Source for Carbon Rods?

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patrickrio

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Thanks. Interesting things in pics: seems like the pic is of the non vacuum bagged spar and they decided that they needed to vacuum bag it to drop resin fraction. They used peel ply to make good attach points for the ribs. I think this doesn't work well if you vacuum bag? The metal inserted for attach points is surprisingly small. I assume that they surrounded it with extra layers of carbon in a pattern of some sort, but I can't see evidence of that in the pictures. EDIT: ah. wing is not cantilever... doesnt need as much strength at that attach point.....

It is not easy to see what pattern they laid the pultrusions in. (EDIT: some other pics shown after vacuum bag and curing make it look like he might stack them in the corner??? pics are kinda confusing for layout..) You can barely see them at the root end on one side in the pic. looks like the root end has 4 pultrusions on one side... so 8 total at root end? then other writing elsewhere on other builds say his method is to have even spacing between where he drops to 3-2-1 pultrusions. I assume that this means the longest pultrusion is the one closest to the web.....

Edit: it looks like in the hand layup pics they laid the pultrusions side by side so that they were spread flat on the spar cap. For the vacuum layup they stacked them in the web/cap corner into a compact square shape.

Another Edit: This is the best page I have found on the WayBack machine copies of Marske pages.......
https://web.archive.org/web/20070817053337/http://www.continuo.com/marske/ARTICLES/Carbon rods/carbon.htm
 
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patrickrio

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And Jim's old web site have a lot of gems:

View attachment 110579
Yeah. I thought that was so clever. With CNC molding tech it seems like you could create an assembly line system for making the full tapered wing rib set on a wing via injection molding.

EDIT: there are pictures in the blog of them doing some ribs on negative molds (vacuum bag on skin attach surfaces) and some on positive molds (mold on skin attach surfaces). There was not an explanation of why they did one or the other, I would like to know why... I THINK they were going to do CF skins and so slightly rough attach surfaces from negative molds wasn't an issue so they used the advantage of easier table bagging on negative molds. BUT THEN they decided they needed to do fabric skins to save weight and thus needed the better surfaces for positive molds???

I would like to see the difference in weight though between a comparable strength CNC cut foam rib set and higher amount of adhesive to accomplish the same task.... I am very sure that CNC foam ribs would be MUCH faster and easier to make.

And I read elsewhere that he did not like foam ribs for early builds, but did not find info on why.....
 
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patrickrio

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Another interesting thing here is that he originally thought that it would be better to do one layer glass and one layer CF for the d tube.... and then after testing came to the conclusion that 2 layers of CF were needed. EDIT: later in blog, they switched back to one layer glass, one layer CF....
 
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Hephaestus

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It's interesting on the carbon Monarch - their final weight was 156lbs (including a 24lb brs). Now I want more details...
 

patrickrio

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Interesting tidbit on different page... in 2005 they recommended putting turbulator strips on the leading edge for control reasons.... so much for the laminar flow......
 

stanislavz

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And I read elsewhere that he did not like foam ribs for early builds, but did not find info on why.....
I did some personal conversation with Jim - corrugated rib is one step if done in mold, half step if cutted from sheet of corrugated sheet. Same for D tube - one single step, done by amateur. Plus lighter - too small load on skin to allow extra glue for foam void fills.
 

stanislavz

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Another interesting thing here is that he originally thought that it would be better to do one layer glass and one layer CF for the d tube.... and then after testing came to the conclusion that 2 layers of CF were needed. EDIT: later in blog, they switched back to one layer glass, one layer CF....
Exterior glass was added for sanding. He was using foil on foam molds, so it was not the best surface finish. But good.
 

Lendo

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TLAR anything I've learned, I've learned from others. No names mentioned to protect the innocent.
George
 

Lendo

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Interesting thing about Flat Rods (again From Steve Rahm the Vision Designer) he and his partner Scott found that very smooth and flat sided rods failed sooner than the Round Rods because, in his opinion, under vacuum the resin between Rods was squeezed-out and didn't maintain sufficient adhesion, whereas the resin between the Round Rods remained sufficient for bonding. Jim Marske suggested a layer fine cloth between square or Flat Rods to allow for sufficient resin retention. I suggested to Steve a little Flock in the Resin would help transfer loads between the Round Rods and Steve agreed.
Just some things to consider with Pultruded Rods.
Don't get me wrong the Quality Pultruded Rods are in themselves great, however with all considerations and costs, my 'roll-your-own' approach seems more, and more attractive. Each to their own, just be aware of some/all of the issues. If they were cheap and easy to get, I wouldn't bother messing about.
George
 

BoKu

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Quick update: I got compression test numbers back last night for the pultrusions from my supplier in China. Compression testing small composite columns is tricky, so there's a bit of data scatter and I'm not going to post raw numbers here. But we tested both our China-sourced and Graphlite pultrusions, and the numbers are comparable. It's clear that the product from China isn't the trash some might have feared.

So I'm moving towards the next round of tests, which probably involve tensile testing and also a reference spar for three-point bending tests. I might just go ahead and tool up for the CarbonMax spars; that seems as good a real-world test as any.
 

Lendo

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BoKo, be warned, High Modulus Carbon Tow Specs of a lesser quality Carbon Tow can look similar to a Low modulus high quality Carbon Tow. I would always go low Modulus as it's much less brittle. Would it matter for your application? I guess it would be in the testing.
George
 

davidjgall

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BoKo, be warned, High Modulus Carbon Tow Specs of a lesser quality Carbon Tow can look similar to a Low modulus high quality Carbon Tow. I would always go low Modulus as it's much less brittle. Would it matter for your application? I guess it would be in the testing.
George
I would think that would depend on the application. Low modulus translates to large deflections for long wings, requiring more material used further below its strength capability to provide the needed stiffness; the high modulus materials like Graphlite are already being used well below strength capability in order to provide adequate stiffness so, for wings, the low modulus material only adds weight. For short, stubby wings the calculus might be different but for high aspect ratio (sailplane) wings the low modulus is not a benefit.

Also, I've heard the declaration of brittleness before but I don't believe it. I think it is a failure to realize just how stiff low aspect ratio parts are when made of high modulus carbon, and a failure to realize the stress concentrations that occur when a thick (aluminum) part is replaced by a thin carbon part, e.g., an angle of equivalent strength that may also be subject to some bending load. The bending load may be insignificant for the thick angle being replaced but equates to a large fraction of the available material strength being used up in a thinner carbon part, leaving less available strength for the design loads. I'm not explaining myself well and don't wish to take the time to explain just now, but I dispute that high modulus carbon is necessarily more brittle than low modulus carbon, just less forgiving of misalignments and non-primary loads that maybe didn't need to be accounted for when built of other materials.
 

stanislavz

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might just go ahead and tool up for the CarbonMax spars; that seems as good a real-world test as any
My vote for this.

And from my point of view - your number 1 problem is deflection, not failure criteria for non-strutted wings. Especially thin one, in gliders
 
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BoKu

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Our first round of tests looked good enough that I just ordered another 3300 feet of the material. We'll be offering it under the trademark SparLite; this particular size is called SparLite 5x2 (five mm by 2 mm, get it?). It comes in 410-foot spools, and initial pricing will be $350 each for 1-4 spools, and $310 each for 5 or more spools. Cut lengths will be $1.25/foot.

My next order of business is to make a three-point-bending fixture that we can use to quickly sample coupons from each end of every spool. That's not a great way of getting absolute strength and stiffness values, but it is a reasonable way of comparing new batches with known good samples.
 
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