Saturn 1B - 1/23 Upscale

markkoelsch said:

You could get some 1/8" thick nonexistent honeycomb core material. Laminate a layer around the tube, then a layer of two of glass or carbon and you are there.

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Mark - Thanks.

If it exists, I'll certainly look into it.:smile:

markkoelsch said:

You could get some 1/8" thick nonexistent honeycomb core material. Laminate a layer around the tube, then a layer of two of glass or carbon and you are there.

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I think this might be what we're talking about....this comes in .125 thick rolled mat which I believe is 1/8 inch thick....and Wow, ONLY $100 for the smallest size roll.

Thanks, but I think I'll go with balsa sheet, and put in the extra labor.
https://www.acpsales.com/Over-Expanded-Cell-Aramid-Honeycomb.html

Got the big roll of CF from Applied Vehicle Technology, one of the suppliers one of you guys mentioned.
https://www.avtcomposites.com/cgi-bin/commerce.cgi?preadd=action&key=2X2TWILL
2X2 Twill Carbon Fiber
Came on rolls in the width I wanted, making layup on the larger airframe component easier.

I went looking for .005 thick mylar for the mandrel barrier for the CF layup, found that at Hobby Lobby.
Trade name is "Dura Lar" near the art and frame section.
The larger 36 "wide roll was only .003 thick so I had to settle for the smaller 20" wide roll.

MaxQ said:

I think this might be what we're talking about....this comes in .125 thick rolled mat which I believe is 1/8 inch thick....and Wow, ONLY $100 for the smallest size roll.

Thanks, but I think I'll go with balsa sheet, and put in the extra labor.
https://www.acpsales.com/Over-Expanded-Cell-Aramid-Honeycomb.html

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This is an area of interest to me. RC guys use rohacell structural foam, goes down to 1mm.

dhbarr said:

This is an area of interest to me. RC guys use rohacell structural foam, goes down to 1mm.

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Yes, I' did a brief search for rohacell.
But I've sheeted so many balsa covered foam wings I figured that method might go quicker rather than wait for a delivery.

I could use some rohacel for a Sagitta 900 build -(that darn spar box).
Any good sources you like for rohacell?

Using the dimensions from the scale plans, the body tube for the 3X upscale Apollo service module at a scale of 1/23 measures 7.66 inches long by 6.68 inches wide.

Best thing I could come up with is a 6 & 5/16 inch (6.3125 inch)) diameter PVC section of sewer pipe.
Weighs a ton. But sturdy.
Should make an acceptable mandrel to roll a body tube.
Will require something like an additional .3675 inches added to match the 3X upscale Command Module shroud (rather than playing with the shroud to make fit- which I don't want to mess with).

That would be roughly .184 inches added per side.
I have some flexible 1/8 inch balsa sheet that I'm going to attempt to wrap around the tube / mandrel once the mylar is on.

The rest of the width I hope to take up with CF and FG wrap...maybe.
First I cleaned off the tube with soap and water, then alcohol to remove any residue.
Then I measured and marked off the length of the SM and left some overlap/gap at the front end.
The mylar barrier comes next.

Wrapped the .005 inch thick mylar with an excess 1/4 inch overlap lengthwise and then sealed the joint with scotch tape, lengthwise.

One of the most important things to keep in mind rolling a tube is to make sure no epoxy gets between the mylar barrier and the surface of the mandrel, that would make pulling the cured glassed tube off the mandrel a lot of fun (not).
I'm going to wrap the mandrel with balsa sheet first to add to the overall width of the tube, but I want to make sure excess epoxy doesn't find its way under the mylar after this starts getting messy.

I left an extra 1/4 inch of overall length with excess mylar around the front end to allow application of a narrow wrap of painter's tape folded over to inside of the tube to make a solid barrier to keep epoxy out.
Tape will be applied on the back end - sealing the gap under the mylar there as well

I wanted to determine how much balsa sheet I was going to need so I wrapped a long sheet of paper around the mandrel and marked off start stop lines to measure the total circumference around the mandrel plus mylar.
This will be guide for cutting the balsa sheets.

