Hello all I am interested in using the pirhana line cutter but I need to know how many grains it uses in triple 7 powder so I can get it passed by safety in my company. Does anyone actually know if not could someone measure? Thanks in advance.
Pirhana Cutter
- Thread starter cbxc
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The Piranha cutter uses the cavity in the base of the cutter to measure the minuscule pyro charge. No weighing of the pyro powder is necessary or advised as the actual weight of the pyro powder is different depending on which pyro powder you are using. In this case, Triple 7 in the 3f granulation, when using the cavity in the cutting piston as the powder measure, weighs about 1.2 grains, not grams but grains. As I said, Quite minuscule.
-Cameron
OT but speaking of the Tinder Rocketry Improved Pirhana Line Cutter ...
They've been out of stock for a while, does anyone know where I can buy a set ?
Thanks !
-- kjh
They've been out of stock for a while, does anyone know where I can buy a set ?
Thanks !
-- kjh
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Look again late this week or the first of next week...
Thanks, Cameron !
I sure will !
-- kjh
I sure will !
-- kjh
Hey William,
Production has begun, yet they are still not back in stock on the website and still may not be for another week.. I have been sick so I am moving quite slow. I have however finished 8 pair (4 kits) and am offering to those that ask. 1 set ships today. Send me an email if you are interested...
Hope you're feeling better @Cameron Tinder
I already exceeded my monthly allowance for March so I'll save the 1st run for others but I'll check again next month.
Thanks
-- kjh
I already exceeded my monthly allowance for March so I'll save the 1st run for others but I'll check again next month.
Thanks
-- kjh
Rschub
Well-Known Member
Well, let's see if I can beat the geezers on this one. 
E-mail sent
Edit:
E-mail sentEdit:
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Got it, thank you! Should ship today!Well, let's see if I can beat the geezers on this one.
Edit:
Rschub
Well-Known Member
Thanks! Best wishes for a speedy recovery.
Thank you! If I could dump this head ache, I'd be good as gold!
Hope you get to feeling better!
@Cameron Tinder --
I am about ready to start building Hedley Babar which is designed around a pair of your Improved Piranha Line Cutters.
Do you think they'll be available later this month ?
Thanks !
-- kjh
I am about ready to start building Hedley Babar which is designed around a pair of your Improved Piranha Line Cutters.
Do you think they'll be available later this month ?
Thanks !
-- kjh
Rschub
Well-Known Member
I did receive my set, they look really good and I am excited to try them out on an upcoming project.
So...
Another guy on this thread wrote to me wanting the last pair of Piranha cutters. I offered them to him but I mentioned that another guy on TRF also wanted a pair for a project that was fast approaching. When he found out it was you, he most graciously "bowed out" and has allowed me to offer them to you. (Thanks Stephen!) So, if you are interested, let me know here and send me your email address so I can get these out to you!
--Cameron
@Cameron Tinder --
The pair of Piranha Line Cutters arrived today -- GREAT turnaround time !
They're packed nicely in a beautiful little box.
I can't wait to run a ground test and then actually fly them in "Hedley Babar" and also in a few old rockets without a payload bay !
Thank you and thank you to @bad_idea !
-- kjh
The pair of Piranha Line Cutters arrived today -- GREAT turnaround time !
They're packed nicely in a beautiful little box.
I can't wait to run a ground test and then actually fly them in "Hedley Babar" and also in a few old rockets without a payload bay !
Thank you and thank you to @bad_idea !
-- kjh
jgarbus
Active Member
So is the idea with the line cutter to throw out the entire recovery package at apogee and contain the main with the cutter? Do you just tape the ematch wire to the harness to keep them from getting tangled?
@jgarbus --
I am no expert -- in fact I'll be building my first HED rocket soon: It's Hedley, Hedley Babar !
But, yes, that is the general idea: kick out the main in a wrapped bundle, maybe along with a drogue and then use the line cutter to release the main at a reasonable altitude.
If you're familiar with the JLCR, it is conceptually the same idea except that the line cutter is fired by the main channel on a dual deployment altimeter / flight controller.
Yes, with a little strain relief ( tape the ematch leads with a few humps so the shock cord takes the jerk.
There are a lot of threads here on TRF with details and better explanations than I could provide
HTH
-- kjh
jgarbus
Active Member
Never thought to compare it with a JLCR. That makes sense@jgarbus --
I am no expert -- in fact I'll be building my first HED rocket soon: It's Hedley, Hedley Babar !
But, yes, that is the general idea: kick out the main in a wrapped bundle, maybe along with a drogue and then use the line cutter to release the main at a reasonable altitude.
If you're familiar with the JLCR, it is conceptually the same idea except that the line cutter is fired by the main channel on a dual deployment altimeter / flight controller.
Yes, with a little strain relief ( tape the ematch leads with a few humps so the shock cord takes the jerk.
