Bolt from the Blue, a Blue Tube, Tube Fin Level 2 certification rocket

[Neutronium95]

After my previous project started suffering from a bad case of scope creep, I decided to look through the parts bin to see what I could rustle up for a level 2 build. This will technically be the third iteration of this rocket. The original was a mid power kit from Discount Rocketry that I got to write the instructions for, in exchange for a free kit. I crashed that one at LDRS, but I saved the nosecone. When a sandstorm blew in, I bought a length of 3" Blue Tube, and rebuilt it with a 54mm motor mount. I had several good flights with I140 motors. Unfortunately, it turns out that a rocket thrown together with 30 minute epoxy in the field tends to not be that well built, and I didn't really trust it on a bigger motor.

I've also learned from some of my previous threads, and I've actually waited until I started construction to post this. All told about half of the parts are recycled from other rockets, and I had most of the rest in stock, so I only had to order a few miscellaneous items. The original donated it's nosecone, centering rings, and it's body tube got cut up into the new tube fins. The slimline retainer is also the only remaining part of my ill fated L1 rocket.

Construction started with the slightly tedious process of cutting up the old airframe into 3 inch long sections for the tube fins. I had to use a hacksaw and a slightly janky jig to cut the tubes, and they needed a lot of love from the sander to make them look pretty. I also sanded down a 29mm-75mm centering ring to seat on the inner shoulder of the nosecone. This will provide a place to put a tracker, as well as provide a more secure shock cord mount than what was in there previously. The final bits of prep work involved cleaning out the old JB weld from the motor retainer, as well as removing all of the old epoxy from the reused centering rings.





Today I started gluing things together, starting with the avionics bay. I am using the standard Blue Tube 3" av bay kit, and it went together easily. If the rocket were significantly heavier I would probably swap out the bent eyebolts for forged eyebolts. I still need to figure out exactly how I want to wire up my two Ravens, as this will be my first dual deploy rocket to leave my imagination. I also hacked one of the centering rings to pieces, to add some thickness to the centering rings around where the rail buttons will be screwed in.



Tomorrow, I'll glue together the motor mount and bond on the first three of the tube fins. I've been trying to come up with a way to get the best attached tube fins possible, and my plan is to bond on three tube fins equidistantly, and fillet them very well. The other three will get glued on normally, and then I will apply fillets between each of the fins.

Thanks for following along as I try to push my building skills in HPR after being away for a while. This build is going to have a lot of firsts for me, beyond the obvious motor size. I have the Openrocket file attached for critique. There are a few place holder items, and it isn't quite up to the latest design, but it should give a good idea of where I'm going. I will figure out the parachute selection when I'm closer to having a finished weight for the rocket. My current plan is to get in a few flights with H and I motors to figure out electronic dual deployment, before doing the cert flight. If everything goes well, I might put a few layers of carbon fiber on the inside of the fins, and try to get it through the sound barriers.

 

[roytyson]

3" Bluetube makes great tubefins, that fly great on J350's

 

[Neutronium95]

3" Bluetube makes great tubefins, that fly great on J350's

That looks really nice. What does it weigh?

I'm also trying to do better on painting and finishing than on my previous projects. The most that I would do would be a quick rattle can paint job with barely any finishing work.

 

[o1d_dude]

After my previous project started suffering from a bad case of scope creep, I decided to look through the parts bin to see what I could rustle up for a level 2 build. This will technically be the third iteration of this rocket. The original was a mid power kit from Discount Rocketry that I got to write the instructions for, in exchange for a free kit. I crashed that one at LDRS, but I saved the nosecone. When a sandstorm blew in, I bought a length of 3" Blue Tube, and rebuilt it with a 54mm motor mount. I had several good flights with I140 motors. Unfortunately, it turns out that a rocket thrown together with 30 minute epoxy in the field tends to not be that well built, and I didn't really trust it on a bigger motor.

I've also learned from some of my previous threads, and I've actually waited until I started construction to post this. All told about half of the parts are recycled from other rockets, and I had most of the rest in stock, so I only had to order a few miscellaneous items. The original donated it's nosecone, centering rings, and it's body tube got cut up into the new tube fins. The slimline retainer is also the only remaining part of my ill fated L1 rocket.

