First HPR build log. L1+

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
Hi everyone. Here is my attempt at a build log!

I’m going to do a scratch build as my first high power rocket. Constructive feedback and advice are very welcome.

The Plan

3” diameter, split fin, configurable booster-only/dual-deploy for future tinkering
MAC canvas phenolic custom kit, tubes, e-bay, fins, etc
38mm motor mount

I’m designing a rocket that I can launch on G motors here at “home” in a single deploy configuration that I can use for my level 1 certification. It will be designed such that I can add dual-deploy down the road.

I’ll launch it a few times at my local launch site on G motors to make sure it holds up, practice my checklist discipline, parachute packing technique with the JLCR, etc. Then I’ll do a level 1 cert in the single-deploy config. After I get some experience like this, I’ll start tinkering with adding electronics for a dual-deploy.

It’s quite the engineering challenge to make a rocket that is stable in both configurations and with various sized motors, but I love a good challenge.

The Design

I love the look of split fin so I’m starting with that. I’m going with 3” diameter to keep the altitude down a touch and give me room to work with inside the rocket. I want a waterproof rocket since my home field (about 2,500’ square) has a pond as the bullseye and I also have no desire to fill spirals. That left me with Quantum Tube, Canvas, or Fiberglass. I chose canvas as a good balance of weight, strength, altitude, etc. and I’ve heard nothing but great things about the fit and finish of MAC kits. Mike makes it easy by essentially building out a full custom kit for my design. Awesome.

Decision point: Head-end-dual-deploy (HEDD) or traditional DD?

In the traditional dual-deploy design, my primary concern is “over stability.” I’m not sure how much is too much. In the booster only config, the rocket is stable at about 1.3-1.8 cal with all intended launch motors G-H. After I add the payload section for the dual-deploy configuration, the rocket gets a lot longer and the stability number goes up quite a bit and I’m not sure how bad it is to be in the 3+ cal range, besides the obvious exaggerated weather-cocking effect. There’s not a good way around this as the added length and weight of the payload section just naturally moves the CG forward and the fin size/shape is bound by the stability in the stubby config.

Alternatively, I’m highly considering a HEDD design. I’m already planning to use a Wildman FWFG nose-cone (need the extra weight up there for either design) that’s about 17 inches long and I think is used in the Punisher 3 kit as a HEDD, so a chute should fit in there no problem. If I went this route, I’d avoid most of the problems with trying to make a short rocket stable but then having a long rocket that is over-stable since with HEDD, the rocket dimensions would be virtually the same whether I use dual or single deploy. However, this means there will be less of a weight different between my two configurations so less motor flexibility. It would end up a bit heavier even in the lightest configuration and therefore a little harder to pull off a G motor at home. I think I can do it by removing the e-bay entirely and just using the nose-cone in the traditional manner with a piece of coupler as the shoulder. I’d pin the coupler/shoulder in through the same holes that I would use for shear-pins in the HEDD mode.

Attached are some screengrabs and files of OpenRocket for both designs. Let me know what you think. I’m partial to the HEDD design currently.

Motors

Surprisingly, I haven’t seen that much about CTI vs ATI reloads. From what I can gather, CTI reloads look simpler and that appeals to me, but all of them require haz shipping fee. Some ATI G and even H reloads can be shipped without haz, which is a big plus, but they look more complicated to assemble. Right now, I’m leaning towards a CTI 38mm 3-grain case with 2 spacers. I could always buy single-use or DMS/loadable Aerotech G or H motors if I wanted. I’ll also probably pick up a 38 to 29mm adapter to fly some single-use 29mm motors.

More to come!
 

