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rev-spars = precision spars???


chewbaka
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hi folks,

i do not know why, but some weeks ago some guys from germany startet

to weigh their rev-spars out.

we had to see, that the spars have tolerances up to 5 grams (3-wrap).

but, i was shocked, when i saw the pictures of an experiment

that one guy made.

he tested the "deflection" of 2-wraps. i do not know,

whether "deflection" ist the perfect technical term, but the picture

will show you what i mean.

here it is:

3.jpg

the used weight on both spars is exactly 625 grams.

the outer diameter of the front spar is 7.3 mm, the back spar is 7.45 mm.

the weight of the front spar is 12 grams, the back one weighs 15 grams.

seeing the weight, i considered the front spar to be a "race rod"

with wrong sticker on it.

i think, if one buys a kite like the 1.5 "b-series" including such spars, these tolerances are not acceptable!

give it a try!

check your spars!

please excuse my bad english! i have to come to the states

and exercise a little. (speaking and flying) ;-)

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I see what you mean, afraid when the mood takes me I am too busy flying to test my rods :-)

There have been many discussions about variences in the rods.

I just tend to think that making the rods to super fine tolerences would need super expense.

My Revs fly well enough for me thanks.

Not that I am trying to dismiss your tests of course. Interesting, thanks.

Edited by Baloo
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I just tend to think that making the rods to super fine tolerences would need super expense.

Not necessarily, it takes an understanding of the places where variation can come in, and so a detailed knowledge of the manufacturing process, which I don't have.

The issue is keyed on the variation in thickness, which is small (~1.5 in 70 in this case, though hardly statistically significant). Is this additional resin, or thicker carbon fibre? Variation in the carbon would presumably change the stiffness, which should be one of the parameters we really care about. This could easily be the fault of the incoming material, nothing in the control of the factory. Tighten up the incoming material spec and the problem is reduced (though the supplier may charge more).

If it's variation in the manufacturing then is it a person to person variation, a tool to tool one, or random because the operations are not precise enough? All of these issues could be quantified reasonable easily with appropraite tracking of parts and end of line measurements. Get in a Six Sigma blackbelt consultant and this could be fixed, possible with little longterm cost, and maybe a reduction is scrap (depending on what Revolution do to test spars and how many fail the test).

Too often people say quality costs, but it is the lack of quality that costs. Of course this could all be a mute point if no-one can tell the difference.

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I guess the real question is how big of a difference in weight, deflection, stiffness... etc can be found in similarly priced wrapped carbon kite spars and arrow shafts? If similar variances are found across the board than the argument is mute... if not than the argument is valid...

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This makes me think about matching microphone pairs. In the studio, if you want a really good stereo recording of something live with microphones, you get a matched pair. Higher-end microphones are tested to find out what their true responses are, and two are closely matched in order to sell as a matched pair. They're not made to match- they're manufactured to be within a certain set of tolerances and characteristics. They're tested in order to find matches in very closely similar characteristics

This could be done for rev rods as well. I don't think it would matter so much is you're flying individually, but in a team, you might want responses between rod sets to be as close as possible. Or, for individual competitors that want their rod sets to perform as similar as possible (say, I've got a B-series Pro with a race rod frame and a backup frame, I'd want the backup frame to perform as close as possible to my other frame). Or not- :) flying Revs is about constant and minute adjustments to your environment and changing wind conditions... at least it is here in central Texas! LOL But if it matters that the sail is made to exacting measurements and tolerances, and your line set needs to be stretched and balanced, and your handles are fine-tuned- should your frame be consistent as well? If there's no consistency between rods in the leading edge, then did you hurt your accuracy?

Maybe testing after the rods are manufactured could be done- yes, it will add to the costs, but probably not near as much as improving the manufacturing tolerances. Come up with a specification of allowable deflection, and a color code for three deflections on each type of rod (2-wrap, 3-wrap, race, etc). So, if you buy a 2-wrap red rod, then you know you're getting a Rev rod that defects only so much within a certain acceptable range for a 2-wrap, a white rod will deflect more, a blue rod will deflect the most (like the red-white-blue code? :lol: ). And if you don't care, buy the lower-priced unmarked rods.

Just some random thoughts...

Edited by dagnabbit
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I'm not sure price would really be an issue, the 'std' rev rods sell for 50% more than skyshark here in the UK, and I've bought skyshark wholesale for 1/4 of it's current retail price in the last year. There's a fair markup somewhere :-) and a 10% increase in manufacturing costs could probably be absorbed along the supply chain somewhere.

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hi folks,

i do not know why, but some weeks ago some guys from germany startet

to weigh their rev-spars out.

we had to see, that the spars have tolerances up to 5 grams (3-wrap).

but, i was shocked, when i saw the pictures of an experiment

that one guy made.

he tested the "deflection" of 2-wraps. i do not know,

whether "deflection" ist the perfect technical term, but the picture

will show you what i mean.

here it is:

3.jpg

the used weight on both spars is exactly 625 grams.

the outer diameter of the front spar is 7.3 mm, the back spar is 7.45 mm.

the weight of the front spar is 12 grams, the back one weighs 15 grams.

seeing the weight, i considered the front spar to be a "race rod"

with wrong sticker on it.

i think, if one buys a kite like the 1.5 "b-series" including such spars, these tolerances are not acceptable!

give it a try!

check your spars!

please excuse my bad english! i have to come to the states

and exercise a little. (speaking and flying) ;-)

Hi Chewbaka,

I would only worry if B) everyone else was doing this or B) when you check other rods and they are better.

I fin the wind changes take away much of teh varience in rods. An dsewing tolerances by anyone and cloth differences adn line stretch etc etc.. And most imprtat of all the person at the end of the line and there ability.

If I had enough rods to check then I would match my rods, because I'm the kind of person who would.

I would also tie all the bridles and do all the lines and ensure all team flyers use identical leaders on thier handles.

(OK so on the Blasts, I've done the bridles, we have identical Leaders & I did about 6 or 7 sets of lines... Just off to check the rods :) )

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Spill chuck?

Felix

Hi Felix, Thats nothing... Today at work I got a coffee grain under the letter a on my keyboard. Still had loads of stuff to write. So it went our with no A's. I reckon everyone knows I'm a dumb ss nywy :) <Grin>

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Tiz easy enough to read if most of the letters are in there anyway. Blasted computers, why dont they know what we mean for goodness sake? Oh I forgot, the predictive spelling thing, they do know what we meant a lot of the time!!

A worrying world we live in, come on the Terminator!!

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