Arapahoe-J - Successful L2 Cert!

OK, I like flying H and I motors a lot, but I'd like just a bit more flame as an option. Also, it looks like I can sneak in an occasional J motor without getting the stink eye from the wife...I might get away with a K once or twice a year, but it ain't looking good. Therefore, I wanted a rocket that can handle H-K, but is really in a I-J sweet spot. Also, I don't really like building High power kits, just not my thing. I did a scratch design for my L1, and have been enjoying upscale recently, so I decided to go with an upscale compliment to my Cherokee-I, an Arapahoe-J for my L2 project. Specifically a 4" upscale. Below is the tentative design, I am sure some details will shift, and the color scheme may change, but you;ll get the overarching ideas.

This is going to be 4" Magnaframe, 54 mm, and be DD with a completely removable electronics bay (for easy set up). I was going to do it classic zipperless design, but ended up with a slightly modified version after I messed up my order and came up short 3" on the motor mount. I am also putting in a nose cone bay to house a future tracker, or make nose weight adjustments if needed.


The decal I have from Mark says "Arapahoe-J"



Original Thrustline kit, not my model

A LUNAR club member has a very large Araphoe clone that he transports on the roof of his vehicle.

Looking forward to see your project.

This a great flying rocket. I have two now. Scratch builds of the original size and an upscale to BT-80. I just flew the upscale for the first time this past weekend and WOW! I opted for a different Phoenix design on the upscale, as I really didn't like the original. Don't forget to show us some build pics.

Gary Byrum said:

This a great flying rocket. I have two now. Scratch builds of the original size and an upscale to BT-80. I just flew the upscale for the first time this past weekend and WOW! I opted for a different Phoenix design on the upscale, as I really didn't like the original. Don't forget to show us some build pics.

View attachment 183288

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Your purple version in the gallery is what has me leaning toward that for mine. Also, I am planning this as a nauseatingly detailed build thread. I want to document as best I can how you can scratch most of a rocket with a few low end power tools, a lot of sandpaper, and some patience. Kind of a Harbor Freight version of the qquake2k method.

Cl(VII) said:

Your purple version in the gallery is what has me leaning toward that for mine. Also, I am planning this as a nauseatingly detailed build thread. I want to document as best I can how you can scratch most of a rocket with a few low end power tools, a lot of sandpaper, and some patience. Kind of a Harbor Freight version of the qquake2k method.

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That shade of purple came from a can of Valspar. They didn't have the glossy so I improvised and did a "Future" bath to make it so. I get the whole lengthy thread thing, but can we expect you're not attempting a year long, drawn out, over the top.....(you get the idea I'm sure) record breaker? Oh, and for what it's worth, that Phoenix design I used on the big one, came from a google image search for tribal tattoos. Unless you're partial to the original design, there were quite a few selections in there.

Gary Byrum said:

That shade of purple came from a can of Valspar. They didn't have the glossy so I improvised and did a "Future" bath to make it so. I get the whole lengthy thread thing, but can we expect you're not attempting a year long, drawn out, over the top.....(you get the idea I'm sure) record breaker? Oh, and for what it's worth, that Phoenix design I used on the big one, came from a google image search for tribal tattoos. Unless you're partial to the original design, there were quite a few selections in there.

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I have a bit of a head start already. I suspect the build will take 6-8 weeks. There will be some lull while the primer, sand, primer, sand cycles go after that. I'm targeting the finished project around the end of the year.

To start off the obligatory parts pic:



Yes the large fins are cut in this pic, I'll get to that shortly.

Major Parts and Sources:

Wildman:
4" LOC Nosecone
4" PML Nosecone (destined to be boat tail)

Giant Leap:
4" x 4' Magnaframe
4" x 4' Phenolic Coupler
54 mm x 18" phenolic (motor mount)
54 mm Slimline
54-38 mm Slimline adapter
Aeropoxy structural

Woodcraft:
1/4" x 3' x 2' sheet of Baltic birch plywood

One more for tonight...tube cutting time:

I need 2 pieces of airframe and two couplers along with a second inner coupler for the electronic bay.

