"Fav'rit 2 B" - Build and Flight Log

Now we are to the point in this build where I start to really ask some questions. The first group of these relates to vent holes. Yes, I have done a search and there are definately opinions, lots of them, many somewhere between divergent and outright opposing.

I found the altimeter bay vent hole recomendation page, since this is a 5.5" internal length, 2.9" diameter bay three 1/8" holes appear to be plenty good. I will likely make at least one bigger so I can actual arm the altimeter (I will probably use the rotary switch many here like). So this raises a question.

1) Should I make all the holes the same size, or just the one to arm the altimeter through?

Next, vent holes in both airframe compartments. I think this rocket will spend its life (a long one I hope) topping out between 2k and 4k, so with a 3" ID that is some actual pressure I want to account for. Keeping this in mind I don't want to use shear pins in the lower section and I really don't want to make that connection real tight either. So assuming I am set on vent hole(s) the below questions arrise.

2) What size should the vent hole be assuming I only want one in each section?

3) where in each section should they be located? I assume near the joint you don't want to seperate, but I don't want to be wrong here.

Thanks in advance for the advice.
-Chris

Minor progress today...got the sled made. Cut this out of 1mm G10, plenty strong it appears. I cut the 1/4" launch lugs I'm using to hold this to the all thread to match the internal length of the bay, and tacked the plate approximately in the middle with CA while the bulkheads and all thread were assembled and leveled by laying the all thread perpendicular across a 4x4. I have read multiple accounts of lawn darts and other sub-optimal recovery attributed to the sled coming loose and disconnecting sometime important in flight. To ensure against this I drilled a series of holes around the lugs and wound a piece of nylon cord around the lug, knotting both ends. Then when epoxying the plate to the lugs I made sure to coat the cord completely, so even if the plate and lug bond fails there is a piece of nylon there as backup.



Other than that I got the terminal blocks attached to the bulkheads and smeared on some bondo to the aft tube.



Captain, thanks for the vent hole suggestion, I figured it didn't need to be much but was unsure what would be sufficient.

Again, this was an iPad photography night, so sorry for the poor quality pics. I'll get good ones for less mundane steps.

Ok, haven't been keeping up on here (not working on this project all that much, building a Quest Harpoon-24mm MM, ordering a Baddazz Lil' Mizz Judy, and planning for a potential BT60 Sea Dart scratch build have distracted me...I think I'm at full blown addiction stage), but I will post pictures of "Favrit 2 B" progress soon. For now I have two questions:

1) How much coupler overlap should you have between the aft (motor containing) section and the altimeter bay when no shear pins are to be used to keep them together? If I center the vent band in the coupler I will have 2.5" overlap, I would like to reduce that to 2" so even a snug fit will seperate without too powder required.

2) How do I take the component analysis info that Open rocket gives me and calculate drag seperation force in something I can comprehend?

OK, off work today, so may catch this up.

Starting with the rail buttons. I made my life easy for the aft rail button by making a 3/4" think target on the penultimate centering ring, so that just needed drilled out and a threaded insert put in. Putting in the insert was a bit frustrating, but once I put a really long screw in it and used a vinyl lock nut to make sure the insert turned not just the screw everything lined up nicely and went in true. While this method worked I am intrigued by the Dog House rocketry tool discussed elsewhere on TRF.



I made up for this easy aft attachment by wanting the second rail button nearer the CG than the forward most CR, so this required a backing block be made to hold a T-nut so I can change out the rail button easily in case of wear. I dearly hope this rocket outlasts its rail buttons, so best to be prepared. I cut a rectangle of 1/4" bass wood and sanded it to match the inner curvature of the tube. I wanted to make sure none of the recovery equipment would catch on the block, so I sanded a curvature into each side. I made the aft side more gradual than the fore...probably didn't need to do anything to the fore side, but why be incomplete. Next a hole was drilled and the T-nut epoxied in place.



Attachment was, let us say challenging. I drilled the appropriate hole for the 8-32 screw and then fed the block down the tube, manipulated it around with a piece of 1/8" rod, and was able after supprising few attemps to thread a long 8-32 screw onto it. I sat this on the table so the screw held the block in the air and put down a relatively thin coat of 5 min epoxy where the block would seat. I then pulled down on the screw to hold the block tightly in place while the epoxy set. As I did this I would back the screw out a half turn or so every 15 sec to make sure the epoxy wasn't grabbing it, but it stayed clean. Once the block was in place I smeared a bit more 5 min epoxy around the block basically filleting it to the tube. This had the added benifit of smoothing out the attachment point hopefully reducing further the chance anything will catch on deployment. Sorry the photos on this step are bad, it was an iPhone photography night.

