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-   -   a couple printed ideas (https://vansairforce.net/community/showthread.php?t=147771)

Steve Melton 11-18-2017 07:21 AM

drag coefficient comparison. if I remember my calculation correctly, the Reynolds number for a 0.2 inch diameter cylinder at RV speeds at 10K ft altitude = 30000. an airfoil profile shape has much lower drag than a cylinder shape for an equivalent d dimension. what's amazing to me is the drag of a small cylinder shape such as a wing bracing cable.


sblack 11-18-2017 12:21 PM

What is clear from those sketches is that anything with a wake behind it generates a lot of drag. The forward shape is not really that important within reason. If you want to go faster, fix anything that generates a wake downstream.

Steve Melton 11-18-2017 04:22 PM

cool Airbus, or rather Boeing! style pics








BHunt 11-19-2017 11:03 AM

Quote:

Originally Posted by Steve Melton (Post 1219756)
cool Airbus, or rather Boeing! style pics








Any speed improvements through test flights?

Steve Melton 11-20-2017 10:32 AM

planning to test this week. it's taking some extra time to fit the remaining. tweaks to the anti-rotation stop for wing structure and mod for standard cotter pin fitment. fairing position 1&6 are same but will be mirrored. bolt head to always face outboard. fairing position 2&5 are same but will be mirrored. fairing position 3&4 are same but will be mirrored. for flight testing the fairings will not be mirrored. I'm looking forward to the testing and hoping for 3 kts gain.

WingsOnWheels 11-21-2017 01:27 PM

This may have already been mentioned, but for the type of parts I see here, PETG is probably a good material option for most home printers. PLA is easy to work with, but not really suitable for aircraft parts. ABS is good as well, but very prone to warp, and brittle. Nylon is awesome, but also prone to warp and many home printers don't really run hot enough.

After playing with PETG quite a bit, I like it. PETG is the same stuff water bottles are many of. It is more pliable than PLA or ABS, so maybe not the best for small stiff parts. However, it has great inter-layer bond and very little warp. The surface finish is not as nice as some of the others since it tends to be a bit "stringy". However, a fast pass with a torch or heat gun cleans that up. It does well in hot environments like ABS. It reminds me of a slightly softer version of polycarbonate. Extrusion temp is 235-255c, My printer tops out at around 240c and it works well.

Steve Melton 11-22-2017 06:16 AM

ABS has good strength and creep resistance. ABS is used for Lego parts. I have 40 year old Lego's that look and work like new. ABS max operating temp = 80C (176F). ABS can be more difficult to print. Once you get the print temperatures dialed in you can make some really good parts.

Position #4 fairing


First print with cotter pin access mod. Standard cotter pin fitment.

Vlad 11-22-2017 06:26 AM

Nice work Steve. Wondering if you can play with a headlight mold. I was trying to fit the RV10 light Zac sells into my cowling. The shape of the base was different and I couldn't integrate it without major alteration. Give it a shot down the road :)

Steve Melton 11-22-2017 06:34 AM

will do. I need to fit you with some of these fairings if I find 3 kts. they will not affect your paint scheme. time to install a set = 1 hr.

Vlad 11-22-2017 06:49 AM

Quote:

Originally Posted by Steve Melton (Post 1220519)
will do. I need to fit you with some of these fairings if I find 3 kts. they will not affect your paint scheme. time to install a set = 1 hr.

That would be awesome. They will hide the rust as well :)


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