L1 Cert choices

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CPUTommy - thanks for the post! Excellent L2 cert flight and a great video! My heart sank when the Scarab seemed lost - and maybe jumped as much as yours when you found it. How cool was that? Thanks for including the altimeter readouts and the L2 check-off. It was a very personal, fun video.

The intro... the sound of helicopters... I love the smell of napalm in the morning... then I was just thunderstruck at your excellent choice of background music! Best lead guitar riff in years (RIP Malcolm). Fantastic flight; your ear-to-ear grin says it all.

Great paint on the Scarab, too. I'm feeling a whole lot better about that choice (with its 54mm av bay, lol).
 
I think you have two conflicting goals, but they’re obtainable in one of two ways-

a 38/29 that is definitely under 3.3 pounds, and will break a mile on a large 29mm I. Not the craziest, but exciting

I didn't realize it, but I had Jim's BH38 ORK file already. I didn't realize it was his - I read his thread a couple weeks ago, saved the file, then kept reading build threads. I saw it reading his build thread this morning and got a new copy to make sure I hadn't corrupted it. From what I see, it won't need to be a 38/29. Using Jim's build weight and 38mm motors, an AT G77 reaches 817', a G64 hits 1050' and a G69 goes to 1262'. CTI G46, G60, and G78 reach 980', 1262' and 1383'. All of them weigh less than 1400g so they are Class 1 with these motors. But it's a BH38 that sims to 16K with a J510. Pretty amazing!

Using 38mm motors for the two larger rockets of the three boatgeek suggested lets me buy one CTI 38mm startup kit with 3 and 6 grain cases and I'll be equipped for both. An AT 29/40-120 would cover a lot of ground for the small rocket.

Jim, I re-read your build thread again. Great thread! I only have one question (all my other questions were already answered). Is the ORK file still valid for the BH38 as it is produced now?

Thanks to everyone who has participated. I've learned a lot, met a lot of nice people, have a lot more options for the future, and know what I want to build first. Success!
 
There are a few of us on here that are in Sacto, and members of both groups. Eric, QQuake, myself, and quite a few others. SARG does limit to 1500' and the field recovery is a bit tricky sometimes with the sizable pond/lake usually in the downwind direction. I believe the limit of 1500g applies. G motor max. There was a G138 at the last launch, so there's that. It is a great time tho. LUNAR last weekend was awesome as well and gives us the opportunity to fly the bigger kits/motors. I had the Mach 1 Portia and a few LOC kits that flew. If you are looking for a good L1 kit to fly at both sites and stay under the 53 Oz limit, I'd recommend the Loc EZI, Madcow DX3 or a lighter weight 54mm FG kit (take your pick of many). All of these would have no issue flying on G's and staying below 1500', allowing for L1 cert. and moving on up to 38/600 reloads if you so desired. Come say "Hi" at SARG on the 24th if the weather holds. I'll be the one with four little kids that all have 1082192819929108 rockets and will talk your ear off.
 
Jim, I re-read your build thread again. Great thread! I only have one question (all my other questions were already answered). Is the ORK file still valid for the BH38 as it is produced now?

Wildman just began using a new spiral wound 38mm nose cone.[might even have metal tip, so you can screw in an E-bolt for recovery]
Mine had the molded version. As far as I know that would be the only difference. You would have to make a quick call to him to verify any other differences.
 
Ahh, didn't see your goal to break one mile on large 29mm. A LOC Hi-Tech will do both of those... Will do 1300' on the G76-7G hobbyline load and the I200W will get you 3200'-ish, but it's a 38mm mount and will hit a mile on most 38/600 loads.
 
By the way, if you have access to a lathe it is very simple to make a 38-29 tailcone adaptor. If you don't a simple one can still be made with a couple of centering rings [coupler], coupler, MM tube, and centering ring that acts as thrust plate against rear of tube. It can be paper/phenolic/fiberglass. I had some scrap glass laying around, but have made others with cardboard.

