Another Level 3 Cert Rocket...

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slaak

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After mainly lurking on this forum for the past couple years, I decided its time for me to try and give back what I can and what I have learned by writing my very own build thread!

This rocket will be a scratch build 3” minimum diameter with a bunch of uniqueish parts. Over the past year I have become obsessed with machining so I bought a small milling machine over the winter and converted it to CNC and recently picked up a small manual lathe. With these tools I’m going to try and make some fancy looking and multi-purpose aluminum parts.

Here are some stats on my proposed rocket.

Body: 3” carbon tube.
Motor: 75mm AeroTech M650W (Longburner).
Nosecone: 5.5:1 Filament Wound fiberglass (Blue).
Fins: .070” 6061 Aluminum with .21” Al fillets X 4.
Bulkheads: 6061 Al made using CAD/CAM.
Max alt. ~33k ft.
Recovery : 4’ RocketMan main, tumble at Apogee.
Tracking: 100mW BeeLine GPS.
Flightcomp: 2x RRC3.

Most of the parts for this rocket are at some stage of completion, but it is still unassembled and many parts need some finishing work done to them.
I am a huge fan of pictures and not a fan of text so I will try to include as many pictures of my process as I can but will happily answer any questions.

Here goes some pictures!

SolidWorks render
full rocket render.jpg

The business Area. the front tube will house the rockets parachute and will act as a chute cannon, there will be and end plug which isnt shown that holds the apogee charges.
transparent render.jpg

Electronics Bay, AFT looking FWD.
ebay render aft.jpg

Aft Bulkhead ,AFT looking FWD. I went for an ISOgrid design style on this part to keep it light, The 3 outer holes will have 10-32 bolts going threw them to some Al posts that span the E-bay and the center theaded hole will hold the 3/8 bolt that screws into the motor closure.
AFT Bulkhead looking FWD.jpg

Aft Bulkhead, FWD looking AFT
AFT bulkhead looking AFT.jpg

FWD bulkhead. The two 3/8 holes which would make up the eyes of the smiley face will hold blackpowder to launch the rockets parachute and the tube going threw the mouth will be where the recovery cord is routed.
FWD bulkhead.jpg

E-bay sleds, AFT looking FWD
Esleds aft.jpg

Sleds on bulkhead, center bolt screws to motor closure and holds the whole rocket together!
Sleds looking Aft.jpg

Assembled Electronics bay
Assembled Ebay.jpg

Electronics bay asm, AFT looking FWD
Ebay asm looking fwd.jpg

More to come!
 

slaak

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Electronics Bay looking AFT
ebay asm looking aft.jpg

Fins. The fins still need a lot more work, the fin root will be sanded to match the curve of the airframe then sandblasted all over followed by Alumiprep 33, followed by Alodine 1201 application everywhere but the root, the root will be sandblasted again with course abrasive and bond prepped with boegel ac-130, and finally bonded to the airframe with henkel loctite hp120.
With the .5" bond width between the aluminum and carbon tube a tip to tip layup shouldnt be needed at the speeds im going. the test I did using this prep and bond method followed by putting the aluminum in a vise and hitting the airframe with a mallet only crumpled the airframe and eventually caused some internal delamination but the bond never failed.
fins.jpg

Fin fillet
fin rad.jpg

Fin side view
fin side.jpg

Charge connectors
charge connectors.jpg
 

dhbarr

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YES! Who are your L3 signer-offers ( the lucky dogs ).
 

blackjack2564

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REK

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Ugh why does my curiosity get the best of me. Cool bird and all and I love the design, but why go with aluminum fins is my curiosity?


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markkoelsch

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The av bay is very nice.

What do you mean by tumble recovery at apogee?

I would also ask why al for the fins? Not knocking it, but curious why that versus g10 or carbon fiber?
 

ksaves2

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The av bay is very nice.

What do you mean by tumble recovery at apogee?

