Ultimate Wildman Level Three Certification Build

It is likely either metric or imperial. Not many other choices. You can measure the thread size (diameter and pitch) to determine if metric or imperial. There might just be a little dag on the inside of the holes preventing the Allen key from going in. Sometimes a slight tap from a hammer helps.

MAC performance Has some very cool push button switches I'll be using on my next build



Or Aerocon switches they are big, but very nice
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I attached the aft centering ring with the appropriate t-nuts for the thrustplate and after that hardened I went ahead and assembled everything.







Now I only have the recovery system and paint left! I should have everything but paint coming in the mail over the next two weeks.

I saw this rocket at Bayboro today... REALLY pretty build.

blackbrandt said:

I saw this rocket at Bayboro today... REALLY pretty build.

Click to expand...

Thanks Congrats on the L2!

A couple little updates on the build:

I received harnesses from Tim early this week, 50ft for the drogue and 35 for the main, both 7/16 tubular Kevlar.



I also got both the main and drogue parachutes in the mail, but I had those shipped home (currently at university) for ejection testing over spring break, so no pics yet... 20" skyangle and a 168" spherachute.

I also decided on screw switches, which I will line up with the vent holes in the switchband.



All that's left to do is shear pins and pressure relief holes, then paint!

Speaking of, I have heard that there are some mathematical methods for choosing the number of shear pins and their size. Can anyone enlighten me? I was simply thinking 4, 4-40 nylon screws for the main and three for the drogue.

Also, how would I properly size relief holes?

Oh, and this rocket's first flight will be on one of Alan Whitmore's research Ls March 25th in Bayboro. REALLY excited for that flight!

Is that a MW screw switch, it looks big?

""""Speaking of, I have heard that there are some mathematical methods for choosing the number of shear pins and their size. Can anyone enlighten me? I was simply thinking 4, 4-40 nylon screws for the main and three for the drogue."""""

I have several 6in. glass rockets, one of which is the Ultimate Wildman. I use 3 [4-40] pins for NC & none on drogue side. Vent holes in with band for UW are 1/4 in. that bay is huge.......20 inch long .

""""Also, how would I properly size relief holes?""""

above .....1/4in holes in vent band...

blackjack2564 said:

Speaking of, I have heard that there are some mathematical methods for choosing the number of shear pins and their size. Can anyone enlighten me? I was simply thinking 4, 4-40 nylon screws for the main and three for the drogue.

I have several 6in. glass rockets, one of which is the Ultimate Wildman. I use 3 [4-40] pins for NC & none on drogue side. Vent holes in with band for UW are 1/4 in. that bay is huge.......20 inch long .

Also, how would I properly size relief holes?

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OK, BJ I think a rogue question, but I'll bite...

Weight of held section (say NC) times expected Gees (or unexpected during that phase of flight profile) must be less than or equal to by # of pins times pin shear force.

Not my question for some reason the quotes feature malfunction functioned...............although I'm sure your answer is much appreciated by most!

I was replying to questions from post 95


I figured mine out for the N-5800 drag race years ago, previously it was just based on ''it works''. Just so happened for mine...stock parts, no nose weight....3 was the correct number.

I have a nice snug fit, so I suppose if one adds nose weight & fit is loosie goodie, I would make it 4.

blackjack2564 said:

""""Speaking of, I have heard that there are some mathematical methods for choosing the number of shear pins and their size. Can anyone enlighten me? I was simply thinking 4, 4-40 nylon screws for the main and three for the drogue."""""

I have several 6in. glass rockets, one of which is the Ultimate Wildman. I use 3 [4-40] pins for NC & none on drogue side. Vent holes in with band for UW are 1/4 in. that bay is huge.......20 inch long .

""""Also, how would I properly size relief holes?""""

above .....1/4in holes in vent band...

Click to expand...

The fit of the coupler on the aft section is a little loose and I would like a bit of insurance against drag separation, so I may do two 4-40 or three 2-56 shear pins on the drogue and three or four 4-40 pins on the main per your experience.

The relief holes I am asking about would be in the parachute bays to compensate for pressure build up during high altitude flights (N5800 to ~25k eventually...) so that I don't have any premature separation. I assume you are referring to altimeter bay sampling holes, which I've drilled at 1/4".

Fearoflightning said:

The relief holes I am asking about would be in the parachute bays to compensate for pressure build up during high altitude flights (N5800 to ~25k eventually...) so that I don't have any premature separation. I assume you are referring to altimeter bay sampling holes, which I've drilled at 1/4".

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Payload has 2 [1/8] holes. One on each side [180] six inches from nose cone shoulder& six inches from edge of av-bay. That way at least one of them is always clear.

