Son-of-a-monster

[kramer714]

Build thread on the Son of a Monster, one of 2 projects for LDRS. it is a scratch built rocket,

The specs;
137 inches long
6.35 inch diameter
Hypertek M1010 motor
All graphite / epoxy construction
Fiberglass transmitter bay in the nosecone
fly away weight, 45 lbs
Sims to Mach 1.02 (not gonna happen, mach .95 is about Al I would expect
over 15,000 apogee, 30 seconds to apogee (how cool is that!)
Mountain Avoidance System (still working out the bugs on that one)

The motor mount / fin cans are a separate module that slides into the body tube. I will rivet it in place. The aft bulkhead is turned aluminum.

I don't have too many pictures of me making the tubes,

The tubes were made on a 6" diameter concrete form that was prepped as follows;
1) painted tube with Kilz primer,
2) sanded 'fuzz' off of tube
3) reprimed with Kilz
4) lightly sanded tube
5) three coats of Partall #2
6) buff out with a terry cloth

For the Layup,
I used a Bis-A epoxy and an Amine Cure, gives me a LOOONNNNNGGGG working time, but needs an elevated temperature cure. Low viscosity, around 300 cps at room temp. Good Stuff! The layup went as follows;

A) paint resin on the surface of the tube
B) wrap 2 plys (one piece of cloth jelly rolled on) of 10 oz graphite cloth
c) Tootsie roll 1 ply of graphite braid (it works out to be 22 oz at this angel +/-30 degrees)
D) Wrap with nylon tape (not shrink tape)
E) Hang from one end for 48 hours
F) Cure at 180 F for 2 hours, followed by 2 hours at 250
G) Cut off the ends
F) One tube actually slipped off of the form, the other had to be peeled, didnt stick (came off clean) but mechanically locked

More details to come

 

[kramer714]

attached rocksim file for it...

The pictures show 2 of the three body tubes, i have the tip of the cone in process but not the tube

View attachment newmonster.rkt

 

[dixontj93060]

Most excellent!

 

[OverLord]

Wow I am really excited about this one! Looking really good! But we want more! Feed our eyes!

Mike

 

[kramer714]

The fincan is bonded up. The motor tube is card board with .040 fiberglass on it.

The three rings are a sandwich of .020 of fiberglass over 30 lb foam. I made these as a sheet and then cut them into rings on a lathe. A lot lighter than plywood with a nice wide (1/2 inch) flange.

The bottom is the aluminum lathe turned closeout, the aluminum piece has a female recess in it to accept the motor tube. The joint is bonded plus there are 3 wraps of boat tape around the joint.

The fins are solid .210 thick graphite epoxy

I bonded the fins using the body tube by sliding the motor tube (with the three rings and aluminum closeout already bonded) into the body tube. The body tube was slotted on a mill. Carefully (remember the game operation?) I put a bead of thick CA on the motor tube, I put CA kicker on the edge of the fin and dropped it in place. It locked in place in a second or two. I did theis for all three fins. after the CA was hard I slid the motor tube with the fins bonded in place out of the body tube and finish boded the fins.

Finish bonding was done by putting a piece of tape tangent from ring to ring, this was a guide to show me how far the build up could go. I laid up 4 plys of 7781 glass 2" wide into the corner, one inch on the fin and one inch on the motor tube. I finished it up by adding one ply that bridged from one fin to the next. I didn't use laminating resin but a tough adhesive (that is the green tint the adhesive) with a high peel strength. In hindsight I would have used boat tape not the strips of glass. I did one 'valley a day' after the last one I oven cured the part to 160F for a few hours.

Total weight as shown 2100 grams.

It looks ugly, i primed and sanded the fins before bonding, looks ugly feels smooth

 

[degreaser]

I did one 'valley a day' after the last one I oven cured the part to 160F for a few hours.

Very nice! What sort of oven did you use to cure the epoxy?

 

[kramer714]

I cheat a bit, i have composite curing ovens at work..

I have helped people with home built programs, if you are creative here are some of the curing ovens I have used / helped people used,

1) Black Car - sunny day - parking lot

2) black plastic box in the sun

3) box made from sheeting stryrofoam (or plywood with foam on the outside), heated with a duct heater and a fan or finned strip heaters and a fan.

4) box made from steel studs and THIN galvanized steel (really cheap way to go), heated with a propane heater with LOTS of air space between the heater and part.

5) BBQ

You can buy simple controllers and heaters. Finned strip heaters or rod heaters are actually pretty cheep, a simple controller can also be rigged up. For a few parts, you can use old school digital (use your digits flip the switch on and off), with a finned heater, simple fan, and a thermocouple or thermometer.

I can give you more details on the size you need and I can help you figure out a cheap curing oven.

 

[redsox15]

do you cure fiberglass the same way or can you just let that dry where you apply it? I ask because on my next project I will be using fiberglass for the first time and am wondering if there is a special way that it needs to dry if any.

PS. the rocket is looking great!

thanks in advance

Matt

 

[dixontj93060]

Curing requirements are dependent on the epoxy used, not the laminate material.

do you cure fiberglass the same way or can you just let that dry where you apply it? I ask because on my next project I will be using fiberglass for the first time and am wondering if there is a special way that it needs to dry if any.

PS. the rocket is looking great!

thanks in advance

Matt

 

[kramer714]

You don't need to use heat to cure ALL epoxy resins just some of them...

