Rocketry Warehouse Formula 98 Build Thread

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gdjsky01

gdjsky01

Kim's Rocketeer
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To be started... right here... soon. ;) It came down to starting the Sub-Lime first or the Formula 98. I went with the Formula since I can gain some experience working on an all FWFG rocket. Then the Broken Arrow or Sub-Lime. Good grief though the Sub-Lime is friggin' cool :cool:. I adore that we now have a gorgeous 5.5 to 4 transition available. I hope they sell it separately as well, the design possibilities it opens up a many. Think of a nice 54mm powered X-Ray like clone... :) But enough blathering about the Broken Arrow and Sub-Lime. We'll get to those in due course.

I'll be designing this for Dual Deploy but with the Altimeter in the nose cone, venting behind the nose cone (the shoulder is plenty long). I'll build it mostly for use with a tether or cable cutter. Motor eject at apogee and a cutter at 500-600'. Even so, since they provided a nice switch band and bulkheads for an altimeter bay, I'll build it with the bay as well. Options are always good.

No Mach... nothing like that. I envision lobs to a few 1000 feet (600m) with a baby J, or 3500 to 5000' (1 to 1,6km) on a good sized or full size J, and an occasional baby K like a 1280-K360WH to 6k (1,9km) . Basically full I's to baby Ks. I am not a speed to altitude junkie. No tracker (yet). So keep it close.

Maybe an occasion kick the pants from a 1092-J1520Vmax :D
 
The Formula 98's (well, at least mine) came standard with dual deploy av-bay so no need for nosecone alt and cable cutter.

IMG_0855.jpg
 
Mine too. And I will build it in a way I can still use it someday. I am going to use PEM nuts like a previous build here on TRF (or just epoxy some nuts) to screw the upper and lower sections to the avbay/coupler without bulk plates. Essential making it a screwed together rocket.

I simply won't put any bulkheads on it making it one straight through tube. If I decide to go traditional DD I can by simply creating a sled, drilling two traditional all-thread holes in each supplied bulk plate, and installing them. Leave off the lower set of coupling screws and poof... traditional DD. Or am I missing something (highly possible)?

Now you got me thinking again. Maybe I should just go with the traditional DD setup... ;) :confused2::sigh:
 
daveyfire said:
Try it, you'll like it!
Click to expand...

I agree. I believe a drogue and main dual deploy is actually more reliable than a tether set up (although I will use the later when I'm pressed--mostly scale designs that don't allow for the added space).
 
A great flying Rocket. Mine on a K940WT to 6379'. My vote? go with the standard DD set up, good luck with the build.


Formula98K940WT.jpg
 
Probably seems like I disappeared.... A new job (well new in the last 6 months and my first major deliverable) will do that. :wink:
But I have been building and taking some pictures. Just need to get caught up.

I embedded threaded rod in the nose cone (NC) after much sanding in thin inside tip with 60 grit. In went the 1/4-20 allthread rod into the epoxy. But also, in went a scrap 54mm bulkhead from the grab bag I got from Rocketry Warehouse when I bought the Formula 98. So I had side sanding grooves, and this bulkhead and it's bond to the inside of the NC hold the rod... but no... no enough. When that cured I took a 2.2 inch wooden bulkhead and put it down over the all-thread, sliding it all the way forward into the NC, and flooded it with epoxy. So now we have two bulkheads holding against the NC side walls. Will that work? Beats me... but I can pull on it pretty hard! As far as I can tell, it ain't coming out. Pics soon.

Also installed the PEM nuts on the Nose Cone 'coupler'. The one that provides the NC 'shoulder'. I then wicked in CA to each nut. And then covered then over with epoxy clay!

The fins, MMT, and CR's are all installed with epoxy on the edges of the fins holding it all together for now. I have small semi-circle openings in the TTW fin slots on the body tube to allow for the epoxy injection. Which seems to be all the rage these days.

Again I'll try and get images up soon.... sorry I know it's not up to my usual build thread standards. But again 'The Job' is taking a bit more time than 'The Old Job'. :wink:

 
First thing I did is wash everything. Boom done.

