3/4 Scale Nike Smoke -- Input / Opinions Thread

My goal is to get this built for flight at LDRS33 this coming July. This will not be a build thread, per se, but instead a place to solicit input during the build process in areas that aren't black/white in my mind, but instead a dingy gray.

I would share a Rocksim file, but during an upgrade/computer switchout a few weeks back, I inadvertently overwrote all my design files :y:. I have them partially recovered back to about the Spring of '13, but the current set does not include this rocket which was lost. I will re-enter it in the next month or so, but probably needless to say, it is a big rocket. Approximately 12 feet tall and 11.5" in diameter. All thick-walled fiberglass so heavy too. Given the weight, even with the 98mm core & 4-54mm setup, top velocity is no more than 1.2 mach.



Given the above, and thinking about getting up to LDRS in Wisconsin, over the last month the transportability of the rocket has become a concern, and, in fact, has moved up the goal chart to nearly #1 for this project. To that end, I would like the finished rocket to be able to be broken down essentially to the pieces you see in the picture above, thus biggest factor becomes doing the design/build with removable fins.

A few comments on the fins (see pic below)... Span is 15.5", root is 16". Familiar Nike Smoke beveled trapezoid with max base of width of 1.5" and max tip width of 5/8". Given the weight, even with the 98mm core & 4-54mm setup, top velocity is no more than 1.2 mach. All this has been run through FinSim and my flutter & divergence velocities are way up there at 2500+ fps so I'm good there. If not, I probably wouldn't even consider making these removable. The second, related point to consider is the build quality. I'm sure most have experienced the early "flaky" fin cans put out by Performance Rocketry that cracked when you blew on them--these guys are no where close to that. The overall shell of fabric seems rock solid and the polyester gel coat seems thick and substantial. Fill on the fins is with a dense foam and the overall weight of each fin is bit over 3.5lbs--I can't yet give an exact weight because the TTW length is actually 1.5" less than the tab shown in the picture (only extends down to the pink mark). Tab depth then is a little less than 4" and tab width is 7" centered.



Last picture for reference-sake is of a centering ring. As expected, two of these will be "sandwiching" the fin tabs. Probably obvious, but in the picture the fins are at the noon, 3 o'clock, 6 o'clock and 9 o'clock positions.



OK, that is probably enough... I intended to go on and provide my current solution/direction, but on second thought maybe instead of biasing people, I will stop here and then TRF'rs can give their ideas / directions which may be far better than the path I'm going down now. If not, I do have big question about piece part fabrication that will be part of this thread, that is if my current direction holds.

Oh, one other point I should say regarding the fins... Talking to Mr. Cayemberg (ECayemberg) who has some experience with projects this size, I will be adding substantial reinforcement to the tab area and the bottom 1.5" of each of the fins which will be laminated with 12 oz. Kevlar cloth at those points (tab area completely wrapped--not just sides). This I would have likely been done whether the fins were removable or not.

So with all the above as input, anyone have suggestions on the removable design for the fins?

Best example I have with considerable flight experience is Jerry O'Sullivan's 7.5" Iris. He has flown this rocket on more power than it seems you can work into your Smoke.

https://www.vahpr.com/VAHPR/Iris_Build_Photos/Iris_Build_Photos.html

I'd suggest a "backwards ejection" design to keep the aft section short (as well as the normal reason of reducing zippering). That way, the widest and heaviest section is not also the longest. See a comparison of the two styles on my ARLISS 2004 page. With this design, your aft section is barely longer than the largest motor you want to fly.

patelldp said:

Best example I have with considerable flight experience is Jerry O'Sullivan's 7.5" Iris. He has flown this rocket on more power than it seems you can work into your Smoke.

https://www.vahpr.com/VAHPR/Iris_Build_Photos/Iris_Build_Photos.html

Click to expand...

Thanks for the link. I have seen posts on this project, but there is much more detail on these pages. Full removable MMT might be an issue though for this design given were the TTW points meet (so far forward of the aft of the booster airframe).

