[101955] in tlhIngan-Hol
Re: [Tlhingan-hol] Propellers and rotors
daemon@ATHENA.MIT.EDU (Will Martin)
Thu Nov 5 14:16:50 2015
From: Will Martin <lojmitti7wi7nuv@gmail.com>
Date: Thu, 5 Nov 2015 14:16:35 -0500
To: "tlhingan-hol@kli.org" <tlhingan-hol@kli.org>
In-Reply-To: <CABSTb1fTS1_H0PfsPFHzU4yBwupvuXgRT9u0Dh8M3YPQQEnj2w@mail.gmail.com>
Errors-To: tlhingan-hol-bounces@kli.org
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The blade of an airplane propeller generates lift, like a wing, by =
creating pressure differences between the two major surfaces of the =
blade. Water is not compressible, so a water propeller works more =
through the redirection of momentum of mass. This is why water =
propellers use such remarkably steep angle of attack (typically around =
45 degrees), which would stall the blade of an airplane propeller, =
making it ineffectual for taxi or takeoff.=20
This is also why adjustable pitch propellers exist for aircraft =E2=80=94 =
because the angle of attack changes as the airspeed of the aircraft =
changes, and it=E2=80=99s better to pitch more shallow to get the =
airplane started on the ground and to climb, then pitch deeper to cruise =
efficiently without over-revving the engine. Less expensive aircraft are =
limited by fixed pitch propellers that have a single pitch, compromised =
between these two angles, less effective at either.
Nobody changes the pitch of a water propeller. There=E2=80=99s no real =
advantage to doing so, since water propeller blades can=E2=80=99t stall.
But hey, they both spin and they both push. I get it.
pItlh
lojmIt tI'wI'nuv
> On Nov 4, 2015, at 1:35 AM, Bellerophon, modeler =
<bellerophon.modeler@gmail.com> wrote:
>=20
> ghunchu'wI', jIQochlaw'. muDDujDaq, bIQDujDaq je nIbbe' bIngtaHbogh =
vo'wI', 'a rurbej.
> cha' tel rav ghaj ngIq vo'wI'. telvamvaD 'etlh ponglu' je.
> jaS 'etlhmeychaj chenmoHlu', jaS jeDmo' ngIq SubHa'wI' 'ej jaS =
'ughmo'. SubHa' bIQ muD je. (vIHtaHvIS neH SubHa'wI', luSIjlu' 'e' qaD. =
SubwI' rurbe'. SubwI' luSIjlu' reH 'e' qaD.)
> tlhe'taHvIS vo'wI', SubHa'wI' vIHtaHghachHey lurghDaq taHHa'mo' 'etlh, =
'etlh 'emDaq SubHa' yuvtaHghach HoS law' tlhopDaq 'oH HoS puS. pImmo' =
yuvtaHghach Duj vo'lu'. beQHa'chugh 'etlh, HoS rap natlhtaHvIS, yuv =
vo'wI' 'e' ghurlaH vay'. (Soy'law' mu'tlheghvam, chaq DIvI' Hol rur 'e' =
vIpIHchugh.)