Construction started with the slightly tedious process of cutting up the old airframe into 3 inch long sections for the tube fins. I had to use a hacksaw and a slightly janky jig to cut the tubes, and they needed a lot of love from the sander to make them look pretty. I also sanded down a 29mm-75mm centering ring to seat on the inner shoulder of the nosecone. This will provide a place to put a tracker, as well as provide a more secure shock cord mount than what was in there previously. The final bits of prep work involved cleaning out the old JB weld from the motor retainer, as well as removing all of the old epoxy from the reused centering rings.

View attachment 412734
View attachment 412730
View attachment 412735

Today I started gluing things together, starting with the avionics bay. I am using the standard Blue Tube 3" av bay kit, and it went together easily. If the rocket were significantly heavier I would probably swap out the bent eyebolts for forged eyebolts. I still need to figure out exactly how I want to wire up my two Ravens, as this will be my first dual deploy rocket to leave my imagination. I also hacked one of the centering rings to pieces, to add some thickness to the centering rings around where the rail buttons will be screwed in.
View attachment 412731
View attachment 412732

Tomorrow, I'll glue together the motor mount and bond on the first three of the tube fins. I've been trying to come up with a way to get the best attached tube fins possible, and my plan is to bond on three tube fins equidistantly, and fillet them very well. The other three will get glued on normally, and then I will apply fillets between each of the fins.

Thanks for following along as I try to push my building skills in HPR after being away for a while. This build is going to have a lot of firsts for me, beyond the obvious motor size. I have the Openrocket file attached for critique. There are a few place holder items, and it isn't quite up to the latest design, but it should give a good idea of where I'm going. I will figure out the parachute selection when I'm closer to having a finished weight for the rocket. My current plan is to get in a few flights with H and I motors to figure out electronic dual deployment, before doing the cert flight. If everything goes well, I might put a few layers of carbon fiber on the inside of the fins, and try to get it through the sound barriers.

I suggest you search for message thread here on TRF for “Bluefin Tuba” by user name “iter”.

It was his L3 cert bird. Successful, too.

 

[Neutronium95]

I suggest you search for message thread here on TRF for “Bluefin Tuba” by user name “iter”.

It was his L3 cert bird. Successful, too.

Thank you. I had read the 38mm and 4" threads before, but I missed the 3" version. That really helps with some of my anxiety. I'll go with the regular tube fin bonding process then, instead of trying to get 3 fins bonded and filleted for extra strength.

Of course it also makes me want to leave the motor mount out...

I am really feeling tempted right now. I don't have any 75mm hardware. I can't really afford M motors on my budget. Then again you can always adapt down, but you can never adapt up.

 

[dhbarr]

j270w in 3in mailing tube, woodglue, lvl2. Watch the spirals on the fin edges, I'd use a brush to harden them if I was doing it again.

 

[Neutronium95]

After playing around with Openrocket a bit, I have decided to toss the motor mount in the trash. (Not really, it will make for a fine adapter.) This is going to require a few design modifications, namely:

• Move the fins up an inch from the base of the rocket to allow for easier motor and adapter retention with tape.
• Rethink the rail button mounting. I was originally going to screw into a centering ring, but that's not really an option on a minimum diameter bird.
• Acquire a fiberglass nosecone and set it up for HED if I ever want to use a longer 75mm case. I'm limited by the tube lengths that I already had.

I figure that there's a 50/50 chance that it will always fly with an adapter, but now that I know that it is possible to fly an M with my materials and techniques it seems foolish to close off future motor options.

 

[Bat-mite]

Looks great!

 

[BABAR]

That’s really Scyc!

 

[Neutronium95]

I have a quick question for before I start gluing things together. How sensitive is Rocketpoxy to minor changes from the specified ratio. My digital scale only goes down to grams, and I prefer to make more small batches than one big one.

 

[Rocketjunkie]

Rocketpoxy is 1:1 mix. +- 5% will be OK.

