Pods on Mega Der Red Max? --- GOT MY LEVEL 1 CERT

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It looks great with the swoopy parts. If it was me I would cut the outside section out of the original fin frame (Red lines). Then add a tab onto the pod holder that fits into the stock frame(Blue lines). Otherwise your add on might just pop off the fin instead of the pod popping off. Know what I mean?

pods-v2-1.jpg
 
ChrisAttebery said:
It looks great with the swoopy parts. If it was me I would cut the outside section out of the original fin frame (Red lines). Then add a tab onto the pod holder that fits into the stock frame(Blue lines). Otherwise your add on might just pop off the fin instead of the pod popping off. Know what I mean?
Click to expand...

Thanks, Chris. I'd have to figure out how I would be able to cut these shapes with any accuracy. My own selection of tools and know-how is not that great. Getting all the edges to meet up flush for a good bond could be difficult. At some point, it's going to make more sense to just ditch the existing fins and have entirely new ones laser cut! But that kind of gets away from my original idea of modifying a $25 MDRM to my liking. Hmmm... These projects sure can take on a life of their own...
 
Pod style clusters are just too cool. They give rockets that retro, Spaceman Spiff with big shiny aluminum rocket and big plastic fish tank helmet feel.
Here's a stretched and clustered Gizmo on a central J with three H54's in the fin pods. If everything goes as planned it's next flight (May 3/4,2014) will be on a central CTI K454 Classic along with three G106 Skids in the pods.



 
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Threemorewishes said:
Pod style clusters are just too cool. They give rockets that retro, Spaceman Spiff with big shiny aluminum rocket and big plastic fish tank helmet feel.
Here's a stretched and clustered Gizmo on a central J with three H54's in the fin pods. If everything goes as planned it's next flight (May 3/4,2014) will be on a central CTI K454 Classic along with three G106 Skids in the pods.

Click to expand...

That is awesome!

It does seem like with motors in the pods, there is a good potential for the rocket to go wildly unstable is they don't all light. How do you deal with that? I'd love to try something like this, just for the looks of the thing, but I don't have much experience with clusters, let alone clusters in pods.

Also, do you do anything special to protect the pods from damage on landing?
 
ThirstyBarbarian said:
That is awesome!
It does seem like with motors in the pods, there is a good potential for the rocket to go wildly unstable is they don't all light. How do you deal with that? I'd love to try something like this, just for the looks of the thing, but I don't have much experience with clusters, let alone clusters in pods.
Also, do you do anything special to protect the pods from damage on landing?
Click to expand...

Thanks for the compliment.

I only light the pods once the central motor is burnt out. This makes sure that the rocket is moving at a very good speed and is well away from the flight line before the pod motors kick in. Its maiden voyage used H54's in the pods - long burn low impulse pod motors are going to be the standard diet. The G106 Skids are probably the max average impulse I will use.

Using CTI motors that have the pressed black powder pellet at the top of the fuel stack also helps with simultaneous ignition. I'm pretty sure that the rocket would not go "wildly unstable" from one or two motors not lighting. The momentum it has from the central motor burn and its massive overweight design is quite a bit to overcome for a 29mm three grain load. If anything it would spin the whole thing.

This particular rocket is built like a tank. It sports G10 tubes and aluminum plate reinforced G10 fins. In fact it is an epoxy free design using aluminum spiders and water jet cut pod hangers. I stuff in an over sized parachute so it comes down quite slowly. It even landed upright on its maiden voyage.

Thanks for your interest.
 
Could you make them so that they stay on for the flight up, but upon landing they could pop off w/o damage?
 
Perhaps you could build in an 18 or 24mm motor mount to the pods, and attach them on some sort of dowel and rod configuration (think strap on boosters) and have it so that when the ejection charge fires, it: a) ejects the pod off of the fin and b) maybe blows off the NC for streamer or nose-blow recovery. This way you can get the pod look, cool cluster effect, and safe (if not easy) recovery of all parts of the rocket. Just and idea, not sure how well it would work ejecting the pod and some recovery device. perhaps, the pods will tumble?

