"Huh, interesting. I'd love to know more about what exactly this means:
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Nathan Wong's Discussions
Do cowlings around props increase thrust?
Started this discussion. Last reply by R_Lefebvre Oct 3, 2012. 13 Replies 0 Likes
So I saw the episode of Mythbusters the other day where they built a jetpack/personal flying machine.1 comment that stuck with me was that cowlings (enclosure for the propellers) were supposed to…Continue
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John Githens replied to Nathan Wong's discussion Do cowlings around props increase thrust?"I read both, and thanks! Can't say I followed most of the math (been a few years...), but there were some quotable text chunks in both. For example, from the ...833.pdf: "Helicopters are intrinsically unstable. They exhibit oscillating…"
Brad Hughey replied to Nathan Wong's discussion Do cowlings around props increase thrust?"Thanks, John. Here's one white paper I've found that contains most of the essential elements."
John Githens replied to Nathan Wong's discussion Do cowlings around props increase thrust?"Thanks Brad. This thread (and others on which you have commented) have distilled out some key information. (I continue to comb the DIY Drones blog for distilled information about tradeoffs related to: physical component placement on a small…"
DeveloperR_Lefebvre replied to Nathan Wong's discussion Do cowlings around props increase thrust?
"Oh right, there's that too.
So one could make a case for using smaller, but shrouded propeller, with the idea of making it more responsive.
Though, I think we'd also have to consider in this case, no just the inertia of the propellers…"
Cliff Dearden replied to Nathan Wong's discussion Do cowlings around props increase thrust?"Thanks Brad, interesting and as usual very informative."
Brad Hughey replied to Nathan Wong's discussion Do cowlings around props increase thrust?"For an electric multicopter with fixed-pitch, control response time is proportional to the rotational inertia of the blades, which also (undesirably) increases with the square of the radius. There are always compromises when you're…"
DeveloperR_Lefebvre replied to Nathan Wong's discussion Do cowlings around props increase thrust?
"I think there is a direct correlation to aircraft wingspans. For all the same reasons, a longer wing is more efficient than a shorter wing. The problem is there are often other constraints which prevent increasing the wingspan to…"
Brad Hughey replied to Nathan Wong's discussion Do cowlings around props increase thrust?"@Cliff: Yeah, I tend to get rather verbose at times. Mea culpa. ;-)
@R_Lefebvre: Yes, you are correct. For efficiency sake, you should always make the propeller (rotor) blade longer unless you can't for some reason*. …"
Cliff Dearden replied to Nathan Wong's discussion Do cowlings around props increase thrust?"Nice summary, looking forward to Brads reply!"
DeveloperR_Lefebvre replied to Nathan Wong's discussion Do cowlings around props increase thrust?
"Brad, so just to summarize, and confirm my thoughts on this matter, is this statement correct?
If you want to increase the efficiency of a give propeller, you can do so by one of two ways. You can shroud it, which reduces tip vortices,…"
Brad Hughey replied to Nathan Wong's discussion Do cowlings around props increase thrust?"The primary efficiency-related purpose of a duct/shroud/ring around a propeller is to fix a problem created by abnormally high disk loading (trying to get too much thrust out of a prop that is too small).
All wings, whether fixed or rotary,…"
Francisc Bereczky replied to Nathan Wong's discussion Do cowlings around props increase thrust?"It is hard to answer to your question. There are advantages and disadvantages.
http://en.wikipedia.org/wiki/Ducted_fan"
Nathan Wong posted a discussionDo cowlings around props increase thrust?
So I saw the episode of Mythbusters the other day where they built a jetpack/personal flying machine.1 comment that stuck with me was that cowlings (enclosure for the propellers) were supposed to increase thrust through the propellers. Anybody have experience with this? Would it make sense to add cowlings around the propellers of my hex for increased thrust or would the additional weight offset the gains in the scales these multicopters are created at?Apparently it has to be quite a tight fit…See More
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