Source for Carbon Rods?

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Lendo

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I didn't get a response from Jim, but your response says it all. There is an European Company who sells quality Pultrusion, one of the European boys on here put me onto them. For me in Australia the costs were the same (expensive). Yes Diversifield were the manufacturers in the States, I have the name of the European Manufacturer in my notes somewhere.
Hs anyone tried Taiwan, their doing a lot of quality production of Carbon and not as expensive as the Japanese products. Maybe Pultrusion may be an extensive of that manufacturing Base.
George
 

Lendo

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I can't understand a European Company buying out an American Company and not opening in another name within the US. The current Pandemic may have stalled the transfer process- who knows. The Company in the Netherlands is D.P.P., they do quality Epoxy pultrusions, perhaps they are the company. Hang-on found my notes, the US Company EXCEL took over Diversifield, perhaps they onsold it.
Sorry that's all I have at the moment..
George
 

patrickrio

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I can't understand a European Company buying out an American Company and not opening in another name within the US. The current Pandemic may have stalled the transfer process- who knows. The Company in the Netherlands is D.P.P., they do quality Epoxy pultrusions, perhaps they are the company. Hang-on found my notes, the US Company EXCEL took over Diversifield, perhaps they onsold it.
Sorry that's all I have at the moment..
George
Exel Composites Oyj is a Finnish company. Took over Diversified in 2018 US Location in Erlanger KY Headquarters Vantaa Finland
 
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TLAR

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Maybe a work around could be a way to pultrude your own rods in a shape and length that fits your needs.
No supply chain worries
 

patrickrio

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I thought about doing pultrusions also, so I started researching the process. To get consistent results you need constant mechanical pull on the finished end of the pultrusion which basically requires 2 precision computer controlled grippers at a minimum. The pultrusion must hard cure within the short compression zone of a die in order to get consistent results also which requires the use of fast setting high temp thermoplastics, in our case I think high temp epoxies are probably the best choice due to strength qualities. The cure temperature must be carefully controlled which requires computerized PID control. The epoxy must be continuously infused in exactly the right amount in a continuous process which requires computer control as well as a computer controlled feedback loop. I believe that a mold release agent must be continuously injected between the pultrusion and the die in perfect quantities and positioning.

This whole process cannot be done simply at home with any expectation of consistent high performing pultrusions. Here is a video of pultrusion machines in action....
 

Vigilant1

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It would definitely be hard to replicate the process for making pultrusions the way they are made at industrial scale.

Getting the fibers straight is the thing. I don't know that it is impractical to do that in a home shop with CF tow carefully bonded to a fixture at each end and put under tension inside a mold, then infused (or even just epoxy and vacuum bag). I doubt it would meet factory specifications (due to fiber alignment, resin fraction), esp for compressive strength. Some folks would be willing to do it if the cost was significantly lower or availability/hassle was less. Obviously, one essential characteristic is consistency of performance, and I suppose that will be a factor in favor of a factory-produced pultrusion.
I think we've all seen pictures of homemade spar caps fabricated from fiberglass rovings. I don't recall how they typically stacked up to FG uni tape or factory FG pultrusion rods (did they exist?)
 
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TLAR

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I have a plan worked out to replace the wood caps in the Sky Pup spar with carbon tow placed in a dovetailed slot routed into Dow billet foam which will increase its MTOW. Easy Peasy.
 

Lendo

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I have also researched making my own Spar Caps , using my own Pultrusion technique. It required a Die and a Resin Bath, the tension can be maintained with a fixture winding-in the Carbon onto the shape required fixture . The Die size controls resin content and the steps in the Caps can be made by doing the caps in pairs, for both top and bottom without disrupting the the winding process. Just a matter of cutting to separate the Caps and trimming the ends of each step and Cap ends. Naturally control over the wet-out Carbon Tow is needed, so that it's spread evenly i.e. doesn't bunch-up.
I don't know if that helps anyone, but that will be my approach.
George
 

stanislavz

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In cos and pros on diy carbon pultrusion - bigger winner is consistency of ready made ones..
It is still too much X in whole home-building, but making one more in crucial component is big no-no for me..
 

