CJ's Black Sat. "JIMBO" Jart 4 in.DD in NC [or any Jart build!

blackjack2564 said:

did you do a sim file on the Jimbo Jart......Lol?

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But of course... in DD and Extreme flavors no less

View attachment Jart_4_Extreme.rkt

View attachment Jart_4.rkt

Not at the computer....can someone run this?

Extreme Super Jart...6.8 pounds ready for motor. L3200 reached 11, 074'.

Interested in how fast it went...

gregm said:

Not at the computer....can someone run this?

Extreme Super Jart...6.8 pounds ready for motor. L3200 reached 11, 074'.

Interested in how fast it went...

Click to expand...

My quick simulation shows 11,061' and reached 1232 mph. 52-1 thrust to weight ratio. NICE Greg!

Flew the Jimbo-Jart yesterday on a I-435-T [Blue Thunder]. This little gem was one of the hardest hitting motors around before the era of Warp-9 & V-max. All of them in this series are still some of my favorites, this one is a ....5 grain ...175lbs of thrust. 38mm so I had to adapt down[yeah I know] but I like to see all the events on the 1st flight.

Gets a rocket moving quick, but not so brutal as the others. I flew it at ROCC...Rocketry of Central Carolina, a nice little field by Charlotte. Waiver is 5,000 & it was blowing 50-55mph above 2500ft. The field is boxcar shaped, with plenty of recovery room the long way, but the wind was blowing across the short side. So I figured caution was in order that day. I wanted to get it up & moving quick[so it would not weather cock] but keep it to an altitude where I could view & critique the flight....charges, length of cord, size of BP etc....So I could fine tune it, if need be later.

I was also Test flying the newest version of PML's Co-Pilot & did not want to put it in the trees first time out.LOL.

Resulting in a picture perfect flight to 2321ft and both the Co-pilot and back up RRC2+ [Missleworks] reported identical altitudes & functioned flawlessly! More on that later.


I have to get JJ out of truck, and clean it up post flight. It's pouring down rain now.

I'll get some pics of nose cone av-bay set up & final flight configuration posted later.

Jim,

I hope you are feeling better. 100% recover?

daveyfire said:

I'm definitely all over that conversion! Greg's flight ROCKED.

Can't wait to get started. Thanks for the inspiration, CJ! :cyclops:

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Was this a 4" Jart standard except for the 3" motor mount? When I ran the Rocksim with the Jart Extreme file above on a 3-grain 75mm motor, either AT or CTI, it showed them being just a bit too long and running into the av-bay. If stretched, how much? Did it also require a boatload of noseweight?

The 'standard' 4" Jart will take a 75/2560 motor & 75/2-grain, however, with room to spare. I love the idea--may have to convert my 4" Jart to a 75mm motor mount even if it will only fit large K motors! The AT K780 will make for a *very* nice flight, I think.

Jim that 435 is an awesome motor. I got 3222' when I put one in my Jart. Mine must be a bit lighter than yours.

blackjack2564 said:

Yep it's the NEW 4in Jart or as I like to call it the......... "Jimbo Jart!" :dark:

99.00 BS special sale!


22 inch airframe with 2 inch vent band + 24.5in spiral wound Von Karman nose cone = a 48in JIMBO JART 4 :dark:


4ft tall :dark:
4 in diameter :dark:
54mm motor holder!
Dual Deploy
8in NC shoulder/Av-bay.....removable!

Aluminum :y: stepped bulkplates for the nose cone Av-bay.


The one shown is prototype, the vent band is raw & BP's are raw Al.

B Sat Kit is all black and BP's are black anodized .

The perfect size for fabulous flying fin-diverious fun!

Make it the #1 seller this Black Sat.:dark:

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That is a cool looking kit! Makes me wish I would have picked one up on BS.

I received my 5" Super Jart last night, I will be following your build to put mine together. Now I need to decide between Proline or Rocketpoxy

Time to go back & finish build!

Wash all the glass.

Sand entire motor mount & both sides of CR's .

[Pics are from another build] obviously glass isn't black.LOL

I'm not injecting these fillets so upper CR placement is not critical like when injecting. I'll be using RocketPoxy on this one. [tinted black]

I used 1in. flat strap Kevlar which is overkill, but it's what I had on hand. Anything 3/8 or larger will suffice. Strap only need be long enough to just come out of airframe.

Mark for 2 notches on CR for strap.


Sand or file notches....dremel works good too.


