An "R"-powered rocket build

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Rail Dawg

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Rocket is set for a 10’ motor.

Got the back-up recovery system in place. (2) 1/2” Kevlar straps that are bulletproof-secured into the upper part of the booster. They will attach via quick links to the 3/4” eyebolt on top of the motor.

Still working on drogue section but now that the 10’ motor placement is locked in this section will be easy to finish.

AvBay will slide into upper part of drogue section and be secured with (8) 1/4” bolts. AvBay needs to be removable to access charge cannons for drogue.

Need to do these AvBay bolts for both ends but that should be pretty straightforward.

Still need to beef up fiberglass nosecone and install Delrin rail guides. After that get electronics installed onto AvBay sled.

Still some work to do but with LDRS 7 weeks away there’s plenty of time to finish with time to spare.

Got one Q motor to test and one to build.

Need to get some pics posted and will do so in the next few days.

Chuck C.
 

Ez2cDave

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Still some work to do but with LDRS 7 weeks away there’s plenty of time to finish with time to spare.

Got one Q motor to test and one to build.

Need to get some pics posted and will do so in the next few days.

Chuck C.
Chuck,

Don't fall into the "I have plenty of time" trap . . . Those 7 weeks will fly by, before you know it !

"From my chair" :

(1) Charge Cannons need to be tested.

(2) Nose cone must be reinforced.

(3) Install Rail Guides.

(4) Test Electronics.

(5) Make or purchase Recovery Harnesses. ( Take a look at "OneBadHawk" ) http://onebadhawk.com/index.html

(6) Attach Fin Can to Airframe securely.

(7) Priming, Painting, & Graphics.

(8) Motor Static Testing & Igniter Development /Testing.

(9) Verify CG with R Motor, Recovery Devices, and Electronics installed.

(10) Etc, Etc, Etc . . .

Something WILL come up, unexpectedly !

Dave F.

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Rail Dawg

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Scroll down about halfway on this page: https://www.multitronix.com/transmitter.html
It will show the dimensions of the Kate transmitter and a recommended mounting scheme.

A 54mm tube is usually run right down the middle of the nosecone. It is pushed into the inside tip of the nosecone as far as it will go and then secured at the bottom by a bulkhead across the aft end of the nosecone. A short length of 54mm coupler tube should then be inserted above the transmitter to bias the transmitter back away from the tip. If the tip is metal then it would be good to bias it back at least 3-4 inches from the metal. Another 54mm coupler is then cut to length as needed to rest against the aft bulkhead and yet push the transmitter as far forward as it will go. The Kate transmitter is 11.8" long so of course the overall tube length needs to be at least that. Usually the tube is much longer than that and the coupler tubes are sized to perfectly fit the transmitter between them. The transmitter has two centering rings on it that are 4.55" apart. That is the gap size you need between the two coupler tubes that will perfectly capture the transmitter between them. I usually just cut the lower coupler tube to length in the field with a Kate transmitter installed so that it works out perfectly.

Clear as mud?

Just to verify Vern since I’m getting to the nosecone soon.

Will install a 54mm tube probably more than 18” long that will butt up against the non-metal tip of the nosecone.

There will be a bulkplate of course that will have the 54mm tube capped at the bottom. I’ll bring some 54mm coupler that we can cut to length as needed.

Looks like that will cover our bases correct?

I appreciate your offer to run Miss Kate as I think this will be a real crowd-pleaser.

Although there is full confidence that the motor will perform beautifully perhaps we should design an escape rocket for the nosecone so Miss Kate can be safely carried away should something happen on the pad.

Ok that’s a poor attempt at humor lol.

Chuck C.
 

Flyfalcons

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Couldn’t you rest it on 2 scales - one on either side of the Cg? Wouldn’t the position of the Cg between the scales be the ratio of the weights?
Weight x Arm = Moment is a proven method to determine CG when using scales.
 

VernK

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Just to verify Vern since I’m getting to the nosecone soon.
Will install a 54mm tube probably more than 18” long that will butt up against the non-metal tip of the nosecone.
There will be a bulkplate of course that will have the 54mm tube capped at the bottom. I’ll bring some 54mm coupler that we can cut to length as needed. Looks like that will cover our bases correct?
Yes, that is exactly what we need. Perfect!
 

Ez2cDave

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With a few people and a sawhorse, it can be done by balancing.
The rocket has a liftoff weight of 700-800 lbs . . . Trying to balance it on a horizontal 2x4 of a sawhorse would be the "Kiss of Death" !

