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Jack of all trades, Master of... (oh never mind)
TRF Supporter
Aug 29, 2020
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Northeast Ohio
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... :rolleyes:

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.]
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Basic parts:
(3) Der Big Red Max kits
(3) Launch Lab (Vander-Burn) upgrades
[Only need (2) plus some CR's]
(2) 3" body tube and coupler from Estes
(1) 12" 29mm MMT (LOC) stuffer tube for core.
Misc. plywood parts, card tubes, Etc. (Not shown)
"Stack up" of parts for visualization... (this is big...:oops: )
Weighed out the parts where there are multiples and tried to "balance" them around the core axis.
Then built the MMT's. (Retainers NOT mounted. Just there for show.)

Cut Estes 3" tube to length, and cut 2 slots for the interconnect "fins".

Test fit fins, tubes, MMTs, etc. for best fit and balance. (Number all the joints for location.)
Then epoxy MMTs into tubes.
One concern is if a side motor doesn't light. Planned apogee would not be reached and motor delay would be way off. Also, if the core motor didn't light there would be no ejection.

SO... Deployment will be handled by an Eggtimer Apogee. [ Hopefully it always gets high enough for the Apogee's Launch Detect logic ] The core motor charge will be used as backup. (The side motors will have ejection charges removed.) Original plan was to put the Eggtimer Apogee in the nosecone, but then I changed my mind... It will go into the coupler between the 2 sections of core body tube. That way if I do fly this high power, I can put a tracker in the nose. Both ejection charges will be under the laundry this way.

Here is coupler. It has the anchor point for recovery harnesss, and (3) 24mm tubes. One is plugged on the bottom, and the Apogee is fit to the top of that tube. The coupler was a little loose so it was coated with long cure epoxy for better fit and resistance to BP residue.
Only got a little done during breaks at work this week.
I did drill, tap, etc. for rail buttons. Also got the 3 booster tubes interconnected. The biggest issue was keeping everything aligned and parallel. Slow cure epoxy was used, so I wasn't rushed, and had time to keep checking. It was done one joint at a time.

The lower connections are thru the wall fin tabs on each side of a 3/8" wide strut. So a very strong joint. (Double dip method of attachment, to build up a epoxy fillet at the MMT and center ring.) Then small external fillets were added.

I was going to leave the upper connection clear. So 1/8" x 3/8" Acrylic bars were secured with DAP RapidFuse (seems to bond well between scuffed up Acrylic and Cardboard.) Then decided I'll paint them, so the surface was scuffed and epoxy fillets added.
That's it for now. Next up: fit Coupler/AV bay, then fins, and more fillets....
Did fins, then fillets. Fins were triple diped to get a decent amount of epoxy at MMT, and CR's. Couldn't get a fin guide to work. So just CAREFULLY eyeballed them with tape in place till the epoxy set. They seem to have come out straight and even.

Trying to keep total weight so this can fly Class1 on some composites. Fillets were craft stick diameter. Added 1.6 grams of epoxy, each.

I am a little concerned about fin flutter. But will stay with lower thrust motors for early flights.
Got the AV Bay/Coupler in place and secured to booster, and payload tube with 4 plastic push-rivets each. (YES the guide says Launch-Lug/Button. It IS rotated 180 degrees from that, so I can access Eggtimer Apogee's Screw Switch.)

The nosecone's of the pods were also pinned in place with 4 plastic push-rivets for symmetry.

Launch-Lugs were made by modifying a 80/20 UHMW Linear Bearing. They were test fit to the body, for now. Alignment was checked with a 24" length of 1010 rail. (Nice and Smooth.)

That's it for today.
Scuffed up the retainers. ID, End, and the 1/8" of OD past end of the threads.

Scuffed the OD of exposed MMT. Then wiped everything with denatured alcohol, a few times.
I used slow cure high temperature industrial epoxy. While it's very thin I brush it on the MMT. It soaks thru the scratched up Glassine layer. After about an hour the 6.2 gram batch was starting to thicken. Another layer is brushed on the MMT to continue saturating the cardboard. Then a thin layer is brushed into the ID of the retainer, to "wet the surface" with 100% coverage. The ring is pushed onto the MMT with a slight twist. Excess on the MMT fills the small gap to the CR. The ID is wiped clean. After another 30-60 minutes it's thick enough to firm fillets, so the OD of retainer gets a small fillet to the CR. Weighing the leftovers, I used about 3 to 4 grams to mount all 3 retainers.

Started assembling the parachutes. By wiping with alcohol.

The plactic tabs have what looks like 3M VHB adhesive. If you look "close" at the first picture there is "unevenness" to the bond. They could be lifted and repositioned at this point. After applying moderate pressure for 10 seconds there was 100% uniform bonding appearance. (Look close at 2nd photo.) An hour later they are very well "stuck" too the parachute.
Been busy, so not much time to work on this. QUICK update. The parachutes were VERY creased from being sooo folded into a tiny pack. I sat them outside in the sun on a 90 F day and tried to stretch slightly to flatten them ... didn't work too much, but some.

Then finished adding the tabs, lines, and swivels

Today was "Paint Day". Flexed my break periods at work around the paint, sand, recoat schedule. Got 2 coats of Rustolium Universal Bonding Primer, then 3 coats of Krylon Fusion Flat Black (or) Flat Fire Red . (Stacks of skids and some bits-n-pieces for support...what ever it takes right.)

