Yikes!!! My Mirage may not fly!

Also, I noticed you mentioned launching on a G load. DO NOT risk crashing your rocket because it was underpowered; it's not worth it. I have listed below the guidelines for choosing the correct motor.

First, figure out the thrust, in pounds, of your motor:

A <B>G64W</B> is a <B>White Lightning</B> load <B>with 64ns</B> of thrust

NS thrust / 4.45 = Pounds of Thrust

<B>64</B> / 4.45 = <B>14.38 lbs</B> of thrust

Now, you want <B>AT LEAST a 5 to 1 thrust ratio</B>, so do the following:

<B>14.38 lbs</B> / 5 = <B>2.88 lbs</B>

<B>2.8 lbs</B> is the <B>HEAVIEST</B> rocket you want to launch on a <B>G64W</B>

The <B>weight</B> (2.8 lbs) <B>INCLUDES the weight of the Rocket WITH Motor</B>

use this method for accurately calculating whether or not a motor is enough. Also follow these guidelines:

The calculations work well on a White Lightning Motor

For a Blue Thunder Motor, <B>Less thrust could work</B>, possibly 55-60ns, since the motor has much more thrust at ignition, then tapers off quickly

For a Black Jack Motor, use a motor that is <B>AT LEAST 1 1/2 times the thrust of a White Lightning</B> to be safe. For example, if you use a <B>G64W</B>, you would want AT LEAST a <B>G96J</B> for a Black Jack. This motor has a SLOW, gradually building thrust curve and, in order to get safe velocity off the pad, you need to increase the NS of the motor.

*****
If you want a ballpark figure whether a motor qualifies, Use the quick Field Method I use on the fly. Take your motor's <B>Average Thrust and DIVIDE by 25</B>!! It's a little rougher than the accurate formula listed above, but you can do it quickly in your head without a caculator.

EG: <B>G64W........64 / 25 = 2.56</B>.........Your safe <B>rocket weight with motor</B> should not exceed <B>2.56</B> pounds; a ballpark compared to the accurate 2.88 with some extra fudge in there for safety!

Cya,

Carl

It's easy to figure in your head. Here is how I do it(yes, I am warped)....

<B>64/100 = .64...... x 4 = 2.56...now the secrets out, you know how I do my brain math! Sick, huh???</B>

What's worse is...<B>YES</B>...I keep all this **** in my head...Spooky as hell !!! (For Ken's benefit! )

If I drop a bunch of toothpicks on the floor, can you tell me how many are there?

I'm now curled up in a fetal ball whimpering and sucking my thumb. Muttering, "Ive seen the inside of Carl's head. I've seen the inside of Carl's head. Help me Mommy."

I'm gonna weigh the rocket tonight and try to figure out the changes in mass. Electrode is gonna do a Rock-Sim for me to let me know if this weekend is gonna be good or bad.

CRUD!!! I didn't think this far ahead. I wanted to test it and what better to test it with than the suggested largest engine: a G. 2.5 lbs huh? CRAP!!! Lessons learned... I bet it's too heavy...

Make sure you weigh it WITH the RMS case and reload added to the scale to get total pad weight.

Sorry for the news, but wou'ld ya rather see it crawl off the pad, just to nose over and create yet another gopher hole?

A G80W Single Use is the largest thrust motor you can currently purchase. I wouldn't use it on a rocket that weighs more than 3 lbs, just for safety.....Remember...INCLUDE the motor weight.

Cya

BTW: GOOD one's Guys...LMAO!

Good news/bad news. First the good news: My flare which consisted in one blue stripe came out perfectly. The bad news: The rocket pad weight will be 3 lbs when done. I still have about 3 coats of clear to go to finish it. How close is 2.88 to 3? Yikes!!! I still feel comfortable launching it on a G. Anyone else have a different opinion?

How about that? "Fear not" as opposed to "Fear This." Although, I'm partial to the redneck version "Ain't Skeered." But I digress.....

Phil, sorry that you had to be exposed to the inside of Carl's head. If it's any consolation, the outside ain't all that great either. (Sorry, Carl..... it was too easy)

Anyway..... if you need a G80, it just so happens that I have TWO of them. Courtesy, believe it or don't..... of Mr. Tulanko. I might even donate one this weekend just to see the dang thing fly. But I will be surprised if it's THAT heavy. BTW, don't know if I had them out while you were here, but I have two scales. One will weigh in either grams or ounces, but only goes up to about three pounds. The other is actually a fish weighing scale, goes to 15 pounds by ounces. Let me know if you want me to bring them on Saturday. Actually.... I will probably bring them anyway.

Oooohhhh.... just thought of something.... I think the delay on the G80's I have is 10 seconds.... way too long for the modified Mirage...... rats..... have to rethink this.....

I borrowed the Cub Scout scales, both measure up to about 300 oz. I measured on both scales which seemed to be .1 different, so I took the smaller number. These are mail scales. Are you saying that the 64 ain't gonna do it?

Thanks for the offer on the 80s.

The G80 should work fine thrust-wise. It's just that it's a single use motor and it has a 10-second delay. Being single use, I can't get to the delay to modify it.... And if your rocket is pushing the weight limit, it probably needs a 4 second delay. You might get away with a 7 second..... but 10 second.... probably be zipper-city. Given all the time and money you've spent on it, I don't think you want that.