Merely thinking out loud here:)

Nate
 
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I just started looking at this today. My first reaction was, "Who is this guy thinking he can improve on der Red Max!?!? Somebody oughter.....:bangpan:"
Then I saw the first picture with the leading blunt nose pod.
OK, he wins that's cool!:cool:
I like the blunt leading better than the pointy.
How about slotting the pod and leaving the fin alone? If you foamed the pod and just used a friction fit, you might be able to land hard without breaking anything, just having the pod eject on impact. Or maybe just one drop of CA glue.
 
Threemorewishes said:
Thanks for the compliment.

I only light the pods once the central motor is burnt out. This makes sure that the rocket is moving at a very good speed and is well away from the flight line before the pod motors kick in. Its maiden voyage used H54's in the pods - long burn low impulse pod motors are going to be the standard diet. The G106 Skids are probably the max average impulse I will use.

Using CTI motors that have the pressed black powder pellet at the top of the fuel stack also helps with simultaneous ignition. I'm pretty sure that the rocket would not go "wildly unstable" from one or two motors not lighting. The momentum it has from the central motor burn and its massive overweight design is quite a bit to overcome for a 29mm three grain load. If anything it would spin the whole thing.

This particular rocket is built like a tank. It sports G10 tubes and aluminum plate reinforced G10 fins. In fact it is an epoxy free design using aluminum spiders and water jet cut pod hangers. I stuff in an over sized parachute so it comes down quite slowly. It even landed upright on its maiden voyage.

Thanks for your interest.
Click to expand...

Thanks for the explanation and also for adding the other awesome picture above with all the pods lit. That is too cool!

It makes sense that even if the pod motors did not light, once the rocket is traveling fast on the central motor, the rocket would not be destabilized. I had thought they would all be lit simultaneously. Your description got me looking up air starts. I've never built anything with that capability, or used any kind of electronics for triggering events. I've only used motor ejection and never done dual deploy.

If I was interested in something like this with maybe 18 mm or 24 mm black powder motors in the pods, mostly for effect, what would be the simplest way to do it? I would not want the pod motors to light unless the central motor lit, but I'd be OK with them lighting just a second or so later. I'm thinking small motors would still make a cool effect, but would not really affect the flight of the rocket much, and maybe I could still rely on motor ejection.
 
Pods!!??

You want Pods!!??

Did you learn nothing from watching “Invasion of the Body Snatchers”?
 
After a very long break in which I made too many rockets for other people an not a single rocket for myself, I want to revive this project. In fact, I'd like to build this project in time to to fly it on September 20, so that's not a lot of time!

At this point I have decided not to do actual motor mounts in the pods --- they are just for looks. I'd like to make the shape of the fin and pod like I show in the post below, with the "swoopy" part on top, and the added piece attached to the outer edge of the fin with a tab that will go into the pod.

Can anyone help with the questions in the post below? I've highlighted the ones I am concerned about in RED.

It basically boils down to: Will the joint in the fin be strong enough? Will the rocket still be light enough to fly on a G80 or similar motor?

EDIT: It looks like the pictures from the quoted post do not show here. The post with the pics is #29. Heres a link: https://www.rocketryforum.com/showt...-Pods-on-Mega-Der-Red-Max&p=688241#post688241



ThirstyBarbarian said:
Finally, the post editor works again... So here is a new mockup I've been waiting all day to post.

The picture below shows the shapes of pieces I could use to adapt a variation on what Terrg suggested. Instead of cutting into the existing fin, this would involve adding a new triangle of plywood to the end of the fin. The triangle has a tab on it that I would insert through a slot in the pod tube and glue to the inside wall of the pod tube. There is also another small piece that I could add to the top of the fin to make it more "swoopy" --- I'm still undecided about that.

View attachment 167015

Below, the near fin shows all the mockup pieces taped together.

View attachment 167016

Here it is without the swoopy piece.

View attachment 167017

So waddaya think?

The fins are pretty wide this way. Once I add the extra plywood and the skins over the whole thing, is it going to be too heavy and draggy for a G motor? Does anyone know how to simulate a design like this?

And are fins made this way going to be strong enough? If I glue the edges of the plywood together and use a one-piece skin over the whole flat surface of the fin, will that joint where the ply pieces meet be strong? The supplied material for laminating the fins is balsa, but I doubt the sheets are big enough to cover all the pieces I am adding, so I can go for something more robust.

And how about the aesthetics? Wide fins or less wide? Swoopy or not?

