Rule of thumb for height above deflector?

[jayarrG7]

I've yet to find any suggestions on how much above the blast deflector to place the rocket engine prior to launch.
I'm thinking that my mid power F40 engines might need more clearance between them and the blast deflector than an Estes C6.
Is there a rule of thumb that I can use to come up with an answer?

 

[Adrian A]

I've yet to find any suggestions on how much above the blast deflector to place the rocket engine prior to launch.
I'm thinking that my mid power F40 engines might need more clearance between them and the blast deflector than an Estes C6.
Is there a rule of thumb that I can use to come up with an answer?

IMO, blast deflectors are disposable. You'll get a straighter flight with the rocket starting out as low on the rod as possible, and I put that at a higher priority. But you can probably save a little wear on them by raising it an inch or so off of the deflector.

 

[ClayD]

The problem is the deflector, and the little spacer it rests on on the bottom of the rod.
The blast could deflect the disk, imparting rod whip. i have had G motors Pound those estes pads HARD.

if your launching from an estes E pad, i think your a little better off, but... couple inches should help the issue tremendously.

just use a clothsline clip or chipbag clip..
another issue is the little spacers on the bottom of the rod, that holds the deflectors.. if the base of the rocket slides down past it, it can cause damage to the rocket(i have had it break of launch lugs.)

 

[jayarrG7]

IMO, blast deflectors are disposable. You'll get a straighter flight with the rocket starting out as low on the rod as possible, and I put that at a higher priority. But you can probably save a little wear on them by raising it an inch or so off of the deflector.

So then, would I be correct to assume that no damage to the rocket or the Aeropack Retainer would come as a conseqence of a spacing of two or three inches above the deflector?
I somehow envision a sort of kickback effect that might catch the tail of the rocket before it lifts off out of the way.

 

[scsager]

So then, would I be correct to assume that no damage to the rocket or the Aeropack Retainer would come as a conseqence of a spacing of two or three inches above the deflector?
I somehow envision a sort of kickback effect that might catch the tail of the rocket before it lifts off out of the way.

This is exactly why I use something... clothespin, chunk of 2X4, etc. to raise the rocket up off the deflector 3-4 inches. To keep the bottom of the rocket from being scorched.

On the low power pads, raising the rocket also helps keep the clips from shorting when using estes style igniters.

Not sure there is a rule-of-thumb. For mid-power, I always use the chunk of 2X4 (club supplied) that's laying on the ground next to the rail.

 

[Rex R]

heh I used a C-clamp*(tightend only to where it would not slide) that just happened to be in my pocket...
rex
*about 3" above the deflector for the launch, about 18" for igniter installation .

 

[bjphoenix]

I think some standoff is recommended to prevent damage to your fins, and of course that would also depend on your fin shape. Consider the amount of flame you've seen in launch photos and take a guess how much standoff you want.

 

[GDJ]

I built my stand with a 12 cm gap <> rocket and deflector. No issues at all.