Low altitude???

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Ok, ran a simulation with the F40-W7..it shows motor burnout around 350 ft +/-. If I had I faulty or early ejection event, that would account for the altitude loss, yes? On assembling the delay/ejection set up, I put the small thick o ring in the delay well, then the delay grain in the tube with the spacer on the bottom of tube (facing fuel grain) then the big, thin oring on then insulator disc. I did put one layer of masking tape over forward end of fuel grain. Is is possible I didn't get the tape on securely enough, and the igniter dislodged it? Does my assembly procedure seem correct? I'm now thinking it was more delay foul up than motor failure. But I am new to this...rsbhunter
That sounds right and if the rocket was still going up and flying sorta fast it does sound like an early ejection as @rcktnut said ...

Here is a pic cropped from RCS > AeroTech & Industrial Solid Propulsion (ISP) Resources > RMS-29/40-120 Model Rocket Reloadable Motor Instructions > E16W-F40W Instructions ( attached below ):

rms_29_e16-g64_4-04_1642627189854-delay.png
The small piece of tape on the fwd grain is only there to keep the ignitor next to the top of the most forward propellant grain -- if the motor lit fthen no problem with the tape.

As @tsmith1315 said, do check your CD !

The only other thing I could think to check is your scale ?

I dropped mine on the driveway on the way to TXSO last month and it lost it's mind -- everything weighed 1999 grams after that event !

All self-respecting texicans and new mexicans should have one-or-more bags of pintos on hand at all times (*) :)

How much does a 1-lb bag of beans weigh on your scale ?

One bag from our cabinet weighs 465 grams / 1.02 lbs / 16.4 oz, so my new scale seems to be OK ...

Is your scale in the ball park ?

A penny weighs 2.5 grams and a nickel is 5 grams ...

On the low end, how much do a few pennies or nickels weigh ?

And if you drop them on the scale, one at a time, does the scale scale ?

After all this ...

I like your idea -- fly another F40W and then try a G64W on a nice day !

-- kjh

(*) - a cajun on the other hand will have bags of rice and red beans but they may be larger than one pound each :) :)
 

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No, my scale "should be accurate" . I've always keep it covered, and it's never been dropped. I do have a bunch of stuff I can check it with. I have 2 50 gram check weights I can use, that I calibrate my reloading scale with. The scale shows 50 grams, each, 100 for both....it's on as far as I can see. Rocket shows 25.7oz / 730 g.. so I'm thinking the scale is ok? The insert you show is the one I loaded the motor with...maybe it was just a fluke first time flight? I really appreciate the help and suggestions, there's always a chance that we will assume something is right, just to be found out wrong...I normally go the other way, obsess over having it "perfect". Makes finishing rockets a real treat!!!!!! Cause they are never perfect. Thank you for taking the time to help me...rsbhunter
 
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Alot of my other hobby involves measuring to within 1/10 of a grain. And some guys have scales that go to .001 of a grain. So I have a tendency to keep strict tolerances. And being new to mpr, I like to stay within a tolerance range that seems reasonable. So, what is reasonable in the weight range of a rocket? 5 grams, 1 oz. ? I have never seen an acceptable range , but will believe what the concensus here states....I also would like a concensus on the rocket weight to Ns or lbs thrust...some say minimum 5x, others 8, or 10x. I'll take all the knowledge given. Thanks, rsbhunter
 
In today's market a scale that *reads* to the nearest gram is rarely precise or accurate to the nearest gram. It will float up and down. A little float is normal. But for the best accuracy and precision, get a scale that has the highest capacity that might be needed, with a readout that has one decimal place more than you expect to need. Example: I need to weigh 2 kg to the nearest gram, buy a scale with the largest possible capacity that reads to 0.1g.

Scales are so cheap that I bought two for the kitchen, a 500g +-0.01g and a 44 kg unit good to a gram. And two for rocketry, long ago: 7 kg +-0.1g and 500g +-0.01g.
 
