Level 3 Build:Red Dragon

[cdondanville]

So here is a build thread that I will be posting on as I progress on this build. This rocket is going to be my LVL3 certification bird. It will be mostly scratch built fiberglass with some plywood for centering rings and bulkheads. I bought the nose cone from Public Missiles, but I will be rolling the fiberglass tubes with the help of one of my TAPs. I am planning a traditional dual deploy, with an electronics bay in the middle, drogue aft and main in payload. rolling the tubes and coupler for the bay will be time consuming and I have to schedule time with my mentor to do them (thanks Walt) but I hope to complete construction this spring.

Special shout out to my TAPs for their patience, support and assistance as well as the members of Phoenix Missile Works for all their advice and suggestions.

Walt Stafford (Prefect Tripoli #81 Birmingham, AL)
Bob Haas (President Phoenix Missile Works)

and my 1st alternate TAP:

Chris Short (Prefect Tripoli Central Alabama #38)


Some essentials of the project:

Length: 110" or just over nine feet.
Diameter: 6" id airframe
Electronics: Dual PerfectFlite Stratologger SL100
Motor: 98mm Cesaroni Pro98 (3 grain)
Fins: 4 (sorry Tom) right triangular @ 1.5 caliber, surface mount
Target Weight: 28-30 lbs packed before motor




Red Dragon.ork

[cdondanville]

I have 2 flights planned for this bird. A shakedown flight and a certification run. I am getting my motor reloads and hardware from Carey Huff at Huff Performance. The motor is a 3 grain Cesaroni Pro98 case. The planned flights are to be on an L610 and an M520. Yes I said M520. Lets Have a look using a weight of 30 lbs packed before motor:

4842L610 Classic
---------
Weight on the pad: 40.7 lbs
Max Thrust: 210 lbs
Thrust to Weight (max) 5.16
Apogee: 6140'
Max Velocity: 393 mph (Mach 0.52)
Acceleration (max) 4.16g

7400M520 Classic (Moonburner)
----------
Weight on the pad: 44.7 lbs
Max Thrust: 267 lbs
Thrust to Weight (max) 5.97
Apogee: 9899'
Max Velocity: 460 mph (Mach 0.61)
Acceleration (max) 4.43g

Both of these motors have relatively low average impulse for their classes, but they both have a nice initial kick off the pad with the max thrust being way up front on a partially to completely regressive thrust curve. As long as I can keep the weight of the packed rocket under 31 lbs, I should keep a nice 5:1 thrust:weight ratio as I come off the pad. I am shooting for 29 lbs, which should put me just over 10k for the certification flight. It also keeps me well below Mach, which was a goal, I do not want to add that complication to the flight profile for a certification run.

Pro98_dimensions.pdf

L610 Thrust Curve.pdf

M520 Thrust Curve.pdf

[cdondanville]

I ordered a 6: fiberglass nose cone from Public Missiles. I chose them because I had a gift certificate that I won at a raffle! Well that and I know that they have great stuff.



The nose cone came with a plywood bulkhead with an attached U bolt. I took the U bold off and threw it in the parts box. I then drilled a 3/8" hole in the center of the bulkhead, between the 2 U bolt holes and I cut out a 4" diameter piece of 1/2" plywood that would serve as an internal bulkead. It also had a 3/8" hole in the center.

I poured a generous amount of epoxy into the tip of the nose cone then inserted a 3' x 3/8" threaded rod into the nose cone seating it in the epoxy. I then threaded the 4" bulkhead over the rod and slid it down into the nose cone until it seated against the interior walls of the nose cone. (I beveled the edge so it would conform to the contour of the wall of the nose cone and provide a better seal. I then poured another generous amount of epoxy into the nose cone to cover the interior 4" bulkhead. The bulkhead ended up being about 17" from the bottom opening of the nose cone. I threaded the top bulkhead on to make sure everything was centered and let the epoxy cure.



