SpiderMax Scratch Build

[frogglicker]

Last week, I finished my scratch 3-inch Goblin, The Great Hobgoblin. I haven't been able to fly it yet and I am planning to Level 1 next Sunday with it. The weather hasn't been great and I didn't get a chance to get out to Harsel, Colorado. I had thoughts of heading down to Alamosa, Co. for the NAR NSL but family and time just won't allow for it. I sat and dreamed of the coolness of my first scratch HPR lifting off and soaring. Then the panic sets in, sleep was lost, and dreaming turned to designing (plotting).

I've built a lot of LPR scratch rockets. The first versions usually have a thing that I missed, but it's never been catastrophic. When you strap an "H" or "I" in the beastie, the game changes. I should have just sent that damn thing naked when I had the chance, but my brain just won't let it go and a naked rocket is, for me, unfinished. I have reprinted the nose cone because it doesn't sit right, and picked at it for a week. Now, I decided to just leave it alone.

While showing the pictures of the Hobgoblin to my team at work, a colleague of mine mentioned that the Hobgoblin has to have SpiderMan to keep him in check. That got me thinking... I could build a rocket to chase down the Hobgoblin, so... why not? No one was around to say no and my next project was born. First, my inspiration was spurred by this comic cover:



Next, I fired up TinkerCAD and started extruding some SVG files and turned them into STLs, trying to get a sense of what I wanted for a concept. While this is still in flux, these are some of the designs I worked up:



I took to open rocket and started designing. I have this special affinity for the Goblin/Red Max design, so I came up with a Red Max variation, but just a little longer. I may shorten it back to scale but it will be based on a 3-inch airframe.



My Hobgoblin has a 38mm MMT and I did that because I wanted to have a rocket that would boogie if I ever got to one of the bigger sites near me. I love my BRM and fly it every time I go to Ft Lupton, CO. for the C.R.A.S.H. Launches. I want to be able to do this with this rocket too, so I settled on 29mm. I can still squeeze a small "H" into it for the CRASH launches (125g propellant cap) but I can get bigger motors in it if I go elsewhere. I think the 29mm is a good size for this rocket.

When Estes had their 65th-anniversary sale, I picked up 2 BRM kits for $22/ea. The original plan was to use one for SpiderMax and supervise my son while he built a Star Wars-themed BRM. Then my wife asked, "Where's mine?" I thought she was being funny. I stood there looking at her and then realized, she was serious. I said, "Yours is over there in the box, waiting for you." She smiled and walked away. I got to live.

That's when I decided I'd scratch-build this one, like the Hobgoblin. I didn't document that build b/c I was rushing to get it done before the next launch (which didn't happen). The process will be nearly identical since the Hobgoblin is nearly the same with the exception of the MMT and the fin can.

I started out designing the fins. I purchased two, Vander-Burn BRM upgrade kits from labrocketry.com. I took the fin and pulled some dimensions. I found that building fins in TinkerCAD (at least for me) is an un-fun experience. I know there is a technique for doing it but I haven't found it yet. I started using OnShape online CAD and I love it. It's a big-boy CAD program, and it unlocked designs that I really struggled with in TinkerCAD. I still use tinkerCAD but OnShape is my Awesome New Tool of the Week!



When finished, I had a couple of minor issues but building the airfoil profile into the fin at design was a game changer. The fin's test print turned out really good:



The plywood fin is held behind the printed fin in the 2nd shot. I make a few mods to it since this picture but I like the shape, especially the airfoil. Unfortunately, the airfoils prevent decent placement on the print bed without supports being everywhere, I had to print the fin upright. I have concerns about the print lines not running the length of the fin, so I will laminate these with epoxy and pray that they don't snap. I'm probably not going to send this on anything larger than an "H" and probably mostly "F"s and "G"s. The only dimension that is different from the Vanderburn fin is this one is 6.35mm versus 3.125 (1/4-in vs 1/8-in) in thickness. I am preparing to print three of these on PLA Plus with 50% infill using 3D Honeycomb fill pattern at 0.08 resolution.

I then took to designing the centering rings. Taking from the same upgrade kit, I designed three centering rings: Forward with both a slot for the shock cord (3mm x 15mm) and a hole for an eyehook (6mm), the mid-centering ring, and the aft ring:

These are currently printing at 5mm thick with 100% infill. Finally, I have pulled the motor retainer from the Hobgoblin and scaled it down from 38mm to 29mm which is 76.32% scale (according to my rusty, trusting scale tool:


This will also be printed in PLA Plus at 100% Infill and 3D Honeycomb.

