"GARC" inspired concept

[Loutky]

I know, I know... its a whacky idea... and believe me... it only came about by chance... now I am too far down the hole to look back!

I was going through my usual spaces online... soon I found myself looking over LEGO concepts and then it happened...I came across the good ol' GARC idea (Basically... imagine a sci-fi formular1 rocket powered racer... you will soon get the idea...)... I found myself smile and a voice in my head say "now one of THOSE would make a cool rocket!!"

Well... first it was a sketch... then it became an Open Rocket project... and now...well... Ive begun shaping the balsa canopy and front body tube.

Yep... I get it... there is a high chance this is too experimental...
But wanted to throw it out in the forum to see if anyone has tried anything similar??
...or is it just a little too crazy??
...or does it break one too many golden rules??

Essentially, the motor would be mounted "tractor" style in the nose... the canopy is stiff balsa, shaped to give some style... the rear body tube is just to ensure the fins are aligned and centred to the engine...

 

[neil_w]

Welcome to the forum!

I see no reason that won’t fly fine. Biggest concern I can see is that the motor is going to roast the lower fin assembly.

 

[les]

From a stability point of view, it looks good to me.
Until the rear fin unit gets burnt away....

 

[mjennings]

Never thought I see a GARC rocket. I miss the Galactic Astroid Rally Circuit community theme. Can't wait to see it painted! We have a few AFLOs on the forum check out the we'll just LEGO thread. Welcome. For those initiated more GARC goodness can be viewed here.
https://flickr.com/groups/2142724@N23/pool/

 

[Daddyisabar]

Singing in my Johny Cash deep voice: "Burn, burn, burn, the ring of fire, the ring of fire."

Using tractor motors to burn your airplane rocket's tail is awesome!


Yes Mr. RSO, shaping your fins in flight with FIRE is a good idea!

 

[Daddyisabar]

I know, I know... its a whacky idea... and believe me... it only came about by chance... now I am too far down the hole to look back!

I was going through my usual spaces online... soon I found myself looking over LEGO concepts and then it happened...I came across the good ol' GARC idea (Basically... imagine a sci-fi formular1 rocket powered racer... you will soon get the idea...)... I found myself smile and a voice in my head say "now one of THOSE would make a cool rocket!!"

Well... first it was a sketch... then it became an Open Rocket project... and now...well... Ive begun shaping the balsa canopy and front body tube.

Yep... I get it... there is a high chance this is too experimental...
But wanted to throw it out in the forum to see if anyone has tried anything similar??
...or is it just a little too crazy??
...or does it break one too many golden rules??

Essentially, the motor would be mounted "tractor" style in the nose... the canopy is stiff balsa, shaped to give some style... the rear body tube is just to ensure the fins are aligned and centred to the engine...


View attachment 589760View attachment 589761View attachment 589764

I would ditch the single motor and go for three canted cluster tractor motors aimed at those big, lovely gaps between the fins! Has worked for me many times.

 

[Daddyisabar]

My mindsim is showing a tremendous amount of stress on the cockpit connection ends to the paper tubes. Remember, your bond is only as strong as the layers of paper on your tubing. A large surface area and correct glue is good, but it may need additional reinforcement like bands or glue rivets, etc.

 

[Daddyisabar]

On a D12 motor you will seriously damage anything less than approximately ten inches behind and in line with the nozzle. Then there is then a slight "hibachi" zone and then a larger super soot zone requiring post launch clean up.



Putting fins directly behind a burning motor is frowned upon by the Jedi. However, if you keep the rear horizontal tail just out of the danger zone you will be fine. Give in to the dark arts and fly the rockets you love.

 

[Loutky]

On a D12 motor you will seriously damage anything less than approximately ten inches behind and in line with the nozzle. Then there is then a slight "hibachi" zone and then a larger super soot zone requiring post launch clean up.