 

[Neutronium95]

Rocketpoxy is 1:1 mix. +- 5% will be OK.

That's what I figured. I went with a 20 gram batch, which was way more than I needed to glue everything that I could glue.

Before I got the rocketpoxy going, I glued the front centering ring and Kevlar y harness to the 54mm adapter.

After that I hit each of the tube fins, and the bottom end of the body tube with sandpaper. I'm not sure how much it will improve adhesion, but it can't really hurt.

Next up was cutting off some sections of coupler and body tube. A relatively long thrust ring will work well with the aluminum tape that I'm planning on using for retention.

Finally, it was time to start slinging epoxy around. I got two pairs of fins glued together, I don't have enough of the correct kind of clamps to do more than that at once. I also got the rear centering ring/coupler tube/thrust ring part of the adapter glued together. Finally, I glued in the nose cone centering ring and the middle centering ring for the adapter.


Later today, I'm going to glue the last two fins to the body tube, fillet the existing fin pairs, and do the final assembly of the 54mm adapter.

 

[Neutronium95]

I made some more progress in my second session today. First up was finishing up the motor mount adapter, complete with the reused Slimline from my Jr. L1 rocket. I can't believe that it's been 11 years since I built that hunk of junk. I'm also really liking the added versatility that the minimum diameter approach will allow for. It doesn't just open the door to an M someday, but it also allows for fun clusters like 7x24mm or 3x29mm motors. I was already planning on doing my SpEEEEar rebuild like this, so it was a pretty easy decision to make.

(This is just a dry fit, the retainer was thoroughly wrapped in masking tape when the epoxy came out)

Next up was gluing two of the tube fins on opposite sides of the body tube. I used one of the two tube assemblies from earlier in the day to help hold everything straight. I also prepped the tube pairs for filleting at this point.


This was actually my first time doing the "standard HPR filleting technique" before. I needed to clean up some excess epoxy from when I tried to build up the joint a bit during the initial assembly, but other than that the prep work went fine. I let the epoxy set up for about 20 minutes before starting the fillets. I was working in a pretty tight space, and didn't need that much epoxy to get a decent amount of contact on both sides. I probably used a bit too much, but a few passes with a dowel got them looking pretty. I did pull the tape off pretty early, I was worried about excess possibly dripping back onto the fillets.





All in all, everything is coming together quite nicely. I should be able to get all of the fins on tomorrow. The only thing that I'm not quite sure about is the final configuration of the nose cone. I have a 29mm centering ring in there right now, and the tracker that I'm considering should fit inside a 29mm coupler, but I'm not certain about how I want to retain everything in the tube that will get glued in there. I might also start laying out the avbay, but I'll probably wait until I actually get my hands on a battery.

 

[Maxter]

I have about 16 flights on mine. Everything from a G to a K. I try to fly it at every meet. l love it!

 

[Neutronium95]

I had a very productive day today. I got the pair of fins that are opposite each other filleted to the body tube, and also got the other bonded pairs glued to the body tube. Once it's cured, I'll only have to do four sets of fillets between fins, and the booster will be pretty much complete. The final bits of hardware for the rail buttons should arrive tomorrow. With the change to a minimum diameter rocket, I am going to have to change the mounting a bit, but I should be able to manage with the hardware I ordered.


I also got the 54mm adapter cleaned up a bit, and made sure that there were no stray blobs of glue that would interfere with the motor casing. I also put a third round of epoxy on the kevlar y harness, because I can't leave well enough alone, and kept peeling the tape off too early, leaving the top few inches looking much worse than the rest of the glue joint. A little bit of sanding will clean up any ridges left by the tape. I know that it doesn't matter, and it's kind of silly to worry about aesthetics on a motor adapter, but part of the reason behind building this rocket is to make something to be proud of. The previous version of this rocket had ugly glue joints all over the place.

I figured out how I'm going to retain the gps into the nose avionics bay, so I cut the tube for that, and glued on a kevlar y-harness. I'll have to file and dremel the centering ring in the nose to make that fit, but it should provide a secure mounting point for the recovery harness.


