Estes Star Orbiter Lower Body Tube

[JLP1]

So what is the deal with the Star Orbiter lower body tubes? Flew my 3rd. one in a year Saturday, brand new first flight and look what happens. It came down nice and easy and landed in tall grass, didn't drag or nothing. When I go to inspect the rocket this is what I found. Always right behind the upper launch lug. I have only been using E16-6 Estes motors in these birds and all 3 have developed the same spiral breaks. The first one had 6 flights, the second had 3 flights, and this one was brand new first flight. Luv the rocket always built to the instructions. Now it's time to cut out the damaged section put a coupler in and go again.

 

[afadeev]

I own a Star Orbiter that had incurred similar damage, and got repaired by cutting the old tube, inserting a coupler over damaged area, then gluing and repainting over the repair area (took a while to get it perfect). I had attributed my damage to a tangled shoot landing over a packed dirt road, but could also have been one of the following:
- ejection charge over-pressurization?
- kink during initial high-G acceleration (long airframe would start bending right above upper launch nut)?

Root cause == flimsy paper tube.

 

[neil_w]

- ejection charge over-pressurization?
- kink during initial high-G acceleration (long airframe would start bending right above upper launch nut)?

I haven't run the numbers, but it seems like the acceleration from something like an E16 wouldn't really be that high. I'm more inclined to suspect the 29mm ejection charge, although it's just a guess.

Installing a piece of coupler above the motor mount would seem to be good insurance. However, I'm really not clear on where exactly the coupler needs to go to provide best protection: is there a rule of thumb as to where an ejection charge incurs the most stress and damage on the interior of the body?

Empirically, it would (obviously) be that spot below the lug, but I believe that is several inches in front of the motor mount. My default guess would have been right above the motor mount, which would not have covered that spot.

 

[Nytrunner]

I'd check that spot on my Star Orbiter, but that piece wasn't one of the recovered debris from the I205 flight

 

[DigBaddy]

Could the glue for the launch lug cause some shrinkage (pull-in) of the body tube there, making a slight kink and a weak point where the EC or acceleration can cause more damage?

 

[mbeels]

I haven't run the numbers, but it seems like the acceleration from something like an E16 wouldn't really be that high. I'm more inclined to suspect the 29mm ejection charge, although it's just a guess.

I think high acceleration isn't likely either. I've flown unreinforced Estes BT-55 with an F39 and it was fine.

I'd check that spot on my Star Orbiter, but that piece wasn't one of the recovered debris from the I205 flight

BWAP! Well that's another flight entirely! Did you add any reinforcement? Got any photos or video?

 

[afadeev]

Installing a piece of coupler above the motor mount would seem to be good insurance. However, I'm really not clear on where exactly the coupler needs to go to provide best protection: is there a rule of thumb as to where an ejection charge incurs the most stress and damage on the interior of the body?

Empirically, it would (obviously) be that spot below the lug, but I believe that is several inches in front of the motor mount. My default guess would have been right above the motor mount, which would not have covered that spot.

If I were to build a Star Orbiter again, I would reinforce the entire area above the motor mount all the way to the end of the lower tube (leaving room for the standard coupler).
One would need to source a reasonably long coupler tube, or glue a sequence of shorter ~3" couplers.
Definitely use epoxy, as Titebond II (or any other wood glue) is liable to "grab" the inserts before you had finished sliding them in place.

 

[JLP1]

So the end of the launch lug (as seen in the photo) is 12" from the end of the body. The motor tube is 8" long with the forward centering ring placed 1/2" from the end of the motor tube. So that places the bottom of the launch lug about 4-1/2" in front of the forward centering ring. The lug was tacked in place with thin CA and then a small fillet of slow drying epoxy was placed on each side of the lug. Looking at the decal sheets all three kits were manufactured in the 2018/2019 time frame if I remember correctly. What I wonder about is why Estes provides (2) different types of body tubes in this kit? One tube is white (lower body tube) and seems softer while the upper tube is brown and seems to have a firmer feel (at least to me). All (3) have suffered the same damage between the bottom of the upper lug and the forward ring. None suffered any real hard landings so it leads me to think that there is some force being applied during acceleration or ejection.