One thing I'd caution is that with the fins higher up from the bottom than usual and a 100lb fincan, your biggest stress may actually be when the rocket "falls over" on landing. On my 11.5" Little John, I've damaged the top of the tube when the rocket falls over after hitting bottom first very slowly. This contact also stresses the fins.

The other thing to consider is that your giant chute may stay inflated after landing and drag your rocket through the field with the fins banging into every cornstalk and boulder. The gelcoat may feel strong, but after banging over a bunch of rocks it's going to take a beating. For these reasons, I'd be glassing the hell out of the fins and permanently attaching them. I've seen my 250lb rocket fly across the field at an alarming speed due to an inflated C9.

You'd be surprised how much you can fit in an SUV. I can pack my 11.5" Little John, a 7.5" rocket and a hell of a lot of rocket gear. If you need more than the one seat up front for a wife or child I would suggest a divorce over removable fins. :lol:

If you are committed to the removable fins, I agree that Jerry's design is a very good proven starting point.

Todd

THarrison said:

One thing I'd caution is that with the fins higher up from the bottom than usual and a 100lb fincan, your biggest stress may actually be when the rocket "falls over" on landing. On my 11.5" Little John, I've damaged the top of the tube when the rocket falls over after hitting bottom first very slowly. This contact also stresses the fins.

The other thing to consider is that your giant chute may stay inflated after landing and drag your rocket through the field with the fins banging into every cornstalk and boulder. The gelcoat may feel strong, but after banging over a bunch of rocks it's going to take a beating. For these reasons, I'd be glassing the hell out of the fins and permanently attaching them. I've seen my 250lb rocket fly across the field at an alarming speed due to an inflated C9.

You'd be surprised how much you can fit in an SUV. I can pack my 11.5" Little John, a 7.5" rocket and a hell of a lot of rocket gear. If you need more than the one seat up front for a wife or child I would suggest a divorce over removable fins. :lol:

If you are committed to the removable fins, I agree that Jerry's design is a very good proven starting point.

Todd

Click to expand...

Actually, all good points. On my L3 I have had flipping damage (long booster, fin forward).

SUV, yes, but I am for the most part using Avis to drive to Airfest and such. With the rental route you have much more of a "wild card" on exact size/spacing that gives you a surprise at the last minute. My comfort level goes way up if I start renting mini-vans, albeit at a higher cost.

Divorce... probably not.

JohnCoker said:

I'd suggest a "backwards ejection" design to keep the aft section short (as well as the normal reason of reducing zippering). That way, the widest and heaviest section is not also the longest. See a comparison of the two styles on my ARLISS 2004 page. With this design, your aft section is barely longer than the largest motor you want to fly.

Click to expand...

John, I get the advantages of the backwards ejection design (actually now doing that on my 5.5" Honest John build), but to do so I'd have to go slicing into 1/8"+ FG airframe wall which scares me a bit given my lack of sophistication in the workshop, i.e., ranging from I may never achieve a tight, square seam all the way to completely screwing up the parts.

So the picture below represents where I am now... Main components for each fin are: 1) two ply U-shapes attached by appropriate wood glue and fasteners, one on each side of the TTW fin and spanning both aft and fore CRs to provide a stable socket, 2) two 5/32" brass sleeves inserted laterally through the length of the fin tab; terminating on both ends inside shoulder bushings epoxied into the Kevlar laminate and internally held in place with Gorilla glue within the dense foam section through which 1/4-20 lag bolts are inserted and, 3) some type of bracketing at base of fin on outside of the airframe.

