substitute c11 for d12's

What would that rocket be more specifically? Length, weight, configuration, etc.

tah

You got it. Since the average thrust rating is fairly close between the two engines, the C11 should be able to get a safe liftoff with a rocket that normally takes a D12 (especially if the rocket is light enough that you're concerned about it going out of sight on the D...).

You may want to use a slightly shorter delay - i.e., a rocket that normally takes a D12-7 may work well with a C11-5.

-dave w

The risk is that it may not go high enough to properly deploy the parachute. Plus, you have to figure out the right delay such that it deploys at apogee, instead of after it hits the ground ;-)

OTOH I flew my original solar sailer on a 1/2A-T with a 13mm/18mm adapter. Went up about 30 feet :-)

Read it.

it lists recommended max lift-off weights. These get lower as the delay time gets longer or as the total-impulse of the motor gets longer.

If you have a heavy model, use a shorter delay time and use a long (4 to 6 feet) and stiff (steel, 1/4 inch diameter) launch rod.

-Fred Shecter NAR 20117

I find that C11's are a good choice for anything that might go a long way on a D12, but would be underpowered on a C6. The first 0.8 seconds of the D12 thrust curve is close to the C11 (C11 thrust is slightly lower, and there is some variation in curves from different tests), so until that point, your rocket will behave pretty much as if it was on a D12.

Best thing to do is to run a simulation, but as a general rule, try going down one delay step, as suggested.

Another option, if the rocket is light enough (I did this in my 'Vikinger' - see

is to take a spent D12 or C11 casing, knock out the clay nozzle, and use it as a 24-18mm adaptor. IIRC the max liftoff weight for a C6 is around 110g, so if your rocket is lighter than that, you can use that method. C6's are a bit cheaper than C11s, but in a light rocket, C11's are more impressive :-)

HTH

-- Niall Oswald ========= UKRA 1345 L0 EARS 1151 MARS