Foamy Jupiter C

Ok, I'm going to try one more time to see if I can make a 7" diameter rocket that still meets far 101 weight....I'm on track so far. Decided on a Jupiter C.

I've got it framed up and am working on the stringers now. I decided to use a 29mm stuffer tube with a 3" pml upper section for the parachute. I'll build up the outer diameter to simulate the second stage can, and that same 3" tube goes down into the transition as well and I'll build up and sheet that. The diameter at the second stage can where the transition hits it is oversized since it is the 3" tube but this is standoff scale.

Like my hellfire I'm trying to use depron structure and sheeting for fins etc to keep the weight down.

It will be 7" diameter and 82.5" long so 1/10th scale. The satelite is also slightly oversized using bt-20 and a bt-20 cone since that's what I had, it should really be .6" diameter. Only the satelite and a small coupler section that goes into the second stage can will eject. Altimiter will be installed, not sure if I can make far 101 with the altimiter onboard or not.

Target weight rtf less motor is 48 oz or so.

I'm not probably going to fly it much on G motors with only 4-500 feet expected altitude, but I'd like to see if I can make it. I wanted to make it strong enough for robust 29mm H motors as well, and not be stuck flying on small motors. Funny thing is single use G80 and G75's are more expensive than H-128 reloads by about 4-5 dollars.....

Frank

Sweet!
Best of luck on the Weight thing.

That is absolutely amazing. Great workmanship! Good luck with the project and please post updates.

Went to the craft store and found a funnel the approx size I needed and trimmed it to fit the base of the satellite. Made the cap to go on the nose portion, then sheeted the second stage. Working on the transition sheeting now. The nose portion that ejects is basically a 3" coupler piece with a ply cap for the screw eye to attach, then the foam and tube structure on top of that.

Frank

Finished sheeting the transition, and added a bit of trim monokote to the satellite.

This is exciting Weight is really close. Good news is that the CG seems to be right on where I need for 1.1 caliber stability or better with G-80's or G125's, if I use an H135, H128 or H97 and add the altimeter I still have 1 caliber, so no needed balast so far.

Frank

Some more photos, showing the lower internal structure before adding it on the center tube, the forward centering rings and parachute attachment, some reinforcing for the middle rail guide attachment, and some of the altimeter bay area. There will be an access door to insert the altimeter from the top into the tube, then an aluminum tube going through the centering rings into the parachute compartment will allow me to route the charge wires.

It's ready for the skinning now and building the fins.

Frank

Another terrific model! Obviously, you know depron can really crank these items out quickly. What tools do you use to cut the depron including the circular sections?

Over the years the original Jupiter C has grown on me partly for nostalgic reasons. It was an exciting time in US space history.

On a different note what marking tool do you use for your profile models to trace your patterns on to depron?

That's so cool. I managed to stay on G power of my 8" x 6' V2-like rocket...but failed on my Redstone. That requires an H.

I'd like to see your redstone and V-2 do you have any thread links or photos? If you are using one of the smaller H motors, like an H-128 you can still get away with far 101.....

I see a couple of places where I could have saved a few ounces, I don't really need eye bolts, I could have glued the kevlar to the tubes/centering rings directly, that would have saved an ounce and a half. I could have done away with the retainer ring, that's a half an ounce, and could have saved a few ounces using lighweight cardboard tubing for the 29mm and 3" stuffer tubes instead of phenolic.

rstaff3 said:

That's so cool. I managed to stay on G power of my 8" x 6' V2-like rocket...but failed on my Redstone. That requires an H.

Click to expand...

I use a fine line sharpie pen and a light touch to not score the surface, I can use CA setting spray to remove it without harming the foam if I need to.
I just use an exacto for cutting the pieces. For the centering rings, I cut a 3/32" ply thrust plate for the rear and one for the top to attach the recovery harness to, I just used one of the ply plates as my template and just cut around it with the exacto for the inner and outer holes, made quick work of it. For the slots, I made a template out of foam and then just used that as a guide to cut all the slots in both the centering rings and the longerons.
One nice thing with the depron is that is cuts and sands so quickly it doesn't take any time to make and fit parts. Pretty much as quick as you are able to exacto them out and glue them in. You can cut them slightly oversized or cut the slots slightly undersized and press fit them in place to make a good joint, I've got a pretty good eyeball now for hand cutting 6mm slots and tabs....If you get a tight fit you can just use thin foam safe CA in the joint and you don't need to use as much glue as if you were trying to fill a loose fit.

Frank

aerostadt said:

Another terrific model! Obviously, you know depron can really crank these items out quickly. What tools do you use to cut the depron including the circular sections?

Over the years the original Jupiter C has grown on me partly for nostalgic reasons. It was an exciting time in US space history.

On a different note what marking tool do you use for your profile models to trace your patterns on to depron?

Click to expand...

Sure thing. It appears you are doing a better job of costruction, but here goes:

V2-like Grand Whazoo: https://rocketdungeon.blogspot.com/2010/12/review-grand-whazoo.html

Too Rollin Red-Stoned: https://rocketdungeon.blogspot.com/2010/12/review-too-rolling-redstoned.html

The Redstone suffered from a minor flood in the basement. I've scavenged it and would like to build a Little Joe out of the parts.

