Any way to reduce ejection delay time on an F27R motor?

[PAL9000]

Hi. Is there a way to take 2 seconds off an F27R? We just learned the Universal Drilling tool doesn't work on this motor, so we're wondering if we can take out the plastic cap in the ejection nozzle to remove a certain amount of powder or whatever substance is used for the ejection charge? Is there a known amount or grams or depth to remove for 2 seconds?

 

[Art Upton]

FYI, the ejection powder grams under the cap does not control the delay time.
It controls how much 'Oomph' the motor has to push out the recovery system.

 

[terryg]

No, there is not. It is one of the major disadvantages to single use motors. What you buy is what you got.
For more versatility get a 24/40 or a 24/60 case where you can adjust the delay as you assemble the motor.

 

[Art Upton]

This is the approved motor list

https://rocketcontest.org/wp-content/uploads/Rocket-Motors-Approved-for-ARC-2025-Sep-2024.pdf

 

[Tom Flint]

Yes there is a way to do it but the resulting motor would no longer be certified.

 

[CoyoteNumber2]

You absolutely can shorten the delay on a single-use motor. People have been doing it for decades.

Remove powder.
Hand-twist a drill bit into the top of the delay grain through the touch hole, 1/32" depth per second removed.
Reinstall powder.

 

[KennB]

Yes there is a way to do it but the resulting motor would no longer be certified.

@PAL9000, please let us know where you are so if you try to fly that with my club we'll know to disallow the use of a motor modified against the rules.

 

[jimzcatz]

Adjusting SU delays does NOT constitute a modified motor. And for the scaredy cats,just don't tell. Delay times are so inconsistant nowadays.

 

[DaveCombs]

@PAL9000, please let us know where you are so if you try to fly that with my club we'll know to disallow the use of a motor modified against the rules.

If you're splitting hairs, you won't find any prohibition of modifying a delay in either the 2025 rules or in the approved motor list documents. RMS motors are allowed (they must be assembled by an adult), and therein is an implication that their delays could be modified because this is routinely done.

The right way to handle this would be to ask the organizers (Trip Barber especially). FWIW, in my years of observing TARC/ARC flights, I've never seen anyone modify a delay.

 

[DaveCombs]

To close the loop on this, here is my email to Trip (with a bad assumption I made), and his reply (with the correction to my misunderstanding):

Trip:
A question came up earlier today concerning whether a motor used in an ARC flight could have its delay adjusted or “drilled”. There is nothing in the rules about this, and delay adjustment is common practice, but I can also see the other side of the argument as modifying the delay would involve removing the black powder from the ejection charge well. I also wonder if there would be a different treatment for RMS motors; since they are required to be assembled by an adult, the delay grain could be modified prior to assembly.
I’d love to hear your thoughts. Thank you very much for your opinion.
Dave –
Teams must use the motors in the manner recommended by the manufacturer. Aerotech provides instructions on modifying delays for their RMS model rocket motors, so this is OK. Modifying the delay on a single-use motor would not be. There is no requirement for RMS to be assembled by an adult, only that they be purchased by an adult. Many teams use RMS at the Finals and we do not allow adults in the prep area, the students must do everything themselves.

Trip

 

[PAL9000]

To close the loop on this, here is my email to Trip (with a bad assumption I made), and his reply (with the correction to my misunderstanding):

Trip:
A question came up earlier today concerning whether a motor used in an ARC flight could have its delay adjusted or “drilled”. There is nothing in the rules about this, and delay adjustment is common practice, but I can also see the other side of the argument as modifying the delay would involve removing the black powder from the ejection charge well. I also wonder if there would be a different treatment for RMS motors; since they are required to be assembled by an adult, the delay grain could be modified prior to assembly.
I’d love to hear your thoughts. Thank you very much for your opinion.
Dave –
Teams must use the motors in the manner recommended by the manufacturer. Aerotech provides instructions on modifying delays for their RMS model rocket motors, so this is OK. Modifying the delay on a single-use motor would not be. There is no requirement for RMS to be assembled by an adult, only that they be purchased by an adult. Many teams use RMS at the Finals and we do not allow adults in the prep area, the students must do everything themselves.

Trip

Thanks for getting this info!