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Waive Goodbye Concept and Build

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fyrfytr310

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So it took me about 4 seconds to start thinking about my next project after getting my L3. The highest waiver I have available within a reasonable drive is 18,000'. With that said, behold my concept model for kissing that waiver limit. I have named her Waive Goodbye. Initial SIM puts it at ~15,000' on the formidable N4000. I have exceeded simulation every time but obviously this value will change as I go through concept and into the build. One major, major item I need to learn more about before I begin to even consider buying components is fin flutter. This sim has a max velocity of 1200mph and I am not confident the fins shown will survive. Additionally, I need to research how these materials in general will handle the heat generated at these speeds.

View attachment Waive Goodbye.ork
 

K'Tesh

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Heading off to bed, and I have no experience with L3 building. So, I'll just say...

Break a Record!!! (in a positive way!)
 

Igotnothing

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Fins very thin for their area. Couplers are rather short for their second job - keeping body tubes pointed in the same direction.
 

fyrfytr310

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Those fins are pretty light material at only .118 thick FG, do you have a copy of AeroFinSim? AFS will allow you to do a flutter analysis on your fins.

http://www.aerorocket.com/finsim.html

To get the AFS you have to follow the directions at this link :

http://www.aerorocket.com/products/products.html
Yup, concept only at this point. I had FinSim on another machine that is no longer available to me. Not that it matters much as I didn't get much use out of it the first go. Requesting a new link now.
 

EeebeeE

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Sweet rocket... A couple thoughts I have to add improvement in performance.
Change your fin settings to airfoil. You can accomplish a good bevel with a belt sander, but try it first on some scrap.
I think for this I'd use 1/4" G-10.
Shorten the size of the fins just a tad... It will help you cut construction costs a lot. I redid them with a root of 24", A sweep of 22" and a Cord tip at 8" away from the airframe.
Use 1/4" G10 for your fin rings and add a couple evenly spaced across the fin roots. This will stiffen them up a lot and give you a better anchor to the airframe. I suggest you get hold of Upscale CNC and have a set of interlocking fins and rings made, which will anchor them even more.
Your coupler tubes should be at least 12" instead of 8" A big and fast rocket like that will encounter a lot of turbulence.
Consider an Ogive nose cone instead of a conical one. It can get you another 1,000 to 1,500' in altitude.

So after a little playing, this is what I came up with. You could fly it at URRF in Potter, NY next year.

Waiver Goodbye.jpg
 

fyrfytr310

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I love this forum lol.

FinSim does not like this fin design at these projected speeds. Not. At. All...
 

EeebeeE

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I love this forum lol.

FinSim does not like this fin design at these projected speeds. Not. At. All...
I'll bet it doesn't. Use Rocketpoxy. That will help your Finsim design. Shear strength is 14,300 PSI according to their specs. I am more conservative and estimate 6,000 PSI.
 

fyrfytr310

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I may have found a decent balance. We are still over on the divergence speed and even this required some serious nose ballast. If I go to the 8" height, it takes a ton off the max speed.

 

EeebeeE

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I love trying to get the most speed and altitude out of an airframe and still keep it stable. Add a tailcone and rake the fins backward a little. Keep them at 8". Shorten the length of your fins from 24" to 18". This adds stability. Assume your e-bay with rods and hardware is going to weigh more like 3 lbs. instead of 7.5 oz. That eliminates the need for nose weight.

Then stick an N5800 in it and shoot for 30,000+ feet. Or stick with your N4000 and go for 25,000'.

Of course this looks nothing like your original design, but that's how rocket designing goes sometime.

Waiver Goodbye 1.jpg View attachment Waive Goodbye 1.ork
 
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fyrfytr310

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I love trying to get the most speed and altitude out of an airframe and still keep it stable. Add a tailcone and rake the fins backward a little. Keep them at 8". Shorten the length of your fins from 24" to 18". This adds stability. Assume your e-bay with rods and hardware is going to weigh more like 3 lbs. instead of 7.5 oz. That eliminates the need for nose weight.

Then stick an N5800 in it and shoot for 30,000+ feet. Or stick with your N4000 and go for 25,000'.

Of course this looks nothing like your original design, but that's how rocket designing goes sometime.

