Saturn V from Arkansas [Estes #2157]

[afadeev]

I have seen several High powered rockets that use plywood centering rings. I have seen a few Medium power rockets that use plywood centers.

True.
Plywood is stronger, but also heavier. And more expensive.

For what it is, with all the parts, transitions, and wraps, Saturn V kit is a steal at either $90 MSRP, or $54 from ACsupply.com, and a few other places selling it at 40% discount.
At that price point, Estes had to keep costs down, and if cardboard rings are sufficient, they certainly would not be spending more money on plywood!

On the Estes Saturn V here, I was very surprised that the only rated motor is the D12-3. The model is so big, that I understand the need for a quick ejection charge. But I wondered why an E motor was NOT specified.

You may be misinterpreting the purpose of the advertised engine recommendation.
The suggested motor printed on an Estes box is never the largest, but rather, then smallest motor that is safe to fly. If it says D12 (not anymore, minimum recommended for new SatV kit is E12/E30), than means don't even think about launching it on C11!

Nothing is stopping you from going with bigger motors, but those cost more $$, so Estes leaves it up to you as to how much $$ you want to burn (pun intended) with each launch.

My guess is that Estes engineers were concerned about the stress an E motor would put on the frame (as designed). Consequently, I am also concerned about using an E motor, although I intend to use the Aerotech E15W-4.

Nope, nothing to worry about w.r.t. airframe integrity.
Recall that the thrust is transmitted to the airframe from the motor mount, through the centering rings (CRs). There are 3 of those on SatV, so you are transmitting the thrust to the main airframe through 3 circles of 3.9" diameter x 3.14 = 12.25" circumference (for each of 3). Assuming your glue fillets are 1/4" wide (at least) hold, the probability of tearing the 12.25" * 1/4 * 3 = 9.2 inch^2 worth of attachment surface area is just about nil.

You might be concerned with CR deflection under thrust, if so, consider gusseting them, or using stronger materials (additional CRs glued together, book cover, 1/8" plywood, etc).

I had some 1/4" plywood CRs lying around.
They are an overkill, but I used them anyway, mostly because I up-scaled my MMT to 29mm, and happened to have those CRs on hand (see pic below).

I apologize if I'm hijacking the thread here, but I am also building the exact same Saturn V kit. I converted the mount to a 5 engine cluster with a central 29 mm and four 24 mm outboards. I'm confident the thicker 4'' LOC tube can deal with the launch loads, but the cluster requires a considerable amount of nose weight for stability, on the order of 300 grams, which seems like it would be a lot for the upper section to either during launch or under chute. Did I over reach with the cluster, or have others used that much nose weight with success?

One of my MMT configurations will also be a 5-cluster: center 24mm, and 4 outboard 18mm.
The extra tubes (not glued yet) pushed the motor mount (MMT) assembly weight form 33g to 66.3g. Maybe make that +50g of extra mass in the aft part of the rocket when everything is done.

But, my heavy duty 29mm tube with 1/4" plywood CRs weights in at 138g (I over-built this a bit), thus my 5-engine cluster is still lighter than my I-motor ready 29mm MMT.

To keep stability at 1.0 caliber, I need 104g of ballast in the nose cone/command module (vs. 29g stock).

Your MMT may be a bit heavier, but I don't see why you would need 300g of ballast.



HTH,
a

 

[jmuck78]

One of my MMT configurations will also be a 5-cluster: center 24mm, and 4 outboard 18mm.
The extra tubes (not glued yet) pushed the motor mount (MMT) assembly weight form 33g to 66.3g. Maybe make that +50g of extra mass in the aft part of the rocket when everything is done.

But, my heavy duty 29mm tube with 1/4" plywood CRs weights in at 138g (I over-built this a bit), thus my 5-engine cluster is still lighter than my I-motor ready 29mm MMT.

To keep stability at 1.0 caliber, I need 104g of ballast in the nose cone/command module (vs. 29g stock).

Your MMT may be a bit heavier, but I don't see why you would need 300g of ballast.

View attachment 374084

HTH,
a

Afadeev, The 300 grams was based on the OR model with 4 D12s and a central E12 loaded in the motor mounts. Are you accounting for the motor weights when you calculate your nose weight requirement? The difference in nose weight may also just be due to the difference between a 29 mm / 24 mm cluster and a central 24 mm / 18 mm cluster. Note that my cluster motor mount tubes also don't extend the same length as the central 29 mm. Here's the OR snapshot just for information. The 1.17 caliber stability is with 300 grams of noseweight.

