Launch day lessons learned.

[Senior Space Cadet]

A couple weeks ago, I launched the first scratch build I'd done. It flew straight and I took it home unscathed, but was a little disappointed with it's speed and height.
Yesterday I launched four of my other five scratch builds, including two with arrow vanes for fins. None of them went careening out of control and I took all of them home unscathed, except for the attachment point on one of the nose cones that, apparently, broke off with the force of ejection.
That isn't to say that I'm happy with how they all performed. I'd be a liar if I said they flew perfectly.
I'm still learning the best way to pack a chute. Fortunately, it seems that as long as the chute comes out of the rocket, and stays attached, it creates enough drag to prevent damage to the rocket.
Some of my launch lugs must not be aligned perfectly because there was drag on the launch rods. I've got to come up with a solution for that.
The three 24 mm body tube rockets all had less than perfect flight paths. Even the one that didn't have arrow vane fins.
The only rocket I was totally happy with was the 29 mm build, the last one I did. It is very long with four large fins and I put a D motor in it and it flew high and perfectly straight.
I've learned quite a bit since building all my 24 mm rockets, including how to use Open Rocket. I intended a BT-55 and a BT-60 to be my next builds, but not being happy with any of my smaller rockets, I've decided to make another 24 mm rocket first, using Open Rocket and what I've learned. I have some Quest (Aerotech) 18 mm D16 motors for it, so it should fly high and fast.
Smaller rockets might not be as dramatic, especially when you start using motors more than a D, but they are easier to transport, and my launch area is limited in size. Until I go for Mach 1, I have no problem with 24 mm.
The one rocket I didn't launch was my BT-80 build. I didn't feel like my launch rod was long enough.

 

[MOF410]

Did u use OR to design them before building? My first few builds were done without OR and I did not have the best cog and cop. I did test them w the string for stability and added some nose cone weight to balance, but I could've benefitted from doing some design work on the computer first.

For launch lug alignment I use a laser level that i have for work to ensure they are aligned perfectly and havent had much trouble. If u build alot of rockets might be worth the investment.

 

[neil_w]

Just use a launch rod to check lug alignment during construction.

 

[kyle]

Or a section of aluminum angle taped to the body tube while tacking on the lugs.

 

[dr wogz]

I typically will slide my lugs onto a rod / tube, then tape this to the rocket, then add glue. The rod does 2 things:

• ensures they are straight & aligned to each other
• ensures the lugs don't collapse as the glue dries / cures. (I've had some weak lugs go from round to flat oval as the yellow glue dries. It will shrink, therefore collapsing the tiny tubes..)

I'll slide the lugs around a bit as I align the rod / tube to the axis of the BT, to get glue under the lug. (But do take care, as you can work glue into the lug - rod joint..)

I have a few short lengths of aluminum tubes for this purpose; 1/8" dia & 3/16" dia (KS Metal, at most local hobby shops). Nice, light, and not too long, Easy to manage! Don't use a wooden dowel, as they are never straight! (or round!)

https://www.ksmetals.com/

Senior,
Can you (re)describe your first scratch builds for us? Why were you disappointing with their speeds & heights? Motor not big enough? Rocket too heavy / draggy? Binding on the rod? (Rod not clean / has a step that catches the lugs?)

How long are your shock cords? You mentioned you broke an attachment eye on one nose cone.. Material?

You say you weren't happy with the three 24mm rockets. Was that a 24mm body tube? or a 24mm motor? Why were you unhappy with them? What motors? (Motors not up to snuff for the design?)

what motors are you typically using? You mention "D" motors.. Estes D12-3/5/7? Quest D16? Black powder & APCL burn quite differently, each having different thrust curves.

Heavier rockets, such as your intended BT-80 should be on a 3/16" x 48" rod. I believe OR will let you set the rod length, so you can see your rod exit velocities.. It will give you a warning if it is below a certain speed (Default settings)..



This is all part of learning, and seeing the results! Glad you got out to launch a few!

