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

[astrojase]

If you are going to use a 'middle' centering ring (good idea with split-fin rockets in general), and once you've got the aft centering ring on, that'll making foaming tough - FWIW... I've never tried to inject foam, but don't imagine it'll be easy or clean.

If you are insane you could even go for an I600.

:headbang:

 

[SCrocketfan]

You're excited to be starting in rocketry. That's good. But don't let the awesome run away from you here.



Nope, it makes for a rocket too heavy to safely fly on an L1 motor. If you don't have 5:1 thrust to weight, It's not going to be allowed to fly. Even at 5:1, wind may give you hell. The challenge on flying this rocket on an L1 motor is to keep it light. Challenges are good, but you can't challenge physics.



I'm in the camp that thinks foam is a terrible idea in any rocket. (its a small camp). In this rocket, it would be better to reduce weight, than add more in the ass end. Foaming the can will add weight in an already strong area...and increase the odds of crumpling the forward section.

No foam, no thru the wall fins, hit the ground going 450 MPH. fincan area was fine, rest.... not so much.

Fully agree on not super overbuilding this (especially considering the cardboard will likely fail before fins/mmt/etc), but I do want to mention I've run an I445 in my dual deploy Frenzy just fine-an H would be possible but I wouldn't recommend it. Before adding the av-bay mine was only ~70 oz and flew great on an I303. The heaviest <J motor build I've flown was a 150oz 5.5" Mini Magg based rocket, but I used an I566, I470, or I540 for all L1 flights to keep a very high thrust:weight ratio.

Serious +1 to building it light though if you want performance on L1 motors. Mine has no internal fillets, two rings that don't contact the fins, wood glue/5 minute epoxy, and absolutely no reinforcement and it did fine on a K360 a while back.

BTW, bit of a sad picture, but a good proof of the durability of cardboard/plywood!

 

[o1d_dude]

Bear in mind that SCRocketfan is a fearless practitioner of the Wildman Creed...:y:

That being said, he does quite well with his rockets.

 

[Banzai88]

Bear in mind that SCRocketfan is a fearless practitioner of the Wildman Creed...:y:

That being said, he does quite well with his rockets.

OK, I'll bite. What's the "Wildman Creed"?

 

[blackjack2564]

OK, I'll bite. What's the "Wildman Creed"?

Written by yours truly..LOL

The reference is to commandment #4 failure to comply results in "Mildman" status.

 

[SCrocketfan]

Bear in mind that SCRocketfan is a fearless practitioner of the Wildman Creed...:y:

That being said, he does quite well with his rockets.

Why thank you Kit and CJ! Admittedly, neither of you saw the result of me attempting part #4 of the creed at LDRS with an L640...

As for the Frenzy, I pretty much stuffed the largest motor that fits in it back in December with that K360-a 4G or 5G motor would fit, but that's really pushing the limits of cardboard and anything more than a 3G makes fitting my tracker difficult. I drop the tracker (eggfinder) into the motor tube as there isn't enough space between the av-bay and top CR. I actually had to rest the tracker in the motor casing for the K360 flight (4 grain case with spacer), and surprisingly it held lock the whole flight! Perfect flight to 5279' (or 5289', depending on altimeters) using dual deploy landing ~4000' away (it was windy that day).

 

[Exactimator]

TMJ,

For whatever it's worth, I've had four 4" Madcow cardboard kits. I built them all standard with kit parts per the instructions using 5 minute epoxy. Some are motor eject, some are DD. I have fiberglass kits too and they have their place. I like the cardboard rockets because they're are easy to build, light, and durable enough to last a while.

There are no internal fillets or foam or fiberglassing or even welded eyebolts. Other than one meeting an early end in an unfortunate CATO, the rest have launched and recovered many times. I've had to make a couple minor repairs after landings on hard playa surfaces (similar to concrete). But all in all, the fleet has held up well.

The lighter the build, the wider variety of motors can be used. The smaller the impulse the lower the cost per launch. Build light and you won't be tied to $50 motors every time you want to launch. If you figure saving $20 per launch, after a handful of launches you'll save enough to buy a replacement kit.

