Plugging Staging BP motors out in the field....?

[DAllen]

I have a bunch of Art Applewhite pyramids I want to give away to kids. I also have a bunch of B6-0 and C6-0 motors I've plugged with epoxy. I might be able to get a bunch more of these motors out in the field so obviously I'd rather not wait for epoxy to set as plugs when I have kiddos that want to fly these pyramids NOW. So I have a bunch of dowels that fit very nicely in the forward end. I'm thinking of cutting a bunch of 1/4" long pieces and CA'ing those into the forward end as plugs. Anyone have experience with doing something like this? Got a better way to quickly plug C6-0s out in the field?

 

[shockie]

Glue in a pre-formed Styrofoam plug? Stuff Estes wadding and tape over it?

 

[aerostadt]

I would be tempted to say don't plug them at all. There is an interpretation that plugging a motor is tantamount to a modification of the motor and hence the motor is no longer certified.

 

[DAllen]

I would be tempted to say don't plug them at all. There is an interpretation that plugging a motor is tantamount to a modification of the motor and hence the motor is no longer certified.

No. This "modification" makes the motors safer for this application therefore falls within the intent of the rules so no decertification necessary.

 

[aerostadt]

No. This "modification" makes the motors safer for this application therefore falls within the intent of the rules so no decertification necessary.

Is this only for BP motors? I know a contrary source for some small composite motors.

 

[aerostadt]

I have done this on one or two occasions for small composite motors. I tend to believe that it is not serious. However, I can point out some contradictions. Article Two of NAR Safety Code:

2. Motors I will use only certified, commercially made model rocket motors, and will not tamper with these motors or use them for any purposes except those recommended by the manufacturer.

https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_298

 

[DAllen]

Ok thanks for you input.

Anyways, any other ideas out there?

 

[cerving]

Stuff the cavity with wadding, and tape it in. You should be fine, and it's within the rules.

And it would be really nice if the motor vendors made a call on plugging motors... I have heard it both ways.

 

[Sandy H.]

My preference is to use 5-min epoxy plugs or not fly those particular rockets that day. Not sure if it is exactly per the rules, but I agree it is better than letting the booster gasses flow on that type of rocket. I've never tried the dowel idea, but it seems like a good idea.

Sandy.

PS: Just saw cerving's response and that seems valid as well. Out of curiousity, I wonder if dripping a few drops of water on top before taping on the wadding would do anything or not. Curious, not suggesting a solution.

 

[DAllen]

Stuff the cavity with wadding, and tape it in. You should be fine, and it's within the rules.

And it would be really nice if the motor vendors made a call on plugging motors... I have heard it both ways.

THIS is the kind of response I was looking for. This will be way easier than making a bunch of wood plugs especially since I'll already have a bunch of wadding and tape with me anyways. Thanks!

 

[Daddyisabar]

A good dolup of 5 min epoxy is the best. Turn the motor when applied to get a good bond on the inside of the casing. Scoring the inside of the casing will make it stronger, but my non scored ones have always held. Epoxy cap gives you a cleaner burn and MORE THRUST. A must in dry conditions, much safer to prevent fires and the Top Men will know this.

NO NO MR RSO, I WANT TO USE A LONG OR MEDIUM DELAY UPPER STAGE MOTOR WITH IN MY SAUCER. Eject on the ground? Poppycock! Modifications are always bad. Oppsie, I stared a fire! Darn oddrocs!

 

[Daddyisabar]

D11P motors put of production.

 

[lakeroadster]

I have a bunch of Art Applewhite pyramids I want to give away to kids. I also have a bunch of B6-0 and C6-0 motors I've plugged with epoxy. I might be able to get a bunch more of these motors out in the field so obviously I'd rather not wait for epoxy to set as plugs when I have kiddos that want to fly these pyramids NOW. So I have a bunch of dowels that fit very nicely in the forward end. I'm thinking of cutting a bunch of 1/4" long pieces and CA'ing those into the forward end as plugs. Anyone have experience with doing something like this? Got a better way to quickly plug C6-0s out in the field?

Why are you plugging the motors? Here is the Launch Prep Instructions:

• Friction fit the motor into the Motor Mount using masking tape. A tight fit is not necessary.​

• Install an igniter in the motor.​

• Put one sheet of recovery wadding in the top of the motor to reduce charring on the inside of the Pyramid. ​

• Insert the Motor Mount into the Pyramid so that the Launch Rod Holes line up.​

• To avoid damage from the motor exhaust, support the Pyramid at least 6 inches above the blast deflector with a clothespin.​

Another option is to modify the pyramids so the gases will vent.

Tim Van Milligan suggests using this approach. Go to 1:35 in the video below.

 

[David Schwantz]

If you have used epoxy with good results in the past, why don't you just prep them at home. Epoxy can then dry before you even get to the field.

 

[DAllen]

If you have used epoxy with good results in the past, why don't you just prep them at home. Epoxy can then dry before you even get to the field.

Because I only have 15 of these motors at home. I am probably going to buy (or someone may donate) more out in the field.

 

[David Schwantz]

Have you thought about just digging out the BP?

 

[GlenP]

Do the motors pop out, or do you friction fit or tape them in tight so they stay in the rocket? To help the pyramid last a bit longer you could treat the exposed portion inside above the thrust ring with some high-temp BBQ paint, maybe? Still a sheet of wadding or something on top of the motor would help too. Or some kind of single-use sacrificial paper liner in the pyramid, like baking parchment? Maybe add a small venting hole to let the hot air get out. Just some other ideas to treat the rocket, in addition to, or as an alternate to, the engine.

I used some of the BBQ paint inside an X-24, it helps them last a little bit longer, but it will burn through after several launches eventually.