Thanks, everyone!
Click to expand...
 
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I've started building this rocket and I'm hoping to fly it on September 20, about a week and a half from now. In order to do that, I'll need a motor. The first flight will be at a field with a G motor limit and a 1,000 foot ceiling. Does anyone have a recommendation for a single-use G?

Unfortunately the rocket is not built yet, so I do not have a final weight, but it will definitely be heavier than stock. The unfortunate thing is I will have to order the motor immediately to get it in time, but the rocket isn't complete yet, so I can't weigh it.

Estes recommends G40-7W and G80-7T for the stock MDRM. What do you think of these impulses and delays in a MDRM that will be heavier than stock? Does the G40 have enough initial thrust to get this rocket moving, or does something like the G80 make more sense? On the delay, will 7 seconds be too much if the rocket has more weight and drag than the stock rocket?

I know it's impossible to answer these questions without the final weight, but in general, does a G40 have more than enough thrust to get a stock MDRM moving, with margin to spare, or is it on the edge and not suitable for anything heavier? Is a 7-second delay perfect for a stock MDRM, or is it usually a little bit late?

I'm also open to suggestions for other SU motors. It may make sense to order something with a drillable delay that I can adjust after a final weight.

Let me know your thoughts!
 
I think I want to fill the pods with 2-part foam. Hobby Lobby has Alumilite 320, which is described as 3-pound density foam. Is that going to be what I want? The rocket will probably land on one of the pods, so I want them to be as tough as possible.
 
Your'e not really limited to the stock motors. G78G, and the G77R both should work, and they have a bit less impulse than the G80. So far I have only flown mine on F50-4s at moffet, which I would say is around 400-500 feet maximum height.

The F50 is pretty much the lowest impulse I would fly in a stock built one, and the G80 might be a bit more impulse than you can fly at moffet. As for delay, it's kind of hard without a sim but most people who fly them on G's use the 7 second delay, rocksim says deployment on a 4 second delay is too fast. even with the extra weight you'd probably be safe, but if you have rocksim try adding the pods. The drag of the pods should matter more than weight.

Regarding your last post, I'm not sure about foam, but you want to glue the fins and on with epoxy. Last month at moffet a fin fell off on landing on mine, which was glued using titebound. I removed all the fins and re-glued them with epoxy.

Finally, I would definitely recommended using a Nomex, and rail buttons.

Good luck on the build!

Edit: looking back at the design from the first page again, I think you might be able to fly a 4 second delay on this. Maybe a G77R, which has considerably less impulse than a G80?
 
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SCrocketfan said:
Your'e not really limited to the stock motors. G78G, and the G77R both should work, and they have a bit less impulse than the G80. So far I have only flown mine on F50-4s at moffet, which I would say is around 400-500 feet maximum height.

The F50 is pretty much the lowest impulse I would fly in a stock built one, and the G80 might be a bit more impulse than you can fly at moffet. As for delay, it's kind of hard without a sim but most people who fly them on G's use the 7 second delay, rocksim says deployment on a 4 second delay is too fast. even with the extra weight you'd probably be safe, but if you have rocksim try adding the pods. The drag of the pods should matter more than weight.

Regarding your last post, I'm not sure about foam, but you want to glue the fins and on with epoxy. Last month at moffet a fin fell off on landing on mine, which was glued using titebound. I removed all the fins and re-glued them with epoxy.

Finally, I would definitely recommended using a Nomex, and rail buttons.

Good luck on the build!

Edit: looking back at the design from the first page again, I think you might be able to fly a 4 second delay on this. Maybe a G77R, which has considerably less impulse than a G80?
Click to expand...


Thanks for the info. The G77R is one of those that I have in mind. The delay is going to be the tricky thing. I'm not sure how to simulate it. I have OpenRocket, but I have not looked at how to add pods to the design, if that is even possible in OR.

Also, I'm thinking about maybe getting a larger chute for landing on concrete at Moffet.
 
ThirstyBarbarian said:
Thanks for the info. The G77R is one of those that I have in mind. The delay is going to be the tricky thing. I'm not sure how to simulate it. I have OpenRocket, but I have not looked at how to add pods to the design, if that is even possible in OR.

Also, I'm thinking about maybe getting a larger chute for landing on concrete at Moffet.
Click to expand...

