Source for Carbon Rods?

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DaveD

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May 28, 2010
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I'm a bit late to this thread, but for those of you not in the US, DPP Pultrusions (in the Netherlands) will ship worldwide. I brought pre cut lengths to make some trial parts but they indicated they can supply long lengths on a spool on request.
They weren't cheap though, and this was a few years ago... but I did have to factor in shipping to Australia!
 

howardyin

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May 23, 2020
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I just ordered 1000m of 2mm (0.079") x 5mm (0.197") carbon flat. We can talk prices in depth after we get test results on strength and stiffness. But preliminarily I'd be pleased to get $75 per 100 feet for it. Because it has only 75% of the cross-section of the .22 x .092 profile we used to get a free ride on, expect to order at least 33% more to get the equivalent cross-section area.
hi, Boku, would you please paste the contact info of this company? thanks
 

peter hudson

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May 24, 2020
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OK, thanks for the (very interesting) explanation. I had assumed you were referring to dynamic bending in plane, not layout/layup - thus of course round makes perfect sense.

Now come the questions: is the forward sweep for aerodynamic reasons or CofG? With bent in horizontal plane layout at roots, it sounds like a one piece wing? Expected a sailplane to have removeable x 2 for recovery from off-airport landings.
it will be pretty traditional tongue in fork, two-pin sailplane like wing joint but the spar stubs still need that bend.
 

Hot Wings

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it will be pretty traditional tongue in fork, two-pin sailplane like wing joint but the spar stubs still need that bend.
Thread drift:

Rather the T+F have you considered a 3 pin? I know it would make the fuselage spar box a lot heavier but the weight saved by not having to deal with the 'peel' force on the spar webs due to the bends in the spar caps might save weight overall - and - simplify construction?
I've built one spar with round rods that bent in only one plane over a quite large radius. Keeping them in place during cure was not an insignificant problem.
 

BoKu

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thanks you the same :)
To expand a bit on my earlier post: I invested a fair bit of time identifying suppliers, obtaining samples, and testing materials properties, and I undertook a fair bit of risk by placing orders for relatively large quantities of material. Socialist at heart that I might be, I still intend to get a return on that investment. I mean to take a smaller bite than Goodwinds/Diversified, but certainly not nothing.
 

sming

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Apr 10, 2019
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Well not to defend him, and i could be wrong, and I also support BoKu position, but i believe howardyin is chinese (and in china?), so just from a practical point of view it would be pretty inefficient to order chinese pultrusion from the usa ;)
 

peter hudson

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May 24, 2020
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Thread drift:

Rather the T+F have you considered a 3 pin? I know it would make the fuselage spar box a lot heavier but the weight saved by not having to deal with the 'peel' force on the spar webs due to the bends in the spar caps might save weight overall - and - simplify construction?
I've built one spar with round rods that bent in only one plane over a quite large radius. Keeping them in place during cure was not an insignificant problem.
To help the thread drift back into the right direction...

All good thoughts, and I'm still "weighing" options. I'm ordering a spool of BoKu's stuff to try some sub-scale spar like test components to see what sort of challenge the bends might be, and how well, or poorly, the flat stock works with resin infusion.

I'll definately share the results.
 

proppastie

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Depends on what category you're designing to 4.4g limit is typical for a utility category aircraft.
Wiki - Load Factor
Some one told me the contest pilots will cross the finish at 180 and do a 5 g vertical pull up while voiding ballast "So they can get to pattern altitude " Which if you are not a designer is a good excuse.
 

proppastie

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My issue (currently today ) is 21" too much at 5g limit for 22ft. semi-span. For an aluminum structure fabric covered. Tomorrow the numbers probably will be different.
 

Victor Bravo

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Some one told me the contest pilots will cross the finish at 180 and do a 5 g vertical pull up while voiding ballast "So they can get to pattern altitude " Which if you are not a designer is a good excuse.
(Sorry, OT)
We crossed the finish line at the redline speed of the glider or less. Going faster than that and having a flutter incident in ground effect would be a very big mess on the runway with a pilot-colored streak in the asphalt. We all wore parachutes, so if you did an overspeed and fluttered your airplane apart at altitude you would more or less easily be able to get out of it.

BUT... the faster you crossed the finish line, the more altitude you had to gain somewhere that you really didn't need. So the (really fun, show-off) high speed low finish was actually an admission that you had spent too much time climbing in the last thermal.

(Matter of fact, the only time I ever got my license taken by the feds was because of one of these low-altitude ego-trips. It was admittedly dangerously low and completely un-necessary, just practicing for a contest at what I thought was a mostly abandoned desert airport. One of the glider instructors, a nice guy named Tom Dickenson, was walking with his wife, and I didn't see them. Never did see them. But apparently I went by them at or slightly below eye level, and Tom's wife soiled herself and fell down, getting mud and dirt on her clothes, and pissed of Tom pretty bad. Nobody ever said anything, and I just went on with my life until the phone rang with the FSDO on the other end... :) )

It's been a long time, but If memory serves, I believe that a perfectly efficient contest finish would be that you crossed the finish line at the optimum inter-thermal "speed to fly" that was calculated (or provided by a whiz-bang device) for that day.

The late great Helmut Reichmann, in his seminal book "Cross Country Soaring", put it best: "After all, the altitude for this airshow has to be gained somewhere..."

Pulling 5G puts a huge amount of drag on the airplane, which means you'd get to a lower altitude than if you did a smooth low-G pull up. I never did anywhere near that. Maybe 2 or 2.5. For the 1980's era 15 meter gliders (assuming we kept all of the water ballast for the whole flight) coming across the finish line at just about 0 feet AGL and 140 MPH, doing a mild pull-up, we'd easily get back up to 1000-1200 feet AGL.

That wasn't just pattern altitude, that was almost high enough to start out on another cross-country :)
 
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Exian

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Jul 26, 2018
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BORDEAUX
I analyzed photos of various gliders thermalling at various bank angles and doing finish pullups and chose a deflection per g that put me in about the middle of the cloud.
I am finalizing the design of the spar of my 15m glider projet, and by taking into account only strenght and manufacturing limitations (double taper of spar caps), I get a wing tip deflection of around 250 mm per G. Is that about right? Should it be less?

On the topic of this thread, for the spar caps, I started manufacturing my own "pultrusion-like" material.
I get carbon UD strips of 38x1 mm of cross section, 7 meters long, 56 to 58 % of fiber content (I need 50 of these...)
These can be flexed and twisted easily to comply with the skin shape, and the bend at wing root for T+F connection.

I tested this material by making a small wing spar, giving also information about the shear web strenght.
Was not able to break it, reached the max of my measurment device...

Mores explanation and pictures if anyone is interested!
 

Lendo

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Feb 6, 2013
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Brisbane
Exian, generally about 300mm or 1 ft (overall) for a standard aircraft design - don't know about gliders, they have long very flexible wings.
Billski did his Carbon Caps with Strips however his meticulous method make Carbon content quite high and his individual strands (TOW) as straight as he could possibly get them for best strength.
George
 
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