Rookie HPR mistakes

[Michael L]

Is there a post for rookie HPR mistakes? If there is could the mod move this? If not... I'll go first

When you don't secure the parachute protector to keep it from sliding up the shock cord...

it slides up the shock cord. Luckily I sewed a loop in the shock cord for the parachute so it stopped there rather than continue up the shroud lines. I have a sequence of photos that shows the protector moving along the cord. The angle on this shot doesn't show it very well but the nosecone was swung out as far as the booster. It came down like a sick helicopter. No rocket damage though. Luck counts...

 

[Orien]

Well, last month I was oblivious to the changing and increasing winds. I was so obsessed with flight prep and going "HSF" (high, straight, fast) that I overlooked the warning signs that the transmission lines were now in play. The launch angle was actually downwind a little so it would weathercock back to vertical. Lost 2 cameras, an RRC3, a JLCR, brand new CTI 6XL case and spacers, Aeropack tailcone, and a Marco Polo tracking unit.

 

[Michael L]

Oh... dang I remember your post. I didn't realize that you didn't get it back. That's painful. Out here we don't have powerlines for miles (and miles). I'm really starting to appreciate our launch site more and more...

 

[Sandy H.]

I'd say one of the most common is mis-application of materials. It can go both ways, but I think most often for people new to HPR is to over-build.

For example, it is very easy to read over some of the great build threads of big, fast, giant-motor projects and go down the rabbit hole that your first HPR needs to be built with 3 layers of 10oz fiberglass tip to tip, when in reality, most L1 rockets are fine with just cardboard and wood glue.

To be clear, I'm not saying that epoxy and fiberglass should be avoided - much the opposite. I believe the model rockets that fly in LPR FAI competition are often made with fiberglass, but its super thin and super light and super strong for the weight it is. Personally, I enjoy working with light-weight fiberglass at times and have used it on MPR and HPR rockets, but I've never used carbon fiber, heavier fiberglass or other techniques that make sense for extreme rockets, as I don't fly anything extreme.

I definitely have overbuilt before and will probably do it again. For many common L1 motors, the stress of flight and recovery is nothing compared to transportation and storage (IMO) so if you overbuild so you don't kink a tube or knock a fin loose during transportation, I actually understand that. The extra effort and extra weight will result in lesser performance, but if maximizing performance isn't your goal and your goal if to enjoy building and enjoy flying with minimal breakage, then the rocket that some would consider overbuilt is actually built to match your specification exactly.

Sandy.

 

[timster68]

My biggest mistake was not looking at the thrust curve for an H115 when I attempted my L1 certification. I lost the NCR Big Brute (built with epoxy) I had built for that attempt an hour before and switched to a MDRM I built with wood glue and had launched on an F50. The fins shredded on the way up in a spectacular fashion. We thought the motor had CATOed because we thought we saw flames as it flew apart, but the motor was intact.

 

[AHansom]

Not resetting the Raven correctly to abort the air starts if things are not going as planned. Click on the picture to go to the flicker page and scroll down for more pictures and comentery by Steve Jurvetson. Steve is a regular at the launches and does quite a bit to promote rocketry!!!!

 

[teepot]

I forgot to attach the nomex blanket to the shock cord once. The rocket went to 3400' ejected the chute bundled in a JCLR and I see something yellow floating away. At first I thought it was the chute. But as everything got lower I was relieved it was only the blanket drifting into the desert. Another time I forgot to take the rubber bands around the chute off. Result one broken fin.

 

[Igotnothing]

<<Looks sideways at "the rubber bands around the chute ". Takes a second, more direct look at "the rubber bands around the chute ".>>

We are really over-due for a chute-packing clinic around here. Rubber bands go over a z-fold loop in the shroud lines, not over the chute itself. They help prevent a shroud line from getting over the chute itself.

Some lessons take better if it is a man-rated chute and your butt is in the harness. I have thrown laundry twice in anger. It worked 3 times. If it only worked twice I would be dead or crippled.

