suggested engines for LOC kits

[caheaton]

Hello, I recently completed building a LOC Onyx (my first LOC kit and first non-Aerotech mid power kit). Besides coming in a bit heavy (weighs 20 ozs with modifications...larger parachute, sonic locator, etc.), the suggested engines from LOC seem to have delays that are far too long (even for the "stock" weight of 13 ounces). LOC suggested using G40-10 and F50-9 engines. Even at 13 ounces, Rocksim showed these delays to be too long. Given my current weights, the following engines seem to be about right:
F25-6, F50-6, G40-7 and possibly the F20-4 (chute deployment a tad early with rocket moving at 37fps, but should be okay given the stout chute)

What does the group feel about this...do you feel that LOC kits often specify a delay that is too long?

Craig (a recent BAR)

 

[loopy]

First place I'd check is EMRR and see if there is a review of that rocket there. The flight logs at the bottom of the review will give a pretty good idea on what's good for that rocket.

I've never built an onyx, but I have a couple of other LOC kits that I absolutely love.

As for determining delays, Rocsim tends to be pretty optimistic in it's altitude estimates, and there fore tends to suggest delays that can be too long. YMMV.

 

[shreadvector]

Already answered on r.m.r.

LOC lists *WAY* too long delay times for their kits.

The kits are heavier than designed.

ALWAYS use the motor manufacturer's recommended maximum liftoff weight for any motor being used.

 

[DKrause]

I've had several great flights on my Onyx on G77R-10s. Fast and high, just the way I like 'em..

 

[Fore Check]

If you have RockSim, the following file might help.

My flights have matched fairly closely to the predicted numbers on this file. I used it do determine delay lengths for reloads.

Flies very well on a G33-7J!

 

[DJDeadParrot]

Originally posted by caheaton
LOC suggested using G40-10 and F50-9 engines. Even at 13 ounces, Rocksim showed these delays to be too long. Given my current weights, the following engines seem to be about right:
F25-6, F50-6, G40-7 and possibly the F20-4 (chute deployment a tad early with rocket moving at 37fps, but should be okay given the stout chute)

Welcome Craig!

Okay, here's my somewhat limited experience from about 15 years ago having owned an Onyx. For an F25, use a 6 second delay. It might eject a bit early if the flight goes straight up, but my Onyx was just a little bit prone to weathercocking on longer burn motors. Consequently, an F50 with a 9 second delay worked out better than a 6 second delay provided the rocket goes straight up. I also flew mine a lot with black powder F50-7s and F100-6s, and found those delays to be nearly perfect. Only one G flight to speak of, and that was a G40-10; delay was a bit long. Never did try a G80 or a G64, but I suspect that 7 seconds will be on the short side for those motors in an Onyx.

 

[caheaton]

Just an update for the group...thank you very much for your help and suggestions. Finally got to launch my Onyx yesterday. It was a tad breezy, but not too bad. Winds were maybe 10 MPH when the rocket went up. Maiden flight was with an F20-4 Econojet...beautiful flight with just a touch of weather cocking into the wind that made for an attractive smoke trail. I used a 6 foot rod to help the rocket build speed before "clearing the tower". I had hoped to launch again with an F25-6, but had a devil of a time getting the ignitor to go into the slot in the grain, so we gave up. (See my new post for more on this.) Overall, I'm quite pleased with how it flew...I was a touch worried about stability and weather cocking due to slow lift off but all went well!
Craig

 

[jimzcatz]

I may be out of bounds here,and If I am,I apologise,but you do know how to trim the delay in composite motors,dont you?

Jim Scarpine
TRA 1377
Cert3

 

[caheaton]

No problem...not out of bounds. I have heard of trimming delays, but I didn't think it was possible with single use motors. I have never used an RMS motor, but have one on the way (a Rouse Tech 24/40 case) along with a few reloads. (E28-4, D15-7, F39-6 and F24-4...don't worry, the D load isn't for the Onyx! )
I was on the fence about getting a 24 or 29mm RMS, but decided on the 24 for now as I prefered the loads that were offered for use with my existing fleet. I have the 29mm case on my Christmas wish list.
Craig

 

[jimzcatz]

Yes you can,we were trimming delays long before the invention of the reloadable motor.

 

[n3tjm]

How stable was the Onyx on the G motor? I had bad luck flying mine with G motors...

 

[Rock_It]

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