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Old Mar 12, 2013, 09:04 PM
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edf fan/cylinder to outlet diameter ratios

Not sure if I'm asking this question correctly, but I'm beginning to indulge in EDF foamies, and want to know how the diameter of the outlet (actual tube in rear of the fuse) compared to the fan or the edf unit diameter is designed. I've done a rudimentary search on this forum, but haven't found anything I can use, yet. A tutorial on the EDF setup would be great!
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Old Mar 13, 2013, 12:02 AM
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im sure there is something here on it ...just may not have the right words for the search. try exhust fsa or tail pipe fsa . normally we run 90% to 80% exhust outlet size to the fan size. so it should be smaller than the fan shroud.
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Old Mar 13, 2013, 12:14 AM
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Here's a thread about FSA, Fan Swept Area, I asked about a while back. The wiser folks kindly educated me!

Fan Swept Area

(Love your Avatar animation, btw!)
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Old Mar 13, 2013, 12:19 AM
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Springer,

Search on Clausxpf (inlet/exhaust duct basics) for all the info you can handle. Also check out the builds in the Scratch Built and Micro EDF Forums. Also, look for Air Sally for how to make ducts. lmao!!!
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Old Mar 14, 2013, 07:58 AM
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Great! Thanks for the tips & leads! I got some reading to do.
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Old Mar 14, 2013, 08:46 AM
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Xmech: I went to your thread, and found a wealth of info, thanks! But as usual, it generated more questions. My first intro to EDF is gonna be a DH Venom.(well maybe, if I can figure the propulsion out. The goal is to size it to a single sheet of MPF - onesheeter #13 or #14 (it will make sense if you check my blog)

Anyway, from the other thread, why use fan shroud I.d. instead of actual fan dia. in the FSA calculation? Also, is something like 90% FSA inlet (including half lip radius) to 80% outlet a good general proportion? What happens if the inlet approached or exceeds 100% FSA? Finally, do all these proportions still hold with a split inlet, or are other "accommodations required? (maybe I should do the F86 I was originally considering.......)
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Old Mar 14, 2013, 10:18 AM
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Aaaahhhhhh! Feel the Force Springer. Come to the Dark Side. Check out this thread. It has a lot of reference links and awesome cad work.

Ksqm
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Old Mar 14, 2013, 12:13 PM
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Springer, your questions are already way over my head! Someone in that thread I started said a good intake size varies with the complexity of the ducting. He mentioned someones F-86 that had an 80% intake size and was great, but that's a pretty much straight through duct. haven't designed or even built my own edf's yet, I'm still on ARF's, so I just wanted to learn about the whole FSA intake/exhaust ratio thing to see if an exhaust tube could help any of my models or not. Turns out only my Dynam Turbojet (Cessna Citation) is the only one with an oversized exhaust, and might pick up some speed with exhaust tubes. But it's still on my to-do list.
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Old Mar 14, 2013, 12:33 PM
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Kq thanks for the tip!

xm: they are over my head as well, but I figure there are no dumb questions and the guys on this forum are as cool as those on the scratchbuilt foamies one, so I'll get great answers! I haven't done any ARF's, built a Gentle Lady balsa and monokote when I got back into the hobby in 04, but found the scratch built forum and foam, and haven't done anything else since. now past 70 planes and the addiction is only getting stronger!
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Old Mar 14, 2013, 01:23 PM
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70 planes!! And my wife thought I was bad with about a dozen! (That she knows of...)
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Old Mar 15, 2013, 09:23 AM
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It's just a matter of time.....Foam is just too easy to work with!

I downloaded the two spreadsheets and played with them, got the specs of my fan (a hobby king 55mm Aeorc, so not such great shakes, but it pulled out of my hand nicely at 25amps with 3s pack) and started the FSA and inlet/out let tinkering in Sketchup. Looks if I size the plane to the outlet dia, it'll come in at 50" span, which is a bit more than I'd like, so I may have to go non scale on the outlet (). It's gonna be stand way off scale anyway. Just another fun flyer, and have to fit it onto a single sheet of MPF. A nice challenge for packaging and propulsion - gotta keep the old dog learning new tricks!
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Last edited by springer; Mar 15, 2013 at 09:29 AM.
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