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

not a bad idea... toasty rear-ends are no fun

Nothing much to report, today. I've snapped the tag ends off of my pins and getting ready to squirt some Titebond III around the exposed ends. Tomorrow, I'll break out the ol' sanding block and some thin CA resin to start filling and finishing the surface, where the pins are, to a smooth paint ready surface.

Getting 'real close' to winding things down and completing the booster section. I've created a 'punch-list' for the remaining operations to be done, in the correct order of which they need to be accomplished to insure that I don't get ahead of myself and paint my way into one of those 'proverbial corners', per se. Been putting in way too many hours at work, putting out fires created by our illustrious engineers. My mind is pretty much fried by the time I get home. A 'punch-list' is now mandatory... a redundant 'back-up system' to aid me in the event that my primary brain fails... :bangpan:

Can/Booster 'punch list' completed... laying down the external fin fillets. No, this isn't a 'hatchet' job. "It just looks that way!"

In the "Hopper", up next... Madcow Super DX3. Nice looking rocket, however. The fins are tabbed only at the lower 30% of their length. That's fine, I'm sure... but you folks have probably come to know my methods well enough to realise that 'that' won't set with me too well. I'll need to more securely 'anchor' the forward most part of those fins to insure they indeed stay put, needed or not! I already know how to go about doing that without tabs to pin through. It will be a different technique than what I've done with my Frenzy. The details will be reserved for a new thread, once I get started on the DX3 build. :eyeroll:

I know you'll come up with something cool for the fins, but to share: I built a 4" cardboard rocket and Surface mounted the fins...with wood glue....poorly.... many flights, and even had a chute float away (opps) and it tomahawked a fin into the ground. All fins still on

DavidMcCann said:

I know you'll come up with something cool for the fins, but to share: I built a 4" cardboard rocket and Surface mounted the fins...with wood glue....poorly.... many flights, and even had a chute float away (opps) and it tomahawked a fin into the ground. All fins still on

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Thanks, David. That's very nice to know info, indeed! I'm paying attention, but also a bit leary of certain things in making this giant leap into heavier birds, higher thrust and HPR in general. It's the 'unknown' that concerns me, right now. After I log a few launches, via a few different rocket designs, with different motors... I'll probably lighten up on my curious ways due to first hand experience. Maybe 'not'! Until I've been there, done that and have hands on experience... I'll build 'em as though I, myself, were going to fly in them. LOL :wink:

You should really try building at least one kit according to the instructions provided rather than re-inventing the wheel and calling it "fire". Just saying.

o1d_dude said:

You should really try building at least one kit according to the instructions provided rather than re-inventing the wheel and calling it "fire". Just saying.

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No can do. I've spent my life in R&D aerospace related work and have become 'tainted' with the results of such. Heck, I can't even follow the given instructions on a box of 'Hamburger Helper' anymore! :lol:

TMJ said:

No can do. I've spent my life in R&D aerospace related work and have become 'tainted' with the results of such. Heck, I can't even follow the given instructions on a box of 'Hamburger Helper' anymore! :lol:

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So why do you keep asking for people's input, and then not following any advice given? Thousands of people here have built these kits according to instructions with nary a problem. Just sayin'...

noffie79 said:

So why do you keep asking for people's input, and then not following any advice given? Thousands of people here have built these kits according to instructions with nary a problem. Just sayin'...

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There's a big difference between 'REAL' metal missiles and simple cardboard rockets. What don't you understand about this? Please explain!

"Here we go, AGAIN!"

Lol, so, you send me threatening private messages now, just because I point out the same fact that others here have pointed out? I asked a simple question and made a simple statement. Telling me that I can't comment on "your" threads is childish. Now you really don't want to know what I think of you...

I never once attacked you. And now you've resorted to name calling. Shame on you

noffie79 said:

Lol, so, you send me threatening private messages now, just because I point out the same fact that others here have pointed out? I asked a simple question and made a simple statement. Telling me that I can't comment on "your" threads is childish. Now you really don't want to know what I think of you...

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I never threatened you. I just asked you to stop posting on my thread.

noffie79 said:

I never once attacked you. And now you've resorted to name calling. Shame on you View attachment 297553

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Yes, you are acting like an asshole! I'm just building a rocket!!!!