Attachments

  • HEDD in dual mode.PNG
    HEDD in dual mode.PNG
    297.9 KB · Views: 36
  • HEDD in single mode.PNG
    HEDD in single mode.PNG
    324.2 KB · Views: 31
  • DD in dual mode.PNG
    DD in dual mode.PNG
    353.7 KB · Views: 29
  • DD in single mode.PNG
    DD in single mode.PNG
    354.3 KB · Views: 25
  • 3 inch canvas HEDD Single.ork
    3.5 KB · Views: 3
  • 3 inch canvas HEDD.ork
    3.6 KB · Views: 2
  • Scratch Built 3 inch_v3_LONGConfig CTI Motors.ork
    4.6 KB · Views: 1
  • Scratch Built 3 inch_v3_ShortConfig CTI Motors.ork
    771.3 KB · Views: 2

thzero

Well-Known Member
TRF Supporter
Joined
Jun 4, 2018
Messages
630
Reaction score
369
Yes, the Aerotech are more complex to assemble. Being newer to mid/high power like you I've only started assembling them myself recently but have several flights under the belt. Once you get the hang of it, and follow the instructions they go together pretty well.
I am getting some CTI reloads at Midwest power so, look forward to trying their system too.
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 4, 2018
Messages
630
Reaction score
369
Thought about using a Jolly Logic Chute Release to do some dual deploy to start with? I use mine for a bunch of F-G launches, and even used it on my Level 1 on an H.

That is a honkin' big nose cone, and without a bigger engine acting as a counter balance, yeah your CG is going to shift forward as you add more tube.
 

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
Thought about using a Jolly Logic Chute Release to do some dual deploy to start with? I use mine for a bunch of F-G launches, and even used it on my Level 1 on an H.

That is a honkin' big nose cone, and without a bigger engine acting as a counter balance, yeah your CG is going to shift forward as you add more tube.

Yeah I have a JLCR and am planning to use it initially will likely use it for my L1 as well.

The big heavy nosecone is kind of required to keep the stubby version stable. Otherwise I need nose-weight, so might as well just have a nice fiberglass nose-cone instead.
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
5,246
Reaction score
4,503
If it was my rocket, I'd go with a plastic nose cone and traditional dual deploy. That would give a little more room in your weight budget. At 1300g loaded weight in the initial sim, you're perilously close to the magic 1500g limit for flying without a waiver next door. 200g can disappear in an instant once you start adding fillets and other stuff back aft.

Given the choices, I'd make the fins a bit bigger and maybe the booster a little longer to get stability with G and small H motors. That should get you to reasonable stability margins with a little less weight. Take that with a grain of salt*--I've never flown HEDD, so I like to go with what's familiar. You can also fly the full version single deploy--just put the main in the booster and pin the upper section all together.

When you're looking at stability for the full versions, check what it looks like with the full range of 38mm motors. If it comes down to 1.5-ish calibers on a full I or baby J, then it's just about right. If it's not quite stable enough, you'll want to add some fin area. You would then make decisions about what configuration to fly in based on conditions. If it's totally calm, an overstable flight isn't as big a risk. I'm also less concerned about overstability than most people because one of my favorite flyers has about 5 calibers of stability. Flies great, too!

If the club you'll launch HPR with has a vendor, go with what they stock. You can also save on hazmat fees by stocking up when you're at the HPR launch. Me, I love CTI for ease of use and variety of propellants, but people also love their Aerotech and Loki.

* Actually, take all of this with a grain of salt--it's your rocket after all! 😀
 

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
* Actually, take all of this with a grain of salt--it's your rocket after all! 😀

I appreciate the advice! A lot of things to consider for sure. Yeah I was worried about 1500g, so that's a definitely a factor.
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
8,145
Reaction score
681
Location
Stafford, VA
If you are building this for an HPR rocket with a 38mm MM, that is for H & I motors, why are you concerned with the 1500g limit and flights on G motors?

I would just build it to fly well on H & I motors and stick with that. I also wouldn't bother with dual configurations. Just build it for dual deploy.

I built one rocket with dual configurations like that. 3" diameter with 38mm MMT. I've flown it over 30 times and only the first flight was in the non-DD config. I wouldn't bother doing that again because the DD config was so much better and more fun to fly with H - baby J motors.

BTW, when I designed that one, for stability I had a plastic nose cone for the DD version and a weighted nose cone for the non-DD version. Using two nose cones was the easiest solution for stability in dual configurations.
 

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
If you are building this for an HPR rocket with a 38mm MM, that is for H & I motors, why are you concerned with the 1500g limit and flights on G motors?
Thanks for the feedback.