I then created the sled that will serve as the holder for the tracking device. I have not secured tracking, but I know that this will give me a nice place for the bug and the antenna. I used a long thin piece of 1/4" plywood for the sled. I attached 2 small blocks of wood with 3/8" holes on the underside that serve as guides and to hold it securely to the threaded rod. I then fixed the sled assembly to the read bulkhead. I put 2 1/4" eye bolts through the holes where the U bold was attached these will serve as handles for extracting the sled/bulkhead assembly when it is secured and also as a point to tie off the 3/8" eye nut that will serve to secure the bulkhead/sled into position, and also as the attachment for the main recovery harness. (I will tie off the eye nut to the eye bolts to prevent the eye nut from spinning off during recover. Hey, it could happen.

[dixontj93060]

Will be following this build... PML fiberglass nosecones are nice, aren't they?

[cwbullet]

I like the tarcker sled. What are you usign as a tracker?

I would look at your motor selection. With a M520, I would not recommended going above 23-26 lbs.

[cdondanville]

I like the tarcker sled. What are you usign as a tracker?

I would look at your motor selection. With a M520, I would not recommended going above 23-26 lbs.

I do not have the tracker yet, but want to use GPS as opposed to RF. I am looking at the Garmin Astro and the Big Red Bee as possibilities. The Astro is very appealing for its rugged design and ease of use on the field so I am leaning that way, but am still open for options.

I think the math works out on the M530 up to about 30 lbs (and actually the L610 test is probably the limiting factor). My design looks to be about 27 lbs right now. Since I am way over stable, I can always cut down on the length of the payload to trim some weight. I am leaning towards the moonburner for budget reasons. Cary has the case and motor that someone ordered and the reneged on the deal. He is willing to let me have it on a deal since it is kind of an odd ball to have in inventory! I also like the low velocity and stress it brings to a certification flight. Less extreme flight profile, but as you point out, it is a little extreme in the other direction.

[Stymye]

sounds great so far Chris .. will you be flying it at MC2?

[cdondanville]

sounds great so far Chris .. will you be flying it at MC2?

Not sure yet. It may be a little big for Manchester especially if the corn keeps growing and the sod keeps shrinking.

[cwbullet]

M520should be ok. I saw on Aerotech that the motor has been used for a 40 lbs rocket successfully and that usual calculation will not work for this motor. How long is you launch rail? I made sure mien was over 45 ft/s at the end of the rail. I wanted ot be extra careful that my 63 lb nike smoke was going to stay vertical.

My biggest fear ourside of landing on a car or person was a land shark.

[Fe Dude]

Why not TTW fins? Seems like a little extra work to cut the tube and add some extra fillets, but a failed L3 due to a popped surface mount fin that would have stayed on if it was TTW would be a bummer.

[cdondanville]

Why not TTW fins? Seems like a little extra work to cut the tube and add some extra fillets, but a failed L3 due to a popped surface mount fin that would have stayed on if it was TTW would be a bummer.

Excellent question. The build is going to utilize a "virtual motor mount". In other words you will be able to swap out the centering rings for different sized motors: 75mm, 98mm and no centering rings for a minimum diameter 6" configuration. The motor tube will slide directly into the centering rings. Set screws will hold the centering rings in place. This also provides better heat dissipation off of the motor as it is not encased in a motor mount tube. The fins will be epoxied in place to the outside of the airframe and then the entire valleys between the fin and airframe will be filled with chopped glass/epoxy to form one large fillet. I have seen this technique on other minimum diameter rockets that took mach 2 flights, so I think it should be for my little flight. With the technique I am talking about (I will post a picture when I find one) I will be more worried about the pointy edges of the 1/8" fin breaking off than popping the whole fin off. And then it will be up to my TAP to say whether it is in flyable condition.

