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PEPP 1 Aeroshell REDUX

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JAL3

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I found a way I can resurrect my old PEPP thread: Here it goes=>

I spent too much time looking through my ROTW supplements and finally could not put it off any longer. I wanted to try and build a flying model of the Planetary Entry Parachute Program Aeroshell. Actually, I want to build both versions but started with the first.

I spent some time doodling in Autocad and came up with a scheme but that scheme required more than I am able to do. Next stop was Roachwerks and Gordon was able to give me advice and assurance. He then got a check and today I got a box of parts.

First out of the box was the nose cone. It is sized to fit a 3" tube.

PEPP1-NC-1.jpg


PEPP1-NC-2.jpg
 

JAL3

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Next out of the box was a bag of what at first glance would seem to be a dozen nose cones. Actually, they are a dozen hemispherical ends fitted for a BT50. They are going to be the tops of my Falcon engines.

PEPP1-falcon-tops.jpg
 

JAL3

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Gordon recommended PML tubing and, true to his word, a piece of 3" tube was next out of the box.

PEPP1-BT-1.jpg
 
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JAL3

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The really hard part was the after bulkhead. It had to be drilled for 12 separate BT20 tubes at a 35 degree angle. I then had to come up with a way to miter all those BT20s together. Gordon solved the problem and simplified it a bit. He balsa to the top of the plywood bulkhead and gace it a shoulder to receive the BT. He then drilled through both. Now the only miters will be the angles on the motor nozzels and I think I have that taken care of.

PEPP1-aft-bulk-1.jpg


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JAL3

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Just for grins, I stuck it all together. This is a project that is going to take some time and I have other priorities right now but I had to do some playing tonight.

PEPP1-central-stack-1.jpg
 

JAL3

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Decided to celebrate the 21st of November (it only comes around once per year, you know) by starting work on my PEPP aeroshell. The first thing I wanted to do was get a handle on the motor motors. After checking the CAD drawings I had made, I decided to cut 12 pieces of BT20 to a length of 4 inches. Cutting tubes has never been one of my greatest skills so I decided to try something new. I purchases a small hose clamp that is finger tightened. I then proceded to mark out 4" increments on my tubing and set the clamp in place as a cutting guide.

PEPP1-hose-clamp.jpg
 

JAL3

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After a while, I had a dozen segments of BT20 tube, all about four inches long. I learned that the clamp works most easily if it is not tightened too much. I tighened it just enough so that my thumb could hold it in place as the X-acto did its damage. When I could not gut any more because of the screw, I rotated the clamp, used the blade of the knife to get it flush with the cut and started to cut again.

PEPP1-4-inch-tubes.jpg
 

JAL3

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With the tubes cut, I worked them into the centering ring that Gordon of Roachwerks had cut and immediately noticed a problem. The upper ends of the tubes were interfering with each other. 4 inches was too long.

PEPP1-4-inch-placed-1.jpg


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JAL3

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I only wanted 1.75 inches exposed from the bottom of the centering ring as measured from the longer side (due to the angle). I removed all but one of the tubes and used a tape measure to decide that the tubes would probably fit if cut down to 3.25 inches. I proceeded to mark all of the 4" tubes at 1.75 and 3.25 inches and recut them.

PEPP1-motor-tubes-1.jpg
 

JAL3

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I took the shortened motor tubes and inserted them all into the centering ring up to the 1.75"; mark. There was a slight bit of crimping at the forward end of some of the tubes but they seemed workable to me.

PEPP1-motor-tubes-2.jpg


PEPP1-motor-tubes-3.jpg


PEPP1-motor-tubes-4.jpg
 

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Almost half a year passed before I got back to work on this project. For various reasons, including the intrusion of "real life", getting involved with other things, having my large format printer need some work and, most of all, having my wife hide the parts from me during one of her "clean the house" episodes, I just didn't get around to it. When I did, I found myself wondering how to proceed and trying to remember what I had planned.

First up was to actually install the thrust rings I had cut. A quarter inch was marked off of a spent casing and that was used to shove the thrust rings into place. I found the fit to be very tight on almost all of them and actually worried about crimping the tubes at times. The rings were secure in place with white glue.

PEPP1-motor-tubes-5.jpg


PEPP1-motor-tubes-6.jpg


PEPP1-motor-tubes-7.jpg


PEPP1-motor-tubes-8.jpg
 

JAL3

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I didn't want to just have tubes protruding from the aeroshell. I wanted it to look something like the prototype which had long tapered bells. I asked Gordon of Roachwerks about cutting some from balsa to scale diminsions and he thought I was nuts. He suggested wrapping the ends of the tubes with very thin balsa and trying to sand in the correct profile. I started to do this with some 1/32 balsa but, even whetted, it was to stiff to wrap a BT20. The solution was to wrap the tubes with something else. Since I had recently bought a large package of label paper, I decided to give that a try.