This is still in the concept phase and I have not committed to any element that I can't back away from yet, so I might change my mind on the MMT size. I have also been thinking about a top "BRM"-style wrap but with Spiderman's mask instead of the skull and crossbones. I am probably going to check in with Mark at StickerShock to see what ideas he has and get him to make this one-off design. I will post updates here as I make my way through the build.

I welcome your input, your critiques, and your cheers and jeers. I just love building these things from concept to cured paint and I can't wait to see this clean the Hobgoblin's clock!

 

[frogglicker]

Yesterday, I tweaked the fin for better fitment with the mid-centering ring and printed the 29mm motor retainer. This is not my design. I got it from wardy89 on Thingiverse



I'm also designing a 3-inch AV bay. This might not get used in SpiderMax, but it's something I've been working on for a while. Started it in TinkerCAD a while back and it is a redesign based on one by LadyKatherinePyro on Thingaverse. I Might try to move it to OnShape to keep that learning train a`rolling.



Finally, I was able to get the nose cone with AV bay filled and sanded. All that's left is a couple of coats of glossy black paint. The 3/8-inch eyebolt is only temporary. I have to pick up a 1/4-inch eyebolt while I'm getting more glossy black paint. In the picture are the Eggtimer Quantum and 2S 300 mAh battery.

The nose cone is not my design. I got it from Arogen67 on Printables and used the BRM, then scaled it up just a bit for a better fit on the shoulder.



Today, I will be working on the centering rings and a hamburger at the family picnic.

Happy Memorial Day. Thank you to all who served and please remember those who can't be with us today.

 

[cwbullet]

Nice design. I really like how you did the cone.

 

[Hobie1dog]

great work

 

[frogglicker]

Today, I set out to get the SpiderMax fins completed and the body tube slotted. Check!

While I was poking around on printables.com, I found a MMT for a BT-80 in a 29mm configuration. I took that and started playing around with it. The idea is to put a 29mm MMT inside as a liner and attach my own motor retainer. I am currently printing a test to check clearances. I will add the motor retainer to the sleeve once it's printed.

Last week, I created a fin slotting jig. I printed that out and got to work. Turns out, I printed the wrong one because I was working on a 6.3mm version and a 4.7mm version. I printed the 6.3mm fins but the 4.7mm fin slotting guide. Not a big deal. I just took a little off each side of each slot to keep it symmetrical/on-axis. I made two nose cones for the Hobgoblin build b/c the first one was just a bit too small. That's the nose cone that is pictured, here.



I made a little 13mm Goblin for display. the Hobgoblin is the same size as SpiderMax, so the little one is really, really tiny!

I'll post up some more pix of the motor mount when it's off the printer, but here's a sneak peek:

 

[frogglicker]

I just got the test print off the printer and wowzers, I'm excited! Taking the MMT from printables.com and importing it into tinkercad then opening up the tube for a 29mm mmt, adding the middle centering ring, then aligning the fins and making them holes (negative space), got me the design in the post above. I printed it to just above the mid-centering ring and did a test fit. It's a tad bit loose in the BT but not overly so. I made it maybe 1mm smaller than it should be. Too tight sucks b/c PLA+ is really hard to sand. If it was anymore, then I would go back and close it up a bit (still might).

With the body tube, I slid in the MMT, aligned the mid-CR and put the first fin in. It locked right into place perfectly. No gap on the outside, flush with the MMT opening on the inside. The next two fins were the same. I took a piece of 29mm MMT and slid it into the opening and it has a nice fit. Not too loose, just right. The fins locked into place and barely wiggled. This is totally going to work.

However, there is the matter of motor retention. The model for the MMT came with a retainer that screws in over the back plate. I would need inserts, heated and pressed in. Not a big deal but the original plan was to use an AeroPak-like screw retainer. I could extend the 29mm tube out just enough to capture the rings but there's maybe a 1/4-inch from the back CR to the lip of the body tube. I guess I will see how the AeroPak looks tomorrow. I will probably go looking for 5mm inserts and hex screws in case I like that better. The AeroPak would be faster and easier to get the motor secured but something calls to me to investigate this alternative method. We'll see in a couple of days which way I go. In the meantime, here are some pics of the MMT with the fins locked in:

 

[frogglicker]

The past week I have had to pick my battles. I lost one of my rockets to a rocket-eating tree and I have been hammered at work. Yesterday, however, I was able to make some progress.

