MADCOW 4" FRENZY CARDBOARD ROCKET... A BUILD THREAD #1

[TMJ]

How do you folks prefer to securely attach your shock cords to eyelets and 'U'-bolts? Simple knots, sewn loops and quick-links... or what?
Also... how do you go about determining the proper/safe tensile strength, and desired 'length' of the shock cord(s), themselves? My 'Y'-harness is surely much stronger than needed (3/8" Kevlar). I wouldn't want to use that for the entire length of recovery cording. What would be a good size/tensile strength kevlar shock cord for this Frenzy? I like the Kevlar 'cause it's fire proof.

 

[rharshberger]

How do you folks prefer to securely attach your shock cords to eyelets and 'U'-bolts? Simple knots, sewn loops and quick-links... or what?
Also... how do you go about determining the proper/safe tensile strength, and desired 'length' of the shock cord(s), themselves? My 'Y'-harness is surely much stronger than needed (3/8" Kevlar). I wouldn't want to use that for the entire length of recovery cording. What would be a good size/tensile strength kevlar shock cord for this Frenzy? I like the Kevlar 'cause it's fire proof.

I stitch my harnesses similar to the way John Coker does in his video [video=youtube;UkLopNaQddI]https://www.youtube.com/watch?v=UkLopNaQddI[/video]

The difference in my method vs John's is he uses a sewing awl, and I use a upholstery needle which is a little harder to sew with and I can't do the lock stitch but so far my own harnesses are several years old and multiple flights and holding up very well. Of course one could just go with ordering harnesses from OneBadHawk and having zero worries about whether the harness is made right, which is what I did for my L3 rocket and will probably do again for some other projects I have upcoming.

 

[TMJ]

Reloadable 54mm motors. I'm looking at Loki, but not sure what I want to do here. There are many, many choices and it doesn't seem as though the reloads are universally interchangeable. Let's open up a can of worms and start getting opinions on what motors would be a good 'all around' choice, and why?

 

[Flyfalcons]

You need to get an accurate sim of your rocket, figure out what kind of performance you want from it, and go from there. 54mm motors are mostly Level 2 size, so you may want to consider a 38mm adapter to start with, as you'll get more choices in propellant type and thrust levels within the L1 range. Again, sim it, figure out what motors give you the performance you want, then buy the hardware. I have a project about the same size as yours and I'm running the numbers for a lot of different motors so I can see which one or two cases will best fit my needs.

 

[DavidMcCann]

Reloadable 54mm motors. I'm looking at Loki, but not sure what I want to do here. There are many, many choices and it doesn't seem as though the reloads are universally interchangeable. Let's open up a can of worms and start getting opinions on what motors would be a good 'all around' choice, and why?

Well, a good starting point in Loki is going to be the 54/1200 case. Several good loads, a red, three whites, and a spitfire. I love the J820. They are all L2 loads though so you're talking another cert....which isn't a bad idea. They'll give you nice flights in this rocket, probably around 4-5,000'

The three brands loads, for most purposes, will not cross over into each others cases. Loki is different in that they use reusable graphite nozzles. CTI and AT use single use nozzles that come with each load.

Even at the "three grain"/ 54/1200 or 54/1280 size you're talking $75 a flight for Loki, $90 for CTI, or $90 for Aerotech. This is the point you need to look and decide how much you want to spend a flight, and how high you want to go.

 

[TMJ]

Sorry folks, I wasn't clear in what I was asking about... Prefered motor 'manufacturers' is what I'm looking for.

 

[DavidMcCann]

Sorry folks, I wasn't clear in what I was asking about... Prefered motor 'manufacturers' is what I'm looking for.

Loki. Scott is a perfectionist, and he makes every load. It's a small shop, but he works his ass off, and it shows. Aside from the quality, he is also very responsive to his customers. It's not unusual for him to call me up when I email him a question.

I also like using snap ring motor cases, as the reusable nozzles cut down on reload costs, and they can easily be used for experimental motors as well.


That said- at one point I couldn't decide on a manufacturer. So I didn't.

Recently I've been selling off hardware. For commercial motors I kept two sets of aerotech 29mm cases in 120/180/240/360, 6x 29/40-120's, Loki 38mm 120 and 1200, and a Loki 54/1200.
Still have the AT 38/1320 case, but likely going to unload that as well.

 

[blackjack2564]

Sorry folks, I wasn't clear in what I was asking about... Prefered motor 'manufacturers' is what I'm looking for.

Well....I for one have never put all my eggs in one basket. Preferring to use 2 motor makers wares. First you want to know where & who you will be buying from.

I.E. what does your local launch site vendor carry. That would be first on my list, definitely want to be able to buy from him.

At one time or another I have had AT Gorilla AMW CTI Loki Ellis Mountain in my motor box. Never all at once. AMW & Gorilla & Ellis are now extinct. I have some AT & some CTI. Cover your butt, ya never know what's going to be available at any given time. Few year back AT had a fire and for 2 yrs getting motor from them was tough. Now CTI is becoming scarce since their fire in March. So having different brands is advantageous.
There really isn't that much difference between all of them performance wise. A bit of searching & you will find the perfect motor for your flight from any of them.....[yeah I know there are a couple of "specialty motors out there] with over 500 loads out there to choose from ya'll find something.

Each company has several propellents & you can find similar thrust curves in most sizes from most companies. That is say a 2 grain 54. Want a hard hitting power lifting unit? That would be Blue thunder in AT & white Thunder in CTI.
Need a 3 grain 54 long burn? Both have those also.

I never have been one to say GO brand X it's the best....BS..they all have their finer points.

Another thing to consider. I never have been one to buy a full set of hardware in any size [29-38-54 etc] from anybody.
It's a waste..... buy & fly what ya need for the moment. I always wait to find a sale somewhere for hardware. When you really don't need it...is the best time to buy... you will wait for a good deal.

Large 38 cases will do what small 54 will and so on. Be choosey about buying hardware & ya won't have any gathering dust unused. :wink:

Edit forgot..... now with a couple of spacers a single case can do they duty of 3. I must admit though.....my favorites sizes, like a 2 Grain 54 & 6-grain 38's,. I have 2-3 of them, so I can load & have ready to fly more than one. I'll clean 'em all later, rather than at launch to re-use. Some....just 2 sizes..I have 3 of to use in clusters..
Bottom line, whatever you fly the most...will be the sizes needed. All else is collecting dust. For that once in awhile flight, I'll borrow the case. [ with the given rule....I break it, I buy it.]
As for the short answer to your question, I use AT & CTI of various sizes. But still have some AMW for research use.

 

[DavidMcCann]

Another thing to consider. I never have been one to buy a full set of hardware in any size [29-38-54 etc] from anybody.

I was obsessed with getting spacers and cases to cover everything when I first started in 29 and 38.

I found out very quickly there were only a couple sizes that really interested me, and to this day never have flown a spacer. 3 and 6 grain seem to be the sweet spots for me in AT and CTI loads. Luckily motor hardware sells very fast here, so I've unloaded most of what I don't use.

Going from the start and just getting the few cases you like would let you get say, AT 360, CTI 3G, and a Loki 480, instead of all of Brand X's cases and having 4 of those cases collect dust when you fly the snot out of one of them is a great point Jim....wish I'd of thought of that a few years ago.

 

[TMJ]

Blackjack, David... I've read your posts. There are three clubs in my area. They all launch from different sites. One of them seems to have lost their HP site, and is looking for a new one. That leaves two. One of those remaining clubs launches about two hours south of me, with fairly high altitude waivers. The other club launches about an hour to the northeast of me with "ehh" so,so high waivers. I might entertain both, just for convenience, but for right now? I don't know 'what' direction I'll prefer to drive. That being said... I also don't know what vendors/goods will be available at the launches for the purchase of motors. I'll contact these folks, in good time, but not right now.

I like the Loki thing for numerous reasons. I also like avoiding hazmat fees if I need to order online. That's a definite 'plus', in itself, however. I also can't buy a reloadable "H" size motor casing, from Loki, for a 54mm mount. No adaptors listed, either (perhaps I missed something on their website). I've run some sims, on OpenRocket, for my Frenzy... and actually see that certain "H" motors will truly give me the 'Low/slow' flight that I desire for Level 1 certification, with my Frenzy. I've also done the math, manually, and 'that' works too, however. Even at a +5:1 ratio, It leaves little room for error due to a low apogee! I now think that I understand why some folks kept telling me that the Frenzy is 'truly' a 'level 2 bird'. Low and slow is good for certification insurance, but a wider/higher margin for error would probably be even better insurance for success! This makes me wonder if I just discovered a good excuse to buy another rocket in the 38mm motor class for my L1 cert! :clap: Maybe save the 54mm Frenzy for L2!

 

[DavidMcCann]

The smallest Loki 54 is the 1200. That's well above H. Even if they did, it'd be a haz mat load. The I405 is likely the hardest hitting without Haz Mat.

I'd check out local vendors, or make one big motor purchase a year and eat the Hazmat. Any CTI or AT load that will lift that thing are going o be haz mat if you have to order.


A smaller rocket would be a very good idea for L1. I'm wholly behind that.

 

[TMJ]

The smallest Loki 54 is the 1200. That's well above H. Even if they did, it'd be a haz mat load. The I405 is likely the hardest hitting without Haz Mat.

I'd check out local vendors, or make one big motor purchase a year and eat the Hazmat. Any CTI or AT load that will lift that thing are going o be haz mat if you have to order.


A smaller rocket would be a very good idea for L1. I'm wholly behind that.

"It's amazing what one learns, once one begins to 'truly' learn!"

 

[TMJ]

Madcow 4" Super DX3 w/38mm Motor mount. How'd 'this' be for a good level 1 cert bird?
I'm also open for suggestions as to 'other' possible designs and manufacturers...

