). So the middle engine MUST lite - and didn't.

In addition, every flight that day angled off the launch rod in one direction or another, leading to the loss of 2 rockets. At that point I said screw it and packed up early. I know when I'm licked . I'm almost done with repairs and plan to try again on Tuesday if the weather cooperates.