Going for 100,000 Feet

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EeebeeE said:
. Plus, CTI makes a tapered 29mm aft retainer than comes up to flush with a 29mm airframe. Unfortunately, apart from heavy sanding and grinding of aircraft-grade aluminum, that means that the sustainer needs to be coupled to the booster externally, rather than internally. So I am fabricating a sleeve that will be glued to the interstage coupler. The sleeve will extend 1.5" from the coupler and the sustainer will slide inside it. and rest on the end of the coupler.

View attachment 298321
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Man I hate to tell you this...after all the work you did....but :

Your totally wrong about the tapered closure, it is in fact, made for STAGING..... it is flush with motor case, not airframe. No need to grind/sand anything. It already fits. You would just have to glue a motor block in your airframe, to keep motor in place.

Her's mine:
It comes with a ring/washer that goes over the threads and THAT is flush with airframe.

DSCN5955.jpg DSCN5956.jpg

Here's mine easily sliding in/out of a 29mm motor tube...

Hopefully it's not too late, sure makes for a simpler/neater way to do it.

I must add this...at least MINE came that way, I don't think they have changed it.
 

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Thanks guys. Don't know why I looked at that wrong. That does present a challenge, however, because now I need to retrofit everything.
 
You better make sure you can get one before changing up again.
Considering the current state of affairs with CTI...........

It will make for a "slicker" drag separation at motor burn out, and yield some higher altitude with less hassle. If you can find one.
 
blackjack2564 said:
You better make sure you can get one before changing up again.
Considering the current state of affairs with CTI...........

It will make for a "slicker" drag separation at motor burn out, and yield some higher altitude with less hassle. If you can find one.
Click to expand...

Agreed. I'm not going to do any cutting until I know for sure.
 
After a lengthy delay caused by a high workload (need to earn money to build rockets), I got back to work on this project. Thanks to Robert DeHate at AMWProX who sold me a thin epoxy specifically designed to soak deeply into glass fibers for T-to-T fin applications. Tried the first application on the booster, and the product is awesome. It sets completely clear so you can see the outline of the original fin, and it appears it is going to be very easy to sand.

I will take photos of the next application. I am going to sand between applications to control spillage. First time I had a lot of excess that dripped around, so to combat that I will use less epoxy and will also tape over parts that I do not want to have to sand globs off.
 
EeebeeE said:
After a lengthy delay caused by a high workload (need to earn money to build rockets), I got back to work on this project. Thanks to Robert DeHate at AMWProX who sold me a thin epoxy specifically designed to soak deeply into glass fibers for T-to-T fin applications. Tried the first application on the booster, and the product is awesome. It sets completely clear so you can see the outline of the original fin, and it appears it is going to be very easy to sand.

I will take photos of the next application. I am going to sand between applications to control spillage. First time I had a lot of excess that dripped around, so to combat that I will use less epoxy and will also tape over parts that I do not want to have to sand globs off.
Click to expand...

Any more info on the epoxy? I am curious as to what brand it is. Did you use any peel ply or vacuuming? What's the glass to epoxy ratio?
 
Here are some photos of my T-to-T process. Since this is a small rocket it will differ from other efforts. First as I mentioned earlier, Nat at Upscale CNC made some fin alignment guides for me that also double as a tray to set up the T to T. Two plywood slats go across the two guides to create a cradle perfectly set up at 120 degrees.

This is the epoxy, made by US Composites. It is their "Thin" compound and is 3 parts resin to 1 part hardener. I have been mixing 3 grams of resin, and 1 gram of hardener and it seems to very effectly jo the job without much waste and without too much being on the fins.
Do 008 - Epoxy.jpg

Sections of the airframe and the backs of the fins to be epoxied are taped off to prevent extraneous lumps of epoxy. Saves on sanding. I had 3" FG "tape" leftover from a boat build that works perfectly. both edges of the tape are woven to prevent fraying so I lay sections out so that the woven edges are fore and aft. Any fraying of the cut part happens beyond the chord tip of the fin.
Do 008b.jpg

The FG is epoxied into place using small pieces of wood to ensure that they are tightly connected to the fillets.
Do 008c.jpg