Finally, I decided to figure out some cluster options that the move to swappable motor mounts has opened up. I'm pretty sure that 7x24mm, 2x29mm, and 3x29mm are all quite possible. I'm not sure about how hard it will be to find centering rings for some of the options, so I'm learning Inkscape to get some rings laser cut. I might even wire up the 7x24mm to work with airstarts, although that would make composite motors mandatory, which would get expensive fast.

I'd also like to talk about the Rocketpoxy that I've been using pretty extensively throughout this project. This is the first "nice" epoxy that I've used, and I really like it once it's mixed, but dealing with the really thick resin and hardener has been a bit of a pain. I would really prefer something that I could pour or pump. I think that I might try out the Aeropoxy es6209 after my small kit of Rocketpoxy runs out.

 

[Neutronium95]

I got a bit more done yesterday. Another fin fillet down, 3 more to go. I'm not comfortable doing multiple fillets at once, so I've just been doing one whenever I mix up a batch of Rocketpoxy. I also got the 29mm tube mounted into the nosecone after I gave the centering ring a bit of love with the Dremel.


Finally I added the rail guides. I reused the hardware that I was planning on using to screw the rail buttons into a centering ring. I cut out a few pieces of half inch plywood, installed some threaded inserts, and then went to town on them with the sander to make them vaguely aerodynamic. A bit of sanding to make them conform to the curve of the body tube and they were ready. I had some issues with trying to hold them straight, and I ended up just eyeballing it, because everything else just seemed to make it worse. I'm not entirely satisfied with how they turned out, and I might cut them off and try again, or go to the Giant Leap conformal rail guides instead.


With the addition of the rail guides, the booster is almost entirely complete, except for a few small fillets, so I started weighing things. I think that I might be able to keep the simple park flyer configuration (just booster nose and 29mm motor mount) at around a kilo, and the full up dual deploy configuration should be well under 2 kilos. I really want to make a lighter avionics bay, as I feel like the current one is quite heavy.

With the exception of the rail guides, everything does seem to be coming together quite nicely. I'm a little bit nervous about the finishing and painting, as I was never that good at it. If anyone has links to guides to getting a good rattle can paintjob, I'd like it if you could throw them up here. Thanks.

 

[Neutronium95]

I made a little bit more progress today. Since I used one of my two 29-75mm centering rings, I needed to make another for the 29mm motor mount. Unfortunately, I didn't have any material that was appropriate. Half inch plywood would be extreme overkill, and while this isn't ring shouldn't be seeing big loads, I was wary of using some of my quarter inch balsa. In the end, I decided to throw a few layers of fiberglass onto the balsa for some peace of mind, and to use some very beefy fillets on the lower centering ring.

This was my first time working with fiberglass in about ten years, and I'm not really proud of any of the fiberglass work that I did as a teenager. I did manage to scrounge up some peel ply, but pretty much everything else was improvised. The fiberglass was stuff of unknown provenance that I found after about a decade of storage. I used a bit of alcohol to thin down some BSI 30 minute epoxy, and used a tile and a bucket of water to press the part.

Everything wetted out.



It was a bit of a pain to keep the fiberglass from moving around and distorting too much while I was getting it wetted out, but I was pleasantly surprised with how smoothly the operation went. My only concern is that the epoxy is taking a long time to cure, and I'm worried that I might have used a bit too much alcohol to thin it, I guess I'll know in the morning whether I totally screwed up. It's probably just taking longer due to the alcohol and the relatively chilly night air.

 

[Neutronium95]

The fiberglass ended up coming out fine. I think that the top layer had some spots that weren't quite fully wetted out, but other than that it looks good enough.

The sander and Dremel made light work of turning it into an actual centering ring. The center hole is a bit wonky, but it's enough to keep the motor mount tube straight, and the biggest gaps only needed a bit more sanding to fit the kevlar harness.

After that, I assembled the two main subassemblies of the 29mm motor mount adapter, and got fillet number 4 done. I did have some issues with the Rocketpoxy being a bit runnier than I had gotten used to, due to warmer weather. This evening, I did the final assembly of the adapter, and did fillet number five. Tomorrow I'm going to start work on the av bay.

