posted weights of kit rockets?
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dave carver
....what hump?
It's always looked to me to be ballpark guesstimations...sometimes the guesses are out of the ballpark
Maybe they should have a range posted from light to heavy expected weights based on construction parameters. For sure the amount of whatever adhesives you use can be critical. Wither you fiberglass and how much. Company that makes the chute can be a difference in weight. I ignore the suggested weights as because you have noticed they hardly ever coincide with finished product. I have a gram scale I got just for weighing rockets to match with motors and delays. Just easier to go to a chart I have mostly memorized.
DavieRockets
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You are not alone! I used to think I was building "heavy". Then I bought Rocksim, started weighing components and realized how far off some of the published weights were. In some cases the raw kit parts were only a couple ounces less than the published weight. Also remember that published weights usually don't include avionics and associated things like charge cups.
Now before commiting to a kit, I get the rocksim file add all the components I think I will install, add weighed chutes, shock cord, eyebolts, epoxy, paint (you may be surprised how much paint, primer and filler add) and then determine if this all meets my needs. Then again, if I really love a kit, I'll just buy it and build it! :smile:
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enderw88
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I am building a thin-wall fiberglass mini-DX3 and keeping very close track of weight at every step of construction. I am not really concerned about weight for this, but I want to see what my building style does. I weighed each piece individually before I started and found I had 336 grams of components which left 32g to get it completed at the published mass of 368g. I think I will get it pretty close.
blackjack2564
Crazy Jim's Gone Banana's
Most high power kits....weights that are supplied, are for total sum of parts.
By the time you add in epoxy, threaded rod, eyebolts, chutes ,nomex, altimeters [1or 2] batteries [1-2] sled, of course it's going to be heavier.
Then take into consideration the different styles of building, some use U-bolts which are heavier than eyebolts, some glue recovery harness to MM tube, others put eyebolts on CR's. Then you have fillets sizes, etc.etc.
Most kits I have done for Wildman I state the parts weight and finished built weight with just 1 altimeter set up, but ready to fly most builders seen to come pretty darn close.
Built weight on 3-4 in. kits seems to be 1.5-2llbs heavier than parts weight.
I can't speak for other brands though.
By the time you add in epoxy, threaded rod, eyebolts, chutes ,nomex, altimeters [1or 2] batteries [1-2] sled, of course it's going to be heavier.
Then take into consideration the different styles of building, some use U-bolts which are heavier than eyebolts, some glue recovery harness to MM tube, others put eyebolts on CR's. Then you have fillets sizes, etc.etc.
Most kits I have done for Wildman I state the parts weight and finished built weight with just 1 altimeter set up, but ready to fly most builders seen to come pretty darn close.
Built weight on 3-4 in. kits seems to be 1.5-2llbs heavier than parts weight.
I can't speak for other brands though.
o1d_dude
'I battle gravity'
This has been my experience with just about every brand of kit I've built.
Kinda like the Pirate's Code: "...more like guidelines anyway."
markkoelsch
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A CJ said, it is just the weight of the parts. Add hardware, epoxy, avionics, and paint. The paint can be significant weight...more than you might think.
Best route I think is to build and initial sim weighing the parts. Start building the actual rocket and keep track of epoxy weight, and update the sim. Finish the rocket sans paint and weigh the whole rocket then compare its real weight to the sim. It should be on assuming you weighed everything and added it to the sim.
Then paint the rocket, and weigh it. Take the difference between finished rocket and pre paint weight to determine the paint weight. Update the sim by adding a mass object equal in weight to the paint at the rockets Cg. Update the sim's surface definition to match the smoothness of the finish.
For some that is too much, but if you want accurate sims the more complete and accurate you are the better off you will be.
Best route I think is to build and initial sim weighing the parts. Start building the actual rocket and keep track of epoxy weight, and update the sim. Finish the rocket sans paint and weigh the whole rocket then compare its real weight to the sim. It should be on assuming you weighed everything and added it to the sim.
Then paint the rocket, and weigh it. Take the difference between finished rocket and pre paint weight to determine the paint weight. Update the sim by adding a mass object equal in weight to the paint at the rockets Cg. Update the sim's surface definition to match the smoothness of the finish.
For some that is too much, but if you want accurate sims the more complete and accurate you are the better off you will be.
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