Lil Rascal HED build

Wayco said:

You haven't even flown it yet? OK, I will go back and edit my post.
I'm not trying to pick on you, you're absolutely correct, that "Super Thunder" motor will spank this little rocket! How much does yours weigh in at?

I don't usually adapt down for smaller cases, a 54mm MMT deserves the biggest motor you can put in it, but that's just the "Wildman" in me...

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Yeah I don't typically adapt down but I have been dying to try this motor. It has not flown but will in October. It weighs in at about 4.1 pounds.

DizWolf said:

I do mini magg's on G's all day long. a 6:1 isn't underpowered. Hell I'll launch at 3:1 The thing wasn't stable because the rear is a glue bomb.

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So I guess I can't convince you to put a 3 grain "K" in it? Dang, that would be fun to watch! might help with the stability too...

LOL, it certainly would. Though I generally stick them in longer rockets.

Wayco said:

You think adding nose weight would have helped that? Not following that logic.

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didn't say adding nose weight, just more stability... I do appreciate all the input. good stuff...

so while trying to figure out the best way to fit a 3 grain in there, what would you say is the min insertion length for the coupler? It is 6" long and 2" goes into the nose, which will be pinned with 3 2-56 nylon screws. I'm going to add a switch band so if I go with 1" that leaves 3" in the body, which is ok, but what about 2" in the body? it's not like this is a big long rocket, think 2" is enough to friction fit the coupler into the body tube with a 12" long nosecone and a 2" band? seems kinda short to me but we're only talking about 14" of rocket on each side of it....

Just the tip is always safe.

DizWolf said:

Just the tip is always safe.

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says the man with 3 kids under 3....

RKeller said:

says the man with 3 kids under 3....

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No connection. Stork brought all those.

Got some more done tonight, printed out the fin guide on 11x17 paper, used the kids glue stick to glue it to thin cardboard from some toy thing, and cut it out.

then I injected some JB weld through the slots onto the motor tube and front centering ring.

I warmed JB weld by putting the tubes in a baggie under some hot tap water. this lets it flow a lot more so it can run down and form internal fillets.

This is where I always fail with pictures. I like to do lots of steps at once so I forget to take pictures. once I stuck the fins in I injected JB at each joint letting it run all the way down to the front centering ring. I use a stick when needed to move the JB weld around. This time I had to be careful not to get it on the body tube beyond where the external fillets will be because it will show. once I'm happy with the fillets I glue on the rear centering ring and retainer. then use rubber bands to hold the fins in tight while it all cures.

RKeller said:

says the man with 3 kids under 3....

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DizWolf said:

Just the tip is always safe.

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Man, that's the funniest thing I've read on this forum in a while.

time to decide how long of a switch band to get...

Once I saw a pie-tin (pot-pie) fly, as well as spools fly, I decided I didn't really understand dynamic stability like I once thought I did...

GREAT lookin' rocket regardless! I always feel bad about my fillets <sp?> making the rest of the rocket look bad. I can hide haze and bubbles under paint.

Wayco said:

Sharon and I were kicking this whole "3 grain" idea around this morning, so I got up and stuck a 3 grain casing in my Lil Rascal and measured it. It's 2" from the top lip of the body tube. My coupler extends 2" down into that same tube, but the aft bulkplate is recessed 2" up into the coupler, leaving me some space for the drogue shock cord and "burrito" main chute tied off with a cable cutter. When I stuff all that in, the burrito is crammed into the coupler. Not much chance that the ejection charge will pop it out, so even when the cable cutter severs the zip tie, the chute might be trapped in the coupler.
Sharon has this kit unbuilt, and even though we both think that a 2 grain reload is plenty enough for it, more is always better, right?
Leaving the coupler 2" into the body tube seems to be working, so we will leave it there, and recessing the aft bulkplate will leave plenty of room for a shock cord, but if you made your top bulkplate removable and mounted your altimeter and battery in the 4" space between them, you could pack the main chute in the nosecone, which is what you planned to do anyway, right? A 1" switch band would keep the coupler from sliding around under boost, and friction fit or shear pin the fincan and nosecone to it. Glue the bottom bulkplate in the coupler and access the avbay from the top. Even with the forward closure sticking up 1/2", there would be plenty of room for a charge cup and eyebolt on the recessed bulkplate.

