Klima ignition-to-thrust time

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Y3kankerous

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Currently planning a couple of clusters where I would like to use a mix of Klima composite and BP motors, but am aware of the potentially longer ignition time on composites, meaning the thrust curve will have a lag compared to fast igniting BP.
Just to spell out what I think that means (in case I am not quite hitting the nail on the head)... if the composite and BP starters all ignited simultaneously from one electric supply (or tape match from a single electric starter), then the BP motors would achieve pressure and thrust earlier than the composite... which could have a few implications, for example if the BP early thrust peak gave enough of a kick to get off the rod, but didn't have enough plateau thrust then the model could take off but then stall and be non vertical when the composite thrust kicked in. Which might be "sub-optimal" 😯 Or with a bit of luck, the igniter might have pulled out of the composite before it took

I'm aware that Klima products have less availability outside Europe, so will be less experience to tap into but hoping someone may have some pointers, or possibly a vid. Had a search on the forum but didn't find anything specific to Klima.
My understanding is that, unlike many composites (but like Cesaroni), Klima motors have an integral BP charge which is ignited by the starter, meaning less considerations with ignition because the BP takes easily. Or they can be ignited with a BP igniter stick for the same reason.
What I don't know is what the typical lag between starter ignition and beginning of the thrust curve (motor pressure) is.
I think there is plenty of info on BP ignition delay including videos I have made where starter ignition is very clear due to using match tape, although I appreciate there are variabilities. I have a note to do the same next time I launch a Klima.
The launches I am looking at for now are low risk due to the set up, ie the outcome should not be problematic if there is a big delay with the composite.
I'm also thinking of trying an indirect ignition of the BP, whereby tape match is ignited from composite exhaust (close to the composite nozzle but not touching the starter), which in turn starts the BP so that any initial lag is removed. There would be limitations on how well this would work depending on the actual pressure lag, and until proven I'd only try it for launches where the model will launch fine without the BP (and obviously subject to RSO being happy).
Any thoughts greatly appreciated!
 

tfish

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No experience with what you're doing..
I'd set up a test ...one of each type of motors..attached securely to an up right and video tape the ignition sequence and timing..

Tony
 

Y3kankerous

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Thanks for the idea, definitely would be a good test. As i live in the city and my garden is fairly small I don't have the room for a static test (esp given the smoke chemistry in typical composites might do something untoward to my neighbours washing 😆😱), but will look into finding somewhere with a bit more space, including possibly getting to the range a bit early on a flying day...
 

heada

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I have done the APCP central motor with BP surrounding motors (29mm center, 4x 24mm surround) I used a standard starter for the central APCP motor and I used sections of "fast paper fuse" from each BP motor to below the APCP motor. The ends of the paper fuse are exposed to take fire well and to pass it into the BP motor. The fuse is taped into the BP nozzle and tied with cotton string below the APCP motor. The fast paper fuse is like black match or quick match but it is legal to own and use without a license in the US. If you have access to black match/quick match legally, I'd use that as it is better than the fast paper fuse I use.

I did that rocket by myself and so I didn't have to pass it by the RSO since I was the RSO. If you are going to do that at a group launch, I would talk to the RSO before starting to work on it and make sure they're OK with it first. Also, make sure your APCP central motor is reliable to start. A "chuff" could throw enough flame down to catch the match below it without fully starting the motor. CTI-like motors with the BP starter helps this alot but if not CTI, then any easy to light motor like AT blue should be fine. I also ensure that the APCP motor has enough thrust to give a safe flight by itself just in case the BP motors don't start.

This is the fast paper fuse I use. If you don't have access to black match/quick match, you could try to find something similar. If you're in the US, there are many places to find similar fuse online, this is just one source. The key is that it takes fire easily, burns very quickly and passes fire well.
 

Y3kankerous

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Bingo!!
That is exactly the method I was thinking of so it's great to know that this has been done successfully. The Klima tape match is basically a thin line of BP on sticky tape and ignites very easily then burns extremely fast, so should be identical to what you used.
The possible "chuff" problem is great advice, i wondered about something like that with sparks from the starter. Will think about match placement and maybe a paper cover that would keep off sparks but toast on AP ignition.
The cluster is 18 mm centre + 4 x 13mm boosters and first off I'm intending to try just two boosters using something tiny like a 1/4a3 which will really just be smoke with little impulse to test effectiveness.
Thanks for the advice and the vid link which I'll look at carefully and time index.
 

Rocketjunkie

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This is the fast paper fuse I use. If you don't have access to black match/quick match, you could try to find something similar. If you're in the US, there are many places to find similar fuse online, this is just one source. The key is that it takes fire easily, burns very quickly and passes fire well.

I have several speeds of these fuses. Unfortunately they have been out of stock for the last year :( They work as a Thermalite substitute. It does not speed up with sheathing like Thermalite does.
 

heada

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Rocketjunkie

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Dealt with them a lot. No problems. Can't order what is listed as not in stock. BTW, my testing indicates the fastest (white) burns closer to .4 sec/ft.
 

Y3kankerous

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Thanks guys, appreciate the info. For comparison, the Klima tapematch lists burn velocity as <0.3 s/m, so its comparable to the "ultra fast" match above. Given the distance is going to be a few cm max, hopefully its speedy enough to get to the nozzle before air flow kicks in and messes thing up.
 

Skyfall

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If you have directly Klima-related questions (on the construction of the motor itself) you surely can get in touch with them for clarification.
The owner (Mr. Klima) is a friendly, helpful and very knowledgeable person!
 

shockie

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Currently planning a couple of clusters where I would like to use a mix of Klima composite and BP motors, but am aware of the potentially longer ignition time on composites, meaning the thrust curve will have a lag compared to fast igniting BP.
Just to spell out what I think that means (in case I am not quite hitting the nail on the head)... if the composite and BP starters all ignited simultaneously from one electric supply (or tape match from a single electric starter), then the BP motors would achieve pressure and thrust earlier than the composite... which could have a few implications, for example if the BP early thrust peak gave enough of a kick to get off the rod, but didn't have enough plateau thrust then the model could take off but then stall and be non vertical when the composite thrust kicked in. Which might be "sub-optimal" 😯 Or with a bit of luck, the igniter might have pulled out of the composite before it took

I'm aware that Klima products have less availability outside Europe, so will be less experience to tap into but hoping someone may have some pointers, or possibly a vid. Had a search on the forum but didn't find anything specific to Klima.
My understanding is that, unlike many composites (but like Cesaroni), Klima motors have an integral BP charge which is ignited by the starter, meaning less considerations with ignition because the BP takes easily. Or they can be ignited with a BP igniter stick for the same reason.
What I don't know is what the typical lag between starter ignition and beginning of the thrust curve (motor pressure) is.
I think there is plenty of info on BP ignition delay including videos I have made where starter ignition is very clear due to using match tape, although I appreciate there are variabilities. I have a note to do the same next time I launch a Klima.
The launches I am looking at for now are low risk due to the set up, ie the outcome should not be problematic if there is a big delay with the composite.
I'm also thinking of trying an indirect ignition of the BP, whereby tape match is ignited from composite exhaust (close to the composite nozzle but not touching the starter), which in turn starts the BP so that any initial lag is removed. There would be limitations on how well this would work depending on the actual pressure lag, and until proven I'd only try it for launches where the model will launch fine without the BP (and obviously subject to RSO being happy).
Any thoughts greatly appreciated!
What Klima composite motors are you talking about? I thought they were all Potassium Perchlorate and sodium benzoate?

Is these what you are talking about?
 
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