In today's market a scale that *reads* to the nearest gram is rarely precise or accurate to the nearest gram. It will float up and down. A little float is normal. But for the best accuracy and precision, get a scale that has the highest capacity that might be needed, with a readout that has one decimal place more than you expect to need. Example: I need to weigh 2 kg to the nearest gram, buy a scale with the largest possible capacity that reads to 0.1g.

Scales are so cheap that I bought two for the kitchen, a 500g +-0.01g and a 44 kg unit good to a gram. And two for rocketry, long ago: 7 kg +-0.1g and 500g +-0.01g.
Yep, time to shop!!!!
 
Congratulations on your flight. A couple questions: how did you secure the altimeter in the payload bay? What was the total flight time recorded by the altimeter?
 
I had added a piece of all thread , threaded into the hole in the nose cone. I double nutted the all thread with a loop of 300lb test kevlar line. The Jolly logic was looped through that. The #'s are apogee 419' top speed 120mph, burn time 2.54, coast to apogee time 2.3,apogee to eject ‐2.2 , ejection altitude 271', flight duration 28.9. Jl chute release set for 300', 30" chute. 0-2 mph wind , 80° , about 6:15 am...
 
Should I put tissue or a piece of foam inside to cushion the JL altimeter? Was afraid it would alter the reading, so I just let it bounce around...
1000048921.jpg
 
So, what is reasonable in the weight range of a rocket? 5 grams, 1 oz. ? I have never seen an acceptable range , but will believe what the concensus here states....I also would like a concensus on the rocket

Something to keep in mind is the acceptable variation in motor impulse, thrust and delay.

Here’s the tolerance allowed during the NAR/TMT motor certification process. Any motor performing within these tolerances is considered to be within spec.

A583EDB2-A60D-494A-8BE6-6508DB514F0A.jpeg

Source:
https://www.thrustcurve.org/info/certification.html

This may help in deciding how small of a nit you want to pick. And that’s largely a personal preference.

One of the things I love about this hobby is the variety in how you can choose to participate. You can design, analyze and build to the limits of your abilities, or with some experience, you can build and/or fly by principles of TLAR.
 
I honestly don't want to nit pick anything, I had thought I had screwed up building the rocket, and made it way to heavy. I picked this engine because I wanted a "middle of the road" flight. High enough to get ejection and watch it fly(stable, straight) . I knew the flight wasn't close to 900', because I have lpr's that go to that altitude. I'm going to run with Titan II and go with a motor problem!!!!
 
I would use a little masking tape or rubber bands to secure the altimeter. Having it flopping around can cause some erratic data. This is more of a problem for accelerometer or G data.

Looking at the thrust curve and weight of the rocket your at 3.25:1 thrust to weight. A 8' rail is pretty long, how was the launch pad setup and fin orientation vs wind direction? Did the rail buttons look like they were dragging on the way up?
 
There was almost no wind 2-4mph. Didn't appear to drag on the rail...I lube the rail and buttons with dry hbn, a powder lubricant. I did order a 6' stick of 1010 rail, although I can move my stop as high as needed...thinking about having about 5' usable rail on next launch..? Thanks for helping....rsbhunter
 
My DX3 weighs about 18 oz (about half what yours does?) and gets to 900-950 feet on an F40. Thrustcurve says more like 1200 feet. I've often suspected that the total impulse of current production F40s is lower than the certification value.
 
Scales for reloading smokeless powder for the other hobby mentioned and scales for rockets are best to be separate items.
The Max weight you plan to measure is an order of magnitude different.
 
My "other" scale doesn't come close to having the capacity for weighing rockets...and for the cost of it, it isn't worth it. Having 15' of 1/4" kevlar cord, 30" chute, 9" square blast protector, as well as JL chute release and altimiter add to the weight. I'm ordering some reloads, one is a G64-7. That ought to get me to 8-9 hundred feet. Plenty for fun launching..rsbhunter
 
There was almost no wind 2-4mph. Didn't appear to drag on the rail...I lube the rail and buttons with dry hbn, a powder lubricant. I did order a 6' stick of 1010 rail, although I can move my stop as high as needed...thinking about having about 5' usable rail on next launch..? Thanks for helping....rsbhunter
Interesting !