[RocketManDan]

Excellent question. The build is going to utilize a "virtual motor mount". In other words you will be able to swap out the centering rings for different sized motors: 75mm, 98mm and no centering rings for a minimum diameter 6" configuration. The motor tube will slide directly into the centering rings. Set screws will hold the centering rings in place. This also provides better heat dissipation off of the motor as it is not encased in a motor mount tube. The fins will be epoxied in place to the outside of the airframe and then the entire valleys between the fin and airframe will be filled with chopped glass/epoxy to form one large fillet. I have seen this technique on other minimum diameter rockets that took mach 2 flights, so I think it should be for my little flight. With the technique I am talking about (I will post a picture when I find one) I will be more worried about the pointy edges of the 1/8" fin breaking off than popping the whole fin off. And then it will be up to my TAP to say whether it is in flyable condition.

I think it will work fine too. Just have a nice big parachute to set it down nice and soft.

[cdondanville]

I think it will work fine too. Just have a nice big parachute to set it down nice and soft.

Yeah unfortunately, after doing the math and looking at my inventory, I am probably going to have to upgrade my current big chute. Seems like my 60" isn't going to be up to the task.

[dixontj93060]

Seems like my 60" isn't going to be up to the task.

Uh, no (WAY).

[Eat, sleep, and Fly]

Looking forward to this build... No WAY a 60 inch will work

[chadrog]

This is closer to what you'll need. A decent price, too.

http://www.ebay.com/itm/New-Top-Flig...#ht_500wt_1287

[Fe Dude]

Sounds solid with the fins.... and hey if you aren't using that 60" chute send er my way, I could use one for my new toy

[cdondanville]

Looking forward to this build... No WAY a 60 inch will work

I know, I know already! Big chutes are expensive though! Course nothing comes close to to the motor budget for this. Level 3 isn't open the wallet, it is back the truck up to the bank.

[cdondanville]

This is closer to what you'll need. A decent price, too.

http://www.ebay.com/itm/New-Top-Flig...#ht_500wt_1287

That is exactly what I was looking at. Love me some Top Flight.

[cdondanville]

So I have the fins done. I made them myself using US composites thin epoxy and 6oz eglass fabric. The general Procedure was this.

1. Tape waxpaper sheets to 2 pieces of glass. Mine are about 18x24".
2. Cut sheets of glass to be the desired size for your fiberglass sheet.
3. Mix a quantity of epoxy (usually about the same amount by weight as your fabric.)
4. Spread epoxy on the wax paper.
5. Lay down a sheet of glass cloth and press it tight with goved hands, smoothing out air bubbles.
6. Spread epoxy on the top of the cloth to ensure a good wet out.
7. Repeat above 2 steps 11 more times to get 12 thicknesses of cloth.
8. Plact the second sheet of glass on top so that your layers are sandwiched between the glass, on the wax paper.
9. Put a sheet of plywood on the top of the glass about the same size as the glass so you get uniform pressure on the glass.
10. Pile weight on the plywood. I use about 50lbs of logging chain.
11. Let cure for 24-48 hours.
12. Peel, unwrap, unstick, etc. and sand lightly then you can cut to shape and size

The first sheet I did, I didn't have quite enough epoxy on it so as it settled the top layer had some of the fabric texture peeking through. I did 2 sheets this way to get 4 fins and some extra for bulkheads and the electronics sled. The wax paper is probably not necessary as the epoxy comes right off the glass, but this is the way I do it.

Not sure how I am going to seal the edges where it is kind of furry from the cuts, not pad, just looks a little porous.

[cdondanville]

I got a new tool yesterday that I had been wanting. An adjustable Hole/Circle saw. Really it is a hole saw, but if you flip the bit over it will cut circles as well. This is it in circle configuration. You can tell that because the beveled edge is towards the outside so that you have your straight edge on the "circle" in the middle that you are cutting out, and that the "hole" that you leave in the board will have a beveled edge.