 

[jrap330]

A couple weeks ago, I launched the first scratch build I'd done. It flew straight and I took it home unscathed, but was a little disappointed with it's speed and height.
Yesterday I launched four of my other five scratch builds, including two with arrow vanes for fins. None of them went careening out of control and I took all of them home unscathed, except for the attachment point on one of the nose cones that, apparently, broke off with the force of ejection.
That isn't to say that I'm happy with how they all performed. I'd be a liar if I said they flew perfectly.
I'm still learning the best way to pack a chute. Fortunately, it seems that as long as the chute comes out of the rocket, and stays attached, it creates enough drag to prevent damage to the rocket.
Some of my launch lugs must not be aligned perfectly because there was drag on the launch rods. I've got to come up with a solution for that.
The three 24 mm body tube rockets all had less than perfect flight paths. Even the one that didn't have arrow vane fins.
The only rocket I was totally happy with was the 29 mm build, the last one I did. It is very long with four large fins and I put a D motor in it and it flew high and perfectly straight.
I've learned quite a bit since building all my 24 mm rockets, including how to use Open Rocket. I intended a BT-55 and a BT-60 to be my next builds, but not being happy with any of my smaller rockets, I've decided to make another 24 mm rocket first, using Open Rocket and what I've learned. I have some Quest (Aerotech) 18 mm D16 motors for it, so it should fly high and fast.
Smaller rockets might not be as dramatic, especially when you start using motors more than a D, but they are easier to transport, and my launch area is limited in size. Until I go for Mach 1, I have no problem with 24 mm.
The one rocket I didn't launch was my BT-80 build. I didn't feel like my launch rod was long enough.

Launch lugs...I can not tell you why...but if any of my rockets seems to bind on the rod...I do a physical test by moving my rocket up/down the rod 2-3 times...and suddenly there is NO bind. Also after a few flights and I mean 3 flights....get a rag and wipe down (clean) the rod..especially with a little oil on the rag. Keep this oily, dirty rag in your range box., It will work/help you forever. And again..you want high...extra pair of eyes to track and field to recover. I have never launch above an Estes D...and yes the bigger engines are more exciting... But also love my C flights.

 

[neil_w]

Also after a few flights and I mean 3 flights....get a rag and wipe down (clean) the rod..especially with a little oil on the rag. Keep this oily, dirty rag in your range box.

Might I suggest as an alternative a piece of waxed paper. Gets the rod nice and slick, doesn't leave any liquidy residue behind.

 

[MOF410]

I was gonna ask about best techniques for polishing my rod...google seemed to think I was talking about something else...lol

Should I use something like lithium grease or motor oil to clean up my rod between launches?

Wax paper sounds like a good idea as well.

Thanks for the help!

 

[heada]

I spray the rod with WD-40 and use 0000 steel wool to clean and then wipe with a clean dry paper towel. It ends up clean and polished without any residue that'll pickup junk from the next launch easily.

 

[Ronz Rocketz]

After a couple launches, the rod gets “carbon scoring” so I rub talc on it. I’ll try the wax paper next time.

 

[dr wogz]

I've found the best this is:
A piano wire rod. has to be piano wire.
Polish it with steel wool or #400, 600 or higher wet n' dry paper. it'll get super slick & slippery! I polish it before each launch, then wipe it down after the day's launching..

it'll get a slight surface rust after a while, but that wipes off easily enough with the pre-launch polishing. Adding WD-40 or any other lube / grease just makes a mess, and you'll then have greasy lu
gs..

 

[neil_w]

After a couple launches, the rod gets “carbon scoring” so I rub talc on it. I’ll try the wax paper next time.

FWIW I keep a folded-up piece of waxed paper in my range box, and use it liberally at club launches, since the rods there are often not exactly in "like-new" condition. I'll often give them a good steel wool rub first, but often they're not satisfactorily slick until I deploy the waxed paper.

That suggestion was given by another TRF user a few years ago, which I could remember who. Maybe Hornet Driver, but not certain. Wish he were still around doing his amazing builds. But I digress.

 

[jrap330]

Might I suggest as an alternative a piece of waxed paper. Gets the rod nice and slick, doesn't leave any liquidy residue behind.

I read every advice after my advice....main thing get the carbon/exhaust built up off the rod and whether wax paper, WD-40, talc or an oily rag or silicon spray rag which I used around the house...anything to keep it (rod) slightly slippery. Piano wire...everyone stated expensive.....lets keep OP cost down......my 20 year Estes rod still doing its job.

 

[Cape Byron]

I clean with WD40, wipe with a clean dry rag then use car wax and buff. Same stainless rods for 20 years.

 

[NateB]

Adding WD-40 or any other lube

Minor, first-world pet peeve: WD-40 is not a lubricant. It is a water dispersant and rust dissolver. Some of the solvents give it short lived lubricating properties, but will do more harm than good when used as a lubricant. On a rocket rod, it will certainly help clean and dissolve the solid particles left behind, but the purpose isn't lubricating anything.

