Satellite Interceptor Build 2

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Jan 19, 2009
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I wanted to bring something new to LDRS this spring, so I dug out my K&S Satellite Interceptor.

This is the 2.63" diameter, 38mm kit he sold

Before I started, I built the Estes version. I was hoping this build would go better than the problems I had there...
Unfortunately, that is not meant to be :sigh:

To begin, the parts shot


One thing I noticed was the cone was wrong. The SI needs a conical cone, not an ogive. So I ordered a replacement cone (plus an Aero pack retainer)

cone diff.jpg

The main tube comes pre-marked for slotting to support the TTW fins.

I started cutting with my trusty exacto knife and decided to dry fit the parts. The look seemed wrong. That's when I started checking and found the 1296 was different from the 3027 version.
I built the 3027 version. K&S modeled the 1296. Scaling the dimensions showed the wing fins were too far back.
Question - since I already slotted the tube do I live with it? But..Next problem? One of the centering rings, which lines up with a cutout in one of the tail fins, interferes with wing.


Guess I'll extend the slot. At least the wing will cover the opening, although I may try to patch it
My next disaster?

First I had to repair my shopsmith, then I was using it to sand the leading edges. The one tail fin has its TTW tab in the way. I sort of slipped and sanded a gouge into the leading edge. :y:

To repair, I took a sheet of card stock and folded it in half. I glued one side to the fin near the edge. I placed a dollop of rocket poxy where the gouge was and compressed the card stock with clamps against some metal rulers and let it dry.

damage.jpg repair1.jpg
Removed the clamps, did some sanding, a little Elmer's F&F, a swipe of CA and voila


Once primed and painted my boo-boo shouldn't even be visible
Before I start actual assembly, I need to figure out how to secure the recovery harness

A concern I have is the kit is 2.6" diameter with a 38mm motor tube. Doing the conversions, and there is less than 1/2" of CR for a bolt and quick link.

I set the supplied screw eye in the tubes to see what it looked like...


As you can see, there will be no way to install a quick link and allow a long motor to extend beyond the motor tube.

The kit also came with a length of Kevlar


My options:
1 - Don't worry about an interference. The motor tube is 14" long so I should be able to fly up to a 5G CTI case. However, I don't have a 5G case - I have a 3G and 6G with spacers. So either new hardware or I would be limited to 3G motors,
2 - Find a smaller bolt and quick link. Just concerned with reduction in strength (and still fitting)
3 - Use the bolt and skip the quick link. Just tie the Kevlar cord to the bolt. I can leave enough loop so the knot is far enough above the bolt to not interfere with a 6G case.
4 - Skip the bolt and just epoxy the cord to the motor tube (sorry Ted - I know you don't approve of this)

Thoughts/Comments? I am leaning towards options 3 or 4 (probably 40% toward 3 and 60% toward 4)
I went with epoxying the strap to the motor tube. The strap was long enough for me to do a "Y" harness.

First one side

mount a.jpg

And then the other

mount b.jpg

For the top center ring, I filed a slight notch and rounded the edge where the strap would feed through

mount c.jpg

Center rings on and filleted. I tried to keep the fillet away from the strap

mount d.jpg

My original thought was to apply tape around the tube below the top ring to provide some holding power while keeping the epoxy off the strap. I then realized this would interfere with the wing tabs so I skipped that. I dry fit the mount into the tube and noticed some of the epoxy would get in the way of the tabs, so I used a dremel to sand away some excess. Once I was satisfied, I used a dowel to get some epoxy into the tube and glued the motor mount in
I needed to figure out the build order. Dry fitting things together I determined there was no way to support installing everything using my Guillotine Fin Jig.
The best approach appeared to be starting from the rear. Note that the rear ring is just sitting in there with some tape to support removal to allow doing internal fillets.

So... Stab 1

stab 1.jpg

Followed by Stab 2

Stab 2.jpg
Tail piece 1

tail 1.jpg

And tail piece 2. Since this piece is forward swept, you can see why the order of the assembly was important

tail 2.jpg

Rear view of the 2 stab and 2 tail pieces

tail 3.jpg

I also took the opportunity (since I had some leftover mixed epoxy) to glue the pieces I removed when I had to extend the wing slots to fill the earlier slot due to the miss-marked tube. You can see how the wing itself will cover this piece. I more installed it so the epoxy on the wing would not just drip down.

slot 2.jpg slot 3.jpg
Due to the long length of the wings, my Guillotine Jig won't work.

I made up some guides on foam board


Then with the guides, rubber bands, tape, etc I installed the first wing

wing 1.jpg wing 2.jpg

And then the second wing

wing 3.jpg
Last bit that glues onto the body is the strake. And a new jig to align this.
Used 2 sections of aluminum angle and clamps.

This piece I just used wood glue.

