Any tips/tricks for group build of BMS School Rockets?

[Grant_Edwards]

Next week I'll be leading a Girl Scout troop group build of BMS School Rockets, and was wondering if there are any tips or tricks specific to the School Rocket that I should be aware of.

The age group is mostly 9-11 with a few older siblings thrown in. There will be 17 kids building in the group. There should be 3-4 adult helpers along with a couple older siblings who've built a few rockets.The same group did a build of E2X Generics last fall and it went pretty smoothly (I had done some prepping of the kits: tubes were cut and marked, nosecone plastic was trimmed, 'chutes had pre-attached snap-swivels. I had added some kevlar string and it and elastic shock cord had pre-formed loops). For the Generics, I had drawn up my own directions, because I wanted to do things in a different order than the Estes instructions.

The BMS School Rocket will the 2nd rocket build for most of the group (there might be 1 or 2 first-timers).

For the BMS School Rocket, I'm planning on using the BMS directions and building pretty much stock (unless somebody convinces me otherwise). I've got the optional parachutes, so I might include pre-tied loops of kevlar with attached snap swivels to make detachable streamers.

 

[BEC]

Since the School Rocket has laser etched marks and such....there really isn't anything to pre-do or any re-ordering of the steps. I've not done a group build with the parachute version, only the streamer, but that doesn't really matter.

If you're doing this next week it's probably too late to get any Qualman fin guides to hold the fins out perpendicular to the body. About half way down this page: http://qualmanrocketry.com/Class_Packs.html

 

[prfesser]

Probably the most tedious part for newbies of building a rocket with balsa fins is gluing the fins to the airframe. The double-gluing method is your friend. JIC you aren't familiar with it:

Apply a small bead of glue to the root edge of the fin.
Press the root edge to the mark on the body tube.
Remove the fin. If there's too much glue, wipe some off both surfaces.
Repeat for the remaining fins.
Give it a few minutes to dry somewhat.
Apply a second small bead of glue.
Press the fin to the body tube and hold it for a half-minute or so. It should stay in place fairly well now.
Repeat for the other fins.

 

[Grant_Edwards]

Since the School Rocket has laser etched marks and such....there really isn't anything to pre-do or any re-ordering of the steps. I've not done a group build with the parachute version, only the streamer, but that doesn't really matter.

I think I'm just going to have them tie a loop in the kevlar instead of stapling the streamer to it, then they can clip on the parachute or the streamer.

If you're doing this next week it's probably too late to get any Qualman fin guides to hold the fins out perpendicular to the body. About half way down this page: http://qualmanrocketry.com/Class_Packs.html

I should have asked earlier!

I had completely forgotten there were classroom packs available. I just submitted an order for the 24-pack and sent a follow-up e-mail offering to pay an expediting fee and additional shipping if there was any way to speed up delivery. Standard shipping is listed as 2-5 business days, so I'll keep my fingers crossed. The last time somebody sent me a package via USPS it bounced around between three local facilities for a couple days (passing through each one twice) before they finally decided to deliver it.

Thanks for the pointer.

 

[rharshberger]

The BMS School rocket IMO is the best kit for that age group and older ages as well, the instructions are clear, parts laser etch with marking, and the fins will always be on straight (not canted off axis), the hard part will be keeping everyone building at measured steps...if you can manage that its super easy.

 

[cls]

I have found that new folks understand double gluing after I demonstrate with a couple pieces of carstock. and a sly reminder that we're not in kindergarten anymore so don't make a puddle, just a thin layer.

 

[rharshberger]

I think I'm just going to have them tie a loop in the kevlar instead of stapling the streamer to it, then they can clip on the parachute or the streamer.



I should have asked earlier!

I had completely forgotten there were classroom packs available. I just submitted an order for the 24-pack and sent a follow-up e-mail offering to pay an expediting fee and additional shipping if there was any way to speed up delivery. Standard shipping is listed as 2-5 business days, so I'll keep my fingers crossed. The last time somebody sent me a package via USPS it bounced around between three local facilities for a couple days (passing through each one twice) before they finally decided to deliver it.

Thanks for the pointer.

