Another Mega der Red Max

[tsmmiller]

I’ve been building rockets pretty much non stop for the last year. None have flown so far.
The latest addition is a Mega der Red Max.
Nose cone and BT from Estes, the remainder of the parts from Erockets. The vinyl will come from Stickershock.
Contemplating how to build this I’ve already decided to forego the 29mm and go to 38mm, motor tube will be the 38mm phenolic I didn’t use from the AMRAAM.
Harness retention by Kevlar loops at the fwd ring.
Now I have questions about the recover harness, I’ve read lots and lots but can’t seem to come up with what would be right for this bird. I want to use a sleeved TN from OneBadHawk, and think the 9/16” x 20 ft is a bit excessive, but then what do I know. I don’t, so I am throwing that question out right now.
Second concern I have is mounting the fins. I really really want to take my time on this one, and get the fins as straight and true as I can. I love the laser cut light ply, but I don’t see any made for 3 fin 4” body tube. Guillotine fin jig sometime way in the future, but for now this is the way I am leaning.
Is there someplace (or somebody) that can or does make jigs for this size?
If somebody from this wonderful forum is willing too cut those for me, I am more than willing to pay for time, materials and shipping!

 

[Nick Hutton]

Big_red_daddy, AKA Toby, can supply both of the things you are after. He made my whole kit and it flew great.

 

[swatkat]

agreed, BRD has it all.

 

[tsmmiller]

Ok then, It looks like I need to get ahold of BRD (Toby) for fin jig and recovery harness. I have everything else I need on hand, except the 38 mm rings and those are on the way.

 

[SomeRandomBAR]

I am no where ready to build on this yet, just playing around and visualizing.
I laid everything out and looked at how it would piece together, and realized with the 13.75 38 mm motor mount the payload area is about 4 inches.
I've not done anything in open rocket and decided to give it a go, see how it stacks up and if I will need to add weight in the nose (I do).
Since OR is totally new to me I used another members file and edited it for the 38mm mount and rings plus larger parachute.
The stability was just over 1 caliber, so I added weight to the nose cone to move it fwd.
Just because it is the motor I have on hand I wanted to see what it would do with a I366R. CG moved back to less than 1 cal, so more weight to the NC when ready to build.

 

[SomeRandomBAR]

I just realized I am logged into this with a different account name. For the first time is nearly two years I am using my PC vs the I pad.
I'll make sure to log in with the correct profile in the future to make it less confusing.

 

[tsmmiller]

I ordered fin jigs, rings and kevlar from big_red_daddy. The were sitting on the counter when I got home from Pasco yesterday. A second box contained the clothing from StickerShock.
(Thanks to both Stickershock and big_red_daddy)
I’ve not had a chance to open either up yet. Other chores first.
One thing I am eager to see is the difference in circumference between big_red_daddy’s rings and those from e-rockets.
e-rockets just seemed substantially small. I know epoxy is the bond that holds, but these rings “rattled” in the Estes body.

 

[tsmmiller]

I measured the circumference of both sets of rings.
The rings from big_red_daddy we’re 3/16 larger and fit snugly. I am much more comfortable with those rings and will be the ones I use. The former will be set aside for a later project.
While I inspected everything my 5YO asked where his rocket to build is.
I am going to have to work on that. I might even convince MRS to build one.

 

[swatkat]

BRD kit complete. "Jiggly Chuff".

 

[tsmmiller]

swatkat
That looks great! I am going to take a considerable amount of time for this one. Slow and easy.
Paint scheme of course red and black. I am leaning toward a nice bright "candy apple red" with the black fwd section.

 

[Bat-mite]

For a fin alignment guide, go here and enter your exact dimensions. If you don't have the mfg. specs, measure with a caliper. Print out the template actual size (make sure your PDF and printer setting aren't on "shrink to fit" or whatever).

Go to Hobby Lobby and get a 3' X 4' piece of foam board. Glue the printed template onto the board, and cut out with a matte knife.

This is an 8" tube. Whole lot easier with a 4"!

 

[tsmmiller]

Thanks Bat-mite, That is what I used on my AMRAAM, only cut from cardboard. It worked.
Mrs Took 5 YO over to his best friends to play for the day. I stayed home to relax and sleep. I broke my little toe yesterday and have been taking hydrocodone for the pain. So also a little sleep.
I woke up with a quiet house and wondered what to do.
Decided to break out MDRM and get some ideas flowing.
Since I am building this with a 38mm motor mount and I am using Aero-Pack retainer all my measurements are based on the retainer sitting flush against the aft ring.
The trial fit of Toby’s rings against PML’s 38 mm motor tube showed I needed to sand a tiny bit from the rings. PML’s tube is 42mm and the rings were about 41. Just a brief wipe on the ID with 100 grit and a snug fit was gained.
I positioned everything and lined up with the fins, marked locations, sanded with 100grit cleaned with IA and nearly made a mistake.
I positioned the center ring, mixed up 1 gm of 30 minute epoxy and started to place it around the ring. After the first dip I realized my error. Motor mount.....not epoxy...JB Weld. I cleaned off the ring threw the epoxy away and mixed a bit of JB Weld and lay down the first fillet around the center ring.
I decided that being doped up and rocket work is not comparable. Cleaned everything up and went back to lay down.

 

[tsmmiller]

I’ve done the basics on the MDRM, same ol filets around the centering rings. I couldn’t come up with anything to keep the rings straight as I positioned them and was going to just hope for the best.
5YO watched me trial fitting everything under the sun with no luck.
I finally found one of the plywood rings from PML that was sort of suitable. Just as I did that 5YO hands me the center of a tp roll.
What do you know, it works. So I slid in on the motor tube, lined everything up and glued away. Once all fillets were dry I just tore the tp roll away.

 

[tsmmiller]

Sometimes my 5 YO scares me with his thoughts outside the box.

 

[tsmmiller]

The next part was filling spirals on the BT. I’ve always just filled with primer, or left alone. The last couple of builds I filled with Bondo spot putty. I found I really didn’t like the sanding of the excess off.
With the nice glassine surface of the Estes BT I decided to try something different.
I wrapped the tube in double strip of Teflon tape, leaving about .003 to .005 on each side of the spiral.
I filled the gap with spot putty, let dry, sanded it down to top of tape level and since the putty Dow’s shrink a bit, added a second layer of putty and once dry quickly sanded it flush to tape surface again.
I then pulled the tape and was left with a .003 high putty ridge where all the spiral gaps had been.
Now I can’t decide if I want to sand that flush, or wait till I prime and sand with the primer. I am leaning toward waiting.

 

[gldknght]

Maybe an Estes Der Red Max for your 5yo? You'd have to help with the build, (oh, bummer!) but the Estes one and yours would compliment each other.

Also, if you want to get rings on a motor mount perfectly straight, you can wrap a piece of printer paper around the tube, lining up the edge and marking with a pen. A good Sharpie makes a nice heavy mark:

 

[tsmmiller]

DRM for the 5YO . Hadn’t thought of that.
Maybe his next build. Right now we are in the middle of a couple of School Rockets. Some of the more delicate work daddy is doing such as knots in shock cord. Everything else I am letting him do after he watches me do it on mine.
I actually did think of the paper for marking, however what I was aiming for was something rigid the ring could be supported on while the opposite side fillet dried. The tp roll fit the bill.