 

[o1d_dude]

Why are you going with a 29mm motor mount for a level 2 rocket?

All of my tubers run 38mm at a minimum.

Did I miss something?

 

[Neutronium95]

Why are you going with a 29mm motor mount for a level 2 rocket?

All of my tubers run 38mm at a minimum.

Did I miss something?

It's a 29-75mm adapter. Without the av bay and upper parachute sections this should be light enough to fly on a G or a punchy F. The 54mm adapter that I made is kind of heavy, and an additional 29-54 adapter would just make it worse, so I made a dedicated 29mm adapter that would be significantly lighter. I have a few H reloads that I want to use to figure out dual deploy before I certify on a 3 grain 54mm motor. After I certify, I'll probably mess around with whatever clusters I can fit into it. If I can afford the reloads, I might throw in a few 75 mm motors someday.

I also edited my post to better reflect that it's an adapter. I've been thinking in terms of swappable motor mounts since I decided to go with the minimum diameter design.

 

[o1d_dude]

It's a 29-75mm adapter. Without the av bay and upper parachute sections this should be light enough to fly on a G or a punchy F. The 54mm adapter that I made is kind of heavy, and an additional 29-54 adapter would just make it worse, so I made a dedicated 29mm adapter that would be significantly lighter. I have a few H reloads that I want to use to figure out dual deploy before I certify on a 3 grain 54mm motor. After I certify, I'll probably mess around with whatever clusters I can fit into it. If I can afford the reloads, I might throw in a few 75 mm motors someday.

I also edited my post to better reflect that it's an adapter. I've been thinking in terms of swappable motor mounts since I decided to go with the minimum diameter design.

Got it.

Thx.

 

[Neutronium95]

I haven't made much progress in terms of gluing things together. I've been spending most of my time figuring out how to lay out the avionics bay so that everything fits nicely. In that vein, I would appreciate it if someone could give me the exact hole pattern on the Raven. I can't seem to find it in the instructions, and I would like something to check my measurements against. I also finished up the fillets, and made a mess of the 29mm motor mount trying to make the thrust ring look pretty.



I also got bit by the altitude bug again, and I'm thinking about doing a series of rockets to build up to my old 29mm two stage design. Part one of that plan is to build a two stage rocket, and what do you know, but I happen to have a bunch of 3" Loc tubing lying around with couplers glued in by some idiot. I also have a very stable 3" booster under construction that can fly on a wide variety of motors....

Today the only tangible progress that I made was drilling the vent holes for the avionics bay. I also recorded weight and CG information for all of the different configurations, so that I can get working on the sims. I've attached sim files for all three configurations that I'm planning on flying this in for now. They are 54mm dual deploy, 29mm dual deploy, and 29mm motor eject. Some of the internal structure is simplified, but the overall mass and CG are correct.

 

[Neutronium95]

With the rocket mostly built, this thread is probably going to go dormant for a while, until I decide on how to lay out the avbay sled. I'm planning on doing a few flights on G and baby H motors in a single deploy configuration without the avionics bay. I also have a few higher thrust H motors that I'm going to use to test out all of the dual deploy electronics, and then I'll probably do my certification flight on a Pro54 3G reload, although I'm not sure which one yet.

I'm also starting to design my next project, which will quite literally build upon this one:

My long term goal is to actually build that 29mm minimum diameter two stage rocket that you can find in my posts from about a decade ago. I figured that I should probably learn HPR staging with something a bit less extreme. I also have some LOC tubes that some idiot (past me) glued couplers into lying around, so I figured that I'd find a good use for one of them.

 

[Neutronium95]

I decided to use the base tubefin rocket as the first stage of my first high power two stage rocket. I'm going to have a more detailed post later, but have some pictures of the avionics bay in progress.

 

[Neutronium95]

I just got news that there will be a launch tomorrow. I've got a decent number of 29mm motors to burn. I want to take some more time to sort out the electronics, so I'm just going to fly it with the nosecone on top of the fin can. I also finally figured out a better name for this rocket. Since the short configuration is almost identical in size to it's predecessor, I'm naming it the Blue Twober.