If you build too heavy, you'll end up limiting yourself to high initial impulse I motors only like White Thunders or VMAX. If that's how you like to fly, by all means have at it. there are certainly enough people here that build their rockets like armored tanks. But for me it would be a shame to take a rocket that could launch on high H's and up and build it so heavy it can only fly on a few I motors.

 

[Bat-mite]

Just wanted to point out that an hour or two of ground testing ejection charges eliminates the risk of over-energetic charges that could bend your eye bolt.

When you test, make sure the rocket is loaded in ready-to-fly condition. Start with the minimum. Increase in small amounts until you get a charge that pulls out your chute but doesn't stress the harness. Think "harness" and not "shock cord." There really shouldn't ever be "shock" on a harness.

 

[DavidMcCann]

Fully agree on not super overbuilding this (especially considering the cardboard will likely fail before fins/mmt/etc), but I do want to mention I've run an I445 in my dual deploy Frenzy just fine-an H would be possible but I wouldn't recommend it.

Yea, I don't think he'll wind up out of the L1 range, but every ounce removes more and more motor options.
Someone suggested an I600R. Fantastic motor. 4", 6 pounds, got about 2800' This and the J500G make me want to get another 38/720.

 

[TMJ]

The rocket is weighting slightly above 2kg so with an I284 you get an thrust to weight ratio of over 10, 20 if you consider the thrust peak. If you are insane you could even go for an I600. So physics is not against a Level 1 Motor.

Ich bin damit einverstanden , dass der Schub zu Gewicht gut sein wird . Ich habe Probleme mit Menschen, mich zu viele persönliche Meinungen "und nicht als harte wissenschaftliche Fakten anbietet.

 

[TMJ]

Just wanted to point out that an hour or two of ground testing ejection charges eliminates the risk of over-energetic charges that could bend your eye bolt.

When you test, make sure the rocket is loaded in ready-to-fly condition. Start with the minimum. Increase in small amounts until you get a charge that pulls out your chute but doesn't stress the harness. Think "harness" and not "shock cord." There really shouldn't ever be "shock" on a harness.

I fully intend to ground test my charges, as well as my altimeters via a shop vac to simulate altitude. Won't know how high the shop vac takes my altimeters, but I suppose if I seal the vac hose tight enough to the static ports it will go high enough in a simulated situation.

 

[TMJ]

TMJ,

For whatever it's worth, I've had four 4" Madcow cardboard kits. I built them all standard with kit parts per the instructions using 5 minute epoxy. Some are motor eject, some are DD. I have fiberglass kits too and they have their place. I like the cardboard rockets because they're are easy to build, light, and durable enough to last a while.

There are no internal fillets or foam or fiberglassing or even welded eyebolts. Other than one meeting an early end in an unfortunate CATO, the rest have launched and recovered many times. I've had to make a couple minor repairs after landings on hard playa surfaces (similar to concrete). But all in all, the fleet has held up well.

The lighter the build, the wider variety of motors can be used. The smaller the impulse the lower the cost per launch. Build light and you won't be tied to $50 motors every time you want to launch. If you figure saving $20 per launch, after a handful of launches you'll save enough to buy a replacement kit.

If you build too heavy, you'll end up limiting yourself to high initial impulse I motors only like White Thunders or VMAX. If that's how you like to fly, by all means have at it. there are certainly enough people here that build their rockets like armored tanks. But for me it would be a shame to take a rocket that could launch on high H's and up and build it so heavy it can only fly on a few I motors.

Thank you! Yes, I am aware of the many pitfalls of weighty building, however. Extra weight could work to my advantage on 'this' build. My goal is to go low and slow for a successful level one project, and 'ditto' for level two, when that time comes. I'm not concerned about weight so long as the rocket will leave the rail at a stable airspeed and reach a minimum safe altitude for successful dual deployment. I'll save the fast, high stuff for later!

 

[Steve Shannon]

Ich bin damit einverstanden , dass der Schub zu Gewicht gut sein wird . Ich habe Probleme mit Menschen, mich zu viele persönliche Meinungen "und nicht als harte wissenschaftliche Fakten anbietet.