Time to cut balsa sheeting.
Most of you guys that have sheeted wing cores for RC airplanes know the procedures.
Get the sharpest blade you can find and cut precisely to butt joint the sheets together.

I hand picked the lightest and most flexible 1/8" x 4" x 36 " at the local hobby store.

Cut the 4" wide balsa sheets to the correct length (7.66 inches), and laid them along the circumference as I went.
When you get to the end you measure what ever is left to cover - and cut the last balsa sheet as close as you can to close the gap of the circumference.

I've had some luck wetting out balsa strip with hot water and bending around body tubes.
Gluing the ends with CA and shooting some CA accelerator worked well.
We'll see how wrapping the sheets works out next.

MaxQ said:

Yes, I' did a brief search for rohacell.
But I've sheeted so many balsa covered foam wings I figured that method might go quicker rather than wait for a delivery.

I could use some rohacel for a Sagitta 900 build -(that darn spar box).
Any good sources you like for rohacell?

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I hear clarasonic is the way to go, but haven't tried yet.

dhbarr said:

I hear clarasonic is the way to go, but haven't tried yet.

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LOL I don't have surface treatment issues, not yet anyway.:lol:
Now, Back to our regularly schedule program.

As a foundation on which to lay the balsa sheeting, decided to use a layer of poster board.
This is the kind that has a slick shiny side, which is laid against the mylar.
That will be the inside of the BT when it gets pulled.
Hope that helps pull the tube off when done.

Probably will have to rough up the surface where I glue anything to it.

MaxQ said:

LOL I don't have surface treatment issues, not yet anyway.:lol:
Now, Back to our regularly schedule program.

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clar_A_sonic

You are wrapping balsa around the paper tubes? If so, is this for strength?

dhbarr said:

clar_A_sonic

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Ohhhh - THAT Clarasonic !
Thanks Man.

https://www.clarasonic.com/

aerostadt said:

You are wrapping balsa around the paper tubes? If so, is this for strength?

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Not exactly.
When I started this project over in the scale section, I was pondering how to arrive at a feasible scale for this thing.
I based the overall scale on the materials available for the most components/parts I would need to locate,- off the shelf if at all possible.
These would be the eight tubes of the fin can part.
I was not thrilled about rolling those eight tank tubes, and my commercial choices were 2.6 inch, 3 inch and 4 inch in the common commercially available tubes.
The four inch tubes would make this thing a little too big.
All of the commercially available tubes were a bit on the heavy side as well. Not good in the aft end as George pointed out (more nose weight would be required).

I settled on a very lightweight tube at 3 iches dia. I was able to get all eight and some extras locally.

While I had the eight tubes and the main airframe handled, this did is leave me in the predicament of setting the scale that made the last component - the service module tube - "off scale" to any commercially availble tube.
(Check out post #12 - explains what I was dealing with).

So, now the answer to your question.

Keeping a consistent scale set the service module at 6.68 inches dia.
I did locate a PVC pipe that was close, but not quite. It was a tad short in width.

So after discussion here - one idea was to use balsa sheeting to make up the shortfall in diameter - then glass over that (thanks for the suggestion Rich H. - the idea works for me - I've done a lot of balsa sheeting on sailplane wings w/CF).

Extra strength - maybe that is an unexpected outcome, but what I really needed to do is add extra width to the tube/mandrel dia. - to hold true scale and make it possible to use the command module shroud 'as is" w/o changing it - after enlarging it 3 X
The carbon fiber twill layup going over the balsa is where most of the strength will come from - if I do that correctly, of course.

This afternoon was rainy and humid, I figured that couldn't hurt if I wanted to wrap some balsa sheet.
I thought about what method to use...decided to do a test with balsa sheet, wetted out with hot water to make it flexible, and Titebond II brushed on.

