Getting there...(new project)

Jul 19, 2004 10 Replies
G

I completed the aft section and electronics bay on my "new" 4" rocket. The



47.625" long aft - which'll hold a 75mm 8000N-s case - weighed in at 3 pounds! wooHOO!!!

I'm gambling the entire rocket may weigh as little as 7 pounds ready-to-fly sans motor case. That bad girl'll go 5600' on a J800, 9800' on an L2000 (EX) @ M1.25 and - the piéce d' resistance - 850' on an H268R. :-)>



May not seem like much of an achievement but for me - a card-carrying member of Overbuilders Anonymous - it's an epiphany.



I'll post some nekkid pics in the next couple days. Ummmm.... of the rocket, not of me.... :-)>


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J

ROFL

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C

LOL! I should start all of my posts with, "Hi, my name is Chuck, and I'm an epoxiholic."

My most recent 5.5" creation, a 1.2x Upscale ARCAS,

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came in at 14 lbs (no motor), which is much better than its predecessor, the Rapier (God, rest its soul) which was packing about 4 lbs of nose weight added to the grossly overheavy airframe,
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cp BTW, Gene, thanks for scaring the heck out of me for my inadvertent foray into the 'good' section of the Bronx! :-)

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G

Just doin' my job, Chuck... :-)>

If it was daylight, you had no problem; to coin a phrase, "they only come out at night"...

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R

Gene, Its not too late to add some all-thread.

ready-to-fly

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G

My rocket is almost complete (some details) and ready-to-fly weight sans motivator is 8.3 pounds, including twin RRC²s. I MAY cut the aft about 8" shorter and the fore section about 2". That would bring the overall length to ~77½". I don't like high aspect ratios but I don't like nose weight either. The buzzword on this project was LIGHT.

I'm going to come in under 8 pounds but I'll still be able to fly it on a

6000N-s M. Naturally, I'll still be able to fly it on an H :-)>

I'm thinking chrome (painted) fin tips with a dark metallic grey and black paint scheme. Kinda Van Goghesque.

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D

You can cut more weight than that if you replace al the steel hardware with

6AL4V Ti alloy. I have a bunch here and you would be amazed how light it is. Not only is it ~40% lighter, you can go with sizes that are less than 1/2 as thick/large because it is so much stronger than the junk steel that we use.

Of course, that's only if you are really serious about making it light. ;-)

Doc

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J

Doc, where did you find the Ti hardware?? I WANT SOME! :)

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D

McMaster Carr is a good place. 6Al 4V Ti is also known as "Grade 5 Titanium" Do a search on Titanium. Some of the good stuff is in the "Titanium - other" type of category. They have nuts, bolts, all-thread, plate, strip, bar, eye-bolts and all kinds of stuff.

1/8 Ti 6AL4V all thread can replace 1/4-20 all thread and will weigh only a few grams. (I'm playing with an 8" long 1/8 Ti all thread right now and I can hardly tell I have it in my hand.)

You can replace about 5 pounds of typical HPR hardware with about 8 or 10 oz of Ti. Remember, the "junk steel" hardware has about 24ksi yield strength.

6AL4V Titanium has a yield strength of at least 60ksi, (Usually closer to 90ksi).

Have fun!

Doc

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