Lay strap over outside of MM and fit notched CR over it & tube.
Bring down approximately 14 inch to leave room for a nice fillet & stuff excess strap into MM tube .
I put about 3-4 inches below CR



Lift strap and place some glue underneath. Make sure you don't glop it all over the place, remember you need room for the fins between the Y-strap recovery harness.LOL



Push strap into glue & encapsulate it with epoxy.
I went ahead and made a nice fillet on both sides of the CR with left over epoxy.

A few tips on using RocketPoxy I've learned & will share:

If you have ever used Bondo..... ya mix this stuff the same way when using smaller amounts.

But first... it goes through 3 stages of pot life. These are temperature dependent, I'm talking 70 degrees & if it's + or minus 10 or more the time value will change quite a bit. Learn to factor that in as you use this stuff.

1st mixed, it is pretty much like JB weld consistency and will flow a bit, not holding it's shape, I use for gluing BP's Centering rings on MM & strap, and fillets around CR's to tubes, vent bands, etc

2nd after 10-15 minutes it thickens up and can be pulled with a tool, such as in fillets, and will hold shape perfectly.

3rd, after 30-45 minutes it has the consistency of epoxy clay & still be used to stick things together or shape, such as broken NC tips.


Mixing:

Since it has all the fillers already added for strength & shaping I find it easier to put down 2 equal lines [ mix ratio is 1 to 1] on a section of cardboard with a tongue depressor or Popsicle stick. I can see when I have = amounts. For me this is difficult when using mixing cups & even harder when trying to weigh it on a scale. After talking to John [ who makes it] it is not that critical to get it exact. He left a margin of error to make using it easier!

So make 2 lines of equal amounts of resin & hardener. I just leave one stick in the epoxy and another one in hardener during my entire build, using a 3rd to mix with. Then apply a few drops of tint to blacken it, 4 drops for this amount. Using too much will not make it any darker but will "loosen" up the mix, making it slippery/gooier.



Then pull it from the outside to the center with mixing stick, just like Bondo.


After you have incorporated all the tint, mix in circles, till mixed thoroughly.



Finally using the edge of stick, scrape the surface of the cardboard to mix in all the residue & get a nice pile to dip from. This has been the fastest and cheapest way to do it for me. Just throw out the cardboard when done, saving mixing cups for something else.

Jim,

I was going to use Rocketpoxy to build my Blackhawk. Do you see any issue in using this over Proline High Temp?

Santa just brought me a 4" Jart...thinking about putting a 75mm motor mount in it...

Viperfixr said:

Santa just brought me a 4" Jart...thinking about putting a 75mm motor mount in it...

Click to expand...

That would be a fun flight. Might need some nose weight.

cwbullet said:

Jim,

I was going to use Rocketpoxy to build my Blackhawk. Do you see any issue in using this over Proline High Temp?

Click to expand...

Had the same question... this was Tim's response https://www.rocketryforum.com/showthread.php?60043-Wildman-Black-Saturday-2013&p=645187#post645187

Viperfixr said:

Was this a 4" Jart standard except for the 3" motor mount? When I ran the Rocksim with the Jart Extreme file above on a 3-grain 75mm motor, either AT or CTI, it showed them being just a bit too long and running into the av-bay. If stretched, how much? Did it also require a boatload of noseweight?

The 'standard' 4" Jart will take a 75/2560 motor & 75/2-grain, however, with room to spare. I love the idea--may have to convert my 4" Jart to a 75mm motor mount even if it will only fit large K motors! The AT K780 will make for a *very* nice flight, I think.

Click to expand...

Greg's Jart was a one off custom. It had 3/16 fins, the kit version comes with 1/8 thick fins. I'm not sure but the airframe may have been a tad longer. Tim made this to Greg's specs. I do NOT think it had any nose weight, but can't be sure.

Greg if you read this how about some measurements & specs.

bill2654 said:

Jim that 435 is an awesome motor. I got 3222' when I put one in my Jart. Mine must be a bit lighter than yours.

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Yes I was a bit disappointed.....sims showed it at 3200 also. But it was very windy that day & ya know how that can rob performance. I have another I-435 I'll try again & see what it does.

jus_rockets said:

I received my 5" Super Jart last night, I will be following your build to put mine together. Now I need to decide between Proline or Rocketpoxy

Click to expand...

Either will be fine, the RP does have about 6% flexibility when cured, giving it room to take a harder hit without cracking a fillet however.

cwbullet said:

Jim,

I was going to use Rocketpoxy to build my Blackhawk. Do you see any issue in using this over Proline High Temp?

Click to expand...

No

Viperfixr said:

Santa just brought me a 4" Jart...thinking about putting a 75mm motor mount in it...

Click to expand...