Now what I do do different is that I do attach the shock cord to the motor tube instead of using the z-fold. I also replace the shock rubber with a combination of elastic and Kevlar about 9 foot long.

 

[neil_w]

If I were to build a Star Orbiter again, I would reinforce the entire area above the motor mount all the way to the end of the lower tube (leaving room for the standard coupler).
One would need to source a reasonably long coupler tube, or glue a sequence of shorter ~3" couplers.

Could also do the old "cut a slice out of a piece of BT and use it as a coupler". Not as beefy as coupler stock, but still doubles the wall thickness of the tube.

Definitely use epoxy, as Titebond II (or any other wood glue) is liable to "grab" the inserts before you had finished sliding them in place.

LOL at the idea of trying to glue in a long piece of coupler with TBII.

So the end of the launch lug (as seen in the photo) is 12" from the end of the body. The motor tube is 8" long with the forward centering ring placed 1/2" from the end of the motor tube. So that places the bottom of the launch lug about 4-1/2" in front of the forward centering ring.

Ah, motor tube is longer than I realized, so it's really only the first 4" or so above the motor mount. That's not too bad.

 

[cjp]

Lets face it,since Estes has been made in China the quality has gone down hill.I'm working on their V2 and cutting the slots and ends off the tail cone really dulls your blade.I have notice the tubes seem to be thinner or just not the same quality as the ones Semroc has used in the past.And why include a rubber shock cord!!!!Well I feel better now that I had my rant.lol.Not trying to start a war on Estes sorry if anyone took that way.

 

[neil_w]

Lets face it,since Estes has been made in China the quality has gone down hill.

I would generally disagree. I don't think the tubes are any different than they've always been, and they've been using rubber shock cords since forever.

 

[teepot]

You can get 34" coupler stock from BMS. He also sells heavier weight BT's.

 

[kuririn]

Lets face it,since Estes has been made in China the quality has gone down hill

IIRC the tubes are made in the USA and packaged along with other Chinese made components in Guangdong.
Exception would be some of the E2X and RTA models with convolute tubes that are made in China. And those are pretty strong too.

I'm working on their V2 and cutting the slots and ends off the tail cone really dulls your blade.

Use a razor saw instead of a blade to cut the V2 plastic.

I have notice the tubes seem to be thinner or just not the same quality as the ones Semroc has used in the past.

Apples and oranges.
Semroc uses the old Centuri tube classification, their ST-7 and ST-9 tubes have always been thicker than their BT-20 and BT-50 counterparts. Nearly twice as thick. Been that way for decades.

.And why include a rubber shock cord!!!!

Economics.

 

[afadeev]

Lets face it, since Estes has been made in China the quality has gone down hill.

I would not blame anything on China.
I'm sure both US, China (and countries in-between) make thicker and thinner, higher and lower quality paper tubes. Estes just chooses to source what it does based on price, and supply chain reliability.

I've thrown out plenty of recovery gear supplies from Estes, Semroc, DrZooch, NCR, PML, and Quest (probably others too).
It takes time and practice to develop your own preferences based on experience, and by far, my replacements are always more durable, longer lasting, and more expensive. But that's just they way I like.

I strongly suspect 99% of the flyers would refrain from paying more for the motor retainer than the kit itself, so I am under no illusion that Estes would ever adopt my preferences. Which is just fine with me.

YMMV,
a

 

[Back_at_it]

I've not had that happen on mine yet but I've only flown it a few times. Most flights have been on E9's with one on the AT E30-7.

Since you're going to need to cut the rocket open anyway, might be worth the time to pick up some lengths of couplers from BMS and sleeve the entire lower tube.

 

[JLP1]

Well I didn't want to start a debate over the quality of the Estes kits. I just wanted to bring it to the attention of anybody who may wish to build the kit and might want to take some added precautions to prevent the failure. I just thought it was unusual for the kits to have the same type of failure in the same area of the body tube. First time ok that was weird, second time ok that's concerning, third time ok what am I doing wrong. The rocket is about 44" long the upper launch lug is 12" from the bottom should it be higher up on the body?

