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

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I'm getting a lot of inputs on shock cords, rigging, etc., however. I still have questions. Maybe my drawing will help clear things up for me.
I can see three different methods of rigging. 'A', 'B', and 'C'. I'm preferring 'B', but not real sure. Let me know what experience has taught you guys to be the best system.
Also, I'm still puzzled as to the length of the cords running from booster to the drogue, and the length of the main shock cord. I hear 3-5 times the length of the rocket, 6 times the length, etc. Too long is supposed to be bad, too short 'also' bad. How does one determine what is truly correct for a specific rocket? If I go by some of the 'rules of thumb', heck. That means some of you L3 guys need to be using steel cables a couple hundred feet long, LOL. That's why I am confused. What works best, for you guys in DD?
The drawing is not to scale. For reference only...

View attachment 298019

One thing I will recommend if you go with D is put the drogue closer to the AvBay, as the rocket falls under drogue the main chute section should always stay above the fin section. If the fin section is above the main payload bay it can fall into the deploying chute causing a collapsed chute.
 
What works best, for you guys in DD?

This is what I would recommend for your particular project:

27 ft of 9/16th's tubular nylon for apogee. You will lose a couple feet tying knots on each end. This is often overlooked. Apogee is where most things go wrong, so having a bit more cord will scrub off excess speed of parts seperating.

9/16 TN is wide & soft ...helps with the zipper issue.

Main, use same but 18ft, you can count length of chute risers as part of overall length, so if they are 4ft you have 20-22 ft after knots.

Attach drogue about 3ft below av-bay. Attach main about 3-4 ft from nose cone.

For testing charges:
Place empty motor case with closures into motor mount.
Put charge on apogee side of Bulkplate & just run wire out vent hole, in vent band. No need for altimeters to be inside for this, or main test. You can use any wire you have, to test. I just touch ends to 9v battery to fire.

I have my recovery gear installed. I put front of rocket on a lawn chair with fins on ground, so front is pointing up at 35-45 degree angle. Brace rear/on ground of rocket with a foot so it can't kick back.

The do basically the same for main test. Looking for at least half to 3/4 extension of gear & nc when fired. You do NOT want NC coming to end of cord and snapping back.....too much BP!

To test electronics no need for BP, Just use bare e-matches/starters or mini Xmas lights. Use your shop vac or what ever to pull down pressure and re-lease slowly. They will fire. This way you can get close for this test, no BP...no danger.

All above based on experience, not rules of thumb. Good luck. I would start with 1.75 gr of BP for both apogee & main, then go from there. Why same amount? well should be more volume in fincan, but no shearpins.
Main your dealing with more needed pressure, to cut the pins, even though less volume.

Remember that testing on ground does not account for dynamics of flight, early/late deploy while rocket is moving, wind shear, weather cocking....things that can cause payload or NC not to move as freely as a static test!
 
This is what I would recommend for your particular project:

27 ft of 9/16th's tubular nylon for apogee. You will lose a couple feet tying knots on each end. This is often overlooked. Apogee is where most things go wrong, so having a bit more cord will scrub off excess speed of parts seperating.

9/16 TN is wide & soft ...helps with the zipper issue.

Main, use same but 18ft, you can count length of chute risers as part of overall length, so if they are 4ft you have 20-22 ft after knots.

Attach drogue about 3ft below av-bay. Attach main about 3-4 ft from nose cone.

For testing charges:
Place empty motor case with closures into motor mount.
Put charge on apogee side of Bulkplate & just run wire out vent hole, in vent band. No need for altimeters to be inside for this, or main test. You can use any wire you have, to test. I just touch ends to 9v battery to fire.

I have my recovery gear installed. I put front of rocket on a lawn chair with fins on ground, so front is pointing up at 35-45 degree angle. Brace rear/on ground of rocket with a foot so it can't kick back.

The do basically the same for main test. Looking for at least half to 3/4 extension of gear & nc when fired. You do NOT want NC coming to end of cord and snapping back.....too much BP!

