3 Stage Rocket

[bringrose]

Hey,

I'm currently designing a model rocket and would like to make it 3 stages and have a few questions and concerns. First is it even possible to do 3 stages and if so is it anything like 2 stages? Second when using this much power should I be considering the weight of the rocket? And lastly do the first 2 stages need to break away or can they just fall out of the tube?

Any help is much appreciated!

Ben

[stefanj]

Ben:

Three stage rockets are nowhere near as common as two-stagers, but people have built them and there have been commercial three-stagers.

I strongly suggest looking at existing designs, and to read the Estes technical report on staging.

This PDF ("The Classic Collection") contains the mulitstaging technical report:

http://www.esteseducator.com/Pdf_files/1976clas.pdf

This page has links to scanned in Estes plans. Look up the Farside and the Comanche-3:

http://www.dars.org/jimz/estes.htm

[Mark II]

Hey,

I'm currently designing a model rocket and would like to make it 3 stages and have a few questions and concerns. First is it even possible to do 3 stages and if so is it anything like 2 stages? Second when using this much power should I be considering the weight of the rocket? And lastly do the first 2 stages need to break away or can they just fall out of the tube?

Any help is much appreciated!

Ben
I'm sure that other forum members will have much more to say on this subject, but the quick answers to your first (2-part) question is yes and yes. Both Estes (the Comanche-3 (http://www.estesrockets.com/rockets.php?pid=001382)) and FlisKits (the Nomad (http://www.fliskits.com/products/rocketkits/kit_detail/nomad.htm)) offer 3-stage rocket kits. The answer to your second question about the weight of the rocket is the biggest issue right now with designing and building 3-stage rockets that fly on black powder motors, but this wasn't always the case. You have to be very careful in designing and constructing your 3-stager so that the low- to medium-thrust black powder motor (those are the only kind that are being made right now) in the first stage has enough power to get the entire stack going at a stable speed.

Your third question asks whether any design requires drop-staging or if it is possible to employ CHAD-staging. I don't know of anyone who has ever done CHAD-staging of 3 motors in a single motor tube; I would think that the exhaust plume of the second, and especially the third, motors would incinerate the motor tube as they fired. Drop-staging, in which parts of the rocket (not just spent motors) are dropped as each stage fires, is the only method that I know of for a 3-staged rocket, although CHAD-staging is sometimes done with 2-stagers.

In the 1960's and early 1970's, there was once another method of direct staging of black powder motors that was tried, which also had all of the motors contained in a single motor tube, but it was abandoned because the method was highly prone to CATO's. That's all that I'm going to say about it, too.

Mark \\.

[Mark II]

I neglected to mention another 3-staged rocket, the Cyber III. This was not a kit but rather was a design and plan published by Semroc Astronautics back in May, 1970 (http://www.ninfinger.org/%7Esven/rockets/catalogs/semroc570/570semroccat.html) (first page. (http://www.ninfinger.org/%7Esven/rockets/catalogs/semroc570/570semroc4.jpg) second page (http://www.ninfinger.org/%7Esven/rockets/catalogs/semroc570/570semroc6.jpg)). John Lee (JAL3) has an ongoing build thread for his version of this rocket on TRF (http://www.rocketryforum.com/showthread.php?t=47728&highlight=Cyber+III), and I have also recently built this rocket. My RockSim 8 simulation demonstrates that this design is indeed flight-worthy on currently available motors, but I have not actually flown mine yet.

Mark \\.

[STRMan]

That's all that I'm going to say about it, too.

"Those who fail to learn from history are doomed to repeat it" Sir Winston Churchill

Please elaborate my friend. Inquiring minds (well, at least one ;) ) want to know.

[ghrocketman]

Don't forget the Centuri Arrow-300 and the Centuri T-Bird.
Both are 3-stage designs that were commercial kits.

[Doug Sams]

Hey,

I'm currently designing a model rocket and would like to make it 3 stages and have a few questions and concerns. First is it even possible to do 3 stages and if so is it anything like 2 stages? Second when using this much power should I be considering the weight of the rocket? And lastly do the first 2 stages need to break away or can they just fall out of the tube? Ben,

It sounds like you haven't done any staging yet. I suggest you get a basic 2-stager and get some experience with that first. Much of what you learn there will apply to 3-stagers.