Despite the recent 'derailment' of this thread (my apologies, folks),... the build continues. Fillets are still being laid and currently curing. I'll start on the altimeter/ebay this weekend.

This is the Madcow Removable Altimeter Bay Upgrade. Before I glue the outer spacer ring into place, I'd like to know why it is supposed to be offset and not 'centered' on the tube?

because you will fix the top end to the payload with removable rivets. I assume this will be the short end of the exposed coupler.

This allows for a shorter bay length and still have enough to ensure an adequate amount to fit into the booster, which typically being a friction fit, should be longer.

Makes sense. I understand. Thanks!

You want at LEAST one caliper of coupler in the part of rocket it slides out of during deploy. Your airframe is 4in. so you need 4in or more in the fincan. Upper part is semi-permanently attached to payload, you can get away with less.

Now the reason. During flight the payload can act like a "lever" during moments of inertia, such as wind gust, wind shear, velocity at Max-Q encountering shear angles. etc This causes the payload to "lever" against the fincan via the coupler. You need the 1 caliper [4in in this case] to spread those stresses out, equally around the fincan through the wall. Any less may cause the fincan to "shear" off due to stress involved. Basically having 1 caliper going into fincan will prevent "wobble" from fit, which also exacerbates above problems. The upper section be held in position fixed is also above the fins which provide the correcting force to rocket and act on the fincan. [upper section is short side of your"lever"]

My caveman version of events. I'm sure others more versed in mathematics & formula's have a better, detailed explanation.

I like to compare it to how thickness of nut, relates to threaded rod diameter. 1/4 threaded rod, needs a nut 1/4 thick for maximum rated strength. Hoping I'm saying that correctly, but I'm sure you get the gist.

You said it correctly, Jim! Good explanation of why the lower section of the e-bay needs to be at least the body tube diameter. I'll be using shear pins up top.
I 'finally' got around to examining the RRC3's (and also read the instructions, LOL). Taking your advice, I drilled three 3/16" dia holes for porting. I also noticed that your instructions say 3/16" for 4"X12" bays. My e-bay has only 7.5" of internal length between the bulkhead plates. Is 3/16" still okay with this shorter length? I can fill them in and use smaller holes if need be.
I cheated on laying out the porting holes. I shoved the e-bay up the rear of my unstarted DX3 and used the fin slots to equally space out the ports. I 'knew' that DX3 would come in handy for 'something'! :wink:

TMJ said:

You said it correctly, Jim! Good explanation of why the lower section of the e-bay needs to be at least the body tube diameter. I'll be using shear pins up top.
I 'finally' got around to examining the RRC3's (and also read the instructions, LOL). Taking your advice, I drilled three 3/16" dia holes for porting. I also noticed that your instructions say 3/16" for 4"X12" bays. My e-bay has only 7.5" of internal length between the bulkhead plates. Is 3/16" still okay with this shorter length? I can fill them in and use smaller holes if need be.
I cheated on laying out the porting holes. I shoved the e-bay up the rear of my unstarted DX3 and used the fin slots to equally space out the ports. I 'knew' that DX3 would come in handy for 'something'! :wink:

View attachment 297593

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To big is better than not big enough...

TMJ said:

. Is 3/16" still okay with this shorter length? I can fill them in and use smaller holes if need be.
I cheated on laying out the porting holes. I shoved the e-bay up the rear of my unstarted DX3 and used the fin slots to equally space out the ports. I 'knew' that DX3 would come in handy for 'something'! :wink:

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Yes you'll be fine. As I mentioned in the PM, when these sizes were recommended in the manual, it took into consideration a variety of lengths & was approved by Jim Amos.

Might I suggest:
Coat the outside of your coupler with a lightly thinned layer of epoxy. It will soak in & harden the exterior, also eliminating the "fuzzies" that build up after several flights.
You will notice a marked difference in how much better it slips in/out after a light sanding. While at it, do same to BP's

Yes, that little "tip" of using fincan slots to mark for 3 even points of reference is one of my favorites first tip I put in instructions.

