TwinJet to Rocket Propelled/Ever been done?  
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TwinJet to Rocket Propelled/Ever been done? - 8/7/2006 5:25:56 PM   
TheJester


 

Posts: 76
Joined: 5/6/2006
From: Fairfield, IA, USA
Status: offline 		Ok, I'm posting some pictures of what I'm trying to do here, but I'm wondering if anyone else has attempted this as well. I'm taking a Twin Jet that will take off and land via hand launch like normal. Then, while in flight and triggered via RC I am going to ignite a perminenantly attached "G" sized ROCKET reload kit and see what happens.
The first photos, in white, are when I had a Hacker A20-20L motor connected to the rear with a 11x4.7 prop. The plane flew great, but not all that fast, so I switched to a20-6xl with 5x5 prop instead of the designed 2 480 brushed motors. When I had it there, the plane flew perfectly and FAST, but I was afraid that when igniting the rocket, it would either damage my motor or burn the prop off, so have moved it to the forward position ahead of the rocket. I'm now trying to balance it out to fly then work on the ignition system.

Let me know any input as I need help with the ignition system that will require 12volts and weight is a MAJOR issue.



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RE: TwinJet to Rocket Propelled/Ever been done? - 8/10/2006 6:08:10 PM   
TheJester


 

Posts: 76
Joined: 5/6/2006
From: Fairfield, IA, USA
Status: offline 		Ok, maybe this project only interests me or no one wants to think about it.

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/10/2006 6:31:35 PM   
Couch-pilot



Posts: 192
Joined: 11/10/2002
From: Burlington, ON, CANADA
Status: offline 		Yes, stuff like this has been done before. Looking at your pics, I'd suggest joining the rocket boost gliders forum on yahoo groups, and checking out the motor mounts. Nylon straps won't keep a "b" engine in place, much less a "G". Most mounts involve your traditional cardboard tube, epoxied into plywood mounts. This motor will produce a phenomial amount of thrust for a short time. Most typical model rockets accelerate to almost 350-400 mph by the time they hit the end of the launch rod - that's 36"!!!! Most of the plans, write-ups
I've read have cited wing failure due to the extremely high G-loads encountered - ie. they get ripped off on launch. You may have to use glass reinforcing tape an the leading edges/spars. Weight is a critical factor, but so is strength.

And good luck

PS - I've got both the Estes Astroblaster and Stratoblaster. They're still in the box, but I've studied the instructions for possible motor upgrades - I'm a power-freak too

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/10/2006 6:43:04 PM   
TheJester


 

Posts: 76
Joined: 5/6/2006
From: Fairfield, IA, USA
Status: offline 		Yeah, on our first test of the smaller reload kit, test fire on the ground, the nylon zip ties melted, so it has now been changed to a slab of balsa between the foam and rocket epoxied down. Then I used the Epoxy putty to attach the reload kit to that.

The over all deal is that I understand the rocket gliders, but what we are trying to do here is, have the plane take off, land, and even fly around like normal first and last, but in the middle ignite the rocket via GER/FLAP switch.

Thanks for the leading edge info, I will give them a thorough coat of epoxy then covered in Strapping tape, like I did with my Combat Wing.

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/10/2006 6:49:00 PM   
Couch-pilot



Posts: 192
Joined: 11/10/2002
From: Burlington, ON, CANADA
Status: offline 		Try a search on RCU for Bell X-1 - a while back some guys built one for launch from a B-29.

_____________________________

Skydiving...Not a sport, a safety device....
"There is no good reason for jumping out of a perfectly good airplane

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       Post #: 5

RE: TwinJet to Rocket Propelled/Ever been done? - 8/13/2006 6:46:44 AM   
RetroFlight


 

Posts: 21
Joined: 8/13/2006
From: Atlantic, IA, USA
Status: offline 		Contact Doug at RetroFlight.com he can help you out email doug@retroflgiht.com.l
Retro Flight designs and fabricates small to large Rc rocket gliders. Specialized in X-15's.


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RE: TwinJet to Rocket Propelled/Ever been done? - 8/17/2006 4:41:19 AM   
TheJester


 

Posts: 76
Joined: 5/6/2006
From: Fairfield, IA, USA
Status: offline 		here is the idea: www.ratpackinternational.com/TwinJetComingSoon.mpg

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/18/2006 6:11:20 PM   
rcmaster-RCU


 

