Recommendations for places for (and kinds) of replacement kite spars

RJoe

Is their a consensus on Carbon Fiber or Fiberglass? And do people favor rods or tubes?

broox

In the USA, www.kitebuilder.com is a good source; another is Kites & Fun Things in Michigan. Fiberglass rods are flexible and nearly indestructible; carbon tubes are much stiffer, lighter, and more brittle (prone to breakage).

MNkiteman

Are we talking solid fiberglass rods, or tubes? Fiberglass tubes are best suited for crosspars.
Solid fiberglass rods are heavy and while they do have there uses in kite making I would avoid them if possible.

timonoko

Carbon fibre rods are easy to make. You just take dozen carbon filaments and pull them trough wet epoxy and hang them from the ceiling. The gravity makes them straight and perfect. I have cheap 3 kilo roll of raw carbon filament from russia, hence this activity makes totally sense.

As regards to carbon's brittleness, yes it is. But if you tie 3 rods together 5 millimeters apart with loosely spaced strands of carbon fibre you'll have superior stiff construct, possibly a crossbar.

Or a bicycle frame:
http://blog.makezine.com/archive/2008/03/carbon_cthru_bike_frame.html

pitprops

Carbon is relatively expensive here in the UK, and agree it is brittle and relatively stiff. Fibreglass is relatively heavy and sometimes too flexible. Natural materials (dowel and bamboo can be inconsisten in their flexibility. But all have their place. I tend to use dowel for large kites where little flex is required. Carbon where weight is an issue, and very rarely will I use fibreglass. For temporary replacements, I always have a couple of lengths of dowel and a small saw in my bag so I can effect mergency repairs to keep me flying if I have to. For sports kites, I carry spares for the parts most likely to break - lower leading edge and lower spreader.

RJoe

Broox - Thanks for the tips and links.

Timo - out of curiosity where did you buy your 3 kilo roll? Was that something like this.

Pitprops - does the dowel give you enough flex to use in something like a Dopero where you have a need for a bit of flex?

pitprops

Depends on the diameter, but I've had no problems with it in 2m rokkaku.

Wind Watcher

My recommendation is work with kite builder and use P-400 Sky Shark carbon tubes.

saF

I agree with Wind Watcher. I have a 6 foot Rok that I initially framed in fiberglass for the spreaders and carbon for the spine. It is what my friend Bill had on hand when I was building it. I think Bill had a bundle of fiberglass tubes that were defective, as I had to replace the same section twice before I finally switched to Sky Sharks (P-400's I think).

A lot depends on the quality of the fiberglass used to make the tubes. Did the manufacturer decide to scrimp and use more resin to save on the more expensive fiber? The fiberglass tubes tend to splinter lengthwise, while carbon tends to snap off cleanly, making it easier to fix with an internal ferrel (usually a carbon rod).

Hope this helps a bit.
saF

tcope

100% depends on what you are using them for/how you are going to use them.

David Wheeler

Since it hasn't been mentioned yet, I think it's worth pointing out that there are two types of carbon tubes: extruded and wrapped. The wrapped ones are less prone to breakage but are more expensive. The skyshark tubes mentioned above are wrapped. My dopero 100 and 60" Rokkaku both use skyshark tubes and none have broken. My 78" Premier Rok, on the other hand had non-wrapped spars and they've split at the ferrule a couple times. I'm in the process of replacing those with Skyshark P400 and P200 tubes.

broox

It is possible to reinforce the intersections of tubes of any kind by wrapping with simple plastic electrical tape. Glen and Tanna Haynes have taken reinforcement to a high art by using fishing rod wrapping techniques to apply elegant thread wrappings to the spars of their award-winning kites.

Wind Watcher

I agree with Broox, I use the skyshark P400 wrapped carbon tubes plus use black gorilla tape near the ferrule points. These sticks have taken a beating in high winds (with Dopero) and have not broken.

RJoe

First off a nod to Wind Watcher and Gorilla tape. I can not say enough great things about this tape which is as strong as what we imagine duct tape should be. The glue they use on there is mighty impressive. If you have ever seen it for sale and stopped short of buying it, go ahead and get some, you will love it!

2nd - I see that there are a number of variations on Sky Shark tubes. As an example: P400, P300, P200 etc... Can anyone provide a tip as to why, for example, a P400 is better than a P300. If one were to use a P300 instead of a P400 is that catastrophic? When looking at descriptions of the characteristics the description for each of these tubes reads identical (except for ID and OD) and so it is a bit confusing.

For SkyShark P400

Length = 32.5"
ID = .244"
OD = .298"
Weight = 18.0 grams
The New Sky Shark™ Straight Competition Air Frames combine exceptional stiffness and light weight. These tubes can be cut and ferruled anywhere using a solid carbon rod (RSG24 works best). They can also be ferruled with any of the New Tapered tubes except the 2PT. These tubes work great for building sport kites as well as single line kites.