I would also ask why al for the fins? Not knocking it, but curious why that versus g10 or carbon fiber?
Why? Because he can do it!:wink: Really nice if you ask me. If I had the skill set, I'd get the cert pulled off with the lightest "M" (meaning not so stupid powerful) that can get the job done. Then if the right venue is available, put the biggest (reliable) motor that can fit (certified or tested Research) and let 'er rip.
Al fins seem to handle flight stresses a bit better. You could argue overkill Mark but by gosh if Slaak can do it (college kid maybe?) why not.
Surprising no postings over time before. I'd question if the through wall charge contacts in the pictures above are insulated from the Al plate. Dead short
otherwise. Jim has some valid observations too I'd say. Kurt
 

slaak

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YES! Who are your L3 signer-offers ( the lucky dogs ).
That’s a good question. I have had the ideas for this rocket floating around in my head for a while now but only really committed to actually designing and building parts a couple weeks ago so I haven’t really talked to anyone about it. I wanted to at least get some proof of concept parts build and get a little polish on the design first.

Are you bonding the Al fins directly to a carbon airframe? Are you using some material to insulate?
Or are you putting a wrap of fiberglass around carbon where Al contacts....[possible electrolysis]

I was made aware of this by CTI.........when I did a similar project.
https://www.google.com/?gws_rd=ssl#q=Carbon+fiber+contact+with+aluminum+electrolysis
This is a really good question and thank you for it because I hadn’t really considered the electrolysis between the two materials. I wasn’t planning on any type of fiberglass overwrap. I’m going to coat the fin roots with some fancy Aluminum bond prep, Boegel AC-130. If you believe the pamphlets that come with it and this diagram from 3M I should be protected from corrosion( I think? Im not much of a corrosion guy). I also read see in this study that using a bond primer should increase my bond strength by a ton and using a primer would definitely protect from corrosion. https://www.dtic.mil/dtic/tr/fulltext/u2/a423563.pdf
Other than that I am a big fan of having a consistent bond width and know the epoxy I’m using like a 3-7 thou bond thickness so I was planning on making some glue shims to place between the fin root and carbon body tube so there shouldn’t be any contact between the two anyways.
Capture.PNG


The av bay is very nice.

What do you mean by tumble recovery at apogee?

I would also ask why al for the fins? Not knocking it, but curious why that versus g10 or carbon fiber?
I went with Aluminum for a couple reasons buy it really come down to because I think it’s cool and fun to work with and I hadn’t made any aluminum fins before. For more technical reasoning, I wanted to make this rocket high performance so to speak which to mean meant making it short with thin fins to minimize surface area and drag as a result. Carbon fiber has some pretty ridiculous strength-to-weight compared Al but for something like its bending stiffness at a given sheet thickness its improvement isn’t nearly as large (carbon fiber should still be lighter, stronger, and stiffer but it’s not a landslide). Anyways I figured either material would be strong enough as a fin and the overall strength of the fins would come down to the strength of the fillets and I figured that having a fin and fillet machined from a single billet of Aluminum would be stronger than a carbon fin with a glue fillet. On top of that I really hate/suck at making glue fillets and am never satisfied with how they turn out. I also thought that having a full half inch bond width between the body tube and aluminum fin root would make for a pretty solid fin.



I'd question if the through wall charge contacts in the pictures above are insulated from the Al plate. Dead short
otherwise.
The charge connectors shouldn’t short unless something goes pretty wrong in flight, I made the holes big enough so that the wire and shrink wrap fill fit through and flush with the connector bottom so no metal is exposed. I am planning on basically potting the connectors into that milled recess with epoxy, so they won’t wiggle and wear through the shrink wrap. It might be a good idea to coat the bottoms in plasti-dip or something though just to make sure there isn’t any contact.
 

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I understand for aesthetic reasons, but for technical reasons carbon fiber is the winner. I will note and defend that carbon has various fiber types that are stronger, the same goes for epoxy.