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That's exactly what I plan on doing, my 6" coupler goes 2" into the nose, so I think I'll get a 1.5" or 2" band leaving 2.5" or 2" of the coupler to go into the body tube. recess the bottom bulkplate a couple inches to make room for a 3 grain then buy a stepped bulkplate for the top. a 4x4" ebay is enough room for a couple altimeters and an eggfinder with an external antenna. a topflite chute and cord should fit fine in the nose. should be slick. and I agree, 2 grain will be plenty but why limit your options?

used up lots of tape and rocketpoxy today...

This project has been sitting for a while, but I'm back at it. I ended up going with a 2" vent band and recessing the aft bulkplate 1" making room for a 54mm 3g CTI and 1280 AT case. here's the av bay, which is not done yet. I still have to drill the three vent holes but I'm waiting till I know where the screw switches will be...
I had to bevel the edge of the bulkplate so it didn't stick in the nosecone

The other side, I'll have to plug that hole in the middle and add an eye bolt off to the side to make sure there is room for the motor.

rocketpoxy fillet on the inside

all the parts

what it looks like


The nose is drilled and tapped for 3 2-56 nylon screws. the coupler to body tube will be friction fit. inside will be an eggfinder TRS and a TBD backup altimeter.

Try a 1/4" tie rod end from McMaster instead of an offset eyebolt.

patelldp said:

Try a 1/4" tie rod end from McMaster instead of an offset eyebolt.

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well if I want to fit 3 grain motors, which I do, I won't have room for anything in the center hole. I do have a couple feet of 3/8 kevlar so I could drill a couple holes and use a loop of that instead of the eye bolt.

still debating with myself regarding how much weight to add. adding no weight = 0.2 cal stability. if you add a 3:1 0 mass nosecone to simulate base drag stability goes to 1.0. this picture is with 8oz in the nose which is what I think I'm going with. stability is around 0.5 to 0.6 depending on the motor and ~1.3 with the base drag.

got all the doohickeys and wires and battery things mounted...

I added 4oz to the nose. to attach the weight and shock cord I drilled a hole into the epoxy tip inside the nosecone and tapped it with 1/4-20. I found a 1" piece of brass rod and cut it to 1.25" long and drilled and tapped that for 1/4-20. threaded that onto a long eye bolt and screwed it all into the nosecone.
here it is in the nose


also did some ground testing. I calculated I needed 0.7g of BP in the nose and around 1g for the body tube. testes went well. pulled the 20ft 1/4" kevlar shock cords mostly straight but did not pull out all the z folds that were taped up.
[video]https://goo.gl/photos/orUeiaMKJyvE6dCv5[/video]
[video]https://goo.gl/photos/SFWuixdiDTMaoK6TA[/video]

RKeller said:

testes went well. pulled the 20ft 1/4" kevlar shock cords mostly straight but did not pull out all the z folds that were taped up.

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Your testes really pull their weight.... Only "mostly straight?" Careful with that not pulling out thing.

Ha ha ha! this is my first HED. guess I got a little excited.

DizWolf said:

Your testes really pull their weight.... Only "mostly straight?" Careful with that not pulling out thing.

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I literally just cringed reading that.

RKeller said:

Ha ha ha! this is my first HED. guess I got a little excited.

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Today, you win the internets.

ROTFLOL!

first flight, CTI I212 Smokey Sam to 1800ft. super windy but it flew great! Thanks Dizwolf for the great pictures!

so this is why they tell you to use a drogue on HED... totally forgot to, I never use a drogue. next time I will. I haven't pulled the data off the TRS yet to see how fast it came down.

Forgot to update this thread...
2nd flight was black friday on an AT I435. great flight to around 3500ft. got there in a hurry!
[video=youtube;VRcJqBYyF_s]https://www.youtube.com/watch?v=VRcJqBYyF_s&feature=youtu.be[/video]

Then April 23rd I added a few more ounces to the nose and put it up on a J145 skidmark. that was an awesome motor!

That was a cool flight. Interesting idea you've come up with for this kit next.....