Fincan has one [3/16] halfway between top of motor mount & bottom of coupler when installed. This one is large, as it's the part of flight that could "push" the payload off, if there is a pressure differential.

Gives you something to check your calcs. against.

Awesome, thanks! I'll do the calcs sometime this week and see how they compare.

The fit of the coupler on the aft section is a little loose and I would like a bit of insurance against drag separation,

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A layer or two of tape can take up the slack nicely. I use masking tape, or plastic polypropylene "slip tape", depending on the rocket and the gap I need to snug up.

I would just try and make sure the shoulder takes the thrust and that the airframe doesn't rock too much at the joint.

OverTheTop said:

A layer or two of tape can take up the slack nicely. I use masking tape, or plastic polypropylene "slip tape", depending on the rocket and the gap I need to snug up.

I would just try and make sure the shoulder takes the thrust and that the airframe doesn't rock too much at the joint.

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Tape is good for making sure the airframe doesn't cant at the joint. What's the gap?

Also, why not just use 2 #2 shear pins?

NateLowrie said:

Tape is good for making sure the airframe doesn't cant at the joint. What's the gap?

Also, why not just use 2 #2 shear pins?

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There isn't much of a gap, in fact I'd have to use pretty thin tape to get it to fit together at all. It's just loose enough to warrant something holding it together.

I could use 2-56 pins, but why use a different size when you're already using 4-40 on the NC.

Fearoflightning said:

There isn't much of a gap, in fact I'd have to use pretty thin tape to get it to fit together at all. It's just loose enough to warrant something holding it together.

I could use 2-56 pins, but why use a different size when you're already using 4-40 on the NC.

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By all means use 4-40 if it works. I suggested #2-56 just because of the small size. You don't need that much holding power.

There isn't much of a gap, in fact I'd have to use pretty thin tape to get it to fit together at all.

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Some of the Kapton, or similar, heatproof tapes are quite thin. Used on 3D printers a lot to protect the bed, so they are becoming more readily available and cheap.

OverTheTop said:

Some of the Kapton, or similar, heatproof tapes are quite thin. Used on 3D printers a lot to protect the bed, so they are becoming more readily available and cheap.

Click to expand...

Huh, never thought of that. I have a metric butt-ton of 1/2" Kapton tape, I'll have to give it a try...

Fearoflightning said:

...

Speaking of, I have heard that there are some mathematical methods for choosing the number of shear pins and their size. Can anyone enlighten me? I was simply thinking 4, 4-40 nylon screws for the main and three for the drogue.

...

Click to expand...

I found this which is helpful but doesn't really help with figuring out how
much force will try to pull the rocket apart (drag in one direction and momentum
in the other.)

https://www.feretich.com/rocketry/Resources/shearPins.html

Here's a couple of black powder sizing resources:

https://www.rimworld.com/nassarocketry/tools/chargecalc/index.html

https://hararocketry.org/hara/resources/how-to-size-ejection-charge/

FerdBerful said:

I found this which is helpful but doesn't really help with figuring out how
much force will try to pull the rocket apart (drag in one direction and momentum
in the other.)

https://www.feretich.com/rocketry/Resources/shearPins.html

Here's a couple of black powder sizing resources:

https://www.rimworld.com/nassarocketry/tools/chargecalc/index.html

https://hararocketry.org/hara/resources/how-to-size-ejection-charge/

Click to expand...

I knew I'd seen something more relevant. See this post:

https://www.rocketryforum.com/showt...-pins-to-use-and-how-many&p=670148#post670148

The whole thread has interesting info, but that one summarizes "the best" information.

FerdBerful said:

I knew I'd seen something more relevant. See this post:

https://www.rocketryforum.com/showt...-pins-to-use-and-how-many&p=670148#post670148

The whole thread has interesting info, but that one summarizes "the best" information.

Click to expand...

That's only half of the battle. The other big reason to have shear pins is to prevent premature separation from pressure build up due to vent holes not equalizing at the same rate as the atmospheric pressure decline.

The purpose of the vent holes is to release excess pressure in the airframe. When the rocket launches into the sky the air pressure drops rather quickly. If you don't have the vent holes, that pressure differential builds to the point where a lot of force is on the nosecone that could push the nosecone out.

Vent hole sizing is key because that controls the rate of equalization. As the rocket is going up, atmospheric pressure is decreasing. At the same time, the pressure difference on each side of the vent hole wants to equalize, so the vent will depressurize the airframe by releasing gas until the pressure equalizes. The rate at which is does is controlled by the size of the vent hole. Too small a hole and the result is that the atmosphere decreases at a rate far greater than the vent holes can equalize, which results in enough pressure buildup to pop off the nosecone. Too large isn't necessarily bad for most rockets, though it can be draggy and forces you to use more BP in the ejection charge.