I dried off the damp balsa sheet, brushed on the Tight Bond II and laid it on the paper layer on the mandrel.
Not exactly good results.

There was still enough moisture in the balsa and the Titebond II to start buckling the paper layer underneath.
I didn't like the look of that, I worked too hard to get a nice tight, even, fit around the mandrel and mylar and I don't want to wait for it to dry to see if it goes away.
Scrapped that attempt.

What I did next is break out the Pacer Z-Poxy finishing resin which I have tons of and lots of experience with.
It is good for laminating wood and foam and works well over paper, sands easy, has a 20 -30 minute working time, which is good for repositioning these sheets to get them even.
Three hour cure time might allow another lay up this evening.

Had to work fast, and getting the rubber bands on this thing was a bit of struggle with only two hands. We'll see how this works out.

I didn't put enough of a bevel on the lengthwise butt joints, so I can already see a high point in the joint that will need to be sanded down.

All balsa sections now laminated on the service module mandrel, rubber bands holding nicely while waiting to cure.
Looks like the balsa wrap will close the gap around the service module, bringing the width of the service module body tube close to proper scale width - and with a CF/FG wrap, I'm certain it will get there.

Here's a shot of the components to date.

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The balsa sheeting came out ok.
Needs a little filler in places.

Looks like the 1/8 balsa closed the width gap.

Reference photos show a band of some sort at the service module /command module joint, so I think that would take care of any issues if it goes out of round later.

Ok, file this under "obsessive".

While waiting for the sheeting on the service module to cure, I went back to the LES tower and was going to add the internal "V" struts near the top.
Unfortunately, the thought of putting a flat structural ply ring as with the Semroc kits just didn't seem right, given the reference pictures, like the one in post #27.
There is a round shaped ring where the V struts converge from the top and bottom.

I've been on the hunt for over a week for a wooden or plastic ring, about the same size as the one shown in the picture.
We've probably all seen a million of these things in plastic in various places and never give it a second thought...on pull toys, old fashioned roll up window blinds, you name it.
Just when you want one it never fails. Can't find one.

I went down endless aisles at AC Moores, Hobby Lobby, Lowes, Home Depot looking to find a plastic ring...everywhere from key section to electrical to misc. hardware.
You know those threads that we've all read here on TRF before ..."You know you are a rocket junkie when you stroll through store aisles and everything begins to look like possible rocket parts...?

Well I was in that frame of mind when I kind of stumbled on to this little thing in the electrical section called a "3/4 inch PVC box adapter".
A check on the dimension and a go at it with a jewelers file seemed to indicate I could modify the edges of this thing.

Didn't take too long to file a radius the front, then razor saw through it to free the front end - to make a ring.

I think this thing will begin to take shape easy enough and get on with the tower build, - not that anyone will see it from launching distance.
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About 30 minutes later I was getting a round ring.
Just needs some fine sandpaper.........

Tower will get some epoxy on the joints before primer and sanding.
Apogee body tube for the LES rocket body comparison - need to start thinking about materials for a skirt and nose cone fabrication.

that tower looks fantastic!!

MaxQ said:

Tower will get some epoxy on the joints before primer and sanding.
Apogee body tube for the LES rocket body comparison - need to start thinking about materials for a skirt and nose cone fabrication.

View attachment 292562

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NJRick said:

that tower looks fantastic!!

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Thanks. Went a little faster than the last one I did for the Apollo LJ II ...smaller scale helped I guess.
Of course it was kind of like revisiting the previous build, just smaller.
Had to redo one of the V struts as it just didn't reach the vertical parts, was too short. No matter how precise you cut the pieces there is always some fiddly adjustments to do to get things to line up and attach.

I'm always impressed how solid this thing is when it is done.
Guess those NASA/North American design guys figured out how to make this thing structurally sound, even the little model of it feels very strong.

LES skirt and nose cone will take time as they are scratch builds.

