Planning 3" Upscale of the Estes Optima

[mcfly1883]

New member here, loved Estes rockets as a child and later building/launching with my nephews (within the past several years). I haven't built a rocket in quite a while and after checking the Estes website specials, it seemed like a good time to jump back in. This is a slow build, still in the planning/material gathering stage. I bought a Scion kit about 4 months ago and I thought it would be cool to build an Optima upscale using the 3" tubes and nose cone. After searching, I realized this is not an original idea, with several examples already built. So, after much research here at rocketryforum (thanks to everyone for all the knowledge available here), I decided to get started. For now, I'm leaning toward single deploy with motor ejection. I can always cut the fwd/mid airframe (in the single deploy configuration, the fwd/mid airframes are actually one piece) in two and convert to dual deploy later.

I am by no means reinventing the wheel here, just using what seems to be tried and true methods/materials on a classic rocket design.

This is essentially 115% scale, give or take a few fractions of an inch here or there. Attached are preliminary Open Rocket designs, both single deploy and dual deploy. These do not include possible fiberglass reinforcements, hardware, etc, so the weights are not final.

Modified nose cone to house an e-bay
Fiberglass sleeved airframes
38mm motor mount
Aero Pack retainer and 29mm adapter
Giant leap hardpoint shock cord mount (maybe?)
Kevlar shock cord
Parachute size/shape TBD
Birch ply rings/bulkheads
Fiberglassed birch ply fins
TTW fin attachment
Removable fwd/mid airframe from booster section (maybe?)





View attachment Optima Dual Deploy.ork

View attachment Optima Single Deploy.ork

 

[r12ski]

Have you seen this thread? https://www.rocketryforum.com/showthread.php?t=131246

 

[K'Tesh]

New member here, loved Estes rockets as a child and later building/launching with my nephews (within the past several years). I haven't built a rocket in quite a while and after checking the Estes website specials, it seemed like a good time to jump back in. This is a slow build, still in the planning/material gathering stage. I bought a Scion kit about 4 months ago and I thought it would be cool to build an Optima upscale using the 3" tubes and nose cone. After searching, I realized this is not an original idea, with several examples already built. So, after much research here at rocketryforum (thanks to everyone for all the knowledge available here), I decided to get started. For now, I'm leaning toward single deploy with motor ejection. I can always cut the fwd/mid airframe (in the single deploy configuration, the fwd/mid airframes are actually one piece) in two and convert to dual deploy later.


I am by no means reinventing the wheel here, just using what seems to be tried and true methods/materials on a classic rocket design.


This is essentially 115% scale, give or take a few fractions of an inch here or there. Attached are preliminary Open Rocket designs, both single deploy and dual deploy. These do not include possible fiberglass reinforcements, hardware, etc, so the weights are not final.


Modified nose cone to house an e-bay
Fiberglass sleeved airframes
38mm motor mount
Aero Pack retainer and 29mm adapter
Giant leap hardpoint shock cord mount (maybe?)
Kevlar shock cord
Parachute size/shape TBD
Birch ply rings/bulkheads
Fiberglassed birch ply fins
TTW fin attachment
Removable fwd/mid airframe from booster section (maybe?)

Welcome to the forums!

Nice job on the sims!

I'd go ahead with the break at the fwd/mid airframe sections. you could install a coupler there (perhaps as a baffle), and fly it as a single deploy so long as your linking screws don't grab the laundry... You could even make the fwd airframe into a zipperless design with the baffle, and not even have to worry about snagging your chute. Then if you want, you could change out the coupler/baffle and put in the DD/AV bay (don't want to use the dirty coupler as it may be bad for the electronics).

Another option would be to build it as a zipperless single deploy (w/baffle in the fwd/mid coupler), then have an AV/DD bay in the nose (DD for redundancy), and use the Jolly Logic Chute Release on the main.

 

[Cabernut]

Wha-hey! Great choice for a rocket! I'm definitely looking forward to your build.

OR tends to underestimate weight, mine was almost HPR by weight alone once finished. Pad weight was 1430g.

The Optima is a good lookin' bird. Going to be a fun one

 

[mcfly1883]

Yep, awesome rocket design. It was one of those I always wanted as a kid and now its awesome that I can attempt to build a larger version. Part of what pushed me to do this build was seeing the builds here.

I figured the initial weight was on the low side. I need to get a scale so I can weigh the components and update the sim as I go along, especially if I do the fiberglass laminates.

I'm not entirely decided on the final configuration (dual, single, zipperless, etc), so I appreciate the ideas.

A note pointed out by K'Tesh: The stiffy coupler tube used in the nose cone modification is originally for 3" ID airframes. The Estes PSII is 3" OD, with an ID of 2.93". I have peeled away a few layers of the stiffy coupler so that it will actually fit in the PSII coupler which has an ID of 2.86. Of course, I'm not sure how all this will work, as this was just an idea of how to extend the nose cone shoulder since the original shock cord mount was cut off. Here is the nose cone by itself.