 

[Crawf56]

Adding a glue fillet to the top of the Main Tube.

 

[Crawf56]

And gluing the Third Stage insert. Even though I normally use CA and epoxies in my model building, on this project I decided to use wood glue.

 

[Crawf56]

And working on the LM/SM section. Note the weights to help keep parts flat.

 

[Crawf56]

By the way, I really like the look of the multi-engine Saturn V. There is plenty of room.

But multiple motors have to be positioned lower. On this design, the tip of the motor nozzle is about 3 inches up inside the Main Body Tube (which I found very surprising).

 

[afadeev]

By the way, I really like the look of the multi-engine Saturn V. There is plenty of room.

But multiple motors have to be positioned lower. On this design, the tip of the motor nozzle is about 3 inches up inside the Main Body Tube (which I found very surprising).

Funny you should bring this up - I was just thinking about this last night.
The engines are positioned somewhat unusually high in the airframe, but you can get away with that with one central motor that is unlikely to damage the circumference of the tube as it's centered ~1.5" from the walls.

One benefit from pushing the motors that far from the aft end is moving rocket's CG forward, reducing nose cone's ballast weight. Also, this leaves room to insert the stand that keeps rocket upright on the desk.

With a 5-engine cluster, the perimeter motors will be burning within 1/4" of the wall, and left unprotected, it will at least singe, if not burn the aft end of the rocket. I suppose one could protect the walls with a coating of epoxy, which might be enough if the perimeter motors only burn for a few seconds (for show). It might be good enough for my 18mm B6/C6-0 motors. But for 24/29mm clusters, this may be a bigger problem.

Afadeev, The 300 grams was based on the OR model with 4 D12s and a central E12 loaded in the motor mounts.

OR is usually right - go with that!

Are you accounting for the motor weights when you calculate your nose weight requirement? The difference in nose weight may also just be due to the difference between a 29 mm / 24 mm cluster and a central 24 mm / 18 mm cluster. Note that my cluster motor mount tubes also don't extend the same length as the central 29 mm.

You are right - I forgot how much heaver 24mm D12s are vs. B/C6's.
I am mostly burning perimeter motors for show, with either E30 (Estes) or F39 (AT) in the middle.

I can't really tell from the diagram - are you channeling outboard motors' ejection charges back into the central MMT, or just sealing perimeter motor mount tubes?

 

[jmuck78]

I can't really tell from the diagram - are you channeling outboard motors' ejection charges back into the central MMT, or just sealing perimeter motor mount tubes?

Sealing the perimeter motor mount tubes.

"But multiple motors have to be positioned lower. On this design, the tip of the motor nozzle is about 3 inches up inside the Main Body Tube (which I found very surprising)."

Yeah, I'm going to move the motors Aft enough that I can still use the stand, but not burn up the airframe. I didn't understand why the motor was so far forward. The stand has a length of tube that enables the stand to reach the motor mount. Only thing I could think of is that the CG requires the motors to be forward or else the kit would require much more nose weight.

 

[Crawf56]

Sealing the perimeter motor mount tubes.

"But multiple motors have to be positioned lower. On this design, the tip of the motor nozzle is about 3 inches up inside the Main Body Tube (which I found very surprising)."

Yeah, I'm going to move the motors Aft enough that I can still use the stand, but not burn up the airframe. I didn't understand why the motor was so far forward. The stand has a length of tube that enables the stand to reach the motor mount. Only thing I could think of is that the CG requires the motors to be forward or else the kit would require much more nose weight.

Another reason for the motor being so far in the Main Tube may be for "looks". It causes the smoke from the motor to be closer to the bottom of the rocket, giving the effect of multiple motors.

Kind of....

 

[Crawf56]

Little by little. Every once in a while, some small task drives you nuts. Trying to tie this string about did me in. Had to get the tweezers out.

 

[Crawf56]

Ok, get the knot on the right side.

 

[Crawf56]

More gluing. Get the centering rings in place. By the way, those rods are Duck Decoy weights I got at Walmart.

