Senza Confini - Max performance 54

Senza Confini, is a "max performance" 54mm Carbon fiber minimum diameter rocket.

Optimized for the Aerotech 54/2800 hardware or CTI Pro54-6Gxl hardware.
It is only 38 inches in length, and weighs about 1.8lbs empty.

We are expecting upwards of 27,000 AGL out of it on any motor fit for these hardwares (excluding Skidmarks).

This rocket is reserved for AeroPac's Black Rock Desert launch site only.

The pictures attached to this first post are the ORIGINAL designs. Along the build process, a few minor modifications were made.

The first steps to creating this beast were to obtain all neccisary parts to build her.

This included various custom parts such as the custom milled 6061 tailcone, the Dragonplate Quasi-Isotropic Carbon Fiber fins, etc. as well as your "standard" rocket parts.

This also included a 6061 Jig that I had to cut using a plasma cutter, to match the other fiberglass one that I had ordered. This took some careful AutoCAD work and a few tries, but eventually I got it perfect.

Lots of fliers choose kits or scratch builds without part modifications because they either do not have access to the proper tools to make those modifications, or because its easier to not have to deal with the hassle, which is understandable.

However, we happen to have access to some nice power tools in a shop that make modifications a simple task. Who needs a dremel and a paper wrapped as a cutting guide when you have a table saw with a fence connected to a measuring track? We used it to cut the Fillament wound T1000G Carbon fiber airframe with a Diamond Cut off wheel that we bought from OSH for about $50. As long as you go slow, it makes a nice clean cut. And it is remarkably loud, too, haha.

Also during this phase, we took advantage of the CNC mill in the shop, and my knowledge of AutoCAD. We examined a variety of different geometry to apply to the fin to give it the best aerodynamic effect within reason of creating. We found that creating a 5 degree tapper angle, at 1/2 inch offset, created a nice leading, trailing, and top edge while still leaving plenty of flat surface area to build the tip-tip onto. This left the edge of the fins at .03125 inches - sharp enough, but without flaking away the edge of the fin. We had to create a jig in order to facilitate the angle without factoring in a Z coordinate travel path into the mill's task, which would take alot longer to cut.

After the fins were finished milling, and the airframe was successfully seperated into its designed lengths, it was time to begin assembling the vehicle.

Each fin had a bit of "flaking" leftover from the mill. -- I used a 1/4 inch dia. endmill with 2 teeth running at a very high RPM, and traveling at 1/10 inch per second. This still left a little bit of stringy carbon fiber attached to the edge. I would call it Flaking, though im sure others have different names for it.

This was removed easily with a few light passes of sandpaper. Any excess leftover wouldnt be an issue anyways.

Fin assembly begins first by roughing the hell out of the airframe with a razor blade (reccomended tool of choice) . This is an essential step in order to make sure that the adhesives have alot of random geometry to grab ahold of. Laminating epoxy in my case is not penetrating, and so therefore will rip right off under high mach stress.

Once the airframe was sufficiently roughed up, the first fin was tacked on with Superglue. We use superglue for our initial positioning because it is strong enough, that when cured, can take moderate handling. Yet, it is weak enough that if a flaw is spotted and the fin needs to be repositioned, it can easily be snapped off and reglued without fear of damaging your rocket.

Using the Jig will help you get your fins at that perfect 120 degree angle and usually more or less perfectly straight as well, but I always like to check them with a lazer if possible.

Once all three fins were in the perfect positions, It was time to apply fillets. I was reccomended Cotronics Durlaco 4525 epoxy because it had an incredible temp rating as well as an amazing 10,000 PSI + tensile strength rating.

Unfortunately, I made the mistake of ordering it in a package of 1qt rather than individual mix packs. The problem with that is that it leaves the rationing and mixing up to the user. This stuff is made to order and quite expensive ($100 I paid for a quart and hardner) so its not like you can just send it back.

This meant that I had to obtain a gram scale. In the end, it wasnt such a bad thing, because I could regulate my fillet weight precisely, and enter better numbers yet into rocksim.

For those who are wondering - "how hard can rationing of epoxy:hardner really be?" .... Well.... its 100:8 mix ratio BY WEIGHT and youre only using a few grams... yeah

But anyways... Once you get the 4525 mixed, it has a great consistancy to work with. Not as thick as JB weld, yet not as thin as epoxy. It made it quite easy to do some nice fillets.

The process is simple - Mask off your area around the fins and airframe and isolate the area where the fillet will be. Then, carefully apply your fillet material to the target area, being sure not to pour in too much. Once it has settled for a good bit, you can use the end of a PVC pipe to create a nice curved shape.

Here you can see my Dad assisting me with this potentially messy process. In retrospect, there are a few things that we shouldve done differently.
1- We shouldve added some angled masking in there to create an angled fillet to the leading edge and trailing edge.
2- We shouldve chipped up any material that didnt belong before it hard cured.

Perhaps the area of the most modifications from the original design is the top of the rocket.

In the original design, we were going to use a PerformanceRocketry Proline 54 nosecone. We ended up trading out for a PerformanceRocketry Fillament Wound G12 nose. This gave us a little more cramming room, and no pesky seam to sand down. Plus, its stronger.

Also, in the orignial design, we were going to be using a Shadow Aero FLASH High visibility streamer... Now we are using a TopFlite 24" thin mil RSN X-Form Drouge. This will bring her down a little lighter, but not too slow.

The original Avbay design fit a Gwiz LCX and backup Perfectflite HiAlts45k. The tracking system was to be secured to the shock cord. After a while of examination, modifications were made so that the new avbay houses a Featherweight Raven2 / Perfectflite Stratologger and has the RF tracking system in a seperate compartment above it, but within the same tower. All of this is protected by a 38mm Bluetube2.0 coupler, which also plays various other roles in shock cord dampening and packing, which I will explain in a later post.

The entire avbay tower is secured to a Fiberglass and baltic sheeting plate (stronger than carbon fiber) , which is secured to the motor. This plate also serves as a shock cord anchor. Baltic sheeting is not the same as "baltic birch" .... it is a paper towel like material that when sandwiched between fiberglass, and cured under lots of weight, produces a plate that is stronger than carbon fiber, not conductive, leighter, and a hell of alot cheaper. I used this as fin material to make fins for another one of my 54mm min dia rockets. It is good stuff. Find it at TAP Plastics.

Doing a Tip to Tip Layup on a rocket is truly a changing moment in the rockets life. Depending on the rocket, this is usually the most complex and time consuming step in the entire build process. Many Rocketeers have different styles of performing this process, and I will guide you through mine.

I learned from a variety of Rocketeers that in order to get the best strength out of your layup, you have to orient the weaves in the right direction, and then treat it the right way for curing. It also helps to have good epoxy.

For this tip-tip I am using West Systems 105 Resin with 206 Slow Hardener, 5.7oz Twill Weave Carbon fiber, and Nylon Peel ply. I use a chip brush to apply the epoxy.

The first step is to create a prototype of what you want your fabric to resemble, but with paper. You then lay this paper on top of your Carbon fiber fabric, and use masking tape to outline it. Then you can go and cut out that shape, leaving about 1/32 inch of tape to keep the fabric from fraying.

I did my tip-tip in 2 layers. The first layer is a bit smaller than the second layer. This creates an A-Symmetrical flutter resistant shape to the fin. I also made sure to cut and orient the first and second layers 90 degrees apart from one-another. This gives me the maxiumum possible layup strength.

Once the fabrics are in the right shape, it was time to mix epoxy, apply them and apply the peel ply on top.

After that, you just let 'er cure and repeat the steps.

Once all three tip-tips are cured, and the flashing trimmed, it becomes time for the most tedius process of Senza's build - finishing the fincan.

The peel ply leaves behind a texture similar to a fine mesh. This is first hit with several light coats of epoxy, with 160grit wet sanding in between coats. What we are doing is leveling out the surface and eliminating imperfections.

Eventually, the surface will get to a point that we can bump up the grit and begin wipe on coats. This will blend the transition between airframe and Tip-Tip reinforcement. It will also give us a fairly glass smooth surface ready for automotive clear coat.

Early into this process we noted two "hitchikers" if you will... A peice of stray masking tape and a brush strand that are now permanently imbedded into my fin can. They mustve fallen off of my jacket during the laminating process or something. Who knows, maybe they will be the very things that provide me with the last few iotas of anti shred strength that I need one day...

Alot of rocketeers that like to push the envelope tend to forget something quite important when they build their rockets- and that is Sealing the leading and trailing edges of your fins.
The idea is simple - apply a high temperture epoxy just to the leading and trailing edges of the fins, that prevents them from delaminating at high mach speeds.

I chose not to seal the leading edges of one of my other 54mm min dia rockets and it had a near delam. Since then, I will always seal anything that will go over mach 2.

To seal Senza's fins, I mask off the area around the leading edge, and using a sponge brush, wipe on a thin coat of Cotronics 4525. After that coat has dried, I sand it down and then re apply, moving the masking tape back about 1/4 inch. This gives us a nice smooth edge and transition.

After many weeks of work, Senza finally made the cut. She was ready to be taken to Shannahan's Auto Body and paint, where she was fitted with an automotive clear coat all around and a Verde Ithica (Lamborghini, Green) nose paint job. Next time, I plan on using Aircraft paint, as it would hold up better under mach.


Now, she sits proud waiting for her first flight, which is planned for AeroNaut 2012.

Frozenferrari, nice work. But did I miss it... Where is your tracker? (you're gonna need it).

It's in with the altimeters. See post #6.

Rocketman248 said:

It's in with the altimeters. See post #6.

Click to expand...

DUH! (Forget I mentioned it--that's what I get for reading posts when I just get out of bed)

How does drilling holes in the knurling affect the motor in the legal sense? It obviously shouldn't actually affect anything, but it could be construed as modifying commercial hardware and limit you to flying research. Maybe.

CarVac said:

How does drilling holes in the knurling affect the motor in the legal sense? It obviously shouldn't actually affect anything, but it could be construed as modifying commercial hardware and limit you to flying research. Maybe.

Click to expand...

I was going to recommend that he just machine the knurling off to prevent any base drag that it may cause. Modifying the external motor case shouldn't be an issue, IMHO, as it doesn't affect the performance of the motor.

The bulb just went on, and I caught how the tailcone is working -- pretty slick.

Are you using the CTI tapered closure for CTI hardware?

-Kevin

FrozenFerrari, Looks really awesome. Where did you get the NC? [Edit]: Never mind, I read the post.

Hmmm... I'll be in Elk Grove this whole next week.


Alex

Aksrockets said:

FrozenFerrari, Looks really awesome. Where did you get the NC? [Edit]: Never mind, I read the post.

Hmmm... I'll be in Elk Grove this whole next week.

Alex

Click to expand...

If you'll be in town Saturday, you should come out to the Snow Ranch launch.

Un nome strafico!!

qquake2k said:

If you'll be in town Saturday, you should come out to the Snow Ranch launch.

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I will try to be at Snow Ranch. It sounds like fun and Its been a while since ive seen good ol' James Marino or alot of the other rocketeers out there. I will try to be out there to catch up and show off this baby.

patelldp said:

I was going to recommend that he just machine the knurling off to prevent any base drag that it may cause. Modifying the external motor case shouldn't be an issue, IMHO, as it doesn't affect the performance of the motor.

Click to expand...

Thats what my original instinct was to do, however consulting with an aeronautical engineer from Lockheed Martin and my father who is a 767 captain, it may not be the best of ideas to smooth out that surface.
From what I was told, the knurled surface will induce laminar flow, thus making the tailcone more effective at M1.75+ , which to me makes sense as well.
I am debating making another one with a smooth surface and running a few more K250 flights just to test that out

As for legal issues, I totally agree that it should be legal for regular flying day flight because it does not affect motor performance, however they will probably tell me to fly it on an EX day. I dunno. I will have to talk to someone like Ken Biba or Tony. Otherwise, I wont be too upset anyway. The K250W is the only motor I have that uses that tailcone. The others (CTI K300CL, L640DT, L935IM) use the CTI certified tailcone for the pro54 hardware.

My understanding is this:

The knurling won't reduce turbulence, it'll increase it. (Just think about it!) It can have a beneficial effect, but probably only at speeds where the flow separation would have been delayed all the way to the tailcone. That is why you see turbulators on the front portion of a wing: to induce turbulence before the aft of the wing where flow separation would increase drag. The Reynolds number of a small supersonic rocket is much, MUCH higher than necessary to get turbulence instantly upon the nose striking the air, so the knurling would only cause shockwaves to form while flying supersonic, inducing additional drag.

https://en.wikipedia.org/wiki/Turbulator

If anything I said is wrong, please correct me with a satisfying explanation, but I can't find it in me to believe that the knurling could possibly reduce turbulence.

Frozenferrari said:

The original Avbay design fit a Gwiz LCX and backup Perfectflite HiAlts45k. The tracking system was to be secured to the shock cord. After a while of examination, modifications were made so that the new avbay houses a Featherweight Raven2 / Perfectflite Stratologger and has the RF tracking system in a seperate compartment above it, but within the same tower. All of this is protected by a 38mm Bluetube2.0 coupler, which also plays various other roles in shock cord dampening and packing, which I will explain in a later post.

The entire avbay tower is secured to a Fiberglass and baltic sheeting plate (stronger than carbon fiber) , which is secured to the motor. This plate also serves as a shock cord anchor. Baltic sheeting is not the same as "baltic birch" .... it is a paper towel like material that when sandwiched between fiberglass, and cured under lots of weight, produces a plate that is stronger than carbon fiber, not conductive, leighter, and a hell of alot cheaper. I used this as fin material to make fins for another one of my 54mm min dia rockets. It is good stuff. Find it at TAP Plastics.

Click to expand...

Cool. Are you going to put a 38mm airframe tube over the whole thing to make a main chute holder/cannon? If you do, and it extends down to the top of the motor, it could provide support to prevent the av-bay from snapping off of the top of the motor after touchdown.

CarVac said:

My understanding is this:

The knurling won't reduce turbulence, it'll increase it. (Just think about it!) It can have a beneficial effect, but probably only at speeds where the flow separation would have been delayed all the way to the tailcone. That is why you see turbulators on the front portion of a wing: to induce turbulence before the aft of the wing where flow separation would increase drag. The Reynolds number of a small supersonic rocket is much, MUCH higher than necessary to get turbulence instantly upon the nose striking the air, so the knurling would only cause shockwaves to form while flying supersonic, inducing additional drag.

https://en.wikipedia.org/wiki/Turbulator

If anything I said is wrong, please correct me with a satisfying explanation, but I can't find it in me to believe that the knurling could possibly reduce turbulence.

Click to expand...

Turbulators on most wings are located aft of the midsection. In senza's case, the knurling on the tailcone will not eliminate drag on its own. Rather, it will create turbulent airflow over the cone which will adhere to it instantly (laminar flow) this flow will then channel right down to surround the motor exhaust and sortof encase it.
the idea of leaving the knurling in place is to create turbulent airflow just for that purpose, not to eliminate it.

Adrian A said:

Cool. Are you going to put a 38mm airframe tube over the whole thing to make a main chute holder/cannon? If you do, and it extends down to the top of the motor, it could provide support to prevent the av-bay from snapping off of the top of the motor after touchdown.

Click to expand...

interesting idea. I like it, but im not sure how well that would work out in a small nosecone like this. There is a knurled grip section on the forward closure that is a good bit larger in diameter than the rest, so that tube would have to be bigger even than 38mm, Im afraid.

There is the idea of a 75mm version of this bird lingering in my head for the next few years, based around the KBA M1450W. I will keep that idea in mind

Frozenferrari said:

Turbulators on most wings are located aft of the midsection. In senza's case, the knurling on the tailcone will not eliminate drag on its own. Rather, it will create turbulent airflow over the cone which will adhere to it instantly (laminar flow) this flow will then channel right down to surround the motor exhaust and sortof encase it.
the idea of leaving the knurling in place is to create turbulent airflow just for that purpose, not to eliminate it.



interesting idea. I like it, but im not sure how well that would work out in a small nosecone like this. There is a knurled grip section on the forward closure that is a good bit larger in diameter than the rest, so that tube would have to be bigger even than 38mm, Im afraid.

There is the idea of a 75mm version of this bird lingering in my head for the next few years, based around the KBA M1450W. I will keep that idea in mind

Click to expand...