Ich auch!

Build it the way you want. It's meant to be an educational, interesting, enjoyable process. You'll learn what works for you and hopefully you'll make many more rockets in the years to come. Don't let it get you down.

 

[TMJ]

Ich auch!

Build it the way you want. It's meant to be an educational, interesting, enjoyable process. You'll learn what works for you and hopefully you'll make many more rockets in the years to come. Don't let it get you down.

Not to worry, "It's all good!" :wink:

 

[TMJ]

MM ready to be shoved up the 'arse' of my Frenzy, however. There's something 'obviously' missing. A 'Y'-Harness! Before I harness this thing, I need to know if some good ol' fashioned fishing knots will suffice... or should I sew loops onto the ends of my harness and use 'quick-links'? I'll be using 3/8" Kevlar tubing for the harness. I've never tried to tie a knot in this stuff, before. This will be a first for me. Time for more opinions, suggestions, photo's, etc...

 

[AfterBurners]

View attachment 296109

MM ready to be shoved up the 'arse' of my Frenzy, however. There's something 'obviously' missing. A 'Y'-Harness! Before I harness this thing, I need to know if some good ol' fashioned fishing knots will suffice... or should I sew loops onto the ends of my harness and use 'quick-links'? I'll be using 3/8" Kevlar tubing for the harness. I've never tried to tie a knot in this stuff, before. This will be a first for me. Time for more opinions, suggestions, photo's, etc...

Use 1500lb 1/4" quick links. You could probably get loops sewn on the shock cord / harness, not sure who would do that off hand. I'm sure someone here may know?

 

[DavidMcCann]

I tie a quick knot in the end of my lines, and attach with a quick link. not pretty, but simple.

 

[Buckeye]

Should any of you folks find flaws in my way of thinking, my methods, etc., PLEASE chime in and give me your 'two cents worth'! I welcome ALL advice and suggestions!

Ich bin damit einverstanden , dass der Schub zu Gewicht gut sein wird . Ich habe Probleme mit Menschen, mich zu viele persönliche Meinungen "und nicht als harte wissenschaftliche Fakten anbietet.

Funny, you ask for ALL advice, then you complain about receiving it. Many of the "opinions" you don't like come from experience.

I didn't even stay at a Holiday Inn Express, I just used Google translate.

 

[AfterBurners]

Funny, you ask for ALL advice, then you complain about receiving it. Many of the "opinions" you don't like come from experience.

I didn't even stay at a Holiday Inn Express, I just used Google translate.

plus 1

 

[TMJ]

I tie a quick knot in the end of my lines, and attach with a quick link. not pretty, but simple.

Thanks, David... "Will Do!"

 

[TMJ]

plus 1

Sorry guys. Don't mean to offend anyone, however. "I'm not looking for 'opinions' as to what people think I'm qualified, able, or educated enough to do. I'm looking for advice as to how to 'get it done'!" Many thanks to those who are actually being helpful. As for the 'rest'... "Let's please stop the negative "nay-saying", NOW!.. It won't do you any good, anyway. I'll have a very successful build despite your desires...
Thank you!

 

[noffie79]

Funny, you ask for ALL advice, then you complain about receiving it. Many of the "opinions" you don't like come from experience.

I didn't even stay at a Holiday Inn Express, I just used Google translate.

Yeah, I stopped offering any advice once I realized he's not going to take it. If he wants to turn a 6 pound rocket into a 10 pound rocket just so it's a "low and slow" cert, instead of simply using a different motor, that's his choice. A good RSO won't let a cert flight go with a 3:1 TTW ratio anyway.

 

[DavidMcCann]

Sorry guys. Don't mean to offend anyone, however. "I'm not looking for 'opinions' as to what people think I'm qualified, able, or educated enough to do. I'm looking for advise as to how to 'get it done'!" Let's please stop this, now...

I don't think any of us has been really happy with the way we built our own L1 birds.... If anyone is, I haven't met them.

I don't think any of this build is going into any kind of danger zone.... just little things here and there that will annoy you in a year.... Which, we all do, and still do. I've rebuilt something like 4 or 5 rockets exactly the same, but with bigger motor mounts on try 2.... And i still build with smaller mounts on new builds. Some people just have styles and ways of doing things.


