Little Joe (I) progress

[Doug Sams]

This thing has been sitting on my bench for ~four years collecting dust and gathering dents from the occasionally dropped object. I finally put some more primer on it and applied the orange. I should get the silver on it in a few days, and can resume work on the capsule soon, I hope. I figure to fill most of those motor tubes when I finally do fly it :D Doug .
http://www.doug79.com/little-joe/lil-joe2.jpg

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[jeffyjeep]

Hi doug. That's really nice! Is this a scratch build? How did you do the taper below the capsule?

[dwmzmm]

Nice!! Can't wait to see the finished product. Are you going to fly it fully clustered as your last picture shows?

[Doug Sams]

Nice!! Can't wait to see the finished product. Are you going to fly it fully clustered as your last picture shows?David,

It's looking like it's gonna be kinda heavy. The fact that it uses two concentric body tubes contributes greatly to that.

My original thought was to use 2 or maybe 4 motors, in the inboard tubes. According the James Duffy, the standard real configuration was usually two large inboards (Sergeants) and four small outboards (Recruits), but the actual airframes were made to handle up to four Sergeants.

(BTW, I followed the actual motor pattern, but used eight equal sized tubes rather than, say, four BT-20's and four MicroMaxx, which would be much closer to scale. But clustering MM's is not my thang.)

So I'll probably stuff it with four A's in the inboards and maybe a couple ½A's in the outboards. I need to run some sims to see what the rod speed, altitude, and optimal delays look like.

I had been thinking four A3-4T's would be about right. That'd be C impulse. But given the weight (and obvious drag), I'm wondering about four A10-3T's plus maybe some outboards. The extra big thrust spikes will help get it off the rod. I have a bunch of plugged A10's I could use mixed with
A3-4T's if I need the longer delay.

Anyway, there will likely be at least four motors on the first flight :)

Doug

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[Doug Sams]

Hi doug. That's really nice! Is this a scratch build? How did you do the taper below the capsule?Thanks!

Yes, it's a scratch build. The capsule is from the Estes 1/35 scale (ST-20) kit of recent vintage.

I followed what I understand to be is a pretty common setup. It uses ST-20 for the forward-most tube to mate with the capsule, then transitions to BT-70.

BT-70 (2.217" OD) is still a tad small for perfect scale. According to Rockets of the World, the LJ's OD should be 80", which translates to about 2.29". I thought about different ways of building up the airframe thickness to get there, but all I could see were rat holes - those places where projects go to die because you find yourself hopelessly wrapped around the axle trying to achieve some level of detail that's 1) un-achievable and 2) takes all the fun out of it.

(BT-70 with a piece of 1/32" balsa wrapped around it would be very close to perfect, but I figured the probability was 4 in 5 that I'd make a huge frickin' mess trying that.)

So I just stayed with the recommended BT-70 :)

The inside ST-20 tube runs all the way down to the motor tubes. This way, there's no step inside the airframe for the laundry to get snagged on. BTW, here's an old write-up I did on the motor section: http://www.doug79.com/little-joe/rings3

It's been a while, but as I recall, the ST-20 was centered using the uni-rings from Totally Tubular. I believe those are available elsewhere now - BMS, I think. The anular radius of the ST-20:BT-70 ring is so thin that it breaks easily. But I pieced them together around the tube and made 'em work.

Lastly, in answer to your question, the transition was drawn up in Autocad, printed out, and taped to a piece of 1/64" birch ply. Then I cut it out with scissors and wrapped it in place :)

As always, all cutting and crafting errors are hidded with FnF :D

Doug

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[sandman]

Thanks!

Yes, it's a scratch build. The capsule is from the Estes 1/35 scale (ST-20) kit of recent vintage.

I followed what I understand to be is a pretty common setup. It uses ST-20 for the forward-most tube to mate with the capsule, then transitions to BT-70.

BT-70 (2.217" OD) is still a tad small for perfect scale. According to Rockets of the World, the LJ's OD should be 80", which translates to about 2.29". I thought about different ways of building up the airframe thickness to get there, but all I could see were rat holes - those places where projects go to die because you find yourself hopelessly wrapped around the axle trying to achieve some level of detail that's 1) un-achievable and 2) takes all the fun out of it.

