Extreme Air Mail! Mailing Tube Rocket Project!

Weldo said:
I'm not sure I want to go so far as doing fiberglass. I don't really know much about the whole process.

What's a recommended lightweight sealer? You mentioned Evercoat earlier, is that like a filler primer or like a body putty?
Click to expand...
sigmfg.com

SIG SANDING SEALER

Butyrate Dope Based Primer Creates an ultra-smooth base for a prize winning butyrate dope finish. Quickly fills wood grain and covering materials. Sanding Sealer is our Lite-Coat low-shrink butyrate dope with special lightweight, easy to sand fillers added that make it the perfect surface primer...
sigmfg.com sigmfg.com

lightweight, made for balsa.
 
I just about completed my rocket, just waiting to pick up a 1/4" round for a launch rod before I decide which launch lugs to use. The total weight with parachute and motor is 511 grams or 18.01 ounces. It's a little heavier than the OpenRocket estimate of 17.1 and I still want to make a Nomex chute protector!

Also I made an account over on the Rocketry Forum just to get some more insights on my proposed flight. Everyone over there says my off the rod launch speed is way too slow to be safe at 25 ft/s. They say the minimum recommended is 50 ft/s with 40 being absolute lowest. I can achieve between 40 and 50 by sizing up the motor to an E30 or above but then the apogee climbs to over 500 feet. While that may be impressive, it's not my goal for this flight.

In an effort to gain some more launch rod speed I'm gonna size up the rod to 72" long. This will ensure my vehicle is traveling a little faster by the tie it leaves the guidance of the launch rod. With a 72" rod my launch rod speed will be around 30 ft/s. I believe this to be acceptable as long as the winds are very calm to completely still at ground level at the time of launch.

Looking through some NAR documentation, the only thing I could find in relation to off the rod speed was that NAR says that by the time the rocket leaves the guiding influence of the rod it should be traveling 4 times the highest observed wind speed at the launch site. For my launch, 30 ft/s equals 20 mph so I could launch in 5 mph winds safely. Based on what I've read...
 
I do not want to advise you to do anything dangerous. I will just say that I used to launch my low and slow rocket WITHOUT a launch rod with calm winds. My rocket was longer than yours at about 40" though.
Robert
 
Ya know I wondered about that. Really you shouldn't even need a launch rod. If everything on the rocket is very closely concentric it should take off vertically as long as there is little to no wind.

It seems to me the launch rod is there to make sure that, if there is wind, it will not influence the rocket until the rocket is traveling fast enough to become stable in that wind.

I feel pretty confidant that my rocket is well made concentrically. I plan to use a longer launch rod to be safe. And on launch day I'll likely set ip up and wait as long as I feel comfortable for a lull in the wind.

I don't want to do anything unsafe either.
 
A launch rod is dramatically safer, I just would not get too caught up in the launch speed for a long stable rocket.
Still, it is fun to know the theory and do the math. I learned something.
R
 
Right on.

I got kinda nervous after hearing some of the other opinions on Rocketry Forum but I still want to try this with a D12. My ideal flight plan is aslow and dramatic lift off, apogee at about 100 feet and the chute deploys and inflates about 30 feet from the ground. It may not be a typical launch plan but I think it'll be fun to watch!

Regarding launch speed, I'd like to compare some known models with known engines and see what they're launching speed is. For example every Estes model recommends the first launch for a model to be with the lowest power engine possible. I got a Nike-X kit from them and it says first launch ought to be with an A8-3. The two others are B6 and C6. Obviously the A8 is gonna have a slower launch speed but it must still be safe.

Also I built the Mercury Redstone Estes kit and it takes a C6-3. It's the only recommended motor. But the package says it provides a "Slow and realistic lift off". Someone over on the other forum said they thought they heard the launch speed of that kit was somewhere around 26 ft/s. That's very slow from what I understand. The Estes instructions say to only launch in very calm winds though, and this may be why.

I don't know, I feel like the best way to learn is through experience so I'll likely end up trying a launch. Even NASA had lots of hiccups at the beginning.
 
Haha don't worry! When I finally go out to launch there will be vid!
 
You must log in or register to reply here.
Back
Top