Command Module will take some time as there will need to be a lead weight storage area transitioning from the interior of the service module thru the capsule...and the whole thing has to accommodate recovery system attachment points.

Decided to try my hand at CF layup this evening.
Service module mandrel is a short little tube so I can practice the technique on this smaller component before moving onto the fin can and larger airframe.

Set up the mandrel on supports with the precut CF laid out underneath, then mixed up a batch Z-Poxy finishing resin.
As they say, always mix more than you need because having to mix more while you're trying to do an even layup is a big hassle.

Brushing on the resin and rolling the CF up onto the mandrel as you go is a quick and handy way to do this.
Poking the CF with the chip brush helps get the CF wetted out and remove air bubbles underneath.
I wish I had set up better lighting, the black surface makes it difficult to determine how wetted out CF is.

I had some peel ply and had pre cut one layer with an 2 inch overlap.
This stuff turns grey as it wets out, so it very easy to read.
This stuff not only imparts a nicer finished surface but as it darkens will show the bubbles and gaps effectively.
I couldn't completely get rid of air pocket in a seam in the balsa sheeting, you can see the white line/seam

CF wrap: CF wetted out: Peel Ply Wrap:

The service module part pulled off the mandrel with no problem, that was a relief.
There was a lot of overhanging CF that had cured rock solid and had to be cut off with a hack saw.
Next time I'll try and do a better job on that.

Cutting and sanding is best done outside or with a shop vac handy, this is stiff nasty stuff and will splinter.
The part came out remarkably light weight.

The peel ply imparted a very nice fine mesh pattern over the heavy twill CF weave.
As you can see, there were some small air pockets and bubbles along the balsa seams that just did not wet out during the layup process, so they will need work.
A bit of delamination in one spot on the end (see first picture near my left thumb), but overall I was happy with my first go at CF layup.
Disappointed with the air bubbles in vertical seams along the balsa sheeting - I used wood filler on the tiny gaps in the seams but should've sealed them with epoxy before layup.
Since this will be a painted part I won't be trying to preserve the carbon fiber appearance in the final process - so any filler will do, rather than epoxy or clear coating.

I enlarged the service module wrap using George's scale drawing to see where the details will need to be applied on the CF tube.
Hopefully with adjustment, some of the detailed panel lines on the wrap will coalesce with the seams in the CF.

Its coming along nicely MaxQ.

rharshberger said:

Its coming along nicely MaxQ.

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Thanks! Congrats on that Level 3 Cherokee D flight, looked great from here.

I did a shopping trip to West Marine supply at lunchtime today - just replenished my supply of West Systems resin and hardner.
Looking over the main airframe components this evening and considering the next steps.

The 11.75 inch diameter sonotube is just right to do a fin can ring CF wrap to proper scale dimension, but if I hold that at 11.75 inches I have to decide how to reduce the diameter for the main airframe to 11.2 inches.

I'd rather cheat a little and do the main airfame at 11.75 inches dia. (instead of 11.2 inches) and hope no one notices it is slightly oversize....and in turn, enlarge the fin ring diameter proportionally, since there is less of that component (fin can ring) to deal with.

Decision time.

The sonotube would make a CF airframe 11.75 inches in dia. but the actual scaled airframe that fits over the eight tank tubes is more like 11.2 inches in dia.
That is a difference of .55 inches in width....maybe that would not be that noticeable on a airframe width of 11.75 inches.......about .275 inches too large per side, - or 1/4" per side.

Option A. One thought is to wrap the CF around the 11.75 inch sonotube, cure it then, cut out a strip lengthwise or longitudinally - and close it back up with a ribbon of CF or FG to reduce the BT diameter down to 11.2 inches.
Frankly, I don't like that idea too much, particularly if it reduces the airframe strength.

Option B. Keep the main airframe at 11.75 inches dia., and hope the oversize isn't very noticeable. This will require that I widen the shroud transition that attaches from the main airframe to the service module part in front to accommodate the sligthtly wider airframe.

Which Option should I do...A or B ?