Hi all, I’m trying to make a composite UAV but have been advised against c/f and Kevlar because they block out and distort radio signals. Does anybody know if diolen or another composite will be fine to use or is it just fiberglass? Needs to be light as its for a plane lol. Thanks
CF blocks RF due to its conductive properties. Kevlar does not block RF. Diolen has the same properties as kevlar but looks like CF so you’ll be fine with that.
You’re not building an X8 are you?
I’m going to try :D. DIY drones member by any chance? Any tips? other than don’t bother haha
Haha we’ll have to stop meeting like this!
For the mould cover up the foam with brown packing tape. Resin will not stick to the tape and will release without waxing or PVA. You’ll need to refinish the mould due to the tape over lapping but at least you’ll still have an intacted X8. Watch out for the exotherm melting/burning the foam or tape. You’ll have to try this first on a sample
You’ll be good with diolen but its about the same price of CF. There’s also decent strength in woven glass and epoxy but dont use CSM and poly resin for the end product. Keep that for moulds
I’d have liked to give this a go myself but couldnt find a X8 in the UK
Haha i know. That’s some great advice mate il give it a go when I get my x8. The uk doesn’t say anything. I’m gonna bite the bullet and get one from bevrc and hope I don’t get nailed at customs. Because of the wing tips curving up it will have to be a 2 piece mould unless I moulded the bend seperatly. Hopefully it won’t be to heavy and actually flies haha. Thanks again for all your advice (on both forums) just thought I’d go on the composite forum to be sure on the materials.
Yeah the wings could be tricky! You’d need seperate upper and lower moulds and bond the parts together as it would be very tricky to get some sort of bladder in place to inflate and compress the composite against the mould to make a one piece wing.
Good luck with the project. I’m happy to help if you’ve got any more questions. And be sure to post some pics when you get going.
H-Glass is an interesting option. However I havent found it as unidirectional fabric.
Aramid does not block RF, at least not in the GHz range. I transmit data through that material with RF. I wish I could elaborate, but cannot give more details.
Any idea about the MHz range. I’m planing on using 433mhz for control and 2.4ghz for video/telemetry.
only conductors can act as a faraday’s cage an block signals. carbon is a semi conductor, and aluminium coated glass is a bit too, so with those you have to be carefull. I know in RC sailboats the carbon mast is sometimes used as an antenna. Radar domes and antennas are made of glassfibre. You could use glassfibre where the antenna is, and carbon elsewhere.
Just found some 36g m/2 Kevlar which will be nice and light and easier to shape. I think if I cut the 90 degree tip off the end o the wing and make a seperate mould for that then I can make a plug for the wing and it will be one solid peice which I can just pull off the plug to make spares.
For optimal radio transparency look into quartz glass fiber. Fothergill might have some. I am sure you will not like the price though…
Is there a list available of which products block which frequencies? Or which materials to use in which application?
Carbon for instance is great for X-ray tables
D-glass or any other quartz glass fiber good for radar transparency
I am sorry I missed this thread, i’ve been on vacation.
What freq do you want to deal with? Kevlar is fine at lowers, but not structural at all. S-2 glass is more or less transparent at most freqs. i fyou want to get crazy, quartz, and plastics, such as Dynemma ST17, is both structural, and RF transparent…but hard to work with. We dal with antenna composites quite a bit, PM me if needed.
*edit: saw your reply about the freqs…what structure do you need? Again, kevlar would be fine there, but is still in the “soft” range. Do S2 glass and you will be fine.
This is an informative thread, thanks guys.
My question is in a similar vein (and vaguely drone related): Sometimes the carbon’s ‘Faraday Cage’ effect is a good thing - but how do you handle things like:
a) shielding grounds. For instance a bonded, metal stud would just galvanize, right…?
b) and bulkhead passthroughs when wiring an antenna’s source (within a carbonfiber enclosure) to an antenna ouside the enclosure (in a Aramid/Kevlar/whatever ‘dome’)? I’d prefer to use Cannon or CPC style connectors…so maybe PTFE bushings?
I hope that makes sense.
Or link to any research (Arxiv.org) on the subject worth reading…
For constructive input, I’ve been shooting <100mW 2.4Ghz packets through Kevlar with no noticeable bit flips at a paltry 115,200bps at (80-100*F, ~90% humidity).
Il look into the quartz glass as I need it to be nice and rigid with minimal flex. I don’t fancy gettin to giddy with the sticks and it disintegrating mid air because of the forces. Thanks again for all your help guys.
This is the airframe im using but as I hate foam a composite one needs to be made. Wing span is just over 2.1 meters
http://www.google.co.uk/search?hl=en&safe=off&gl=uk&site=webhp&tbm=isch&source=hp&q=skywalker+x8&oq=skywalker+x8&gs_l=mobile-gws-hp.3..0j0i24l4.14628.20325.0.20752.12.9.0.3.3.0.311.1380.0j8j0j1.9.0.crnk_mobile_unfiltered..0.0...1ac.ZzAh3--LehA&biw=320&bih=416&sei=E5ZVUPStM8HJ0QWMiYHgAw#p=0
Yes, carbon will have issues with corrosion. You can use copper mesh as a main ground plane.
B: RF connectors can be anything. Simple bulkheads, or running a cable through the body, maybe having some silicone as the bushing. If you need more data, then anything you can use as a bulkhead is fine. It all is depending on your exact specs and project.
RF transparency is easily done with S2, or Quartz. Quartz is VERY expensive. If you can mold it, ST17 is a nice choice. Again, depends on your mechanical specs. If the antenna is on the outside (conformal), then your body should not matter, and if carbon, act as the ground plane. Use any bulkhead as needed, and have your equipment inside.
PM me if you need to know details and don’t want your project specifics known.