View attachment 306318 View attachment 306319
You have a lot of fun with this. I can tell :)

I've gone through a redesign after some consultation with others. Thinking about doing a 5" instead.
 

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fyrfytr310

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Here is an interesting combination, bearing in mind that the overriding goal here is to max out the 18,000' waiver and not necessarily being quick about it. Departing from the N4000 and going with an N1000, and its crazy long burn time, gets us there without risking an unplanned, rapid disassembly of the fin can.

 

fyrfytr310

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If you have followed any of my builds, you will know that I like simple paint schemes. This one will be no different:

 

fyrfytr310

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And component ordering has begun! My in-laws are graciously sourcing the nose cone for Christmas! The rest of the family has been instructed, for those offering to buy gifts, to focus on MadCow gift certificates.

Mike Fisher at Binder is yet again helping me with a thrust plate, predrilled for an Aeropack.

I'll order the Aeropack tonight as well. Might even get some of that fancy laser engraving.

I have engaged Upscale CNC for budgeting numbers and I have submitted drawings for the fins and CRs to a local machine shop (which can't read .orks) my company uses professionally for good measure.

*Edit: Oh and I ordered a 5" Mobius shroud from Additive.
 

fyrfytr310

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Simulation with the N1000.



My thrust to weight ratio is a little light (4.2:1) so I'll try play around with that a little bit but I'll also come to the launch prepared with the thrust curve which will prove a ratio well above 5:1 for more than half of the 12 second burn time. Right now I am coming in at 53lbs.



Now, playing my own devil's advocate, my rail speed is lower than I would like at 28mph. I looked into the launch parameters and found the length set at 48" for some reason. I changed to 96" with no change. So I upped to 144" (club max) and still no change. Not sure if I am doing something wrong in OR or if my understanding is flawed somewhere. I'll keep playing around.
 
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fyrfytr310

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I have altered the model to give myself more room for the main chute by increasing its airframe from 36" to 48" and reducing the intermediary/booster extension from 36" to 24" so the overall length isn't impacted. This will also make transport much easier.
 

dford

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good fun to follow fantastic minds. this is one of those opportunities. 13+ feet? N motor?
i watched a video of aerotech prepping an M motor.
one day in the very distant future i hope to be where builds like this is.
definitely following. in the shadows.:dark:
 

EeebeeE

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This is a sweet design. Good luck with your build. Post construction photos and flight videos.
 

OverTheTop

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Have you considered factoring in a deployment bag into your recovery method? I am tending towards using them on my larger rockets. Seem to make for easier packing and cleaner inflation.

N1100 motor is really nice. I certified L3 on it. I was considering using the O3400 but backed off a little to my original plan.
 

fyrfytr310

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Have you considered factoring in a deployment bag into your recovery method? I am tending towards using them on my larger rockets. Seem to make for easier packing and cleaner inflation.

N1100 motor is really nice. I certified L3 on it. I was considering using the O3400 but backed off a little to my original plan.
I have considered, and will continue to do so for the time being. I have a perfect record with z-folding and masking tape (used it on my 70lb L3) so I don't feel a need to change but it would be nice to get that experience under my belt.
 

fyrfytr310

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This is a sweet design. Good luck with your build. Post construction photos and flight videos.
Absolutely! I might do two cameras on this one. One facing out and one taking the traditional downward shot.
 

fyrfytr310

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And why did I have a 48" MMT? Don't know. Reduced to make more sense...
 

fyrfytr310

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98mm retainer body and airfoil rail buttons have arrived. I ordered a retainer cap laser etched just for this project.

I will be going with Upscale CNC for the fins, CRs and nose cone access bulkheads. Just need to work out a couple more details with Nat.

I'll be ordering the airframes, couplers and mmt from Wildman (save for a couple items I was able to relieve from another forum member) this weekend.
 

fyrfytr310

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Fins and CRs are well underway. I have asked MAC to bevel the fins for me. I'll be sure to post pics upon arrival.

Also, I placed the order for the remaining airframe components with Wildman.
 

fyrfytr310

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And after recovery harness discussion adnauseum, I have ordered the requisite equipment from Teddy at OneBadHawk!
 
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