There would either be too much force concentrated in one small area of the airframe and the rocket would "snap in two" or the 2x4 of the sawhorse would break and drop the rocket to the ground.

Dave F.

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mperegrinefalcon

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The rocket has a liftoff weight of 700-800 lbs . . . Trying to balance it on a horizontal 2x4 of a sawhorse would be the "Kiss of Death" !

There would either be too much force concentrated in one small area of the airframe and the rocket would "snap in two" or the 2x4 of the sawhorse would break and drop the rocket to the ground.

Dave F.

View attachment 388644
Yeah, that would be bad. I didn't realize this was a 700-800 pound rocket, I thought maybe 200-300.

I think just placing it on two scales and calculating it would be the best.
 

Ez2cDave

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Sounds like a perfect test for the steely eyed missile men. Lol
Fortunately, for Chuck, the Steely-Eyed Missile Men are taking a serious look at the "logistics" of doing an "all-up" CG check.

Safety for those involved and the rocket itself are of primary concern.

At present, I'm looking at the possibility of using a "sling" to establish the CG.

Dave F.

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rcktnut

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I'd find a nice tree with a sturdy low branch, hook up a come-along to the branch and either assemble the rocket on the ground or appropriate amount of bucks put sling at approximate CG and crank it up a few inches. Adjust until CG is found.

I'll add or a joist or an engine puller, anything overhead that is capable of handling the weight.
 
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Ez2cDave

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Component CG analysis.

Determine the CG of the pieces, and determine the composite CG location.
That's an intriguing idea . . . Can you please provide more details, as I have never used that method ?

Thanks,

Dave F.

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Nytrunner

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The engineering team, whoever they are, should be abke to handle it.

Each piece of the rocket has its own weight (w) and its own CG at a location within that piece. Carefully record those weights and CGs.

When stacked together (on paper or real life), record the distance (x) of each piece's CG from the base of the rocket . Multiply each section's weight by its corresponding distance and Add them together (w1x1 + w2x2 + w3x3 + etc...)

Divide that sum by the total mass of the rocket, and the result is the CG of the whole thing (aka, the composite object)

Link below

http://hyperphysics.phy-astr.gsu.edu/hbase/cm.html
 

Ez2cDave

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The engineering team, whoever they are, should be abke to handle it.

Each piece of the rocket has its own weight (w) and its own CG at a location within that piece. Carefully record those weights and CGs.

When stacked together (on paper or real life), record the distance (x) of each piece's CG from the base of the rocket . Multiply each section's weight by its corresponding distance and Add them together (w1x1 + w2x2 + w3x3 + etc...)

Divide that sum by the total mass of the rocket, and the result is the CG of the whole thing (aka, the composite object)

Link below

http://hyperphysics.phy-astr.gsu.edu/hbase/cm.html
Thanks for the link !

Dave F.

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blackjack2564

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I'd find a nice tree with a sturdy low branch, hook up a come-along to the branch and either assemble the rocket on the ground or appropriate amount of bucks put sling at approximate CG and crank it up a few inches. Adjust until CG is found.

I'll add or a joist or an engine puller, anything overhead that is capable of handling the weight.
+1
how we did with a 675lb one. Used the hitch on truck to pull rocket a few inches above ground.
used 1inch TN.[4500lb rated] loop tied with bowline so it could slide into position. Simple and you KNOW exactly where CG is..no guessing with calculations.

Block & tackle would be even better.
 

fyrechaser

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+1
how we did with a 675lb one. Used the hitch on truck to pull rocket a few inches above ground.
used 1inch TN.[4500lb rated] loop tied with bowline so it could slide into position. Simple and you KNOW exactly where CG is..no guessing with calculations.

Block & tackle would be even better.
+2 Jim

In my humble opinion this method is the absolute best way to get an accurate CG location for a project this size. It can be done safely and quickly with a little preparation.
 

Ez2cDave

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+2 Jim

In my humble opinion this method is the absolute best way to get an accurate CG location for a project this size. It can be done safely and quickly with a little preparation.

To All,

Just so long as we don't try to "Swing Test" it . . . LOL !

Dave F.



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Theory

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+2 Jim

In my humble opinion this method is the absolute best way to get an accurate CG location for a project this size. It can be done safely and quickly with a little preparation.
X3 No replacement for real world numbers
 
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