 

[Crawf56]

There have been several comments about engines on this thread. So, I emailed Estes questions about engines. Their response went something like this:

RECOMMENDED ENGINES (Defined)

1. In general, when Estes lists "Recommended Engines", these are the engines that should be used with the rocket. Sometimes one engine is listed, and sometimes several.
2. Engines smaller (less powerful) than the Recommended Engines should not be used.
3. The ability of a rocket to handle LARGER engines than the Recommended Engines varies greatly. Some rockets can easily handle larger engines. Rockets that are Scale, Oddroc, or Glider are more likely to have problems with more powerful engines.

ENGINES FOR SATURN V [#2157]

1. It was heavily recommended that I use E engines for the #2157 kit.
2. The Saturn V model (built per instructions, no additional structural support) was tested with an F engine, and did not survive.

So, looks like I will be saving my D12-3's for my Estes V-2. Thanks for the advice, guys.

 

[JJSR]

Crawf56
It's your kit build it your way,,,,
As you gain building experience you'll learn where things can be improved for how you want the rocket to perform.
Each person has their own ideas and none of them are wrong just different.
Here on TRF everyone likes to share their ideas,,, sometimes it gets confusing, but don't let that get in the way of YOUR building style.

OH, and don't forget we love lots of pictures

 

[Crawf56]

More work on the LM section.

 

[Crawf56]

"Houston, we have a problem....."

While assembling the Third Stage, I ran into some troubles. I had to quickly disassemble the section, and re-glue a centering ring. I had neglected an internal fillet.

Here, I have re-assembled the Lower Insert, with a better internal fillet:

 

[Crawf56]

Part of the problem was that:

1. I had put glue on the 3rd Stage Body Tube, and had let it sit a few minutes. Thin areas of the glue got tacky, and 'grabbed' the centering ring.
2. The opening for the centering ring did fit the tube, but it was tight. I probably should open it up some.

Note the glue residue on the tube.

 

[Crawf56]

Here is the glue I am using: Elmers Woodglue.

Generally, I use CA and epoxy glues for my large balsa RC aircraft. I thought I would use wood glue for this model, to give me more assembly time.

I am concerned about how well this wood glue is holding. I may go back a apply some CA to some of the joints.

EDIT: Not sure why I chose Elmers. I normally use Titebond wood glue.

 

[kuririn]

Here is the glue I am using: Elmers Woodglue.

Generally, I use CA and epoxy glues for my large balsa RC aircraft. I thought I would use wood glue for this model, to give me more assembly time.

I am concerned about how well this wood glue is holding. I may go back a apply some CA to some of the joints.

EDIT: Not sure why I chose Elmers. I normally use Titebond wood glue.

View attachment 374250

Aliphatic wood glue has a bond that is typically stronger than the materials (balsa, paper) that it bonds. So any yellow wood glue like Elmer's or Titebond is fine for wood, cardboard, porous materials. Not good for plastics or plastic to wood or cardboard.

 

[afadeev]

Here is the glue I am using: Elmers Woodglue.
Generally, I use CA and epoxy glues for my large balsa RC aircraft. I thought I would use wood glue for this model, to give me more assembly time.
I am concerned about how well this wood glue is holding. I may go back a apply some CA to some of the joints.
EDIT: Not sure why I chose Elmers. I normally use Titebond wood glue.

+1 on Titebond II, which has been tested to provide stronger wood-to-wood bonds than epoxy (link shared in some glue related thread on TRF).
However, both Titbond and Elmers have the nasty tendency that you've discovered already - they sometimes "grab" the components before you are done positioning them. So for attaching motor mounts, I only use 15-/30-minute epoxy that gives me enough time to prep everything without undue hurry, and then yet more time to re-adjust the desired MMT placement before the glue hardens.

The primary downside to Epoxy are the weight, the mess, and the undesirability of having it come into contact with the skin.

Afadeev, The 300 grams was based on the OR model with 4 D12s and a central E12 loaded in the motor mounts.

jmuck78, are you at all tempted to use decorative bell-housings as motor mount decorations?
I've seen a few pics of others trying that, but no feedback on whether or not they survived the heat, or impacts from landing (BT-101 is tail happy, and will likely come down on anything that is sticking out the back).

It seams like a silly cosmetic idea, but they do look good, and serve no other useful purpose.
I don't see my rockets sitting on the Estes stand anywhere, and all that stand has been goof for thus far is taking up space on my desk as a pen cup.

a

 

[jmuck78]

jmuck78, are you at all tempted to use decorative bell-housings as motor mount decorations?
I've seen a few pics of others trying that, but no feedback on whether or not they survived the heat, or impacts from landing (BT-101 is tail happy, and will likely come down on anything that is sticking out the back).