(I thought I had a picture of this, but I do not)
I started off by threading the shock cord through the forward CR hole I created for 1/4 inch tubular nylon. I tied a half hitch in the end and covered it with epoxy. Earlier in the week, I cut slits to allow me to insert the fin/motor assembly. I also cut the tube above the fin assembly to make access easier to the forward CR (and give the option of dual deployment down the road -- more on that later). I dry-fitted the assembly and it seemed to fit well. Some small gaps between the CRs and the body tube but nothing concerning. I knew it was loose and would have to adapt to this. I struggled to get the assembly back out but was successful without damaging anything.

I put a coat of epoxy on the forward/mid CR areas within the body tube and then put it back in. For the most part, the assembly seated nicely, but there is an odd deformation on the aft end of the tube. I tried to figure it out but the epoxy kicked before I could sort it out. It's not bad, just cosmetic.




Once the epoxy finished kicking, I mixed up another batch of rocket sauce and added fumed silica to thicken it up. BTW, this stuff really works but it is very light and will go everywhere. When using it, lock your doors, turn off the fans, wear a mask, and get it into the epoxy ASAP. The consistency I was going for was something like peanut butter. It was no longer self-leveling and it filled the gaps very nicely. I have a very good bond with the BT. Once cured, I flipped the fin can over and repeated the aft CR. This one didn't as well. The epoxy wasn't thick enough and ran into the threads of the retainer, and dripped down the gap. It wasn't a lot so, I was able to control it. I came back with another batch and fixed it up but I had some unevenness on the CR. Again, cosmetic, and with the epoxy fully cures I can level it with everybody's favorite pastime... sanding.

Next, I taped off the fins and started doing the fillet. Again, I thickened up the epoxy with the silica. Between silica and taking my time, this went much better. Made a bit of a mess, but excess just went on the tape and came off with the peal. One thing I see is that my epoxy is a bit rubbery after it kicks. I wanted to get the tape off before it really cures but I think I waited too long. I'm going to test tape peals at different times starting with 2mins before it kicks and move down every 30 seconds, so I have a better idea of when I can pull and not get a rubbery edge.





Finally, I took the tube that I cut off and measured out the coupler to half the length, and glued it in place. Once the epoxy on everything tightened up. I put the payload tube with the coupler into the fin can, marked three spots, right above the fins, and drilled a 1/8-inch hole for each. I pulled out the payload tube and sanded down the holes - inside and out - on both tubes, applied thin CA to each, then sanded again, making sure the hole diameter didn't change. I lined it all up and it worked like a charm. I have the rivets but won't put them in until right before painting.



At this point, I will start sanding the tube, fill the wraps, voids, etc. with glazing putty and sand some more... I might get to put primer on it today. I will take more pics as I move through the process. Here are some glamor shots.

 

[frogglicker]

Nose cone testing (during my maiden and then again during my L1 cert... ACK!) proved that the print, as originally designed, isn't robust enough. It snapped at the threads between the shoulder and lower half during the maiden flight. During the 1st L1 attempt, it broke between the upper and lower half.

The meat behind the threads in these areas was maybe 1.5mm thick, and looking at it now, it's ridiculous. I just didn't see it when assembling it. I have added a full centimeter of meat behind the threads now, and plan to slather epoxy (ummmm... epoxy) all over the upper threaded section and on the threads once it's assembled. I love that I have a ready-made, AV-ready nose cone on demand, but if it keeps failing, I may have to either thicken the shell or abandon the print. Frogglickers never quit, so I'll probably add a couple more parameters to it. I am about to start a 10hr print of the middle section so I guess we'll see how it goes.

Now that the L1 is behind me, the pressure is off a little, but I still want a durable nose cone that won't dump my electronics all over Northern Colorado.

The picture below shows the modified lower and shoulder sections on the left in white and the original sections on the right in grey.

