12 fins and 3" of two stage good-ness

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Yoehahn

Yoehahn

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I ordered a two stage upgrade for my 3" darkstar today, and Ill be doing a build thread here. I will have a standard 3" DS as the booster, then a modified sustainer. The sustainer will have a 50"? body tube, for extra space underneath the fins for the interstage coupler. I did a mock up with two of the 3" darkstars I have lying around, and for reference I'm 6'3" tall.


photo-2.JPG





Ill post final specs when I get the box in from tims with the modified sustainer
 
I have spring break next week and Tim said I should get it in 2-3 days so ill update more then. I would add more but its really just speculation at this point. I do have a couple of questions tho if someone can answer them for me:

1: What rail size should I use? I have no tower, and this thing is freakishly long and tall so I want lots of support on this. The clubs I fly with have 6' 1010 rails and one or two 8' 1010's, while the 1515's are all 10' (maybe 12'.)

2: Should I add some aluminum rods in the interstage coupler to the sustainer? It might be unnecessary but I am not sure if Ill need the support or not. I will have at least 3" of coupler and 3 shear pins holding it in but I'm not sure if I will need more.

3: Is it better to use centrifuge tubes instead of glove fingertips for a more directional separation charge?
 
So I got my box, and washed everything and did a dry fit. This thing is massive and completely awesome!


First, a lot of parts:



image-2288598305.jpg



Then, the dry fit sideways



image-1090262217.jpg




And finally, the vertical test fit: it's a few inches over 11' tall



image-14758921.jpg
 
That's awesome! I also ordered a 2-stage upgrade kit (in black "carbonite") which I was planning to use with my 3" black DS...when I spoke with Tim earlier today and he asked if I'd like to have the new sustainer with matching DS split fins instead of the stock Wildman fins I said yes absolutely. So I guess I'm going to end up with exactly what you've got here. I was going to post some pics when I received the upgrade kit just to whet people's appetite but you beat me to it :)
 
beezwax said:
That's awesome! I also ordered a 2-stage upgrade kit (in black "carbonite") which I was planning to use with my 3" black DS...when I spoke with Tim earlier today and he asked if I'd like to have the new sustainer with matching DS split fins instead of the stock Wildman fins I said yes absolutely. So I guess I'm going to end up with exactly what you've got here. I was going to post some pics when I received the upgrade kit just to whet people's appetite but you beat me to it :)
Click to expand...

Well what you will end up with is:

20? feet of Tubular nylon,

2 lengths of kevlar strap (one short one long)

3 Quicklinks

1 3" FG Bulkplate (Av Bay)

2 wooden 54mm to 3" CR's (AvBay)

2 wooden 54mm bulk plates (AvBay

3 FG 54mm to 3" CR's (MMT)

A 3" interstage coupler

a 6? inch piece of 54mm FG Tubing (AvBay)

a longer mmt than stock

Fins

and the special cut body tube

I actually can't wait to build it/Fly it, its looking like Red Glare (which is 30 days away...) so I best get started. luckily though, No Painting!
 
Im thinking about making the booster MD with a removable motor mount (54)

On one hand, I would have more motor options and the motors would be cheaper, But on the other hand it also makes the rocket considerably weaker. Any thoughts?
 
Yoehahn said:
Im thinking about making the booster MD with a removable motor mount (54)

On one hand, I would have more motor options and the motors would be cheaper, But on the other hand it also makes the rocket considerably weaker. Any thoughts?
Click to expand...

Built my Wildman DD two stage with a MD booster and am also building my Ultimate Darkstar MD (Ultimate is going to fly an O25000). It is simple and inexpensive. I used ProLine epoxy for attaching the fins and the fillets. Everything gets tip to tip reinforcing with uni carbon fiber and fiberglass. Can always adapt down but when you want to put an L3200 in your booster, that will be quite difficult with a 54mm mount. ;)
 
I think I decided to just build it "stock" Because Im not going to pick up 75 hardware (unless some pops up here) until I have a rocket with a 75 mount. And on the east coast, I can already break the highest call-in waiver and there is only a $20-$30 difference between 75 and 54 in the smaller/bigger sizes respectively.
 
