Do you send it?

[MarsLander]

Do you send it on a K695R?

Mass and CG measured and overridden in Rocksim. Nose/motor deploy, JLCR, about 5,000 feet. .125 G10 fins, ttw, jbweld fin to MMT, west six10 internal and external fillets. Thrust plate and flanged retainer. Build link in my signature.

 

[Hobie1dog]

should be stable at 1.46 and up, why do you question it?

 

[jmasterj]

Are you using motor deploy?

 

[MarsLander]

should be stable at 1.46 and up, why do you question it?

The important thing is to not stop questioning. Curiosity has its own reason for existing.”
- Albert Einstein

 

[MarsLander]

Are you using motor deploy?

Yep.

 

[Titan II]

The important thing is to not stop questioning. Curiosity has its own reason for existing.”

You neglected to complete the quote. It is not even remotely applicable in this case.

“The important thing is not to stop questioning. Curiosity has its own reason for existing. One cannot help but be in awe when one contemplates the mysteries of eternity, of life, of the marvelous structure of reality. It is enough if one tries to comprehend only a little of this mystery every day.”

BTW...Your question has an obvious answer.

 

[3stoogesrocketry]

What are your lower fins made from?

 

[ljwilley]

I would fly it, but not above 10mph winds.

 

[jsdemar]

What are your lower fins made from?

This ^^^
And how are they attached?

Also, the point masses for the recovery gear in the simulation will move aft during liftoff, reducing the stability margin. Add a stuffer tube and/or nose weight.

 

[MarsLander]

What are your lower fins made from?

.125 G10

And how are they attached?

TTW, internal and external fillets, West six10, JBWeld for initial attachment to MMT.

Also, the point masses for the recovery gear in the simulation will move aft during liftoff, reducing the stability margin. Add a stuffer tube and/or nose weight.

JLCR is attached to sled, sled attached to harness next to NC…meant/designed to not shift.

 

[3stoogesrocketry]

.125 G10

TTW, internal and external fillets, West six10, JBWeld for initial attachment to MMT.

JLCR is attached to sled, sled attached to harness next to NC…meant/designed to not shift.

I'd send it, but there will be some flutter. I don't think your fins will come off. Take a video

 

[rcktnut]

With more information (JLCR) being used I changed my vote to send it rather than other. Recovery from altitude with single deploy was a concern rather than stability.

 

[MarsLander]

Updated info in original post with requested info…

 

[MarsLander]

It is not even remotely applicable in this case.

of the marvelous structure of reality. It is enough if one tries to comprehend only a little of this mystery every day.”

^^^

 

[kjhambrick]

@MarsLander --

Looks OK to me up to 10 mph ...

I've followed your build thread: L2 Design and Build...4x Upscale EAC Viper -- that is a pretty rocket !

And I know you've done all your homework Flutter Tools for You

I am curious though ... do your wide-span1/8 inch G10 fins flex when you try to bend them ?

Good luck with your Level 2 !

-- kjh

$ for i in 5 10 15; do ./aoa.sh 84 $i; echo '' ; done

# Rail Vel = 84 fps
# Rail Vel = 57 MPH
# Wind speed = 5 MPH
# AoA( Radians )= 0.0870808
AoA( Degrees )= 4.98937

# Rail Vel = 84 fps
# Rail Vel = 57 MPH
# Wind speed = 10 MPH
# AoA( Radians )= 0.172861
AoA( Degrees )= 9.90419

# Rail Vel = 84 fps
# Rail Vel = 57 MPH
# Wind speed = 15 MPH
# AoA( Radians )= 0.256151
AoA( Degrees )= 14.6764

 

[jsdemar]

Changed my vote to go for it. Fins will buzz but stay on with this motor, I think.

 

[Spacedog49Krell]

I agree with kjh, flight stability and off-the-rail flight deviation oscillations well within limits for 10 MPH winds.

 

[MarsLander]

I'd send it, but there will be some flutter. I don't think your fins will come off. Take a video

I am curious though ... do your wide-span1/8 inch G10 fins flex when you try to bend them ?

Fins will buzz but stay on with this motor, I think.

Ahhh....the question of the day...back to Flutter! Oh, so esoteric, our boundaries.

TAP (for level 2) says don't worry about flutter until Mach. Standard Atmosphere Mach = 791mph. Prescient, I think, given the below analysis. Experience and RW results trump "science."

From Flutter tools for you..., Duncan McDonald (DMcD) used a flexural modulus and Poisson value that I think are incorrect. However, based on his model, he collected anecdotal evidence of shred speed being 220% of Vf based on NACA TN4197 and his Flexural/Shear modulus. Using his Flexural Modulus and Poisson values (which he based the 220% on, this rocket), this rocket should not shred below 807.4 mph.

Applying the 220% to lower Vf values reached by MarsLander and Bennett (https://www.apogeerockets.com/education/downloads/Newsletter615.pdf), and associated spreadsheet, shred velocity is still well above noted velocity with the K695R.

Bennett agrees with my Poisson value, but equivocates on the flexural modulus and notes..."If we search the Internet for data pertaining to the shear modulus of G10 or G12 fiberglass, we will obtain values ranging from 425K to 1.7M psi (or the equivalent SI values). Experimental direct measurements report values near 775,000 psi (5,343,436 KPa). This number is also approximately the median of many reported and calculated values for both fiberglass and carbon fiber composites."

HOWEVER, he then uses 600,000 as his recommend shear modulus, "Allowing for margin."



Ignoring his margin allowance, and using the "measurements report values near 775,000," we get summary 220% of Vf as the shred boundary.



I'm inclined to base everything on Duncan McDonalds calculations and shred boundary, because his real world comparison (220%) is based on HIS shear modulus.

Maybe I will give heads up to the RSO....and SEND IT!

Take a video

I have the shroud for the video camera...still debating if I'm willing to drill the holes into this rocket, just for the video.

 

[Onebadhawk]

This ^^^
And how are they attached?

Also, the point masses for the recovery gear in the simulation will move aft during liftoff, reducing the stability margin. Add a stuffer tube and/or nose weight.

Nice, lol..

Teddy

 

[Ronz Rocketz]

Tuco's dilemma...

 

[rfjustin]

Send it, but add altimeter deploy first.

 

[86mustang408w]

Its good, send it...Half...lol.

Nice I just got my L2/L3 setup..