Clearly the ply socket is meant to keep the fin from rotating/angling side-to-side. The brass sleeve/bushing/lag bolts are meant to keep the fin from moving up and down and from any potential tipping corner to corner inside the socket. This second attachment mechanism is also oriented laterally so assembly can be done without ever removing the motor mount. The outside brackets provide support at the airframe base with minor aid to fin flutter performance similar to external fillets. Given the complex face angles on the Nike Smoke fins outside brackets are the biggest headache in implementation. Right now, I have three options for these:

1. Standard L-brackets. These would need to have custom shaped stand off platforms similar to the Jerry O'Sullivan's Iris rocket referenced above. The need to add these custom wood standoff "warts" to the outside of the airframe make this option the least desirable at this time.
2. Use heavy duty piano hinges to accommodate the varying face angles on fins. Clearly the piano hinges don't provide a fixed base in one direction and have seemed to been less than reliable in some other large designs (e.g., Talon on a P). But in the case of the Nike Smoke, there are actually six opposing angles at the base of the fin, so the potential movement is likely reduced. One of the big problems with both #1 and #2 is the cross fin attachment of the fore and aft fin sections. Because of the opposing angles of ~10 degrees flaring back you don't have a flat cross section to bolt into. At a minimum you would have to use floating Pem nuts, and it could be that you would have to do some special bending/machining of the brackets for them attach securely. These need migrated me to one last option...
3. Last option really gets to my biggest worry, namely that the fore and aft sections of the fin are the most problematic as they don't have attach points like the center tab area. It is not clear that there is even a need for a bracket at the center of the fin given the attachment in the TTW area, and fore and aft fins might only be needed. If so, I would prefer to have a socket/sleeve/cap that fits over each end of each fin that completely enclose front/back root fin points. This would likely have to be a custom designed piece with five or so attach points each.

as a 3/4" nike smoke owner myself (thanks eric c!)- i'd recommend changing the motor mount system to 6" central and then some outboards if you want/if they fit. i wish i had the 6" setup but do not- 4" is ok but in my opinion not optimal. if you dont want do do the big boy motors (like for balls) then stick with the 4" with outboards. jack g. and james d. in ca also have 3/4 scale nike smokes with 6" motor mounts. mark l. in co has a 3/4 scale nike smoke with 6" mount. sometime down the road i will try and coordinate a battle of the 3/4 scale nike smoke drag race or something.. lol - i look forward to see what you with the fins. good luck on the build - i look forward to seeing it fly at ldrs, i will be there.

I've got a Polecat Smoke that I bought partially built, so I'll be watching your thread with great interest.

I've decided to modify it to go with a zipper-less design as well, principally due to the lack of length in the drogue area if I use a full length coupler. The original builder decided to modify it for (4) 75mm motors, which is kind of economically unfeasible for me. I'm going to build 2 fin cans, one with the 4 motors, and another with a single 98mm. I would love to go to a 152mm motor mount, but just the retainer is major expensive.

Best of luck with your build!

SSenesy said:

I've got a Polecat Smoke that I bought partially built, so I'll be watching your thread with great interest.

I've decided to modify it to go with a zipper-less design as well, principally due to the lack of length in the drogue area if I use a full length coupler. The original builder decided to modify it for (4) 75mm motors, which is kind of economically unfeasible for me. I'm going to build 2 fin cans, one with the 4 motors, and another with a single 98mm. I would love to go to a 152mm motor mount, but just the retainer is major expensive.

Best of luck with your build!

Click to expand...

Curious, what is the yellow airframe material? Is it wrapped with Kevlar?

dixontj93060 said:

Curious, what is the yellow airframe material? Is it wrapped with Kevlar?

Click to expand...

That's it exactly. The previous owner used a Giant Leap kevlar sock over the top of the Polecat tubes. No peel ply, so smoothing the finish is going to be tough.

SSenesy said:

That's it exactly. The previous owner used a Giant Leap kevlar sock over the top of the Polecat tubes. No peel ply, so smoothing the finish is going to be tough.

Click to expand...

Yeah, I might be inclined to just put another layer of 3oz cloth and call it a day--easier than trying to finish out Kevlar.