To test electronics no need for BP, Just use bare e-matches/starters or mini Xmas lights. Use your shop vac or what ever to pull down pressure and re-lease slowly. They will fire. This way you can get close for this test, no BP...no danger.

All above based on experience, not rules of thumb. Good luck. I would start with 1.75 gr of BP for both apogee & main, then go from there. Why same amount? well should be more volume in fincan, but no shearpins.
Main your dealing with more needed pressure, to cut the pins, even though less volume.

Remember that testing on ground does not account for dynamics of flight, early/late deploy while rocket is moving, wind shear, weather cocking....things that can cause payload or NC not to move as freely as a static test!

Now 'THIS' is something that I can actually sink my teeth into... maybe even use as a standard by which to punch keys on a calculator for different sized rockets close to the Frenzy size/weight! I can determine many 'things' from the spec's offered here in shock cord material, strength's, length's, etc. Very, very useful data!!!! :)
 
The neat thing about rocketry is that two people can build the same kit side by side, do different things, and they both work just fine.

I fly my DD birds with the drogue about 10-15% of the line down from the AV bay. That way the bundle has some room to move away from the blast. I think that most people, in general, use WAY too much cord, especially for the drogue, and that's just cargo. I size the drogue to ensure that the payload bay/main stays above the booster. Sometimes that takes a flight or two to dial in perfectly, and I reserve the right to change based on winds aloft of the day! I have flown drogueless, but I don't like to. I almost always put the main on the nose cone ring.

I sleeve my TN with either nomex sleeve or kevlar, depending on configuration. All of my harnesses are removable for inspection and replacement as much as possible. Anything that I can't put my hands down gets kevlar for flame resistance.

I haven't set a rocket up like Dave illustrates in his picture (parachute on the end of the cord, and nose cone down the line), but I have one rocket that I think I may change to that configuration because it always seems to tangle somewhat.

One point to you wanting to ground test your charges without any lanyard....I did that once. Once. Shot the nose cone across the yard, over the fence, and out into the park! Luckily it was early Sunday morning and no one else was around. Since then, I always use some sort of limiting lanyard when testing to decide what length of cord to use.

I also use old t-shirts rolled up to the same bulk and size as the parachutes that I plan to use. Tape 'em closed and label them and you'll always have the right reference on hand. Mess it up one time and torch a brand new Fruity Chute and you'll know why some us say test with dummy rolls.
 
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One point to you wanting to ground test your charges without any lanyard....I did that once. Once. Shot the nose cone across the yard, over the fence, and out into the park! Luckily it was early Sunday morning and no one else was around. Since then, I always use some sort of limiting lanyard when testing to decide what length of cord to use.

I also use old t-shirts rolled up to the same bulk and size as the parachutes that I plan to use. Tape 'em closed and label them and you'll always have the right reference on hand. Mess it up one time and torch a brand new Fruity Chute and you'll know why some us say test with dummy rolls.


I'll let the video speak for itself on these two ><.

[youtube]8JjxD48V_e4[/youtube]
 
The neat thing about rocketry is that two people can build the same kit side by side, do different things, and they both work just fine.

I fly my DD birds with the drogue about 10-15% of the line down from the AV bay. That way the bundle has some room to move away from the blast. I think that most people, in general, use WAY too much cord, especially for the drogue, and that's just cargo. I size the drogue to ensure that the payload bay/main stays above the booster. Sometimes that takes a flight or two to dial in perfectly, and I reserve the right to change based on winds aloft of the day! I have flown drogueless, but I don't like to. I almost always put the main on the nose cone ring.

I sleeve my TN with either nomex sleeve or kevlar, depending on configuration. All of my harnesses are removable for inspection and replacement as much as possible. Anything that I can't put my hands down gets kevlar for flame resistance.

I haven't set a rocket up like Dave illustrates in his picture (parachute on the end of the cord, and nose cone down the line), but I have one rocket that I think I may change to that configuration because it always seems to tangle somewhat.

One point to you wanting to ground test your charges without any lanyard....I did that once. Once. Shot the nose cone across the yard, over the fence, and out into the park! Luckily it was early Sunday morning and no one else was around. Since then, I always use some sort of limiting lanyard when testing to decide what length of cord to use.

