An interesting conversation........................
From: George T
Sent: Tuesday, January 28, 2014 6:28 PM
To: Ted Chernok
Subject: RE:
Teddy,
Just wanted to get your opinion, I got the 1/2" Kevlar shock cords for a 4" rocket which I think will easily go 15 pounds.
Will the 1/2" be enough or should I go up to something like the 9/16 tubular nylon?
Thanks,
George
George,,, Good question,,,,,,,,
First,,,,
Everybody in The Radical Rocketeers ( my home club ) pokes fun
at me cause I build so heavy,,,
they say I'm building another tank...lol...
You say 4" and 15 lbs on the pad,,,,,,,,,,
I had a very large,,, very long,,,, 3" rocket that was 16 lbs on the pad.....
Now,,, that said,,, the 1/2" Kevlar in my humble opinion,,,,,,,
a 15 lb rocket,,,,, yes,,,, no problem at all,,,,
but I wouldn't go all that much heavier then that.........
Please be aware,,,,, these cords do wear,,,,, they do not last forever,,,,,, if you fly one rocket A LOT,,, all year,,,,
10 or 12 flights,,, with the same cords,,,
you'll see wear at the end of the year......
not enough to retire the cord ,,,
but you'll have a feel for the cords lifetime......
The heavier the rocket in relation to the cord the faster
the cord will wear,,,, the more load it's taking,,,,
the more echarge it's tolerating.......
Now,,,,, you asked 9/16" tubular nylon,,,,,, I flew that last year A LOT.....
Kevlar,,, pound for pound is much stronger then nylon,,,,,
or anything else for that matter.........
but it doesn't give at all,,, none,,, zilch,,,,,,
that's why we like the bit of give you get from nylon,,,,,,,
the problem is that an echarge will
burn up a nylon cord in 1 flight.........
This is my solution,,,,
https://www.ebay.com/itm/141174522000?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649
I flew one of these all year last year,,, I loved it,,,,, worked fantastically,,,,, there's one drawback,,,, ( you didn't think this was the perfect answer did you,,, lol,,,)
The sleeved nylon is a bit cumbersome and bulky,,, I flew this in a 54 mm airframe,,, my Altitude Seeker,,, on the bottom,,, in the booster,,,, it made things a bit tight,,, but doable ,,,,
Be aware,,, this example is 1/2" tubular nylon and a 1/2" tubular Kevlar sleeve.....
I have gotten the 9/16" white tubular nylon into this same sleeve,,,,
it's just difficult to do ,,, but it will go,,,,, These cords that have gone out,,,,,, people have raved about,,,,, they loved them,,,,,,
I sent one to Dan Patell,,, he was going to give it to his pop,,, and to Les too if I'm not mistaken........
But anyway,,, if you compare the same weight / size nylon and Kevlar,,, the Kevlar will be stronger,,,
I know this is a lot of information George,,,,
but to be honest,,, at 15 lbs,,, your on the cusp,,,
you have many options open to you..........
That's a good place to be,,,,,,,,,,,,,,,,,,,,,,,
Anytime I can help George,,,,,
Teddy
George,,, this reads pretty cool,,,,,
I hope you don't mind if I post this....................