I do mostly scratch-building, so I'm at a loss to recommend a kit; otherwise I would give you a link. Sorry.

Doug

.

[CPMcGraw]

Hey,

I'm currently designing a model rocket and would like to make it 3 stages and have a few questions and concerns. First is it even possible to do 3 stages and if so is it anything like 2 stages? Second when using this much power should I be considering the weight of the rocket? And lastly do the first 2 stages need to break away or can they just fall out of the tube?

Any help is much appreciated!

Ben

Ben,

Welcome to our asylum!

Have you had a chance to pick up a copy of Stine's Handbook (http://www.amazon.com/Handbook-Model-Rocketry-7th-Official/dp/0471472425/ref=sr_1_4?ie=UTF8&s=books&qid=1219336940&sr=8-4)? The questions you ask are (almost) right off the pages of that book.

My first recommendation is to order a copy and read it completely, then keep it at your design desk for reference.

The second recommendation is to download the DEMO of RockSim (http://www.apogeerockets.com/rocksim.asp)and just play around with it, adding and removing basic components to a simulated version of your design until you achieve what looks good and flies acceptably. The Handbook gives you the background information, while RockSim lets you see theory become practice. It will reinforce what you learn from the book.

[Shreadvector]

I think I have a few Super Samuri kits left. I have not bagged any new kits in a while.

Read all about multi-staging in the Estes Classic Collection:

http://www.esteseducator.com/Pdf_files/1976clas.pdf

If anyone is seriously interested, e-mail me.

http://www.geocities.com/fredeshecter/prdctinf.pdf

[Green Dragon]

Your third question asks whether any design requires drop-staging or if it is possible to employ CHAD-staging. I don't know of anyone who has ever done CHAD-staging of 3 motors in a single motor tube; I would think that the exhaust plume of the second, and especially the third, motors would incinerate the motor tube as they fired. Drop-staging, in which parts of the rocket (not just spent motors) are dropped as each stage fires, is the only method that I know of for a 3-staged rocket, although CHAD-staging is sometimes done with 2-stagers.
\\.

OK, going to answer this two ways, lol ...

1) as for chad staging - this being where you just hang the booster motor out inthe airstream behind a single stage rocket - done this many times 2 stage. including drop staged clusters ( ie: 3 x D12's glued together in parrallel, dropped off a singe D12 upper stage :)
However. I can say firsthand that the Estes Maxi Alpha 3 can be tripple stage chad staged, but not reccomended.. mine flew fine 3x D12's hanging out in the wind, but if any wind might weathercock, do to the slow liftoff wieght on a D12, if ,say an FSI D20 or similar was available for th elowest stage, go for it :)

2) there is a concept called a ''rack rocket' wherein motors just kick back out of a slotted / vented tube - I have flown 5 stage D12's in an Achilles rack rocket design ( see the Oct or Dec 1985 Tripolitan for plans )
Much fun, need to build another one :)

but yeah, get some experience wiht 2 stagers, and start with plans or a KIT before tackiling anyhting more extreme .

~ AL

[snaquin]

2) there is a concept called a ''rack rocket' wherein motors just kick back out of a slotted / vented tube - I have flown 5 stage D12's in an Achilles rack rocket design ( see the Oct or Dec 1985 Tripolitan for plans )
Much fun, need to build another one :)

~ AL

AL

I had posted a link to an interesting article for another forum member a while back that was written by Ken Good called "The Rack Rocket Concept - The Quest For High Altitude".

The link is contained in this post

http://forums.rocketshoppe.com/showpost.php?p=15869&postcount=22

A three stage rack rocket would be a fairly simple build.

.

[STRMan]

All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought. Due to the weight of this model, and it's engines, the ONLY recommended engine to use in the first booster is a B-14. We know we won't see any of them any time soon. I wonder how long the rod would have to be to boost this on a B6-0 or C6-0 to get it up to a stable speed.

http://i85.photobucket.com/albums/k65/STRMan/1971CenturiTBird.jpg

[Ltvscout]

All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought.
Let's keep our fingers crossed that Carl can find a source for CPT-10. Then we can have Semroc kits of the long awaited Payloader II and the T-Bird!

[Shreadvector]

Use a C11-0 or D12-0 in the booster, but verify the stability. I suspect the C11-0 will be OK.