There are a lot of threads here on TRF with details and better explanations than I could provide
HTH
-- kjh
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I had an arrangement to purchase a pair from someone, but after he accepted my offer, came back and told me that he sold them to someone else. Looks like I've missed out on my chance at getting a pair.
Cameron told me more are coming soon.
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I hope so.
Hi Cameron, Had a chance to use the line cutters this last Saturday. One ground test and one flight test. Both worked great. However, I wrapped up the chute in a Nomex blanket held closed with a zip tie. At deployment I could see the cutter fire but the chute never came out from the "burrito". Upon examination, the cut portion of the zip tie was still wrapped around the nomex loosely preventing chute release? Additionally, when I cleaned the line cutter, a small piece of the zip tie had worked its way past the "piston" and was found in the lower part of the cutter. Is this normal??
One last thing, what is the black cord, included in the box, intended for?
Great product thank you very much.
William
Hey William,
When the cutter cuts the zip-tie or cord, it does indeed cut and stuff a portion of what the piston cuts into the cutter itself. This is normal and intended. The brown cord packaged with the Piranha cutter is waxed cotton cord intended to be used instead of the zip-ties. Unlike the nylon zip-ties, the cotton cord is quite bio-degradable. Also, when ingested by wildlife, cattle or horses, the cotton cord is a bit more digestible than the nylon zip-ties. This is especially important if you fly on grass or alfalfa fields that will be made into hay or fields that horses or cattle feed on. I changed this when it occurred to me how many of these zip-ties I was sending out in the kits and realized that a lot of flyers fly on these sorts of fields. I would hate to hear about the loss of livestock and quite possibly the loss of a launch site as a result of this sort of thing!
That is a VERY thoughtful change, @Cameron Tinder !
I see in your Video: Improved Piranha Dual Mason Twine Constrained Parachute Simulation that you wrapped the chute + protector like an old-timey package and the twist passes thru the line cutter.
Is there any more to it than that ?
Thanks !
-- kjh
To be perfectly honest with you, I do not fly this way. It's either all out at the top (Low flying typically H motors) or tether and release, historically with the Tender Descender and now exclusively the bolted TD-2. So, really, I can only tell you what I THINK not what I have done in regards to using a "burrito wrapped" chute and a Piranha cutter to release it.
Yes, I THINK that I would wrap the chute like an old time package and release with the cutter. The up side to using a cutter compared to the JLCR is the thing can be cinched down pretty tight.
I will defer to others on this as to the BEST way to do this type of recovery.
---Cameron
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Hi All,
Jenni and I fly with burrito-wrapped mains in a dual deploy / single opening configuration on almost every rocket we fly, from 2 inch to 4.5 inch. Make a burrito with "wings" out of nomex (so kinda like a fat cross shape) and bundle the main and some extra harness into that and secure with a Mako (3 or 4 inch on up) or a piranha (2.5 inch and down or lighter 3 inch rockets). We have had only one failure to get a full main when a chute with very "fuzzy" nylon shrouds snagged on the sharp edge of the zip tie preventing a full main inflation.
It's easy to have full redundancy as well by running the same ziptie or cord through 2 units. We use either electrical tape or heat-shrink around the ematch wires and the harness together to make an umbilical that goes from the Av-bay to the units. Be sure to secure a Mako to the harness with something. The ematch wires won't keep it (Cameron probably wonders why I have bought so many of those!). The piranhas are so light, they stay on the ematch lead.
Try to get the burrito-wrapped main as close to the Av-bay as possible to prevent twisting during the descent, especially for flights where the descent will take a while.
If you are going above 30K ft, make sure your cord or ziptie can take -70degree temps without shattering. Found that one out the hard way.
John Etgen
Jenni and I fly with burrito-wrapped mains in a dual deploy / single opening configuration on almost every rocket we fly, from 2 inch to 4.5 inch. Make a burrito with "wings" out of nomex (so kinda like a fat cross shape) and bundle the main and some extra harness into that and secure with a Mako (3 or 4 inch on up) or a piranha (2.5 inch and down or lighter 3 inch rockets). We have had only one failure to get a full main when a chute with very "fuzzy" nylon shrouds snagged on the sharp edge of the zip tie preventing a full main inflation.
It's easy to have full redundancy as well by running the same ziptie or cord through 2 units. We use either electrical tape or heat-shrink around the ematch wires and the harness together to make an umbilical that goes from the Av-bay to the units. Be sure to secure a Mako to the harness with something. The ematch wires won't keep it (Cameron probably wonders why I have bought so many of those!). The piranhas are so light, they stay on the ematch lead.
Try to get the burrito-wrapped main as close to the Av-bay as possible to prevent twisting during the descent, especially for flights where the descent will take a while.
If you are going above 30K ft, make sure your cord or ziptie can take -70degree temps without shattering. Found that one out the hard way.
John Etgen
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I have seen quite a few do it that way. That is a great way to have redundant with a cutter.
I see these used less with the Jolly Logic coming out, but I still think it is a great option.
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