patrickrio

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In cos and pros on diy carbon pultrusion - bigger winner is consistency of ready made ones..
It is still too much X in whole home-building, but making one more in crucial component is big no-no for me..
This was pretty obvious from the data and other evidence. Even getting consistent results from pro machines requires some care. I also read a report on windmill blades where they found it was better to use a subcontractor with demonstrated consistency and then statistically test their pultrusions before use than to buy the pultrusion equipment themselves and operate it intermittently. Clearly this could vary with windmill blade manufacturer, but the fact that professionals in CFRP like those guys came to that conclusion gave me pause.

It is clearly hard to consistently get the high end of advantages that a pultrusion can provide.
 

stanislavz

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Clearly this could vary with manufacturer, but the fact that professionals in CFRP like those guys came to that conclusion gave me pause.
Not only this aspect.

Doing nice composite is possible for average Joe. Doing this consistent with high quality is problematic for some Pros. Just by using ready made pultrusion with are left only with connectors (which are well described in Jim book) - which are overbuild anyway due to spreading of concentrated load.

And that is left - are some skins, which are build in the 1 place to withstand moron pencil. Not air load. And here it is again easier to wet, over-epoxied layout in cf - it is thicker and more rigid.

Where this kind of mold if go-go for such a simple project : 1620824555516.png

 

patrickrio

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The airplane calculator spreadsheet on the homepage is fun to play with. That whole website is super interesting for carbon fiber construction. thanks.

I am very interested in seeing carbon fiber wing constructions for planes in that weight range built with rectangular CFRP pultruded strips in the spar caps.
 

Vigilant1

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I am very interested in seeing carbon fiber wing constructions for planes in that weight range built with rectangular CFRP pultruded strips in the spar caps.
Agreed, and the pultruded spar caps are being widely adopted by designers even for aircraft that are otherwise primarily wood (SD-1, Gazaile, Lucille, etc).
 

rv7charlie

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That site looks really interesting, but the 1st thing I noticed was using what appears to be a butane/propane bottle (compressed gas container) as a 'vacuum reservoir'. Smarter people than me say pulling a vacuum on a container meant only for compressed gasses can be really hazardous.
 

Lendo

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Patrickrio, I agree with you, but given the cost and access to quality product, the "Roll-Your-Own" is looking more and more attractive.

Stanislavz, As Billski always says 'it's in the testing' of your samples, to understand the results. I know Billski did his Caps with Uni Strips under stringent control over Resin content, even so keeping the Tow straight would be difficult.

Remember even the Quality Pultrusion should be devalued for real world application, as many builders do.
Remember also the Commercial Rods can be bent to allow for Dihedral are also pre-loaded. A winding of Carbon Tow and Resin is not so loaded.

Lots of things to consider.
George
 

patrickrio

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Does anyone have drawings/layup schedule lists for extremely lightweight wings using CF pultrusions and probably CF Dtube in the design? for wings in the 70-130 sq ft area range and design gross weights under 400lbs is what I am interested in seeing. Glider aspect ratios preferred.....

I have found some videos of wing layups for higher gross weights but haven't found lighter stuff.

I don't need exact, I just want to get a feel for what real engineers are doing at this weight with the material.
 

stanislavz

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Stanislavz, As Billski always says 'it's in the testing' of your samples, to understand the results. I know Billski did his Caps with Uni Strips under stringent control over Resin content, even so keeping the Tow straight would be difficult.
Not only. Stability of achieved parameters is in first place. And you have to do many samples and test them, and make run numbers from lowest one.
 

patrickrio

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Not only. Stability of achieved parameters is in first place. And you have to do many samples and test them, and make run numbers from lowest one.
Once tested and incorporated into wing load calculations, approximately how much more % weight did your self made uni caps need compared to calcs for similarly functioning pultrusion caps? Did you do any type of comparisons at the calc stage?

oops... misunderstood. It's Billski who did his own uni spars..
 
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