Full disclosure I'M NEW at all this, have some background in building vehicles and such and hold my PPL. Fell in love with the BearHawk and am currently in the learning and research phase of all this. No I'm not made of money but came across this while looking into stuff for my other non pilot life. feel free to scold me anytime I spout nonsense! I went down this rabbit hole purely out of curiosity (seen a squirrel and chased it).
I was curious (minus cost prohibition) if anyone has tried to replace a traditional fabric (like polly fiber fabric) with a carbon fiber composite? I did some comparisons of very thin 1mm Carbon Fiber (CF) sheeting to fabric in the area of durability, toughness, pressures and so on. I am NOT suggesting the use of CF for anything structural, just skins. I know there has been some concerns out there on blogs and such about when CF fails its catastrophic. I talked with my aunt who is a composites engineer (not in aviation) about some of those concerns. Her thought was the CF sheeting could be (in theory) safely used as skins, even on control surfaces because the loads are so low. as for concern about failures, anything could happen but the typical rock pelting from prop-wash on the horizontal stabilizer shouldn't cause catastrophic failure and would likely be highly resistant to that kind of use in a backcountry setting. I found some sheets pretty close to 4'x8'x1mm for pretty reasonable (as far as CF prices go) for about $380 a sheet. I have no idea how much would be needed to skin the Bearhawk as a direct replacement for fabric.
I called a local manufacture (in the USA) for some Q&A about CF sheets and found the following:
Q: What is the weight, strength of the 1mm CF sheeting?
A: 3.1 oz per square yard. 1mm" thickness, Strength 33,000 psi
Q: What is the cost of a "sheet"
A: Sheet price $795 (4’ x 8’ sheet Gloss finish) $755 (4'x8" sheet Matt finish) (prices as of 12/2020) for the USA Manufacture found an overseas for $380 a sheet same size.
Q: What type of CF are the sheets?
A: 0 / 90 degree Twill, two layers of CF with epoxy. Sheets are made via the pre-preg CF material and compressed and heated to prescribed temperatures for curing (for good quality control and strength)
Q: What would a sheet failure look like for the material? (I explained the sheets would be used in theory for skin of an aircraft, not required to be structural).
A: This was a bit of a longer conversation back and forth and of course they wouldn't commit to anything officially but they have been creating CF stuff for a long time. uses have been in motor sports and off-roading applications. It boils down to this. if the CF is being used as a skin (even control surfaces skins) and not relied upon for structural support. there's no reason the sheeting wouldn't be sufficient. Even if used on a bush plane where there would be potential for rock chips and debris from prop wash, pelting the CF; it wouldn't likely cause the catastrophic failures that scares everyone about CF, simply because there's not a significant enough "load" on the panels. so even the "mega rock chip" on say the bottom side of the horizontal stabilizer that is experiencing some "loads" associated with airflow, it wouldn't be enough to cause the explosive failures you see in structural CF testing. It would most likely cause a pitting or "tear" in the CF but not be catastrophic to the surrounding portions of the panel.
Q: How flexible are the sheets to work with?
A: as a sheet goes its pretty flexible and as thin as that sheet is would likely be shipped rolled up.
Q: How well do the panels hold up to UV light?
A: Very well, over time you may notice some yellowing of the epoxy resin on the surface but it can be cleaned away with denatured alcohol. they haven't noticed any other property changes. from UV exposure. Additionally you can spray clear coat UV protection over it if you are overly concerned. it can also be painted with auto/aviation paints as well.
So how does this compare to a heavy fabric on aircraft? To be clear its defiantly not cheaper. but from a physics perspective (my very limited understanding). Aircraft Spruce is listing the following specifications for Poly-Fiber heavy fabric.
I'm still interested in what gotcha's might be out there by folks with some experience (obviously cost is the biggest gotcha). Any thoughts?
Below are the links for reference.