I'm subcribed, I like this rocket.

Tech tip: Use Mother's Aluminum & Mag polish. It will make it very reflective.


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blackjack2564

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Instead of glue shims, why not machine some "nub standoffs" in various locations on fin root to do same. You will have better control on your 3-7 thous... bond thickness and one less part to fiddle with.


Edit...don't know what I was thinking, you already have the fins...lol
 
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blackjack2564

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I did something similar to you....had AL fillets machined by Eric@ Baddazz for the airfoiled fins to slide/glue into.
Wanted all AL, but that would have been to costly.

I see exactly where you are going with this & concur, much better 1 piece.

Binford-Hendrickson 2013 N0001.jpg DSCN2210.jpg

DSCN2339.jpg attachment-4.jpg


attachment-3.jpg

Unfortunately the N-1000 Research motor catoed and went through the airframe around 200ft. ending my 50,000 ft attempt......i'll be back! LOL
 
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slaak

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I understand for aesthetic reasons, but for technical reasons carbon fiber is the winner. I will note and defend that carbon has various fiber types that are stronger, the same goes for epoxy.

I'm subcribed, I like this rocket.

Tech tip: Use Mother's Aluminum & Mag polish. It will make it very reflective.


Sent from my iPhone using Tapatalk

Higher grade carbon fiber and epoxies that are processed right are defiantly some amazing materials to work with, crazy strong. One day I’ll do a tip-to-tip layup with some fancy composite but I don’t really have the patients or skills to give them what they deserve. I'll look into the polish but I'm not sure if it will play well with the sealant I'm going to use. I have some Alumiprep 33(some kind fancy acid based cleaner used in AERO) in the mail that I was referred to to get some shine back after sanding/sandblasting but after that I'm going to coat the aluminum parts in Alodine 1201 and it really doesn't react well with a lot of cleaners.


Instead of glue shims, why not machine some "nub standoffs" in various locations on fin root to do same. You will have better control on your 3-7 thous... bond thickness and one less part to fiddle with.


Edit...don't know what I was thinking, you already have the fins...lol
I might try and machine some metal nubs on the a test fin that I have to see how it works. I was going to make them out a glue because that’s what I’d seen in industry (pretty limited exposure though) to hold a bond gap. I don’t actually know why they make them from glue, I think it might be so that you don’t have to worry about any chemical interaction between the glue and shim or metal and shim, not sure thought. I should be able to control the thickness pretty accurately(or good enough to make me happy), to make them I was planning to put some Teflon tape on a milled flat piece of aluminum then just smooth on some glue and mill it to a final thickness after it hardened then try to get it off the Teflon tape and x-acto it into little 1/8” or ¼” squares/strips. Not sure if I’ll be able to get it off the tape or if the epoxy will machine when it’s that thin.


I did something similar to you....had AL fillets machined by Eric@ Baddazz for the airfoiled fins to slide/glue into.
Wanted all AL, but that would have been to costly.

I see exactly where you are going with this & concur, much better 1 piece.

View attachment 322898 View attachment 322899

View attachment 322900 View attachment 322901


View attachment 322902

Unfortunately the N-1000 Research motor catoed and went through the airframe around 200ft. ending my 50,000 ft attempt......i'll be back! LOL
That rocket looks sweet! Sorry to hear about that cato  I mocked up a design that was very similar to that before I decided to go with one piece. I wasn’t able to come up with something that I felt was so profile enough, but yours looks pretty dang sleek and not all that bulky. I know what you mean about one piece fins being costly, there was probably 5-7 hours machine time per fin the way I did it, if I had a more rigid machine I could cut that in half or less but it’s still a lot of different setups. if I wasn’t doing it myself id of gone with a more traditional fin due to cost. Nice thing about aluminum though is that it’s relatively cheap, I think this is the stock I used to make 4 fins. https://www.ebay.com/itm/2-Pieces-1...-Mill-Stock-/360694209917?hash=item53fb0cdd7d
 

