Build Thread : Der Big Red Max

[4regt4]

Is that the same as a Big Daddy nose cone?

Hans,

 

[StreuB1]

FWIW, my Der Big Red Max with papered balsa fins and the stock clay nose weight flies amazing on the E26W-4 Q-Jet to around 400'. I have the 24mm D Q-Jets as well but since the E26 flies to 400', I cannot imagine what the D would fly to.

I replaced the chute with a Top Flight thin mill and a nomex chute protector. I also augmented the elastic shock cord with a 4' length of 1/8" kevlar cord. The Kevlar goes to the top CR and then links up to the elastic so that the kevlar is exposed to the ejection charge and the elastic is protected inside the nomex blanket.

Its one of my favorite rockets and flies really well. The papered balsa fins are too fragile for landing, even with a larger thin mill chute. So, I filed the first 1/8" of the fins flat, where they contact the ground. This does away with the sharp corner meeting terra firma upon landing. And then epoxied popsicle sticks flat to the bottom. Once cured, I cut then all off and filed/sanded them flush. This gives you a nice flat spot on the bottom of the fins to land on and its also made of hardwood so it can take the abuse.

I will post a few pics shortly.....

 

[waltr]

The warp on the fins is really bad. I would not be happy with them and pulled them off and make new fins from plywood.

 

[StreuB1]

Also, your fins can be fixed rather easily, even as they are installed. Sand the paper off, get some brown kraft paper for packing at Menards. Cut out paper sections that cover the fins, but are a little larger, maybe an 1/8". Get some tin foil or wax paper and tape it to a flat surface so that it hangs over the edge. Apply a piece of kraft paper to each side of the fin with a THIN epoxy of your choice. Then lay the rocket sideways with its fin on the wax paper and the rocekt hanging off the table. Then place another piece of wax paper on top of that, then a stack of HEAVY books. This will press the fin flat and also press the kraft paper/epoxy into the balsa. Once cured, cut off the overhang of the kraft paper/epoxy, light sand and finish. Its not too late to do this even with the fins glued in place.

 

[StreuB1]

Some pics to explain....

 

[techrat]

Is that the same as a Big Daddy nose cone?

No, the nosecone for DBRM is 3" diameter like the Big Daddy, but it's like 4" longer. I would like to build a Big Daddy with this nosecone.
But that's a project for much later this year.

 

[techrat]

Ok, quickie bulkhead built. Welded eyebolt, washers, coated with CA, and then I used Gorilla Glue quite liberally, because I was too lazy to mix up epoxy. Should hold. And likely to outlast the rest of the rocket.

 

[Back_at_it]

OK, after two very thin coats with laminating epoxy, I performed a quick and light sanding with 150 grit and then 240 to remove the airbubble "bumps" that came from applying the epoxy with a paintbrush (or perhaps the bubbles formed due to acetone), but either way they sanded easily enough. I'll give it a final sanding before painting, and I'll try and use filler primer to fill any low spots in the epoxy. we'll see how it goes.

One of my fins still managed to warp badly, as I said, this balsa is way too thin. I should have bought a thin sheet of balsa, and cut a buttress piece with the grain going 90 degrees from the grain of the fin, and glued that to each side of the fin, but, what's done is done. Interestingly, I've got a slight warp on the next fin over, but going the opposite direction, so, perhaps they will cancel each other out and it'll still fly straight. Who knows?

Next steps: Shock cord/Chute, Motor retainer, and a paint scheme. While I'm tempted to do the traditional red & black, I'm also thinking of the "Mad Max" MFP paint scheme for the police vehicles in the first film, which was Yellow and Blue with a Red & White stripe. Then I could call this "Der Big Mad Max"... Either way, almost done.

That is some serious warp you have there. Depending on the motor you plan to use, I'm not sure I would risk flying like that. You're going to be in for an entertaining flight if the fins hold together but my concern is they would break off entirely which could be dangerous. At the very least, fly this when no one is around.

 

[techrat]

OK,.... here's my solution to the warped fin. I cut a piece of scrap, have the grain running perpendicular to the fins grain, and epoxied that to the fin. Then a pile of heavy books and an old shortwave radio were pressed down on the fin overnight. And I can say that warp has been reduced. I'll have to sand down the scrap to "blend" in with the fin a bit, and then I'll need to laminate again. I may put pieces on the other two fins to balance it out first though. Once covered in the laminating epoxy, it should be MUCH MUCH stronger than it was. It's also going to be heavier (so much for flying this on E motors), but that's no longer a priority as much as making this as durable as I can, while keeping it within the realm of a Mid-Power Rocket.

 

[techrat]

OK, added all the strengthening pieces I'm going to add. The fins are considerably stronger now, and less warped. Ready for one more coat of lamination epoxy, and then a final sand and paint. Almost there.

 

[techrat]

With temps hovering in the low 40's, I decided it was time to paint. Now, I despise "pristine" rockets that look like they've never flown (although I admire the paint job that I can probably never do as well), but I like "battle scarred" rockets that look like they've already suffered more than one CATO. So with that in mind, I went out of my way to make the rocket look distressed, and I present as the finished product "DER RUST MAX", a rusty, discolored, orange/black monstrosity that can only be mine. Guaranteed to come to back in the field, because we know that rocket-eating trees only prefer glossy, brightly colored rockets. Also, never to be confused with anyone else's Der Big Red Max, because mine is hideous.