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View attachment 590021
Putting fins directly behind a burning motor is frowned upon by the Jedi. However, if you keep the rear horizontal tail just out of the danger zone you will be fine. Give in to the dark arts and fly the rockets you love.

hahaha... the hibachi zone!!! love it
Now the golden question... how in the heck do you calculate the hole cutouts for the angled motor mounts?

 

[mjennings]

I think Fliskits has the Tres mounts back in production. If you're looking for a pre designed solutions. It's a ellipse with minor axis the mmt outside diameter and major axis BT Outer Diameter over sine of the can't angle. If I worked it out right.

 

[BABAR]

On a D12 motor you will seriously damage anything less than approximately ten inches behind and in line with the nozzle. Then there is then a slight "hibachi" zone and then a larger super soot zone requiring post launch clean up.

View attachment 590020
View attachment 590021
Putting fins directly behind a burning motor is frowned upon by the Jedi. However, if you keep the rear horizontal tail just out of the danger zone you will be fine. Give in to the dark arts and fly the rockets you love.

Quantification of what I’d call the “Hibachi-Angle” is something I’ve always wondered about, and you and @jflis are likely the experts.

Barring blowback off the blast plate, is there a constant acute angle (which in 3D would be a cone) of significant radiant heat behind the nozzle? Objects within the cone would get grilled, object outside would be okay?

Or does it vary with the motor type, the rocket velocity (would anticipate a wider angle as the rocket starts at zero velocity on pad and decreases at max V), and or max V of rocket itself?

For @Loutky ‘s design, I was wondering if a layer of aluminum can on the INSIDE of the ring and along the under surface of the fuselage would be enough? I was thinking a single layer inside the ring proooobaaaably wouldn’t stretch the “no metal fins” too much, but a complete wrap (internal and external) would be a low power NAR Safety code violation.

 

[Daddyisabar]

The cone of shame a.k.a. THE DANGER ZONE, can vary from motor to motor, flight to flight. On the Avro Lancaster tail it was only a quarter inch lift that went from flame cutting force to mild hibachi. Air flow, nozzle dynamics, propellant type, atmospheric conditions, etc., must all be considered in the complex mindsim equation. Failure is not an option.

No weighty, Billy Beer can or tinfoil wrap solution would satisfy my old RSO. Going to splatter droplets of molten metal on the helpless crowd today are you? Pad assignment REJECTED due to exceededingly poor rocket design, Period! Noted on flight card an filed in permanent record. They came to him with skulls full of mush and left thinking like rocket scientists. Learn the ways of the Jedi.

Icarus flew too close to the sun. Placing vital rocket components behind your motor is scary...FUN!

 

[Raythain]

Barring blowback off the blast plate, is there a constant acute angle (which in 3D would be a cone) of significant radiant heat behind the nozzle? Objects within the cone would get grilled, object outside would be okay?

Or does it vary with the motor type, the rocket velocity (would anticipate a wider angle as the rocket starts at zero velocity on pad and decreases at max V), and or max V of rocket itself?

First order mindsim says that it will at least vary by motor. Nozzle expansion ratio will determine the shape of the danger zone immediately behind the motor. But after that, it would be a fuzzier line as the exhaust gas slows down and the heat is dissipated. Then you have to worry about messy outside factors like air temp, wind speed and direction.

 

[Loutky]

Update... over the last few days i e modelled and then 3d printed a more sleek and streamline rear section/cockpit from PETG. As you can see... ive taken onboard much of what I read and now have cantered motor mount holes. Yep... its a mini engine sized A10-3T build as a start point...

 

[Daddyisabar]

Smaller motors are much easier to work with. Less likely to get a call from Mr. Krushnic or Mr. Hibachi!

 

[lakeroadster]

I know, I know... its a whacky idea... and believe me... it only came about by chance... now I am too far down the hole to look back!

I was going through my usual spaces online... soon I found myself looking over LEGO concepts and then it happened...I came across the good ol' GARC idea (Basically... imagine a sci-fi formular1 rocket powered racer... you will soon get the idea...)... I found myself smile and a voice in my head say "now one of THOSE would make a cool rocket!!"

