Kevlar vs Nomex vs........any others?

[Wingarcher]

So..... I'm building an upscaled Art Applewhite inspired design (bigger Qubit, with 9.5" square sides) that is going to eject its motor mount and deploy a parachute that is stowed around the motor tubes.

The question is- I'm going to have a couple (at least) ejection charges going off in a somewhat small inclosed space. I need to protect my foamboard/matboard construction. My plan is to wallpaper the space with one of the afore-mentioned products.... Question is, which one? I can also fill the space with "wadding" which should help, some.

It seems that the Nomex chute protectors I picked up a while ago really can't take the heat (they're crispy after 2-3 flights). Kevlar? McMaster Carr catalog gave carbon cloth a pretty high heat rating (700 F? )

N

 

[Stymye]

on my 29mm cone the area forward of the motor mount is a large blob of epoxy used for noseweight , the blob seems to hold up well to the ejection charge. could that work in the maxi-qubit?

 

[teflonrocketry1]

Aluminum foil should do the trick, and its a lot cheaper and more readily available and you could get it in different thicknesses.

Bruce S. Levison, NAR #69055

 

[Hospital_Rocket]

How about some JB-Weld? The stuff will hold the rocket together and is darn near indestructible.

 

[sandman]

How about a small aluminum plate scrounged up from a constuction site?

Like a piece of siding or aluminum flashing would be less than 1/16" thick but thick enough to dissapate any extra heat and not very heavy.

Or...a piece of aluminum pie plate!

I don't think it would violate the NAR "no metal" parts rule. Heck, it probably would weigh less than an Aerotech motor hook.

Of course a couple of layers of heavy aluminum foil would be pretty cheap and replaceable after every flight if you wanted to.

Thanksgiving is coming and my wife always uses the heavy aluminum foil to cover the bird...she wouldn't miss a couple of inches.

 

[DynaSoar]

Originally posted by wingarcher
So..... I'm building an upscaled Art Applewhite inspired design (bigger Qubit, with 9.5" square sides) that is going to eject its motor mount and deploy a parachute that is stowed around the motor tubes.

The question is- I'm going to have a couple (at least) ejection charges going off in a somewhat small inclosed space. I need to protect my foamboard/matboard construction. My plan is to wallpaper the space with one of the afore-mentioned products.... Question is, which one? I can also fill the space with "wadding" which should help, some.

It seems that the Nomex chute protectors I picked up a while ago really can't take the heat (they're crispy after 2-3 flights). Kevlar? McMaster Carr catalog gave carbon cloth a pretty high heat rating (700 F? )

N

Fiberglass insulation. It'll take the heat and cushion the shock.

 

[lalligood]

FWIW, Art recommends filling the tip of his 29mm Qubit with $2 DevCon 5-min epoxy (the kind that comes in the syringes). I've flown my big Qubit 5 times now & it has worked beautifully. I have, however, removed the ejection charge as best I can before loading it into the MMT tube. There's always a little BP residue so I have a *tiny* bit of scorching. I think the epoxy is used to protect the pointy end of the design from impact as well as absorb any ejection charge and/or motor heat.

Seeing how you're building one out of foamboard as well (just bigger), I'd say, scrap the chute idea--and just K.I.S.S. As long as you aren't going to be launching it on a hard surface (like playa), it'll come down slow enough under its own weight with everything intact to land safely.

HTH,

 

[Wingarcher]

How big is that 29mm qubit? This thing is 9.5" on a side. I'm concerned about weight with the recovery because I'm building a 4x24mm mount for it....

The motor mount has the four tubes with centering rings attached to an inner triangle and an outer triangle - the triangles fit into the "cube".

I was thinking last night about flying with D11-P or E9-P and not using any positive MM attachment (except for a string to hold the two parts together). On the launch rod, I'd use a clothes pin or tape to hold the MM, and the shell would just sit on the MM. Thrust of the engines would definitely keep the MM in place. When everything burns out and the shell stops, the MM will fall out because it will be fairly heavy and not experience nearly the same drag as the shell.

This way I'd be a-ok with the ejection charge situation


Is this how the cone rockets that Art Applewhite sells function?

N

 

[Stymye]

the cone is 2 pieces ,the ejection charge blows the shell off and it stays connected to the other half by a shock cord, the shell acts as an aero brake during decent. the motor stays in the mount.

 

[lalligood]

Originally posted by wingarcher
How big is that 29mm qubit?

The sides are 6" square. On an Ellis Mountain G35, it gets about 400-450ft. Never had any damage to it (I launch on a grass field).

The motor tube is attached to a equilateral triangle piece of foam board that mounts inside (under) the 3 square pieces. The tube touches the inside tip.

With no ejection charge, I just friction fit the motor with masking tape.

Download the free 13mm version of the Qubit from Art's site. The big version is put together very similarly but with foamboard instead of cardstock. This model scales up very well, not to mention easily!

HTH,