Yoehahn said:
I think I decided to just build it "stock" Because Im not going to pick up 75 hardware (unless some pops up here) until I have a rocket with a 75 mount. And on the east coast, I can already break the highest call-in waiver and there is only a $20-$30 difference between 75 and 54 in the smaller/bigger sizes respectively.
Click to expand...

I've got a 3" two-stager with 54mm motor mounts and you can do plenty of damage in that size. So, I think your decision is fine. Having said that, I also think that building a 3" rocket with thru-the-wall fins is one of the best ways I can think of to weaken a fin can.

Jim
 
JimJarvis50 said:
I've got a 3" two-stager with 54mm motor mounts and you can do plenty of damage in that size. So, I think your decision is fine. Having said that, I also think that building a 3" rocket with thru-the-wall fins is one of the best ways I can think of to weaken a fin can.

Jim
Click to expand...

Do you think the fin roots are too short to be worth anything?
 
Alright I decided to go the other way and do an MD 75- do you recommend carbon tape on the root or a full T2T layup? of Carbon
 
CarVac said:
Do you think the fin roots are too short to be worth anything?
Click to expand...

Well, my point was that cutting the airframe compromises its strength. In the attached pic, which is the bottom of my 3" two-stager, the body tube on both of the "top" two fins is cracked at the bottom, and the airframe is pulling away from the motor tube centering ring. I keep repairing it and it still works (because I did a pretty good tip to tip job to start with), but I'm gradually losing the battle. I prefer a strategy of surface-mounting fins and then making the fins and airframe into an integral unit using relatively large fillets and tip to tip. With that approach, I don't have many problems with fins. Looking closer here though, with the split fins, I'm not sure that the large radius approach would be very aesthetic. I've never done split fins though.

Jim

DSCF0117.jpg
 
Last edited:
I am now the proud owner of a CTI Pro 75 3 Grain case, and an L910 For the booster of this project. I will probably light a 38mm I or J in the sustainer to get to about 15K at Red Glare
 
Today I got the retainer installed, the CR's installed, and I will be putting in the first set of fins today. I also finished the interstate coupler, now I just need to focus on the av bay. Ill take pictures in a few minutes
 
I got the booster finished minus fillets (starting now) and things are going well

image-3249810183.jpg
 
I finished the sustainer MMT, retainer included. I'm going to fillet/cover the all thread with JB Weld next.

image-2203522375.jpg



image-1367036182.jpg
 
Alright Ill take some pictures soon, But I flew this twice at Red Glare (saturday and sunday). on Saturday, I flew it on an AT I600R to a CTI I140SK to 2202'. The Entacore AIM USB in the Booster did NOT fire the apogee charge (unsure why as of yet) but fired the main, and the Raven 3 in the sustainer staged the motor beautifully, fired the apogee charge, but a short in the wiring prevented the Main from being deployed. I picked up everything and started getting ready for another test the next day before I put it up on the K590 Dual thrust to J380SK to 15,000'. I fixed the av bay, and then put it on the rail late in the day. I loaded up another I600R, and another I140SK, and burned through the igniter. I put in a home made igniter (more oomph) and tried it again. This time the rocket went up, and right before the end of the burn the I600R CATO'd, sending the booster into the sustainer snapping off two of the fins. Luckily, I added more safety checks to my Raven so the I140SK did NOT fire, and the rocket was recovered in pieces. I will be repairing it this week, And I am looking forward to next MDRA launch so that I can try it a third time!

I would like to take this moment to thank Karl at Aerotech, I brought by my casing, he asked a couple questions and took a look at the remains, then walked over to Tims Trailer and replaced my I600R on the spot! Thats customer service right there, I really appreciated them fulfilling the Warranty.

Pictures to come soon.
 
