TRF Summer Build Off: Der V-Max

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Screaminhelo

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Here is my entry.

I love low'n'slow launches and short, fat rockets so this is my attempt to combine the two.

View attachment BYOD.ork

Neil_w got me to thinking about tubes and rings and I started playing in OR. It will have tube fins and the balsa fins are there to approximate the final profile. The ring fin will be used if needed. You may also note that the motor is rather deeply recessed...

That is where the gadget in the image below comes into play.

I will need to draw in some air to help protect the aft end of the airframe and attempt to avoid an encounter with Mr. Krushnik. This is the master for an NACA style inlet. The inlet will terminate just FWD of the nozzle so that the exhaust stream can draw in cool air. This is not an attempt at DGS though, so any added stability from this will be a bonus.

The ultimate goal is to fly this on a BP F motor and keep it below 1k feet. Right now, mind sim says it is doable with a 6' rod (I will have to watch the weight gain) but I will go to a composite if needed.

It will be a slow start though, I'm going camping with Uncle Sam for a while.
 

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neil_w

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I hope the ring makes it into the final product. This should be cool, and I'm really looking forward to seeing how that inlet looks and works.

I'm getting a bit of a yearning for a stubby low and slow flier like this, will be watching this one for sure.

This contest is a rousing success already, if you ask me.
 

Daddyisabar

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Low and slow, short and fat, trying to avoid Mr. Krushnik. Sounds like fun launching off WD 40 slicked, 6' rod!.
 

dhbarr

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Here is my entry.

I love low'n'slow launches and short, fat rockets so this is my attempt to combine the two.

View attachment 292522

Neil_w got me to thinking about tubes and rings and I started playing in OR. It will have tube fins and the balsa fins are there to approximate the final profile. The ring fin will be used if needed. You may also note that the motor is rather deeply recessed...

That is where this comes in.
View attachment 292523
I will need to draw in some air to help protect the aft end of the airframe and attempt to avoid an encounter with Mr. Krushnik. This is the master for an NACA style inlet. The inlet will terminate just FWD of the nozzle so that the exhaust stream can draw in cool air. This is not an attempt at DGS though, so any added stability from this will be a bonus.

The ultimate goal is to fly this on a BP F motor and keep it below 1k feet. Right now, mind sim says it is doable with a 6' rod (I will have to watch the weight gain) but I will go to a composite if needed.

It will be a slow start though, I'm going camping with Uncle Sam for a while.
I've been wanting to play with an internal, forward-mounted motor. How are you determining how far forward you can get away with?

My thinking was that I would fire a motor on it's side 0,1,2,3 motor-calibers above a sheet of plywood and use the discoloration to approximate the shape of the exhaust plume, but I wasn't planning for inlets.

Looking forward to this one!
 

Screaminhelo

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Low and slow, short and fat, trying to avoid Mr. Krushnik. Sounds like fun launching off WD 40 slicked, 6' rod!.
Unfortunately, I could not solve my stability issues with nose weight. Is stuffing the motor 4" up the tailpipe an acceptable solution?

I hope the ring makes it into the final product. This should be cool, and I'm really looking forward to seeing how that inlet looks and works.
I'm getting a bit of a yearning for a stubby low and slow flier like this, will be watching this one for sure.
This contest is a rousing success already, if you ask me.
The ring is a bit of a backup performance wise, the tube fins will cut from 2.6" tube but 1/3 will be cut out so that the edges will butt against each other and the height will be reduced to about 1.3". I may need the extra drag for stability but I am a bit concerned about weight if this thing is going to work on a 29mm BP motor. That being said; the Ringed Warrior project is what got me started down this road and I kinda hope it makes the final cut too.

I've been wanting to play with an internal, forward-mounted motor. How are you determining how far forward you can get away with?
My thinking was that I would fire a motor on it's side 0,1,2,3 motor-calibers above a sheet of plywood and use the discoloration to approximate the shape of the exhaust plume, but I wasn't planning for inlets.

Looking forward to this one!
I would have to find it again, but I remember reading a ratio in one of the Apogee PoF newsletters. I am sure that there are limits, but you can recess rather far if you have enough air coming in at the nozzle to maintain flow out of the tube. The finless design featured in the article had the motor recessed several calibers (you have to think tube diameter here since that is really the driving factor) but had a large opening around the airframe at the nozzle to allow the motor thrust to draw in air.

Found it! Peak of Flight #379

In a nutshell, it calls for an inlet area greater than D2 or 6.76" in this case. Now that was for stability using DGS, I am not sure if the same applies in my case but I will be in the neighborhood for sure.
 

Daddyisabar

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When you are desperate to move the CG up because of questionable design, use any and all techniques you can imagine, even if it means putting up with a little motor burn!
 

Screaminhelo

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Well, this is as far as I'm going to get for a while.

First is the final fin shape next to the initial cut from a T-80 tube.

The next two pictures are of my mock up on a scrap tube. The fin height is only about 1.3" which may not quite get the job done so the MindSim optimization tool is suggesting that the ring fin be added.
20160601_194522.jpg20160604_210218.jpg20160604_210258.jpg

I will be away for quite a while...er...camping. I should be able to check in from time to time but building is out of the question.
 

KenECoyote

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Sounds very interesting! However I don't have OR...can someone post a pic of the rocket/diagram? :)
 

Screaminhelo

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Sounds very interesting! However I don't have OR...can someone post a pic of the rocket/diagram? :)
For this one, OR only provides a very general shape. The reality of the tube fins is very different from the actual rocket. Since they are something other than straight, full diameter tube fins, MindSim is more helpful.