Edit: The remaining polystyrene shoulder on the nose cone is only 1.1" long, not my original OR sim length of 1.5". I have uploaded the updated nose cone below.

View attachment Optima Nose Cone.ork

 

[K'Tesh]

Here's my idea in a .ork file...

 

[mcfly1883]

I like the baffle system, I may have to try and incorporate that if I go single deploy. It definitely seems like a waste to not do something with all that glorious airframe above the booster, its almost just asking for dual deployment. I was trying to keep the separations at the paint lines, but it seems as though the main bay should be larger than the drogue bay (accommodate larger parachute) but with the way it is, I get 6.75" for the main and 9.25 for the drogue. I guess it really doesn't matter as long as the 'chutes fit.

I'm concerned about the strength of the coupler tube for the av bay (and booster section for that matter) in the dual deployment configuration. This is the "low power" coupler with a wall thickness of .035". Maybe an internal fiberglass lamination would be in order to strengthen it up.

 

[rharshberger]

I like the baffle system, I may have to try and incorporate that if I go single deploy. It definitely seems like a waste to not do something with all that glorious airframe above the booster, its almost just asking for dual deployment. I was trying to keep the separations at the paint lines, but it seems as though the main bay should be larger than the drogue bay (accommodate larger parachute) but with the way it is, I get 6.75" for the main and 9.25 for the drogue. I guess it really doesn't matter as long as the 'chutes fit.

I'm concerned about the strength of the coupler tube for the av bay (and booster section for that matter) in the dual deployment configuration. This is the "low power" coupler with a wall thickness of .035". Maybe an internal fiberglass lamination would be in order to strengthen it up.

You can also go with a zipperless design, by basically making a extension of the mmt, with a coupler, section of mmt tube and 2 centering rings, a kevlar harness could be attached wildman style (epoxied to the mmt section, then the whole unit epoxied into the airframe to create a zipper less fin can section.

 

[K'Tesh]

I like the baffle system, I may have to try and incorporate that if I go single deploy. It definitely seems like a waste to not do something with all that glorious airframe above the booster, its almost just asking for dual deployment. I was trying to keep the separations at the paint lines, but it seems as though the main bay should be larger than the drogue bay (accommodate larger parachute) but with the way it is, I get 6.75" for the main and 9.25 for the drogue. I guess it really doesn't matter as long as the 'chutes fit.

I'm concerned about the strength of the coupler tube for the av bay (and booster section for that matter) in the dual deployment configuration. This is the "low power" coupler with a wall thickness of .035". Maybe an internal fiberglass lamination would be in order to strengthen it up.

I'd recommend shortening the motor tube some, and building this with a baffle there. Sure, it'll limit the length of the motor you can use, but are you really going to send this into orbit?

I'd break it at the color joints just like you planned. I agree that it'll look better that way. I've attached another sim showing this as a true dual deploy capable rocket (but set up the the main and a JLCR) along with the baffle (and shortened motor tube).



(I also restored stiffy coupler to the original config, as well as the black section to it's original length, and extended the white section to make up for the switchband I removed.)

[EDIT] Oh, and the strakes (the forward fins) likely don't need to have full length fin tabs glued to the motor mount (or fin tabs at all), as they won't be nearly as vulnerable to damage as the main fins will be. Personally, I like them being TTW, as that reduces the chance I'll foul up the alignment and end up with them causing drag, or making the rocket to roll in flight.

Like you said, so long as the parachutes can deploy, it doesn't matter if the drogue's in the larger body tube section or the main is.

I'd go ahead and strengthen the couplers, or buy heavier duty couplers if you're worried about it.

 

[mcfly1883]

What's wrong with putting it into orbit? Good point though, 18" of motor mount tube may not be completely necessary and I like TTW as well, but surface mount would be more than adequate for the fwd fins, I'm sure. I gotta reign in my expectations and compromise if I want it to follow the Optima form.

Is there any concern for the distance between the ejection charge blast (dependent on length of motor hardware, of course) and the baffle assembly? Is it possible/feasible to place a baffle in the actual motor mount tube?

 

[Cabernut]

Any baffle is going to increase the pressure behind it. If you were to say, install a half-moon baffle within a 29mm motor mount, that would effectively be forcing the 29mm ejection charge through a BT-20. Like coughing through a straw. Better off using the full width of the airframe to keep flow as free as possible.

Personally I'll be leaving about 6-7" of space between the baffle and end of the motor tube. I'd be interested to know if there's some sort of "sweet spot" with placement of a baffle.