The Qubitz rockets have little vents on top, for example:


PS - have you built any of the Art Applewhite monocopters, 13mm or MMX size, no plugging needed for those! Maybe not as high, but they make a neat sound and smoke trail.

 

[shockie]

If I was at a launch and I told the RSO that I was going to plug some -0 motors with wadding/dogbarf and a small piece of duct tape, his probable response would probably be: So What?

People have been doing this for at least 25 years.

It's simple, quick and does the job intended. If the gases can't escape out the top end they will just go out the nozzle.

A typical Estes C engine has a max chamber pressure of around 225 psi during the thrust phase and this is at peak thrust.
When burn through occurs the pressure immediately drops to what ever sea level altitude you are at, normally 14.7 psi.

 

[SharkWhisperer]

Have you thought about just digging out the BP?

In Estes booster motors, the propellant is continuous (no delay, no ejection, no clay cap) and when it reaches the end it burns at low pressure with exhaust going in both directions; because no nozzle restriction at the boosting end, the flamefront preferentially goes that direction to (usually, unless plugged) ignite the sustainer. And though low pressure, the flame and gas jet is appreciable in both travel distance and temp, sufficient to guarantee sustainer ignition. Hence plugging it up so that flame just goes through the nozzle end.

Digging into the BP grain risks unpredictably altering flight performance.

 

[Ez2cDave]

Glue in a pre-formed Styrofoam plug? Stuff Estes wadding and tape over it?

Stuff the cavity with wadding, and tape it in.

The tape will likely prevent the motor from being inserted into the motor mount.

Dave F.

 

[Marc_G]

For what it's worth, I've found packing with dog barf and a wrap of blue masking tape around the top to seal it to be more than sufficient to plug the thing and stop blow-through. I kinda scrunch the blue tape down into the open top of the engine with a small extra piece of tape over the top. Takes about 15 seconds to prep and is reversible.

I've sometimes wondered why on earth people bothered with the epoxy method, given it would invalidate insurance coverage if there was an accident/fire, and not be reversible. But different strokes for different folks.

There's lots of ways to fly a rocket, or a pyramid...

 

[jimzcatz]

This again? Would have been better to ask what kind of glue should I use?

 

[lakeroadster]

This again? Would have been better to ask what kind of glue should I use?

 

[bad_idea]

Stuff the cavity with wadding, and tape it in. You should be fine, and it's within the rules.

Thank you for this idea. It saves me a lot of trouble finding the appropriate sized dowel and o-ring so as to plug without "modifying" the outrigger motors in a future mixed-motor cluster build.

Any idea if this - or a similar, non-"modifying" fill to keep all the RSOs happy - will work with a motor with ejection charge too?

 

[Marc_G]

Thank you for this idea. It saves me a lot of trouble finding the appropriate sized dowel and o-ring so as to plug without "modifying" the outrigger motors in a future mixed-motor cluster build.

Any idea if this - or a similar, non-"modifying" fill to keep all the RSOs happy - will work with a motor with ejection charge too?

I don't advise it. The ejection charge makes a lot of gas and particles and a higher pressure than the blow-through of a booster motor.

One of my birds a decade ago had three outboard pods with engines in them. Using B6-0, plugged with barf/tape worked fine but to allow me to use regular engines, I designed the pod forward cones to pop off upon ejection of the side engines. Cones were attached by shock cords.

Benefit was as the rocket coasted up, I had 4 tracking smokes going! Used shorter delays on pods than center engine. So they would be finished their business by the time the chute deployed.

 

[Ez2cDave]

I sent erockets an email describing the problem and referring them to this thread.

Dave F.

 

[bad_idea]

Figured as much. Thanks for confirming.

The A10-0, C6-0, and D12-0 should suffice for me.

 

[dpower]

I'll have to try the wadding/tape method - plugging boosters with epoxy works perfectly (though epoxy is definitely modifying the motors, hence violatig the NAR safety code). I once tried friction fitting dowels tightly with masking tape, this did not work - the dowels acted as small projectiles inside the MMT, kicking the motors and damaging the plugged motor tubes.

 

[Ez2cDave]

I'll have to try the wadding/tape method - plugging boosters with epoxy works perfectly (though epoxy is definitely modifying the motors, hence violatig the NAR safety code). I once tried friction fitting dowels tightly with masking tape, this did not work - the dowels acted as small projectiles inside the MMT, kicking the motors and damaging the plugged
motor tubes.

The tape might prevent the motor from being inserted into the motor mount.

Dave F.

 

[Alan15578]

I'll have to try the wadding/tape method - plugging boosters with epoxy works perfectly (though epoxy is definitely modifying the motors, hence violatig the NAR safety code). I once tried friction fitting dowels tightly with masking tape, this did not work - the dowels acted as small projectiles inside the MMT, kicking the motors and damaging the plugged motor tubes.

Interesting. Back from my old competition days, this issue was that nothing may be permanently "affixed" to the motor. Adhesive tape was OK, but glue was not. I have heard that corking the motor works and is legal, and could even be done on the field. This is not cheating like corking a bat in baseball. Rather the booster motor is plugged by inserting a cork, like bottling wine. I have never done this, but I have bottled wine.

I have a cheap hand held wine corker. The corks are first soaked in water. the corker compresses the diameter of the cork and pushes it into the bottle. I doubt that a wet cork would be compatible with a BP motor. A more industrial corker might work better. Wine corks are one of the most expensive parts of home wine making and they are hard to find. Commercial wine bottling has mostly gone to screw closures and elastometric plugs that can be removed with a cork screw. I see no reason why a suitable elastometric plug and insertion tool could not work for plugging BP motors.

My approach would be to use a thin metal disk with a double sided tape gasket, and a very strong motor retention method.