That brings this thread up to date...
Not sure how to do a poll, or if I can this far into a thread...SO asking for opinions

I have not done clustered composite motors...

For this rocket I have 2 thoughts and am open to suggestions. Rocket needs ~45N for 3:1 T:W and 75N for 5:1 T:W. Also I have 8ft rail for launch. So lots if time to build speed if needed.

1) Make the first flight on center motor only on a G79, G80 etc. Simple no timing issues, etc.

2) Go for broke and load up all 3 motors with F42 Blue thunder motors (light easy, and fast)

3) other thoughts?

Remember the Eggtimer Apogee will be main deployment maybe with a JLCR.
Worked on the recovery system a little the last few days. Overview : it will be 1/8" tubular kevlar from AV bay to a little past top of body, then LOC 3/16 tubular Nylon for shock cord and risers, (4) Estes Skull and Crossbones parachutes, Fruity Chutes deployment bag, with Rocketman pilot chute...maybe JLCR too.

1st up was cut-to-length, and finishing the ends. I don't like the sewn loops. They have too many places to catch. All ends were looped with finger-traps. This included finishing by adding 6 stiches with the sewing awl to prevent "creep" of the finger-trap from shock loading.

Kevlar leader was attached to the AV-Bay, 2 layers of double wall heatshrink at the body tube end, and Nomex sleeve.

The riser lines were added to the 4 Skull and Crossbones parachutes. Then a "test" packing to check the fit in the 3"x9" Fruity Chutes Deployment Bag. (A little room to spare ) I will add a few stiches to divide the elastic straps to separate each set of lines and riser.

Went ahead and did layout of the shock cord and full recovery system. Will fine tune it next week. It all fits and slides easily.

This Rocket is definitely the antithesis of "keep it simple"...🙄 What was I thinking... 🤔
The four super light weight chutes in the deployment bag might be tricky

Tbh, never been one for deployment bags, but know many use them successfully
Well.... as I thought would probably happen... the rocket took it's name too seriously, and will be too "heavy" to fly class 1. SO, this is the right fourm for "almost" all flights.

Official "READY TO FLY" all up weight with all the bells and whistles is 1476.5 grams. (No- motors)

I was close, but 3.5 cans of spray primer/paint, all the decals, and my estimate was low on the deployment bag. (Probably used a little more glue than estimated, too.)

If I strip out some of the rigging, the 5 parachutes; then fly with 1 ThinMill chute, on only 1 core composite motor; it might be class 1 on a G80. Probably won't do that though.)
Hey by the way, showed your pix to my girlfriend, she approves of Heavy!

Currently we're building papa, mama, and baby Red Maxes. 4", 3", BT60

Maybe some day Goldilocks will appear, BT80?
The four super light weight chutes in the deployment bag might be tricky

Tbh, never been one for deployment bags, but know many use them successfully
I like to "play" with recovery systems. The fields we fly at are limited in size. High altitude just means lost to the trees, lake, etc.

The only way to get organized deployment of that many chutes is to use a bag. Each riser needs to come out even. Then the shroud lines need to fully extend on all the chutes at the same time. Only then do I want the chutes to fill with air. The pressure cushion that forms under them will keep them separated.

My concern is these are farily small chutes, and VERY STIFF plastic. This means if the descent speed is too slow, it may not inflate. So if 2 or 3 "pop" open and slow the descent; the remaining ones will not open and the overall rate will be higher than planned.

Organized layout and careful planing allows these things to work. Sometimes it takes a try or two.. hopefully not this time. Those big fins will not take a hard landing.

Here is a 60 or 72" parachute I used for a duration contest in a standard Estes Big Bertha. Had (48) 72" shroud lines and a 12" Estes chute for a pilot
Photos: (you can see how it fills with air.)!
Post in thread 'Parachute Question'
Video: (full speed and slowed down)
Post in thread 'Parachute Question'
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WOW does time fly....

Been looking at this and decided to make a few changes. Since it's really to heavy for class 1; I went ahead and did a few things that I like better. They add a little weight, but at this point that doesn't matter.

1st) Cut off the "Ramp" on the bottom of the center nosecone, add provisions for Eggfinder TX, or nose weight if needed. Used .093 G10 sheet, Advels (compression thread inserts), rod end bolts, etc.)
I make the loop at the end of the shock cord big enough that I don't need to use a quick-link. Just loop it thru the eye, and over the nosecone.

2nd) I added a section of coupler tube above the body tube joint. Then added a piston to make sure the deployment bag gets pushed out, and not rely on nosecone inertia to pull it out. This is much longer than my normal piston because I am using it to take up space, hold the recovery items up at the top of the payload tube.
I did finally get 2 coats of UV protection clear coat sprayed on.

This needs to travel with kids in the van, so, I decided some travel protection was needed. Found a perfect size box and packing material. Will tape up the corners, and it's good to go.
Will post the "final" updated OpenRocket file from my other computer.
Here is final OpenRocket 22.02 Beta version file and screen shots.

Cross Section View

Simulation Chart
Notes: Launch rail set at 5ft". (my rail is 8ft). JLCR set for main at 400ft.

The next Launch were I can fly this hopefully will be July 2nd, at NOTRA in Amherst, OH.... IF the weather holds, and there will be enough people around on the holiday weekend to make it work them getting all the stuff out.

Not going to rush it with this beast though. If not ideal conditions for a shakedown flight, it will wait.

Fingers crossed... LOL


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