L3 Build - Project Icarus

[babp1011]

Some background on myself. I've been into high power for about 6 years now. Got my L1 with NAR and then was quickly addicted and got my L2 about a year later. Not too long into flying with my L2, I got the need for speed and made the jump into MD rockets. My first project was the Kestrel from John Wilke at 3DogsRocketry. It was a great first kit for MD and John and I had many an email back and forth so I could perfect my design. The Kestrel had many successful flights before I wanted to challenge myself. I did tons of research on TRF and decided to try my hand at a 2 stage 54mm-38mm MD flight. I used the Kestrel as a booster staging to a Blackhawk 38. I test flew the Blackhawk to make sure everything would work, then moved on to the full stack. The up went perfectly. I recovered the sustainer just fine, from 18k, but a failed apogee charge caused the booster to come in ballistic. Everything but the interstage coupler was completely recoverable, so it lived to fly another day. Now that I have been flying for a while and have been seeing some amazing MD rockets put up by many of TRF'rs, I got the itch to go for a larger MD project, specifically a 98mm minimum diameter rocket.

A few months ago I was thinking through all of the space saving measures I have seen here and decided to build a rocket to test out some of my ideas. While I am not an L3 yet, the lessons learned with this rocket will directly influence the design of my L3 cert rocket. NOTE/DISCLAIMER: This will be a slow build as I currently live in Chicago but am building the rocket back in southern California at my parents house. Simple reason is all my rocket materials are there and Lucerne Valley is a quick drive away and offers a nice high altitude waiver for testing.

The overall rocket design will be fairly straight forward. 60" FG airframe with large fins capable of flying everything from a soda can K to a 5G or 6G load. Positive motor retention will be completed with a bulkhead epoxied into the airframe to allow a threaded rod to pass through with an eye nut securing everything in place. There will be one airframe break with drogueless dual deploy recovery. The area that will be the most work is the nose cone.

To save space I had a few goals. 1) The nose cone has lots of space, let's use it! 2) Attempt to keep it as simple as possible 3) Make the whole set-up easily removable. I'm using a Performance Rocketry 4" filament wound nosecone to start. My parachute of choice will be a 48" Fruity Chutes Iris with kevlar shock cords to reduce the parachute size while still retaining a great decent rate on many 98mm motors.

My plan is to house the parachute in a 75mm airframe body, secure the electronics on top (looking like those will be a Raven 3, AIM GPS, and a ComSpec RF Transmitter) and retain the whole assembly using 6, 6-32 steal threaded rods epoxied in the airframe shoulder with JB Weld. I have already started that process and attached some pictures below. I will add guides to the outside of the 75mm tube so the whole assembly can't wiggle around in the NC shoulder. Now, the reason for putting the parachute in the tube is so I can a) perform a drogue-less dual deploy with one airframe break and b) use reliable piston ejection to get the laundry out and in the air. Now you may be asking yourself, "With the parachute in the NC, how will it attach to the main recovery harness. Or for that matter, what will the recovery harness even look like??" Excellent question!

The main recovery harness will consist of 1/2 inch kevlar cord will run from a quick link attached to the eye nut mentioned above to the nosecone. The end will attach to the nose cone by being epoxied the full length of the NC shoulder. I decided this for two reasons. First there isn't enough space between the wall of the shoulder and the outside of the 75mm tube to have a fixed attachment point. And second, the nosecone won't bear the main force of recovery, it will only need to support its own weight. Now, for how the parachute will attach. Because the bottom loop of the parachute's shroud lines is relatively narrow, I can pass them through the drilled opening in the bottom bulkhead of the 75mm tube. There, it will be attached via a quick link to a short (3-4 foot) section of 1/2 inch kevlar that will then be attached to the main recovery harness between the motor and the nosecone. I will leave enough play so that no matter what happens (theoretically), the parachute can't get pulled out prematurely. And now for the bulkhead that is now attached to the parachute after ejection. Luckily there is a thick knot several inches above the bottom loop that will be thicker than the opening in the bulkhead. This will stop the bulkhead from traveling up into the shroud lines, staving off the possible disaster of an unopened parachute. If this is all hard to follow, I will try to summarize the recovery scheme and in a short and sweet manner.

Kevlar joins motor to nosecone. Parachute sits in tube in the NC and is connected to main recovery harness with short section of kevlar. The parachute tube is as follows (from bottom to top): Bulkhead held in place with sheer pins, space for parachute, piston for ejection, back bulkhead held securely in place with screws, upper nosecone with space for electronics.

Now for ejection. The main and main backup charges will be connected into the parachute tube using some all-thread and nuts. It's a simple solution I first learned from Adrian that allows for successful pyro events with no worries of blowback. The apogee and backup apogee charges will be run down separate sides of the parachute tube into the main compartment.

Right now I am focusing on the building of all the nosecone parts as those will be the most time consuming. As I get through those I will focus on the remainder of the rocket. As I said, the build will be long, but I plan to document everything here as I go. Any tips/suggestions/comments are always greatly appreciated.

Phil

 

[Burner]

Good luck Phil, I'll be following along.

 

[babp1011]

Thanks James. I've learned a lot from you and your builds over the past few years. I'm hoping to get the remaining parts list solidified and everything together over the next few months.