A thought I had was that I wanted the plastic laying over the fins to be as evenly covered as possible. I was using lead shot to apply the pressure, but I wanted something to ensure as smooth of surface as possible so I would not need to sand through dimples created by the shot. So I spread simple cooking flour across the plastic on top of the fins. It compresses real nicely into a very even and smooth surface. Then, I put a small amount of lead shot into a Ziplock bag (about 3 pounds) and laid it across the flour. A couple blocks of wood and the coffee container holding another 17 pounds of shot, and everything should be very nicely compressed when it sets. I'll photo the finished product after I let the epoxy set for the night.
Do 008d.jpg Do 008e.jpg Do 008g.jpg

This is a 29mm Min. Dia. rocket and the T-to-T is probably a little overkill, but I am doing this to practice on the technique for the larger rockets in this project.
 
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EeebeeE said:
Here are some photos of my T-to-T process. Since this is a small rocket it will differ from other efforts. First as I mentioned earlier, Nat at Upscale CNC made some fin alignment guides for me that also double as a tray to set up the T to T. Two plywood slats go across the two guides to create a cradle perfectly set up at 120 degrees.

This is the epoxy, made by US Composites. It is their "Thin" compound and is 3 parts resin to 1 part hardener. I have been mixing 3 grams of resin, and 1 gram of hardener and it seems to very effectly jo the job without much waste and without too much being on the fins.
View attachment 304884

Sections of the airframe and the backs of the fins to be epoxied are taped off to prevent extraneous lumps of epoxy. Saves on sanding. I had 3" FG "tape" leftover from a boat build that works perfectly. both edges of the tape are woven to prevent fraying so I lay sections out so that the woven edges are fore and aft. Any fraying of the cut part happens beyond the chord tip of the fin.
View attachment 304885

The FG is epoxied into place using small pieces of wood to ensure that they are tightly connected to the fillets.
View attachment 304886

A thought I had was that I wanted the plastic laying over the fins to be as evenly covered as possible. I was using lead shot to apply the pressure, but I wanted something to ensure as smooth of surface as possible so I would not need to sand through dimples created by the shot. So I spread simple cooking flour across the plastic on top of the fins. It compresses real nicely into a very even and smooth surface. Then, I put a small amount of lead shot into a Ziplock bag (about 3 pounds) and laid it across the flour. A couple blocks of wood and the coffee container holding another 17 pounds of shot, and everything should be very nicely compressed when it sets. I'll photo the finished product after I let the epoxy set for the night.
View attachment 304887 View attachment 304888 View attachment 304889

This is a 29mm Min. Dia. rocket and the T-to-T is probably a little overkill, but I am doing this to practice on the technique for the larger rockets in this project.
Click to expand...

The US Composite 635 is what I use and Irma great. I recommend the pumps. I weigh my epoxy and the pumps make it easy to do the small amounts. I recommend the fast 4:1 hardener for structural stuff. Use the microballoons for filler for fillets. It's a good system.

Where did find the flour idea? Any reason you don't use peel ply with a breather?
 
NateLowrie said:
Where did find the flour idea? Any reason you don't use peel ply with a breather?
Click to expand...

I have used flour as filler for my fillets in modrocs and small HPR. Unlike sawdust it has a very smooth finish to it. After seeing how it clumped together and still completely filled voids, I though it would be effective for this.

As far as not peel plying, I don't really have the experience at it as much as I have at using pressure. It is more of a personal preference. Pressure takes more time, but I am more confident in the result.
 
I was super happy to see this thread rejuvenated. I had been wondering how everything was progressing.

Love the flour + lead shot idea.
 
Tip to tip work is largely done. apart from some every fine sanding around the leading edge of the fin root. It came out pretty nice and pretty even. The CTI aft tapered closure ended up being the same diameter as the motor case, so that will mean some cutting and redesigning a little. Should end up with a slightly shorter rocket than it is right now. Currently a little over 46" long. Recovery for both the sustainer and the booster will be 4" x 40" nylon streamers. Sustainer will be single deploy...I think. Some photos of the finished T-to-T

Do 009a.jpg Do 009b.jpg Do 009c.jpg
 
patelldp said:
I am sure you have done sims on this, but I'd be very concerned with the stability of this rocket. At the very least, I'd be concerned with significant coning.

