Arapahoe-J - Successful L2 Cert!

First off, thanks again folks for the kind words. I'm pretty happy with how things are going so far.

qquake2k said:

Centering rings turned out nice. Your fly cutter did a good job.

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Thanks. You do have to go slow though, and there can be a lot of smoke toward the end. My cutter has quite a few rings and bulkheads under it's belt at this point, and is beginning to dull. It is definitely time to break out the bench grinder and try to sharpen those up. It gets the job done though, and now that I know how to do this I don't ever have to be stuck waiting for that extra centering ring I forgot to order to arrive.

qquake2k said:

I think if it were me, I might try hand sharpening it with a file first. If you do use your bench grinder, go slow and quench it in water often. If it gets too hot, it can weaken the metal.

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I'll try with a file first. I don't want bits flying off this thing at 600 rpm later. Worse comes to worse, I'll just pick up another one. At $6 I have gotten my share of bulkheads and CRs from this one, probably 50+ at this point.

Thanks for the tip, Captain.

Fin can work.

Starting with the motor mount. The Slimline was attached with JB Weld, and the excess was used to attach the aft CR and begin the Slimline 38-54 adapter. The slightly thicker aft CR was attached later using Aeropoxy. The adapter was also completed at that time. Once the CR sandwich was completed I used the Dremil with sanding drum to taper it so it let the retainer stick out ~1/16".



It was finally time to cut the fin slots. I had been avoiding this, but it ended up easier than I imagined.

First I cut all three bt slots, no problem getting them straight. I used the Dremil with a grinding wheel to make a notch that I could get my Zona saw in, and cut the slots by hand. For the boat tail I started the slots with a heavy Xacto knife, and finished them with the Zona saw. The hard part was keeping the slot line true from the tube onto the boat tail, but I made a tool for that from scrap plywood.



The inside of the boat tail was scuffed up with 50 grit and a dull Dremil grinding wheel. The MM was glued in with Aeropoxy at the aft only using the 4-54 and coupler-54 CRS to ensure the MM stayed in line. These were removed easily after cure as the fin slots allowed easy access from below.

Post fail!

Nothing to see here, please move along to post 44 and 46 for fin post recap.

Looks great! Can't wait to see it in person! 😁

I wish I knew why the pics in post 36 only show as links (and now they don't show at all). Sorry. I'll try to fix them tonight.

I like this build so far!

It doesn't look like the attachments actually got uploaded. Even when I click on the link I just get forwarded to a blank page.

Cl(VII) said:

I wish I knew why the pics in post 36 only show as links (and now they don't show at all). Sorry. I'll try to fix them tonight.

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Cl(VII) said:

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.

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Not to fuel the competitive fires, but my upscale Scortch looks pretty darn good now that I've got the decal on. Can't wait to see yours done.

Yes, that's a challenge.

AlfaBrewer said:

Not to fuel the competitive fires, but my upscale Scortch looks pretty darn good now that I've got the decal on. Can't wait to see yours done.

Yes, that's a challenge.

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Ah, now you've gone and done it. I wonder if you can have an entire rocket chromed? Hum...

Cl(VII) said:

Ah, now you've gone and done it. I wonder if you can have an entire rocket chromed? Hum...

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As soon as I get caught up with work, I'm headed to NAPA to see if they can mix a platinum color. I have a design in the works that'll need it, based on it's title.

Lets try that messed up post again...

Fins!

The most distinctive part of this rocket have to be the fins. This is pretty standard stuff, I cut oversized fin blanks from a large sheet of 1/4" Baltic birch 6 ply from Woodcraft. These were pegged together with a section of dowel, cut close to final shape on the band saw, and finished on the belt sander.



I actually made things harder than they had to be by making a mistake cutting the blanks that led to me having to make a replacement fin after the test fitting showed my stupidly truncated fin was a problem. I cut the oversized fin blanks incorrectly that led to one not coming all the way to a point. I had hoped that it would be enough to get into the hidden tab, but no luck there was still a sliver of surface fin past the mistake, so a fourth fin was made by pegging a piece of ply to the good pair and careful cutting and sanding to match.

Cl(VII) said:

Fin can work.
The inside of the boat tail was scuffed up with 50 grit and a dull Dremil grinding wheel. The MM was glued in with Aeropoxy at the aft only using the 4-54 and coupler-54 CRS to ensure the MM stayed in line. These were removed easily after cure as the fin slots allowed easy access from below.