The final weight for that configuration with 29mm motor mount, kevlar shock cord, 36" flat parachute, and nomex blanket came out at 1020g.

 

[PatD]

With the rocket mostly built, this thread is probably going to go dormant for a while, until I decide on how to lay out the avbay sled. I'm planning on doing a few flights on G and baby H motors in a single deploy configuration without the avionics bay. I also have a few higher thrust H motors that I'm going to use to test out all of the dual deploy electronics, and then I'll probably do my certification flight on a Pro54 3G reload, although I'm not sure which one yet.

I'm also starting to design my next project, which will quite literally build upon this one:
View attachment 413965
My long term goal is to actually build that 29mm minimum diameter two stage rocket that you can find in my posts from about a decade ago. I figured that I should probably learn HPR staging with something a bit less extreme. I also have some LOC tubes that some idiot (past me) glued couplers into lying around, so I figured that I'd find a good use for one of them.

Looking at the rendering, it appears that you have 5-6 inches of bt behind the sustainer nozzle. I'm probably looking at it wrong, but that would seem to invite aft bt flamage. Take that word however you like, but pronounce it with a french accent.

 

[Neutronium95]

Looking at the rendering, it appears that you have 5-6 inches of bt behind the sustainer nozzle. I'm probably looking at it wrong, but that would seem to invite aft bt flamage. Take that word however you like, but pronounce it with a french accent.

I'll post some pictures after I get the sustainer fin can glued together on Sunday. There is a coupler sticking about four inches out the back of the sustainer, and the motor mount sticks out about a half inch past the end of that. If you're worried about the sustainer motor roasting the booster, I'm planning on using a separation charge to kick the stages apart before lighting the sustainer.

 

[Neutronium95]

Just got back from the TRASD Holtville launch. I got two flights in with this in it's stubby configuration, with the 29mm motor mount. The first, on an H133 was about as good as could be expected with the wind we had. I did get a bit turned around and lost trying to find it after it landed though.


After having a long walk to recover it, I decided to reef the parachute a bit, to try to get it to come down a bit closer to the pad. The up part on the H159 was good, but the parachute fouled on the way down. Since I was fumbling around with my camera and glasses, I didn't get a good look at it, so I don't know if it just wouldn't inflate, or if it was tangled due to trying to pack it in windy conditions. Whatever the exact circumstance, the rocket had a hard landing and smashed one of the tube fins. Fortunately, I think that I have just enough 3" Blue Tube lying around to replace the broken fin.


I learned a few lessons from this launch, in no particular order they are

• Always use a tracker at Holtville. Despite being in the desert, the large bushes and rolling terrain make it very difficult to spot a rocket on the ground.
• Err on the side of a longer walk than a broken rocket when sizing parachutes. If I hadn't messed around with reefing the lines I could have gotten several more flights in.
• Blue Tube isn't quite as impact resistant as I had hoped. The tube fin snapped rather convincingly.

 

[Neutronium95]

I noticed some small stress marks and cracks in the adjacent fins to the one I replaced. I used my last piece of 3" Blue Tube replacing the broken fin, and I didn't feel like putting in the work to remove a mostly good fin. I decided to reinforce all of the fins with some unidirectional carbon fiber that I had in storage. I had some problems figuring out how to get it into the fins, but I eventually got one fin reinforced. I have it curing now, so I'll see what it looks like tomorrow.

 

[Neutronium95]

I've been making progress on the carbon fiber fin reinforcements. I got the carbon applied to the last two fins today, but I think that I'm going to need to put an additional layer of epoxy on, and then do a lot of sanding to get it all looking good.


I also got a parachute from BAMA recovery for this. It's a bit oversized for most configurations, but it should be fine for when I shove a 75mm motor in it. Incidentally, my club has some cases I might be able to borrow for my cert flight...

(It is really hard to get a good picture of a parachute inflated when you're running backwards with a phone in one hand.)