I think people here at great at helpful advice... But at times over-act when it's ignored. Some lessons can only be taught by experience, and those experiences will shape each person's own journey in rocketry. The only goal we all share is safety.... other than that, we all build to different ends and purposes. My goal recently has been to share my experiences, and not act all crazy when others disagree with me. It's helping lower my BP some

 

[TMJ]

I don't think any of us has been really happy with the way we built our own L1 birds.... If anyone is, I haven't met them.

I don't think any of this build is going into any kind of danger zone.... just little things here and there that will annoy you in a year.... Which, we all do, and still do. I've rebuilt something like 4 or 5 rockets exactly the same, but with bigger motor mounts on try 2.... And i still build with smaller mounts on new builds. Some people just have styles and ways of doing things.


I think people here at great at helpful advice... But at times over-act when it's ignored. Some lessons can only be taught by experience, and those experiences will shape each person's own journey in rocketry. The only goal we all share is safety.... other than that, we all build to different ends and purposes. My goal recently has been to share my experiences, and not act all crazy when others disagree with me. It's helping lower my BP some

:smile: Words of wisdom...

 

[nmartin]

Got paint on this past weekend. Pretty much stock. Used rocketpoxy. Dual deploy with dual altimeter systems. My wife likes purple. ACE hardware spray paint. Good stuff. Found testing this week. Launch Saturday if July I hope.

 

[AfterBurners]

I don't think any of us has been really happy with the way we built our own L1 birds.... If anyone is, I haven't met them.

I don't think any of this build is going into any kind of danger zone.... just little things here and there that will annoy you in a year.... Which, we all do, and still do. I've rebuilt something like 4 or 5 rockets exactly the same, but with bigger motor mounts on try 2.... And i still build with smaller mounts on new builds. Some people just have styles and ways of doing things.


I think people here at great at helpful advice... But at times over-act when it's ignored. Some lessons can only be taught by experience, and those experiences will shape each person's own journey in rocketry. The only goal we all share is safety.... other than that, we all build to different ends and purposes. My goal recently has been to share my experiences, and not act all crazy when others disagree with me. It's helping lower my BP some

But David I was happy with the way I built my L1 bird, so now you can say you met someone. I built a stock SUMO, put on a custom paint job and the very first flight was my L1 on an H250G-10 in fact I drag raced my friend with his G-FORCE who also was going for his L1. Every build I do I don't do it the same way twice. If I built one rocket one way, I try to improve on the next by making it lighter or maybe airfoil the fins you know whatever I feel I can do to increase performance. Buts that's just me. The OP isn't concerned with performance and his whole goal is low and slow. So all of us should let it go at that.

My rule of thumb is this. If I'm using cardboard and wood, it's a wood glue build. Other combinations such as wood and fiberglass, all fiberglass, plastic and cardboard I use epoxy and yes I will use fillets, but in proper portion to the rocket. I usually think through exactly what I am going and then execute it. I always try to figure out where the issues may be. About the only thing I replace on most kits is the shock cord especially if it involves knotting two unlike materials such as nylon and Kevlar. I agree with a lot of guys about going larger on the motor mount this way it opens up more options and you can fly smaller if the wallet is thin one month.

You're right everyone has there way of doing things....the OP is asking for advice on what to do, but when someone offers it he does the opposite, so again why ask or what I should be saying don't offer any advice for the OP unless it's pertaining to low and slow? It seems he knows what he is doing and continues with his same method so I just figure I just sit back and watch, because I have nothing insightful to offer Keep up the good work

 

[SCrocketfan]

Yea, I don't think he'll wind up out of the L1 range, but every ounce removes more and more motor options.
Someone suggested an I600R. Fantastic motor. 4", 6 pounds, got about 2800' This and the J500G make me want to get another 38/720.

Pretty sure I could pick up a 720 case and be happy flying only 38mm 720 and 5G loads

I don't think any of us has been really happy with the way we built our own L1 birds.... If anyone is, I haven't met them.

