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Progcraft · Posted: Mon Oct 27, 2003 2:59 pm Post subject: Line strength

HI All.
When it comes to flowforms of 2 square meters to 10 square meters, how do you determine the size of line you will need to fly it? Say for example useing the FF04A or FF03A plans from Harry Prinzler?

Thanks
P.

stevef · Posted: Mon Oct 27, 2003 4:21 pm Post subject:

I have two general formulas:

1. The flying line should have a breaking strength of about three times total area in square feet, times 1.2 (add 20% 'just in case')

2. Line strength = (1/5 x surface area in square feet) x (Maximum wind velocity in mph) x 1.2 (add 20% 'just in case')

I usually go by #1 just because it is easier. Remember, this is just a general guideline. Other things come into play, like wind conditions, age & quality of line, number of knots, type of kite, attached line laundry, etc....
_________________
Steve Ferrel
Go Build a Kite!
Measure once, buy twice!

Spence602 · Joined: 16 Sep 2003 Posts: 340 Location: USA TX Houston

stevef · Posted: Mon Oct 27, 2003 5:21 pm Post subject:

knew that might be confusing! Wink

Those formulas were in some magazine I read a long, long time ago....and are very basic quidelines, which I use as a quick reference when customers call on the phone. I usually go by the formula and then add my "gut feeling" Smile

As an example:

A six foot Rokkaku is usually about 25 sq. feet. That would mean (by he first formula) that the minimum line would be 90 pound. (25 x 3)x1.2. But I usually round up to 100.

The second fomula in a 10mph wind would give you minimum line of 60 pound... rounding up to 80.

I have flown a six foot Rok on line ranging from 50 pound to 250 pound - depending on circumstances...

So Prog, I'd probably say use a minimum of 80 pound on the 2 and 300+ on the 10. But of course it depends on the winds and if anything else is on the line....
_________________
Steve Ferrel
Go Build a Kite!
Measure once, buy twice!

Progcraft · Posted: Mon Oct 27, 2003 6:37 pm Post subject:

Thanks Steve. That's an interesting formula.
Thanks Spence. I appreciate the metric conversion there.

Now another question. Is 3/16 or 1/4 inch braided nylon rope a good choice? Or perhaps Polyethylene rope?

P.

KiteSquid · Posted: Tue Oct 28, 2003 8:51 am Post subject:

The perfect Kite Line for Single Line Kite’s (SLK's) would have some elastic factor and be infinitely strong and infinitely small in diameter to cut down on wind resistance.

But you need to be able to handle you line. So it needs to have some diameter.

For most SLK's I like to fly on Braided Polyester or Nylon.

Polyester is strong, lightweight and is small in diameter to cut down on wind resistance. And it does not dry rot. It is usually a little more expensive than nylon. It is lighter than nylon so if you have to carry your kites a lot or to take them on commercial aircraft, I would recommend Polyester. Polyester is hydrophobic, so on wet days it does NOT get heavier, see Nylon...

Nylon has quite a bit more elastic property for gusty winds. It is kinder on your anchor point and your kite. It dampens the hammering that can take place in gusts. It also gives back some of that stored energy went the wind slacks, to keep your kite in the air. It is also available at most hardware stores but buy braided not twisted nylon as you don’t want to put a spin in you line and the braided is easier to handle than twisted line. It costs more to make so you pay a little more for it. Nylon has up to 50% stretch and it is hydrotropic so on wet or humid days water vapor or droplets will bond itself to the nylon fibers making them heavier and streatchier, as well as your Nylon kite...

Polypropylene is not a good choice for Kite Line as it is usually hard to handle as it is stiff, and it has a low strength to weight ratio. It has low stretch (does not absorb shocks well), but it does float on water (that is why water skiers use it)

Spectra and Kevlar line.... I would not recommend them UNLESS you are going for an altitude record as they have only about 2-3% stretch. They have the highest strength to weight ratio of any of the lines so they will be thin (low wind resistance) and did I say expensive???

Spectra is EXPENSIVE and has a low melting point, so someone with a $1 kite on twisted cotton line will cut your $1 a foot Spectra line faster than you can say "OH NO!!"

Kevlar is abrasive to everything it touches it will cut you so fast it is not funny.

I came across a roll of Polyester sheathed Kevlar Halyard line on the cheep as it was last year’s line and it was not needed. It is 3/8" diameter and has a breaking strength of over 8,000 lbs. I flew a 252 on it once and will never do it again. This was a $400 roll of line I picked up for a lot less. It is hard to handle (Stiff) and it has NO bounce...

After saying all that, my preference for all my SLK's (except fighters) is Braided Polyester line.

I try to have a lot of different diameters as you never know what the winds will hold for you...

Boy did I stand on my electronic soap box for quite a while...
_________________
VR/
KiteSquid
AKA TakoIka
AKA Harold
King George VA

P.S. Yet another post by the Squid..... Shocked

Doesent he ever shut up???

P.P.S. The wind is like the air, only pushier.

Progcraft · Posted: Tue Oct 28, 2003 9:34 am Post subject:

That is most excellent info Harold. You have answerd many other questions I had as well. Like stretch.
You've made this alot easier for me.

Thanks mate.
P.

KiteSquid · Posted: Tue Oct 28, 2003 3:48 pm Post subject:

Just remember about posts from me...

I usualy come off the top of my head and don't use refrence books to look up numbers so they may be off... unless I give the refrence.

I am totaly unbiased Laughing

I am frequently incorrcet. My wife tell me that I frequently take artistic license when quoting numbers (she is a CPA)...

You should always go to some refrence book to look up details for the above reasons if it is critical to the application.

I dont intentanly steer people wrong, but sometimes I am incorrect.

Glad I could help.
_________________
VR/
KiteSquid
AKA TakoIka
AKA Harold
King George VA

P.S. Yet another post by the Squid..... Shocked

Doesent he ever shut up???

P.P.S. The wind is like the air, only pushier.

stevef · Posted: Tue Oct 28, 2003 4:50 pm Post subject:

yep, good info squid.... prog, for your reference:

Solid Braid Polyester = 1/4" diameter = 1,100 pound strength
Solid Braid Polyester = 3/16" diameter = 700 pound strength
Solid Braid Polyester = 1/8" diameter = 450 pound strength

Those are 'conservative' spec's on the line that Kite Studio stocks. You can view them in the catalog here:
http://www.kitebuilder.com/catalog/index.php?cPath=30_71

Let me know if you find it anywhere at a better price.....
_________________
Steve Ferrel
Go Build a Kite!
Measure once, buy twice!

Progcraft · Posted: Tue Oct 28, 2003 5:04 pm Post subject:

Oh, you do have line like that. I couldn't find it through the menus on KiteStudio.

As for cheaper, well, there is a guy who runs an EBay store which is a bit.
3/16 X 500' = $18.50.
1/4 X 1000' solid braid = $52.00

He has tons of variety of rope and even lists the strength of each one. I only found this last night. (I'm gong to get in trouble now arent' I)

Pl