I took great care to square the fence on my compound miter saw before cutting, and yes it was off. I replaced my fence (the yard kind) this year and the heavy use and poor treatment during the process had the fence (the saw one) about 2 degrees off square. I know from experience that such a deviation from square makes for enormous headaches later. The factory ends of the Magnaframe were very nice and square. As such, I have chosen to have the factory ends meet at the aft break point (apogee event). The newly cut ends will join at the NC and the boat tail. Both points will be forgiving of slight imperfections as the aft will be blended into the boat tail with bondo, and the fore joint at the NC will be at a color transition which masks imperfections.

The tubes were cut to length with my cheapo miter saw.



The electronics bay requires a double wall with the internal being recessed 1/4" on each side to accommodate the bulkheads. The inner coupler was split lengthwise using a table saw (again, among the cheapest available). The challenge here is making sure the tube doesn't rotate during the cut. You can accomplish this several ways, but the easiest I think is to tape it in several places to a 2x4 that will slide against the fence while you cut the tube. This cut doesn't have to be perfect, in fact I took out a bit more than I needed too, but I will make sure my bulkhead fits very snugly which will minimize the worries about ejection gas leakage. You can see once cut how the inner coupler slides in.

Subscribed! Looks awesome! I'll definitely try to come out to see that one!

op: I'm in

Subscribed!

First off, I'm glad some of you are interested. Thanks.

However, This is why I don't usually do build threads. I let the thread languish while I work on the rocket, or I do something fun like spend the entire weekend at the Red Bull Air Race (HIGHLY RECOMENDED!) with the boys.

Not rockets, but fun!

Anyhow, I have a two plus hour flight to Grand Rapids tomorrow, so I will get some catching up done hopefully.

One for tonight.

Bulk plates: how to make them cheaply and effectively with a $56 Harbor Freight drill press and a $6 fly cutter.

But first, the glued up electronics bay which was glued together with Aeropoxy.



The bulkheads will be made from two circles of 1/4 ply one which fits inside the coupler and a second that fits inside the double walled portion for a total 1/2" bulkhead.

To cut these you set the fly cutter with both cutters at the same spacing making sure you will end up slightly oversized (1/16" or so). It is important to pay attention to which side of the cutter is pointed in, you don't want the angled side...no asking how I know . Also, make sure to clamp the wood down, tightly!



After cutting two slightly oversized bolt them together using a lock washer, and you are ready to employ your poor man's lathe. Just chuck that bolt up, rig up a sanding block, and sand until it snugly fits.



...and repeat the process for the double walled thickness bulkheads.

Finishing up the bulkheads.

Next up is to glue them together (Titebond II used here). A bolt keeps them tight and I always throw in some clamps...can't hurt.



After that is all dry I have to take care of those center holes as I plan to use U-bolts for attachment. To that end pieces of dowel are cut a bit long and Titebond II -ed into place. When the glue dries a quick hit on the belt sander flattens them off. Then I lay out the holes that need drilled for the U-bolt (2), threaded rod (2) that holds the 3D printed Missileworks sled, terminal block holes (2 each) and hole for charge well (1).



Speaking of charge wells...I make these from 1/2" PVC caps that are sanded round on the disk sander and a hole that is tight to the screw is drilled in the bottom with countersink. There is also a small hole in the side to accommodate an ematch.



The holes are drilled with the appropriate sized bit for each. With the charge well hole being intentionally very snug.

I then solder on the terminal blocks with the wires pulled through the holes. I set up all my electronics bays with the same JST connectors (which I tape wrap for flight) and threaded rod spacing, so my altimeters can easily cruise between. Once the terminal blocks are soldered on and continuity checked (repeatedly) they are epoxied in place making sure to get some epoxy in the hole. Now my solder joints are encased in epoxy for all eternity, I like to think this protects them, and given my soldering skills extra protection is welcomed. The U-bolt is put on (blue threadlock used) and the charge wells are placed in (vinyl locknut here).



And all snugged down with the threaded rod cut to length and topped off with cap nuts.



Note: the rod is fixed to one bulkhead by vinyl locknuts on the inside and blue threadlock in the capnuts. Having the rods fixed on one side makes assembly less frustrating. Also, all metal external to the electronics bay is stainless steel.

Boat tail progress.

I have never adapted a nosecone into a boat tail, or done through the wall fins with a boat tail. Therefore, do not take this as the way to do it, just the way I made up as I went along.

The some of the NC shoulder had to go, and my cordless (nearly useless) Dremil was too slow, so I used my Zona saw and did it by hand. I left several inches of shoulder to give me a good amount of surface area to glue. Next I seriously roughed up the NC shoulder and the inside of the short segment of body tube. The body tube had gone through two cycles of Bondo/sand at this point...The Magnaframe spirals are canyon like. The cone was glued in with Aeropoxy.