 

[mcfly1883]

I'd be interested to know if there's some sort of "sweet spot" with placement of a baffle.

Yep, I was wondering the same thing.

Here is an Estes The Shadow, single deploy, baffle, nose cone e-bay, and more room in the booster for longer motors. This could be used with a 'chute release. I'm leaning toward simplicity and I think single deploy/motor ejection fits the bill. I do like the paint scheme on the Optima better, but The Shadow is cool too. Plus, I can keep the airframe break at the paint line (I know, not super important, and I could modify the Optima so that the breaks are not necessarily at the paint line). Speaking of, since The Shadow's instructions do not specify a paint line location, I estimated based off catalog pictures.

 

[K'Tesh]

I thought it was fairly clear that the paint breaks are at the body tube joints.



One thing you could do is put a bulkhead on the backside of a tube coupler at the fwd/mid airframe joint and make your recovery bay the mid airframe section. That would leave the fwd airframe open for a payload if you wanted. This would also reduce the volume of the area that the ejection charge needs to pressurize, and reduce the chance that a weak ejection charge would prevent your parachute from deploying. Last night, I saw on facebook where someone's MDRM based upscale of the Der Big Red Max had that problem (nose didn't eject forcefully enough) and it ended up taking a 5" deep core sample.

Another thing... In your ork, you've got the baffle as part of the mid airframe part. I'm sure you know in reality you'd want it as part of the booster, unless you're intending to glue the mid airframe to the booster too.

If you use screws to attach the F/M airframes together, you could then change the coupler out and replace it with a proper AV bay with DD.

BTW, I'm glad you've modified the nosecone (should you decide to go with popping the nose). The Big Daddy (which uses the same nosecone) has a record of lawndarts, and anything that reduces the pressure behind blowing it is IMHO a very bad idea. Problem seems to stem from that long sloping area that the shock cord is supposed to mount to.

BTW... Are you going to use rail buttons or LLs?

 

[mcfly1883]

I thought it was fairly clear that the paint breaks are at the body tube joints.

Oh, yes, of course, I agree 100%, that was my plan from the beginning. I guess I should have been more clear in my last post. I was merely commenting on a way to increase the available room for longer motors and increase distance from ejection charge to baffle; namely to increase the length of the booster section. If the booster section was increased, then the white/yellow paint line would not correspond to the body tube joint, which is absolutely not a problem. The Shadow has a longer booster section, which would hold longer motors and have more distance between ejection charge and baffle, and could, in theory, be painted like an Optima, which is an option.

But, after some calculations (and careful building), it appears that even in the Optima configuration with a booster length of 16.25", both a 29/360 and a 38/720 would fit--just barely. It would have to be plugged, since the fwd closure would be within fractions of an inch from the baffle bulk head. In this configuration, I could fly dual deploy, assuming I have the AV bay setup between the fwd/mid airframes, as you suggested in post number 9.

I guess this is too much thinking when it comes to simple painting schemes...but its fun to plan. And, I have to remember, I can always build another one in a different configuration!

And yes, the baffle would be mounted in the booster. Rail buttons, for sure.

 

[Cabernut]

For my "post-prang rebuild", I'm placing the baffle 4" above where a 6XL casing would extend to. Do I think I'll ever launch it on an I motor? No. But it's good to plan ahead and leave room for future possibilities.

So I guess the other thing to consider is what size motor mount? 29 or 38? Building for 38mm with 29mm adapter is a good plan. More options. For my build I stuck with 29mm for simplicity and to save build cost. My goal was to stay in the G&H motor range so 29mm is all I would ever need. However if I were to start over from scratch with the goal of building for say, up to 500N motor range, then 38mm capability would be mandatory as the highest 29mm is a 384N baby-I. If you can afford the extra cost, stick with 38mm. You can always adapt smaller.

I think you have a good plan. When you start building, feel free to post in detail along the way so hopefully the gurus here can advise.

 

[DavidMcCann]

You guys are killing me with these 3 inchers..... must not upscale.....

 

[Cabernut]

You guys are killing me with these 3 inchers..... must not upscale.....

C'mon you know you want to... Just one.

 

[rharshberger]

C'mon you know you want to... Just one.

There can be only one......well maybe a few......

 

[mcfly1883]

Everybody's doing it, might as well join in the upscale fun!

No real progress on the Optima plan, but I am heavily leaning towards a setup similar to K'Tesh suggestion in post #9. I did get some materials in recently; tubes, couplers, retainers, and hardware. Not shown is my stash from McMasterCarr and some supplies from FibreGlast. I even dug my D-Region Tomahawk and Maxi-Brute Honest John out of storage so I can continue to plan their builds. Those have been in the idea bank for quite a while--I saved the "classroom series" instructional builds from the old RocketryOnline (circa 2010ish) website and I plan on building them similar.