Rookie HPR mistakes

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dr wogz

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"What is the best glue" on any public forum..

It is the same as asking: "who was the best (or worst) president".. everyone has an opinion, and is almost as heated! :D

Some might say JB weld on fillets is overkill, whereas some will use their F-350 to go buy milk..
 

Chad

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on my first L1 attempt my oldest son disconnected the quick link to the top half of the airframe (he was watching me and trying to help heh). The nosecone and payload section fell/floated down very serenely and landed without any damage. ( 4" cardboard madcow dx3 )

ever since, i use a very specific checklist on a clipboard for all flights
 

Rocketclar

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I had launched (and still do) lots of mod and mid-power rockets. There are no short cuts with HP that I have personally found. So I made some of the rookie mistakes....
a. early mistake.....using the elastic band that came with the rocket instead of a stronger material. (Gosh, I had used those in low and mid power for years with no problem.)
b. wired my drogue and main backwards.....now I use unique connectors to minimize that mistake.
c. got distracted talking to a bystander prepping my rocket....didn't connect a d-link to my custom made NC. That mistake made an impression on that club so my misfortune has helped them remember at least that....BTW....I found my NC based on slowing down the onboard video to see where it landed.
d. most recent mistake....forgetting to ARM the Proton flight computer!
 

dr wogz

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Especially for the 'building motors the night before':

Take the Motor face card from the packet. Mark on it the delay used / drilled to. Also mark intended rocket it'll be used for. Build motor. (Assemble motor?!)

then either:
  • Rubber-band it (and igniter) to the motor case.
  • Rubber-band it (and igniter) to the rocket body ONCE THE MOTOR IS INSERTED into the rocket.

And you'll never be unsure of what motor is what, and what delay it has..
 

Troy3003

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1) Don't 100% depend on motor eject if at all possible..
2) Setting a heat source near freshly injected fillets that are seeping a little to try and speed up the cure. Well, that will give you just the opposite of the desired effect.
 

AHansom

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Was told at the check in table I needed to add booster lights to my Night Flyer to make it night safe in case of separation. A quick trip to the vendor trailer and I taped some LED strip lights up and down the booster then tightly taped the battery at the transition coupler. The motor ejection, main ejection and backup couldn't overcome the friction. Beautiful K sparky up and a long long whistle coming back down. Made a 7 foot rocket into a 3 footer real quick. Never noticed the problem because the booster was shear pinned to the transition.

IMG_1961.jpg

IMG_3970.jpg
 
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plugger

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Plugger, Almost seems like there is a story behind that advice ???
No real story Glasspack, other than I've been there in the past and I've since moved past it.

When you get into the hobby it's funny the things you choose to focus on, convince yourself of, and the things you ignore. But often over time logic wins out.
 

OverTheTop

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No real story Glasspack, other than I've been there in the past and I've since moved past it.

When you get into the hobby it's funny the things you choose to focus on, convince yourself of, and the things you ignore. But often over time logic wins out.
+1, same here.
 

Rocketless

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At the end of the day, it is the same reason we use it on the retainers. Heat. Pretty much any epoxy will give you enough hold to keep the retainer on the rocket if it is cold, but JB Weld retains its hold even when it gets very hot.

Same principle for surface mounted fins on a minimum diameter rocket. The heat may not be high enough to go over the Fiberglass' Tg temperature, but it could get high enough to soften the epoxy on the fin mount and cause the fin to pop off. Combine that with the fact that I (and most people, it seems) like to fly their minimum diameter rockets at extreme speeds (Mach 2 or 3+), and JB Weld again seems to be the natural choice.

