Grill? Baffle? Support?

[slohand]

Not even sure what to call it. I'm building a long(ish) rocket with dual deployment. The drogue is in the aft section. I'm planning on using the motor ejection to deploy the drogue and a charge for the main. Here is my question/issue. The drogue/lines/shock cord/chute protector is a very small package for all that space in the booster tube. I want to keep the drogue, etc. all as close to the separation point as possible. So my thought is to add a grill(?), baffle(?), or support(?) so the drogue, etc. is held in place and doesn't wander down the booster tube. Is this a dumb idea?

I haven't found any other discussion about this. Maybe because I don't know what to call it LOL.

 

[tsmith1315]

Try a search for “laundry shelf” in the recovery forum.

 

[Hobie1dog]

Try a search for “laundry shelf” in the recovery forum.

that's the first time I've heard that term. I learned something new today.

 

[slohand]

Try a search for “laundry shelf” in the recovery forum.

"Laundry Shelf"!?! Well, I'll be dipped! (Quote from VGG)

 

[dr wogz]

In Canada, it's called: "le tuque shelf" eh, mon ami!

 

[slohand]

In Canada, it's called: "le tuque shelf" eh, mon ami!

Hahahaha! My Mom is from La Tuque

 

[dr wogz]

Hahahaha! My Mom is from La Tuque

I had a good friend in highschool from La Tuque.. she's a head nurse in Peterborough now.

gorgeous drive thru that area!!

 

[dr wogz]

On a serious note: use a centering ring.. the hole in the middle is usually enough to allow separation & keep stuff form sliding down.

another method is to use two chop-sticks: drill 4 holes, so that they pierce the body tube, insert teh stick, so they run parallel to each other. Glue in place, an then sand smooth on the outside.

 

[BABAR]

On a serious note: use a centering ring.. the hole in the middle is usually enough to allow separation & keep stuff form sliding down.

another method is to use two chop-sticks: drill 4 holes, so that they pierce the body tube, insert teh stick, so they run parallel to each other. Glue in place, an then sand smooth on the outside.

I like this idea. May want to coat the sticks with JB Weld or some other heat resistant material as it’s gonna get blasted with the ejection charge on every flight.

 

[slohand]

Using Fusion 360 and a 3D printer gives endless possibilities. Definitely consider a heat resistance option.

 

[dr wogz]

I would take wood over plastic in 'the blast zone'.. (and they are free & easy to come by.. The only time spent is picking up the order & eating it! )

@BABAR : is it any worse than the inside of the tube? the top CR in the MMT tube?

 

[Steve Shannon]

I would do a stuffer tube also so less volume needs to be pressurized.

 

[BABAR]

I would take wood over plastic in 'the blast zone'.. (and they are free & easy to come by.. The only time spent is picking up the order & eating it! )

@BABAR : is it any worse than the inside of the tube? the top CR in the MMT tube?

Minimum diameter or motor mount extensions (aka stuffer or chimneys) that are same diameter or LARGER don’t seem (in my experience) to be a problem.

I have used SMALLER tubes for pop pods in gliders or for rear ejection to provide more space for recovery gear or save weight. THESE have had a problem, if not protected they burn through just forward of motor after X flights (it varies.). So I put a rolled up single layer of aluminum can in the first about 4 inches and no problem.

So I theeenk that items directly or nearly directly in front of blast get toastier than tubes parallel to but not directly impacted.

I have always kinda wondered why gap staged rockets can light a motor over 50 inches away (my maximum successful gap in flight, I have done 6 feet on a test stand) and not light the paper cardboard tube right next to motor on fire. Emma Krystal (Kristal) did a nice NARAM presentation that showed it was hot gas radiance and not particles that lit the motors.

I think this is also how Kevlar mounts on low power rockets tend to burn through after a number of flights, likely during packing the first inch crosses directly in front of the motor.

 

[dr wogz]

Minimum diameter or motor mount extensions (aka stuffer or chimneys) that are same diameter or LARGER don’t seem (in my experience) to be a problem.

I have used SMALLER tubes for pop pods in gliders or for rear ejection to provide more space for recovery gear or save weight. THESE have had a problem, if not protected they burn through just forward of motor after X flights (it varies.). So I put a rolled up single layer of aluminum can in the first about 4 inches and no problem.

So I theeenk that items directly or nearly directly in front of blast get toastier than tubes parallel to but not directly impacted.

I have always kinda wondered why gap staged rockets can light a motor over 50 inches away (my maximum successful gap in flight, I have done 6 feet on a test stand) and not light the paper cardboard tube right next to motor on fire. Emma Krystal (Kristal) did a nice NARAM presentation that showed it was hot gas radiance and not particles that lit the motors.

I think this is also how Kevlar mounts on low power rockets tend to burn through after a number of flights, likely during packing the first inch crosses directly in front of the motor.

thanks for this!

 

[MidOH]

Excellent idea.

I chose to use an extra long motor tube, and a third centering ring on my custom Loc4 build (one tube, not DD split tube). Has the same effect. Maybe I'll add a couple pieces of wood across the front of the motor tube, but my laundry is above a large blanket, and has no possibility of sliding down a 38mm tube.

 

[Handeman]

The laundry shelf is a good idea, but the first thing I would eliminate is the motor ejection. If you're using an altimeter, use it for apogee deploy. Much more accurate and allows for a smaller charge since it will only occur at apogee and all you need is to get the drogue into the air stream not a full extension of the shock cord.

 

[jqavins]

Regarding the thread title, I would call it a baffle, but that's because I would actually install a baffle. You need something for the laundry to sit on, why not get double duty out of it?