I made one out of wood. Glued some shock cord to motor mount tube [Y-harness] & it's held in place by rear rail button screw.

To hold motors in place just wrap tape around front of case after installing into adaptor. Insert and screw in rail button done & done!

DSCN5528.jpg DSCN5530.jpg

This one is only 4in long. That's a 3 grain motor case. I use Hobbyline G-64's in this also.
 
The black hawk would certainly be an awesome project.

Some points to consider (not meant to dissuade, but so you can consider before getting the box)

- motor retention. On an MD it’s either friction fitting with tape (my preference) or mounting a hardpoint internally and using rods to space motors of varying size.

- the Blackhawk is a screamer with Timy fins. At M1 no big deal. At lower speeds the small fins will correct angle of attack differently than larger fins at low speed. Not a dealbreaker, but be aware of it if it’s windy and your using a G with lower average thrust. It’ll be stable, it nice and long.
 
You said you were interested in Mach 1 Rocketry, here's my build thread on their Portia, which I just maiden launched at LUNAR last weekend on an I357. Great flyer, but comes in at 80 Oz loaded up. Too much for SARG.
https://www.rocketryforum.com/showt...ocketry-Portia-dual-deploy-sport-rocket-build
 
Hello swatkat, thank you for saying hi. I didn't Google the SARG site closely, but the thought of a water landing is a bit unnerving. I bet it leads to overcorrection in the rail angle. I missed the last SARG launch, somehow thinking it was Sunday (?). Prior to that I'd only been watching hybrids on YouTube.

I assume you do, but have to ask if SARG has 1010 launch rails? How tall are they? I want to have the speed of the rod calculated properly. Probably will use fly-aways from the start to keep things clean. I'll look at your suggestions after I take care of business, and have the 1.6" Madcow Tomach on my personal list as well.

Erik PM'd me, asking about my plans for L1 Cert since Snow Ranch shuts down when the grass gets dry. That was good input, as the BH might take too long to build. So maybe I'll have to revisit the decision and look for something more do-able in the time frame and take the summer to practice filleting and make the BH a good build. I would like to have L1 for LDRS, which I heard Saturday was at TCC this year. That's "too good to be true" or certainly too good to pass up. Or I could fly the L1 Cert flight at LDRS, which certainly would be memorable. Although no cows.

I'll look for you and your family on the 24th.

Oh, WRT a mile on 29mm, I messed up with OR. I was looking in the low 38's and double-clicked to select. Turns out that kinda scrolls the list then selects a different motor, so I ended up with a couple 29's in the BH38. Unintentional. But maybe a 38/29 is a good build for the time frame rather than an MD 38.


Jim, I'll check with Wildman and post any details on your BH thread along with an updated ORK file using the new NC. I put a 12" 0.8 Cd drogue in it so it sims properly, but it's otherwise unchanged.
 
David, good points. It has about 5.5 cals of stability with a G69 and comes off the rod at 44 FPS. That seems pretty good, but I don't have the experience to draw on.

Swatkat, congrats on the maiden. Fun to see and consider new products.
 
By the way, if you have access to a lathe it is very simple to make a 38-29 tailcone adaptor.

Good idea, Jim. No lathe, but maybe the CNC router could cut aircraft ply to the basic shape. #8 set screw to hold it in place. I was thinking of using a fly-away rail guide. The big J510 you set up goes 1000' higher without rail guides.

How hard is it to do a decent fillet? I've bent some FG wings and fixed them. Do the skills transfer, or should I make practice fillets first?
 
One other thing to consider is the cost of motors. For the same impulse, a smaller motor diameter tends to be a little cheaper. It's not 100% universal, but it's a good rule of thumb.