Yeah I'm kind of realizing this as well. I ended up changing the design a bit, going with the HEDD and ordering it from MAC. I came to the same solution as you and ended up ordering two nose cones to solve a bunch of issues.

I bought two plastic NCs and I'll modify one by cutting off the rear shoulder cap and epoxying a small centering ring deep into the nose cone that has threaded inserts or T-nuts around the perimeter. Then I can screw in a bulkhead that has an eyebolt attached. Gives me the option to remove it easily when it needs maintenance. Then I'll likely epoxy a short section of airframe tubing, maybe around 5" for 3" exposed, to the nosecone shoulder so essentially the nosecone and payload bay are one piece. So that'll slide right onto the AV-bay/coupler and be held in with shear pins. That's the experiment for the future anyway.

I'm going to fly it single deploy on G motors at my local field to get some experience with it, keep it down around 800-1000 feet, then I'll probably end up cert'ing single deploy with a ChuteRelease.
 

Ganji

Member
Joined
Oct 29, 2020
Messages
10
Reaction score
0
Hi everyone. Here is my attempt at a build log!

I’m going to do a scratch build as my first high power rocket. Constructive feedback and advice are very welcome.

The Plan

3” diameter, split fin, configurable booster-only/dual-deploy for future tinkering
MAC canvas phenolic custom kit, tubes, e-bay, fins, etc
38mm motor mount

I’m designing a rocket that I can launch on G motors here at “home” in a single deploy configuration that I can use for my level 1 certification. It will be designed such that I can add dual-deploy down the road.

I’ll launch it a few times at my local launch site on G motors to make sure it holds up, practice my checklist discipline, parachute packing technique with the JLCR, etc. Then I’ll do a level 1 cert in the single-deploy config. After I get some experience like this, I’ll start tinkering with adding electronics for a dual-deploy.

It’s quite the engineering challenge to make a rocket that is stable in both configurations and with various sized motors, but I love a good challenge.

The Design

I love the look of split fin so I’m starting with that. I’m going with 3” diameter to keep the altitude down a touch and give me room to work with inside the rocket. I want a waterproof rocket since my home field (about 2,500’ square) has a pond as the bullseye and I also have no desire to fill spirals. That left me with Quantum Tube, Canvas, or Fiberglass. I chose canvas as a good balance of weight, strength, altitude, etc. and I’ve heard nothing but great things about the fit and finish of MAC kits. Mike makes it easy by essentially building out a full custom kit for my design. Awesome.

Decision point: Head-end-dual-deploy (HEDD) or traditional DD?

In the traditional dual-deploy design, my primary concern is “over stability.” I’m not sure how much is too much. In the booster only config, the rocket is stable at about 1.3-1.8 cal with all intended launch motors G-H. After I add the payload section for the dual-deploy configuration, the rocket gets a lot longer and the stability number goes up quite a bit and I’m not sure how bad it is to be in the 3+ cal range, besides the obvious exaggerated weather-cocking effect. There’s not a good way around this as the added length and weight of the payload section just naturally moves the CG forward and the fin size/shape is bound by the stability in the stubby config.

Alternatively, I’m highly considering a HEDD design. I’m already planning to use a Wildman FWFG nose-cone (need the extra weight up there for either design) that’s about 17 inches long and I think is used in the Punisher 3 kit as a HEDD, so a chute should fit in there no problem. If I went this route, I’d avoid most of the problems with trying to make a short rocket stable but then having a long rocket that is over-stable since with HEDD, the rocket dimensions would be virtually the same whether I use dual or single deploy. However, this means there will be less of a weight different between my two configurations so less motor flexibility. It would end up a bit heavier even in the lightest configuration and therefore a little harder to pull off a G motor at home. I think I can do it by removing the e-bay entirely and just using the nose-cone in the traditional manner with a piece of coupler as the shoulder. I’d pin the coupler/shoulder in through the same holes that I would use for shear-pins in the HEDD mode.

Attached are some screengrabs and files of OpenRocket for both designs. Let me know what you think. I’m partial to the HEDD design currently.