I decided to place the vent band in the middle of the coupler, so I marked this area off and started getting the aft section of the coupler smooth so it could slide easily from the aft body tube upon drogue deployment. When I sanded the coupler with 300 grit I still had a fuzzy surface that really increased the friction with the tube. I smeared a thin layer of Titebond II on the entire aft end of the coupler, waited for it to dry, and sanded smooth. This gave a much better result, very smooth and easy (not too easy) slip from the aft tube.

I then attached the vent band by carving little grooves into the coupler and completing the attachment with 30 min epoxy. I used the appropraite body tubes to ensure that the band was properly alligned. This is actually the second attempt...the first vent band had to be pealed and sanded off when I tried Titebond II and it bit way too early and unevenly (read as: really crooked vent band). I then drilled my vent band holes (3 x 1/8") this is a bit more than I should need for this coupler but I like breathing room. I drilled the holes by starting small, thin CA, sand, repeat, repeat until I had really nice holes.

Having practiced my hole drilling technique enough to this point I felt confident drilling the vent hole in the aft tube at this point by the same method. Don't remember size, I wrote it on the tube, then primered over it before I made another note.



So I decided to blow the nose cone for the main seperation, so I needed a way to ensure that the altimeter bay and upper body tube didn't seperate when the charge went. I could just create a snug fit, but I like the look of a few screws here and there in a rocket, so I decided to attach the tube with 3 X 8-32 black oxide screws. To do this I put backing blocks with T-nuts inside the altimeter bay. These were made the same as described above, but are smaller and not tapered as there was no need here. They should also provide a nice reinforcement for the bulkhead plate when seating. The attachement holes were done by marking the upper body section, then alligning these marks with the vent holes in the vent band, taping the two pieces together and drilling the holes large enough to accomidate the screws. I then attached the blocks to the altimeter bay by the method used above, pulling them tight with a screw threaded in until bonded.



I was very relieved when all of the holes lined up again.



Lastly I drilled the vent hole in the upper section and made holes for 3 x 2-56 shear pins. These holes were drilled through into the nose cone as well.



Now everything is ready for primer except the nose cone.

qquake2k said:

I flood couplers with thin CA then sand/polish them on the lathe.

https://www.rocketryforum.com/showt...cratch-build-Centurion-XL&p=313254#post313254

Click to expand...

My kingdom for a lathe, and a different kingdom big enough to put a lathe in.

Cl(VII) said:

My kingdom for a lathe, and a different kingdom big enough to put a lathe in.

Click to expand...

You don't really need a lathe, you can sand them by hand. I'm just lazy.

I know you can do these things by hand, but I have serious shop envy every time I read one of your threads. I go through a lot of sandpaper. I think well over 50% of the time on his project has been hand sanding, tedious but I only have a small palm sander (for now anyway). I think the first tool I add will be a band saw, followed by a drill press. I get by with my Zona saw and Dewalt drill, but some bench top tools would really simplify things. Of course this would probably accelerate my building and which would of course accelerate my spending. So perhaps I should just keep my hand tools.

Long time, much work. I have been priming, sanding, bondo, priming, sanding, bondo, priming, sanding..... Well today I got the base metal done on the whole thing. I used rustoleum automotive primer and needed a little bit of bondo glazing putty here and there, but not as much as I expected. Used a crap ton of primer though (3+ cans), this was largely an OCD issue admittedly.

My youngest got to name the rocket, he also got to pick the color scheme: Green and Purple. I figured I might as well go all the way to gaudy and go with the duplicolor base metal, followed by annodized colors, then Clear Effex over that. Think "Intergalactic Space Pimp" and you'll get the effect I'm going for. Anyhow the the base metal is now done, so below is the most gratuitous rocket porn I have generated to date.


Min-pin added for size comparison...I was thinking of shooting the picture with no other objects in it for reference and claiming that was a full size Pit, but I couldn't frame the shot I wanted in my neighborhood. The rocket comes in right at the planned 5 ft.


The fore set of fins...really happy with how these came out.


Really happy with how the fillets came out, so many pics included.

