Custom Rockets SAM-X

[Chuck H]

I found this browsing my LHS and liked the looks and the fact that it was a two-stage. This will be my first two-stage rocket and my first build thread!

Here are the parts laid out. Also the first step is to add nose weight - the nose cone had to be opened in order to insert the clay.

 

[Chuck H]

Next were the engine tubes, booster tube spacer, and booster body tube. The engine tubes were easy enough (or so I thought). After I got all the tubes assembled, I discovered an error. I had glued the rings on the outside of the 5/8" mark, not the inside. This meant that the booster and sustainer would not fit together because the body tubes were impacting the rings. Oh well, the fix was to adjust the position of the engine tubes in order to allow the booster and sustainer to fit together. Because of this, the engine tube in the sustainer is recessed and the engine tube in the booster protrudes a bit.

 

[Chuck H]

Although the instructions didn't specify sanding the leading edges of the fins, I usually do anyway. I thought that a sharp edge would look best for this kit. I also sanded the upper body "decorative fins" to a sharp edge. They were then glued to the kit and filleting began. After I added the fillets and they dried (and shrank to nothing) I searched this forum for better techniques. I'll try using the Titebond Moulding and Trim glue next time if I can ever find it.

 

[Pem Tech]

Very nice...
What is your secret to keeping an even bevel on the fins?

 

[JAL3]

Very nice...
What is your secret to keeping an even bevel on the fins?

Inquiring minds DO want to know.

 

[mjennings]

Nice work Chuck, the Sam X is a good rocket, I always liked to put it up on a B6-0/B6-6 combo. On a calm day I've had the booster land with in feet of the pad and the sustainer not much further away. I've never put her up on a C6/C6 stack but that should really scoot. Hopefully I'll be able to fly her again soon, I would have never have found here were I flew in Florida.

 

[cobra1336]

Flew mine once and the booster did not seperate from the rocket. It did a burn thru. Second motor lit and burned thru the booster. To much tape and to tight. Repaired it and I still have it.

 

[Chuck H]

I like the camo scheme. Also, having never flown a two-stage, what exactly is the deal with the taping of the engines together? Is that standard procedure? How much tape?

 

[Chuck H]

Very nice...
What is your secret to keeping an even bevel on the fins?

First I just eyeballed it, then used the emery board to even it out. I guess a sanding block or even sandpaper on a flat surface will work too.

 

[Chuck H]

OK, time to paint this thing. But first, I noticed here on TRF a neat device that someone had built to assist in holding rockets while painting, taking pics, etc. (Chime in and take credit if it's your idea.) Anyway, take a spent engine casing for the size rocket you are building and insert an appropriate-sized diameter of wooden dowel. For "C" engines that's 1/2". I cut the 36" length in half and slathered some white glue on mine just to be safe. Voila! Now you can insert the engine into the engine mount and grip by the wooden dowel for painting, picture-taking, and simulated flights (zooming it around the room).

 

[Chuck H]

I decided to try and prime this with Kilz. I've seen John (JAL3) use this and was looking for a new can of sandable primer so I gave it a shot. Wow! It shoots like a fire extinguisher! But you get used to it and adjust accordingly. Once dry, it sanded nicely to a pretty smooth finish.

 

[Chuck H]

I didn't want to paint like the art provided with the kit, and since this was a Russian missile I searched the web for ideas. I decided on green with silver fins and a white nosecone. I had a nice Tamiya green in a jar so I chose to brush-paint it. Next I brush painted the fins with Testors aluminum and sprayed the nosecone gloss white. To reduce silvering of the decals, I painted Future in the spots where the decals would be placed.

 

[RangerStl]

That brush paint looks mighty good!

 

[Chuck H]

I sprayed on a clear dull coat, which didn't cover the gloss and flat the same causing a mottled appearance.
It also made the aluminum fins look a dull grey (of course:bangpan and caused part of the nose cone paint to lift and wrinkle.
That's OK because this is a mobile Russian missile that has been dragged around Siberia, getting dinged and touched up throughout its lifespan.

 

[mjennings]

Nice work, I really like the simplicity in your paint scheme it works very well, The rocket on a stick trick is older than dirt, because it works great with 18 mm's, It doesn't work so well with 24 mm engines unless you knock the nozzle out and run the dowel through that way. 24 mm do have a slight tapper, I have a small statistical sample that proves it.

On the tape, one wrap of cellophane / scotch tape around the two motors is what I use / read somewhere. It helps in the motor loading and motor ignition, by keeping the booster attached until the sustainer comes up to thrust and melts/breaks the tape, thus preventing the booster from separating and an ignition failure on the sustaining stage. How true the second part is may be up to debate since gap staged models don't have the tape and work just fine.

 

[cobra1336]

Chuck, nice job. Look at the beginner and education section on this forum.
There is a list of education material. The second estes educator talks about multi staging. My theory is the tape helps keep the motors close so the hot gases can ignite the second motor and it also acts as a friction fit for the motors at the same time. If I remember the Sam-X has no motor hook. Usually one or one and a half wraps of tape is fine.

 

[JAL3]

The idea that anyone is doing anything based on what I say is really frightening!!!!!