Posts: 115
Joined: 10/21/2002
Status: offline 		I am currently working on a rocket propelled park zone stryker with estes E sized motors. It will be a two stage deal. One motor to get it up and another to use while in flight. G motors are very powerful. I had a 2 meter spririt great planes glider rocket propelled with an F motor and it was too much for it. It worked, but just barely. The wings flexed tremendously and due to the motor placement, it would do a violent loop and not a straight up and away type deal. In one flight the motor didn't ignite in flight like planed, so the plane landed. The motor ignited as soon as the plane came to a rest. An F motor had enough power to take off( from grass) this big glider, loop the plane in about a 20 ft loop and ascend another 15 ft. I am not saying a G motor can't work, especially since you will have battery and motor weight, but these high power motors are very violent. Be sure to compare your plane's weight to a G rocket's weight. I haven't figured out the ratio with respect to how much heavier to have the plane in comparison to a rocket using an equal motor, but the plane should be heavier. Going back to my 2 meter glider, I later tryed E sized motors, which worked a little better and they are easier to get and use. This plane eventually sustained severe fire damage as my motor mount loosened and the blast caught the bottom of the tail. I am very interested in your project, keep a rocket plane thread alive. If you are interested in my set up I would be more than happy to post some pics, just let me know.

Alex.

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/18/2006 6:41:54 PM   
TheJester


 

Posts: 76
Joined: 5/6/2006
From: Fairfield, IA, USA
Status: offline 		Sweet another pilot that is a "little off his rocker" and willing to take some risks, like me. Yes, I would be interested in seeing your set up. When you say you are launching from the ground, are you launching with a conventional system, IE: car battery, or do you have an onboard switched controled ignition system?

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/18/2006 7:11:17 PM   
RetroFlight


 

Posts: 21
Joined: 8/13/2006
From: Atlantic, IA, USA
Status: offline 		The Loop was most likely a result of off center thrust, camber air foil or CG/Cp shift. Airfoils with camber will loop so be prepared to correct for it quickly. If motor is located off of the centerline (further from CG/Cp location the more pronounced the effect) the model will loop. Best to locate the motor close to CG/Cp location or if aft of model angle the motor so the thrust line passes between the CG and CP locations. Composite motor propellant burns quickly which results in a sudden CG/CP (weight) shift in the model. If the motor is located near the aft end the shift will be more violent. Delta platforms seem to handle the CG/CP shift best and often do not require ballast dump to compensate. Straight or swept wing models may require ballast dump (water bottle) to work. Or again locate the motor close to the CG location.

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/18/2006 9:08:44 PM   
rcmaster-RCU


 

Posts: 115
Joined: 10/21/2002
Status: offline 		I have an on board ignition system. I use estes ignitors that are connected to a toggle switch which is hit with a servo arm. The switch then opens the circuit to the receiver battery which then applies power to the ignitor. I used to custom build ignitors for my F motors to ignite them in the same way. It works quite well. I will try and post pics. As for my glider, I had a rocket pod bolted right on the C.G. to eliminate weight issues. My current project is a balancing act. The receiver battery is positioned in such a way that the plane is slightly tail heavy with two full motors and slightly nose heavy with the two empty motors. I have the motors mounted in the same position as your twin jet project.

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       Post #: 11

RE: TwinJet to Rocket Propelled/Ever been done? - 8/18/2006 9:32:03 PM   
TheJester


 

Posts: 76
Joined: 5/6/2006
From: Fairfield, IA, USA
Status: offline 		Ok, I have that same type of switching set up, but you are using the power from the Receiver, not another source and it is enough to ignite? On early tests that is what caused us some difficulty as we were using a separate 9v battery and it didn't seem to have the gusto to ignite the rockets or the igniter itself. I'm trying to ignite a G79W-m motor with Aerotech 1st Fire Jr. Igniters.

Ok, next question, are eithe of you using reload kits? The reason I ask is becuase how are you running the wiring to the ignitors. I'm not using the blast cap, but I am using the delay, so I'm guessing that I can just fill in the hole at the top of the motor so flames are not shooting forward burning up my plane.

_____________________________

FMF - Time, Money, and Imagination

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RE: TwinJet to Rocket Propelled/Ever been done? - 8/18/2006 9:45:25 PM   
RetroFlight


 

Posts: 21
Joined: 8/13/2006
From: Atlantic, IA, USA
Status: offline 		I use the Jomar switch its electriclly isolated from the receiver and uses a seperate battery pack (two or more 50 mAh cells). Don't use a standard 9 volt it will not fire composite ignitors and questionable on Estes nichrome solar ignitors. Always use NiCad cells they have way more kick. The Jomar switch keeps your Rc servo from being effected by the air-start or vice-versa. Weight of the xtra battery pack is small , can be used to offset the rocket motor weight. Test out your system on the ground first to ensure it will fire the ignitor. For composites I use the Quick-Burst brand ignitors.

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       Post #: 13

RE: TwinJet to Rocket Propelled/Ever been done? - 8/18/2006 10:04:03 PM