Yoehahn said:
Alright Ill take some pictures soon, But I flew this twice at Red Glare (saturday and sunday). on Saturday, I flew it on an AT I600R to a CTI I140SK to 2202'. The Entacore AIM USB in the Booster did NOT fire the apogee charge (unsure why as of yet) but fired the main, and the Raven 3 in the sustainer staged the motor beautifully, fired the apogee charge, but a short in the wiring prevented the Main from being deployed. I picked up everything and started getting ready for another test the next day before I put it up on the K590 Dual thrust to J380SK to 15,000'. I fixed the av bay, and then put it on the rail late in the day. I loaded up another I600R, and another I140SK, and burned through the igniter. I put in a home made igniter (more oomph) and tried it again. This time the rocket went up, and right before the end of the burn the I600R CATO'd, sending the booster into the sustainer snapping off two of the fins. Luckily, I added more safety checks to my Raven so the I140SK did NOT fire, and the rocket was recovered in pieces. I will be repairing it this week, And I am looking forward to next MDRA launch so that I can try it a third time!

I would like to take this moment to thank Karl at Aerotech, I brought by my casing, he asked a couple questions and took a look at the remains, then walked over to Tims Trailer and replaced my I600R on the spot! Thats customer service right there, I really appreciated them fulfilling the Warranty.

Pictures to come soon.
Click to expand...

Plug in the AIM USB to your computer and check the settings. I cant wait to see the pictures and videos.
 
Yoehahn said:
I did and it turns out that the battery had dropped to 2.6 volts (that would do it)
Click to expand...

Figures, you got to watch out with those batteries :p. I always checked them making sure they weren't dying on me lol. I cant wait to use the AIM USB 3 on that single cell LiPo battery I bought for $10.
 
I was using a brand new Duracell 9V, I guess I gotta check them out of the box from now on
 
Yoehahn said:
I was using a brand new Duracell 9V, I guess I gotta check them out of the box from now on
Click to expand...

Yeah watch out for that from now on and that is why I now recommend to you using LiPo rechargeable batteries :). They last longer and you can get them cheap at Hobby King. Which version of the AIM USB do you have 1.3, 2.0, or 3.0?
 
SinfulDarkLord said:
Yeah watch out for that from now on and that is why I now recommend to you using LiPo rechargeable batteries :). They last longer and you can get them cheap at Hobby King. Which version of the AIM USB do you have 1.3, 2.0, or 3.0?
Click to expand...

I have the 2.0 and can you send me a link?
 
Some pictures:
IMG_0098.jpg

IMG_0099.jpg

And the first flight on the I600R to an I140SK (Photos by Nick Debrita- Thanks Nick!)

8658807269_1a404a0256_o.jpg


8659909956_c9ee3cb799_o.jpg


I have more pics of construction if anyone is interested as well. And Ill have some more, currently the rocket has no fins :cry: poor baby.
 
nice skidmark ignition, what happened to the fins? Also did the battery recommendation work?
 
SinfulDarkLord said:
nice skidmark ignition, what happened to the fins? Also did the battery recommendation work?
Click to expand...

Haven't tried the battery yet, and on the second flight on sunday the I600R Blew the Forward closure, the booster rammed into the sustainer and everything came down violently because the chutes couldn't open in the 114' altitude that I hit. I have a crappy video here that kinda lets you see what happened, I have a better one that I will upload later today. When I picked the rocket up, the interstage coupler was broken and every damn fillet on the whole rocket was cracked so I hammered the fins out and am sanding the tubes now. Problem is, the tubes are to scratched up now so I gotta paint em'. Its a damn shame really.

[video=youtube;YSba6ScSXS0]https://www.youtube.com/watch?v=YSba6ScSXS0&[/video]
 
Any chance you could post more detail on your inter-stage coupler? It looks far different from anything I have seen.

Also, How'd the motor retention work out for the sustainer? I assume good? I've always wanted to try using this method.
 

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