I put this on the drill press and set it up to cut a 6" diameter circle, which is the ID of my airframe. I cut about 1/2 way through the 1/2 plywood. Then I shrunk the size of the circle about 3/32 (.09") and cut a shoulder about 3/16 down into the circle I was cutting. Then I set the diameter back to 6" flipped the board over, lined up with the guide hole, and finished cutting out the circle. A little sanding on the shoulders and viola, a self sealing bulkhead for the electronics bay.



I cut out a couple extra 6" circles without the shoulder that I will go back and cut 4" holes in the center of to use for centering rings/motor mounts. the 2 with the shoulder I then drilled out the center to 3/8" to accomodate the threaded rod that will run the length of the electronics bay. I also attached terminal blocks and charge cups to each bulkhead with epoxy and small brass screws. These will be held on with forged eye nuts that you can see in the picture.

[hammer]

...

[cdondanville]

I am constructing a scratch electronics bay from fiberglass that will use the bulkheads I showed earlier. It will be a 6" coupler about 20" in length. I am shooting for 9" (1.5 cal) overlap on each end with the airframe and a 2" switch ring that will hold the rotary on/off switches. While I have not constructed the fiberglass coupler, I have a section of phenolic coupler that I am using to craft the other pieces.

For the sled I am using a section of the flat fiberglass that I made for fins and bulkhead stock. The piece I am using is slightly smaller that the ID of the coupler.

To mount this I am using some wooden strips with a channel cut in them. These wooden pieces will mount to the inside wall of the electronics bay and allow the sled to slide in and out of the bay. On the bottom of the sled I mounted some wood at either end with the 3/8 hole to accept the threaded rod that will act as the load bearing member through the bay.

[cdondanville]

Then I took the sled and mounted the electronics. I have chosen to go with dual PerfectFlite Stratologger SL100. I chose them because they are generally affordable, reliable and I have lots of experience with them.

The 2 will be set with the following parameters:

System A: Apogee deploy, Main at 1300'
System B: Apogee + 1 second deploy, Main at 900'

I have mounted both system to the board using threaded standoffs tapped into the fiberglass and fixed with epoxy on the back. The altimeters are on the front of the board and the batteries on the back. Currently the batteries are mounted with zip ties through holes in the sled, but I am going to add some additional support at the fore and aft ends of the battery fixed to the sled to offer additional support to prevent shearing of the zip ties under heavy acceleration/deceleration. I am utilizing terminal blocks on the fore and aft of the sled and on the inside of the bulkhead to allow modular construction of the electronics bay so that it can be totally disassembled or parts replaced as necessary. Also because I store my rockets in the garage and don't like to keep the electronics in them out there, I bring them in the house.

For the wiring I am using 22g stranded connection wire. Color coded red for the drogue charges and green for the main charges. All the primary circuitry is on the left side and the secondary circuitry is on the right hand side. (Drogue aft towards booster and Main fore towards payload. for the switch circuits I am utilizing a molex PC power connextion to keep them modular. The male is on the board mounted to the altimeters and the female will be soldered to the rotary 110/220 switches that are permanently mounted into the switch ring. I will zip tie the molex connectors together to make sure that they don't come apart under load. the connections between the sled and bulkheads will utilize a labeled harness that is also color coded.

[cdondanville]

For the air frame I decided on a 6" ID fiberglass construction. To do this I enlisted the help of Walt Stafford and we rolled the tube ourselves. We got a 5' length of 6" OD 1/8" wall 6063-T52 architectural aluminum from onlinemetals.com to use as our mandrel. I chose 7 1/2 e glass fiberglass cloth from US composites. Also from US Composites I am using their thin-slow epoxy as the resin and hardener.

We cut 3 lengths of 47" (which actually acted as our width) off the 51" roll. Wrapping that sideways on the mandrel that gave us 8 wraps. With a thickness of 0.0107" that should put us at our 0.08" target for the wall thickness.