A little background on epoxy, one misconception is that if it is hard it is cured, this isn't always the case.

Room Temperature curing epoxy such as West System will harden (vitrify is the technical term where they turn into a glassy solid, hard but not cured), and given some time will cure. Temperature will speed things up, and to some degree increase the mechanical properties and temperature resistance. Even with the room temperature resins, I always like them to see some elevated temperature before de-molding or use. With resin chemistry like West System I would post cure at 120-130F for 4 hours to get the best properties.

Elevated Temp resins may or may not vitrify at room temperature. For example the resin I used for this rocket gets hard overnight but if you were to test it, it would soften from solvents like acetone or alcohol and has a very low toughness. The cure for this resin was 180 for 2 hours followed by 250 for 2 hours. After the cure the resin was VERY tough and strong. Properties that would be difficult to achieve with room temperature resins.

The way to think of it is spaghetti... when you mix the curing agent and resin together, two things happen, the first thing is the chains of polymer get longer, by joining ends of other molecules as the spaghetti gets longer it becomes harder for it to find another free end to join onto. It also becomes harder for it to wiggle, if the chains are long enough they become almost immobile, this is the glassy state of vitrification. Looks hard, but has poor strength, low temperature capabilities, and poor solvent resistance. If I pull on the chains they can slip over each other, heat them up and they wiggle more.

The second step is crosslinking, in this step of the reaction branches from the middle of the chain for and connect to other chains. Now if I pull on one chain it is 'anchored' to many other chains. Even if it put some heat in, I can't give one chain the energy to wiggle free.

Here is where heat during the cure can help, in the first step by heating the resin the chains can wiggle more and have a better chance of finding a free end. In the second step the energy aids in crosslinking.

This is a simple take on it but I hope it helps you understand what is going on.

Having said all this, for home built rocket parts, room temp epoxy should meet your needs, a post cure to 120F certainly helps things more fully cure.

 

[redsox15]

And a post cure meaning after it initially dries...correct?


Matt

 

[kramer714]

yup,

Let it stay at room temp for a day and then heat it.

 

[Handeman]

What about letting it sit for a week or two? Will time do the same thing as the post cure?

 

[kramer714]

Time isn't quite the same as temperature, the higher temperature give the reactive ends a bit more energy to find something to grab onto.

 

[kramer714]

I have the avionics bay almost complete, all that remains to be done is to bond the aluminum flanges in place (shown loose in the pictures), build up a wire harness, add switches, and rivet in place nut plates for mounting in the rocket.

The AV bay is all composite (and some aluminum) including fiberglass tube .1 thick S-Glass / Epoxy, graphite epoxy bulkheads .125 thick 350 degree cure TOUGH resin, and VH PE for the blast shield.

I wanted to work on making a 'clean end' of the Av bay. to clean things up I did a few unique (well for me at least) things including,

1) Charge holders, machined aluminum charge holders bolted to the end bulkheads

2) 4F holders, bonded PVC 'capsules' with the igniter bonded in place

3) Recessed bulkhead with a plenum for the charges and a blast shield to prevent the chute from being in contact with the charges and to protect the end of the shock cord,

4) Machined shackle mount, this keeps the shackle heading the right direction and allows the use of an anchor shackle.

5) Shackle cup, the shackle sits recessed in a cup totally protecting it from the charges.

 

[kramer714]

some more pictures,

The aluminum ring will be bonded in place in the av bay tube. The aluminum (it is hard to see in the picture) in machined like a flange wit ha smooth bore on the inside. This lets me use an o ring or flange gasket to get a good seal from the bulk head to the tube.

The view of the plenum shows what is going on between the blast plate (plate with 6 smaller holes in it and the bulkhead.

 

[dixontj93060]

Very nice av-bay.

Where did you get the the material for the bulkheads?

... graphite epoxy bulkheads .125 thick 350 degree cure TOUGH resin

 

[kramer714]

Scrap pieces from work. This was a 'failed' panel from some developmental part at work (aerospace composites company). The part failed because of some trapped air on one of the surfaces, more of a cosmetic problem than structural.

 

[kramer714]

Progress so far, 3 body tubes are compete (upper one needs sanding) plus the entire tube needs clear coat. Much easier to paint than to clear coat over graphite..

The fins are primed white, i plan to paint them safety orange to make it easier to see. The altimeter bay stripe will also be painted safety orange or possible covered with a THIN stainless strip as a reflector.

The fin case is attached with screws, the bottom screws are tapped with (6) 10-24 screws. The picture shows the clecos I used to match drill the body tube and fin can. The upper flange of the fin can is attached to the rocket with (6) 10-32 floating nut plates. The connector is also screed in place (6) 10-32 screws, I do need to verify the bearing strength of the screws, based on a 40 lb rocket I'm designing all of the recovery gear to 2,000 lbs. 6, #10 screws can handle that in shear but I need to verify the bearing strength of the graphite. The laminate is .080 thick with 1/2 of it at 0/90 and 1/2 at +/-30 degrees (0 degrees is along the axis), great laminate for buckling, poor for bearing. If it comes up short I will add a second row of screws 30 degrees 'clocked' from the first.

I did buy a RoamEO dog tracker and will be incorporating it into the nose cone. The Nosecone will add an additional 20 inches to the length.

 

[cjl]

Very nice. I look forward to seeing this at LDRS. Do you have approval for the flight yet?