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-   -   SEMROC Little Joe II Building Thread (http://www.oldrocketforum.com/showthread.php?t=1338)

CPMcGraw 01-04-2007 10:07 PM

Quote:
Originally Posted by tbzep
I thought the same thing about the center balsa piece. At first I wondered why the original was done that way. I then thought that some builders wouldn't be able to get a good fit and would end up with a bulge across the length of the fin. I doubt I'll ever fly mine on a C motor, so I'm happy with it like it is so far.

I've built the escape tower legs and I'm now on the center support structure. I got tired of doing the tiny detail work so I ut it away for a while and I've built a couple of regular rockets like the Nike-X to rest my eyes. :)

I'll get back to the LJ II in a few days.


Since I haven't closed up the three clams yet, I'm going to cut some additional center pieces from some soft balsa and fit it in place, and then sand them to match the wedges. It also means I need to cut out one additional set of pieces and build yet another fin.

I agree, a "C" motor is just way overkill power for this model. I might consider an occasional "B" flight, but I'll probably limit it to an "A" most of the time.

CPMcGraw 01-05-2007 05:11 PM

Taking an alternate route...
 
Sometimes the original way to do something just ain't the best way to do something, no matter how nostalgic it might seem. Case in point -- the LJII fins. As I tried over and over to get those skins to work out, I kept getting bad results and no real satisfaction. I kept thinking, "How much those fins need to have a full balsa core". But then, I also kept thinking, "How much of a bear those fins would be to sand into that wedge shape..."

My RC builder's sensibility kicked in last night, and I realized I actually had something in my wood piles that was perfect for this task. It's known as "Aileron Stock", and can be purchased in just about any LHS. See the first image:



This piece of pre-shaped balsa measures 1 1/4" wide and 3/8" tall, and comes in 36" lengths. I had two sticks in the pile. Selecting one, I cut off a 3" long piece and marked both sides with a piece of the cardstock containing all those lovely printed fin images. Starting with the long wide edge of the fin, I cut through from one side about half-way, flipped the piece over, and cut through the remaining excess. This left me with a gentle, sandable hump along the wide edge. Using a "T-Bar" sanding tool, I flattened this edge. Next, I cut the remaining edges, ending up with this:



Now I have a solid fin with no ridges, dips, or other gross visual imperfections. All I need to do now is apply the label stock around the sides and edges. If there is a drawback to this method, the solid fin is just a fraction thicker than the built-up fin. Unless you are looking at the original kit fin, this is completely un-noticeable. Weight-wise, it doesn't feel any heavier or any lighter. Actually, it feels about the same weight.

Here is a comparison between the raw stock and the finished fin:



And another view:



I'll continue with the assembly sequence as soon as I finish the remaining fins. I think this is the better way to handle this issue, and provides the more consistent final product.

Till next time...

sandman 01-05-2007 07:11 PM

Craig,

That is NOT a new idea.

Using trailing edge stock is exactly what Centuri did for their 1/45th Little Joe II kit. :D

Gees, you would have thought Carl would have come up with that.

Actually Carl was just sticking to the original Estes version.

I copied the trailing edge stock idea with my 1/35th LJII and my LTV Scout kits.

Now if you cover the trailing edge stock with the cardstock from the SEMROC kit...badda bing, badda boom! No balsa to seal! ;) And those puppys are strong!

CPMcGraw 01-05-2007 07:24 PM

Quote:
Originally Posted by sandman
Craig,

That is NOT a new idea.


It is when the idea hits you at 2 AM... :D

Quote:
Using trailing edge stock is exactly what Centuri did for their 1/45th Little Joe II kit. :D


Actually, that's what I should have said -- Trailing Edge stock; Aileron stock is similar, but has a half-round cut into the thick edge.

Quote:
Now if you cover the trailing edge stock with the cardstock from the SEMROC kit...badda bing, badda boom! No balsa to seal! ;) And those puppys are strong!


I was thinking about the self-stick labels sealed with CA, like we've started doing with other models. Cardstock would give it a tougher surface, though. It would be that much thicker, too, but it would still look right.

sandman 01-05-2007 08:37 PM

2 Attachment(s)
The trick is to cut the trailing edge to fit the cardstock (mainly the patterns in the SEMROC kit) Don't make the cardstock fit the trailing edge.

Does that make any sense at all??? :confused:

These could be a better pictures but I think you could get the idea. This is of my 4" LJ II.

My original is starting to show signs of wear after 10 flights. :o

I have a set of the 1/70th vacuform parts from Paul Graf so I can do a really detailed 1/70th version...someday when I have time... :rolleyes:

sandman 01-06-2007 12:47 AM

1 Attachment(s)
While looking through my "stuff" on my LJ II kit I came across some body wraps of the upper section of the LJ II. The Service Module area.

If anybody wants them I have redrawn the different rounds A-001 through A-004. I can post them if you looking to get a bit closer to scale and don't feel like a lot of masking and paint.

I also can scale down the detail lower pattern for placement of all the bumps, conduits and stuff on the bottom.

The one here is for round A-004

ghrocketman 01-06-2007 12:03 PM

Will this wrap fit the 1/70 scale (BT-70) if I print it at 100%?

sandman 01-06-2007 06:10 PM

Quote:
Originally Posted by ghrocketman
Will this wrap fit the 1/70 scale (BT-70) if I print it at 100%?


It should.

I make these drawings up in CAD and my program prints perfectly. But...

I print it to pdf to make the file since I can't attach CAD files here.

Hey...try it...it's only paper!

Does anybody know what round the SEMROC kit is? It can't be A-002, A-003 or A-004 'cause that uses the fin fairings. It has to be A-001.

In that case the wrap is too big vertically.

I'll redraw it correctly tomorrow...gotta go out tonight.

CPMcGraw 01-06-2007 06:18 PM

Quote:
Originally Posted by sandman
Does anybody know what round the SEMROC kit is? It can't be A-002, A-003 or A-004 'cause that uses the fin fairings. It has to be A-001.


I think someone has mentioned it before, maybe it was Carl, maybe even on the instruction cover, that this model represents A-001. This was the only LJ-II that had fixed fins; all of the others had the adjustable / power-boosted type, and their requisite power conduits along the body. A-001 didn't have these conduits.

sandman 01-06-2007 10:03 PM

2 Attachment(s)
Quote:
Originally Posted by CPMcGraw
I think someone has mentioned it before, maybe it was Carl, maybe even on the instruction cover, that this model represents A-001. This was the only LJ-II that had fixed fins; all of the others had the adjustable / power-boosted type, and their requisite power conduits along the body. A-001 didn't have these conduits.


Yes, it has to be A-001. Fixed fins and no fin fairings.

Maybe this will help.

I'll work on the upper wrap.

edit* I got the wrap done. NOTE!!! Round A-001 does NOT have RCS thrusters! That was probably Estes error if you are trying for scale points!


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