Engines opinions needed.....

[Rocket_Man]

So I am building this Valkryie PMC and I need some help / opinions on the engines. The plane is 3ft long 18 inches wide and will weigh somewhere around 24 - 28 ozs.

For simplicity I am just going to use Estes engines.The main body tube 24mm for a D or E engine.

Now I think I am going to add 2 more engines, one on either side of the main engine. This is where the problem comes in.
I know a E9 is a slow burning engine so to get the plane off the pad quickly I was going to add 2 D12's on either side of the E9.

But is that way too much ???

Should I go with 3 D12's ? A D12 in the middle with C6 or C11 on either sides ?
Or maybe an E in the middle with C6's or C11's on the sides.

I am leaning toward the middle being an E9 with 2 D12's on wither side. I am really concerned that 2 C6's on either side of the E9 are not going to contribute that much. Am I over-powering this thing or not ?

 

[[POW]Eagle159]

I think that an E and 2 D's would be enough, but 2 C's might be a little less weight. Then if it flys on that you could use D's, but that is a lot of power... if one doesn't light than ...:cry: not good

 

[Rocket_Man]

what about 3 D12's ?

 

[GregGleason]

The XB-70 had six engines, all line abreast. Are you keeping this configuration for the PMC?

If so, having an odd-numbered motor arrangement wouldn't work because you would have asymmetrical thrust. You can have an even-numbered motor arrangement. But the motor types would have to mirror each side away from the aircraft's centerline axis.

For example:

Arrangement 1:

Empty-Empty-D12-D12-Empty-Empty
​

Arrangement 2:

Empty-C6-D12-D12-C6-Empty
​

This only applies if you are keeping this arrangement.

Greg

 

[[POW]Eagle159]

The XB-70 had six engines, all line abreast. Are you keeping this configuration for the PMC?

If so, having an odd-numbered motor arrangement wouldn't work because you would have asymmetrical thrust. You can have an even-numbered motor arrangement. But the motor types would have to mirror each side away from the aircraft's centerline axis.

For example:

Arrangement 1:

Empty-Empty-D12-D12-Empty-Empty
​

Arrangement 2:

Empty-C6-D12-D12-C6-Empty
​

This only applies if you are keeping this arrangement.

Greg

Wow that is a BIG plane :y:
I don't think that he is using the plastic planes engines exhaust/afterburner to place the rocket engines in though... but that is what I think :confused2:

 

[Rocket_Man]

no, i am going with 3 24mm engine mounts centered down the middle. i am thinking a d12 in the middle and 2 c11's on either side for test launch. 6 engines would have been crazy and running 3ft of engine / body tube going from 6 engines routing to 1 tube would have been crazy.

as it sits i just need to hook the nose cone on n do my COP n CG calculations n its ready to go.

thanks for the great pictures, i know its supposed to be white n am going to paint AFTER my first launch!

 

[Marc_G]

Rocket Man,

I so love your PMC threads!

I haven't moved up to these weighty models but I like the idea of having three 24 mm tubes to work with.

I have a question though: I know you said you are sticking with Estes engines (OK, cheap, locally available via coupons at HL!), but given the effort and probably expense of these (BEAUTIFUL) models, wouldn't it make sense to consider maybe some Aerotech engines that give higher thrust in 18 and 24mm packages?

Whatever you decide, I look forward to the video. Given these models already have some weight to them, have you considered a pair of keychain cams pointing forward and aft? Might make for some impressive results!

Marc

 

[MarkII]

How about a central D12 flanked by two D11s? The Estes D11-P is a nice motor.

Re: composite motors... I have never done a plastic model conversion, but I imagine that I really wouldn't want to send one to 1,800 ft.

 

[Rocket_Man]

Hey Marc,

These PMC planes / rockets might be a little heavier than a rocket but I think they are more aerodynamic so once they get going they are definitely....missiles....I am very surprised at how fast they go. That 1st plane the F-106 Delta Dart I launched with a D12 went straight up and checked-out. It was moving so fast I couldnt track it with the camera. So dont be put off by thinking they weigh too much to be fun.


As far as the number of engines on the Valkyrie, I want to have the 2 engines on either side of the middle main engine to counter some thrust alignment "needs" that I perceive. Nothing major, just want some counter-balance thrust to offset the main engine by a little bit.

As far as the Aerotech engines...... the bottom line is the Valkyrie and the Stiletto are only going to launch once or at most twice. I built them just to see if I could. Too much work there to lose em to something. So I have no use to buy re-loads.


i am going to do a 2 stage launch of the Stiletto this week oint:

 

[MarkII]

Hey Marc,

These PMC planes / rockets might be a little heavier than a rocket but I think they are more aerodynamic so once they get going they are definitely....missiles....I am very surprised at how fast they go. That 1st plane the F-106 Delta Dart I launched with a D12 went straight up and checked-out. It was moving so fast I couldnt track it with the camera. So dont be put off by thinking they weigh too much to be fun.


As far as the number of engines on the Valkyrie, I want to have the 2 engines on either side of the middle main engine to counter some thrust alignment "needs" that I perceive. Nothing major, just want some counter-balance thrust to offset the main engine by a little bit.

As far as the Aerotech engines...... the bottom line is the Valkyrie and the Stiletto are only going to launch once or at most twice. I built them just to see if I could. Too much work there to lose em to something. So I have no use to buy re-loads.


i am going to do a 2 stage launch of the Stiletto this week oint:

Vid-e-os man, vid-e-os! Must post videos! Or launch pictures at least. I have never seen a launch of a PMC. :cyclops:

 

[Rocket_Man]

How about a central D12 flanked by two D11s? The Estes D11-P is a nice motor.

Re: composite motors... I have never done a plastic model conversion, but I imagine that I really wouldn't want to send one to 1,800 ft.

yea, i think you are right mark. i think i will end up with D12 center and 2 C11's for outers. after adding nose weight will check weight and adjust. but it is finished, just need to do COP & CG and find the nerve to press the button.