Have you flown something with a similar small fin profile? I believe Tim Dixon (dixontj93060) built and flew a 2.6" with 54mm mount with equally small fins and had a less than desirable outcome (https://www.rocketryforum.com/showthread.php?67419-The-Great-Built-Kit-Sale&p=737349#post737349)
Click to expand...


OR shows the stability to be at least 2 CA. RAS Aero shows that it dips under 2 CA as it goes through mach, but still remains stable.

This is the stability calculations according to OR. Ito remains above 2 CA stable until just before apogee.

Do 010a.jpg

RAS Aero stability up to the staging event is above 1 CA, but the rocket will stay below Mac 0.8 until after separation. After separation stability is 2 CA at about the time it breaks Mach 1.
Do 010b.jpg
 
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The risk with low profile fins is roll-yaw (or pitch) coupling. The mechanics to model this are beyond the capabilities of OR.

An intro to this is here: https://en.wikipedia.org/wiki/Inertia_coupling

Here is a reference to the roll-pitch coupling failure on early Aerobee sounding rockets
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660029199.pdf

If you have ZERO roll you'll be ok. Or if you have very high spin you'll be ok. Anything in between is not certain. Also I think 4 fins is better than 3 fins in this regard.

If anyone has references on how to possibly model this that would be appreciated for my own high alt project...
 
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jderimig said:
The risk with low profile fins is roll-yaw (or pitch) coupling. The mechanics to model this are beyond the capabilities of OR.

An intro to this is here: https://en.wikipedia.org/wiki/Inertia_coupling

Here is a reference to the roll-pitch coupling failure on early Aerobee sounding rockets
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660029199.pdf


If you have ZERO roll you'll be ok. Or if you have very high spin you'll be ok. Anything in between is not certain. Also I think 4 fins is better than 3 fins in this regard.

If anyone has references on how to possibly model this that would be appreciated for my own high alt project...
Click to expand...

Good points, John, but I think you are underestimating the size of the fins. Here is a side-by-side view of my sustainer with a LOC Nuke Pro Maxx. The NPM is 2.26" in dia. and the fins are 2" wide at the tip. My sustainer is 1.25" in dia. and the fins are 1" wide at the tip. The ratio of fin width on an NPM is 87%. The ratio of my sustainer it isn't much smaller...80% Plus with this particular NPM of mine, which broke Mach 1 when I certed L2, had no nose weight. The total rocket weight 78.8 oz. My sustainer will have 4 oz. of nose weight, bringing the total weight to 24.7 oz. THis is done because the motor extends 1.25" aft to act as a coupler for staging.

The booster is what makes the fins look very small, but again, it will not be attached when the rocket is breaking mach 1.

Do 010c.jpg
 
Evan, I admit I do not know. Dynamic stability is a totally different animal than static stability. For example adding nose weight increases your static stability margin but may decrease your dynamic stability margin. This is an area I need to learn more about as well.
 
jderimig said:
Evan, I admit I do not know. Dynamic stability is a totally different animal than static stability. For example adding nose weight increases your static stability margin but may decrease your dynamic stability margin. This is an area I need to learn more about as well.
Click to expand...

This is something we can discuss at club meetings. It will be more critical as I build larger versions to go to higher altitudes. When the boosters cross mach 1, dynamic stability is going to be a lot more important, because a 2-stage rocket is inherently less stable to begin with. It's part of the reason why I wanted to start small and work up.
 
I haven't worked on this for a while because of other projects, but I am nearing URRF where I want to fly "Do", so I decided to get moving on it. Do will have a single delpoyment sustainer, that will recover with a a 4' streamer. The benefit to this is that I can glue the nose cone to the upper airframe and eliminate a seam. Also, with the e-bay located in the upper airframe, it does not need threaded rod running through it. This helps create a ton of more usable space and allows far more versatility in the AV-Bay configuration.

The electronics I am using for this project will be a Raven 3 altimeter, a Beeline tracker, and a cheap tiny HD video camera I found online (China must be a wonderful place).

I took 4 layers of 6 oz. fiberglass, and epoxied them together to create a very strong but very thin sled (less than 1/64" thick - Pictures later), which is as strong as 1/8" ply but takes up a lot less space. This is critical because the sims all show I need 5 oz. of weight in the nose, and the lead shot/epoxy combination takes up almost all the nose cone space.

Here is my first go-round of laying out the AV bay as well as a photo of the nose cone, upper airframe.