Well... first it was a sketch... then it became an Open Rocket project... and now...well... Ive begun shaping the balsa canopy and front body tube.

Yep... I get it... there is a high chance this is too experimental...
But wanted to throw it out in the forum to see if anyone has tried anything similar??
...or is it just a little too crazy??
...or does it break one too many golden rules??

Essentially, the motor would be mounted "tractor" style in the nose... the canopy is stiff balsa, shaped to give some style... the rear body tube is just to ensure the fins are aligned and centred to the engine...


View attachment 589760View attachment 589761View attachment 589764

New Guy Alert... Welcome!

Fire, hibachi, Toasty? Gnaw, I am betting you'll be fine. Sure it'll have some scorching, but nothing to stop the build. Damn the torpedoes!

 

[jqavins]

Welcome to The Rocketry Asylum.

Comparing the original dry fit and the new 3D printed part, I don't quite see how the whole thing now goes together. Would you be so kind as to dry fit the new configuration?

I had originally been concerned, when I saw the sketch, not only about torching the aft assembly, but also about the bending load on the slender connecting member (cockpit) and at the cockpit to tube interfaces. Then I was happier when I saw the beefier part and really large contact area in the first dry fit. I'm even happier with the 3D printed part withstanding the bending itself, but I'm still concerned about the bending at the PETG to paper interfaces, since I can't see how much contact area - or what type of connection - the new configuration is providing.

 

[BABAR]

Welcome to The Rocketry Asylum.

Comparing the original dry fit and the new 3D printed part, I don't quite see how the whole thing now goes together. Would you be so kind as to dry fit the new configuration?

I had originally been concerned, when I saw the sketch, not only about torching the aft assembly, but also about the bending load on the slender connecting member (cockpit) and at the cockpit to tube interfaces. Then I was happier when I saw the beefier part and really large contact area in the first dry fit. I'm even happier with the 3D printed part withstanding the bending itself, but I'm still concerned about the bending at the PETG to paper interfaces, since I can't see how much contact area - or what type of connection - the new configuration is providing.

I’m with Joe. Like to see a layout that shows trajectory of the canted Motor jets. I think @Daddyisabar has shows some nice barbecue demonstrating that even with canted motors you may not have sufficient lateral clearance of the ”cone of Hades” to avoid condemning parts of the rocket structure. That beautiful ring in particular, part of me wonders if you would be better of firing through the clear middle of it that trying to go around the sides.

 

[jqavins]

I'm known to be a nervous Nelly, so it's a relief that someone else has similar thoughts.

 

[Loutky]

Hey all, Ive done some tweaking and reworking... heres some dry fit pics with motors mounted... honestly... im kinda loving where this one is heading. Initial swingtest was a success and all seems to be on track

 

[jqavins]

Thanks for the pictures. I get it now. I like it. You have my blessing to continue.

 

[Daddyisabar]

Midcants rock!

 

[BABAR]

Hey all, Ive done some tweaking and reworking... heres some dry fit pics with motors mounted... honestly... im kinda loving where this one is heading. Initial swingtest was a success and all seems to be on track

Very cool. Where does the ring go? Or has it already went?

 

[Loutky]

Just finished the initial paint job on the GARC inspired rocket... the stripes were a bit of a masking tape fail and had to hand paint way too much than what I wanted to!! ... over all... pretty happy with how my first crack at this style of rocket came out... cant wait to get it in the air!

 

[lakeroadster]

Have you done a swing test on that? Might be worth while and quite educational.

 

[Loutky]

Yeah! Loaded thhem motors up and swung away... no issues from the test

 

[mjennings]

Very nice looks good!

 

[BABAR]

Have you done a swing test on that? Might be worth while and quite educational.

Have you done a swing test on that? Might be worth while and quite educational.

Good call. Glad it tested good!

 

[jqavins]

Yeah! Loaded thhem motors up and swung away... no issues from the test

Still, do remember those two little "two little wordses". "First flight." "Heads up!"

 

[BABAR]

Where’s the launch lug?