All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought. Due to the weight of this model, and it's engines, the ONLY recommended engine to use in the first booster is a B-14. We know we won't see any of them any time soon. I wonder how long the rod would have to be to boost this on a B6-0 or C6-0 to get it up to a stable speed.

http://i85.photobucket.com/albums/k65/STRMan/1971CenturiTBird.jpg

[STRMan]

Use a C11-0 or D12-0 in the booster, but verify the stability. I suspect the C11-0 will be OK.

I can live with that. Just modify the lowest booster for a 24 mm mount. I'm completely embarrassed that slid by me. I was thinking this was a minimum diameter rocket, but I can see it is not right in the catalog. Thanks.

[Doug Sams]

All this talking about 3 stagers got me pining after a Centuri T-Bird. What a cool rocket to clone, I thought. Due to the weight of this model, and it's engines, the ONLY recommended engine to use in the first booster is a B-14. We know we won't see any of them any time soon. I wonder how long the rod would have to be to boost this on a B6-0 or C6-0 to get it up to a stable speed.[/IMG]Fred's right - rig it to take a 24mm motor in the 1st stage (ala the Comanche).

I'd make a bunch of other changes in the passport stuff, too. It need not be that complicated or heavy. And I'm skeptical of its reliability as well. Why have vents if they don't open until after the stages begin to separate?

Doug

.

[STRMan]

Fred's right - rig it to take a 24mm motor in the 1st stage (ala the Comanche).

I'd make a bunch of other changes in the passport stuff, too. It need not be that complicated or heavy. And I'm skeptical of its reliability as well. Why have vents if they don't open until after the stages begin to separate?

Doug

.

The passport staging always works perfectly on my Centuri Stiletto. I think the concept is that as the booster starts to separate from the sustainer, the hole become exposed, releasing some pressure. This slows down the separation of the booster long enough for the sustainer to ignite. In the passport staging setup, the engines are in direct contact with each other, so there is no place to have a vent anyway.

When I made an upscale of the Stiletto, I used traditional vent holes, as the engines were now gap staged about an inch apart.

[Doug Sams]

The passport staging always works perfectly on my Centuri Stiletto. I think the concept is that as the booster starts to separate from the sustainer, the hole become exposed, releasing some pressure. This slows down the separation of the booster long enough for the sustainer to ignite. In the passport staging setup, the engines are in direct contact with each other, so there is no place to have a vent anyway.Looking at the plans for the T-Bird, there's a 1/4" gap between the 1st and 2nd stage motors. It does appear the 2nd stage motor abuts the sustainer.

I agree the vent opening will relieve the pressure and thus help slow the separation - or at least prevent it from gaining any more speed - but it still strikes me as klunky and suspect. That said, I haven't tried it, so I gues I shouldn't knock it :)

Doug

.

[Mark II]

"Those who fail to learn from history are doomed to repeat it" Sir Winston Churchill

Please elaborate my friend. Inquiring minds (well, at least one ;) ) want to know.
Well, OK. I never actually saw anyone use this method, and I don't recall what it was called. I learned about it when it was discussed in a thread on the Oldrockets Yahoo! group a couple of years ago. This method of staging involved joining booster motors and a sustainer motor end to end in the same manner as in direct staging, but bonding them together with epoxy instead of joining them with tape. The permanently joined motors would all fit into one long motor tube, with the nozzle of the rearmost booster motor (1st stage motor) being positioned in the usual place at the aft end of the rocket (and not hanging off the back, as in CHAD staging), with the rest of the motor stack extending well up into the rocket. With the motors permanently attached to each other, none of them would drop off as they burned out. Instead, the next motor would fire right through the (supposedly) empty motor casing(s) of the previously burned motor(s).

Just thinking about this for a second, you can well imagine how anyone using this method is really begging to get a CATO. Sure, MOST of the BP propellant is gone once the motor is burned, and there is a wide open passage for the next motor's exhaust to blow through. But there is still a fair amount of burnt residue left in the spent motor's case, and apparently it is all too easy for the next motor's exhaust to dislodge a chunk of that residue and send it down to the nozzle where it will sometimes block the exit port. Blocked nozzle exit port = CATO, every time. And a burning stack of permanently joined BP motors that experiences a blockage in its nozzle's exit port becomes the equivalent of a pipe bomb.

Regarding rack staging: I have heard the term, but I have never gotten a handle on how it works. Is there a diagram somewhere of the setup that also illustrates the whole staging process?

