First Time Questions

[Pippen]

Oh, that's no problem at all--it was above and beyond what we'd expected to do with it anyway. As I was trying to take enough dimensions to convey this fin I was wondering if it could be done.

The 4-H launch is Saturday--the site is a wide open space and I can take him early to test it before the crowd starts rolling in. Of course I want to do what we can in advance for safety purposes but if all doesn't go exactly right that's a learning experience too. I'm finding out that ten year old boys have a very different perspective on lawn darts, etc. than you big boys.

Any other ideas? I forgot to mention that when we let out the string long it was a nice even forward path.

 

[brianc]

Originally posted by Pippen
We loaded it back up this morning to double check it and on both trials (first by him, second by me) the same thing happened: the rocket started backwards and then after 2-3 revolutions it flipped forward and did an nice even nose forward flight. I did tape the string to hold it in place.

That's an example of minimum launch speed in action and perfectly normal.

What you witnessed is the speed required to make the fins effective. As long as your
selected motor can get the model up to that speed (and stable) quickly, it should be OK
off the rod.

If you're still a bit nervous, you can increase the length of your launch rod.

 

[cjl]

I'm fairly certain it can be simmed - give me a minute to mess around with this comp and see if I can get rocksim running (my sister is using the comp I normally use) and sim it for you...

 

[jraice]

if you figure it out PLEASE let me know how you did it... I would be very interested in anything rocksim related that I didnt already know how to do.

 

[brianc]

Originally posted by Pippen

Weight of rocket w/ everything but no motor = 2.4 ounces
...
Motor we plan on using – what’s easiest to find around here are A8-3, B6-4, and C6-5. We tested it on the C6-5.

The A8-3 has an initial weigh of 0.57 oz. which will push you very close to the
recommended maximum lift-off weight of 3.0 oz. I wouldn't suggest using this motor.

You should be good with either the B6-4 and C6-5.

BTW- here's where you can get the Estes motor chart- https://www.estesrockets.com/images/page 34.pdf

(showing Total Impulse, Time Delay, Maximum Liftoff Weight, Maximum Thrust,
Thrust Duration, Initial Weight and Propellant Weight for motors)

 

[brianc]

Originally posted by jraice
I cant find a way to make the fins get longer then the length where they attach to the airframe.

Select fin set from the rocket designer panel.
Then free form layout.
Click 'Edit fin plan' on the General tab.
Point, click, drag to your hearts content!
Just don't cross any lines.

 

[cjl]

Well, is this close enough?

I did the fins for this by a combination of the "plan points" and the "chamfer at selected point" controls (including the "show points" table).

CP for this is 14.8 inches from the tip of the nose cone (I didn't know what nose you used, so I guessed at a standard 4.35 inch long one).

 

[Pippen]

Yes, thanks, it's very close. The one difference I can see (and I don't know if it's significant) is that yours show the fin coming straight down while his continues a slight curve out and then back in towards the BT. The outer fin tip is about five degrees off from a straight down path.

 

[cjl]

Actually, mine does come back in a bit, so it sounds like it's good enough

Using the stated mass of 2.4 oz, I get the following results:

A8: 99 feet, 52mph, 10.76 gees, 2.07 second optimal delay
B4: 313 feet, 89mph, 13.90 gees, 3.72 second optimal delay
B6: 327 feet, 95mph, 13.41 gees, 3.92 second optimal delay
C6: 961 feet, 174mph, 14.81 gees, 6.19 second optimal delay
D13: 2339 feet, 356mph, 21.71 gees, 9.06 second optimal delay
D21: 2449 feet, 429mph, 34.21 gees, 9.66 second optimal delay
D24: 2394 feet, 411mph, 41.55 gees, 9.70 second optimal delay


That should give you a good idea of what to expect(I vote D13W )

 

[jraice]

well I was proved wrong... cjl... thanks for helping me/pippen out

 

[Pippen]

Originally posted by cjl
Actually, mine does come back in a bit, so it sounds like it's good enough

Must be ...er, the humidity distorting my vision. Yes that's it! We're blaming *everything* on the humidity around here this week.

Using the stated mass of 2.4 oz, I get the following results:

Cool! Thank you.

That should give you a good idea of what to expect(I vote D13W )

LOL, he'd probably have more fun launching with you.

 

[geof]

I just love this thread...a mom and a kid building rockets together! Pippen, you get a lot of points in my book for being a great role model.

Regarding motors, I think you understand that CJL was mostly kidding? The D13W needs a reload case and reload motors. I love the D13 to death, but its cost and power is not what you need in this case. Plus, you're unlikely to find this rocket after a D13 launch. Use the C6.

I'm looking forward to seeing the finished painted rocket, and a launch photo, and a photo of the triumphant kid holding his recovered rocket!

G

 

[Pippen]

Originally posted by geof
I just love this thread...a mom and a kid building rockets together! Pippen, you get a lot of points in my book for being a great role model.

