1Matthew

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I bought the 54 mm kit but am unsure if I should also get a 38 mm retainer. Would it be better to do this?
 

OverTheTop

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I bought the 54 mm kit but am unsure if I should also get a 38 mm retainer. Would it be better to do this?
I would have thought you would want a 54mm retainer if you have the 54mm kit?

I would also be making or buying an adapter, 54mm downto 38mm, to give more flying options. That gives you choice of two motor sizes to fly.
 

Jerry F.

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Run a bunch of simulations on Open Rocket to see how well the rocket will perform with some of the 38mm motors that you might like to fly...38's are cheaper than 54's....and a lot of them will get you a good flight for your Lvl 1 flight - no need to go thousands of feet at mach chicken and have a failure when a low and slow flight can win the prize...
 

smstachwick

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I bought the 54 mm kit but am unsure if I should also get a 38 mm retainer. Would it be better to do this?
The word you’re thinking of is “adapter”, I think. The adapter allows you to use a narrower motor, the retainer prevents your motor from ejecting itself out the rear of the rocket.

There is some overlap in 38mm and 54mm impulse ranges. 38mm runs mostly G through J, 54mm runs mostly I through L. “Mostly” because Loki manufactures two 38mm K loads and a single 54mm M load.

If I were to make a recommendation on motor selection, I’d say your best bet is an H motor (available in 29mm and 38mm diameters) with strong but not excessive thrust. You don’t want to send the rocket too high or overstress it. There’s no need for the flight to be super impressive or break performance records, it just needs to be nominal, safe, and recovered without damage.
 

OverTheTop

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If I were to make a recommendation on motor selection, I’d say your best bet is an H motor (available in 29mm and 38mm diameters) with strong but not excessive thrust.
Just fly what you want in the certification rocket. It is your cert and you can choose any motor in the H-I impulse range. If your rocket, as you have built it, should be capable and the flying field is appropriate then just choose a motor.

Many people recommend just using a small impulse H for L1. Personally I have certified on I, K and N. I chose to go one level above the minimum. Either way is right and within the rules. As the flyer you have the choice and need to evaluate the possible outcomes. Listen to other people but make your own decisions :) .
 

JackC

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The word you’re thinking of is “adapter”, I think. The adapter allows you to use a narrower motor, the retainer prevents your motor from ejecting itself out the rear of the rocket.

There is some overlap in 38mm and 54mm impulse ranges. 38mm runs mostly G through J, 54mm runs mostly I through L. “Mostly” because Loki manufactures two 38mm K loads and a single 54mm M load.

If I were to make a recommendation on motor selection, I’d say your best bet is an H motor (available in 29mm and 38mm diameters) with strong but not excessive thrust. You don’t want to send the rocket too high or overstress it. There’s no need for the flight to be super impressive or break performance records, it just needs to be nominal, safe, and recovered without damage.
I think SMS is correct. You are probably looking for a motor adapter. The retainer simply holds the stock size of motor in the tube while an adapter can hold a smaller motor in the stock sized tube. You can make your own adapter or purchase one from Aeropack or Giant Leap Rocketry. Look for a 54mm to 38 mm adapter.
 

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