Mark \\.

[shockwaveriderz]

AL

I had posted a link to an interesting article for another forum member a while back that was written by Ken Good called "The Rack Rocket Concept - The Quest For High Altitude".

The link is contained in this post

http://forums.rocketshoppe.com/showpost.php?p=15869&postcount=22

A three stage rack rocket would be a fairly simple build.

.

I agree with you Steve. Rack staging is much more effcient than nomal staging.... but a method needs to eb developed that allows the engine casings to fall with an attached deployed streamer for safety.

terry dean

[shockwaveriderz]

Well, OK. I never actually saw anyone use this method, and I don't recall what it was called. I learned about it when it was discussed in a thread on the Oldrockets Yahoo! group a couple of years ago. This method of staging involved joining booster motors and a sustainer motor end to end in the same manner as in direct staging, but bonding them together with epoxy instead of joining them with tape. The permanently joined motors would all fit into one long motor tube, with the nozzle of the rearmost booster motor (1st stage motor) being positioned in the usual place at the aft end of the rocket (and not hanging off the back, as in CHAD staging), with the rest of the motor stack extending well up into the rocket. With the motors permanently attached to each other, none of them would drop off as they burned out. Instead, the next motor would fire right through the (supposedly) empty motor casing(s) of the previously burned motor(s).

Just thinking about this for a second, you can well imagine how anyone using this method is really begging to get a CATO. Sure, MOST of the BP propellant is gone once the motor is burned, and there is a wide open passage for the next motor's exhaust to blow through. But there is still a fair amount of burnt residue left in the spent motor's case, and apparently it is all too easy for the next motor's exhaust to dislodge a chunk of that residue and send it down to the nozzle where it will sometimes block the exit port. Blocked nozzle exit port = CATO, every time. And a burning stack of permanently joined BP motors that experiences a blockage in its nozzle's exit port becomes the equivalent of a pipe bomb.

Regarding rack staging: I have heard the term, but I have never gotten a handle on how it works. Is there a diagram somewhere of the setup that also illustrates the whole staging process?

Mark \\.

Mark:

this was called originally called ganged motors in the early 60's when Doug Frost first researched the idea and later in the 70's called tandem motors.... and the reports of CATo's everytime wasn't true. Our own Trip Barber back in 1978 when tamdem motors were allowed, did an extensive R&D study(which I just so happen to have) and he found out that if they were glued together in a certain way with a outer sleeve, and the lower motor engine was either equal to or greater than the nozzle size for the upper motors, and the total thrust duration of both engines was < 2 sec approx, then the motors would work just fine.

In fact in 1978, when Trip did this R&D report it just so happened that he was also Chairman of the NAR S&T and he actually allowed these tandem motors to be used in NAR competition as they had an advantage over staged models. Unfortunately, then new NAR President J. Patrick Miller, stretching NFPA regulations to say that tandem motors were "being manufactured" by the people who glued them together and statements from Estes that ths was not an intended use, immediately overruled Trip and Tandem motors were no more.

I started a thread on this topic a few months back on TRF:

http://www.rocketryforum.com/showpost.php?p=535348&postcount=1

no need for it to be repeated here. Since the TRF post I received the Trip Barbers reports but I could nver locate Doug Frost to get his early 60's R&D report, but it was just a older version fo what Trip did with an electronic test stand versus a mechanical test stand that Doug Used.
terry dean

[STRMan]

Thanks for elaborating Mark, and thanks for your input Terry.

[Mark II]

Thanks, Terry. That conclusion goes against my intuition, but that's what research is for, right? :D I missed your recent thread on TRF, and I was, instead, just summarizing the information that I could recall from the Oldrockets thread. That earlier thread did stick out in my memory because I had never heard of the technique until then. At first blush, it struck me as being quite ingenious, until I read the comments about CATOs that followed in the thread. Trip Barber's research report obviously carries the most weight regarding this issue, though.

One clarification about my post though. When I said "CATO, every time" I was specifically referring to the effects of a blocked nozzle exit port, and was not saying that this was the inevitable result of tandem staging. (The complete sentence was "Blocked nozzle exit port = CATO, every time.") What I did say in that post was that I thought the technique had a significant tendency to produce CATOs, but I was not saying that such a result was inevitable. This is all moot now, anyway, because you have provided me with information that has caused me to modify my earlier take on the subject.