I've never tried dry hexagonal boron nitride ( aka dry HBN ) on my personal 2020 rail.

I've got some around here somewhere and I'll try it out ...

Thanks for the Tip, @rsbhunter !

-- kjh( :) slick rails is good rails :) )
 
Interesting !

I've never tried dry hexagonal boron nitride ( aka dry HBN ) on my 2020 rail.

I've got some around here somewhere and I'll try it out ...

Thanks for the Tip, @rsbhunter !

-- kjh
I keep hbn in a small bottle mixed with 99% isopropyl alcohol to lube case necks, and vibrate projectiles in a jar with hbn and bb's.. hbn is some slick (literary) stuff. Plus has off the chart temp. resistance....has ALOT of uses....rsbhunter
 
I'm ordering some reloads, one is a G64-7. That ought to get me to 8-9 hundred feet. Plenty for fun launching..rsbhunter
You better order a couple of them, my favorite MPR motor. Also go by what your sim is telling you for altitude, don't assume how high it might go. I have a 4" dia. MPR rocket (Big Brute- much shorter than yours) that weighs 33oz. with the G64 in it and it sims at almost 1400 ft. and it's flights look close to that alt. I simed your rocket with a weight of 25.7 oz. w/o motor and it sims 1350 to 1400 ft also.
 
You better order a couple of them, my favorite MPR motor. Also go by what your sim is telling you for altitude, don't assume how high it might go. I have a 4" dia. MPR rocket (Big Brute- much shorter than yours) that weighs 33oz. with the G64 in it and it sims at almost 1400 ft. and it's flights look close to that alt. I simed your rocket with a weight of 25.7 oz. w/o motor and it sims 1350 to 1400 ft also.
I am ordering a couple ( at least). I have one more F40-7W to try, and unless it goes higher than 400', I'm moving on to the G64's...and will try others... what I don't understand is in OR ( and I'm not real good with OR yet) that it shows my correct weight I entered, with and with out motor, and sims to 911' with F40. Now, I am more than willing to accept options that I screwed up something, or maybe a weak reload, etc. Getting to the point where, upping the load is the best option. IF the next F40 does the same thing....we shall see....rsbhunter
 
I am ordering a couple ( at least). I have one more F40-7W to try, and unless it goes higher than 400', I'm moving on to the G64's...and will try others... what I don't understand is in OR ( and I'm not real good with OR yet) that it shows my correct weight I entered, with and with out motor, and sims to 911' with F40. Now, I am more than willing to accept options that I screwed up something, or maybe a weak reload, etc. Getting to the point where, upping the load is the best option. IF the next F40 does the same thing....we shall see....rsbhunter

Make sure to let us know.
 
My guess is (and forgive me if I'm barking up the wrong tree) is that the red nozzle cap was placed on too tight.

1718476891512.png

This happened to me with a G80 in my Mega Teal Max. The first attempt was with a DMS motor, but Jake's Mega Red Max chuffed. He wanted to fly both again so lent me a RMS G80 with case. In my haste, I put the nozzle cap on all the way without notching the end. Afterwards, the red ring was left on the nozzle and the rest had melted away.

The first flight was 644ft. Not sure what the altitude was for the second flight because the altimeter broke off, but it was definitely less than Jake's. Probably went 400ft and barely ejected in time.

 
I will report back when I launch again, might be in the morning (fathers day) depending on wind. As to the red cap, I slit it about 1/8" wide to the bottom, and removed the slit part. I also found the cap on the ground. Besides having a little soot(?) on it, I could have used it again...luckily, there was no chuffing, I heard the igniter puff, then full smoke and sound...I was expecting a normal flight, 800-900 feet. But, tomorrow is another day, maybe the wind gods will be kind....rsbhunter
 
Not sure this is helpful but.. I have assisted in building and flying around 100 DX3 as part of a Jr. Level One program. the 'gold standard' build was 713 grams with an H135 and 710 grams with a H115, weight ready to fly including motor.

We added nose weight for the H motors, yes you should too. The final altitude with a H135 was 3663' and with the H115 2824' .
 

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