I marked an 8.5x11 sheet to cut a 1.75" strip and used a guillotine style paper cutter to get the strip. I then cut a series of successively narrower strips, reducing the width by 1/8" each time. The widest strip was applied first and the the smaller ones in order were applied, always trying to stay flush against the aft end. This started to build up the tapered cone and also gave a bit of 3D definition to the nozzles.

PEPP1-nozzle-1.jpg


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PEPP1-nozzle-3.jpg


PEPP1-nozzle-5.jpg


PEPP1-nozzle-6.jpg
 

JAL3

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When I applied the final, 1/8" wide band, I was quite pleased. I had gotten the effect I was looking for.

PEPP1-nozzle-7.jpg


PEPP1-nozzle-8.jpg
 

JAL3

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I wanted to see what the final result would look like so I took the first nozzle I had done and primed it with white.

PEPP1-nozzle-primed-1.jpg


PEPP1-nozzle-primed-2.jpg
 

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When the white had dried, I gave it 2 coats of a metallic "hammered silver". I really think it looks good.

PEPP1-nozzle-silver-1.jpg


PEPP1-nozzle-silver-2.jpg


PEPP1-nozzle-silver-3.jpg


PEPP1-nozzle-silver-4.jpg
 

TheAviator

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What is a PEPP-1 Aeroshell? Considering you are clustering 12 motors, I already think it's cool. :cool:
 

JAL3

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What is a PEPP-1 Aeroshell? Considering you are clustering 12 motors, I already think it's cool. :cool:
It was used to test deployment systems for a Mars mission way back. Think of it as a UFO shaped thing with 12 canted motors.
 

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I liked the effect of building up the Falcon engine nozzles from label paper but it is sure a laborious process. I averaged about 1 each day and that is only on days when I could actually get over to work on them. As that was progessing, I decided to try and get some other work done simultaneously. I began to fill the after bulkhead with Elmer's filler and sand it smooth. Additionally, I took the 12 BT50 hemispherical nose cones and treated them to a dousing with thin CA in an attempt to harden and seal them.

PEPP1-tank-tops-1.jpg
 

JAL3

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5 done, 7 more.

This gets old.

PEPP1-5-down-a.jpg


PEPP1-5-down-b.jpg
 

JAL3

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Thanks. I like the way they're turrning out as well. I just don't like making them.

The 6th completed one was taken down today and I put the seventh in the booth to paint. I have to say that this last one has been the least trouble. THe label paper seemed to want to line up right for a change.

PEPP1-6-down-1.jpg


PEPP1-6-down-2.jpg
 

JAL3

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I sure get tired of peeling the backing off of label paper though.

This is the result of 1 nozzle.

PEPP1-nozzle-trash.jpg
 

JAL3

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The dau before yesterday, I got the 7nth one done.

7-done-a.jpg


7-done-b.jpg


7-done-c.jpg


7-done-d.jpg
 

JAL3

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And today I got the 8th done. Only 4 to go.

8-down-a.jpg


8-down-b.jpg


8-down-c.jpg
 

JAL3

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really cool work John,
IF others want to see the drop test video check this out on youtube
http://www.youtube.com/watch?v=lZ0K9LLmWiM

web search also said these were for parachute test for the Viking landers
Thanks.

I found that vid a couple of days ago and watched it and the others in the group. It is of the PEPP 2 which had 8 engines. I actually have some plans drawn up to do that one as 8x24mm if this works out.

The one I'm doing now is the PEPP 1 which had a cluster of 12 falcons. I have been unable to mind much on it outside of ROTW.
 

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I'm taking a bit of a break from this one. A friend "borrowed" my paint booth for some project at work. In taking it, he also took the supplied I had for this project. He says they're sitting in his van.
 

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I decided to work on another part of this project while awaiting the return of my materials.

The "tanks" for the Falcon motors were and remain a compromise. Mitering a piece of BT20 to a piece of BT50 at an angle and expecting it to survive the canted thrust of a dozen C motors was going to be problematical. I had decided early on in the project that I would "cheat". The BT20 motor tubes are mounted at the proper angle through the plywood aft bulkhead; instead of fixing the BT50 tanks directly to them, I decided to attatch them to the opposite side of th bulkhead. I still had to fabircate the suckers though.

I began by cutting a 4.5" length of BT50. I then made a vertical slit along one end and removed hald of the tubing for a length of about 1". The tubing was removed to allow the BT50 to sit on the aft blukhead and to accomodate the built up area near the center. I then held the cut tube in place and made pencil marks to indicate where the proper tube would be cut deeper/longer.

PEPP1-falcon-tanks-1.jpg


PEPP1-falcon-tanks-2.jpg


PEPP1-falcon-tanks-3.jpg
 

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