Some Questions To Ask:

1. With the lug being so low on the tube is there more twisting and torqueing taking place between the lug and the first centering ring?

2. With the shock cord being attached at the motor mount in the lower body tube instead of being up high with the z-fold cause undue flexing of the tube right above the first centering ring ? I use a 9' cord made up 1/4" elastic cord and Kevlar.

3. I use 3 to 4 sheets of wadding with a little dog barf to protect the chute, I never pack it very tight and the chute is 18" and fits the tube very well and never packs tight still could there be overpressure?

4. None of the rockets have ever landed really hard causing excessive body flex that I know of. My alt 3 usually shows a decent rate of 10 to 12 fps which I assume to be accurate.

My first one which is now retired due to excessive damage was flown on F15-8 Estes motors for the first couple of launches with no damage I just scale back to E16's in order to control how high they flew in respect to our field conditions.

My second one has only flown on E's after it was damaged I cut a 1-1/2" section of the body tube out installed a coupler and glued it back together it has now flown 3 more times with no more damage.

My 3rd and newest one has flown once on an E16 and it was damaged. I'm still working on a repair plan.

In all of these the tears have never been across the body tube they have always been right along the spirals.

Like I said food for thought not bashing

 

[kuririn]

In all of these the tears have never been across the body tube they have always been right along the spirals.

The spirals are the seams between two strips of kraft paper which make up the tube. In other words the weakest area of the tube.
Here is an interesting article regarding aeroelasticity of super rocs (long, slender rockets)
The first picture of one in flight is telling.
Avoiding_the_Bends.pdf (nar.org)

 

[JLP1]

Yep I agree Kuririn I think the thickness of the paper at the spiral bottom is about half of the overall thickness of the tube wall. Might be a little thicker than half but not much. Excellent article

 

[Ez2cDave]

I would not blame anything on China.

I'm sure both US, China (and countries in-between) make thicker and thinner, higher and lower quality paper tubes. Estes just chooses to source what it does based on price, and supply chain reliability.

The strength of the current "white" Estes tubes is inferior to the original "brown" Estes tubes of the 1970's - ???? ( Whenever Estes switched over ).

This is VERY apparent, particularly when comparing a "vintage" BT-55 to a "current" BT-55.

Dave F.

 

[Back_at_it]

Well I didn't want to start a debate over the quality of the Estes kits. I just wanted to bring it to the attention of anybody who may wish to build the kit and might want to take some added precautions to prevent the failure. I just thought it was unusual for the kits to have the same type of failure in the same area of the body tube. First time ok that was weird, second time ok that's concerning, third time ok what am I doing wrong. The rocket is about 44" long the upper launch lug is 12" from the bottom should it be higher up on the body?

Some Questions To Ask:

1. With the lug being so low on the tube is there more twisting and torqueing taking place between the lug and the first centering ring?

2. With the shock cord being attached at the motor mount in the lower body tube instead of being up high with the z-fold cause undue flexing of the tube right above the first centering ring ? I use a 9' cord made up 1/4" elastic cord and Kevlar.

3. I use 3 to 4 sheets of wadding with a little dog barf to protect the chute, I never pack it very tight and the chute is 18" and fits the tube very well and never packs tight still could there be overpressure?

4. None of the rockets have ever landed really hard causing excessive body flex that I know of. My alt 3 usually shows a decent rate of 10 to 12 fps which I assume to be accurate.

My first one which is now retired due to excessive damage was flown on F15-8 Estes motors for the first couple of launches with no damage I just scale back to E16's in order to control how high they flew in respect to our field conditions.

My second one has only flown on E's after it was damaged I cut a 1-1/2" section of the body tube out installed a coupler and glued it back together it has now flown 3 more times with no more damage.

My 3rd and newest one has flown once on an E16 and it was damaged. I'm still working on a repair plan.

In all of these the tears have never been across the body tube they have always been right along the spirals.

Like I said food for thought not bashing

1 - Unlikely that excessive twisting above the launch lug is causing this. That being said, there is no reason why you couldn't move the upper lug forward a few inches. Mine has the upper lug mounted to at the split between the upper and lower tubes.