The mandrel was mounted on an axle with wooden centering rings and the axle sits on top of some tripods to put it at about chest high. The mandrel was covered with one wrap of mylar (polyester film) so that there was no adhesion to the mandrel by the epoxy and make sure we had a really slick surface to slide the tube off of the mandrel.



Starting by coating the mylar with epoxy, you then stick the cloth to the mandrel being careful to get a nice straight starting edge down the length of the mandrel parallel to the axle. The you just slowly turn the mandrel brushing on the epoxy as needed to make sure that you get full penetration and work all the air bubbles out with the brush or your gloved fingers. When you reach the end of one piece, you add the next lining up the edges of the 2 pieces. Rinse and repeat until you have all 8 wraps on. We then added a final wrap of dacron cloth (peel ply) that will be removed later, but will make sure that we get a nice smooth finish on the outside of the tube, and reduce necessary sanding later.

[cdondanville]

While the US composites epoxy cures at room temperature, it will cure a little faster with some additional heat. Also it ain't exactly "room temperature" in Walt's shop in February. (it was around 60 in there that day) So to do this we stuck the air frame in Walt's curing box. That box is made of foil backed Styrofoam and has light bulbs on dimmer switches for the heat source. The ingenious piece, and one that makes the quality of these tubes really shine is the rotisserie assembly. The axle in the mandrel has a drive shaft on it that snaps into a barbecue rotisserie. This allows us to continuously and evenly rotate the curing tube in the curing box. This prevents any pooling of the epoxy or sagging due to nasty old gravity.



For the coupler things are a little trickier. Luckily you can buy a 6" OD tube that serves as a mandrel for a 6" ID mainframe. Problem is you need a 5.92" tube to use as a mandrel for a coupler with a 0.08" wall and a 6" OD. Well you can't buy a 5.92" OD pipe or tube. So we had to make our own mandrel. We did this by fabricating a fiberglass tube INSIDE a section of 6" phenolic coupler. This was not really fun. Basically you use the same procedure as wrapping the outside of a mandrel, but you do it on the inside. Mylar goes inside the tube and you roll up the cloth on a broomstick or dowel and lay it inside the coupler and slowly paint and roll, like you would on the outside of a mandrel, only a lot messier. Once it was done we just put some heat on it and rolled it around a table top since the axle and rotisserie was busy.



This coming weekend we are going to fab the other airframe section and hopefully lay up the coupler on our shiny new mandrel.

[Feckless Counsel]

Chris,

You are a brother and my respect to your work in composites.

May I offer you the squeegee? I've found it to be the most useful tool in my limited composite work. Bubbles, excess resin and wrinkles fair no chance against that simple tool. Use it, succeed and be laurelled.

Feckless Counsel

[cdondanville]

Chris,

You are a brother and my respect to your work in composites.

May I offer you the squeegee? I've found it to be the most useful tool in my limited composite work. Bubbles, excess resin and wrinkles fair no chance against that simple tool. Use it, succeed and be laurelled.

Feckless Counsel

We actually used a squeegee today when laying up the payload section. It worked like a champ on some little diagonal ridges running under the pull ply Dacron. I think it was a little excess epoxy that was pooling into ridges. Apparently I have a fear of being too dry and overcompensate. Squeegee took them right out.

[cdondanville]

OK have a bunch to catch up on here. First a shot of us making the coupler on the previously fashioned mandrel.



Here is a shot of peeling the dacron off of one of the big tubes. Leaves the skin nice and smooth, requires very little sanding. Well it would be a little if there weren't 7 feet of it to sand.

[cdondanville]

So now onto the booster. I took a piece of foam board and made a fin jig to tack the fins on square with. Then tacked on the fins one at a time with 5 min epoxy. Once they were all on I LIBERALLY filleted the fins using the diameter of the tube for the sweep of the fillets. (I used the circle I cut out of the center of the fin jig for the scraper to form the fillets.) West 604 colloidial sillica for the filler in the fillets mixture. I make it to a mayonnaise consistency.