David Qualmann makes fantastic products, if you cant get them in time and know someone local with a 3d printer fin guides can be printed pretty quickly if kept thin and basic (say similar to a payloadbay.org fin guide).

 

[Grant_Edwards]

Probably the most tedious part for newbies of building a rocket with balsa fins is gluing the fins to the airframe. The double-gluing method is your friend. JIC you aren't familiar with it:

I always do double-gluing for "normal" fins, but wasn't sure if it was practical for TTW fins like the BMS School Rocket.

 

[BEC]

As long as you sand off the retention bump on the root of the fin, it should seat well on the motor tube through the fin slot, so yes, double gluing will work. This is one place where motor tube centering rings being too loose (which I've seen sometimes, and which I thought I'd mentioned in my first post, but apparently didn't actually type it in) can cause minor problems as the motor tube can wind up not quite perfectly centered. In that case, so some fin tabs are too long and some too short....but there's little one can do about that other than offer helping hands at build time.

But the SR is a reliable flyer which is very tolerant of lousy weather (windy days). I often build my own with the optional payload section.

 

[rharshberger]

As long as you sand off the retention bump on the root of the fin, it should seat well on the motor tube through the fin slot, so yes, double gluing will work. This is one place where motor tube centering rings being too loose (which I've seen sometimes, and which I thought I'd mentioned in my first post, but apparently didn't actually type it in) can cause minor problems as the motor tube can wind up not quite perfectly centered. In that case, so some fin tabs are too long and some too short....but there's little one can do about that other than offer helping hands at build time.

But the SR is a reliable flyer which is very tolerant of lousy weather (windy days). I often build my own with the optional payload section.

Its also extremely tolerant of fins not being perpendicular to the tube.

 

[BEC]

Yeah. The slots make sure they're straight, and that's more important for basic flight really than perfectly perpendicular fins for sure, at least in the regime the SR operates in. It will do 1700 feet on a D10-7, though.....

 

[Grant_Edwards]

As long as you sand off the retention bump on the root of the fin, it should seat well on the motor tube through the fin slot, so yes, double gluing will work.

Thanks for the tip. Sanding the bumps off the fin tabs sounds like something I might want to do ahead of time.

This is one place where motor tube centering rings being too loose (which I've seen sometimes, and which I thought I'd mentioned in my first post, but apparently didn't actually type it in) can cause minor problems as the motor tube can wind up not quite perfectly centered. In that case, so some fin tabs are too long and some too short....but there's little one can do about that other than offer helping hands at build time.

I'll make sure I have a sanding block along to adjust the fit of fin tabs if needed.

But the SR is a reliable flyer which is very tolerant of lousy weather (windy days). I often build my own with the optional payload section.

We'll be launching a week later, and if it's breezy we'll probably be using the streamers instead of the parachutes.

 

[BEC]

I'll make sure I have a sanding block along to adjust the fit of fin tabs if needed.

I just realized/remembered it's not that hard to tweak the fins with a sanding block where needed....take a little off the tab if it's too tall, take a little off the two bits that touch the main body tube fore and aft of the tab until the tab seats on the motor tube if the tab seems to be too short. But it would probably be much easier to do than to explain...

 

[prfesser]

I always do double-gluing for "normal" fins, but wasn't sure if it was practical for TTW fins like the BMS School Rocket.

Sorry, I didn't realize that the school rocket had TTW fins. That should make assembly even easier.

 

[Grant_Edwards]

I just realized/remembered it's not that hard to tweak the fins with a sanding block where needed....take a little off the tab if it's too tall, take a little off the two bits that touch the main body tube fore and aft of the tab until the tab seats on the motor tube if the tab seems to be too short. But it would probably be much easier to do than to explain...

You're right, it shouldn't be difficult to do once you know it needs to be done. I'm also anticipating at least one engine mount (despite being pre-marked) will end up with the centering rings too close together so that the fin tabs need to be "adjusted" for that. The troop leader, one of the scouts, and a couple of the other helpers are going to do a trail run building one of the kits tonight.

 

[Sooner Boomer]

One thing I would add, is that with the double-glue method, it helps to actually take a finger tip and rub the glue into the pores of the balsa. Have a wet paper towel ready ahead of time so gluey fingerprints don't end up on everything.