 

[frogglicker]

I am almost finished with Spidermax. Yesterday I began with securing the camera mount to the body tube. This is a self-designed camera shroud for the runcam2 4k (see file below). After that, I began separating and deploying the decals. I received a Cricut Maker 3 for Father's Day and it is an awesome addition to my collection of machinery. I also ordered a 30-inch LOC parachute and two 'H' motors. This I have one week before the next CRASH launch and I still have a few things left:

• Vent the body tube
• Mount the rail buttons
• Finish printing the nose cone (it has an AV bay in it. I have a stock BRM cone already painted)
• Epoxy laminate the inside of the NC
• Paint the NC
• Mount the avionics into the rocket
• Clear-coat the entire airframe and the spare nose cone

If I am unable to get the printed nosecone printed in time, I still have the one I have already painted. I really would like to test out the modifications that I did to the printed NC and get the electronics out of the BT. The top of the nose cone is finishing printing now and I should be able to get the NC sanded, primed, and maybe a coat on this weekend. I will put a second coat on as soon as the 1st is cured. Once all that is done, I will clear-coat the entire airframe and spare the nose cone. I should be getting the chute and the motors before the launch.

I just weighed the rocket and it comes in at 1.8 lbs.

 

[frogglicker]

Yesterday, I had an unexpected discovery. While finalizing the simulation of the rocket, it seems that I picked up a lot more weight than I had previously calculated. I am not sure what happened but I screwed up and now this is one, fat, flying arachnid. In the sim, it's almost 16oz heavier, in the tail. I would have to add 300g of nose weight to get it stable. ACK! I did a couple of different mod sims and it appears that if I extend the BT by 6", I only need 30g of weight. I have ordered two motors for the launch next Saturday -- an H210R and an H250G, and they will arrive tomorrow. This will give me enough time to get everything balanced correctly, though it looks a little "off."

I cut a 6" piece of a 3"-tube and glued a coupler to it. I have also finished printing the reinforced nose cone and have primed, sanded, filled, and sanded. Still need to prime it again, sand again, then get the color coat on it. The extension has also been primed and ready for color. I am not going to permanently affix the extension but will attach it with plastic rivets. The fin can is detachable as well and I may redesign the fin can since it's basically a boat anchor.

I also have additional decals for the new nose cone and I can cut more as needed while I progress. I still think the rocket is viable but I want it to have some flexibility since I generally fly at a smaller field.

The good news here is that I have a path to flight. Also, I was experimenting with AV bays in the tube for my BRM and have some bulkheads that, with some minor modifications, should work with this design. This will give me a great platform for perfecting dual deployment with an airframe that is flexible and can run as high as an I205W for launches at Tripoli Colorado or North Colorado Rocketry launches.

 

[frogglicker]

Well, it looks funky but it's better as far as the sim goes... I added the 6-in "payload section and now the stability is just at 1.25 cal vs 0.25 cal. I got my rough measurements with a spent DMS motor and no chute. I will drill the rivets, and vents, put the rail buttons on, get the chute installed, and then tomorrow night, I will build the motor and get it installed. The only thing left is to finish the paint on the nose cone and then add any weight to get it in the 1.2-1.6 cal range. I wish it had turned out looking better but rockets happen. I'd rather have a goofy-looking rocket go straight than a cool-looking rocket that sky writes all over Ft. Lupton, Colorado. Maybe I'll put another big spider or Web in that vacuum of space. I can definitely fix this with the following:.

• Cut new decals
• Cut and paint new tube between fin can and payload section
• Print new camera shroud

It would probably take about a week to get it reworked. I will unveil the Extended SpiderMax at my next Hartsel launch on the I200 next month (maybe). We'll see how it goes with the Ft. Lupton Launch Trials.

 

[BABAR]

Miss Muffet is in BIG trouble!

 

[frogglicker]

Here is the video of the maiden launch of SpiderMax and the C.R.A.S.H. launch on 7/15/2023.



Most times, my maiden launches do not go so well. I can only remember 3 out of ~12 rockets that were issue free on their maiden. I'm starting to get a better collection of data on what works/doesn't work for maiden flights. This one has solidly clobbered all the other maiden attempts.

 

[BABAR]

Congrats on a great rocket, flight, and video!

especially impressed with fin shaping and placement. practically No roll on ascent.

 

[frogglicker]

SpiderMax has had an active summer. I have launched it three more times since the YouTube post above (two were documented, one I'm still working on).

• July 23rd, 2023 - Launched on an H250G - Apogee was 2,143 ft. I didn't seat the onboard camera (design updated since) and it plopped down on the rocks. I did get a shot of the rocket as the camera was tumbling (see below). Also, I feel like an idiot b/c I didn't truly understand screw-on retainers. The cap that I designed and used was simply too tall and there was a gap between the interior lip and thrust ring on the motor case. The nozzle was also recessed a bit. In addition, I designed the opening on the cap to be just wide enough to prevent the case from slipping out. The problem was that will all these failings, I didn't account for the nozzle melting my cap interior opening, thus leaving a gap for the motor case to get violently pooped out the back. I have also since discovered that for wide openings on caps, you should have a ring sandwiching the motor between the MMT and the cap. Had I known this, I might still have my motor case. It is now just more space junk in a bison field in the mountains of Colorado. I do not yet have this video but I am at present, editing it.
  