It is more of a "why not?" thing. If you have JB Weld and you are making a minimum diameter rocket and you know it is going to get hot, why not use an adhesive you know works well in extreme heat and is really thick, which makes excellent fillets? If you are building a rocket that cost hundreds of dollars, are you really going to skimp on the fillets?
Exactly, and at that point are you really worried about the extra weight of JB Weld??
And I know for a fact that you can make nice looking filets with JB Weld
 

Rocketless

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Yes, as a professional pilot we are required by policy and law to use a checklist. I will be developing several for my needs and most of the folks in my club use one.
Please share it with us!
 

mket

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Problem with epoxy is it becomes brittle over time

Mike
 

tfish

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I wrote this a couple of years ago for Spaceport America teams..it should apply here as well...

Over the years I have noticed a few things (issues) with rockets that failed to meet their flight expectations. Below is a list of items that come to mind, in no particular order.

COTS motors: My advise is to read the motor instructions. Under stand them. And follow them. If something in the instructions or the actual motor components does not make sense, contact your motor vendor. If the instructions say to glue the grains in, in a particular order, with 'this glue" 24.2 hours before use..do it!

SRAD motors: Nothing beats static testing with data. Scale motors up to your flight motor. Does the data look consistent with what you think it should look like? Grain configuration and Formula changes. Make small changes with these items. Is it doing what you want it to do or think it should be doing? And static test! I know I've already said this but it is important!

Fins (shape, size, material and attachment): If the fins are to small, too flimsy or poorly attached, your flight probably won't turn out well..if it gets that far! I say 'that far' because "fins" are one of our 'critical' (no fly) items during your Flight Safety Review. The fins need to stay attached, for the rocket to go where we point them. The following are not rules. They are what I use and recommend to my fellow fliers. I like my fins to have a simi span of 1.1 calibers. I do not like short 'rooted' fins like the Nike Smoke. Longer root cords seem to help dampen against 'vibration' issues. Be careful of swept back trailing edges. They are 'unsupported' and the tips can break off in flight. Attachment: welding (NOT to motor cases), bolting or gluing. All can work. The entire project rests on this attachment point. Epoxy and fillets bond in one of two ways. A chemical bond: works of clean, fresh and compatible materials. Mechanical bond: attaches itself via roughed up surfaces. I use the mechanical method. I use 60 grill sand paper and a hacksaw blade to really scratch up the surfaces. to give the epoxy a place to bond to. Fin Material: Metal, wood and composites will all work. If you're not sure if your fin shape and material choice is strong enough, clamp the root edge of one of your fins into a vise. Can you flex it, bend it or break it? No? Then your fin shape and material choice are probably good.

Altimeters (COTS): Be familiar with them and how they work. What beeps are you listening for when you arm the electronics? Beep Beep Beep? Have printed instructions with you to figure out what 'abnormal" beeps are trying to tell you. Do you have the proper vent holes for your altimeter brand? Batteries: how are your batteries mounted? Will your battery mounts fail under your planned 20-60 G's flight? How long will the batteries last? This applies to altimeters, video cameras, GPS and payload batteries. Best to have batteries that last 3 or more times your expected usage times.

Deployment Charges: 10K flights, The best thing is to ground test them! Once you find something that works, don't change it! Small changes can make a big difference, good and bad..mostly bad.
30K and Demo flights. These teams have a lot more to over come because of the altitude the rockets will be going. The following applies to BP and CO2 ejection systems. Things teams may or may not have to take into account when designing their "High Altitude Ejection Systems" is expected MSL altitude, Lower atmospheric pressure, temperature at altitude and scattering of the BP (if BP is used). A Flight Safety Judge will be contacting these teams in regards to what they have come up with.

Rail buttons: We see rail buttons pop off while rockets are being loaded onto the rails. Rail Buttons need to be securely attached to the rocket! A wood/sheet metal screw into a .060" thick fiberglass tube is NOT securely! Bolts with washers and nuts work. Screws can work if they are screwed into a strong backing material.

Parachutes and recovery gear: I'm often asked how "strong" do things need to be? It all really depends on how big and heavy is your rocket? Most people think the rocket is going to fly straight up to apogee, loose it's kinetic energy, stop and the parachute will deploy. That rarely happens! More then likely your rockets will be traveling at 20 - 60 mph when your recovery gear gets deployed. Will your chute, recovery cord, anchor points, knots and your $0.79 3/16 quick link rated at 660# hold up? Don't wait until the rocket is built to decide how much and how strong of stuff you can get in the rocket. Build the rocket to fit the motor, payload, altimeters and proper recovery gear.

Not many parts of a rocket can fail and still have a good flight!

Tony
 

Greg Furtman

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Was told at the check in table I needed to add booster lights to my Night Flyer to make it night safe in case of separation. A quick trip to the vendor trailer and I taped some LED strip lights up and down the booster then tightly taped the battery at the transition coupler. The motor ejection, main ejection and backup couldn't overcome the friction. Beautiful K sparky up and a long long whistle coming back down. Made a 7 foot rocket into a 3 footer real quick. Never noticed the problem because the booster was shear pinned to the transition.

View attachment 468873
View attachment 468872
As we say up north here, uff da!
 

Donnager

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Especially for the 'building motors the night before':

Take the Motor face card from the packet. Mark on it the delay used / drilled to. Also mark intended rocket it'll be used for. Build motor. (Assemble motor?!)

then either:
  • Rubber-band it (and igniter) to the motor case.
  • Rubber-band it (and igniter) to the rocket body ONCE THE MOTOR IS INSERTED into the rocket.

And you'll never be unsure of what motor is what, and what delay it has..
The only difference for me is I usually write the motor size with the drilled delay (H-238-8) on a piece of masking tape in large writing on the case. When it is burned, I pull the tape and re-label for the next load. My rubber band skills are lacking.
 

dr wogz

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The only difference for me is I usually write the motor size with the drilled delay (H-238-8) on a piece of masking tape in large writing on the case. When it is burned, I pull the tape and re-label for the next load. My rubber band skills are lacking.
that works too!
 

prfesser

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Using the little loop on a molded nose cone as an attachment point for the recovery system.

Instead:
  • Cut a hole in the side of the shoulder, large enough to drop a washer in (large washer preferred) and large enough to fit a wrench.
  • Insert an eyebolt into the hole at the bottom of the nose cone.
  • Washer into nose cone, on the eyebolt
  • Nut on eyebolt.
  • Insert wrench, tighten nut by turning the eyebolt.
  • Add a second nut as a jam nut.
  • Add epoxy to the nuts and the thread of the eyebolt so it ain't going nowhere. Now you have a proper attachment point.
 

heada

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Using the little loop on a molded nose cone as an attachment point for the recovery system.

Instead:
  • Cut a hole in the side of the shoulder, large enough to drop a washer in (large washer preferred) and large enough to fit a wrench.
  • Insert an eyebolt into the hole at the bottom of the nose cone.
  • Washer into nose cone, on the eyebolt
  • Nut on eyebolt.
  • Insert wrench, tighten nut by turning the eyebolt.
  • Add a second nut as a jam nut.
  • Add epoxy to the nuts and the thread of the eyebolt so it ain't going nowhere. Now you have a proper attachment point.
I do a slightly different method.

Drill 1/2" holes on either side of the molded loop on the base of the nosecone (not through the shoulder, through the base). The holes should be near the shoulder but not on the shoulder. Shoulder should be free of objects/"stuff" that would prevent it from sliding in or out of the bodytube. Feed the shockcord in one of the holes, through the nosecone and then out the other hole. Then feed one end of the cord through the loop of the other end.

- No additional parts are needed
- loading is spread over the entire width of the cord inside the bottom of the nosecone
- no knot, eyebolt, nut or quick-link to come undone
- cord can still easily be replaced
 

MidOH

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On my low power and FG stuff, I tie the recovery gear straight to the shock cord. The shock cord only passes through the loop for the nose cone on its way to the main. If the nose cone string pulls free, or an eyelet fails, I only lose a nose cone, not the rest of the rocket.

No idea if that applies at all to HP stuff.
 
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