 

[ghostfather]

Built a fairly straightforward dual deploy rocket, put a tried-n-true PerfectFlite altimeter in on a 3D-printed sled, hooked everything up and tested it.

Now I was using a magnetic arming switch for the first time (this was before the Tripoli rule limiting their use) instead of a bayonet "Remove before Flight" switch. Load it on the pad, wave a magnet in the right place, and you hear it beeping faintly that it's armed.

....but then the drogue parachute didn't come out, though the backup motor ejection pushed it out. Coming down, but then the Main parachute didn't come out. Came in a bit hard, but no real damage. Upon examining the electronics, I found that both charges never fired.

Scratched my head, but then it dawned on me. The hole to arm a bayonet switch also allows air for a barometric altimeter to enter the e-bay. Guess what I didn't drill because I was using a magnetic switch?

 

[Antares JS]

I learned most of these the hard way as I was starting out in HPR.

-If you build a QT kit from PML, ABSOLUTELY, POSITIVELY, 100% scuff any QT bonding surfaces with some 100 grit sandpaper before trying to bond anything to it. We should do this for everything, but it's especially important for QT as epoxy will NOT bond well to smooth plastic.

-Consider motor retention BEFORE starting to build your kit. It's much easier to install your motor retainer if you plan ahead and make sure you have enough motor tube sticking out the back to install your retainer. Not all rockets have enough centering ring to put Z-clips on later!

-Addendum to above: DO NOT rely on friction fit to hold your expensive motor case in place. (Thankfully I did not learn this one the hard way, but saw several others learn it the hard way.)

-Five minute epoxy is not always strong enough for the job you're doing. For fin fillets in particular, ALWAYS use a strong, slow-curing epoxy. Also, five-minute epoxy doesn't have enough working time to make a nice looking fillet.

-If you have a vendor who comes to your launches, try to buy something from him every time he's there, even if it's something small. It encourages the vendors to keep coming back so he'll be there when you need something big. (Learned this the hard way but not with regards to rocketry.)

 

[boatgeek]

<<Looks sideways at "the rubber bands around the chute ". Takes a second, more direct look at "the rubber bands around the chute ".>>

We are really over-due for a chute-packing clinic around here. Rubber bands go over a z-fold loop in the shroud lines, not over the chute itself. They help prevent a shroud line from getting over the chute itself.

Some lessons take better if it is a man-rated chute and your butt is in the harness. I have thrown laundry twice in anger. It worked 3 times. If it only worked twice I would be dead or crippled.

My understanding of the post was that the rubber bands were around the chute for storage and never got pulled off for flight.

Mine is:
-Never use an eye screw through a plywood bulkhead for chute retention, no matter how small the rocket is. Pulled out on the first flight. Fortunately, the airframe fell on soft sod without damage and the nose cone and chute were recovered a mile away.

And a near-miss:
-If an altimeter seems flaky, don't fly it. Pull it off the flight line and fix whatever's wrong. That saved a flight for me.

 

[Citizen Baslim]

When assembling an AT motor with motor ejection, don't get lubricant where it blocks the hole to the charge well...the burning delay won't be able ignite the ejection charge and you'll have a lawn dart. Sad but true.

 

[Citizen Baslim]

Read the instructions. If it's been awhile since you've assembled something (like using spacers in an AT motor case) consider yourself a "momentary rookie" and re-read the instructions.

 

[Antares JS]

When assembling an AT motor with motor ejection, don't get lubricant where it blocks the hole to the charge well...the burning delay won't be able ignite the ejection charge and you'll have a lawn dart. Sad but true.

That one reminded me as well...

-Don't just dump your BP into the ejection well and call it good. Start by putting in a little at a time, and use some sort of sharp tool to make sure it goes down the hole. Once the hole is filled and no more BP will go down it, then you can dump the rest in.

I had multiple RMS ejection charge failures before I started doing this. Never have had a failure since.

 

[Bat-mite]

Number one error I see (and have experienced!) with new and eager HPR fliers is "Go Fever!" The excitement of the launch disables the part of the brain that is supposed to day, "Today is not a good day for this particular launch." Learn to say, "Hmm, let's put this off till next month."