Re: fillets, you'll just get better as you go. Your first rockets are probably going to be a little rough in a lot of ways. Your fiberglass skills will transfer, but there's a learning curve too. A few test fillets won't hurt. There's a piece of advice for people who are planning to build a sailboat to sail around the world--build the dinghy first. Once you build the big boat, you'll save far more money and time than the dinghy took by not screwing up as much. Same thing here. Build a kit that you like that can be your truck rocket. Not necessarily beautiful, but a solid flier. My 54mm/29mm rocket fits that role.
 
boatgeek - "Build the dinghy first." Very wise. In engineering the parallel is "Make it work, then make it work well." Thanks again for the wise advise as I consider all the information that people have offered.

For hoots, from the Alien Interceptor page of the Mach 1 site, "Note: This rocket does not actually intercept aliens during an invasion. If you were to be invaded by aliens from another planet, call the U.S Air Force. Or better yet, lay off the booze." Gotta love a company with a good attitude!
 
My MAC Zodiac is a few inches longer than stock per my request. Without a motor it's about 1300g (thats all electronics, cords, chute, etc)
31099051972_cea2fc0860.jpg
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My MAC Optima I asked Mike to cut out of carbon for me is about a kilo less motor. (Also a 54mm airframe with a 38mm mount)
27341086899_91214447ac_z.jpg


I'd fly either of them on a G76G. (aerotech load for the 29/40-120 case)
simfile1088_650x350n.png



AT G80 isn't a bad choice either-
simfile2013_650x350n.png


The reason I posted the graphs was to also show this next one for the AT G69 (38/120 load)

simfile905_650x350n.png


simfile1318_650x350n.png


When you get into flying toward the heavier end of rockets on G's, you want to not just look at the average thrust, but the thrustcuve itself. This will show the initial thrust, which is important for getting speed off the rail, and why I love the G76G load. The lowest thrust to weight ratio allowed is 3:1. Most people want to see 5:1 for safety. Many debates are had if it should be initial thrust or average. I like it as high as I can get it, so i've never really gotten into a "how low can you go" situation. Other than flying 1500g rockets on AT G76's and loki G80's in low wind.
 
How hard is it to do a decent fillet? I've bent some FG wings and fixed them. Do the skills transfer, or should I make practice fillets first?

Not hard... biggest thing is getting the epoxy at the right times. Lay it in when it's just a little thickened, and pull the tape before it cures. Go too thin, the epoxy runs flat. pull the tape too late, and you'll have ridges.

I lay the epoxy in with a stick, dip a section of 3/4" PVC in alcohol, pull it down the fillet, wait a short bit, then pull all the tape.
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David, two very interesting posts. I didn't see the Optima on the MAC site - I wonder if it was renamed or discontinued. The Zodiak has very nice lines and the weight speaks for itself. It is made of phenolic. Even the spell-checked doesn't know what phenolic is! :) But I have Googled it and read about it. It has good properties, but I don't understand what it feels like or how it works. I feel like I *must have* held the material. I know the word from years ago. What I could not find at all is an answer to "Why is this a good material for rockets?" If you can point me to a thread, thank you. If I missed something, this has been a floodgate of information.

If you've ever worked HDU on a CNC router, it behaves one way while wood behaves another and XPVC yet another. How would you characterize its workability... what material is similar?

Not hard... biggest thing is getting the epoxy at the right times.

Thanks. Blackjack Jim has a way of making everything look easy and come out perfectly. And then I think it's Jim Jarvis who did a T2T that looked like art in composites. That's another topic for a future discussion, though.
 
David, two very interesting posts. I didn't see the Optima on the MAC site - I wonder if it was renamed or discontinued. The Zodiak has very nice lines and the weight speaks for itself. It is made of phenolic. Even the spell-checked doesn't know what phenolic is! :) But I have Googled it and read about it. It has good properties, but I don't understand what it feels like or how it works. I feel like I *must have* held the material. I know the word from years ago. What I could not find at all is an answer to "Why is this a good material for rockets?" If you can point me to a thread, thank you. If I missed something, this has been a floodgate of information.