Regarding motors, I think you understand that CJL was mostly kidding?

G

Long ago in a galaxy far far away (before my at-mom days, that is) I was a science teacher so this is a pleasure for me. My next undertaking is going to be getting the 4-H schedule changed so the fashion show and the rocket launch aren't happening at the same time. Harumph..grumble, grumble... way to encourage those girls...:kill:

I didn't know the specifics of that motor but I knew he was totally teasing. Thanks for being cautious just the same. I still plan to take him early so we can do a trial launch before the crowd arrives just to be on the safe side.

 

[cjl]

Yeah - I threw in the D sims as a joke, though the Aerotech D motors, especially the D13, have got to be some of my favorite motors for small rockets.

 

[Pippen]

We knew it would push 100 degrees with high humidity today so first thing this morning he masked off the fins by himself and we headed outside.

 

[Pippen]

I got one of those plastic can holders this year and it's been so much easier for the kids to control the can but it also has that weapon feel to it that my boys don't seem to be able to resist.

Let me tell you that you haven't lived dangerously until you've taken a kid out to spray paint a rocket.

 

[Pippen]

We had 'em inside to dry at about 6:30 pm and hope to do the fins tomorrow.

 

[jraice]

I have heard about those spray can lids, thinking about getting one actually. Wow, I know it is a simple paintjob but for someone his age, that looks very nice from the pics. I dont see any drips at all.

 

[Pippen]

I've been really pleased with how it helps--makes it easier to press the nozzle and is a lot less awkward.

As for the no drips--the gun helps but my husband figured out that a really good way to start painting with kids is to have them spray a mist straight out and then one of us holds the dowel with the rocket and moves it in and out of the mist. Otherwise they inevitably point the can at the rocket and shoot on a blob of paint. I think starting this way gives them a good feel for "keeping moving" and it doesn't take long until they tell me they want to move it themselves.

This morning I did the movement for the fins and then he did the up and down motions for painting the body tube while I rotated it a few rotations. It was really light around the launch lug and knowing we had to nail down this color today in sauna conditions I shot a quick mist to cover that. Painting is the best part of course, but not if it gets dragged out day after day after day...

 

[Pippen]

This morning he took off the mask and declared the yellow to be "Awesome!" then taped up to paint the fins gold. As I expected he wanted to move the can today so I talked him through order of what to paint before we headed out. I still held the dowel and rotated plus coached him ("Keep moving!!!!!!"). He was using a small can that doesn't fit into the gun and it was much harder to press down for him. He did great though--only one blob...which I quickly quizzed him how he felt about and ran for a paper towel to wipe off for him to respray the fin.

 

[jraice]

thats going to be a mean looking rocket!

 

[Pippen]

Originally posted by jraice
thats going to be a mean looking rocket!

You got that right!!!

Yesterday was touchup day. The gold paint on the fins wasn't too shimmery so I picked up a new can and he resprayed those in the morning and it's much better now. He had some spots that needed be touched up around the fin-BT junction so I just had him spray a little paint into a cup and take care of that with a small paintbrush--quick and easy. Here's how it looked yesterday before the touchups:

 

[Pippen]

I found flame decals at a hobby store that specialized in RC cars and he applied those this morning. This was one moment I wished you could have all seen: as he was applying them he was singing "Burn, baby, burn..disco inferno..." (which I found out today was the inspiration for the theme. My kids have been watching too much of Shrek 2 this summer...

 

[Pippen]

Since the flame decals are the most "Awesome!!!" part he wanted a close up of those. I'm sure you'll understand.

You can see how hot it's been here lately. Looks like it's melting already...or else the photographer was at fault.

 

[Pippen]

Here's my boy John checking out his finished rocket. He's done a super job and tomorrow he gets to see it launch. Stay tuned!

 

[timb]

Looking forward to seeing the pics of the launch! Good luck and have fun.

Can't wait 'till my 5-year girl takes an interest . . .

 

[Pippen]

We just got back from a great 4-H fair launch. There were about 30 kids who shot of a whole slew of rockets. We came early and got the first shot off after the test shot. Here it is on the launch pad next to his sister's Thing-a-ma-Jig:

 

[Pippen]

Oops, guess the Thing-a-ma-Jig wasn't there yet. You can see it here together with the moment we've all been waiting for...

 

[Pippen]

And getting it back from the recovery team after a PERFECT first flight!

 

[Pippen]

He let the friend he brought along fly it next since the repair we did on his Fatboy didn't turn out as hoped. It launched great again but this time the parachute didn't fully unravel. Even so it had a pretty easy glide down but we were sweating it out when the recovery team didn't bring it back on their next round. They persevered however and brought it back in one piece. Several of the scratch builds that flew today didn't fare nearly as well with some leaving pieces behind at the launch pad so he felt fortunate.

Some pictures need no explanation: