outside body tube wire on rocket going past Mach 1: For SLI rocket need input quick

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dknight

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The Statesville Christian School SLI team I coach has a slight problem. Our rocket is heavy. We need it light to ensure it goes past Mach 1 (K1440 Cesaroni motor and 4" diameter body tube) Unfortunately, we have to run wire outside of our rocket to the top and bottom from a payload section. On both sides 180 degrees apart. Tried copper conduit: too heavy, way too heavy. Tape is our current option, right now packaging tape but leaning to maybe gorilla tape. Got a hold of some very small diameter, just little bigger than copperhead igniter, tubes. Would have to epoxy them to the body tube thought. Weight! Not much but more than tape with epoxy.

To give you an idea of our mass situation, we are skinning the metal off of our 9 V batteries to aid in weight reduction and going with lithium 9V also. They are lighter than standard alkalines. Quiet simply, the lighter the rocket, the faster the max velocity and greater probability our science payload works. www.teamstatesville.com

Any ideas?? With the brianical IQ of this group, I have faith a good, quick easy solution will show up. Not being a smart*** either.

Doug
 
It would have to be very streamline and preferably balanced on with a similar weight on the other side (not necessary but recomened). The hole the wire comes out of would have to be small otherwise mach pressure COULD, NOT WILL cause a separation.

I wouldn't use gorilla tape, way too draggy. Thin packing tape would be better but probobly only last 1 launch if that. The thin tubing run on the outside along the body would be the best solution for no problem to occure accept that it is the heaviest solution. This is where the opposite weight comes in on the other side, therefore doubling the weight of the whole tubing contraption.

I have had multiple "permanent" decals rip of mach rockets at the max acceleration point.

1. Tape is pretty draggy if you are looking at .8 mach and up.
2. Wire holes have to be tiny.
3. Streamline.

Quick question, why do you need to run wires outside of vehicle? Are the wires permanent? If they are, you can epoxy them along the side of the rocket.
 
Perhaps a strip of light fiberglass cloth epoxied over the wire for its entire length?
 
That would definately be the best sollution but, we don't know if he wants it to be permanent.
 
Thanks for the responses.

Permanent is not the issue. Just making it work this one flight is my concern right now. The drag issue with gorilla tape is worrisome. The plan is to have two sets of wires on opposite sides of the rocket for symmetry issues. We have thought of fiberglasses but again, weight is an issue. Five to 10 grams , 20 at most would suffice but more than blows our mass budget. This problem must be solved though.

Doug k
 
Why so concerned about weight?

Something like a K1440 really doesn't care about an extra couple ounces...
 
If the wires can be permanent, then I would do an EXTREMELY THIN layer of epoxy over the wires.

May I ask why you have wires outside of your rocket in the first place? That is what is kind of losing me.
 
Basically the wires are outside of the rocket because we didn't put them inside the rocket in the first place as we should. After the rocket was put together in the manner it was, we really couldn't, based on time and budget, get a hole, conduit, etc, to make an internal wiring system for the rocket. Our bad, we're living with what we have and trying to make the most of it. The epoxy idea was floated at the launch site today. What we probably will go with. But wanted to hear some other ideas. Have to do this tomorrow with Tuesday a pack day to Huntsville.

As opposed to why can't the K1440 not worry about an ounce or two, based on our Rocksim simulation, we is pretty exact, it does. At 12 lbs, the rocket will hit Mach 1.1 according to the simulation, at 13.5 lbs, the rocket hits Mach 1 according to the simulation. With simulations being as they are, GIGO, we are trying to get to at least Mach 1.1, hopefully more, so that the rocket has a decent chance of hitting at least Mach.
 
Sorry this didn't occur to me when we talked yesterday at the field - what about using FLAT speaker wire? The stuff is designed to hide under paint on living room walls. It's super thin and comes in various sizes.

Try the links below for more info and call local stereo or video installers to find a local source. I'm sure you could think of a way to glue this one without adding a lot of weight. If you paint over it with a good paint you can make it virtually disappear.

The Invisible Wire

NEWS FLASH - This is even better: 26gage 4 conductor 1/32 inch thick!
Taperwire

The speaker wire is still thinner (some claim to be .012 inches thick) so that may be best if you need only two conductors per run.
 
What's the tube material the main rocket is made of Doug? If it's paper then you could get away with joint compound or wood glue. If it's phenolic... I'm not sure what's light and strong but with super thin materials maybe you could get by with thinned laminating epoxy used as a "clear coat" of sorts.
 
Now this flat speaker wire is THIN.

0.004 inches thick. Bad news is it weighs almost a lb for 25'. So I stand by my comments about the four conductor alarm wire 26/4 that I posted. That may be the best - light and reasonable size.
 
You can use copper enameled wire. They are available in different diameters, including very thin diameters (down to ~0.001”). It depends on the amount of current that you want to transfer over it.

Reinhard
 
Go to hobby lobby, in the doll house section you will find a tape with two flat copper strips that is made to conduct power in doll houses. Its flat, strong, and got good adhesive.. I used in my daughters doll house and it conducts power all troughout ...


d

cir-kit is the maker.. here is an exerpt from there online catolog..
Tapewire



Select an Item A. CK1000 30' Roll 2 Conductor + $US13.90 B. CK1001 15' Roll 2-Conductor + $US7.00 C. CK1002 5' Roll 2-Conductor + $US2.70 D. CK1017 50' Roll 2-Conductor + $US21.96



Click Here


Our double conductor tapewire is the "heart" of all Cir-Kit wiring systems. From its introduction in 1976 to the present it has been the predominant method of dollhouse wiring. Its use creates a printed circuit type layout and completely eliminates the congested wiring found in conventional systems. A super strong adhesive, exposed by the removal of a peel away paper carrier, ensures a secure grip on any surface. Since the copper foils are sandwiched between two layers of transparent tape, the tape may be applied even over bare metal. The exposed transparent tape has a matte finish allowing easy application and retention of paint.

Several major improvements have been incorporated into the design and manufacture of the Cir-Kit Concepts' tapewire. The most significant is color coding of the copper foils. This new feature greatly simplifies the making of corners during the wiring process. Brass brads are installed only at the blue-to-blue and copper-to-copper overlap points, eliminating any possibility of short circuits at these locations. As great an idea as color coding may be, if the colors are too intense they will bleed through light wallpaper or paint and appear as unwanted ribbons of color. To ensure this doesn't happen, the one colored foil is made of a light pastel blue for easy masking.

Another problem that occurs with other, lesser quality brands of tapewire is "bubbling". This is a phenomenon that takes place once the tapewire is in place. As time passes, the transparent overlay begins to buckle causing ripples that eventually show through the wallpaper or paint coverings. Using a special manufacturing process, Cir-Kit Concepts has completely eliminated this problem. A tape run made today will appear as straight and true in a year as the day it was laid. The Cir-Kit Concepts' name is also embossed on the natural copper foil to identify it as the one and only Cir-Kit Concepts' tapewire product.

The main body of the tape is 5/8" wide with a total thickness of approximately .005". The copper foils will carry up to 5 amperes of continuous current.
 
Doug - have you seen the flat aluminum duct tape (the sheet metal tape not the sticky plastic/cloth stuff)? Maybe that would work if you cut it carefully. You could run it inside the tubes and come out where you had to - the slits you would need to pass it in and out would be small and the wire would be flat and self adhesive. I'd still go over this with something to ensure that it stayed in place.
 
Everyone,

Thanks a lot for the ideas. We are going to test some smaller gauge wire this afternoon and probably use some thinned epoxy to adhere it to the body tube (phenolic) This really has to work only once right now and at this precise moment in time, this is our solution path. We do have some time at Huntsville in the evenings and night to work if needed but don't really want to if possible.

The flat speaker wire idea I really like. Don't know if time or current load wll allow if but will look into if possible.

Thanks again for your ideas. Helped much.

Doug K
 
Originally posted by dknight
Everyone,

Thanks a lot for the ideas. We are going to test some smaller gauge wire this afternoon and probably use some thinned epoxy to adhere it to the body tube (phenolic) This really has to work only once right now and at this precise moment in time, this is our solution path. We do have some time at Huntsville in the evenings and night to work if needed but don't really want to if possible.

The flat speaker wire idea I really like. Don't know if time or current load wll allow if but will look into if possible.

Thanks again for your ideas. Helped much.

Doug K

Good Luck Doug - go get 'em!

BTW - The flat dollhouse wire is available at Hobby Lobby and says that it can carry 5 amps (at ? volts). That should help you decide. The flat speaker wires should be able to carry many amps - as much as 18ga zip cord.
 
Not sure what the setup is currently but you could make a slot in the body tube for the wire to fit in (like a channel) and seal it with epoxy. Then you could sand it down smooth with the body. I think of it as embedding the wire into the side of the rocket. I'd use two exacto blades with a nickel between the two and a pair of vise grips to hold it together. Use the edge of the nickel as a depth guage.

That's just my suggestion...probably not the best but it's from an uneducated standpoint...
 
Originally posted by dknight
Basically the wires are outside of the rocket because we didn't put them inside the rocket in the first place as we should. After the rocket was put together in the manner it was, we really couldn't, based on time and budget, get a hole, conduit, etc, to make an internal wiring system for the rocket. Our bad, we're living with what we have and trying to make the most of it. The epoxy idea was floated at the launch site today. What we probably will go with. But wanted to hear some other ideas. Have to do this tomorrow with Tuesday a pack day to Huntsville.

As opposed to why can't the K1440 not worry about an ounce or two, based on our Rocksim simulation, we is pretty exact, it does. At 12 lbs, the rocket will hit Mach 1.1 according to the simulation, at 13.5 lbs, the rocket hits Mach 1 according to the simulation. With simulations being as they are, GIGO, we are trying to get to at least Mach 1.1, hopefully more, so that the rocket has a decent chance of hitting at least Mach.

RockSim was developed for subsonic flight simulation, the drag analysis will be way off for a supersonic flight. You will probably need to get past Mach 1.5 in RockSim to assure a Mach busting flight. You need to use another method to estimate the drag coefficients for trans-sonic and supersonic flight.

Bruce S. Levison, NAR #69055
 
The slot idea is a new one. With our body tube thickness, it isn't feasible but I will keep that one in my bag of tricks.

RockSim was developed for subsonic flight simulation, the drag analysis will be way off for a supersonic flight. You will probably need to get past Mach 1.5 in RockSim to assure a Mach busting flight. You need to use another method to estimate the drag coefficients for trans-sonic and supersonic flight.

Very interesting. We used it to simulate our Apogee Aspire machbusting flight and we pushed through Mach decently (1.1 to 1.2 or so due, much uncertainty due to our 10 Hz altimeter sampling rate) when the simulation said we should be hitting about Mach 1.4 or so. Discouraging. Since we are just trying to get over Mach, at what point does Rocksim start to diverge from reality? Is it off by 10% at Mach 1.0, 20% at Mach 1.5, etc. Is this divergence curve linear or increasingly parabolic? Does it start to diverge near Mach?

By transonic, I assume you mean starting at Mach 0.8. Is that true? If so, doubt we'll do the deed. I do wonder, would this mean that RockSim over or under estimates our altitude? Right now,we have it hitting about 6800 ft? We haven't painted the rocket and wonder if that would help?
 
Brad,

Thanks for the legwork on this. Even though we probably won't use any of these solutions, the next stage of this project will use one of them probably. We want to do some more flight for testing if we still believe this rocket can hit the speed we need. Guys like you are why I love rocketry, not just the physics and engineering but the camaraderie.


Doug K
 
Originally posted by dknight
The slot idea is a new one. With our body tube thickness, it isn't feasible but I will keep that one in my bag of tricks.



Very interesting. We used it to simulate our Apogee Aspire machbusting flight and we pushed through Mach decently (1.1 to 1.2 or so due, much uncertainty due to our 10 Hz altimeter sampling rate) when the simulation said we should be hitting about Mach 1.4 or so. Discouraging. Since we are just trying to get over Mach, at what point does Rocksim start to diverge from reality? Is it off by 10% at Mach 1.0, 20% at Mach 1.5, etc. Is this divergence curve linear or increasingly parabolic? Does it start to diverge near Mach?

By transonic, I assume you mean starting at Mach 0.8. Is that true? If so, doubt we'll do the deed. I do wonder, would this mean that RockSim over or under estimates our altitude? Right now,we have it hitting about 6800 ft? We haven't painted the rocket and wonder if that would help?

It all depends on the design and configuration of the rocket and even the altimeter that you use, visit:

https://www.transolve.com/Transolve/Files/Testbench/001/Testbench001.html

Unless you want to buy and learn some more software, the best you can do is make the flight and try to get some data and then confirm the data with a second flight or an independent speed/velocity measurement of the first flight.

The finish on the rocket can help reduce the drag, what are you going to paint it with? How smooth can you get the painted surface?

Bruce S. Levison, NAR #69055
 
The altimeter is an ARTS 2 which is 10 bit I believe. Am going to look at raw data if I can and do the analysis from that information. Do not know what smoothing function will be used on the data as of yet.

The rocket currently is naked but we plan to at least put some clear coat on it to smooth it up. This seems to help coasting altitude much more than max velocity, according the simulations, though.

Doug K
 
Just use mylar packing tape or Scotch tape.

There will be no severe heating and there is little stress on the side of the airframe. The tape will keep the wire flat and out of the boundary layer which is what you want to do.

Bob
 
Originally posted by dknight
Thanks for the legwork on this. Even though we probably won't use any of these solutions, the next stage of this project will use one of them probably. We want to do some more flight for testing if we still believe this rocket can hit the speed we need. Guys like you are why I love rocketry, not just the physics and engineering but the camaraderie.

Anytime Doug... anytime. Remember you scare me!

:p

LOL... I'm kidding of course.
 
Originally posted by teflonrocketry1
RockSim was developed for subsonic flight simulation, the drag analysis will be way off for a supersonic flight. You will probably need to get past Mach 1.5 in RockSim to assure a Mach busting flight. You need to use another method to estimate the drag coefficients for trans-sonic and supersonic flight.

This is actually useful for me to know. I have been worried about a couple of designs that I felt were too close to going transonic and knowing that I might have some breathing room is great to know.

What software do you know of that will model this correctly?
 
I still wonder about the amount of divergence. The worrisome part with this is that is RockSim Pro or whatever it will be called available to accurately measure transonic and/or supersonic flights. What is the use of splash probability calculations if the simulation isn't representative of the flight.

Not knocking Rocksim. Just wondering.

The K1440 gives me hope though. Will be my first K flight. Have heard this engine really rips. Hope so.

Leaving tonight. Will let you guys know what happens. Even if it is ugly.

Doug K
 
If its constructed like normal and the wires are streamline, then it should be fine.

But you will need some quick reflexes to catch an image of that rocket taking off on that motor. Unless you have a highspeed multishot camera.
 
Wires are streamlined and used superglue for attachment a bead of epoxy on over the top. Very thin bead. My camera does 30 fps at 640 x 480 resolution. May do this or go burst mode. Don't know yet.

Doug
 
both those will suffice. I would personally use the 30 fps because its a better chance of getting it if it delays on the launch.
 
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