Then I tackled the nosecone / altimeter bay. Obviously I needed a to hold things together.

  • I roughed up and washed off the inside tip of the nose cone. I used some 80 grit wrapped around a dowel.
  • I went pawing through the grab box I got from RW and saw a small bulkplate.
  • I roughed that up as well.
  • I washed some trimmed-to-length, 1/4-20 all-thread with soap and water, and rinsed.
  • I placed the rod through the bulkhead, both into the nose cone, pushing the bulkhead down as far as it would got with some scrap 29mm MMT slipped over the rod to help me push the plate into position.
  • I prepped a full size bulk plate to serve as a centering jig for the rod.
  • Mixed up some System III and poured it in. BTW I first poured in water to find out how much epoxy I would need to filled the area behind the all thread and cover the small bulkplate.

So the picture below shows up to the end of that step.

I placed the nose cone level upright in a bucket of water incase the epoxy started getting warm and let it cure.

2012-12-31-Formula-98-0012.jpg
 
Next day it was cured and I gave some good tugs on it. It seemed like it was not going anywhere!

But I thought, if one is better, two might be twice as good?

So I found me some light ply and cut another somewhat larger disc and repeated the process from the day before.


And so we have this ( you can see all the coarse scratches from the 80 grit ):

2012-12-31-Formula-98-0002.jpg
 
Next up I tackled the nose cone shoulder.

Printed out a 4 position fin wrapper based on the OD of the coupler and taped it on to the nose cone end. Looking at the picture you'll see the full wrap. I decided it was a bit tall and cut it's width in half. Then took a pencil in marked 4 positions.

I placed the coupler into the NC to the point it would go no further.

2012-12-31-Formula-98-0001.jpg

This should give you an idea of where I went.

2012-12-31-Formula-98-0013.jpg
 
Well I ordered the wrong ones. I ordered Mcmaster Carr PN 95185A125 - which are for SHEET METAL. Grrr... I like to make lemons from lemonade so used them anyway.

Here's what I did. YMMV so be careful.

Scribe a mark on the NC and the coupler. Do a good job as this will be your guide for the life of the rocket should you need to remove the shoulder.

I drilled the four holes from the outside of the nose cone to the inside. I made these first holes with a 1/8th inch bit. That's enough room to get 4-40 shanks through. Heres a test fit and the scribe mark

2013-01-06-Formula-98-0005.jpg
 
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So now I removed the coupler / shoulder to get on with installing the nuts.

Roughed up the areas around the coupler/shoulder holes on the inside where the PEM nuts would touch and I roughed up the tops of the PEM nutes.

I removed the coupler / shoulder and widened the shoulder holes to 5/32nds. Because of sloppy tolerances I just kept running the drill and opening the holes in the shoulder until I could press the PEM nuts in with vice grips. BEFORE I pressed them home I dribbled some thin CA with a toothpick on the hole and area where the PEM nut would sit. Then squeezed them home.

I put Vaseline on four 4-40 screws and tightened them into the PEM nuts.

So that gets us to about this.

2013-01-08-Formula-98-0001.jpg
 
Next we mixed up a blob of Aves epoxy clay and pressed four blobs home over the PEM nuts and shanks of the screws sticking inward.
The hope here is now our PEM nuts will not be pushed loose when inserting or removing screws. Time will tell as this is all new territory to me.
2013-01-08-Formula-98-0003.jpg
 
Pretty stock stuff here

One thing I learned

I would not put the retainer on until last. In my jubilance to use a retainer instead of my tried and true home built Kaplow Klips, I went ahead and JB Welded it on. Now of course the aft centering ring has to go in as soon as the MMT.

This is an anti-pattern for those of us who prefer placed the aft centering ring in to align the forward centering ring while glueing the forward ring, but then prefer to remove the aft ring, tack fins on, and pour internal fillets through the aft end. This pretty much forced me (well, maybe not 'forced' but guided me), to try the "fillet injection method".

You can see the wood blocks for the rail buttons.
2013-01-04-Formula-98-0001.jpg

 
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When putting together the rings, MMT, and fins, mark lines down all them that line up and can be seen from inside and out. This will certainly help you get the rail button mounts and such lined up. Also don't forget to test fit all the parts. The CRs were too tight. That's good as you can custom fit them.