As I am working through the detailed fin attachment, let's move onto another area where some input would be much appreciated. I have looked through dozens of scale drawings and write-ups of Nike Smoke's and very few have the detail included on the smoke ejection system, actually, not the system itself, but the port location / configuration in the nosecone area. The best drawing I do have (from Stine) shows one right-angle pipe and if you cross-reference that to the second picture I have attached, it looks like you can see the orifice located on top halfway between a red fin and to the right (in picture angle from fore) of the single yellow fin. Can anyone confirm or deny if what I am summarizing (single port and its location) is true? BTW, if you haven't already deduced, the idea is to incorporate a simulated working smoke trail port into this design and flight. Current thought is to utilize a Smokey cartridge in a nosecone sub-compartment that is lit after first engine burnout.

View attachment 164144

dixontj93060 said:

BTW, if you haven't already deduced, the idea is to incorporate a simulated working smoke trail port into this design and flight. Current thought is to utilize a Smokey cartridge in a nosecone sub-compartment that is lit after first engine burnout.

Click to expand...

No TiCl4?

daveyfire said:

No TiCl4?

Click to expand...

Hmmm, yeah, sure, I have a vat of it stored on the "Back 40."

Keep it up Tim, really looking forward too seeing this build and, maybe the flight!

I wanted to follow up on the placeholder in the first post to reenter the Rocksim file (turns out to be a little over 13' and close to 100lbs dry weight). After doing all the weights and measures again and building the file, I began to simulate and survey available motors/motor hardware. After consultation with David Reese and others, I have pretty much decided on a first flight configuration, namely, a Loki N3800LW and four Kosdon (not KBA) K700F airstarted to give an equivalent N-M flight profile. BTW, I have posted just one of two different Rocksim files. The two differ in recovery approach. As is always the case for large projects (maybe any project), recovery is the most important design consideration. The Rocksim posted is a version with a nosecone chute cannon. The second version I am working on uses redundant, bulkhead mounted Defy Gravity releases to hold the main. I am working on the details of both, looking at highest success probability and also considering available parachutes and weight of various recovery break point sections.

View attachment Nike_Smoke_3-4scale.rkt

dixontj93060 said:

I wanted to follow up on the placeholder in the first post to reenter the Rocksim file (turns out to be a little over 13' and close to 100lbs dry weight). After doing all the weights and measures again and building the file, I began to simulate and survey available motors/motor hardware. After consultation with David Reese and others, I have pretty much decided on a first flight configuration, namely, a Loki N3800LW and four Kosdon (not KBA) K700F airstarted to give an equivalent N-M flight profile. BTW, I have posted just one of two different Rocksim files. The two differ in recovery approach. As is always the case for large projects (maybe any project), recovery is the most important design consideration. The Rocksim posted is a version with a nosecone chute cannon. The second version I am working on uses redundant, bulkhead mounted Defy Gravity releases to hold the main. I am working on the details of both, looking at highest success probability and also considering available parachutes and weight of various recovery break point sections.

Click to expand...

Really like that flight profile; warms my heart just thinking about a recent flight! Cool!

Just my $0.02...your setup is almost exactly as Gerald's is. The first flight....er flop (launch system malfunction) I had set up the recovery system with twin Defy Gravity Tethers. It was a huge pain in the rear to prep and I'm not certain how well it would've worked anyway. Recognizing the limited space for recovery in the airframe (it's amazing how 4' motors, long coupler and cone shoulders eat up a booster) and not wanting to fill the entire cone cavity with foam, I installed a full length 6" phenolic airframe in the nose. Though we flew the most recent flights single deploy, I suspect Gerald will use the 6" tube for housing the main. I know if I were to fly the beast another time and wanted dual deploy: I'd put a pair of electronics in the nose and put the main up there.

Good luck whichever direction you choose. Looking forward to watching this one develop!

-Eric-

ECayemberg said:

Really like that flight profile; warms my heart just thinking about a recent flight! Cool!

Just my $0.02...your setup is almost exactly as Gerald's is. The first flight....er flop (launch system malfunction) I had set up the recovery system with twin Defy Gravity Tethers. It was a huge pain in the rear to prep and I'm not certain how well it would've worked anyway. Recognizing the limited space for recovery in the airframe (it's amazing how 4' motors, long coupler and cone shoulders eat up a booster) and not wanting to fill the entire cone cavity with foam, I installed a full length 6" phenolic airframe in the nose. Though we flew the most recent flights single deploy, I suspect Gerald will use the 6" tube for housing the main. I know if I were to fly the beast another time and wanted dual deploy: I'd put a pair of electronics in the nose and put the main up there.