Number two is lack of a tracker. "I'm going for 3000 feet!" "How are you going to find it when it comes down?" "I'll just watch it down." Then it comes down behind a grove of trees, or drifts into some low clouds and no one sees it come out again.

Number three is not knowing how to size parachutes, and not using dual deployment for high altitude flights. We had a group of college come out to certify level one. They each had their own rocket, but they were sharing a motor casing. The first one up launched a cardboard rocket to about 3500', deployed an oversized main chute at apogee, then watched the rocket drift for about ten minutes until it went behind trees about two miles away. They never found it, lost their shared casing, and no one certified.

 

[Antares JS]

Number three is not knowing how to size parachutes, and not using dual deployment for high altitude flights. We had a group of college come out to certify level one. They each had their own rocket, but they were sharing a motor casing. The first one up launched a cardboard rocket to about 3500', deployed an oversized main chute at apogee, then watched the rocket drift for about ten minutes until it went behind trees about two miles away. They never found it, lost their shared casing, and no one certified.

Big oof to that.

 

[dr wogz]

• Thinking big numbers = big (impressive) flights.. "It few fine on an H128. Lets put in an H550!!"
• Thinking an H motor (or any H or I motor) will do for the L1 flight. I once did have to refuse an L1 attempt as they had a 7lb rocket with an H128 or something small / marginal..
• Thinking it's a race.. I got my L1, now it's time for my L2 (at the next launch or later the same day!)
• Buying a CTI reload, and either not knowing it needs a case, or forgetting to put it in it's case!

 

[heada]

Having your dual deploy rocket arch over and not deploy at apogee just to realize you forgot to arm the electronics on the pad which is then followed by watching in horror while it comes in ballistic. (Get and follow a checklist for every flight!)

 

[Bat-mite]

My best advice to someone seeking L1 certification would be to study the L2 exam materials. Personally, I think the L2 exam should be the L1 exam! Why do we let people fly HPR without knowing the basics of rocket flight?

We had a guy come out to certify L1. Had a scratch built rocket and an H motor. Didn't know where his CP was, didn't know how fast or how high the thing would go, need know how to estimate delay time or drill the delay. I got the impression that he really didn't know anything -- just stick the motor in and magic happens. Didn't have a successful launch and I never saw him again.

 

[mrwalsh85]

Make sure you close the quick link. I didn't learn the hard way, but it was certainly an eye opener. Main shook out at apogee, kept the slack on the open quick link. As soon as I picked it up after landing, a little rattle in the body tube and the shock cord fell out. Quick link is spread open. I keep it in my range box as a reminder, and kind of a cool "damn, that was close" story.

 

[PayLoad]

No, the paint still isn't dry dammit

 

[Antares JS]

Some of these tips also point to another big one I forgot in my first post...

-Don't start out in HPR. Fly at least a dozen LPR's of varying sizes and types before trying your first HPR. That experience will really help you avoid the dumbest mistakes.

I can at least honestly say that most of my early HPR problems stemmed from using materials I wasn't used to and not realizing I needed to supply motor retention separately. Spoiled by Estes!

 

[Antares JS]

No, the paint still isn't dry dammit

Especially if it's metallic paint. Metallic paint is never really dry.

 

[Bat-mite]

Make sure you close the quick link. I didn't learn the hard way, but it was certainly an eye opener. Main shook out at apogee, kept the slack on the open quick link. As soon as I picked it up after landing, a little rattle in the body tube and the shock cord fell out. Quick link is spread open. I keep it in my range box as a reminder, and kind of a cool "damn, that was close" story.

Man, I had a problem with that just a few months ago. 8" FG rocket, 75# on the pad ... Iprep everything at home, so that when I get to the field, I just slide in the recovery packages, attach the quick links, screw in the shear pins, and go launch.

I had a large SS quick link on the main harness with the main chute also attached. My NC bulkhead is recessed, so I have to reach up in there to attach the quick link. No problem, screwed it on, pulled on it, good to go. Shear pins in the NC and off to the pad.

