actually what I was thinking about is the new AT/RCS superplastic LUR casings....instead of AP use BP... with the lower pressure and temperature burning characteristics of BP vs AP, you should be able to get at least twice the number of flights per casing 3 ap vs 6 bp.... the same LUR casing would then use the same new variable adjutment delay module.....
with 24/29mm LUR you should be able to do Full BP D and E and small F....
shockie B)
Or, is happy to see that a delay modification which has been a widespread violation of the safety code everybody winked at is now authorized and completely legal. And, it isn't just the HP motors...the process can be used in a 24mm case as well. Weather permitting this weekend the Silver Comet is going up with a drilled delay to try to dial in ejection right at apogee for a change.
Trying to make each flight as optimized as possible is a large part of the enjoyment I get from the hobby. RCS has just freed me to make the single greatest change in a flight profile that I can and I appreciate that.
Again, not really practical in birds originally designed for a D.
IIRC David's quote correctly, CAR/TMT/S&T don't need to buy off on the RCS delay modification procedure. Unless somebody files a formal protest flyers are free to follow the procedure as desired.
Why ? Assuming (because I must have been very bad in a previous life) you win the jackpot and get to observe my L1 cert flight this summer. I announce that I am going to drill the delay grain 1/16th of an inch to reduce the delay time by two seconds. You watch me drill the grain. You watch me double-check to see the stop on the drill only permitted me to drill the 1/16th inch hole I intended to. You watch me assemble the motor with the drilled side down because I think it looks better that way. What is so different than if I had used a ProDAT on a Pro38 delay grain ? I don't see anything scary in that.
Which, of course, is why you sim as carefully as possible, fly as accurately as possible and use the results to feed back into the sim.
The post from CTI detailing the additional testing clearly indicated they were proving the process would work reliably when released to hobby flyers. Seems a prudent step on their part to me. I don't see any 'backdoor' collusion here. Following a spirited (and _mostly_ civil) thread in rmr Gary published an approved method to adjust the delay time in RCS reloads. In my view that's a good thing.
If you can't do anything better than that maybe you should just stick with Estes and Quest BP motors.
John
FTR they could also specify nozzle throat drill-outs if they choose. It would increase the burn time, lower the thrust, shorten the delay, and increase the drama and consumer interaction.
All while not changing the production line.
Tandems are impractical on APCP composites :-(
I did not actively advocate it because he had not yet even blessed delay mods, which are far more useful generally.
YMMV :-)
Point.
Before you do, look at the NAR S&T web page to see what the true delay is for the motor, and base your mods off that number instead of the number on the package. For example the E28-6 is really about an E28-2 and you really wouldn't want to shorten it by a couple seconds if you really need a -4...
:-(
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
This is a violation of NFPA 1127 which is (the last time I checked) the official safety code of TRA. NAR has also said (via Trip Barber) that NAR launches should follow either the NAR HPR safety code or NFPA 1127, whichever is the most restrictive.
NFPA 1127 - "4.5.3 The components of a reloadable high power rocket motor shall not be altered."
Absent an official announcement from TRA (who have certified nearly all of the Aerotech HPR motors effected) or possibly NAR S&T, I am afraid that I would consider drilling delays to be a violation of the safety code. My personal opinion only and worth everything you paid for it. :-)
After watching Aerotech plead with the NAR board at NARAM-44 to allow drilled core J350's to be flown and fail, (the board insisted that the motor be recertified) I cannot see how NAR would approve now of drilling delays. So far, all we have is "Bunny says" which simply isn't sufficient.
Drilling delays seems to me the wrong thing to be doing. However, I would love to be able to swap delay elements. Since the RDK+ line already provides about every delay you could possibly want if you could just swap out as needed, drilling isn't really required.
I don't have a copy of 1127 here, but 1125 is the motor standards and the safety code IIRC and the motor testing policy IIRC both state use "as recommended by the manufacturer" is permissible.
While I agree the above statement seems conclusive, one wonders, altered from what? At all? From what the instructions, design and method of usage allows?
Simply by adding variable not fixed amounts of BP to reloads, one is already "altering a component" while strictly following the instructions and/or rules.
Stripping wires from an igniter is a mod.
Even switching out delays from what is included in the package itself is alteration.
Jerry
Is the shiney side out?
-----snipping my drivel-----
Huh ? I thought the NAR Safety Code and NFPA 1127 were in agreement already ? How can one be more restrictive than the other ? And, if there are differences, wouldn't that be a clarion call for a resolution committee ?
I construe that to incorporate an unwritten clause "unless specifically authorized by the manufacturer".
-----snip-----
I agree that the drilled cores should have been recertified. The Board made the right call that time because the procedure hadn't been formally published. And, drilling a core incorrectly can lead to a really, really loud BANG. Drilling a delay grain incorrectly can only lead to premature ejection possibly a zipper and a lesson learned :-)
Drilling RCS delay grains following instructions now published in the public domain is in my opinion (whatever THATS worth) a process which is legit for us to use.
Personally, I think a preferable approach is for the manufacturer to supply the longest possible delay in each reload kit, along with simple instructions how to shorten the delay by drilling X inches per second shortened. The 'Infinitely variable delay" ideal.
John
Did you forget the propeller again???
David Erbas-White
Yes. Mandatory,
Throwing in my two cents...
I have no problem with the current method of supplying the 'medium' delay. Statistically, there are probably more people who use the medium delay 'out of the box', so for those who DON'T want to modify anything, this is the most 'cost effective' method. Selling the other delays on the side works for me, too.
Putting the long delay in would then (almost) FORCE people to do their own delay modifications (personally, the long delays are the ones I use the least), so I'd either be out of pocket for buying the 'right' delay, or have to modify each delay manually.
The way it stands now is optimum (IMHO). It provides the most cost effective solution for the majority of users, but ALLOWS those who want to modify things even further to do so.
David Erbas-White
The NAR HPR Safety Code is "derived" from NFPA 1127. The TRA Safety Code is NFPA 1127 vernatim.... thats the difference... there was supposed to be a joint nar-tra committee to "merge" the differences between the two, but have not hear the results...
shockie B)
-----snip-----
Well, we might be approaching a win-win situation here. You are probably correct that some flyers don't want to have to fool with the delay grain and others (like me) who will want to be able to dial it in as closely as possible.
At the end of the day, its gonna be decided by market forces. If one motor manufacturer can cut a buck off the cost of their reload kits because they don't have to carry the overhead associated with providing several different delay grains (3 ? 4 ? more ?) I KNOW whose HPR system I'M gonna use !
John
Propellers are a TRA conspiracy to keep Jerry out.
jerry, those don't work if you don't have any brains in you head to protect.
Think of the NAR HPR code as a "Reader's Digest Condensed version". The NAR code isn't anywhere near as long or detailed as NFPA 1127.
Wishfull thinking does't make it so.
It is followed by:
"4.5.4 A high power rocket motor or its components shall not be used in a manner or for a purpose other than that specified by the high power rocket motor manufacturer in the instructions."
But the prohibition against alterations appears to be absolute as there is no "unless" clause in 4.5.3
If you don't like it, NFPA 1127 is nearing the start of its next revision cycle. Visit the NFPA web pages to find out how to submit a change proposal.
jerry's not doing it right, he's just using a Fosters lager can with the end cut off!
Care to make a proposal?
So now you are assuming I have brains?
That is not consistent with the fact I invited you to become a partner and put up with you NOT ever investing the $5000 you solumnly promised, or contributed any notable labor.
Point.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.