General thoughts and comments:
- This only took 1.5 cans of base metal.
- I love this product, the specs break up the surface for your eye and hide very tiny imperfections (not big ones, but the OCD took care of most of those).
- This is a tough product to use, it takes practice...this is the third rocket I have used these products on, and the first time I am approaching really happy with it. We'll see how the color layers go.
- This paint job will cost more than the rest of the rocket, you may now roll your eyes, but it's what I like so here we are.
- I know I need to have my pool tiles replaced, but I spent it all on rockets. I made my choice and I stand by it, the thing still holds water and effectively tires out the children ensuring peaceful bed times.
- Yes, I know the fence needs replaced...see above.

Below is the color scheme I'm probably going with, I'm going to leave the fins, switch band, and nose cone metal flake silver. I may preserve a band or two of silver around the body tubes, but these pigment layers are really hard to get even, and I'm worried about pooling around the tape, so I'll likely just paint the entire tubes.

Rocket is looking really nice!!!:headbang:

I really like the way the fins came out. I got similar results with paint color selection when I let my 2 boys pick the paint color for their room. Next time I'll let them pick the color for a rocket. Looks much better on the rocket:wink:

Keep up the good work.

PAINTED!!!!

For being completely unenthused with my 2 year old design advisors choice of colors I have to say I like it, and I will certainly be able to track it in flight.



I tried a trick I saw here on TRF (can't remember who's thread) and after I put down the masking tape on the fins I gave a light coat of clear and let it dry about 45 min before spraying color. This gave really sharp borders between the green and silver on the fins. So, THANKS to whomever I stole that trick from.



One product that I have really come to like is Duplicolor Clear Effex, which is a clear topcoat with particles in it that give that prismatic look which is REALLY prevalent in sunlight. It's pricy (~$12 / can at AutoZone), but for bigger, special projects it is a must now. It's kind of like Homer Simpson only wanting to use a "Star Wipe"..."Why have hamburger when you can have steak, Lisa"...indeed, Homer, indeed.



The process:
1) Lots of primer, sand, primer, bondo, sand, primer, sand..... (3+ cans)
2) Duplicolor Metalcast Base Metal (~1.5 cans)
3) Tape
4) Duplicolor Clear coat (spritz)
5) Duplicolor Anodized Purple/Green (1 can each)
6) Duplicolor Clear Effex (~2/3 can)



Picture of cans, crossing fingers for advertising kickbacks.

All coats had at least 3 days drying time between, except the clear coat discussed above. This is really important for the color layers. They look really uneven and disappointing when I did them, then over the next few days they slowly changed to a uniform finish and tone. I said above that the Duplicolor Metalcast products are difficult to work with (sometimes just leaving them alone and trusting it will even out is the hard part), but the finish you get with them is really sweet. I have gotten numerous compliments and inquiries about the Red/Grey LOC Iris in the background which is done with the same products. As an added bonus the finish is brick hard, I have had that Iris come down on dirt road ruts hard enough I thought I broke a fin (probably would have if they weren't covered in 5 oz glass) and get dragged by the wind with shockingly little damage.

Once all dried I installed my railbuttons.com 1 piece 1010 buttons and black oxide screws to hold the payload bay on.

Now I have to get the AV bay rigged up for ground testing the charges, which I hope I can do at the DARS HPR launch next Saturday. With luck this thing will get to fly in Sept/Oct time frame, Disneyland trip next month zapping funds currently...that Mouse is brutal. Won't stop me from getting some nice "Favrit 2 B" vinyl from Stickershock though. On that note I have an email to send.

qquake2k said:

Wow, that turned out nice!

Click to expand...

Thanks much sir. Now lets hope I don't do it an injury ground testing Saturday. I got some good ejection charge advice last weekend from one of the DARS gents. I think I'll have everything ready for testing Saturday, that is if the postal service hurries up my Q2G2s.

Got my Q2G2s in hand, and just got an email from Mark...my vinyl is on its way. Apparently, my order could be done on his operating cutter. I'm genuinely excited.

Most exellent workmanship my friend ,and the paint and finish is about as good as you`ll see , smooth and sleek !

I`ve used those metalcast colors before ,very nice stuff, but I learned it hates high humidity when applying.Mine blushed a bit ,bit another light coat and brough back into the house cured the problem.

BRAVO !!

Take care


Paul T

It may finally be time for this thing to fly, and for me to get my L1. After some MUCH needed rain and the discontinuing of the burn ban we have a high power launch tentatively scheduled for next weekend. The motors are available, and I just have to get a few "i"s dotted and "t"s crossed this week to be ready.

Ok, after many missed chances caused by burn bans, rain, spouse back surgery, kid's choir performances, man you name it I funally got the chance to fly this thing and get my certification. I had a minipanic about stability early in the flight, so the night before the launch I added 4 oz of shot to the NC. I held it in place with 30 min epoxy, and then followed that with a generous helping of expanding foam to be sure it didn't go walkabout.

