Adjusting delay in an F67

[kelltym88]

This may seem like a dumb question, and please note I am an experienced rocketeer, I was wondering if it is possible to adjust the delay time on the F67's? Like drilling a small hole from the top to delay it just a bit (I have F67-6 and I want just a bit shorter). Now I know on a reload, you can adjust the delay by drilling the delay grain and the drilled end goes against the propellent. What happens if you drill it from the top?
Please, I am not proposing doing anything dangerous, nor am I gonna go rogue and experiment, I am curious if it can be done. And if not why?

 

[jmasterj]

That is not a manufacturer-designated modification, and is therefore not allowed at NAR launches and would technically require Tripoli L2 at a Tripoli launch. Dumping the BP, drilling into the delay, and then replacing the BP should work, but do you really need something in between an F67-4 and an F67-6?

 

[Tractionengines]

Boy did you open a can of worms....

Short answer. Yes it workes. (Don't go less than 4 seconds. ie. Take off more than 2 from your -6 motor.) The DMS line of single use motors are drilled from the outside. So from a functional aspect it works. Drill carefully.

NOW the conflicting bit: "Is this now an EX motor that can only be flown at Tripoli launches and under EX rules...?" That is up to you and your RSO / launch site. The latest feedback when someone "pushed" Tripoli and Aerotech for "official" responses was "modifying delay times of motors where it is not in the manufacturers instructions is NOT approved". So therefore it IS a modified motor.

[ Note: pulling the red plug and adding/removing powder from the ejection charge to match requirements of rocket IS approved, and not a modification of the motor. (So far). ]

 

[lakeroadster]

This may seem like a dumb question, and please note I am an experienced rocketeer, I was wondering if it is possible to adjust the delay time on the F67's? Like drilling a small hole from the top to delay it just a bit (I have F67-6 and I want just a bit shorter). Now I know on a reload, you can adjust the delay by drilling the delay grain and the drilled end goes against the propellent. What happens if you drill it from the top?
Please, I am not proposing doing anything dangerous, nor am I gonna go rogue and experiment, I am curious if it can be done. And if not why?

https://www.rocketryforum.com/threads/rocket-motor-delays-explained.171511/page-3#post-2257978

 

[waltr]

Yes, I have done it and it does work. I only had a F67-9sec delay and needed 6 sec. So drill 3/32 deep into the delay element. Ejection fired at 6 seconds after burn-out.

Other addressed the rules.

 

[kelltym88]

Thank you all for your replies. Lakeroadster, thank you for the link. My question has been answered.