Just a comment having no particular bearing on anything......... As time goes on and experience is gained, most find eliminating as much as possible, simplifying to the max, saving weight where ever possible....is the mantra of performance and successful flight.
That being said, most of us starting out, go the opposite direction, till reality sets in....... "less is Mo' betta" LOL

blackjack2564 said:

Yes you'll be fine. As I mentioned in the PM, when these sizes were recommended in the manual, it took into consideration a variety of lengths & was approved by Jim Amos.

Might I suggest:
Coat the outside of your coupler with a lightly thinned layer of epoxy. It will soak in & harden the exterior, also eliminating the "fuzzies" that build up after several flights.
You will notice a marked difference in how much better it slips in/out after a light sanding. While at it, do same to BP's

Yes, that little "tip" of using fincan slots to mark for 3 even points of reference is one of my favorites first tip I put in instructions.

Just a comment having no particular bearing on anything......... As time goes on and experience is gained, most find eliminating as much as possible, simplifying to the max, saving weight where ever possible....is the mantra of performance and successful flight.
That being said, most of us starting out, go the opposite direction, till reality sets in....... "less is Mo' betta" LOL

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I was thinking about coating the exterior of the e-bay tube with thin CA, (just like I've done to the ends of the airframe tubes and the motor mount) and coating the plywood end caps of the e-bay with a thin layer of epoxy simply to make for easy cleaning via the black powder residue from deployment charges. Would 'this' also be a good way to do it... or do you think epoxy, everywhere, would be the better choice for reasons that I am currently unaware of? I'm open to your input/suggestions here.

"Most of us starting out, go the opposite direction, till reality sets in....... "less is Mo' betta" LOL
"Been there, 'STILL' there... 'doing' that!" I imagine that after my first HP launch I'll be more 'tuned-in' to the realities involved. As for now, it's the 'unknown' that I fear 2'd most. What I fear the most is failure!

Thanks, Jim!

E-bay power switches.
I purchased some rotary switches, from Missile Works, back when I bought the altimeters. I've since read of, and heard of various other methods for turning the power on. Someone here, on the forum, even mentioned simply twisting the wires together. I don't remember who that was, but I must say it is a beautifully simple and near foolproof idea!
How's about you folks telling me what different methods you use, and why? I'll sort through the advice and go from there...

I've done the twist the wires together and tape them to the side of the rocket. It's not elegant, but it works. Fishing for switches sucks. Externally mounted switches are nice.

DavidMcCann said:

I've done the twist the wires together and tape them to the side of the rocket. It's not elegant, but it works. Fishing for switches sucks. Externally mounted switches are nice.

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Maybe it was 'you', David, who mentioned the twisting thing! The rotary switches I have are indeed externally accessed. You have to use a screwdriver, push in hard and twist, then they pop back out and lock into position. I don't think that they could possibly switch themselves off, or fail, however. I 'have' read about failures in rotary switches. Maybe they were different switches that simply do not lock into place. Don't know for sure.

I like these in 4" and up rockets. These photos are in a 3" and it gets tight inside. basically blocks off half the board on one side. I inset one pair of them in the vent band, decided it was wasted effort and just set the other pair outside.


Twist and tape is easy....if a bit ugly. vent band is black here, that's not all tape- Oh, and don't tape the wires to the booster....umm...yea.




This is a screw switch.... I like them, but finding them through a vent hole can be infuriating some days. Someone invented a funnel guide for them, but I can't seem to find the link at the moment.

David, your rotary switches look exactly like mine! Only exception being in that the graphic below the 110/220 has no paint, on mine! "I just saved some weight!" LOL (just kidding).
Here's a curious question. I'm surely splitting hairs, here, but need to ask, just the same. These switches mount with a profile 'above' the surface of the airframe. They are in the slipstream of airflow running down the body of the rocket. That creates drag, in the area of the switches. The rail buttons 'also' create aerodynamic drag. When assembling the rocket should I locate the switches on the 'opposite' side of the rocket than where the rail buttons are located? Equal/opposite forces. Would this lead to a straighter trip up, or do things happen so fast that the rocket doesn't really care about unequal parasitic drag forces?