Good luck whichever direction you choose. Looking forward to watching this one develop!

-Eric-

Click to expand...

Eric, thanks for the input--one vote for chute cannon.

No problem, Tim. I forgot to mention; I actually really like using the Defy Gravity Tethers...in smaller airframes. I have an EZI, VB Extreme 54, and 3" min dia that use the tethers exclusively. It just proved to be very difficult when trying to work with big chutes, cords, etc. (ie: what worked on a smaller scale did not scale up well for me anyway).

First flight still planned for LDRS 33?

-Eric-

Oh, and did get some smoke trail system components in today...

Thunderstruck 5 is history and now attention moves to this build. As discussed, the fins need reinforcement and protection, not to guard against flutter, but to primarily strengthen the attachment area and, secondarily guard against dings and non-optimum landings. First step is to develop templates as needed. Top one is for of the two pieces of fiberglass (6 oz., two layers of each of those, 8 total pieces). Bottom two are for the 10 oz. Kevlar. Left is the wrap for the fin tab and up 2-1/4" up the root (4 of these pieces) and right is for the fin leading/trailing edges (8 of these).



And all cut for laminating tonight...

Sequencing through the laminating of the fins, two steps on each will take a few days. I suppose I could make it go faster by doing two fins in parallel, but I don't want to stress my vacuum. In the mean time, I sketched up the control electronics. The goal here is to make this as blatantly simple as possible, and given that this is such a large rocket, I want to be as safe as possible. I am looking for a measure of time/altitude to make sure I am on the flight profile along with the extra verification of fairly vertical flight, this is done through the Missleworks RRC3 and Tiltometer, respectively. The second altimeter may be another RRC3 or a MARSA54. I don't need to make that determination yet as both have programmable auxiliary ports that can drive a piezo siren triggered sometime after apogee. Other than that, I have a timer in the nosecone to run the simulated smoke trail upon ascent.

If you recall there was some discussion of using a chute cannon and putting all recovery and most electronics in the nosecone. But as I thought of it further, setup could prove tight given the size of the parachute and putting the tilt/staging electronics (potentially) up there also. Also factoring in this decision was a calculation of forces and shear pin needs. I believe the lowest risk, highest success, recovery method is to drop back to a standard dual deploy setup with a drogue aft and main forward. The difference will be using a second/separate recovery for the nosecone. Finally, keeping with reducing risk, I will utilize my standard deployment bag setup for both main parachutes.

If you don't have already the Tiltometer, you can use a TeleMega of Altus Metrum , so you will have the altimeter and tiltometer combine in a single unit

Area66 said:

If you don't have already the Tiltometer, you can use a TeleMega of Altus Metrum , so you will have the altimeter and tiltometer combine in a single unit

Click to expand...

Already have the Tiltometer and even two of my own design using uMAD and a latching relay circuit. But I'm using the former "professional" solution for this flight.

What did you use to cut the kevlar? Regular scissors just don't cut it...

blackbrandt said:

What did you use to cut the kevlar? Regular scissors just don't cut it...

Click to expand...

Kevlar scissors. I posted a couple months back when I bought them along with the Amazon link. Can't look for the post right now on my iPhone but it should be easy to find with a search.

dixontj93060 said:

Kevlar scissors. I posted a couple months back when I bought them along with the Amazon link. Can't look for the post right now on my iPhone but it should be easy to find with a search.

Click to expand...

I have used a regular pair of scissors from walmart to cut kevlar fabric without any issue. Cost was $3.00.

isobig said:

I have used a regular pair of scissors from walmart to cut kevlar fabric without any issue. Cost was $3.00.

Click to expand...

I have been cutting Kevlar over a decade and never got a regular pair of scissors to work especially on this 10oz stuff.