New Member w/ Questions

[prowlerguy]

1. I have read people talk about modifying a 24mm mount to accomodate E engines. Since they are 24mm, is the only modification to strengthen the mount? Or is there some dimensional mods that need to be made? And if they are longer, how do you launch a D or fat C in them?

2. Is there a good site you can direct me to that has a good visual explanation on how reloadable engines work? There's no NAR club within a couple of hours of me, and I want to understand enough to ask decent question when I do make that long a trip.

3. I've read EMRR's review of the Gemini DC. Can anyone here give me any more feedback about ensuring dual deployment?

 

[mikeyd]

Prowlerguy, Welcome to the group.

1st the Estes E engines are longer than the D's. After you modify the mount to accept th longer engine, you put a spacer in to adjust back to the D length. If you do not have a "factory" spacer, you can make one by cutting off a length from a spent D engine. I believe the E engines are longer by about 1".

2nd https://www.aerotechrocketry.com/ has information on their site for their reloads. There are others out there, I just do not have them off the top of my head right now, others here will jump in I am sure with others.

3rd Others here may be able to help here as well as I have not built or flown the DC myself.

Once again, Welcome, and Happy Flying!

 

[rstaff3]

Don't have a link on the reloads off hand, but there might info on ROL InfoCentral https://www.rocketryonline.com/ (InfoCentral link is on the left) If you are new to the hobby and haven't seen this site, it would be useful to look through it anyway.

On the motor mount, strengthening generally isn't required for a D to E jump. Just make sure you build it well with nice glue fillets, etc. A common approach is to make the motor mount the length of the longest motor - say stretch it to accomodate the longer E9s. This actually isn't a requirement but most times people do this. Instead of a motor hook or block, just leave the tube open. Then, wrap several layers of thin masking tape around the end of the motor to make a thrust ring. Just above this, add just enough tape to make the motor fit snugly in the tube. The tape thrust ring really works well - I have used it on G's and I have heard of people using the method on HPR motors. I have used the thin layer of tape to hold the motor in on many rockets thru the years. The trick is to get it tight enough that the more pressure is required to eject the motor than the chute, without damaging the motor tube. However, I usually don't use the tape retention method and provide some other form of motor retention. ('Kaplow' clips, modified estes clips, etc.)


I can't answer the GeminiDC question.

 

[astronboy]

Hi Prowler:

I have modified a few rockets to accept the long 24mm motors. Yes, you will need to build a longer motor mount. An Estes E, and many Aerotech 24mm motors are 1" longer than a standard D. If you do not have an E engine hook, you can bend your own. Just save your old windshield wipers!! Yes, the two metal strips inside of your wiper blades are the same dimension spring steel as used for engine hooks.

A few other thoughts: An ESTES E9 motor weighs about 12 grams more than a D12-7. Just be sure that your rocket will be stable with an E engine.

If you want to be able to also launch your converted rocket with Aerotech E and F engines, I would suggest glueing in the engine mount together, and into the rocket with epoxy. The ejection charges in Aerotech motors are pretty healthy. Upon ejection, I blew the mount clear out of my 18mm Big Bertha the first time I flew it on an AT D21.


Just as Mikeyd said, if you want to fly your E bird on D or Fat C motor, just cut a 1" long section from a spent D or E motor and insert that into the mount before the motor.

 

[Prowler901]

I have the Gemini DC. She only has 4 launches on her so far. But, each one has been perfect. Both chutes have deployed each time. I was concerned on the first couple flights because the chutes seem to pack in awfully tight. But, that doesn't seem to be an issue. Here's how I usually pack them:

1. put two sheets of crumpled wadding in. Use a stick to pack them up against the vent tubes. But do not pack it beyond them.
2. Roll and pack your chute so that it is small enough to fit into the tube.
3. Pack one more sheet of wadding in the end of the tube to protect the chute from any hot particles during ignition.
   [/list=1]
   
   Like I said, it seems really tight. But, it seems to work great every time.
   
   Regards,
   Todd

 

[prowlerguy]

Thanks for all the quick replies. I appreciate the hints. I am building a Stormcaster, but I intend to use it as my "booster" for multiple payloads, the first of which is a MegaCam. I thought it might be wise to modify it to grow with its assigned missions over time.

Prowler901, I see you also were an ECMO. I was with VAQ-136 in Midway way back in '85-'88. Do we know each other?

 

[mikeyd]

if you have not been there yet go to rocketrys new web resource at

https://www.flyrockets.com

Here you will find pages and links that explain rockets, and how they work, including graphics of reloadable motors.

Happy Flying

 

[illini]

Originally posted by prowlerguy
Prowler901, I see you also were an ECMO. I was with VAQ-136 in Midway way back in '85-'88. Do we know each other?

Hey, look at all the ECMO's! Until 2 years ago I did a lot of work with the EA-6B program. Worked the study that gave birth to ICAP-III and most recently the AEA AoA (big study to determine replacement for the Prowler). Used to do Prowler related R&D at NRL. What is it with EW types and rockets?

Prowlerguy, head to a NOVAAR launch sometime. A bit of a drive for you, but you'll probably be able to get many of your questions answered.