The Optima is an Estes rocket from the mid 90's. I'm -mildly- obsessed with it. I have two originals built, two NIB, and like 8 or 9 clones of various size. It was a custom built "kit" from files I sent Mike.

the Canvas Phenolic..... from what I understand, it's resin soaked canvas. I'll try to get some more specific info on it. It's strong, stiff but some flex. It's lighter than FG, But where you can fire FG into a brick wall and it'll come out the other side, canvas won't. Personally...I don't go for many brick walls. Each material has it's place. The couplers and AV bays MAC makes could double as nuclear bunkers.

The fins are very similar in feel and working as glass.
19566735401_707cd8892f_c.jpg


The tubes.... I haven't had to work them much. MAC cuts them, I glue stuff into it. You're looking at power tools for major cuts. Sandpaper by hand for surface prep.

a few galleries of canvas-
https://www.flickr.com/photos/31757945@N05/albums/72157655395209742/with/19566735401/
https://www.flickr.com/photos/31757945@N05/sets/72157672967926033/with/32075193561/

Hard to give a good feel for it in photos. It's waterproof, which is a plus.

I disassembled my 3" Villain about 50' off the ground. 54/1600 motor popped. The av-bay took a hit from the forward closure of the motor, but survived as did the electronics. payload deployed the DD charges and drifted down. The booster turned into a stamp collection, understandably. The fin can shockingly survived the ordeal, aside from the motor mount itself, which the flared motor casing blew itself down and out through.

33563938413_e31bb310de.jpg
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In the toughness defense of canvas.... I once had my chute drag the villain about a half mile through a field, plowing it the whole way with not so much as a ding-

[youtube]mXfD646uURc[/youtube]

Dragged from X to O lol
26550040091_c10c87a731.jpg
 
SARG does have a 1010 rail, it is SHORTER than the LUNAR ones tho. I believe the LUNAR ones are 7ft (or thereabouts) and SARG is 5'.
 
SARG has the bigger rail pad, and at least one longer rail for the smaller pads. They don't usually use them at Gibson Ranch, though.

P1030885.JPG

P1030889.JPG
 
SARG does have a 1010 rail, it is SHORTER than the LUNAR ones tho. I believe the LUNAR ones are 7ft (or thereabouts) and SARG is 5'.
This will hurt exit velocity off rail. It will matter if stability is high and a gust of wind knocked the rocket with a lower exit velocity. I had an RSO explain that the rockets needed over a 45 fps. Excess velocity off rail is wonderful. I've made a four foot rail tower no rail guides for comp multistages. We could pack that tower into a car sideways for Utah trips. We had to sim rail lengths and pick motors wisely. A fast burner had no issues. Some of the slowest burning motors weren't useable to us on a 4ft rail with MD. Just trying to make a point here.
 
Water and tree landings at SARG site happen sometimes. But there is lots of recovery area if you work with the winds correctly. And the club does have a long extendable rod to aid in recovery. And I can bring an 8' rail if needed.

20170225_130857.jpg
 
David, thank you, I laughed for several minutes watching your video. The photo and your description helped me understand phenolic a lot.

Eric, nice to know. I'll be just a visitor at the next launch. Seems like fly fishing tackle could be helpful there! Nice looking launch site.
 
Hi David,

You presented a lot of new information for me to process. Let's do thrust curves first. I had looked at them, but I hadn't carefully compared the curve with the various performance characteristics with a given rocket. I did so this morning with the BH38 because its OR file is set up the best of what I have.

The BH is 1174g no motor in the OR file. Your first two motors simmed nicely: G76 off rail at 61.6 FPS, apogee 1033. Compare this to the G64 I had in my list; almost the same apogee but off the rail was only 48.3. The G80 you listed wasn't quite as good as the G76 (I'm learning so much); apogee went up 50 feet but velocity off the rail down to 52 FPS.