Easily can be done for 2-grain....you will need to great creative to fit a 3 in there. I just checked with my case [3-grain] and there is only 1in between NC & motor. You could move MM out the back an inch, that might do it or add a tailcone retainer....that should do it. Or you could move the bottom bulkplate up into the coupler av-bay an inch or 2... glue that side in permantly. between moving MM back & the coulpler trick that's 2-3 more inches of room.
You will have to dry fit parts & move them around to get it to work.

cwbullet said:

That would be a fun flight. Might need some nose weight.

Click to expand...

As I mentioned above I don't think Greg added any, but common sense , balancing & simming should figure it out. We all know if you are at this level of flying, ya should be able to build it & make it work. If not......leave it stock & go have FUN!!!:tongue:

Ps: with the threaded metal tip, ya could put a long eyebolt in and add NC weight to that making it adjustable.

Thanks Jim. I was hesitant to use Rocketpoxy on a MD build after some posts on flier's concerns about it standing up to heat. I will give it a try on my next build.

Are you going to make it in January? I would like to take a look at both this and the DD bird a little closer.

Yes CW, I'll be there with the "JimboJart" for more test flights and I'll have your stuff along too!

Time to finish this build thread, holidays got in the way!

Assembling fincan:

Slid the motor mount assembly into fincan & marked fins so 3/4 of exposed got taped and sanded for internal & external fillets.

Also sanded inside of airframe where upper & lower CR's will be glued.

These pics are from DarkStar build but method is same. Actually the upper DS fin is same as used on Jart!

Lay fin next to table edge when sanding and use finger as guide, sliding it along table edge to keep sandpaper off tape.





insert fins into airframe & mark with pvc tool coated edges with magic marker. This will show you where to tape. I have since found that when working with black tubes , use a silver shapie & you can see marks very clearly.

I'm using RocketPoxy for this build, so I want to be able to remove rear CR for internal fillets.

If using an Aero-Pac retainer, be sure to dry fit it with CR in place, so you have enough exposed MM tube [1/2 in.] to glue on the retainer. Normally I would glue it on first, but since I need to remove rear CR, must leave it off for now.

I use 2 short sheet rock screws, as they self tap, so I have handles to pull the CR off after tacking fins on.



Mix small batch of epoxy and butter the root edge, insert fin & do remaining 2. Make sure the Y-harness is NOT blocking/visible in any of the slots or fins won't be tight to MM!
Align fins.
Set aside to cure.
Make sure not to glue the rear CR on!



After cure remove CR & screws from same.

I forgot to mention....I always wipe surface to be glued with denatured alcohol just before gluing so I have a clean oil & dust free surface.

I taped 2 mixing sticks together, so it would be long enough to reach front of fin inside.

One of the nice things about RocketPoxy is after you have used it for awhile, you learn when it reaches the "stay put" stage. about 15minutes after mixing for me. I can do all the internal at once. Since I have the airframe already taped off, I can use the left over epoxy on an external fillet..... no waste! I kept it smaller than the final fillet, using the stir stick to pull it smooth & that will be my first external one as soon as the internal solidify[ I'll go over it with a larger one later] ,so I get a chemical bond & no need to sand. Didn't bother dying the epoxy black for this step.

Ya don't need big honkin internals for this...it's a short stubby rocket & I don't want the rear end turning into a boat anchor! These are just the size a stir stick [popsicle] makes & they are plenty. The big ones go outside....pulled with a 1in PVC section.




Finally.....just because.... I foamed the front 1/3 of interior. Just one mixing cup full poured in of 2 part foam. I did this because the front CR is several inches in front of fin tip, where as normally the CR is butted up to the front of fin & injecting "locks" everything in place. I used a bit of foam to do it. Since area in front of fins on MM is wide open, just pour in foam and it will rise around all the fins.... no need to pour between @ fin.
No need to foam the whole can either....just adds weight.

This is how much glue & dye I use for a set of external fillets.



Since it reaches the "gooey" stage first, I slip on my rear CR fill the 2 holes from the screws.
Then coat the inside of retainer groves.... very little is needed. Put that on with a twisting motion to evenly distribute the epoxy. Wipe off any excess with rag & alcohol.

Finally run a fillet around the CR to tube joint.




All the above took just the right amount of time for epoxy to reach the "stays put stage" & Now it's perfect for pulling external fillets. So.....that's what I do.LOL [with my 1in. diameter tool]


Any left over goes on to next set of fillets & continue on till all 6 are finished.:dark:

PS: don't know why it looks grey in some pics & black in others, but it's the same.... all deep black that matches the tubes

I noticed in your picture that you added the color to both parts of the epoxy before you mixed them. Is there a reason for this? I had been mixing together and then adding the color dye.