Bat-mite

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Has anyone ever made a Level 3 attempt in a 3" airframe with a long-burning motor before? That sounds like a unique combo, and quite the opposite of the low-and-slow that most people go for.
 

slaak

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Has anyone ever made a Level 3 attempt in a 3" airframe with a long-burning motor before? That sounds like a unique combo, and quite the opposite of the low-and-slow that most people go for.
I know Adrian A had a similar rocket planned for his Level 3, and his rocket is where I got the parachute cannon idea for my design. But it doesn't look like he ever made the L3 flight with that rocket?
https://www.rocketryforum.com/showthread.php?26383-Level-3-high-performance-design-and-build-thread
 

slaak

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I did something similar to you....had AL fillets machined by Eric@ Baddazz for the airfoiled fins to slide/glue into.
Wanted all AL, but that would have been to costly.

I see exactly where you are going with this & concur, much better 1 piece.

View attachment 322898 View attachment 322899

View attachment 322900 View attachment 322901


View attachment 322902

Unfortunately the N-1000 Research motor catoed and went through the airframe around 200ft. ending my 50,000 ft attempt......i'll be back! LOL
Did you blend the body tube side of that aluminum bracket to match the body diameter? I was thinking id just tape some sandpaper rough side out to a piece of body tube and run the fins back and fourth until the radius matches but am looking for a better/quicker way if you know of one
 

bclark989

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Has anyone ever made a Level 3 attempt in a 3" airframe with a long-burning motor before? That sounds like a unique combo, and quite the opposite of the low-and-slow that most people go for.
I had a Mongoose 75 kit that I hoped I might cert on with a CTI M840, but level 3 is still a ways away for me, so I sold the kit. Would love to build an MD long burner some day though.

This looks super awesome, slaak. Keep up the good work!
 

slaak

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I did some Alodine application on a test fin today to see how it would turn out and well it turned out pretty ugly. The application guidelines said it would be kinda blotchy and runny if you applied it with a brush and that exactly what happened, covers the Al just fine, it just looks bad. Its supposed to have much prettier results if you use an immersive method to apply it so im going to blast it off and try that after this aluminum surface prep stuff comes in the mail.

Also did some test beveling on the leading edge of my test fin to see how I like it, turned out pretty good and should be very repeatable from fin to fin so i think im going to give it a go on the real fins. Attached some pics of the machining process for beveling the fins just because.

Block on the right is set parallel to the y-axis, blocks on the left are clamped to set the leading edge parallel to the y-axis when the root is flush to them.
IMG_20170626_175754.jpg

IMG_20170626_175808.jpg

scribed 0.3" (0.3" and 4.5 degree head tilt will leave .03 leading edge thickness) from the leading edge and clamped into place.
IMG_20170626_180750.jpg

head tipped to roughly 4.5 degrees.
IMG_20170626_180908.jpg

turned out good enough for a test run, only took about 5 minutes to do the actual cutting after my blocks where set so im happy with the results. (side note its really hard to take a picture that shows the pointy edge of a fin.)
IMG_20170626_181613.jpg
IMG_20170626_182518.jpg
 

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Beautiful work. :pop:
 

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Anodize the fin surfaces that will see adhesives.
 

Nytrunner

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(side note its really hard to take a picture that shows the pointy edge of a fin.)
Set up your shot looking along the edge from the tip towards the root. With a cellphone camera, that should place the point in a better focal position.
 

slaak

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Anodize the fin surfaces that will see adhesives.
I was planning on Anodizing the fins originally but pretty quickly realized I didn't wasn't to deal with or have to worry about disposing of the chemicals involved :puke:. researching it also brought the boegel ac-130 stuff to my attention and the studies that the airforce + boeing did seem to conclude that if you properly sandblast/abrade the aluminum followed by their prebond treatment and some primer it creates a bond just as strong as a mill spec anodized surface.
Another reason I moved away from Anodizing is because the data sheet for the adhesive I want to use claims it will have only half its strength on anodized Aluminum vs blasted + primed(2,100 psi vs 4,800). but I am not really sure how this could be and have a hard time believing it unless its some type of chemical incapability.
 