 

[babp1011]

After much planning a decision making I have decided to use this rocket for my L3 certification. While I was back in California for the recent holidays I made some great progress on the build. My main focus was reinforcing the fins with 6oz. carbon fiber and getting them attached to the airframe. I have to give credit to Giant Leap Rocketry for their amazing workmanship on the fins, the beveling was perfect.

I decided to use the Tfish method of 1/3, 2/3, and a final tip-to-tip layer to reinforce my fins. To get a good bond of the first two layers I decided to bond them to each fin prior to attaching them to the body. I used a convenient (aka my mothers) vacuum saver food system to apply pressure to the layup while it cured. I chose Aeropoxy for the layup due to the properties of the resin I have read about on several occasions on this forum.

Picture of the first layer being attached. The blue tape was used to make sure excess epoxy did not run all over the fin. This was removed prior to vacuum bagging.



All three fins completed.



This picture shows the smaller template over the top of the final product so you can see the size of the first two layers.



The next step was to attach the fins to the body tube. I had the tube pre-slotted for the fins. Although this will be a minimum diameter rocket, I like the idea of having the fin sitting slightly inside the body tube. I used two foam boards to make sure the fins were properly aligned while curing. One for the front and one for the back. this method was repeated for all 3 fins.



Next step were fillets made with Proline epoxy. For some reason I can't find the picture of the cured and sanded fillets. All I came up with was the initial layout with tape. So here's some tape!



After all of the fillets were done and sanded I proceeded to the final layer of tip-to-tip carbon.



Since this rocket will go high and fast, I am going to use proline high-temp epoxy to protect the leading edge. In an attempt to prevent delamination in the mach region, I chose to cut away the final tip-to-tip layer from atop beveled edge once the epoxy had gelled. The final product came out pretty well. A cut a little further away from the end of the bevel on the first set of fins, but nothing that can't be fixed.



All in all I think the finished product came out pretty well.



I ran out of time during my trip to fully complete the Proline leading edges, but I will be able to get to that in the future. I also completed the parachute section that will fit in the nose, complete with front and rear closures and piston ejection. I took a few full mock up photos. Can't wait to finish it and see it fly!


Phil

 

[rocketgeek101]

Great looking bird! I like how you did the t2t, leaving the forward and trailing edges uncovered. Adds a bit of style!

 

[Aksrockets]

Absolutely love it! I hope she flys as good as she looks! Best of luck with the L3.

Alex

 

[babp1011]

Thanks for the comments! I'll make sure to update the thread as more gets completed.

Phil

 

[babp1011]

I was able to get back to California and work on the rocket a little more. Now that I live in Chicago, I made the decision to move everything out to the Midwest (where I now live) and do my L3 Cert flight with the Indiana Rocketry Group. This means the rocket will get done faster and hopefully able to fly near the end of summer. Alright on to the pictures!

This first one is of the completed parachute bay set up. On the left is the housing with the centering ring epoxied in place. This will allow me to bolt it into the nose cone shoulder. At the top you can see three tabs I epoxied in place to keep the entire piece centered. On the right are the internals. The top is secured with six screws to captive nuts to hold it in place when the ejection charges fire. Below that is the piston. And last but not least, the bottom bulkhead. This will be held in place with a couple of sheer pins.



Next photos are of the whole set up installed in the shoulder. I have not epoxied the shoulder into the nose cone as of yet as this was the easiest way to test the fit and build our the design.



I also got to work on the electronic sled that will sit atop the parachute bay. One side will hold a Raven 3/Power Perch and two batteries to power the AIM XTRA GPS that sits on the opposing side. I still need to play with the layout of the AIM XTRA side. I will need two featherweight magnetic switches to power up the batteries for the computer and the pyro channels separately and I only had one. I built some walls on the Raven side to house the batteries. I will most likely use a zip-tie around the sled to hold them in place during flight.



I am thinking about using small all-thread and bolts (similar to the featherweight av-bays) to transfer power from the electronics to the charges in the main parachute bay and the body for apogee. This will allow for permanent fixtures and ease of wiring as well as making sure the electronics are sealed off from any ejection gases. I figured this would work just fine for the parachute bay, but I am a little worried about having so many holes drilled in the narrow centering ring. It is double the thickness, but 10 holes seems like I could be pushing it (6 for retention, 2 for main charge, 2 for back up). Any thoughts?

Phil

 

[babp1011]

It has been way too long for an update on this thread. Now that I have everything in Illinois, I've been slowly working through things. As you can see in the previous photos I left the leading edges bare of carbon. This was to build a tapered leading edge out of JB Weld.

The first thing I did was use a flat piece of aluminum to create a clean edge.



Most areas only required a small fill to get a clean line. Other areas required a little more, that's what I get for doing the cut free handed.

After doing this to all fins I then applied JB Weld across the entire leading edge and used a straight edge to taper it down to the tip of the fin. After they were dried, I did a little sanding to smooth out some slight unevenness. I may do a thin skim coat to get the edges perfect, depends on how much I want to fuss with it.



I have been ordering a few parts from McMaster Carr to complete the av-bay. More on that to come.

 

[babp1011]

I was able to make a fair amount of progress this weekend on the av-bay. Hoping to get this all buttoned up this weekend so I can epoxy the shoulder into the nose cone once and for all.