It seams like a silly cosmetic idea, but they do look good, and serve no other useful purpose.
I don't see my rockets sitting on the Estes stand anywhere, and all that stand has been goof for thus far is taking up space on my desk as a pen cup.

a

No, that thought hadn't occurred to me, but it sounds interesting. It seems like it would be difficult to keep the engine bells from melting from the central motor - and I would count on losing at least two engine bells on each landing. I thought I had seen a vendor who made metal engine bells somewhere - might have been custom aft motor retainers that look like engine bells.

Separate Question - I was trying to figure out if the Saturn V has enough base drag to allow some nose weight reduction, so I added in the aft nose cone / base drag simulator in OR (3 calibers long, one caliber in diameter), and OR does in fact show a substantial increase in stability margin. Top image is with the base drag simulator, bottom image is without. I understand that the base drag is only useful for short, stubby rockets - but I had also understood that adding in the base drag to a longer rocket would just not have any effect on stability, so this result was a bit puzzling.

 

[Crawf56]

Got the 3rd Stage sorted out.

 

[Crawf56]

Working on the Wraps. Using blue masking tape and Elmers All Purpose glue. Weights & clamps to hold surface flat.

I did not use wood glue because sometimes it weakens the paper when it is initially put on.

 

[jmuck78]

Working on the Wraps. Using blue masking tape and Elmers All Purpose glue. Weights & clamps to hold surface flat.

I did not use wood glue because sometimes it weakens the paper when it is initially put on.

View attachment 374318

View attachment 374319

Crawf,

One thing that wasn't clear from the instructions is whether the large end of the wrap is supposed to sit on and flush with the large part of the 3rd stage, or if the wrap is supposed to go over the large part of the third stage. The bond would be stronger if the wrap is able to go over the larger round part of the third stage, but I was unable to slide it over, and the wrap was too ovalled to sit flush with the edge. I have a small gap at the bottom of the wrap in some places, which I think I can fill in with putty, but the wrap will still have a slight oval shape to it.

The other consideration is that during launch, I didn't want the wrap to react all of the launch loads from the booster section into the third stage section. The instructions don't seem to indicate (unless I missed it) if the smaller LEM section is supposed to be glued in to the larger third stage tube, but either way, the larger third stage tube is only friction fit in to the booster, so any "lip" from the wrap is going to be sitting on the booster carrying the launch loads. I ended up inserting a coupler into the booster section that the upper stage can sit on during launch.

Thoughts?

 

[SecondRow]

Crawf,

The instructions don't seem to indicate (unless I missed it) if the smaller LEM section is supposed to be glued in to the larger third stage tube, but either way, the larger third stage tube is only friction fit in to the booster, so any "lip" from the wrap is going to be sitting on the booster carrying the launch loads.

FWIW, instruction 9 in the "Paint Rocket" section, page 12, calls for gluing the LEM into the 3rd stage. The instructions for this kit are not the best. I believe they are pulled from the old Centuri instructions, with some updates made. But not everything was updated. For example, note instruction 4 on the same page that says to cut out the masking guide for the service module. The kit does not have any masking guide.

In my view, that 3rd stage wrap is the most difficult part of the build to get a good fit. I could not get mine to lay well, either. You have to decide whether you want the top of the stage to fit well or the bottom. Either way is not ideal.

 

[afadeev]

One thing that wasn't clear from the instructions is whether the large end of the wrap is supposed to sit on and flush with the large part of the 3rd stage, or if the wrap is supposed to go over the large part of the third stage. The bond would be stronger if the wrap is able to go over the larger round part of the third stage, but I was unable to slide it over, and the wrap was too ovalled to sit flush with the edge. I have a small gap at the bottom of the wrap in some places, which I think I can fill in with putty, but the wrap will still have a slight oval shape to it.

Are you asking about conical paper shrouds, or plastic wraps?

I finagled my conical paper shroud (using word shroud not to confuse things with plastic wraps) to go OVER the edge of the larger diameter cylinder for maximum strength.
Plastic wraps end at the same point as the paper shroud.