Next up I wanted to mark the fin slot areas while the tip was still in place. Then I could use the tip as a reference point. I first marked off the tube with 6-lines using a marking guide generated from the payload bay's tools, and extended those marks using a piece of angle aluminum as a marking guide. To extend these lines onto the curved nosecone I may a marking guide from 110 lb card stock. After taping two strips together I drew a reference line down the center, cut the thin end to a point, and cut a slit ~1/8" wide centered on the reference line. I could then line up the reference line with the lines on the tube, and the point with the nosecone tip. This gave me a very straight extension of the body tube line. I then scotch taped the marking guide in place and drew the line with a sharpie.

Next I have to turn this thing into a boat tail. Perfect scale would be 10.5" long, and that looks really close for the slimline, so I braced the tube to a scrap piece of 2x4 using masking tape (keeping the tube square will keep the cut square), and extended the floor of my miter saw with a scrap of hardboard. I then marked 10.5" down the 2x4 from the nose/bt joint (note: if you use a flexible ruler on the nose cone to measure 10.5" you will end up shorter than you intended), and made the cut.



Looks good, right? One problem, the ID was too narrow for the slimline. I was afraid that sanding to fit would leave the shoulder too thin at the bottom, so I cut ~0.15" more off the boat tail, and sanded the ID a tiny bit with my dremil fitted with a sanding drum. Now the slimline fits perfectly.

Wow, the hits just keep on comin' ! Thanks for documenting this and continuing the string of awesome L2 projects we have going on in our neck of the woods.

qquake2k said:

Great build thread! I love the Arapahoe design, it has beautiful lines. This is going to be an awesome rocket! And hey, I still have Harbor Freight tools...

I built a kit for my L1 (Minie Magg), but scratch built my L2 (upscale Shadow). Scratch building my L2 gave me a little extra measure of satisfaction when I flew it successfully.

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I not only meant using Harbor Freight tools, but employing my Harbor Freight like techniques...note the prevalence of masking tape in how I build. Like you with your L2 I was particularly satisfied that my L1 was a scratch build. Doing scratch builds is also a good way of managing costs. If I bought everything precut it would take me way less time to build, and then I would buy way more kits, then I would have no motor money...vicious cycle. Its also why I tend to build 3 or 4 LPR for every HPR.

samb said:

Wow, the hits just keep on comin' ! Thanks for documenting this and continuing the string of awesome L2 projects we have going on in our neck of the woods.

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There have been a lot of nice L2 projects lately. I'm glad we have a mutual admiration society, if DARS were a competitive (one-up manship type) group it would get ridiculous real quick.

Cl(VII) said:

View attachment 183287
Original Thrustline kit, not my model

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How did I miss this!? That's my original build & photo from 2006! After numerous launches and repairs, this Thrustline original finally met its maker on an AT F44 CATO just a few weeks ago. I was able to salvage the Nose Cone & Boat Tail for a future rebuild. Anyhow, I'm enjoying seeing your upscale thread. Did you use 2 different NCs for a specific reason, or just ones you happened to have?

https://rocketryforumarchive.com/showpost.php?p=284727&postcount=8

What do you do when you get to the Grand Rapids airport 3 hours early? Update your build thread, obviously.

The strake fins are next. These are a touch over .6" wide and run nearly the full length of the bt. The tricky parts are the small angle the ends have, and ultimately getting them to line up at the bt-fincan joint. The joint will have some visual forgiveness as that will be a paint change whic will mask any tiny variations.

Table saw was used to rip 6 30" x .65" strips from the same 1/4" plywood that everything else is made from. These are then bundled using my favorite tool, masking tape. Bundling this way will ensure that all 6 cuts are the same.



Now to keep things perfectly even a blocks were taped on to keep everything flush. I would have ideally made this cut with a miter saw, but I don't have a sliding miter saw, and my saw has a cut length just under 6", so another solution. I chose to freehand a single triangle on the bandsaw and then sand to the proper angle on the belt sander. I then taped this to the bundle to act as a guide to ride against the fence of the table saw.