I also use old t-shirts rolled up to the same bulk and size as the parachutes that I plan to use. Tape 'em closed and label them and you'll always have the right reference on hand. Mess it up one time and torch a brand new Fruity Chute and you'll know why some us say test with dummy rolls.

Nice post, very informative... all points well noted. Never thought about using a dummy-roll for testing. That makes a lot of good sense! You likely just saved me a lot of unnecessary wear/tear on a new chute! As for testing without a lanyard, I see your point and the potential for problems, prior to my getting things properly dialed in, however... does the same warning hold true if there's an irritating, noisy dog, that just won't stop 'yapping' on the other side of the fence? LOL
 
No building has been done since my last build update/photos. Totally burned out from a heavy work load and the Texas heat... but stand by. Advancements are coming soon!
 
On a 4" dia. airframe... what would be a good size to drill my 'vent' holes to prevent premature separation of components? Also, where are the preferred locations, of these holes, in the booster section and in the payload section?
 
if you are planning to use sheer pins then you probably don't need vents. one 1/8" hole per section will suffice, for my comp3 I put in 1 hole in the booster section about halfway between the forward CR and the aft location of the av-bay(which is about 3" below the vent band).
Rex
 
On a 4" dia. airframe... what would be a good size to drill my 'vent' holes to prevent premature separation of components? Also, where are the preferred locations, of these holes, in the booster section and in the payload section?


I would recommend:

drill 1/8in. hole then harden with CA. Sand the outside/inside of airframe to remove rough edges.
Re-drill/clean up hole, by "hand " turning a bit.

Place one vent between top CR and bottom of av-bay coupler. Fincan done
Place other in center of payload tube. Done

As stated 1/8 hardened hole for both, will be fine. If you plan on flying "fast" motors over 5,000 ft. I personally up the size to 5/32's. No... it will not have any adverse effect on charge sizing.

That's how I do it on 4in tubes, assuming approx. 2-3ft of tube length being vented. No I don't use a calculator or formula, just based on flying experience. Others may disagree.
 
Thanks Rex, thanks Jim... "Will do!"
Jim, how'd you know I'd ask about charge sizing with vent holes, had you not said anything? "You're obviously starting to understand how I 'think'." I don't know if that's a good thing, or a 'bad' thing! :lol:
 
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Rex... you once answered a question that I had concerning primer paint for plywood fins. I was afraid of warpage when I asked the question. Should I 'seal' the plywood fins prior to priming, or just go with the primer, alone?
 
Rail buttons...
My aft rail button screws into the aft MM centering ring. Easy to secure, however. What about the forward most rail button? It screws into a through the wall 'blind-nut', of sorts. The screw does not protrude into the internal space of the fin can, for obvious reasons, but how does one secure that screw? When I back the screw off just enough to allow the button to spin, the screw 'also' spins with the button. I can see the screw 'unscrewing' itself during launch and blowing my L1/L2 attempts. Can't re-launch with only 'one' rail button! Will Loctite threadlocker solve this problem and positively secure the screw, or should I use something else. I'd really like to be able to change the button, if need be. Not wanting a permanent system... unless it is highly unlikely that my rail buttons will ever need replacing before I decide to move on to other rockets (highly likely, quickly).
 
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Rail buttons...
My aft rail button screws into the aft MM centering ring. Easy to secure, however. What about the forward most rail button? It screws into a through the wall 'blind-nut', of sorts. The screw does not protrude into the internal space of the fin can, for obvious reasons, but how does one secure that screw? When I back the screw off just enough to allow the button to spin, the screw 'also' spins with the button. I can see the screw 'unscrewing' itself during launch and blowing my L1/L2 attempts. Can't re-launch with only 'one' rail button! Will Loctite threadlocker solve this problem and positively secure the screw, or should I use something else. I'd really like to be able to change the button, if need be. Not wanting a permanent system... unless it is highly unlikely that my rail buttons will ever need replacing before I decide to move on to other rockets (highly likely, quickly).