I slid on the aft CR (because of putting the retainer on too early) and then tacked the forward ring with thick CA. Then pushed the whole home until the forward ring just cleared the slots. Then I played and fiddled awhile while I rotated the whole assembly and the aft ring such that my marks were lined up and I could see the fin lines I had drawn on the MMT through the fin slots. Like I said, IMO, this is all easier if you can leave off the aft ring... each to their own.

Then I placed a bead of glue on each fin and pressed them home with the aft CR pushed tight to them.

2012-12-26-Formula-98-0001.jpg

2013-01-06-Formula-98-0001.jpg

2013-01-06-Formula-98-0002.jpg
 

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Right then... that is where we stand today. Ready for fillet injection.
I did pour epoxy on to the forward surface of the forward CR so it's sealed when I fillet.
Probably do the same for the aft.
Because of my goof up with the retainer, I can only hope the fin roots are fully sealed.
:blush:
Live and learn.
 
Sorry about the lack of detailed pictures. Not quite up to me usual build thread standards. I'll try and do better on the Sublime and Broken Arrow. :confused2::blush:

Thing is I am sorta feeling my way through this. I for all I know, the nose cone thing will flop. If the bond lets go, the nose cone alone will fall. Everything else should stay together.

Here's a picture looking down the lower section at the forward CR.
2013-01-12-Formula-98-0002.jpg
 
Here is the general nose cone setup. Still have to drill the holes for the wires from behind the bulkhead and seal them.
The plan is, at the pad, lift off the NC, switch on, put the NC back on, and if I feel the need, insert shear pins. Not yet used shear pins. Nope. Not ever. Always have adjusted the fit via masking tape using the old rule:

If you can pick the rocket up by the nose cone, thats good. If you can then shake it once and it starts to separate, thats perfect.


But I have 2-56 nylon screws... should I feel the need.

The eye nut will be secured with another 1/4-20 nut.

2013-01-12-Formula-98-0003.jpg
2013-01-12-Formula-98-0004.jpg
 
Couldn't help myself :wink: The white band is the paper guide for drilling the screw holes in the couple and body tube, just like the nose cone shoulder.

2013-01-12-Formula-98-0001.jpg
 
Looking good, I really like the NC setup. What type of epoxy will you use for the fin filets?
 
I can see your arming method posing an issue. If there isn't a perfect seal, the charges will pop.

I had this happen many years ago with my 4" scratch built Patriot. I wanted to pull the rocket from the pad, and I was using the "twist and tuck" method. I absent mindedly pulled the payload section up, and as I did so the charge fired. It was <1g so it wasn't overly dangerous, but scared me enough to teach me a lesson.
 
If I am understanding your issue, it's that as I push IN the nose cone, it might cause a pressure surge in the nose cone as the air in the body tube has to go somewhere. I always drill holes in the body tube section to prevent pressure separation. As the nose is installed, air exits the tube, and does not build pressure. Also, though not shown, the plate is two plates. One that fits IN the coupler, the other that is the diameter of the INSIDE of the body tube. And I have to pry it off with a flat blade. It fits tight. The wire holes will be sealed. However I see and understand your point.
 


I am going to do an experiment with the stratologger and the RR2 and see if pulling the nose can fire it. If it's truly sealed there should be no issue... however I want to know. So I'll throw it together, plug the MMT, add a chute, and give it a whirl with 12v lamps as charges.

I am reconsidering Dan's concern and find tho I can program the stratologger with a 60 second sensing delay, that only helps ARM the altimeter. There is no way to DISARM without pulling the nose cone. And THAT could be a dangerous thing (hence my experiment above). So I am pulling the switch and will plug the hole with epoxy clay.

So how will I arm it? Twist and a tape. Not tuck, tape. Twist, tuck most of the way in, and tape to the side of the NC. Black wire with black tape. No one but me will notice.
Also I am adding small vinyl warning labels. Don't pull while armed.

I may just build the traditional ebay after all.

Like I said... a learning experience.
Thanks Dan for making me think!

 

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