Mark \\.

[Bob Kaplow]

I thought the reason for the demise of tandem motors was that a certain manufacturer said that this was not "use as intended by the manufacturer"...

[Shreadvector]

I thought the reason for the demise of tandem motors was that a certain manufacturer said that this was not "use as intended by the manufacturer"...

Yes, and that was after NUMEROUS motor failures or catos (not CATOs since the abbreviation is not an acronym). The firing of the upper stage motor through the lower stage motor reodes the inside of the lower motor casing. This results in more mass being accelerated out the lower nozzle which results in 10% higher thrust throughtout the entire upper stage motor burn. The lower casing will burn through the side with longer burning upper stage motors (C6-0 to C6-5 or -7, D12-0 to D12-5 or -7).

This was a safety issue.

And, yes, epoxying two motors together and epoxying a sleeve over them to form a secondary outer casing is indeed "manufacturing" and the outer casing and epoxy has not been certified/tested and there is no quality control, so it makes sense that they are not allowed/certified/covered by NAR insurance.

[tbzep]

Were these sleeves just heavy paper rolled with epoxy onto the tandem assembly to build an extra heavy wall? I guess an old BT-20 tube (modern motor mount tubes are puny in comparison) and epoxy would give some strength without having to roll anything, or maybe use a 24mm blank casing, but they fit slightly loose and you'd need the epoxy to completely seal between the 18 and 24mm casings. Just curious. :cool:

[Shreadvector]

Were these sleeves just heavy paper rolled with epoxy onto the tandem assembly to build an extra heavy wall? I guess an old BT-20 tube (modern motor mount tubes are puny in comparison) and epoxy would give some strength without having to roll anything, or maybe use a 24mm blank casing, but they fit slightly loose and you'd need the epoxy to completely seal between the 18 and 24mm casings. Just curious. :cool:

it was a sleeve of regular body tube, like BT-20 or BT-50. Obviously that presented a problem for the airframe body tube or motor mount tube for the new and larger diameter motor assy, so most folks used CMR RB-74 for the motor sleeve and RB-77 for the body tube.

Thin wall cardboard tubes with epoxy slathered on by average Americans is not a reliable high quality motor casing.

There is no need for this now, as there are double the power motors in the same size and weight. They are called "Aerotech". :D

[ghrocketman]

As far as I'm concerned, unless one is boring into the propellant of an existing motor to create a port burner, it should NOT be considered manufacturing and it should be allowed.
The cato rate should have zero impact on this.
Gluing motors together is no different than taping them together for staging. it is NOT motor manufacturing and I'm sure even the BATFE would agree with that.

Once one gets into packing BP propellant or drilling cores, THAT is manufacturing.

I'd even see removing clay end plugs from E15-P, E9-P and A10-PT engines to create boosters as perfectly acceptable.
One is NOT manufacturing anything.

My attitude toward this is probably why I never joined the NAR with it's too-many-regs and why I almost always choose to fly on my own private land. I could care less when a motor cert expires or if has ever existed.

[Shreadvector]

It alters the performance.

It alters (increases) the pressure of the lower motor casing.

The thin sleeve must function as part of the motor casing to retain pressure, so that makes it part of the newly re-manufactured motor assy. IF and only if a manufacturer submitted tandem motor kits including the sleeves, to a recognized certification authority and had them tested and passed, could they legally be used as Model Rocket Motors.

RMS motors are tested and sold as a system. Delay adjustment is tested and approved.

This is all very clear and logical to me.

As far as I'm concerned, unless one is boring into the propellant of an existing motor to create a port burner, it should NOT be considered manufacturing and it should be allowed.
The cato rate should have zero impact on this.
Gluing motors together is no different than taping them together for staging. it is NOT motor manufacturing and I'm sure even the BATFE would agree with that.

Once one gets into packing BP propellant or drilling cores, THAT is manufacturing.

I'd even see removing clay end plugs from E15-P, E9-P and A10-PT engines to create boosters as perfectly acceptable.
One is NOT manufacturing anything.

My attitude toward this is probably why I never joined the NAR with it's too-many-regs and why I almost always choose to fly on my own private land. I could care less when a motor cert expires or if has ever existed.

[shockwaveriderz]

I thought the reason for the demise of tandem motors was that a certain manufacturer said that this was not "use as intended by the manufacturer"...

