New Semroc Blue Bird Zero

[Solomoriah]

So one of my 4-H kids ordered the BBZ from erockets.biz. It's the first Semroc kit I've seen since Semroc sold, and overall I'm fairly impressed.

Just one thing stood out as an issue: The engine tube is supposed to be a BT-50J, 2.75" long, but the one in the kit is much longer. I forgot to measure it, but it's either a 9" piece or the 7" (or so) main tube for an Alpha.

This is an issue because the kit does not include a thrust ring installation tool (i.e. fake engine casing) to push the ring into place. The instructions are still the original Semroc materials, and so do not explain what to do; for a Skill Level 1 kit, I think that's a mistake. Either the instructions should be changed AND the installation tool included, or the correct tube should have been in the bag.

We passed on that part of the construction; Clayton (the kid of whom I write) assembled the conversion mount, tied the shock cord to the coupler and assembled the main airframe. We'll get together next week to finish it up. Since I had time to do it, I did a simulation and concluded that it should be stable and should fly rather well on an E9-6, so I'm going to swap him parts from my stockpile to build it that way.

If it was his Mom or Dad helping him, and it was a first or second rocket (it's actually his third, but still), they'd have been in for some frustration. This is a bad showing, in my opinion, for erockets.

[Rich Holmes]

I bought one of those at NARCON but haven't opened it up yet. I'll check (probably tomorrow) and see if mine is the same.

[LeeR]

I'll typically use a spent engine casing. How about using one, assuming you have one on hand?

The other thought, although a bit of a nuisance, is to go to Home Depot or Lowes, and buy a dowel that fits well. The big advantage to a dowel is that you can mark it more D or E engines, and you'll have a painting wand when it comes time to paint the rocket.

I'm sure eRockets will get things fixed. I'm sure taking over the business and trying to get everything running smoothly is a daunting task, especially the part of the business to cut body tubes to length, and cut nose cones for the hundreds of styles that were available.

[Solomoriah]

I would usually use a spent casing myself. I was at the kid's house, though, and unlike me he does not have a bucket full of spent casings. As I said, it's not a problem at all for me, but it would be if he were a first-time builder.

I did err, however, in that it is a Skill Level 2 rocket, so my first-time builder comment is off base. I assume that's because of the second set of fins; it still seems pretty simple to me, though.

[Sheryl@Semroc]

I'm sure eRockets will get things fixed. I'm sure taking over the business and trying to get everything running smoothly is a daunting task, especially the part of the business to cut body tubes to length, and cut nose cones for the hundreds of styles that were available.

Thank you Lee. Randy has really done a fantastic job of getting Semroc up and running. I know from experience, it is so easy to put the wrong tube or no tube at all in the bag when kitting. Have cut open a few kits to take out wrong tubes or put in something I forgot to put in. I caught most before the kits went out the door but most happened our first year of starting Semroc.

[Solomoriah]

I guess I was just spoiled. You and Carl were so very, very good at getting things right.

[Vanel]

I guess I was just spoiled. You and Carl were so very, very good at getting things right.

Wholeheartedly agree! Miss the old Semroc!

[Rich Holmes]

I checked my kit which I bought in February and it too has a 9" piece of BT-50 for the motor mount. The instructions show and list a BT-50J tube (2.75"). So this isn't an isolated error.

[Chas Russell]

Until Randy Boadway or one of his reps comments on the longer motor tube, I can only speculate that he introduced the longer tube as a stuffer to aid in pressuring the main tube. He either has not had a chance to update the instruction and used ones that were already printed. If so, it would not have hurt to put in an instruction correction sheet.

Sheryl and Carl worked very hard to make SEMROC a great company that will live in our memories. Randy has had the company for a short time. Give him a chance to excel.

Chas

[astronwolf]

Until Randy Boadway or one of his reps comments on the longer motor tube, I can only speculate that he introduced the longer tube as a stuffer to aid in pressuring the main tube.
Agree with this.... if anything, the longer MMT is an upgrade. I usually opt to upgrade short Estes MMTs myself. Too bad that the detail didn't make it to the instruction sheet. Think of it as an engineering challenge.

[RocketRohde]

Randy has been made aware of this and he stated he pulled the remaining stock to verify parts.

[Doug Sams]

Agree with this.... if anything, the longer MMT is an upgrade. I usually opt to upgrade short Estes MMTs myself. Too bad that the detail didn't make it to the instruction sheet. Think of it as an engineering challenge.I mostly agree, altho (IMO) a BT-55 doesn't really need much stuffer - my Cherokee D doesn't have one.

That said, I'd be inclined to cut the long motor tube down just a bit. At 9", it's a tad long - I might like a bit more space for recovery system.

Everybody on this forum ought to be able to cut a few inches off to make it fit better. Even if the cut is uneven, if it's at the forward end, it's a don't-care. That is, this ought to be a simple work-around for most experienced modelers. But I can see it causing some issues with youngsters such as Sol's 4-H'ers.

Doug

.

[Solomoriah]

It's awkward, doing the 4-H thing. Technically, they expect the kids to move up a skill level in the second year, but where I built half a dozen rockets in my first year, they're building a couple each year. I think you need more practice before moving up.

That said... the BBZ has what, a 3' airframe? How much room do we need for the recovery system??? I was actually thinking, if I built one, I'd sub an 18" BT-50 to stuff the entire lower half.

[mwtoelle]

I built a Cobra-1500 stock back in the late 70s. It has a BT-20J for the motor tube, and I never had a problem with ejecting the parachute. It has about 51" of tube to pressurize. 24mm motors should have no problem with ejection. The only Estes BT-55 kit with a stuffer tube that I am aware of was the Prime Number Explorer which had a long section of BT-5.

[Doug Sams]

That said... the BBZ has what, a 3' airframe? How much room do we need for the recovery system??? I was actually thinking, if I built one, I'd sub an 18" BT-50 to stuff the entire lower half.I looked it up. I thought it said 18" long. If it's 3', then yeah, an 18" stuffer is just about right :)

Doug

.

[Rich Holmes]

I built a Cobra-1500 stock back in the late 70s. It has a BT-20J for the motor tube, and I never had a problem with ejecting the parachute. It has about 51" of tube to pressurize. 24mm motors should have no problem with ejection.
The Blue Bird Zero comes with an 18 mm adapter, though.