Those are really neat. One advantage to using the cardboard skin is it is load bearing and you don't need to use the stringers, my total foam weight is around 15 ounces. Most of the weight is in the recovery system, 5-7 oz, stuffer tubes, 14 oz, and motor, 4-9 oz, carbon fiber, glue and ply, retainer and eye bolts 9, and some misc here and there. Advantage in the depron is that there isn't any water problem so you don't have to clear coat or paint if white is ok.

Got some little magnets at the hobby shop and took a few minutes to build my hatch. This is similar to what I did for my hellfire and X-20 stack, with some internal structure and sheeting, idea is the hatch will help keep the altimeter cap in place when closed. The aft end of the hatch needs a cutout to clear the deployment charge wires coming out the top of the cap, to the right end of the bay you can see the epoxy blob that is right next to where the conduit is to route the deployment charge up into the parachute tube.

Finished the sheeting, now have to build the fins, and do some of the details.....I think I'm going to be an ounce or two over, my particular 2mm sheet was just a bit denser than the online spec...but stay tuned.

Here is the openrocket file and a picture of the structure/sim



View attachment redstonefoam.ork

burkefj said:

Finished the sheeting, now have to build the fins, and do some of the details.....I think I'm going to be an ounce or two over, my particular 2mm sheet was just a bit denser than the online spec...but stay tuned.

Click to expand...

Looks great! Your construction method is much nicer than mine, which is basically craft store junk.

Made a few little details.....

Did a few monokote trim markings to start with...

Got one fin built and installed. On this model I skipped making a fin box since the fin tabs are slotted for the centering rings and once installed complete the stringer to the rear thrust plate. The downside of that is that the skin is unsupported once you slot it and until the fin is glued in, I found that by adding 3/16" strips along the fin at the root it helps to push down the skin flat to hold it in place for gluing. I used a bit of styrene sheet to reinforce the rear ends that will take landing punishment, the fin has a 3/16" carbon spar angled through to the root as well.

Frank

Got some free time today to finish the fins, and slot them, all up weight right now is at 46.5 oz, very close, still need to verify the parachute/kevlar line weight, that's on order. I'm pretty pleased I'm this close. With the altimiter included, my CG is an inch and a half forward of where I need for stability with a loaded motor in place...so I shouldn't need nose weight for the larger 29mm motors.

Frank

Really impressive work. I have enjoyed your foam builds, and not a method I had considered prior to seeing them. Always good to learn something especially from someone who clearly has the method down.

Thanks, the method is evolving, little things here and there.......

Here she is painted with some sharpie detailing...just waiting for the chute/kevlar to attach the forward section permanently and do a balance check.

Frank

Wow!!!:clap:

For something thats not going to glide, this sure is awesome!!

What motors you planning here? Too bad a G40 won't have the oomph for this wt/drag, that would have looked great going up. Too bad you didn't decide on an H45 and 'sorta steering' on the way up if needed....

Mike, it was a tradeoff. Active control would have added weight in the rear end. The H45's and similar motors didn't have enough thrust off the pad to give me a velocity to launch without guidance in wind more than about 5mph. I also wanted to be able to fly it on larger motors. With the diameter and the draggy nose, the low thrust longer burn motors don't really get all that high, the CTI H42 is a good examply, only 27fps off the rail and 620 feet, H97 gives a similar altitude with a 47fps off the pad. I really thought about the I59, which meant I would have to go with a 38mm lower stuffer tube. Unfortunately I would have to also use an adapter in the rear end for small 29mm flights. That would add another 2 oz to the tail and 2.5 oz to the nose, and I really was down to the gram to make far 101 weight so chose not to.

There are still a lot of motors to use: Here is a snapshot from the sims. The G75 and G80 assume two ounces lighter without the altimeter pod installed. most of these motors give me near 50fps or better off the rod and 1.1 to 1.3 caliber of stability, the few that are right at 1 give me 60fps or better.
I'll approach the bigger motors in progression, I haven't flown anything with a foam structure past about 250fps so want to be sure it holds up.
This is based on openrocket barrowman, rocksim equations show cp 5 inches further back, so I probably have extra stability margin for wind.

AstronMike said:

For something thats not going to glide, this sure is awesome!!

What motors you planning here? Too bad a G40 won't have the oomph for this wt/drag, that would have looked great going up. Too bad you didn't decide on an H45 and 'sorta steering' on the way up if needed....

Click to expand...

One thing astute readers may notice is that the little details on the bottom are off by 90 degrees....My rockets of the world drawings did not show clearly where they were on the drawing with the paint markings. In any case where I assumed they would go was thwarted by my pre-planned location for the launch buttons, since these had to be built in before skinning. I found they would interfere with the lower button so moved them one bay over which put them in the "black" painted portions, not in the white like they should have been, I know, I'm so lame.....I could have chosen a different orientation for the "front, but I wanted the rail buttons to be in the back on the seam.....oh well.

I had the maiden flight on an H-128 today. 3.5 pounds ready to fly. Just perfect dead straight flight, didn't even arc over, started a tail slide and the nose popped like a champaign cork. No damage perfect recovery. Flight recorded 500' altitude. Excellent!

Terrific project, Frank! How long is your rail? Do you think a shorter rail will work? Do you have any flight photo's.

Here is the flight video. Rail is 12', two 6' lengths with splice plates.

An 8' rail would probably be fine but I had the long rail for the dyna-soar titan stack so I used it just to give extra exit velocity..

https://www.youtube.com/watch?v=Ao8DZ2jO8nw