(BT-70 with a piece of 1/32" balsa wrapped around it would be very close to perfect, but I figured the probability was 4 in 5 that I'd make a huge frickin' mess trying that.)

So I just stayed with the recommended BT-70 :)

The inside ST-20 tube runs all the way down to the motor tubes. This way, there's no step inside the airframe for the laundry to get snagged on. BTW, here's an old write-up I did on the motor section: http://www.doug79.com/little-joe/rings3

It's been a while, but as I recall, the ST-20 was centered using the uni-rings from Totally Tubular. I believe those are available elsewhere now - BMS, I think. The anular radius of the ST-20:BT-70 ring is so thin that it breaks easily. But I pieced them together around the tube and made 'em work.

Lastly, in answer to your question, the transition was drawn up in Autocad, printed out, and taped to a piece of 1/64" birch ply. Then I cut it out with scissors and wrapped it in place :)

As always, all cutting and crafting errors are hidded with FnF :D

Doug

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If you can still change it how about setting it up for the long burn Quest motors?

BTW, what is the main body tube size?

[Doug Sams]

If you can still change it how about setting it up for the long burn Quest motors?

BTW, what is the main body tube size?It's BT-70 which necks down to ST-20 at the forward end. The motor setup is all glued in. Not sure which long burn motors you mean, so I'm not sure if they could fit. Definitely no D5's. Maybe some of the new, small stuff.

Doug

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[sandman]

OK, sorry, I didn't see that...nevermind.

[dwmzmm]

David,

It's looking like it's gonna be kinda heavy. The fact that it uses two concentric body tubes contributes greatly to that.

My original thought was to use 2 or maybe 4 motors, in the inboard tubes. According the James Duffy, the standard real configuration was usually two large inboards (Sergeants) and four small outboards (Recruits), but the actual airframes were made to handle up to four Sergeants.

(BTW, I followed the actual motor pattern, but used eight equal sized tubes rather than, say, four BT-20's and four MicroMaxx, which would be much closer to scale. But clustering MM's is not my thang.)

So I'll probably stuff it with four A's in the inboards and maybe a couple ½A's in the outboards. I need to run some sims to see what the rod speed, altitude, and optimal delays look like.

I had been thinking four A3-4T's would be about right. That'd be C impulse. But given the weight (and obvious drag), I'm wondering about four A10-3T's plus maybe some outboards. The extra big thrust spikes will help get it off the rod. I have a bunch of plugged A10's I could use mixed with
A3-4T's if I need the longer delay.

Anyway, there will likely be at least four motors on the first flight :)

Doug

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Doug, what are the specs (total length, weight, etc) going to be when finished? With the size and swept back angles of those fins, it should be pretty stable even if flown clustered. I think you know I converted the Estes Gauchito kit from a single engine to a four engine so I could enter it in the Future Scale/Science Fiction event. Using four 1/2A 13 mm engines, it flew pretty high and was very, very stable even with no additional nose weight needed.

This thread is cool as it was just a coincidence that I watched Duffy's DVD on the Little Joe - I a couple of weeks ago while thinking of doing such a project. Please keep us informed of your progress! :D

[Doug Sams]

Doug, what are the specs (total length, weight, etc) going to be when finished? With the size and swept back angles of those fins, it should be pretty stable even if flown clustered. I think you know I converted the Estes Gauchito kit from a single engine to a four engine so I could enter it in the Future Scale/Science Fiction event. Using four 1/2A 13 mm engines, it flew pretty high and was very, very stable even with no additional nose weight needed.

This thread is cool as it was just a coincidence that I watched Duffy's DVD on the Little Joe - I a couple of weeks ago while thinking of doing such a project. Please keep us informed of your progress! :DI'll have to get you the specs later, but I'll say now that I'm not worried about stability. I'm pretty sure I could stuff it full of motors :) But when I pick it up, it feels heavy. So I can only anticipate that it will need most of those motor tubes for getting a safe altitude :)

Doug

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