Rrwjr said:

I noticed in your picture that you added the color to both parts of the epoxy before you mixed them. Is there a reason for this? I had been mixing together and then adding the color dye.

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I put it in first ,just so I can tell when it's thoroughly mixed, by the consistency of color.When color is same throughout, no need to mix any more, your done!

Put it in last, & you have to mix it twice as long.
Guess I do it that way from years of mixing Bondo which you also tell is mixed correctly by color. I always squirt the hardener in several spots, rather than one.
Put in both parts cause it blends faster than a single pile of dye..... or so it seems.LOL

blackjack2564 said:

I put it in first ,just so I can tell when it's thoroughly mixed, by the consistency of color.When color is same throughout, no need to mix any more, your done! Put it in last, & you have to mix it twice as long. Guess I do it that way from years of mixing Bondo which you also tell is mixed correctly by color. I always squirt the hardener in several spots, rather than one. Put in both parts cause it blends faster than a single pile of dye..... or so it seems.LOL

Click to expand...

That makes sense to me. Sometimes it's those "little" things you see someone doing that's makes you question what your doing. Both give you the same results, but I like your thought process and your right you would only be mixing once versus twice. Thanks - I'm gonna try that way moving forward.

One of the reasons I like build threads with pictures is it allows you to learn and see new ideas if your looking at things with an open mind. Look forward to learning some additional tips/tricks from ya.

I finally painted this rocket so here is a finished shot. Flew it 2 weeks ago on a CTI 2-grain white.



Went 4590 RRC3
4589 RRC2+

Four flight so far and both altimeters have been within 10ft of each other!

There are 2 upcoming drag races featuring this rocket., ThunderStruck & URRF, so I thought I would bump up this build thread for those who may be getting one!

I've added a 18in drogue, since doing so, flights are absolutely perfect, with the fincan dropping straight below the NC av-bay containing the 40 in Re-Con chute. Flies straight and drops closer to the pad than any other rocket I have! Gotta love DD out of the nose cone.

Jim, would you call the "traditional" DD setup with an upper airframe section above the av-bay now evolved or replaced by something better with the head-end dual deployment?

Viperfixr said:

Jim, would you call the "traditional" DD setup with an upper airframe section above the av-bay now evolved or replaced by something better with the head-end dual deployment?

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Not replaced by something better, yes evolved......just another solution to do DD with short fat rockets or any extreme project where maximum use of minimum space is needed. Of course this is based on NC's with a removable shoulder/coupler. [all the newer spiral wound cones]

I am seeing Nose cone av-bays now being used in regular rockets i.e.,3 fins & NC, to eliminate the payload & coupler/av-bay completely, thus gaining more altitude & performance by simply using the coupler in the nose cone as the av-bay.

You eliminate weight and drag by shortening the rocket, but still can use simple DD techniques that have long been proven successful.
In other words it eliminates the new learning curve associated with cable cutters & chute cannons. Basically just moving the av-bay from one coupler to another, nothing really changes.

Payloads are here to stay as they will always be a great introductory into learning dual deploy & many rockets would not look right without them. They offer more space to utilize DD on a day to day basis. [my opinion only]

blackjack2564 said:

There are 2 upcoming drag races featuring this rocket., ThunderStruck & URRF, so I thought I would bump up this build thread for those who may be getting one!

I've added a 18in drogue, since doing so, flights are absolutely perfect, with the fincan dropping straight below the NC av-bay containing the 40 in Re-Con chute. Flies straight and drops closer to the pad than any other rocket I have! Gotta love DD out of the nose cone.

Click to expand...

I will have mine at URRF. Looking forward to the drag race. This will be my first with you. Mine will get it's first test flight this weekend (assuming the field is dry enough by then).

blackjack2564 said:

I've added a 18in drogue, since doing so, flights are absolutely perfect, with the fincan dropping straight below the NC av-bay containing the 40 in Re-Con chute. Flies straight and drops closer to the pad than any other rocket I have! Gotta love DD out of the nose cone.

Click to expand...

Jim, How long is your NC shock cord and how far back from the cone are you attaching the Recon? Just finished my build and was thinking about minimizing chances of entanglements. I'm thinking ~15' of cord with the chute a few feet outside the NC just like regular DD, but with a little extra to make sure chute gets pulled out clean.

I used 15 ft. Attached to the loop from the eyebolt in metal tip.

Loop tied in shock cord 2-3ft from the tip for chute. I used a 40in recon wrapped burrito style in a 14in nomex.

The excess shock cord is placed in front of the chute/burrito as to aid in getting chute out clean. I 've had 8 launches so far, & everything has functioned flawlessly.