Do 012.jpg Do 011.jpg
 
Glad to see you back at it! I was literally thinking about this thread today as I was starting to solder my electronics together for my first HPR two-stager later this year. Keep up the good work.
 
BDB said:
Glad to see you back at it! I was literally thinking about this thread today as I was starting to solder my electronics together for my first HPR two-stager later this year. Keep up the good work.
Click to expand...

This still needs a 3-function altimeter even though it is SD. I need to have a small charge to separate at booster burnout, a sustainer ignition, and then an apogee deployment. Fortunately, the Raven can handle all of that.
 
Im sorry to put it like this, but you really do need those fin spans to be at least around 110% of the airframe diameter to get them out of the turbulent air flow and in to some clean air to give them any chance of keeping the rocket stable at high velocities. Good luck, I get excited reading about projects that are pushing the limits and hope to one day fly a 2 stage rocket to over 100,000 feet at "Thunda down under 2018" in Queensland Australia
 
Chrisn said:
Im sorry to put it like this, but you really do need those fin spans to be at least around 110% of the airframe diameter to get them out of the turbulent air flow and in to some clean air to give them any chance of keeping the rocket stable at high velocities. Good luck, I get excited reading about projects that are pushing the limits and hope to one day fly a 2 stage rocket to over 100,000 feet at "Thunda down under 2018" in Queensland Australia
Click to expand...

A100% is what I typically start with - it's not a hard and fast rule but a good starting point. Do some studies in RasAero or any sim program to see how fin shape and Cp interact. Span is really important, small changes translate to big shifts in Cp. At the same time you can see how your apogee altitude is impacted by these changes. Everything is a trade off.

Another reason to do this is because of nose weight. If you can move the Cp back another caliber just with fin geometry that can reduce or in some cases eliminate the need for dead weight. Then you can fly more payloads like cameras :)

Good luck man glad too see projects like this out there!
 
RASAero shows this to be a pretty stable flier. After the first stage it gets even more stable. In designs with larger fins I got lower altitudes. This is because when we add the nose weight and the motor weight together, I essentially have a boosted dart until the second staqe fires. The rocket has a ton of inertia. Doesn't go as fast, but harder to slow down. I could actually add another 2 oz. and not lose that much altitude.

This first rocket will fly with the fins that are on it. It won't break mach until after staging and I am not too worried about coning at this altitude. The next size up will probably have a slightly higher fin to airframe ratios, but I am also going to induce spin to increase stability.

BTW...the camera weighs about 12 grams.
 
Chrisn said:
Im sorry to put it like this, but you really do need those fin spans to be at least around 110% of the airframe diameter to get them out of the turbulent air flow and in to some clean air to give them any chance of keeping the rocket stable at high velocities. Good luck, I get excited reading about projects that are pushing the limits and hope to one day fly a 2 stage rocket to over 100,000 feet at "Thunda down under 2018" in Queensland Australia
Click to expand...


Would love to go down to Australia, but I would have to deal with both money and shipping issues. Looks like a great time, though.

I am pushing for altitude by focusing on inertia, not necessarily speed. The ultimate 100K flier will not break Mach 3 and this first flier will not break Mach 2. However the added weight means that it won't slow down as fast.
 
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CoyoteNumber2 said:
What camera are you using?
Click to expand...

A little cheapie I found on e-bay. 1080p, but not the best frame rate. Also the orientation is not perpendicular to the length of the camera so the video will need to be shown sideways. But I should get some decent images at altitude. You can't be too picky when it comes to a very lightweight camera that will fit inside a small airframe. This will actually fit inside a 24mm motor mount tube. When I start using 38mm and 54mm tubes I can increase the picture quality.

Camera.jpg
 
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EeebeeE said:
A little cheapie I found on e-bay. 1080p, but not the best frame rate. Also the orientation is not perpendicular to the length of the camera so the video will need to be shown sideways. But I should get some decent images at altitude. You can't be too picky when it comes to a very lightweight camera that will fit inside a small airframe. This will actually fit inside a 24mm motor mount tube. When I start using 38mm and 54mm tubes I can increase the picture quality.
Click to expand...

That's pretty cool; I will have to check that out more. I'm looking for a camera to go in a minimum diameter 29mm, so far I've gotten a 1080p pen spy cam to experiment with.
 

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