> ~'eD
> --=20
> My modeling blog: http://bellerophon-modeler.blogspot.com/ =
<http://bellerophon-modeler.blogspot.com/>
> My other modeling blog: http://bellerophon.blog.com/ =
<http://bellerophon.blog.com/>
> _______________________________________________
> Tlhingan-hol mailing list
> Tlhingan-hol@kli.org
> http://mail.kli.org/mailman/listinfo/tlhingan-hol
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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dutf-8"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" =
class=3D""><div class=3D"">The blade of an airplane propeller generates =
lift, like a wing, by creating pressure differences between the two =
major surfaces of the blade. Water is not compressible, so a water =
propeller works more through the redirection of momentum of mass. This =
is why water propellers use such remarkably steep angle of attack =
(typically around 45 degrees), which would stall the blade of an =
airplane propeller, making it ineffectual for taxi or =
takeoff. </div><div class=3D""><br class=3D""></div><div =
class=3D"">This is also why adjustable pitch propellers exist for =
aircraft =E2=80=94 because the angle of attack changes as the airspeed =
of the aircraft changes, and it=E2=80=99s better to pitch more shallow =
to get the airplane started on the ground and to climb, then pitch =
deeper to cruise efficiently without over-revving the engine. Less =
expensive aircraft are limited by fixed pitch propellers that have a =
single pitch, compromised between these two angles, less effective at =
either.</div><div class=3D""><br class=3D""></div><div class=3D"">Nobody =
changes the pitch of a water propeller. There=E2=80=99s no real =
advantage to doing so, since water propeller blades can=E2=80=99t =
stall.</div><div class=3D""><br class=3D""></div><div class=3D"">But =
hey, they both spin and they both push. I get it.</div><br class=3D""><div=
class=3D"">
<span class=3D"Apple-style-span" style=3D"border-collapse: separate; =
color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; =
font-variant: normal; font-weight: normal; letter-spacing: normal; =
line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: =
0px; text-transform: none; white-space: normal; widows: 2; word-spacing: =
0px; -webkit-border-horizontal-spacing: 0px; =
-webkit-border-vertical-spacing: 0px; =
-webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
auto; -webkit-text-stroke-width: 0px; "><div class=3D"">pItlh</div><div =
class=3D"">lojmIt tI'wI'nuv</div><div class=3D""><br =
class=3D""></div></span><br class=3D"Apple-interchange-newline">
</div>
<br class=3D""><div><blockquote type=3D"cite" class=3D""><div =
class=3D"">On Nov 4, 2015, at 1:35 AM, Bellerophon, modeler <<a =
href=3D"mailto:bellerophon.modeler@gmail.com" =
class=3D"">bellerophon.modeler@gmail.com</a>> wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><div dir=3D"ltr" =
class=3D""><div class=3D"">ghunchu'wI', jIQochlaw'. muDDujDaq, bIQDujDaq =
je nIbbe' bIngtaHbogh vo'wI', 'a rurbej.<br class=3D"">cha' tel rav ghaj =
ngIq vo'wI'. telvamvaD 'etlh ponglu' je.<br class=3D""> jaS 'etlhmeychaj =
chenmoHlu', jaS jeDmo' ngIq SubHa'wI' 'ej jaS 'ughmo'. SubHa' bIQ muD =
je. (vIHtaHvIS neH SubHa'wI', luSIjlu' 'e' qaD. SubwI' rurbe'. SubwI' =
luSIjlu' reH 'e' qaD.)<br class=3D"">tlhe'taHvIS vo'wI', SubHa'wI' =
vIHtaHghachHey lurghDaq taHHa'mo' 'etlh, 'etlh 'emDaq SubHa' yuvtaHghach =
HoS law' tlhopDaq 'oH HoS puS. pImmo' yuvtaHghach Duj vo'lu'. =
beQHa'chugh 'etlh, HoS rap natlhtaHvIS, yuv vo'wI' 'e' ghurlaH vay'. =
(Soy'law' mu'tlheghvam, chaq DIvI' Hol rur 'e' vIpIHchugh.)<br =
class=3D""></div>~'eD<br class=3D""><div class=3D""><div class=3D""><div =
class=3D"gmail_extra">-- <br class=3D""><div class=3D"">My modeling =
blog: <a =
href=3D"http://bellerophon-modeler.blogspot.com/" target=3D"_blank" =
class=3D"">http://bellerophon-modeler.blogspot.com/</a><br class=3D"">My =
other modeling blog: <a href=3D"http://bellerophon.blog.com/" =
target=3D"_blank" class=3D"">http://bellerophon.blog.com/</a><br =
class=3D""></div>
</div></div></div></div>
_______________________________________________<br class=3D"">Tlhingan-hol=
mailing list<br class=3D""><a href=3D"mailto:Tlhingan-hol@kli.org" =
class=3D"">Tlhingan-hol@kli.org</a><br =
class=3D"">http://mail.kli.org/mailman/listinfo/tlhingan-hol<br =
class=3D""></div></blockquote></div><br class=3D""></body></html>=
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