 

[Prowler901]

Originally posted by prowlerguy
Prowler901, I see you also were an ECMO. I was with VAQ-136 in Midway way back in '85-'88. Do we know each other?

Hmmm... good question. Probobly not. I didn't go through VAQ-129 until 1990-91. But, it's great to meet a fellow member of the gliding electric light show And, I always loved the 136 patch

illini868891: Not sure why we seem to crop up here... perhaps it's cuz we could only launch the HARM. And, this is a great way to relive the fun Well, I never got to fire one myself... maybe it's just missile envy in my case

Regards,
Todd

 

[prowlerguy]

Hmmm... good question. Probobly not. I didn't go through VAQ-129 until 1990-91. But, it's great to meet a fellow member of the gliding electric light show And, I always loved the 136 patch
Regards,
Todd

Well, I taught at Corry from 1988-1991, so maybe we have met. Anyway, thanks for the help.

 

[powderburner]

Any of you guys want to venture an opinion of the proposed -18G jambird? Personally, I don't see how it can both get anywhere and do much good, because if you fill the stations with pods, there is no room for tanks, and all you can do is circle the boat a few times and it's time to recover. Looks like a dud to me.

 

[Vance in AK]

I'll give my .02 on the Gemini DC.
I read everything as far as tips go on the EMRR site(if you haven't gone there do. Many tips on that rocket as well as many others.), & built mine carefuly using the mods recomended their to make it dependable with 2 chute recovery.
First launch the main nose cone blew off & only one chute opened. Could see that there had been good coverage with plastic glue, but the NC blew off anyway. To add insult to injury, there was a pretty stout wind & the rocket drifted about 300 yds. I jumped in the van to run down the dirt road to get it & ran over the NC on the way. Saw it on the way back.
At that point I decided that the reason I liked the rocket was it's appearance, not it's recovery method. When I put it back together I made it a standard ship with normal single chute forward ejection. Less to go wrong.
To plug the gas tubes that went to the side pods at that point, I used epoxy putty (Apogee) on the end of a long applicator.
I'm sure I will build another in the future, & it will be standard recovery from the start.
That's just my approach.
Vance in AK.

 

[illini]

Originally posted by powderburner
Any of you guys want to venture an opinion of the proposed -18G jambird? Personally, I don't see how it can both get anywhere and do much good, because if you fill the stations with pods, there is no room for tanks, and all you can do is circle the boat a few times and it's time to recover. Looks like a dud to me.

I did a lot of the analysis on the AEA AoA that evaluated the Growler (I always thought "Howler" would be a better name) amongst other options. Keep in mind that the "G" is derived from the "F" which has much better range than the A-D aircraft. There are a *lot* of issues in moving to the new airframe. Some good and some not so good. I have plenty of opinions on the "G" and other alternatives we studied, and I even have numbers to back 'em up. However...in this forum I'll only say that it might make an interesting plastic model conversion some day!

 

[powderburner]

Originally posted by illini868891
the "F" which has much better range than the A-D aircraft

Yeah, I suppose the E/F does have better range than the A/B/C/D---but then anything would have better range than that turkey. However, even though the E/F has better range (after all that extra gas, and all those taxpayer $$$), it STILL does not even go as far as the A/B was supposed to go in the first place. Check the proposals if you don't believe me.

Brown stuff under your shoe is still brown stuff, even if someone calls it new.

 

[illini]

Originally posted by powderburner
it STILL does not even go as far as the A/B was supposed to go in the first place

Bottom line is that all of these issues were thoroughly studied in the AoA. All significant capabilities and limitations of all alternatives were accounted for, and suitable mission profiles were developed and vetted by a group of trained operators like the ECMO's in this thread. An AoA doesn't determine the final answer, but makes recommendations and presents all the supporting analyses so that decision makers have the facts before them. That doesn't guarantee they'll make the right decision, but they have the facts. Given that, if they settle on the Growler then they are doing so fully cognizant of the capabilities and limitations of that platform. I neither endorse nor withold endorsement of such a decision, nor is it my position to do so. My job is done when the analysis is done (how's that for being in Washington too long? )

 

[powderburner]

Believe me, I understand your comments. That's a very nice way to say: we figured out that it's a crappy platform, but it's all we have.

 

[illini]

Actually, an EA-6C *was* an option that we considered in the AoA, and we considered lots and lots of other platforms as well, including UAVs, UCAVs, commercial jets, business jets, other strike-fighters, and combinations thereof. We had no lack of alternatives. On the contrary, we had way too many alternatives and it was difficult to thin the herd on effectiveness alone. An AoA is a cost-benefit analysis, and while the cost part of it puts me to sleep (and the people who enjoy that part scare me), the reality is that cost is usually how the decisions are made. Not just, "what do we have available?" but "how much does it cost?"

One thing that you need to understand is that the threat evolves and, therefore, the requirements evolve as well. We're not trying to defeat isolated SA-2's in Vietnam anymore. If the Growler couldn't get far from the carrier it would be a non-starter as a platform. It *does* have capability, but how much must be weighed against the requirements.