 

[dr wogz]

ditto, but soooooooooooooooooooooooooooooo many people use it as a lube..

little do they know:
WD = Water Displacement

 

[Ronz Rocketz]

Eau de fishoil cologne

 

[Senior Space Cadet]

Whew! I'll try and respond to most of these posts here.
I've got the rod all polished up with super fine steel wool. It's definitely the lugs and not the rod. I'll try wax or something.
Only minor binding, but maybe enough to have negative effects.
I'll try some of the alignment suggestions and make sure there is nothing inside the lugs that's causing the binding.
The only one of these rockets that was designed after I learned how to use Open rocket and got more info from you guys, was the most recent build, which has a 29mm body and 24mm motor, and that one flew great, though probably over stable.
All of the 24mm body rockets had weight added to the nose cone because I wanted to be sure they were stable. I had visions of rockets flying crazily and hitting someone. This, along with some binding in the lugs, might have resulted in slow speeds off the rod, which might have been a factor in their flight characteristics.
I saw some fishtailing, some smoke trails that looked like cork screws, and some flights that I thought should have gone higher. Not a disaster, but I could have been happier.
In a couple of cases, I feel that fin alignment might have been a problem. I've been trying to go to slotted tubes, but I haven't found them in the smaller sizes.
One reason the first rocket might have flown straight, but not very high (for the motor I used) was I made that rocket before I learned that spin was a no-no. It spun beautifully.
I'm thinking of building two new 24mm rockets. Same stability factor for both, but one longish with small fins and one shortish with big fins. Flight simulations seem to favor the long rocket with small fins, but I'd like to see how they fly. Apogee isn't everything.

 

[William Dieckmann]

Minor, first-world pet peeve: WD-40 is not a lubricant. It is a water dispersant and rust dissolver. Some of the solvents give it short lived lubricating properties, but will do more harm than good when used as a lubricant. On a rocket rod, it will certainly help clean and dissolve the solid particles left behind, but the purpose isn't lubricating anything.

Finally someone that knows WD is not a lubricant but a solvent and water displacement. And it took 40 times to get it right thus the name WD40

 

[neil_w]

In a couple of cases, I feel that fin alignment might have been a problem. I've been trying to go to slotted tubes, but I haven't found them in the smaller sizes.

1) Slotting your own LPR tubes is easy.
2) You don't need slotted tubes to get straight fins. There are any number of alignment jigs you can use to ensure surface-mounted fins are straight, if your eyeballs are not up to the task.
3) *Slight* fin misalignment doesn't have much affect on flight.

 

[jrap330]

ditto, but soooooooooooooooooooooooooooooo many people use it as a lube

Whew! I'll try and respond to most of these posts here.
I've got the rod all polished up with super fine steel wool. It's definitely the lugs and not the rod. I'll try wax or something.
Only minor binding, but maybe enough to have negative effects.
I'll try some of the alignment suggestions and make sure there is nothing inside the lugs that's causing the binding.
The only one of these rockets that was designed after I learned how to use Open rocket and got more info from you guys, was the most recent build, which has a 29mm body and 24mm motor, and that one flew great, though probably over stable.
All of the 24mm body rockets had weight added to the nose cone because I wanted to be sure they were stable. I had visions of rockets flying crazily and hitting someone. This, along with some binding in the lugs, might have resulted in slow speeds off the rod, which might have been a factor in their flight characteristics.
I saw some fishtailing, some smoke trails that looked like cork screws, and some flights that I thought should have gone higher. Not a disaster, but I could have been happier.
In a couple of cases, I feel that fin alignment might have been a problem. I've been trying to go to slotted tubes, but I haven't found them in the smaller sizes.
One reason the first rocket might have flown straight, but not very high (for the motor I used) was I made that rocket before I learned that spin was a no-no. It spun beautifully.
I'm thinking of building two new 24mm rockets. Same stability factor for both, but one longish with small fins and one shortish with big fins. Flight simulations seem to favor the long rocket with small fins, but I'd like to see how they fly. Apogee isn't everything.

Better yet..unless doing competition is nothing....flew reasonably stable (no horizontal).. successfully recovered rocket..that is a successful launch. Rockets will weathercock into wind..all members have stated so...too much weight for engine...so not as high as you lile.