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woodpekr · Posted: Thu Mar 04, 2004 5:14 pm Post subject: Ferrule length

I've got some Carbon tubes with a .2440 ID and I have some Carbon rod with a .2400 OD.

I'm going to join the tubes using lengths of the rod as an internal ferrule.

How long should they be?
If they're too long I have a bit of extra weight.
If they're too short maybe the tubes will disconnect under stress or even break through the wall of the tube. . .

Is there a rule of thumb or calculation?

Thanks --
_________________
Rich Durant
Portland, Oregon

Charles Bojarski · Posted: Thu Mar 04, 2004 6:27 pm Post subject:

Woodpekr:

I usually cut my ferrels, when I make them, about 3" long. I find that inserting the spars in about 1 1/2" works fine. The ferrels that Steve carries are all 3" long.

Hope this works.

Good winds....CharlieB

Spence602 · Joined: 16 Sep 2003 Posts: 352 Location: USA TX Houston

If you're worried about 3" being too short, or not strong enough, go for 4". Or 5", or whatever you feel comfortable with.

3" is the standard length of an external ferrel, especially in aluminum. But when you go with a small diameter internal tube or rod, you're losing strength based on wall thickness or just plain size.

3" of .2400 rod (solid CF) is plenty stong for in internal ferrel. (Almost all) SkyShark tubes have an ID of .244 and recommend an .240 OD rod as a ferrel.
_________________
Spence
www.kiteshark.org

Air: Refreshing when stirred up and served cool on a hot day.

KiteSquid · Posted: Fri Mar 05, 2004 7:56 am Post subject: Re: Ferrule length

stevef · Posted: Fri Mar 05, 2004 9:01 am Post subject:

I assume you are internal ferreling skyshark wrapped Graphite spars. If so, you will be fine with a three inch ferrel. If you are ferreling linear Graphite, I would NOT advise the internal ferrel. Linear Graphite is much better when coupled externally. of course, you can use BOTH and internal and external, but if you are only going to use one, go with the external.

-s
_________________
Steve Ferrel
Go Build a Kite!
Measure once, buy twice!

woodpekr · Posted: Fri Mar 05, 2004 10:57 am Post subject:

Thanks for all the info folks.

Yep! I have some skyshark tubes that I'm joining together.

I'm experimenting with some ideas for a quad kite frame and just wanted to have an idea for optimum ferrule length.

Thanks --
_________________
Rich Durant
Portland, Oregon