Dragon Plate CF manufacture (USA) https://dragonplate.com
Aircraft Spruce's heavy fabric listing https://www.aircraftspruce.com/catal...fiberheavy.php
I was curious (minus cost prohibition) if anyone has tried to replace a traditional fabric (like polly fiber fabric) with a carbon fiber composite? I did some comparisons of very thin 1mm Carbon Fiber (CF) sheeting to fabric in the area of durability, toughness, pressures and so on. I am NOT suggesting the use of CF for anything structural, just skins. I know there has been some concerns out there on blogs and such about when CF fails its catastrophic. I talked with my aunt who is a composites engineer (not in aviation) about some of those concerns. Her thought was the CF sheeting could be (in theory) safely used as skins, even on control surfaces because the loads are so low. as for concern about failures, anything could happen but the typical rock pelting from prop-wash on the horizontal stabilizer shouldn't cause catastrophic failure and would likely be highly resistant to that kind of use in a backcountry setting. I found some sheets pretty close to 4'x8'x1mm for pretty reasonable (as far as CF prices go) for about $380 a sheet. I have no idea how much would be needed to skin the Bearhawk as a direct replacement for fabric.
I called a local manufacture (in the USA) for some Q&A about CF sheets and found the following:
Q: What is the weight, strength of the 1mm CF sheeting?
A: 3.1 oz per square yard. 1mm" thickness, Strength 33,000 psi
Q: What is the cost of a "sheet"
A: Sheet price $795 (4’ x 8’ sheet Gloss finish) $755 (4'x8" sheet Matt finish) (prices as of 12/2020) for the USA Manufacture found an overseas for $380 a sheet same size.
Q: What type of CF are the sheets?
A: 0 / 90 degree Twill, two layers of CF with epoxy. Sheets are made via the pre-preg CF material and compressed and heated to prescribed temperatures for curing (for good quality control and strength)
Q: What would a sheet failure look like for the material? (I explained the sheets would be used in theory for skin of an aircraft, not required to be structural).
A: This was a bit of a longer conversation back and forth and of course they wouldn't commit to anything officially but they have been creating CF stuff for a long time. uses have been in motor sports and off-roading applications. It boils down to this. if the CF is being used as a skin (even control surfaces skins) and not relied upon for structural support. there's no reason the sheeting wouldn't be sufficient. Even if used on a bush plane where there would be potential for rock chips and debris from prop wash, pelting the CF; it wouldn't likely cause the catastrophic failures that scares everyone about CF, simply because there's not a significant enough "load" on the panels. so even the "mega rock chip" on say the bottom side of the horizontal stabilizer that is experiencing some "loads" associated with airflow, it wouldn't be enough to cause the explosive failures you see in structural CF testing. It would most likely cause a pitting or "tear" in the CF but not be catastrophic to the surrounding portions of the panel.
Q: How flexible are the sheets to work with?
A: as a sheet goes its pretty flexible and as thin as that sheet is would likely be shipped rolled up.
Q: How well do the panels hold up to UV light?
A: Very well, over time you may notice some yellowing of the epoxy resin on the surface but it can be cleaned away with denatured alcohol. they haven't noticed any other property changes. from UV exposure. Additionally you can spray clear coat UV protection over it if you are overly concerned. it can also be painted with auto/aviation paints as well.
So how does this compare to a heavy fabric on aircraft? To be clear its defiantly not cheaper. but from a physics perspective (my very limited understanding). Aircraft Spruce is listing the following specifications for Poly-Fiber heavy fabric.
- Weight – 3.4 oz/sq yd
- Breaking Strength – Avg 113.5 lbs/in
- Bursting Strength – 279 psi
- Tear Strength – Warp 108 lbs, Fill 119 lbs
I'm still interested in what gotcha's might be out there by folks with some experience (obviously cost is the biggest gotcha). Any thoughts?
Below are the links for reference.
Dragon Plate CF manufacture (USA) https://dragonplate.com
Aircraft Spruce's heavy fabric listing https://www.aircraftspruce.com/catal...fiberheavy.php
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