This worked surprisingly well until the cut off piece slipped down the gap next to the blade and caused the whole mess to kick a bit and put a bite in the freshly cut angle. This cleaned up nicely on the belt sander, and the variance that is left will go away when I round the leading and trailing edge. Three came out perfect at full length (30"), and 3 had a bit of flaking at the tip. Since three pieces will only be about 10" long I will fix the three imperfect one's during round over and cut to length after rounding over. The final challenge was how to keep them from warping until I need them in a month or so...my second favorite tool behind masking tape is cheap clamps. My workbench provided a flat, stable surface.

dpower said:

How did I miss this!? That's my original build & photo from 2006! After numerous launches and repairs, this Thrustline original finally met its maker on an AT F44 CATO just a few weeks ago. I was able to salvage the Nose Cone & Boat Tail for a future rebuild. Anyhow, I'm enjoying seeing your upscale thread. Did you use 2 different NCs for a specific reason, or just ones you happened to have?

https://rocketryforumarchive.com/showpost.php?p=284727&postcount=8

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I'm glad that the rightful builder of the pictured rocket I lifted from a google image search is going to get the credit. We have similar taste in rockets apparently, my current favorite is my Cherokee-I (2.6").

The two different nosecones was indeed on purpose. It turns out the LOC nosecone is almost perfect proportions for the original NC, but a bit stumpy on the tip (I may make a hat for it, but honestly I doubt it. The trick was going to be the tailcone, but as luck would have it the longer PML cone is very close to the curvature of the original boat tail...certainly closer than the LOC. I would have ordered the preslotted boat tail available from PML, but I hate paying extra shipping and I was able to get both cones from Wildman when I ordered a bunch of 24/40 reloads.

Cl(VII) said:

I not only meant using Harbor Freight tools, but employing my Harbor Freight like techniques...note the prevalence of masking tape in how I build. Like you with your L2 I was particularly satisfied that my L1 was a scratch build. Doing scratch builds is also a good way of managing costs. If I bought everything precut it would take me way less time to build, and then I would buy way more kits, then I would have no motor money...vicious cycle. Its also why I tend to build 3 or 4 LPR for every HPR.

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No matter what you call your techniques, they're certainly good ones. I think you're doing a great job.

Looking good!



TA

thobin said:

Looking good!

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+1

I might have to try building one someday...

Looking good, always like the lines on this bird. And your building techniques are fine, similar to how I would do it. It's going to look really nice on the launch pad.

Centering rings, there are quite a few and all but one set of the ODs are the different.

To cut I set up the fly cutter with one tip at the OD of the MM, and the other at the desired ring OD pending its location. The biggest trick with this is make sure that the center cutting tip will cut completely through before the outer, or you will have nothing holding the wood and it will spin. Also, make sure that the angled side of the cutter tip is on the correct side of the cut...you want CRs with flat edges, not tapered. Again, no asking how this lesson was learned, please.

The rings cut were:
54-4" x2 (one to chop up for rail button backing)
54-4" coupler
54-NC ID (yes this was different)
54-~2.4"
54-~2.6"

Note: there is definitely a minimum diameter CR you can cut with a fly cutter, and all plywood is not created equal. The Woodcraft ply allowed for 54-2.4", where as the Michaels ply fragmented before the cut was complete. 54-2.6" was the best there, and that was sketchy.

Nose cone bay. Use to be determined down the road, but it can't hurt to have one.

Started simply by cutting off part of the NC shoulder with the Zona saw, then turned my attention to the nosecone CR that would fit snugly just above the NC shoulder lip, and the matching bulkplate. To make sure the holes line up just right it is easiest to drill them at the same time, so the two were joined with my favorite tool, masking tape. And holes for the T-nuts drilled.



Much to my satisfaction I had a snug fit with the 8-32 T-nuts all around. These were carefully epoxied in place with 5-minute epoxy. Note: Every screw I plan to use in this project will be 8-32, I try to standardize as much as possible, and that is what my rail buttons use.



The inside of the NC, just above the shoulder lip is scuffed up using a dull grinding wheel on the dremil. Scars it up nicely without any chance of accidentally cutting through the NC. The ring is then epoxied in with Aeropoxy, thickened with milled fiberglass so it doesn't run wild during curing. The top of the T-nuts are also protected from accidental epoxy fouling by what else, little bits of masking tape.



I'm running out of the warm up stuff, so I've had to start tackling the fin slots and fins...progress report in due time. It is not as straight forward as without the boat tail, you do a lot of extra work for that look.