They sell the reloadables for G75J and G104T. Course it doesn't mention the delay, it just says S, M, or L. I will ask what that means in the propulsion forum. Those motors require the 180ns case which I don't have yet.

I'm still waiting for Electrode to key everything into Rocket Sim and tell me what the 64 is gonna do.

Doesn't look like the Mirage is gonna fly this weekend.

I bought the AT G64-4W for testing my Mirage. Now I'm afraid I made the Mirage too heavy. CRUD!!!

For those of you just tuning in... This thread was split from another thread but did not have the desired results. This thread was started originally by me with the below post. Sorry for the confusion.

I bought the AT G64-4W for testing my Mirage. Now I'm afraid I made the Mirage too heavy. CRUD!!!

Click to expand...

The G104T has the thrust you would need to get it off the pad, however, it uses a 29/100 case, which is only good for two different reloads; kind of a waste to buy IMHO, especially for a single launch. Also, you won't get much in the way of altitude, since the motor burn time is less than 1 second.

I would wait for Whitakers...

Make sure you call Ken Allen of Performance Hobbies and have him bring the cert motor you want to the launch. You may even want to get two for the fun of it.

Carl

Well, the preliminaries are in from Rock-Sim. (Thanks Electrode) Based on the weight and a CG of 65" (which I need to verify) my Mirage should leave the pad at 41 fps and go 958 ft which makes me very happy. More once I verify the results....

And the results you quoted are based on what engine? G64? G104? ?????

Sorry. The 64. Optimal delay was 6.44 seconds so the 4 second delay should be fine.

BTW: I received my Dr. Rocket casings today. Man, they are so sexy!

A G64...for a 3lb+ rocket...??? And 41fps is marginal...you can decide from there...but I don't wanna hear any crying after this weekend while you are rebuilding.

You will get away with it IF you are lucky, which reminds me of something...


"Now, did I load a 64...or a 104...to tell ya the truth, in all the excitement, I forgot. So, what you have to ask yourself is... "

"Do you fell lucky?"

"Well, DO YA?...P _ _ _ ???!!!"


Carl

I just watched Challenger: Final Voyage. I think you should listen to the engineers on this one and don't rush it. Think of all that hard work. Wait until you have the right power dude.

Well, what is the worse thing that can happen? The rocket is distroyed and I can't cert at Whitakers the 22nd? The paint job looks like crap anyway. What the heck - I'll just buy another one and make it better, faster, and stronger. I have the tools, and now the technology. I'm feeling lucky... Jack, I'd like to spin again....

ok here is the rock-sim results........
G64w... optimal delay (6.11), 41 ft./s off a 6 ft. rod to an alt. of 894 ft.
H128w... optimal delay (7.75), 59 ft./s off a 6 ft. rod to an alt. of 1,354 ft.
H238T.... optimal delay (8.5), 80 ft./s off a 6 ft. rod to an alt. of 1,497 ft.

I would say your safe with all the flights.... I did the sim with a 5mph wind.. up here in the mid-west it's hard to get a windless day. 41 ft/s is a fine for stabilty.

Tim Hansford
NAR 78513 SR L2

OK, I've decided to go ahead and try. The Mirage will liftoff (crossing fingers) with a G on Saturday. I feel confident that it will fly. (thanks Electrode) I should have pictures, happy or sad, by Sunday.

Last words of a white collar redneck: "OK, I've decided to go ahead and try."

Flying rockets ain't like dusting crops boy! Without precise calculations you might fly too close to a star or bounce too close to a supernova and that would end your trip real quick.



My worry is what your wife will think. You go and destroy a $200 bird on the first flight and she is going to start questioning your expense reports and your ROI.

That would be true if she thought the bird cost $200. Those things depreciate rather quickly once you order them. Buy the time the rocket reached my house, it was already down to $50.

lol.... I don't have a wife anymore to complain.. but I do have a mom... even though I haven't lived at home in over10 yrs... I still hear it all the time... lol. gotta watch what I say and use words like.. wow it was on sale.. or I got it for 1/2 price... and if the price get's brought up.. it's a change of the subject really quick.. Hmm you should see what your grand daughter did in school today.. lol

I suppose if you trickle in the supplies she may not notice as much. Easier to fool that way. Deep down she knows though, she is adding it up. Waiting until she has enough to go get that big ticket item.

Craft plywood, 20 cans of paint, epoxy, sandpaper, motor casings, motor mounts, countless hours of time.... the list just goes on and on.

Can't wait until Saturday... "Hey Bubba, watch this." (No white color rednecks here, just plain red.)

Phil,
Can't wait to see the Mirage on Saturday. I will have my camera ready. I have faith in you.

Thank you Ms. Shutterbug. At least someone, sniff, cares for me.

And it was 70 cans of paint Milo!

Well folks, she flew. The two parachutes got tangled so I will have to figure out how to keep that from happening. And it seemed to go alot higher than the 900ft that Rocksim predicted. But, it was a beautiful launch and I had my heart in my throught (sp?) until I had the Mirage back in my hands.

Thanks to everyone for all the help and kind words that you gave me. Now off to Whitakers and Level 1!!!

throat

Pffft! I knew that....

Good job Phil! I would have been hesitant myself, but eat my words. Then again, I tend to make sure there is always extra power; you'll see when the A2 goes up on a H128W at Whitakers!

Regarding the 70 cans of paint, the student has become the master! I am proud of you!!!!

Carl