 

[AfterBurners]

Madcow 4" Super DX3 w/38mm Motor mount. How'd 'this' be for a good level 1 cert bird?
I'm also open for suggestions as to 'other' possible designs and manufacturers...

I thought the Frenzy with as your Level 1?

 

[SCrocketfan]

Even though options are limited, why not fly a (CTI) I540, I470, or I445, (Loki) I405, or (Aerotech) I500 or I600 in the Frenzy? With a strong I motor you have much more room for error, without having to build another kit. The Super DX3 will do fine on an H (even a G if built light) if you do go with that route-probably best to go with a fairly powerful H though (Loki H144, CTI H225 or similar).

 

[Flyfalcons]

Stick an I in there and skip the dualy deploy for your cert flight. Easy peasy.

 

[TMJ]

Primary fins going on. I made a template to insure the fins go on straight and maintain 120 degrees. I'll install all three primary fins, then use the primaries as the alignment fixtures for the secondary fins.

 

[noffie79]

I'm a huge fan of the CTI I540. The I540 is a 99% I motor, meaning it's almost a J. That motor will give you a good L1 cert flight with over a 10:1 TWR. Then, stick in a J285 (which takes the same case, 5G CTI) and get your L2. Almost identical performance with ~2200" and ~300 mph. Easy L1 and L2 in the same day.

 

[TMJ]

One of my fins is slightly warped. I'm throwing some heat at it and will then backbend it, slightly, and let it cool to correct the warp.

 

[DavidMcCann]

Heat, or moisture, then clamp it between two tiles or boards

 

[TMJ]

"Ah, yes"... "Perfect!" Waiting on my warped fin to cool... ... ... ...;

 

[TMJ]

Heating the fin, on the stovetop, then backbending the fin while cooling didn't work. It produced a 'ripple'. Re-heating the fin and sandwiching it between two thick plates of steel didn't work either. The sandwich removed the ripple, but restored the original warp. Now, I'm trying to backbend it, while heating, using a slightly curved base plate on the gadget you see atop the fin, with toothpicks under the ends of the fin, for the backbend. I'll let 'this' system cool as it sits. If this doesn't work? I'll need to do some head scratching, drink a beer... and start pondering upon the properties of G10!

 

[Flyfalcons]

Wipe it with a damp cloth on both sides and keep it flat while drying, as mentioned earlier. I have repaired warps this way successfully.

 

[TMJ]

Wipe it with a damp cloth on both sides and keep it flat while drying, as mentioned earlier. I have repaired warps this way successfully.

Okie Doke! If this doesn't work, I'll try that. Do I just want to dampen the surface, slightly, or what?

 

[Flyfalcons]

Dampen it but don't soak it.

 

[terryg]

From a thread on straightening warped fins:

Apply a mixture of water and ammonia and use some clamps and shims to do this:
Bend the warped fin the other way about the same distance it was warped beyond center. Let it dry for a few days and it will usually go back to center when done.
Usually holding flat will only take out about half of the warped distance.

 

[TMJ]

Dampen it but don't soak it.

Got it! Will do, many thanks!!

 

[TMJ]

From a thread on straightening warped fins:

Apply a mixture of water and ammonia and use some clamps and shims to do this:
Bend the warped fin the other way about the same distance it was warped beyond center. Let it dry for a few days and it will usually go back to center when done.
Usually holding flat will only take out about half of the warped distance.

Thanks terryg. That's 'kinda' what I tried, initially, only without the ammonia and water. I've done a lot of stream bending, heat bending, and 'yes' the ammonia thing too, however. I've never before tried to form 'plywood'... only solid pieces of hardwood. The ammonia thing makes me a bit nervous. Not sure if the ammonia will play nice with the glue used between the laminations in the plywood. I could very well be wrong, but I think I'll save the ammonia for my static 'plank-on-frame' wooden ship models, just to be safe.

 

[TMJ]

Okay, the warped fin is 'still' fighting me. I wet it, last night, then weighed it down flat. That removed 'some' of the warp, but not all. I've re-wet it, on both sides, and now have it back-bent via two thicknesses of paper under the fore/aft ends of the fin, as shown in the photo. Gonna let this dry for 24 hours and see what I get. Just to make sure that I am not 'splitting hairs' here... What would be an acceptable amount of warpage? I currently have about .030" inches worth of warp, measured at the deepest part of the warp, which is almost dead center, fore/aft, on the fin? It's not much, but easy to see when I look straight down the leading edge of the fin. I certainly don't mind having a bit of 'rifling, as it goes up, but only 'one' fin is warped. That could produce a wobble, or a 'barrell-roll' sort of ascent. ???

 

[TMJ]

I appreciate all of the suggestions for motors on my Frenzy L1 cert flight. I was wanting to keep that cert flight low and slow, but who knows. If I feel confident in my build and find myself happy with my ground testing results...I might very well stuff it with an "I" and "Let 'er Rip!" The only problem is....... I'm 'already' wanting to add another rocket to my toy box! "I'm looking for a good excuse!"