I don't think any of this build is going into any kind of danger zone.... just little things here and there that will annoy you in a year.... Which, we all do, and still do. I've rebuilt something like 4 or 5 rockets exactly the same, but with bigger motor mounts on try 2.... And i still build with smaller mounts on new builds. Some people just have styles and ways of doing things.


I think people here at great at helpful advice... But at times over-act when it's ignored. Some lessons can only be taught by experience, and those experiences will shape each person's own journey in rocketry. The only goal we all share is safety.... other than that, we all build to different ends and purposes. My goal recently has been to share my experiences, and not act all crazy when others disagree with me. It's helping lower my BP some

+1
I was happy with my L1 and still like flying it, but there's a lot I would change building another Mini Magg (54mm, nose cone avionics, different recovery), which I probably will at some point :dark:

Thank you! Yes, I am aware of the many pitfalls of weighty building, however. Extra weight could work to my advantage on 'this' build. My goal is to go low and slow for a successful level one project, and 'ditto' for level two, when that time comes. I'm not concerned about weight so long as the rocket will leave the rail at a stable airspeed and reach a minimum safe altitude for successful dual deployment. I'll save the fast, high stuff for later!

If you don't mind the limited L1 motor selection and pick a motor that will provide enough velocity off the pad like the I540 or I600, then go for it!

 

[Steve Shannon]

I don't think any of us has been really happy with the way we built our own L1 birds.... If anyone is, I haven't met them.

I don't think any of this build is going into any kind of danger zone.... just little things here and there that will annoy you in a year.... Which, we all do, and still do. I've rebuilt something like 4 or 5 rockets exactly the same, but with bigger motor mounts on try 2.... And i still build with smaller mounts on new builds. Some people just have styles and ways of doing things.


I think people here at great at helpful advice... But at times over-act when it's ignored. Some lessons can only be taught by experience, and those experiences will shape each person's own journey in rocketry. The only goal we all share is safety.... other than that, we all build to different ends and purposes. My goal recently has been to share my experiences, and not act all crazy when others disagree with me. It's helping lower my BP some

Well said.


[emoji1010] Steve Shannon [emoji1010]

 

[Buckeye]

The rocket is weighting slightly above 2kg ....

Not likely. My flight ready, Dual Deploy Frenzy with paint and minimal hardware and reinforcement weighs in at 2800 grams. The OP plans on adding the following above and beyond:

• Redundant altimeter system ~175g
• Foam ~125g (I calculated this in my build. Not sure why people think foam is heavy. It's mostly air. But, I digress.)
• Probably a 38mm motor adapter for L1 motor ~ 75g
• Extra ubolts, quicklinks, epoxy ~ 125g

So, this rocket is now up 3.3 kg, pretty easily. Let's sim this in Thrustcurve. Let's also play it safe and assume 10 mph wind. Using the guideline that minimum speed off the rail should be greater than 4X the wind gives a required speed of 60 ft/s. Here's a sampling of Aerotech reloads through I-impulse class. The result pretty much rules out any H motor, except for Warp 9 loads that barely get off the ground. This leaves a handful of I motors for the L1 attempt.

 

[TMJ]

Not likely. My flight ready, Dual Deploy Frenzy with paint and minimal hardware and reinforcement weighs in at 2800 grams. The OP plans on adding the following above and beyond:

• Redundant altimeter system ~175g
• Foam ~125g (I calculated this in my build. Not sure why people think foam is heavy. It's mostly air. But, I digress.)
• Probably a 38mm motor adapter for L1 motor ~ 75g
• Extra ubolts, quicklinks, epoxy ~ 125g

So, this rocket is now up 3.3 kg, pretty easily. Let's sim this in Thrustcurve. Let's also play it safe and assume 10 mph wind. Using the guideline that minimum speed off the rail should be greater than 4X the wind gives a required speed of 60 ft/s. Here's a sampling of Aerotech reloads through I-impulse class. The result pretty much rules out any H motor, except for Warp 9 loads that barely get off the ground. This leaves a handful of I motors for the L1 attempt.

View attachment 296172

'That's' the sort of advice/info that I am after! "Thanks, Buckeye!"