Loctite will work, but even the "removable" types will make the railbutton permanent if the blind nut is not epoxied in place. If you epoxy the blind nut then the screw can be tightened as normal.
 
are you using a water based primer/paint? if the answer is no then I would just apply primer...well ok, I have been known to apply a coat of spot putty and use an electric sander before the fins are attached, but since most of the spot putty gets removed...prime and sand as needed/wanted until they pass your muster(which can vary depending on the time allotted and when you get sick and tired of the whole sanding routine :)). don't waste your time using any paper higher than 320 grit on primer(one can usually get away with using 240 grit as the color coats will usually fill that size scratches, filler primer can handle covering the results of 220 grit paper).
Rex
 
Loctite for threads... and lacquer based primer, without sealant... "Sounds good to me!" "Thanks Rich, Thanks Rex!"
 
Waiting on a needful 'care-package' to arrive so I can complete the Frenzy build. While waiting, I stumbled upon a great little 'tangent' worth veering off towards...
I just found a really cool 'gadget' that might make me change my mind on someday pursuing level 3. I was thinking that level 2 would be enough to keep me happy, and I'm sure it would, under 'normal' situations, however. When I heard the words "Hello, my name is 'KATE'"... I instantly fell in love! You guys know what I'm talking about! https://www.multitronix.com If this isn't the 'cats' meow, and also a very good reason to go higher, further and faster... well. It's missing a damned good chance! This thing is simply "WAY TOO COOL!"' A true 'Gadgeteers' GOLDMINE!
Have any of you folks ever met KATE, in person? Whatta you think?
 
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Have any of you folks ever met KATE, in person? Whatta you think?

Yes...yes..no....yes

Talking GPS. I've seen it in action several times.
Telemega does Talking also, just not as sexy, but 400.00 Tapped a L-3 flight where it was speaking all the way up & down.

Missleworks is working on that[talking] next after getting caught up with the new release.

2500.00 is out of my range, although it IS worth every penny!

Tracking says package was delivered to locker....
 
2,580.00 seems to be the current price for a complete system, with case included, plus shipping, of course! Yes, it's definitely 'pricey', but 'damn'! Who needs 'Houston' with one of these friggin' things!! LOL
I'll have Vickie check the mail when she gets home. Thanks Jim!
 
Waiting on a needful 'care-package' to arrive so I can complete the Frenzy build. While waiting, I stumbled upon a great little 'tangent' worth veering off towards...
I just found a really cool 'gadget' that might make me change my mind on someday pursuing level 3. I was thinking that level 2 would be enough to keep me happy, and I'm sure it would, under 'normal' situations, however. When I heard the words "Hello, my name is 'KATE'"... I instantly fell in love! You guys know what I'm talking about! https://www.multitronix.com If this isn't the 'cats' meow, and also a very good reason to go higher, further and faster... well. It's missing a damned good chance! This thing is simply "WAY TOO COOL!"' A true 'Gadgeteers' GOLDMINE!
Have any of you folks ever met KATE, in person? Whatta you think?

We have flier who attends our regular launches that owns a KATE unit, the feedback is awesome, expensive but awesome.
 
I've asked many folks about recovery system details and have also received 'many' great answers. I'm truly grateful to everyone who has offered me their advice. It all helps! That being said, there were also certain 'fine' details that kept escaping me and simply led me towards asking more questions. Kinda like getting a recipe for that 'perfect' BBQ rub. All good cooks know to leave an important ingredient, or step out, just because! LOL Not saying that anyone here has intentionally done that... I'm just saying that there is a lot more to good recovery systems/techniques than can be explained via simple answers. Recovery is very important. Without it, "what's the point?" Me being a newbie to HPR, not knowing what 'all' to ask, and also being a bit anxious to get things done and learn as quickly as possible... I decided to pursue a more sophisticated means by which to hopefully learn about the finer details and methods behind proven HPR recovery systems and proper Av-Bay electronics mounting hardware/techniques. "I begged!" :blush: LOL
The below photo shows a very needful 'care package' containing all of the important 'goodies' that I'll need to complete this build, plus a Super DX3 and get them both back safely the first time! "Huge 'THANKS' to ya, Jim!!!" "This is that 'proverbial' "Bird in Hand!" A Missouri "SHOW ME" answer to 'most' all of my recovery questions. Workmanship is also 'great'! You know how to tie some impressively flat/substantial knots! I'll easily learn 'volumes' from what you have sent me! I do have one more question concerning the proper location of the drogue, and the main, on those strings of harness. You might have explained that in your written material, but I've not read it yet. I just got home and the Mrs. sent me a text wanting to know if I'd whip up some of my spicy southern fried chicken. Gotta keep momma happy! I'll read after supper... then get to work on another Av-Bay for the DX3.