Motors

Surprisingly, I haven’t seen that much about CTI vs ATI reloads. From what I can gather, CTI reloads look simpler and that appeals to me, but all of them require haz shipping fee. Some ATI G and even H reloads can be shipped without haz, which is a big plus, but they look more complicated to assemble. Right now, I’m leaning towards a CTI 38mm 3-grain case with 2 spacers. I could always buy single-use or DMS/loadable Aerotech G or H motors if I wanted. I’ll also probably pick up a 38 to 29mm adapter to fly some single-use 29mm motors.

More to come!
How do u connect the nosecone so it won’t fall out while deploying 1st chute but it will fall out when the second chute is being deployed ?talking about DD
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 4, 2018
Messages
630
Reaction score
369
Shear pins.

 

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
Little update.

Got the kit in from MAC. It looks great. Dry fit was excellent. I ordered a spare nose cone so I can modify it for HEDD. It will be experimental but what scratch build isn't?

I originally planned on a split fin design because I like the look. However, that would make the rear fins potentially a bit weaker since they would be smaller and more prone to breaking, especially on certification. So instead I combined the split fins for a split-like look but more structure to hopefully take a beating a bit better. Still looks cool and maybe it'll whistle too.

So far, I've epoxied the forward two centering rings to the MMT, epoxied that into the bottom of the rocket, epoxied the fins internally, epoxied in the rear stepped centering ring and used JB Weld to epoxy the retainer. The fins are currently taped up and awaiting external epoxy filets.

I designed and 3D printed some conformal rail guides that double as 1/4" launch lugs as well. Gives me good flexibility on launch pads so I don't have to build a launch rail at my local site. Those will go on after the fin filets.

I picked up a 29mm Aerotech Hobbyline RMS. I've got some G76 reloads to maiden the rocket on. This reload has a pretty strong initial kick in the order of 125-150N for the first 0.25 seconds or so. This gets me a nice 30mph+ off-rail velocity even when using a 4ft launch rod. Sims to about 1000 feet give or take. Should make for a nice maiden and I can use the case in some smaller mid-power rockets too. Got a great deal on sale at wildman.

Lastly, I began (and actually finished already) construction of a 46" six-gore elliptical parachute. Used my wife various sewing machines and a serger to assemble it. Lines are 325lb paracord. Going to use my quadcopter and a 1lb dumbbell to do some drop tests this afternoon. I'll drop it with a JLCR as well to test inflation/deployment at higher speed as well. 46" is kind of big for the rocket as-is but once I build the dual-deploy configuration, I need the extra chute area. Should be about 16-17 fps at max weight and probably closer to 12 at light weight. Planning to use a JLCR for high-power flights so it doesn't drift 20 miles.
 

Attachments

  • IMG_1579.JPEG
    IMG_1579.JPEG
    151.6 KB · Views: 27
  • IMG_1577.JPEG
    IMG_1577.JPEG
    97.8 KB · Views: 28
  • IMG_1594.JPEG
    IMG_1594.JPEG
    129.9 KB · Views: 25
  • IMG_1588.JPEG
    IMG_1588.JPEG
    164.1 KB · Views: 23

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
5,246
Reaction score
4,503
Th are a nice chute. I have a 30” one in the same colors. They stand out nicely against the sky and ground so the rocket is easy to spot.
 

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
Chute test went well! My quadcopter was screaming to try and lift the extra 1lb weight and the chute. I dropped it from 200 feet with immediate deployment then from 400 feet with 200 feet JLCR deployment to test some higher speed shock (it was being dragged down with a 1lb weight). It worked and looked great! I did crash my quadcopter in the process, haha, but a few new props and it'll be fine.

External fillets are complete. I taped up the rocket with some wide tape, only took a few minutes actually. Then I mixed some BSI 30 minute epoxy and used a couple old children's Tylenol syringes to apply it in a thick bead. It oozed and spread out perfectly with basically no work from me. I just wiped up the excess that spilled onto the tape and right before it set, I removed the tape. Worked great!
 