View attachment 185257

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Fins continued.

PML specifies the slotable area of their NC/boat tails, and this requires that the slot not be continuous as you see with the slots I cut. I decided not to get fancy and try to get this right blind, so I cut the slots then used my original fin template to figure out the tabs and cut those into the template. Here I should mention that I always make the tabs a bit too long, and sand to fit when it is time to epoxy the fins on. The tabs were drawn onto the stack, and a hole drilled to make pivoting the band saw possible. The tabs were then cut out with the band saw and finished on the disk sander.



Test fit! Starting to look like a fin can. Remember the tabs are intentionally long now, that will get fixed.



One more thing not pictured. The holes in the fins have been plugged by dowel pieces glued in with TBII, and sanded flush.

This brings me up to date, so the thread will slow down, even more, as I don't have backlogged material to rely on. In fact I am updating this tonight because I was getting set up to glass those fins and realized I was too low on laminating epoxy. Hence spending my rocket time updating this thread. I will need to order that to get things moving again.

Gary Byrum said:

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See, now this is why I use rail buttons. They don't start unnecessary hostilities with demonic spirals.

Also, wow, that is the strangest response I've ever gotten to a build thread (or possibly anything else, ever). I feel it needs a pic, so BONDO candycanes:

ChrisAttebery said:

It doesn't look like the attachments actually got uploaded. Even when I click on the link I just get forwarded to a blank page.

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I think that the repost has fixed things, so I'm going to delete the original.

Cl(VII) said:

See, now this is why I use rail buttons. They don't start unnecessary hostilities with demonic spirals.

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Cl(VII) said:

...

View attachment 185335

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That is one sexy fin can ! Yeah, I said it.

Gary Byrum said:

View attachment 185340

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Ah yes Ronnie, now that guy looks familiar.

_{Someone PM LWBercini and tell him his friend has flipped his lid. I'll keep talking to him until help arrives...}

This project, especially the use of hand tools, demonstrates that man is still the master of technology. Excellent thread and deserving of a box full of Baby Ruth candy bars!

tmacklin said:

This project, especially the use of hand tools, demonstrates that man is still the master of technology. Excellent thread and deserving of a box full of Baby Ruth candy bars!

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Thanks. Flight ready candy bars I'm sure...every 6 year old knows they taste better after they have flown.

That fin can is looking sweet!

Looking good.


TA

samb said:

That is one sexy fin can! Yeah, I said it.

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Indeed it is. I'm a sucker for a killer fin concept and this one got my complete attention the 1st time I laid eyes on it. There's nothing quite like it. Both of my Arapahoe's fly supremely and worth all the time I put into them. This one is shaping up very nicely.

Is the K version next?

cwbullet said:

Is the K version next?

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We'll I have a Cherokee-I
Will have an Arapahoe-J
What could I do, a Comanche-K? Beyond my abilities, budget, and wife's tolerances I believe.

In all seriousness, this one should be good to fly on a K at a field with a higher waiver than my home field...there are a few within 3 hours with waivers that would accomidate. I think my next upscale will be a BT-60 Trident that flies on F-G motors...I already have the parts for that.

Thanks for the kind words folks. I am quite pleased with how it is coming together.

I am starting to think about how I will hold the electronics bay in since my laminating epoxy will be a week or so in arriving. Since the bay is to be completely removable screws will be in order...the question is 3 or 6. My fear is that upon the fin can hitting the end of the cord the shock will be transferred to the bay and that force concentrated completely into the screws. Perhaps I will make one more CR to sit on the aft side of the bay for it to rest against. Then the force will be concentrated on the ring mainly as that will be the stiffest joint. I'm not as worried about the NC event as the NC will be far lighter than the fin can and thereby impart far less energy.

I'm probably over thinking this, but I haven't done DD this way before.

Cl(VII) said:

Ah, now you've gone and done it. I wonder if you can have an entire rocket chromed? Hum...

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Of course, no sooner do I open my mouth, then I manage to screw up what was otherwise a pretty decent paint job. I decided the nose cone wasn't glossy enough after I shot the body with clear, so I hit the NC with clear coat. Apparently Rusto clear and Rusto black don't play well together.

Oh, well. It'll fly fine with a crackle finish nose until I sand it off and repaint.

The challenge still stands, though.