All of the main pieces are now glued on. Need to do some cleanup and fillets.

I did get the replacement cone - looks a lot more Satellite Interceptorish, right?

cone new.jpg

I decided to dry fit the pieces together and found an issue :facepalm:

The rocket looked too tall. Time to do some more measurements......

tall a.jpg tall b.jpg

Scaling up from the 3027 version, the total body tube should be 45" (and this includes the straight portion on the NC that the replacement cone does not have). But the tubes total 52" - an extra 7" in length.

My first thought was "Off with her head" - err - extra body length.

But then I did some thinking. The upper tube is 24" long. The coupler/bay and NC shoulder will use between 7~8".
If I remove 7" from the tube I get 24 - 7 - 8 = 9" of space to pack a main chute and shock cord.

Presently the rocket weighs 2.5 pounds. I included the av bay as is (no electronics mounted), the motor retainer, but excluded the chute and cord weight and the motor casing weight. Also no fillets, primer, paint and I did not include the wing pods and dowels.

Optimistically this will only add 0.5 pounds, which for a 20fps descent rate requires a 39" chute.
Probably more realistic is adding a pound, which requires a 42" chute
Conservatively, the final weight could be 4 pounds requiring a 45" chute.

Maybe I could fit a 36" thin mil with cord in the 9" of space - doubt I would fit my 48" standard thickness chute (not sure the 39", 42" or 45" dimensions are standard without getting a custom chute made). Just did a quick check. I see Top Flight does offer both a 45" and 50" thin mil chute....hmm....

Another option would be to forego standard dual deploy and either just fly low or use a Jolly Logic Chute release.

May also compromise - only cut 3~4" off instead of the full 7 - that will give me some more space....

Thoughts? Other suggestions?
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No input on the length issue - going to move forward right now with the full length. Figure I can cut it down later.

One thing I never did was fill the spirals in the tubes, although I have to admit they are very fine and would probably get covered when primed
But hey, who doesn't love sanding???

Also, so when I do my fillet they don't droop, I wanted to give a bit of fill in the fin/tube joints - especially where I had a "square" hole and a pointed fin.
Here comes the Elmer's Fill & Finish!!!

slot fill a.jpg slot fill b.jpg

fill 1.jpg

For the pods I also did a fill of the rather nasty internal spiral

fill 2.jpg
Sanded off the F&F. Besides a mess, very little left on the tubes. It was probably a waste of time and the primer would have taken care of it.

Put some masking on for fillets. I am doing these a bit small for looks. I don't plan to push this bird to hard.

This looks great. FWIW....I think the chute release is the easiest way to go for something like this.
I did the internal fillets when I did the external ones. I really could only do the stabilizers - the others were too recessed.

Finally installed the rear ring. Not really exciting


Looks like I may be doing some overtime at work, so I may not get back to this until the weekend
Are you planning to add a nozzle, for display only or flight, like in the original kit?
It comes with a template and ring to make a display only nozzle.

But I plan to use an Aeropack retainer which may get in the way - I'll need to take a closer look once I get the retainer on
After working a 50+ hour week, I was looking forward to doing a lot of building this weekend, but....

Unfortunately I threw my back out. So on muscle relaxers & pain pills. :(:cry::sad:

But I did try to get at least 1 pod mounted.

Made a template and cut some foam board to make a guide to ensure the pod would be centered. Used Titebond II with a double glue joint

pod guide.jpg pod 1.jpg
Still fighting back pain so going slow...

Did some fillet for the dowel. When that was dry I used some F&F on the dowels and joints.

Arg - can't upload pix - will add later
Sanded down the F&F (will need to get a pix later) and instead of filling gaps I went with making holes.

The kit came with parts to support DD. Still not sure if I will go that way or the Jolly Logic Chute Release, but I'm going to build it to support DD.

I first decided I want 2 shear pins to prevent drag separation. With the pods and dowels there will be a fair amount of drag on the lower portion. I aligned these with the strake and lower rudder. I am using 2-56 nylon screws for the shear pins.

Drilled and tapped the holes for the lower portion


The screws that will secure the AV bay to the top were aligned with the wings and lower rudder. In the picture you can see a 2-56 screw maintaining alignment while I marked and drilled the hole for these mounting screws.

In the past my DD rockets were fiberglass. This is my first cardboard tube rocket with DD. I decided to use the advice from this thread
to add some brass shim plate to cut the shear pins

Did some sanding of the tube to make space for the thickness of the brass shim (I used 0.005" thick brass). The picture is with the plate just sitting on the shear pin and has not been glued in yet.

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Glued in the shim plates. Ended up with a little too much epoxy and needed to sand it down. At the moment the coupler fits, but I will probably do a bit more sanding.

shimb.jpg shimc.jpg
Going to get cold here so I decided to get a quick primer coat on to highlight imperfections that will need cleanup.