Attachments

  • IMG_1612.JPEG
    IMG_1612.JPEG
    181.5 KB · Views: 18
  • IMG_1623.PNG
    IMG_1623.PNG
    300.3 KB · Views: 27
  • IMG_1632.JPEG
    IMG_1632.JPEG
    98.9 KB · Views: 25

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
Got a lot of work done. Rocket is pretty much finished. Got the rail guides glued on. Then I had some time to kill so I painted the beast. Turned out pretty well! I'm actually going to repaint one of the nosecones in bronze though for the single-deploy config. The dual-deploy config has a modified nosecone that I'm still working on installing a bulkhead with a T-nut for an eyebolt into the front of. Also finished the AVBay which was pretty easy to do.
 

Attachments

  • IMG_1661.JPEG
    IMG_1661.JPEG
    170.7 KB · Views: 28
  • IMG_1685.JPEG
    IMG_1685.JPEG
    178.7 KB · Views: 33
  • IMG_1692.JPEG
    IMG_1692.JPEG
    75.4 KB · Views: 32
  • IMG_1693.JPEG
    IMG_1693.JPEG
    60.9 KB · Views: 29

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
Nice looking rocket... you certainly moved faster than I did with my 3" build. :)

Thanks! Yeah I spent a couple hours a day moving it along. I got the G76 assembled the other day so I'm hoping to put the rocket up on that maybe tomorrow or the next day. If that goes well, I might be able to certify with it this Sunday in single deploy config.

McMaster delivered my 2-56 tap today so I got the shear pin holes drilled and tapped. I went with 1 on the bottom and 2 on the top. We'll see how that goes since I've never done this before. If I get early main deployments then I'll add a 3rd pin.

I was able to install the bulkhead and eyebolt into the nose cone. I should have taken more pictures for a build log but I've just been knocking out steps. I 3D printed a rather beefy bulkhead that had a bunch of extra texturing on one side of it to help glue adhesion. I scored the deep inside of the nose cone with 80 grit sandpaper. I put a 1/4-20 T-nut on the back of the bulkhead and used my soldering iron to heat it up and press it deep into the plastic bulkhead. Then I mixed some original gorilla glue with a little bit of vinegar and baking soda to help it get water and cure better and applied that to the top side of the bulkhead that would be hidden inside the nose cone. On the exterior ring of the bulkhead I used JBWeld Plastic Bond. My thought was the polyurethane gorilla glue would grab the top of the bulkhead and hold it from there and the JBWeld would bond with the sides. And the excess gorilla glue would expand into the top part of the nosecone cavity for extra grab. Looks like it's in there pretty solid. If it doesn't hold, I have some backup plans including the dowel method. Problem is, I won't know if it is strong enough until I launch it a few times, or maybe with the BP ground tests.

I also stripped and repainted the other nosecone. The paint wasn't really on that well anyway because I didn't use plastic primer. But I think the copper nosecone looks pretty sweet.
 

Attachments

  • IMG_1702.JPEG
    IMG_1702.JPEG
    71.2 KB · Views: 15

Saint_Tiki

Well-Known Member
Joined
Oct 6, 2020
Messages
58
Reaction score
55
It flies!

Perfect flight, landed 50 feet from the pad. I had no idea APCP motors would be that loud. ChuteRelease worked perfectly and it came down very gently under my huge custom chute. It did descend rather rapidly while the separated but before ChuteRelease opened so I went ahead and made a small drogue that I would need for the dual-deploy option anyway. Will test that out this week.

Very happy with the rocket! Will hopefully get to fly it on HP and certify this weekend or next.

 

Attachments

  • IMG_1703.JPEG
    IMG_1703.JPEG
    204.8 KB · Views: 12
  • IMG_1709.JPEG
    IMG_1709.JPEG
    53.3 KB · Views: 10

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
5,246
Reaction score
4,503
It flies!

Perfect flight, landed 50 feet from the pad. I had no idea APCP motors would be that loud. ChuteRelease worked perfectly and it came down very gently under my huge custom chute. It did descend rather rapidly while the separated but before ChuteRelease opened so I went ahead and made a small drogue that I would need for the dual-deploy option anyway. Will test that out this week.

Very happy with the rocket! Will hopefully get to fly it on HP and certify this weekend or next.



Yay! If you think general APCP motors are loud, wait until you hear a sparky. They roar...
 
Top