I am also unable to do the inlets in OR (but k'test may be able to figure it out). They are about 6" long and modeled often an NACA inlet and terminate at the aft end of the motor tube.

Speaking of the motor tube, the aft end is recessed about 4" to offset the CG.

The airframe is planned to be 16" with an 8" ogive nose cone.

It may be a while but I will try to get a bad drawing posted before I go much further, which will certainly be a while.
 

Screaminhelo

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I do have a sketch that I could upload but it is on my phone, my only connection for.quite a while, and I can't get it to upload. Any ideas other than a hosting site?
 

neil_w

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What about Dropbox? Easy enough to share a link from there.
 

Screaminhelo

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Finally got the link to work. This is just a drawing of the general idea, three tube fins with an outer ring and three inlets tat terminate at the nozzle.
 

dhbarr

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Finally got the link to work. This is just a drawing of the general idea, three tube fins with an outer ring and three inlets tat terminate at the nozzle.
Sweet! I'll bet this thing whistles like crazy.

I'm trying to imagine this at Mach with the inlets interior to the rings, it's doing strange things to my brain.
 
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KenECoyote

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OOOH! Very nice and a quite a gorgeous design! :clap:

BTW - It's better juju to post the pic with the pointy side up. Just sayin'. ;)
 

Screaminhelo

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OOOH! Very nice and a quite a gorgeous design! :clap:

BTW - It's better juju to post the pic with the pointy side up. Just sayin'. ;)
I had an aircraft, 599, that only worked right when I moaned, groaned, gripped and complained about her, kind of a reverse psychology thing. Maybe the same vibe will work here.
 

KenECoyote

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I had an aircraft, 599, that only worked right when I moaned, groaned, gripped and complained about her, kind of a reverse psychology thing. Maybe the same vibe will work here.
That's how my wife gets me to work. :wink:
 

Screaminhelo

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Only a few more days left here! The problem that I have been having out here is that I can't turn off MindSim. I should probably stick with my original plan but I have come up with a variation that is very tempting to try.
 

KenECoyote

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The problem that I have been having out here is that I can't turn off MindSim. I should probably stick with my original plan but I have come up with a variation that is very tempting to try.
I have no idea what you're talking about (so says the guy with an out of control mindsim) . :wink:
So what is the variation? :)
 

KenECoyote

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Regarding a name, how about...

"I Want to Vent"

TRF'ers should relate to this well. :wink:
 

Screaminhelo

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I have no idea what you're talking about (so says the guy with an out of control mindsim) . :wink:
So what is the variation? :)
I'll try to explain since I have no way to post a picture out here. I am considering using a section of body tube as nothing more than a jig to glue the fins together so that they are somewhat free floating and using fiberglass wafers to connect them to the aft end of the intakes.

Regarding a name, how about...

"I Want to Vent"

TRF'ers should relate to this well. :wink:
The name All Hail Cesar has entered my mind. It has nothing to do with the design but I can be a bit of a joker sometimes.
 

KenECoyote

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I'll try to explain since I have no way to post a picture out here. I am considering using a section of body tube as nothing more than a jig to glue the fins together so that they are somewhat free floating and using fiberglass wafers to connect them to the aft end of the intakes.
Damn, that sounds really nice! However would it make it more susceptible to landing damage if landing motor end down?

The name All Hail Cesar has entered my mind. It has nothing to do with the design but I can be a bit of a joker sometimes.
I don't quite get the reference...is it referring to the movie? :confused:
 

KenECoyote

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The inlets keep reminding me of a Ferrari F40...how about painting it red and naming it R40? :grin:

 

Screaminhelo

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Landing damage is a concern as well as being a bit complicated to build. That idea may have to wait for later.

The name struck me when we were at Six Flags and waiting in line for the Batman ride. Green and purple struck me as a good color combination. We'll see what strikes me when I can start digoing into the build.
 

jqavins

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Oooh, I like, I like. And without the picture, I was imagining the inlets the other way around.

The inlets keep reminding me of a Ferrari F40...how about painting it red and naming it R40? :grin:
And fly it on an F40? (Well, that might not give the desired low and slow, would it?)
 

Screaminhelo

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The inlets keep reminding me of a Ferrari F40...how about painting it red and naming it R40? :grin:
Then I would be inclined to paint the intakes a contrasting color, black comes to mind, and I just can't bring my self to use UGA colors.
 

KenECoyote

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The inlets keep reminding me of a Ferrari F40...how about painting it red and naming it R40? :grin:
Strike that...I would love to make a copy of your design, but call it "V40" and give it a V2 camo paint scheme! :drool:
 

Screaminhelo

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I am liking the V2 reference, you have given me an idea so get ready for Der Vmax!
 

jqavins

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RockSim allows for a better job of showing the tube fins on this design, and a rough approximation of the air scoops. It still can't show the bias cuts fore and aft on the tube fins. Hope this helps.
Unnamed Rocket 1.jpgUnnamed Rocket 2.jpg

One thing, though. I didn't do anything with the feature on the body tube circled in blue in the sketch, because I don't understand what it is. It looks like an air inlet, but I thought the side scoops were the inlets, so I'm confused.
Notch.JPG
 

Screaminhelo

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One thing, though. I didn't do anything with the feature on the body tube circled in blue in the sketch, because I don't understand what it is. It looks like an air inlet, but I thought the side scoops were the inlets, so I'm confused.
View attachment 294929
That is just a poor attempt at showing the inlet in profile.

Thanks for the RocSim backup. There will be some minor changes at this point (got to live up to the Der V-Max name) bu they should work in my favor, but it is nice to know that RocSim and mindsim agree.
 
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