  
• August 6th, 2023 - Launched on a G74 - Apogee was... well, not impressive. What WAS impressive was that I retrieved the rocket more or less in one piece. For SpiderMax, since the fin can is a decent amount of PLA+, it's really tail-heavy. My previous launches were conducted with a 3D nose cone that I have specifically modified for HPR flight. On this day, I was rushed to get everything and everyone in the car and grabbed my glamor nose cone. The paint on it is much better and looks great in pictures. Not so great with launches. I failed to check my CG before flight, which I really should have since I was flying a much smaller motor. Anyway, the video tells the tale: SpiderMax Rocket - You're Doing It Wrong
  
  
• August 19th, 2023 - Launched on a H220 - Apogee was not recorded but I would guess it was in the neighborhood of 1,800ft. This was the SpiderMax redemption flight. Being apprehensive about the previous two launches, I scrutinized the rocket from tip to tail and made sure everything was solid. The launch on the Blue Thunder motor looked amazing, the deployment with the JollyLogic Chute release was perfect, and recovery was uneventful. I have a video of that flight here: SpiderMax Redemption Launch. Unfortunately, one of the fins was broken on the trip back. I suspect that it was cracked during the skywriting session on 8/6. It has a metric tonne of epoxy holding it to the MMT, so graphing a new one will not be doable. I think I will attempt to reattach the fin, and then jump into learning fiberglassing.

All in all, this is one of my favorite rockets. The design isn't anything new and it's not a complex build for anyone who's scratch-built rockets before. For me, this rocket represents my passing through the threshold of cut-and-paste kit building into a much wider, more challenging world. The stakes are much higher with scratch-built HPRs because you're always pushing the limits. I have learned some easy lessons and some that were hard. Cutting the body tube of your triumphant sub-space vehicle to repair it because you were stupid is humbling. It's right there that we learn something about ourselves. Some quit. Some give up and go back to kits. Others will embrace the challenge and accept that rocketry is the essence of pressing on in the face of failure. For me, the challenge of building a one-of-a-kind rocket from scratch that kisses the sky and hearing the roar of the motor as it leaves the pad is all I need. Here are some pictures of SpiderMax's Journey (not shown above). Thank you for reading.

Btw, I post all of my rocket launches on YouTube, the Good, the Bad, and a couple that are really Ugly. Please check it out if you have a moment:

https://www.youtube.com/@FrogglickerSpace




Concept Drawing


MMT Hot of the Printer


Dry Ftting the MMT and Fins in the Body Tube


Fincan Assembled and Waiting for Fillets


The Wait is over - Fillets!


SpiderMax with the BRM, Maximus Periculum


SpiderMax: Ready for Action!


SpiderMax's Maiden Flight


SpiderMax's Second Flight


SpiderMax's Third Flight


SpiderMax's Forth Flight

 

[BABAR]

Thanks for sharing the good and the less than nominal.

Helps us all to learn.

That’s a really pretty rocket and (when. Properly prepped) a really nice flier.

Good vids, too.

 

[Hobie1dog]

Yesterday, I tweaked the fin for better fitment with the mid-centering ring and printed the 29mm motor retainer. This is not my design. I got it from wardy89 on Thingiverse

View attachment 583260

I'm also designing a 3-inch AV bay. This might not get used in SpiderMax, but it's something I've been working on for a while. Started it in TinkerCAD a while back and it is a redesign based on one by LadyKatherinePyro on Thingaverse. I Might try to move it to OnShape to keep that learning train a`rolling.

View attachment 583261

Finally, I was able to get the nose cone with AV bay filled and sanded. All that's left is a couple of coats of glossy black paint. The 3/8-inch eyebolt is only temporary. I have to pick up a 1/4-inch eyebolt while I'm getting more glossy black paint. In the picture are the Eggtimer Quantum and 2S 300 mAh battery.

The nose cone is not my design. I got it from Arogen67 on Printables and used the BRM, then scaled it up just a bit for a better fit on the shoulder.

View attachment 583263

impressive 3D printing, I'm highly envious.