Shear pins help mitigate the risk of pre-mature separation due to pressure differential. While it's not too big of a deal on smaller rockets, you can have 100+ lbs of force on a 6in rocket due to the area that the pressure is pushing against. If the internal pressure don't equalize to atmospheric pressure at a fast enough rate, as long as the shear pins rated shear strength is greater than the maximum pressure differential they mitigate the risk fully. To plot this, you would take a pressure output from a RockSim or Open Rocket simulation and feed it through a program that calculates the internal pressure at each interval of the flight. Use the maximum value of the graph in your sizing. I have a C command line program right now that does this.

I had an Ultimate Wildman a few years ago. Flew it about 12-13 times on Ms and Ns, including an N10,000. I used three 4-40 shear pins in the drouge section and on the nose for every flight. I also used three small button head cap screws to secure the payload section to the av-bay. Never had any issues. No need to complicate things with different sized pins for each section, or trying to find just the right tape to make the fit just right. Keep it simple.

Also, I used 6 grams of 4F BP in each section for every flight.

Rocketman248 said:

Also, I used 6 grams of 4F BP in each section for every flight.

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I was planning on using 6g as my backup charges. I'm going to start ejection testing at 4.5g. I have decided on 4 4-40 pins in the nosecone and 2 4-40 pins in the drogue. The latter is still slightly up in the air, but I like the large margin 4-40 pins give.

I will drill 2 1/8" holes on opposite sides and ends of each parachute bay just clear of the couplers to provide pressure relief from altitude change.

I will do ejection testing next week!

Rocketman248 said:

I had an Ultimate Wildman a few years ago. Flew it about 12-13 times on Ms and Ns, including an N10,000. I used three 4-40 shear pins in the drouge section and on the nose for every flight. I also used three small button head cap screws to secure the payload section to the av-bay. Never had any issues. No need to complicate things with different sized pins for each section, or trying to find just the right tape to make the fit just right. Keep it simple.

Click to expand...

Pretty much the same for me - my Ultimate QCC is basically and Ultimate Wildman - I use four 4x40 shear pins in Booster and same in Nose cone - 7 gram 4F as primary and 8 as backup and long harnesses. Lookup Ultimate QCC on YouTube and you will see the separation charge at apogee wasn't too much, don't skimp here - Griffin had a 6gram charge not separate his and had to rely on his 7gr backup. That rocket can't come in ballistic.

My payload section may be a little longer than yours but I tested at 6 grams and it separated fine but really didn't stretch the harness at all and the harness didn't pull the bunched sections apart. So after talking with GRIFFIN, Justin, Gus, Eric C decided I'm not risking a weak separation. I did however use a engine hone with 220 grit lightly in the ID of top of booster and top of payload to make a smooth fit but not loose.

Keep it simple, 3 or 4 4x40's test at 6 or 7, fly rocket, others have already figured this out for us - you will be fine. Going to be a great flight!

Picture of 7 gram in payload 4 pins

View attachment 313519

Picture of 7 gram in booster 4 pins - neither reached the end of the harness
View attachment 313520

Also I'm using a FWFG NC from mad cow. This may affect your fit a little bit.


You can search for my build thread " Ultimate QCC level 3" on here as well near the end if that would help.

Fearoflightning said:

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Where in tarnation did you get that critter?

I have screw switches but they are so daggum tiny and for bigger projects when I have the room (and weight isn't an issue) I'd much rather work with something larger.

-Dave

Missileworks: https://www.missileworks.com/store/#!/6-32-PCB-Screw-Switch/p/38076724/category=5760490

DAllen said:

Where in tarnation did you get that critter?

I have screw switches but they are so daggum tiny and for bigger projects when I have the room (and weight isn't an issue) I'd much rather work with something larger.

-Dave

Click to expand...

I got them from Chris short:

https://www.csrocketry.com/electronics/missleworks/6-32-screw-switch.html



About charge size, It seems that 6 grams is widely agreed upon, but that anything from 4 grams up will work fairly reliably. My backup charges will never be anything less than 6 grams, but I will have to see for myself during ejection testing what I am comfortable with my primaries being. I certainly would be more comfortable with an energetic separation than it just mediocrely sliding apart!

Thanks for the input!

blackbrandt said:

Missileworks: https://www.missileworks.com/store/#!/6-32-PCB-Screw-Switch/p/38076724/category=5760490

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THANKS!!!

I just bought 2 RRC2+ so how the heck did I miss that?????



(Dave goes to MW store and orders up a handful)

i used to make my own circuit boards so I have lots of scrap around. I make my own screw switches with brass screws and nuts. If I wasn't making them, I would certainly be buying them. I highly recommend the screw switches. Most reliable switch around IMHO.