For SkyShark P300

Length = 32.5"
ID = .244"
OD = .292"
Weight = 17.0 grams

The New Sky Shark™ Straight Competition Air Frames combine exceptional stiffness and light weight. These tubes can be cut and ferruled anywhere using a solid carbon rod (RSG24 works best). They can also be ferruled with any of the New Tapered tubes except the 2PT. These tubes work great for building sport kites as well as single line kites.

For SkyShark P200

Length = 32.5"
ID = .244"
OD = .284"
Weight = 14.5 grams

The New Sky Shark™ Straight Competition Air Frames combine exceptional stiffness and light weight. These tubes can be cut and ferruled anywhere using a solid carbon rod (RSG24 works best). They can also be ferruled with any of the New Tapered tubes except the 2PT. These tubes work great for building sport kites as well as single line kites.

And when looking at tubes from other vendors in their different sizes but of the same type (i.e. wrapped), how does one compare apples to apples? Is it all in the ID and OD?

Thanks!

broox

What those ID and OD numbers tell you is that the walls are of different thicknesses. They can all be spliced with internal ferrules of .2400, but the thicker walled spars are going to be stronger, and the thinner ones lighter.

Wind Watcher

RJoe, I agree with Brooks. The P200-400 are all the same ID but different ODs (wall thickness) and weight. In my eye all of these sticks are very light, flexible and strong. I selected the P400 as they are the thickest, stongest and the weight is more than acceptable. I would even go for P500 or P600 if they had it. Kite Studio sells the sticks and the .240 ferrules. A fine tooth hack saw, a bit of crazy glue, plastic tips for the ends and some of that black gorilla tape are all you will need.

David Wheeler

Besides being stronger, the higher number skyshark tubes are stiffer. That's why, for example, you'll see people frequently recommend a P400 for a rokkaku's spine but P200's for the spreaders.

pitprops

The numbers refer to the number of wraps of carbon as these are wrapped tubes rather than pultruded. As said before, bigger numbers mean thicker wall and stiffer/stringer tube. All are wrapped onto a standard jig, so the internal diameter is always the same.

RJoe

Why would you want a more flexible spine than a spreader? Does it have to do with the dynamics of how a kite contorts in the wind?

Dave Mitchell

It's the other way round, RJoe. You want the 'wings' of the Rok to flex (by having a more flexible spreader) , but not the spine, since that would make the Rok turn from an 'aeroplane' shape into a 'dish' shape (with a corresponding loss in aerodynamic lift).

sdunn

The Kite Studio description says "These tubes can be cut and ferruled anywhere using a solid carbon rod (RSG24 works best)." I've only seen ferrules where spars fit into short steel tubes.
So tubes vs. plugs: which is better?

If taking the plug approach, what rod length would be advised?

broox

"Best" depends on the spar. Few thin-walled spars use outside ferrules because the spar can split easily under bending compression. The best would be a rod inside on one section and a sleeve outside on the matching section, but that's seldom done.

With pultruded carbon, use external tubes.

1.5 to 2 inches of ferrule overlap on each side is usually enough; i.e., make your ferrules 3 to 4 inches long for a modest sized kite; longer for a big one.

Many use superglue for ferrules, but I prefer 5 min epoxy. For a stronger joint, wrap the last inch or two of the section with the male ferrule with plastic electrician's tape, duct or gorilla tape, or most elegant, fishing rod thread & glue. See above discussion.

http://www.brooxes.com/

sdunn

Thanks Brooks! Much clearer now.

Now that I'm digging into this I thought about making a set of travel spars. The idea is to make a spar kit small enough to fit in my luggage. Here I would end up with 5 ferrules on a single spar instead of two. I realize that this is adding more weight. It's also going to make assembly more complicated. Are there other problems associated with using this many ferrule points?

broox

It would of course stiffen the spar, but the Magic Delta of Jerry Sinotte years ago was a 16 ft kite that folded into a 2-ft case and flew like a champ. I wouldn't worry about it.

You might steal an idea from Jerry, though: run a piece of round elastic cord through the spar from one end to the other, like some tent poles. Then the sections can fold without getting separated and lost. I've done that with a Dopero very successfully.

sdunn

Jim,
I'm assuming you're using the P400 for all 4 spars on the Dopero? I ask because the stock configuration has a single thick cross spar at the top with the remaining 3 spars made of a much thinner carbon tube and wondered if it might make sense to replace those 3 with a lighter spec.
Scott

KappinChina

This is really great information!

I have a question, which has more flexibility, fiberglass or carbon? I am looking for something thin, light but very sturdy and stiff

broox

Fiberglass has much more flexibility; carbon is stiff but brittle. Depends on your use which you pick. Suggest you search this forum for other threads on the subject; there's been lots of discussion here. Better yet, www.kitebuilder.com is full of advice.

Wind Watcher

Scott, I use the P400 spars for the main horizontal cross spar on the Dopero and I have continued to use the stock spars for the lower horizontal (thiner) cross spar. Hope that helps.

sdunn

Thanks Jim. It does help. Sticking with stock spars for 1 lower horizontal and the 2 verticals makes the modification much easier.

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