Your third thrust curve was for the AT G69. While its apogee is 1262 (+200), it comes off the rail at just 44.4 FPS. Would it be fair to say that this motor would be reasonable for a large-finned rocket but inappropriate for the small-finned BH? It seems there must be a place for all these motors, and it does give more altitude.

Now, on to the CTI motors. You have a G46 there, kind of a shame because that's their lowest power 38mm G motor, but it has an obvious thrust spike at ignition. That spike seems to be fairly common with CTI, at least for those I've looked at. This is a CTI G106:

G106.png

The G106 has a fairly pronounced spike. Apogee 1357', off the rail at 51.5 FPS.

G115.png

The G115 has a less-pronounced spike, but still leaves the rail at 55.7 FPS and reaches 1407'. Both seem like worthwhile motors; the G115 being better for a BH.

Is there any reason to prefer AT or CTI in general? Or is it more a matter of personal preference, mounting style / case design, or suitability for a particular rocket? Is there a reason for the early CTI thrust spike, such as vel off the rail?

- the Blackhawk is a screamer with tiny fins. At M1 no big deal. At lower speeds the small fins will correct angle of attack differently than larger fins at low speed. Not a dealbreaker, but be aware of it if it’s windy and your using a G with lower average thrust.

First - thank you for bringing up important design points. I still have no way of judging what is a suitable flight plan for the small-finned BH. CJ had about a dozen motors already in the OR file. I161's leave the rail in the low 50's; I211 is 66.3 and I301 is 63.2.

Would it be correct to believe the G76, G106 CTI and G115 CTI would have sufficient velocity to respond well to wind gusts, as they leave the rail at similar speeds to the more powerful motors?


I'm not suddenly focused on the BH above all others. It's more like I'm trying to comprehend the nature of your caution and what steps can be taken to avoid possible problems, using the only decent OR file on hand.

The Zodiac is a different beast, being 54mm. Do you have an OR file for yours? How long did they cut the fin can? I'm going to call MAC and learn more about phenolic. There's surprising little to be found on the net - or I've done a poor job of searching.
 
CTI or AT, in 29mm, AT has more options that ship without hazmat. In 38, both have a staggering selection, Go with whatever you can get locally. Each motor has different physical and chemical properties. Both companies have progressive, regressive and neutral burn motors, big spikes, slow building, flat etc. Finding the right motor is a big part of the fun. Don’t get too caught up in subtle differences, as each physical motor may vary a bit for several reasons.

Theres several types of pheonlic i believe, MAC has theirs custom made for them, and calling or email will get the best info on it.
 
When we’re on motors... one other hoop.

G motors are all well under the limit for class one. That stastifies the FAA.
Due to NFPA, TRA, and NAR rules/codes/regs/wigee boards, any Motor with over 80 Ns average thrust or an sparkie (skid mark, darkmatter, propellant X, etc) requires L1 cert
 
CTI positives: easier to assemble in the field, some more variety in propellants depending on the size range, a starter kit including a couple of spacers lets you fly lots of different loads, easy to adjust delays
CTI negatives: All hazmat shipping ($/box if you buy by mail), availability crunches due to a factory fire a couple of years ago, no single use options

Aerotech positives: More non-hazmat loads, good availability, single use options
Aerotech negatives: More difficult assembly, some cases don't have many propellant types, can't use spacers in some cases

Reasonable people can disagree about whether Aerotech and CTI are cheaper per flight. There are tradeoffs between casing cost and motor reload cost, and I don't remember which is easier. Also, hazmat shipping is a non-factor if you can buy from a vendor on site. As said above, if your launch site has a vendor that supplies one or the other, go with that.

I generally fly CTI because my field time is more valuable to me than the cost of hazmat shipping, especially buying a bunch of motors at once. That said, last time I launched, it was an AT single use F and a CTI G.
 
At some point you’ll see a Loki motor and think “that’s awesome I want that!”

Unless CalFire changes its rules, they’re unlikely to be legal for private use anytime soon :(
 
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