CG question

[dmaaero]

On my G Force there no room for the chute and shock cord to move up or down the tube. (its in a small comparment)
On my Zephyr the chute and shock cord can be down by the motor tube or up by the nose cone. There is a 2 inch differance on CG depending where its at, we know its going to be at the bottom. That gives me a margin of .87 (marginal).
I could install a baffle or bulkhead with large holes to still allow ejection air thru, to keep the chute an shock cord at the top... that will increase my margin.
Should i even be worried at .87?

 

[SolarYellow]

I'd do a laundry shelf.

 

[Steve Shannon]

On my G Force there no room for the chute and shock cord to move up or down the tube. (its in a small comparment)
On my Zephyr the chute and shock cord can be down by the motor tube or up by the nose cone. There is a 2 inch differance on CG depending where its at, we know its going to be at the bottom. That gives me a margin of .87 (marginal).
I could install a baffle or bulkhead with large holes to still allow ejection air thru, to keep the chute an shock cord at the top... that will increase my margin.
Should i even be worried at .87?

Is that with motor?

 

[smstachwick]

On my G Force there no room for the chute and shock cord to move up or down the tube. (its in a small comparment)
On my Zephyr the chute and shock cord can be down by the motor tube or up by the nose cone. There is a 2 inch differance on CG depending where its at, we know its going to be at the bottom. That gives me a margin of .87 (marginal).
I could install a baffle or bulkhead with large holes to still allow ejection air thru, to keep the chute an shock cord at the top... that will increase my margin.
Should i even be worried at .87?

With a big-diameter stubby kit like that, I shouldn’t think so.

Still, as long as you’re not bumping up against any mass/thrust-to-weight limitations, I should think a shelf of some kind would be the safe option.

 

[dmaaero]

Yes that is with the motor
Total weight with motor H283st is 1703

 

[Steve Shannon]

Yes that is with the motor

Leave it alone then. A rocket like that has a rearward shift of Cp due to base drag.

 

[dmaaero]

I think i"ll go ahead an add a laundry shelf, i don"t doubt it will work fine without one, cause i trust ya"ll.
But i would feel better knowing my CG is more forward. Also there would be a couple handfulls of dog barf around the sides of the engine tube below where the ejection charge comes out. A shelf would prevent it from falling down in there. As long as no one sees a reason not to install it, i will go ahead an epoxy it in.

 

[Lord Rory Gin]

I've got an upscale 4" Ø Boyce builder's kit Mercury-Redstone that I am building. I'm using 2 chutes wrapped in a nomex blanket for the main and the capsule assembly. The chamber is rather long at 570mm (22") long and I'd rather not have the chutes sitting way down at the bottom. The CG is at 0.98 before the motor installation and before adding nose weight.

Would you recommend a laundry shelf to keep the chutes up high and move the CG up? I would like to use something very lightweight like 1/8" plywood similar to the photo above or even cardboard with gussets ALA Apogee' design. A shelf would be about 1/2 way in this chamber.