I've currently got a decent amount of time on my hands, and looking to spend it on a rocketry project, so if send me your base OR file and pod dimensions, I could try to hack it together for you.
 
Hnefi said:
I've currently got a decent amount of time on my hands, and looking to spend it on a rocketry project, so if send me your base OR file and pod dimensions, I could try to hack it together for you.
Click to expand...

That's a great offer! I haven't started an OR file on this yet, but let me see what I can do. It might have to be later tonight or tomorrow.
 
I just checked my motor supply, and I have a few G40-4 motors that I got at the Fry's clearance. They had a bunch of these short delay motors and I got a few thinking maybe the MDRM could use the shorter delay. But now I've added the pods extra fin material, and I think the rocket is now too heavy for these motors.

I just weighed all the components, and it adds up to 38.5oz, and that is without glueing on fins, MMT, or pods. It is also before the foam in the pods and the primer and paint. Maybe it will be 45 ounces?

45 ounces is too heavy for a G40, correct?
 
G40 peaks at 19 lbs of thrust, or 84n, it just drops off quickly to lower thrust. Should actually be enough for a 2.8 pound rocket, but openrocket should be able to verify it leave the launch pad at a least 40-45 ft/s. A 4 second delay should be good if it's really 2.8 lbs, my stock one is 1.8 lbs without recovery setup for reference, so the pods must add a lot of weight. What motors do you have besides G40-4's? Based on that weight, any 4 second G with lots of thrust will probably work.

You probably want a bigger chute if it's going to weigh almost 50% more than a stock MDRM, just so it doesn't get damaged on landing.
 
SCrocketfan said:
G40 peaks at 19 lbs of thrust, or 84n, it just drops off quickly to lower thrust. Should actually be enough for a 2.8 pound rocket, but openrocket should be able to verify it leave the launch pad at a least 40-45 ft/s. A 4 second delay should be good if it's really 2.8 lbs, my stock one is 1.8 lbs without recovery setup for reference, so the pods must add a lot of weight. What motors do you have besides G40-4's? Based on that weight, any 4 second G with lots of thrust will probably work.

You probably want a bigger chute if it's going to weigh almost 50% more than a stock MDRM, just so it doesn't get damaged on landing.
Click to expand...

Other than the G40-4's I really do not have any other motors that I think will work at all --- some G40-7's and a few Econojet F's with too little thrust.

It would be great if the G40-4's would work with this rocket. The Thrustcurve quick and dirty simulation has it off a 7-foot rail at 40 ft/s. I am looking at maybe buying a G77R-4 or G78G-4 for a more reliable flight (46 ft/s and 49 ft/s off the rail). Hobbylinc does not have any G79's but I think I would like that motor (42 ft/s). They also do not have any G80's with a shorter delay.

Do you know how long the rails are at Moffet?

I am definitely going to look at a bigger chute. I don't want to smash this rocket on the concrete!
 
I actually don't know how long the rails are at moffett, I think they are 6 ft or 7 ft... In no wind it might work.
 
Does anyone have any advice related to chute size for a rocket like the MDRM landing on concrete?

Does the stock 32-ounce MDRM on a stock 30" parachute do OK at Moffet, or is a larger chute in order? I went to Rocket Reviews to use their descent calculator, and the recommendation for a 32-ounce rocket is a 40" chute! The recommendation for a 45-ounce rocket is 47"!!!

That seems really big!

These sizes would give a descent rate of under 16 feet per second (under 11 MPH). What is a safe speed for a rocket with big fins landing on concrete? Does it have to be that slow or can it be a bit faster? I don't want to crush anything, but I also don't want it to drift away on the breeze, and I don't want to buy an overly large chute if I don't need one that big.

Here are some calculated descent rates for a 45-ounce rocket:

30" (stock) = 24.7 fps
36" = 20.6 fps
40" = 18.5 fps
48" = 15.4 fps
 
SCrocketfan said:
I actually don't know how long the rails are at moffett, I think they are 6 ft or 7 ft... In no wind it might work.
Click to expand...

I'm thinking they are probably 6 feet. I've never used them, but that seems like a pretty standard length.

I think I probably ought to go with something with a little more kick on the first flight, just to get a feel for the rocket.
 

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