What I didn't realize is that the main harness slipped off the quick link while I was reaching it up in there. So, the main chute was linked to the NC, but the main harness was not.

This happened. Go to 3:45. Fortunately, everything was undamaged and easily recovered.

 

[Michael L]

Some of these tips also point to another big one I forgot in my first post...

-Don't start out in HPR. Fly at least a dozen LPR's of varying sizes and types before trying your first HPR. That experience will really help you avoid the dumbest mistakes.

I can at least honestly say that most of my early HPR problems stemmed from using materials I wasn't used to and not realizing I needed to supply motor retention separately. Spoiled by Estes!

I had the help of 3 club members through the build process. I took almost a year to finish the rocket (LOC IV). Not because it was difficult to build. I'm just an over thinker. I built everything carefully. Sometimes I wouldn't do anything for a couple of weeks. I added an Av bay. That changed the Cg. I went with rail guides rather that the launch lug. Beveled the fins rather than leave them square. Built it for dual deploy with the intention of using motor deploy for the L1 cert flight. That turned out to be the change that affected the rocket the most. All of the changes added more time and more education.

I read everything I could get my hands on, including the L2 test material even though I was going for my L1. I don't know how many C and D sized rockets I flew with my grandsons. A lot. I bought motors in bulk We still fly them when I see them. Sometimes it's nice to fly without the complexity.

I called off my first L1 attempt because of a few problems that I couldn't solve in time. Cg... When I measured it (with a string around the body tube) the Cg was forward of the Cp but only by an inch and a half. The sim didn't match. It didn't feel right. So... I put it off for a month and was a spectator one more time. The L1 cert went off with no issues, not counting being nervous.

I have L2 on my mind but no real plans to cert yet. The LOC IV could be used for the L2 (I've change the payload bay. It's now 5" longer. I may have to start calling it the LOCenstein) but I think I want to up my game and work with fiberglass next. I've also been eyeing the sustainer of the LOC IV. It looks like it would make a fine 1st stage for a 2 stage rocket

 

[Igotnothing]

My understanding of the post was that the rubber bands were around the chute for storage and never got pulled off for flight.

Mine is:
-Never use an eye screw through a plywood bulkhead for chute retention, no matter how small the rocket is. Pulled out on the first flight. Fortunately, the airframe fell on soft sod without damage and the nose cone and chute were recovered a mile away.

And a near-miss:
-If an altimeter seems flaky, don't fly it. Pull it off the flight line and fix whatever's wrong. That saved a flight for me.

That was my understanding as well. It is not a good way to store a chute.

 

[Steve Shannon]

1. Placing the delay grain o-ring around the cardboard delay grain spacer rather than the delay grain in a small AT motor.
2. Throwing away your first metal seal disk.
3. Forgetting the metal washer under the ejection charge in a Aerotech DMS motor.
4. Not realizing that a CTI reload must go into a metal case.
5. Using too much grease in either a Loki or AT forward closure and having the ejection charge fail to ignite.
6. Forgetting the BP on a motor you built previously.
7. Forgetting to turn on avionics.

Full confession: I’m guilty of 1, 6, and 7.

 

[DMC12]

Forgetting to drill a pressure release hole in the body tube is easy to do. I had been flying high powere for years and forgot once. Pressure separation is no fun!

 

[prfesser]

1. Placing the delay grain o-ring around the cardboard delay grain spacer rather than the delay grain in a small AT motor.
2. Throwing away your first metal seal disk.
3. Forgetting the metal washer under the ejection charge in a Aerotech DMS motor.
4. Not realizing that a CTI reload must go into a metal case.
5. Using too much grease in either a Loki or AT forward closure and having the ejection charge fail to ignite.
6. Forgetting the BP on a motor you built previously.
7. Forgetting to turn on avionics.

Full confession: I’m guilty of 1, 6, and 7.

#4 has GOT to be the top rookie mistake! I've seen it several times and I don't go to many big launches.

Best -- Terry

 

[teepot]

That was my understanding as well. It is not a good way to store a chute.

After that incident I don't do that anymore.