 

[Echo3]

I led a group build of BMS School Rockets about a week and a half ago. It was the first time we had built this rocket together and it turned out to be a great choice. One thing that several kids/parents had trouble with was the dowel that is glued into the nosecone. Some builders did not understand from the instructions that the dowel should be pushed all the way into the nosecone until the end is flush. I caught one and fixed it before the glue dried but there was another one that wasn’t fixed. The Rocket is roomy enough that it does not hurt for the dowel to stick out. I asked for s parent to be available to help each Scout and I built a rocket with them and we went through the build together step by step. The School Rocket was easy enough to build that some parent Scout teams were working ahead though.

 

[Grant_Edwards]

I led a group build of BMS School Rockets about a week and a half ago. It was the first time we had built this rocket together and it turned out to be a great choice. One thing that several kids/parents had trouble with was the dowel that is glued into the nosecone. Some builders did not understand from the instructions that the dowel should be pushed all the way into the nosecone until the end is flush.

A couple days ago I did a trial run build of one of the School Rockets with one of the older kids who's going to be helping out. We were unable to get the dowel all the way in to the NC. We gave up with it about 1/4" proud. I may have them glue the dowel in before installing the screw-eye — that way they can bang it on the table to drive the dowel in. At least with the one we built, there's no way you can just "press" it in so it's flush.

If we do it in that order, I'm sure at least one will glue the dowel in the wrong way, so I'll have a drill handy with a bit sized to drill a pilot for the screw eye.

I'll also have to remember to bring some dowels or rods to put through the screw eye to act as a "handle" to screw it in. There's no way we could have screwed it in with bare hands.

I don't understand why the instructions have you put the kevlar string through the body tube before gluing in the engine mount. [Maybe I misunderstood the instructions?] The string does nothing but get in the way while applying the glue. It think it would far easier to drop the kevlar down through the engine mount so it's hanging out the bottom of the mount before gluing the mount into the BT. Then later you can push the string back through the engine mount and out the top of the BT.

The classroom packs of Qualman fin guides arrived today, so that should make the fin alignment pretty fool-proof. I need to check to see if the fin guides will slide off over the launch lugs (IIRC the School Rocket lugs are a bit larger than the ones generally used on LPR BT50 rockets).

 

[BEC]

True, the School Rocket has 3/16 launch lugs. Bill Saindon told me he did that to make it easier for younger kids to get the rocket on the launch rod.

I didn’t think of that when I suggested the Qualman classroom-pack fin guides. Oooops!

 

[Grant_Edwards]

True, the School Rocket has 3/16 launch lugs. Bill Saindon told me he did that to make it easier for younger kids to get the rocket on the launch rod.

I didn’t think of that when I suggested the Qualman classroom-pack fin guides. Oooops!

They'll be fine. It only took a couples seconds with a pair of scissors to enlarge the launch lug cutout so that the guide will slide off over a 3/16 lug. During the test build, I used one of the fancier Qualman BT50 3/32 fin guides, and it worked great. Then I realized I'd have to bend one of "tabs" up to get it off over the launch lug.

 

[BEC]

I was envisioning trying to use a sharpened piece of 7/32 or 1/4 inch brass tubing to use as a punch to do that….kind of overkill, I suppose. Scissors work.

 

[Grant_Edwards]

Well, I was thinking about a sharpened 1/4" copper coupler in a drill press:

https://www.homedepot.com/p/Everbil...Coupling-Fitting-with-Stop-C600HD14/204583730

 

[BEC]

I have had this set for years and years (though this is not my picture — this one is stolen from a listing selling this set on RC Groups) ….

So I just naturally think in terms of sharpened brass tubes for cutting nice round holes in balsa and paper. I even show using a piece of 3/32 tubing (epoxied in a 13mm motor casing for a handle) for cutting static ports in rocket body tubes in my article on altimeters in the NAR Member Guidebook. The smallest one in this K&S set is 1/4 inch….it actually would have worked well for modding David Q’s fin guides for your School Rocket application.

But as I say, scissors, for your use case, are good enough.