OverTheTop

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properly sandblast/abrade the aluminum followed by their prebond treatment and some primer it creates a bond just as strong as a mill spec anodized surface
Sounds very process dependent. That would concern me. Professional anodizing may be the way to go?

the data sheet for the adhesive I want to use claims it will have only half its strength on anodized Aluminum vs blasted + primed(2,100 psi vs 4,800)
This somewhat takes the shine of the idea of using anodizing anyway.

Decisions, decisions...
 

slaak

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Sounds very process dependent. That would concern me. Professional anodizing may be the way to go?

This somewhat takes the shine of the idea of using anodizing anyway.

Decisions, decisions...
Its going to take a lot of prep work and care to get the Aluminum properly prepared for the bond for sure, im slightly concerned after how the Alodine test I did turned out. But I figure in the least as long as I sandblast the Al properly(not too hard) and do a chemical degrease bath then I should be most of the way there to a good strength bond even if the prebond primer doesn't give its full benefit. Luckily there is quite a bit of process related performance testing with less than optimal conditions (like my kitchen/work area) on the primer though since its kinda designed to be used in repairs when you cant anodize the entire part.
 

slaak

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Update time!
I ended up re-making all my fins... I had been planning on making this rocket have 4 fins because that would allow them to be shorter, but I played around in open rocket and realized it was only really buying me .25" in height. I also would like to tower launch this rocket and I have no desire to build a tower for a 4 fin rocket when all my other rockets are 3 fin so the tower would not work...

So in the spirit of "high performance" this rocket needed 3 fins to minimize surface drag and i also made them slightly swept and slightly shorter, openrocket is showering ~2.15 stability margin, more than enough yeah?

With the fins finished this weekend today I used the day off to do some surface coating on my Aluminum parts.
The combination of a 220 mesh sandblast -> alumiprep 33/phosphoric acid --> Alodine 1201 turned out really well i think.

The bulkheads look amazing and nearly flawless (I did them last and had figured out a few tricks by then) and the fins turned out pretty good in there own right, I need a stronger compressor so that I can sandblast more evenly right now any high or low sandblast coverage spots show up in the final product and that is easy to see on the fins with their high surface area. Enough text here's some pics.

Some dark and light spots on the fins but good chromate coverage overall. Think this has to do with my lack of sandblasting skills.
3fins post coating.jpg

not quite the even gold/brown Alodine is supposed to have but that is ok as long as its protected form oxidation.
fin post coating.jpg

I was hesitent to do the bulkheads at all but im very happy that i did and love the results.
aft bulkhead coated.jpg

Almost looks like a render! (no Photoshop here) I love the smooth golden surface look. Its even functional too!
aftbulkhead coated angled.jpg

FWD bulkhead has some blotching but its not going threw NASA inspection so that's ok.
fwdbulkhead looking aft.jpg

FWD bulkhead looking AFT
fwd bulkhead coated.jpg

Alodine always looks more golden around the edge, i think you might need a bunch of agitation in the Acid bath to make sure it etches evenly.
aft bulkhead FWD emd.jpg
 

dhbarr

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Smexy! What's your stability margin at peak velocity and/or maxQ?
 

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That is some real nice machining and a sweet looking bird.
If you havent got your TAP's etc., lined up for your L3, I would get that done now. Most will want to see a plan, etc., BEFORE you start building the rocket. At the moment, you are in the stage of manufacturing parts for that rocket, so, for the moment, I think you are OK. Once those parts start going together, that is when 'the build starts'.

Good look.. subscribed.. popcorn... everything
 
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