2 - Again, Unlikely. Most of us mount the shock cord to the upper centering ring. I would think that the paper centering rings would fail and let go before there was enough stress on the body to cause this type of failure.

3 - This could be an issue with over pressure. Odds are that your wadding and dog barf are not making down past the coupler so it would be the lower section of the tube that would be under pressure during ejection. I have seen similar issues but it was only when someone over packed the chute, nose cone too tight or someone under sized the holes in a baffle.

4 - Of all of the points listed, this is the most likely. Some years back I had an Estes Cobra 1500 that kept bending very similar to what you have happening about 1/3 the way up the body tube. I would fly it an if it came down on anything but soft fluffy tall grass it would bend. I'd repair it and the next flight it would do the same this just above or below the previous repair. I finally replaced the entire lower tube and put a bunch of couplers in there to strengthen it. At the time I didn't know that full length couplers were available.

I ran into the same issue about a year ago when I built a mini mean machine. Of course this was streamer recovery with an 18mm mount but same exact issue. I ended up cutting the rocket just below the coupler and shoving a full length coupler in the lower section. A little filler and some glue and it never happened again.

Generally failures appear at the spirals as those are the weakest points of the tube so it's no surprise that this is where you are seeing them. Get yourself some full length couplers from BMS and call it a day.

 

[Nytrunner]

BWAP! Well that's another flight entirely! Did you add any reinforcement? Got any photos or video?

Report at link. Sad Day, but I was kinda asking for it

https://www.rocketryforum.com/threads/what-did-you-do-rocket-wise-today.48649/page-1012#post-2113501

 

[mbeels]

Report at link. Sad Day, but I was kinda asking for it

https://www.rocketryforum.com/threads/what-did-you-do-rocket-wise-today.48649/page-1012#post-2113501

Oh wow, what a flight. If yours survived for 3 seconds, it sounds like it could have made it past motor burnout. What was the simulation altitude and max velocity?

 

[Art Upton]

Any have damage using regular or Mini Rail Buttons? My Star Orbiters use Buttons, not lugs and I have not seen this; opinions?

 

[JLP1]

All 3 of mine use the launch lugs, all 3 had the damage right below the upper lug.

 

[kuririn]

The tube wants to bend somewhere along the length of the launch lug but the lug is acting as a stiffening rib so the bend occurs just aft of the lug.
Easiest solution as mentioned is to glue a coupler in that section.
Alternatively if you don't want to cut the tube you can glue ribs along the length of that section.

 

[heada]

Do you get the same damage when converting it to DD?

 

[Philip Tiberius D.]

I’ve got a Star Orbiter with the Vander-Burn upgrades... now I’m kinda worried to fly her... really sweet Black & Gold paint job. Sounds like this bird is a candidate for glassing or just an outright fiberglass build.

 

[smstachwick]

I just got back from flying my own Star Orbiter over the weekend. 8 flights, 2 each on E16-4s, E16-6s, F15-4s, and F15-6s. Same damage identified as I’m unpacking, and I immediately thought of this thread.

I’m not sure exactly after which flight it first appeared, I was mainly checking for airworthiness so it could fly again.

I too am puzzled as to the cause, and unwilling to take the thing apart to put couplers in, as the thing is built with very strong 24-hour epoxy. Putting it back together would be a pain.

I wouldn’t say any of the landings were particularly hard, but I do recall a few of them coming down and landing directly on the screw-on motor retention cap with what looked like a solid BONK!

Still, a very solid and reliable bird overall, far better than my other rockets that flew that day (full flight report coming soon). It flies so straight you’d think there’s some kind of onboard active guidance, there is absolutely ZERO roll.

 

[Philip Tiberius D.]

Guess she’s a candidate for a new build with reinforced booster… good thing winter is approaching. Perhaps the LOC Weasel….

 

[JLP1]

On mine I made the repairs by removing the damaged section of the body tube and installing a coupler and a new section of BT to keep the overall length correct. Also I stopped flying them with "F" motors and use only E16-6's now. So far nine flights on the two newest ones and no more damage. They still fly straight as arrows and they get decent height so I'm happy