Recovery and Av Bay Care Package.jpg
 
while I am sure that you probably know this...a reminder, Take. The. Tape. Off. The. Chute Bundles. Before you stuff them into the rocket during flight prep. also Attach the quick links to shock cords, Chutes, AND the Rocket during flight prep. ballistic recovery usually leaves a mess where your hpr bird used to be.
Rex
 
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I do not see much point in ground testing with different equipment than what will be flown.

I fly both. I ground test with the cheap ones that get culled out of the lot for various reasons (chips in the match head, strange resistance readings, etc).

I've NEVER had any issues with the firewire matches, but they're expensive to ground test with when I have non-flyables at a much cheaper price.

Using both I also know that I always have proven alternatives that I can borrow/buy at the field should I brain fart and leave my charges at home(again).
 
I fly both. I ground test with the cheap ones that get culled out of the lot for various reasons (chips in the match head, strange resistance readings, etc).

I've NEVER had any issues with the firewire matches, but they're expensive to ground test with when I have non-flyables at a much cheaper price.

Using both I also know that I always have proven alternatives that I can borrow/buy at the field should I brain fart and leave my charges at home(again).

That is cool, and not trying to single you out here, but recently I have seen a ton of preventable problems along similar lines. Changing components, formulations, or suppliers, means retest!

Either that or understand that you are flying an untested configuration, which I do all the time, but as a calculated risk. For example, I once changed to weaker shear pins for a flight where deploying main at apogee was totally acceptable.
 
Motor cases have been ordered. I'm starting my propulsion journey with Loki. 38/480 for my level 1 Super DX3 and a 54/1200 for this L2 Frenzy. Don't know where I'll go from there, but 'this' is where I start with motors! :)
 
Motor cases have been ordered. I'm starting my propulsion journey with Loki. 38/480 for my level 1 Super DX3 and a 54/1200 for this L2 Frenzy. Don't know where I'll go from there, but 'this' is where I start with motors! :)

Get an I405; they are amazing.
 
while I am sure that you probably know this...a reminder, Take. The. Tape. Off. The. Chute Bundles. Before you stuff them into the rocket during flight prep. also Attach the quick links to shock cords, Chutes, AND the Rocket during flight prep. ballistic recovery usually leaves a mess where your hpr bird used to be.
Rex

I hear ya, Rex. A lot of new stuff to get a good grasp upon. New pre-flight techniques, equipment, etc.. I hope that I don't miss something, come launch day, and find myself doing new calculations to best match rocket size, weight, peak altitude and descent velocities in order to properly size the 'shovel' that I'll need to recover my rocket(s)! :facepalm:
 
I once was at a LDRS In KS. I was putting my rocket on the pad and the guy next to me started using some bad words. I asked him if I could help you. He said I don't think so I left my motor back at the truck. How did he make it through the RSO table. We both had to laugh after he went back and got his motor.
 
I once was at a LDRS In KS. I was putting my rocket on the pad and the guy next to me started using some bad words. I asked him if I could help you. He said I don't think so I left my motor back at the truck. How did he make it through the RSO table. We both had to laugh after he went back and got his motor.

LOL! I doubt that me, nor anyone else will miss a motor during my cert launch(s), but... only the lord knows what I 'WILL' miss the first few times out of the chute! Hopefully, altimeters cannot accidentally be programmed for 'negative' altitude values! "YIKES!"
 
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