I flew with the HOTROCs folks on a beautiful, freshly plowed, expansive field. The rocket flew on a H-242T to 1209 ft, and deployed at apogee under the control of an RRC3. You could definately hear the motor backup about +2 sec. Came down on a 45" chute and landed safely after flirting with some power lines (which was the only serious obstacle for 1/2 mile in any direction.

I owe a special thanks to Robert Vanover who not only witnessed the certification, but also took some sweet pictures he has given me permission to share.

Thanks to those of you that have given me advice along this build, during my RRC3 learning, and last minute stability freak out. Particular thanks to qquake2k and the sodmeister (wherever he may be) I've learned alot from your prolific building and carefully documentation.

Pics, including my recovery crew.

Congrats on flight.
Looks like a great recovery crew

That is a beautiful rocket! Nicely done. Congrats on the flight.

Thanks, and yes I have the best recovery crew in the buisness, or at least the only crew that will put up with me. I don't know if the feeling was accomplishment or relief, but I'm happy with how it went. My improved mood may be from the fact that I got to spend an entire day in the sun for a change. I know many have said it, and North Texas isn't the worse place to spend a winter, but I am so sick of this winter.

Chris,
You rocket exceeded the requirements in every way, it was my job to sign off on that. I hadn't seen your build thread before the flight but it was obvious that it was solid work. I have an I357T you can have if you are ready to push it a little harder and try DD.

Robert Vanover

Cl(VII) said:

Ok, after many missed chances caused by burn bans, rain, spouse back surgery, kid's choir performances, man you name it I funally got the chance to fly this thing and get my certification. I had a minipanic about stability early in the flight, so the night before the launch I added 4 oz of shot to the NC. I held it in place with 30 min epoxy, and then followed that with a generous helping of expanding foam to be sure it didn't go walkabout.

I flew with the HOTROCs folks on a beautiful, freshly plowed, expansive field. The rocket flew on a H-242T to 1209 ft, and deployed at apogee under the control of an RRC3. You could definately hear the motor backup about +2 sec. Came down on a 45" chute and landed safely after flirting with some power lines (which was the only serious obstacle for 1/2 mile in any direction.

I owe a special thanks to Robert Vanover who not only witnessed the certification, but also took some sweet pictures he has given me permission to share.

Thanks to those of you that have given me advice along this build, during my RRC3 learning, and last minute stability freak out. Particular thanks to qquake2k and the sodmeister (wherever he may be) I've learned alot from your prolific building and carefully documentation.

Pics, including my recovery crew.

View attachment 167594 View attachment 167595 View attachment 167596 View attachment 167597

Click to expand...

Congratulations!
The paint job is beautiful! Love the Green.

JP

robertv2 said:

Chris,
You rocket exceeded the requirements in every way, it was my job to sign off on that. I hadn't seen your build thread before the flight but it was obvious that it was solid work. I have an I357T you can have if you are ready to push it a little harder and try DD.

Robert Vanover

Click to expand...

Thanks, Robert. That I357T would give it a fun ride, I'm definately interested as I plan on DD with this rocket for the next High power launch I get to. The test ignitors I had in the payload section Saturday both fired when they were supposed to, but I did get a small leak (read as ~200 ft drop in altitude for a fraction of a second) into the electronics bay when the apogee charge fired. I will probably make new bulkheads as I wanted to convert that bay over to accept my Missileworks sled anyway.

Congratulations on the cert flight. It sounds like you had as much fun with it as we did following it. I learned a lot from you as well. Thanks for sharing.

JP Morgan said:

Congratulations!
The paint job is beautiful! Love the Green.

JP

Click to expand...

Thanks. I really like the Duplicolor Metalcast, but it is relatively expensive and harder to work with thannirmal spraypaint.

Mr Rocket said:

Congratulations on the cert flight. It sounds like you had as much fun with it as we did following it. I learned a lot from you as well. Thanks for sharing.

Click to expand...

Thanks, and I glad you enjoyed the thread. I will say there are far more experienced, and skilled builders on here to learn from. I guess if I served the I'll ask noob questions as I go guy, so hopefully that helps anyway.

The big thing I learned between start of this project and today is to never overlook how stability changes over the course of the flight, and don't assume it starts where the little dot in OR is and gets better as fuel burns off, tha little dot is I think related to the max velocity, not the just cleared the rod velocity. This is a big deal for small fins, and I fear I came very close to doing some skywriting.