That said, I like you paint job. Its simple and clean.

Great job!

Be sure and post a flight report.

 

[Chuck H]

Here's the flight report: B6-0/C6-5, nice launch, separation at maybe 100', sustainer went OOS and then lost! I didn't see the ejection, chute - nothing. I also couldn't locate the booster at first and then spotted it about 20' feet from the pad.

So the reason that I am even posting this is I have rebuilt the sustainer. I figured since I had the booster I may as well. I used a Custom Rockets Fiesta to start with, and just cut my own fins. I'll also keep the streamer recovery, even though it will have added noseweight. I messed up on one of the fins, so i made an extra cut in all four fins to match.

 

[Chuck H]

Here's a pic of three fins on the rocket and the nosecone with noseweight added. The nosecone for the Fiesta had an open bottom and end cap, so the clay was a snap to get in there. I also noticed that the balsa I used was pretty soft, so I hardened with CA. Then I primed with Kilz.

 

[Solomoriah]

I have a SAM-X, but haven't launched it yet; I've saved an Estes A8-5 for the upper stage, and plan to use a Quest B6-0 (one of the old German ones) for the lower stage.

Oh, and here's something I do with all my just-painted rocket pictures:

I erase the stick.

 

[mjennings]

Chuck,
Sorry about the loss, you might want to redo the fins on the new sustainer. Your grain runs parallel to the tube, and not parallel to the leading edge. The fins will work as is but reorienting the grain will help prevent fin breakage. Compare our fin pictures in post 3 with those in post 19.

 

[Chuck H]

Chuck,
Sorry about the loss, you might want to redo the fins on the new sustainer. Your grain runs parallel to the tube, and not parallel to the leading edge.

Good point. If I'd done that I wouldn't have needed the CA hardener. Next time.

 

[Chuck H]

I erase the stick.

Thanks! Should have a SAM-X2 completed pic up tonight.

 

[Fred22]

Thanks! Should have a SAM-X2 completed pic up tonight.

Cool Keep up the good work I like the paint scheme as well.
Cheers
Fred

 

[Chuck H]

Got a chance to launch again on Saturday. Perfect launch, good separation, but second stage didn't light - lawn-darted; booster recovered OK. Not sure why, any ideas?

This is the second and last flight. I don't think I'll rebuild again, at least not anytime soon.

 

[shreadvector]

https://www.rocketreviews.com/reviews/all/cus_samx.shtml

Without reading the entire thread...is this a model that requires the motors to be taped together for sucessful upper stage ignition? If so, did you use cellophane tape or some other tape?

If not tape is recommended, then it either needs a looong stage coupler or vent holes. AND it needs an upper stage motor with a large diameter nozzle hole to allow the flaming bits to reach the upper stage motor propellant face. An Estes B6 or C6 has a very tine nozzle hole. The A8-5 is best and if they only made the B4-6 again it would be great as well.

 

[Solomoriah]

The SAM-X instructions call for a single wrap of cellophane tape, and specifically warn against using magic transparent tape. The engines are to be friction fitted with masking tape, also.

 

[Chuck H]

I used a single wrap of tape, tho it was magic transparent tape. I thought it was a tape issue and the force of the initial blow thru caused the engines to separate too soon to get the flame into the upper engine.

 

[luke strawwalker]

I like the camo scheme. Also, having never flown a two-stage, what exactly is the deal with the taping of the engines together? Is that standard procedure? How much tape?

The typical method of staging black-powder motors is to wrap a single wrap of cellophane tape around the butted-together motors. This holds the motors together for a split-second after the booster motor burns through the top of it's propellant grain, and gives the upperstage motor time to ignite. Once the upperstage motor lights, it blows the engines apart.

Typically on this type of rocket, the booster motor is taped to the sustainer (upperstage) motor and then the upperstage motor is friction-fitted in the upper stage, then the lower stage is slipped over the booster motor. The booster typically has a thrust block ring AT THE BOTTOM of the motor tube to prevent the booster motor casing from being kicked out the back of the lower stage while leaving the booster section itself still attached to the upperstage-- if that happened, the upperstage motor would burn through the lower stage motor tube, burning it up, while reducing the effective thrust of the upperstage to near-zero because of the Krushnik Effect. If that happens, usually your lower stage is burned to a cinder and your upperstage crashes due to the lost thrust of the upperstage motor leading to a low flight, and the long delay in the upperstage allowing the rocket to prang before popping the chute.

The other method of staging is 'gap staging' where the lower stage is much longer, sometimes up to a foot. The motors are NOT taped together, but the airframe of the booster is usually vented with a pair of holes in the side or centering rings to allow the pressurized gas to escape, to allow time for the upperstage to ignite without blowing the stages apart. If the lower stage is larger than the engine diameter, a stuffer tube is HIGHLY recommended to contain the heat/particles of the booster engine blow-through to ignite the upperstage motor, but it's usually vented up at the top near the upperstage motor to allow the gases to escape, so the gases don't blow the stages apart before the upperstage ignites.

Good luck and hope this helps! OL JR

 

[Solomoriah]

SAM-X doesn't have a rear thrust ring, and the instructions call for both engines to be friction fitted.