Bob< that was 1/2 of the reason. The other half was as I stated above: J. Patrick Miller decided that the cat of gluing 2 motors together to make a tandem motor was 'manufacture" and that violated the NAR Safety Code and NFPA regulations.

Check your copies of Model Rocketeer for 1978.

In hindsight, it appears this was just a power play by a then new NAR president to show who was in charge.

Its also just another example of how the NAR used its safety code and NFPA regulations to control model rocketry.

terry dean

[ghrocketman]

I stand by my original statements and re-state that this is NOT motor manufacturing and I could care less if it ALTERS the motor performance.
Even the agents at BATFE are SMART enough to surmise that gluing motors together no more constitutes motor manufacturing than taping them does.

Pure horse-pucky to punish the innovative all in the mamby-pamby name of safety.
Typical over-regulation....I would always rather have ZERO regulation than over-regulation, which is why I rarely join any sort of club or governing body...most have WAAAAAYYYYY too many rules/regs.

There is a certain amount of risk involved in the hobby of rocketry....I'd just as soon accept that (part of the fun....no risk/danger=NO FUN) instead of constantly try to weed it out/reduce it.

[Doug Sams]

Typical over-regulation....GH,

You're free to do this on your own. The restriction is at club launches. Nobody's gonna bust you for doing it at unsanctioned launches. (Although your NAR/TRA insurance will likely not cover this.)

After reading about this the past 2 days, I'm inclined to glue a couple together just for a cheap thrill :) I'm thinking a C5-0S to a C6-5 in a Big Bertha. How's that sound?

Doug

.

[shockwaveriderz]

GH,

You're free to do this on your own. The restriction is at club launches. Nobody's gonna bust you for doing it at unsanctioned launches. (Although your NAR/TRA insurance will likely not cover this.)

After reading about this the past 2 days, I'm inclined to glue a couple together just for a cheap thrill :) I'm thinking a C5-0S to a C6-5 in a Big Bertha. How's that sound?

Doug

.


I've done it with some B6-0/B6-6 and its definately a cheap thrill. with that combination Doug, you would probably get a burnthrough die to the combination of the two engines thrust durations being in excess of 2 seconds.

terry dean

[Shreadvector]

I've done it with some B6-0/B6-6 and its definately a cheap thrill. with that combination Doug, you would probably get a burnthrough die to the combination of the two engines thrust durations being in excess of 2 seconds.

terry dean

The nozzles should be identical. If the lower nozzle is larger it will have losses. if the lower nozzle is smaller it will overpressurize and fail.

And, as stated, if your glue joint and/or sleeve (i.e your homemade casing into which you install 2 normal model rocket motors to create an uncertified device) is bad, it will fail at the joint. And then there is the burn through issue at the bottom....

[Bob Kaplow]

I tandemed a few motors back in the day, and don't remember ever using a sleeve over the joint. Most were just butt joined end to end; an A3-0T and A3-6T for B Payload at NARAM-20 IIRC.

The neat ones were sticking a A3-4T into a C6-0 to get into the D class for D BG and similar events. Or a D12-0 C6-3 for E class events.

Around the same time as tandem motors, we had AVI "Gold" series motors that used delay ejection modules epoxied into the end of their motors. I made a neat F24:D12 tandem probably for a Dual Egglofter that I never fired, and is still in my collection somewhere.

[LeeR]

Hey,

I'm currently designing a model rocket and would like to make it 3 stages and have a few questions and concerns. First is it even possible to do 3 stages and if so is it anything like 2 stages? Second when using this much power should I be considering the weight of the rocket? And lastly do the first 2 stages need to break away or can they just fall out of the tube?

Any help is much appreciated!

Ben

There have been lots of suggestions on getting started in staging with something less ambitious than a 3 stage rocket. Check out this Estes Plan from 1965 (the Augie II). I built this as a kid, and it was a blast to fly. I've toyed with upscaling this to a 24mm 2 stager.

http://www.dars.org/jimz/eirp_28.htm

[Green Dragon]

The neat ones were sticking a A3-4T into a C6-0 to get into the D class for D BG and similar events. Or a D12-0 C6-3 for E class events.


That's the tandem motors I remember.

Like a F100-0 / C6-7 tandem to make a baby F, or D20-0/ A3-6T .

doubt I have any fired examples in the dead engine box, will have to dig and see. lol .

~ AL