Here's my 75mm version.

https://www.rocketryforum.com/showthread.php?t=26383&page=6

What I had in mind for yours was just having the 38mm airframe tube slide down as far as it will go, and butt up against the top of whatever parts it doesn't fit over, and then maybe retain it to your inner coupler tube assembly with some screws. I really like having a chute cannon for the main chute; it's my most successful recovery configuration, by far.

Edit: I see now you were planning for single deployment. The chute cannon would give you dual deployment with your current rocket length and single 54mm airframe separation. The 38mm airframe tube would only go up as far as would fit under the nosecone taper. I'm not sure where that would wind up for your rocket, though.

Looking good! Where did you get your CF tube?

yeah, your design is similar. I do like the method of zig zagging that shock cord and taping it down. Not only is it compact, but it works well for shock dampening as well.
How the heck did you only pull 31k from that bird tho? it looked like it could pull a good 40. cold day? It was an M wasnt it?

I got the tube from my local dealer. its a Performance Rocketry tube.

Frozenferrari said:

How the heck did you only pull 31k from that bird tho? it looked like it could pull a good 40. cold day? It was an M wasnt it?

Click to expand...

:roll:
It was a CTI L1115, and it broke the L altitude record. I'm still an L2, but I'm planning to go for the M record on an L3 cert flight at Balls this year.

Oh okay haha. Yeah man the M record would be cool, but you're up against some serious rockets then. Falcon, which is Von Delius's M alt rec bird, is a seriously mean machine. he has a custom made nose and everything. flying casings will always go higher than airframed birds, but i personally dont like em. Anyway, his birds are crazy performing, and they shred sometimes because or it. i kept senza's fins above a 1.5-2.0 stability margin (barrowman) so i could fly a good variety of motors. Kurt's Kmaxx fins are ridiculously small, and i bet he totters on .5 or less. I wont give numbers, but belive me, theyre itsy bitsy little things.

If you wanna take that M record youre probably gonna have to cut down on its weight a bit. Youre using a 6G right? M2020Im has potential. KBA M1450W holds it right now because it has a little over 8Kns . ... and that was with a superlight flying casing with some carbon parts on it.
I think the keys to extreme altitude are quite simple- burn time, weight, drag (fins, tailcone, nose shape) and then lastly power.

I hear Aerotech has a backburner project- 75/10240. Karl told me that they already had some cases... hehe

Frozenferrari said:

Oh okay haha. Yeah man the M record would be cool, but you're up against some serious rockets then. Falcon, which is Von Delius's M alt rec bird, is a seriously mean machine. he has a custom made nose and everything. flying casings will always go higher than airframed birds, but i personally dont like em. Anyway, his birds are crazy performing, and they shred sometimes because or it. i kept senza's fins above a 1.5-2.0 stability margin (barrowman) so i could fly a good variety of motors. Kurt's Kmaxx fins are ridiculously small, and i bet he totters on .5 or less. I wont give numbers, but belive me, theyre itsy bitsy little things.

If you wanna take that M record youre probably gonna have to cut down on its weight a bit. Youre using a 6G right? M2020Im has potential. KBA M1450W holds it right now because it has a little over 8Kns . ... and that was with a superlight flying casing with some carbon parts on it.
I think the keys to extreme altitude are quite simple- burn time, weight, drag (fins, tailcone, nose shape) and then lastly power.

I hear Aerotech has a backburner project- 75/10240. Karl told me that they already had some cases... hehe

Click to expand...

My M2020 RASAero sims are well over 50kft, assuming the rocket will hold together. I'm working on some high-temperature materials testing to help with that. I don't think any altitude records are held by flying casings, but I don't know that anyone has seriously tried. I'm guessing the extra drag from the discontinuities would exceed any other benefit. Personally, I think small fins are over-rated on record attempts. Keeping the angle of attack small is more important than the small increase in wetted area.

This included various custom parts such as the custom milled 6061 tailcone, the Dragonplate Quasi-Isotropic Carbon Fiber fins, etc. as well as your "standard" rocket parts.

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Did Dragonplate cut out your fin shape, or did you simply get the stock from them?

Great looking project!



Justin