The other consideration is that during launch, I didn't want the wrap to react all of the launch loads from the booster section into the third stage section. The instructions don't seem to indicate (unless I missed it) if the smaller LEM section is supposed to be glued in to the larger third stage tube, but either way, the larger third stage tube is only friction fit in to the booster, so any "lip" from the wrap is going to be sitting on the booster carrying the launch loads. I ended up inserting a coupler into the booster section that the upper stage can sit on during launch.

The acceleration forces should be transmitted from the main airframe (BT-101) to the forward end of the rocket through "lips" formed by conical paper shroud, which is further reinforced by the plastic wrap on top of it. The E12/E30 generate only 3.5-4 G of acceleration, so I would not worry too much about the strength of that joint.

Nothing below G-motors generates anywhere near 10 G's, so I would not worry about it, unless you are beefing up to fly on G/H/I motors.

a
P.S.: The entire rockets is single stage, so referring to 1st/2nd/3rd/LEM stage is a bit ambiguous.

 

[jmuck78]

Are you asking about conical paper shrouds, or plastic wraps?

The Paper Shroud. I attempted to get the shroud over the coupler, but the glue grabbed at the top of the shroud, and the paper had become "wet" by the glue, so moving the shroud = tearing the shroud.


The acceleration forces should be transmitted from the main airframe (BT-101) to the forward end of the rocket through "lips" formed by conical paper shroud, which is further reinforced by the plastic wrap on top of it. The E12/E30 generate only 3.5-4 G of acceleration, so I would not worry too much about the strength of that joint.

Nothing below G-motors generates anywhere near 10 G's, so I would not worry about it, unless you are beefing up to fly on G/H/I motors.

P.S.: The entire rockets is single stage, so referring to 1st/2nd/3rd/LEM stage is a bit ambiguous.

I realize that - I was attempting to use the same terminology in the instructions

 

[jd2cylman]

I'll second, SecondRow, on the link to Chris Michiellsen's build!! GOOD STUFF RIGHT THERE!

I'm fighting through my last year of my Master's Degree at the moment... an Estes Bull Pup build will take me a whole 3 months! LOL. (Read, write, go to class, repeat.... while longingly looking at a finless Bull Pup on the building board!!)

We'll see what I can do on that, Crawf56.Who KNOWS what model number I've got... tag says "1969"...box cover is different than yours, Crawf56, with the picture of a "new and improved" Lunar Lander on the upper right of the box.

Shooting 29mm motors WILL require 100 grams in the nose of this rocket, they say. Might have to get a different nose to use while going with a 24mm to 29mm adapter, and shooting 24mm motors.

CHOICES CHOICES!

Maybe a Skylab version for one of your motor choices?

 

[Crawf56]

REGARDING TERMS:

One aspect of the instructions that is somewhat confusing is that both the conical light cardboard and the plastic sections that go around the main tube (and other places) are referred to as "wraps".

Yes, this is a one-stage rocket. But Estes' instructions refer to different sections by the names used on the REAL Saturn V. To communicate clearly, I have tried use the terms in the instructions.

 

[Crawf56]

Crawf,

One thing that wasn't clear from the instructions is whether the large end of the wrap is supposed to sit on and flush with the large part of the 3rd stage, or if the wrap is supposed to go over the large part of the third stage. The bond would be stronger if the wrap is able to go over the larger round part of the third stage, but I was unable to slide it over, and the wrap was too ovalled to sit flush with the edge. I have a small gap at the bottom of the wrap in some places, which I think I can fill in with putty, but the wrap will still have a slight oval shape to it.

The other consideration is that during launch, I didn't want the wrap to react all of the launch loads from the booster section into the third stage section. The instructions don't seem to indicate (unless I missed it) if the smaller LEM section is supposed to be glued in to the larger third stage tube, but either way, the larger third stage tube is only friction fit in to the booster, so any "lip" from the wrap is going to be sitting on the booster carrying the launch loads. I ended up inserting a coupler into the booster section that the upper stage can sit on during launch.

Thoughts?

I think the main reasons for the conical paper wraps are:

1. To look like the real Saturn V.
2. To aid aerodynamics (like the real Saturn V).
3. To give some strengthening, which is possibly more of a vibrational dampening effect than straight structural.

I would prefer the conical cover/wrap on the 3rd Stage go out to the edge (of the centering ring) to aid aerodynamics. As an engineer, sometimes you have valid concerns; and sometimes, you are worrying about how many angels can stand on the head of a needle.

EDIT: In other words, sometimes I am not sure if I should worry about something, or not.