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Date: Mon, 1 Nov 2010 23:41:37 +0000 (UTC)
From: hoursaway1@comcast.net
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] How fast is it safe to turn a Prop. Opinion Poll
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Airframe control flutter, carefull Dave,=C2=A0we other "Rotary folks" love =
ya.=C2=A0=C2=A0 David R. Cook RV6A Rotary=C2=A0 (45 on ASI down the runway,=
 feeling good. Temps good, tied to truck full cowl, full throttle, 5975=C2=
=A0 29.5 MAP 10 min. ).=C2=A0=20
----- Original Message -----=20
From: "David Leonard" <wdleonard@gmail.com>=20
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>=20
Sent: Monday, November 1, 2010 2:49:04 PM=20
Subject: [FlyRotary] How fast is it safe to turn a Prop. Opinion Poll=20


So I am getting a little more bold with my new=C2=A0turbo.=C2=A0 On the way=
 home today I decided to open it up a little bit.=C2=A0 At 8500' and MAP ar=
ound 34", I was at 6700 RPM and 201 KTAS (about 3060 RPM at the prop with t=
he tips doing 860fps).=C2=A0 Temps still less than 160, plenty of throttle =
left.=C2=A0 I just couldn't accept turning the prop any faster, not knowing=
 what the limit really is.=20

My prop is a 64" diameter (pretty short) Catto (wood/composite) with a numb=
er of nicks in the leading edge and has not been dynamical balanced to date=
.=20

I talked to Craig Catto about the issue and=C2=A0what he told me completely=
 makes sense, but is utterly unhelpful in setting my racing redline.=C2=A0 =
He said that I could turn it as fast as I want, but the risk of separating =
the prop. increases as I go faster.=C2=A0 I just depends on too many factor=
s.=20

I realize the the final number is going to depend on my risk tolerance and =
how much I really want to post some big numbers in a race.=C2=A0 But it is =
hard for me to balance that without better understand or the factors on the=
 prop, hence, the opinion poll, on various factors..=20

I have heard that it is important to keep the prop tips under 900 fps, whil=
e others say it is not a factor.=C2=A0 Is there some important number for t=
he max tip speed?=C2=A0 Is it a safety issue or an efficiency issue?=20

Most of my nicks in the paint and composite layer are in the outer 1/3 of t=
he prop.=C2=A0 Are these a big deal for safety?=C2=A0 Efficiency?=20

If I were to run the engine at 7000 RPM that would give me 3225 at the prop=
, tips doing 900 FPS an an aircraft speed of around 209 kts (240mph).=C2=A0=
 This seems pretty reasonable to me as an upper limit, but it is scary a li=
ttle.=20

But what about 8000RPM at the engine (if I have the power to get there)?=C2=
=A0 With a cleaned up and balanced prop, that would be almost 3700 RPM at t=
he prop, tips doing 1020fps, aircraft going=C2=A0something less than 240kts=
=C2=A0(275 mph).=C2=A0 Stupid though? Or give it a try and see how close to=
 those numbers I can get?=20

Any issues with the gear-box going that fast, other factors I am not consid=
ering?=20

Anyway, it feels really cool to have broken 200kts in level flight.=20

--=20
David Leonard=20

Turbo Rotary RV-6 N4VY=20
http://N4VY.RotaryRoster.net=20
http://RotaryRoster.net=20

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<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Arial; font-size: 12pt; color: #000000'>Airframe control flutter, carefull Dave,&nbsp;we other "Rotary folks" love ya.&nbsp;&nbsp; David R. Cook RV6A Rotary&nbsp; (45 on ASI down the runway, feeling good. Temps good, tied to truck full cowl, full throttle, 5975&nbsp; 29.5 MAP 10 min. ).&nbsp;<BR>----- Original Message -----<BR>From: "David Leonard" &lt;wdleonard@gmail.com&gt;<BR>To: "Rotary motors in aircraft" &lt;flyrotary@lancaironline.net&gt;<BR>Sent: Monday, November 1, 2010 2:49:04 PM<BR>Subject: [FlyRotary] How fast is it safe to turn a Prop. Opinion Poll<BR><BR>
<DIV>So I am getting a little more bold with my new&nbsp;turbo.&nbsp; On the way home today I decided to open it up a little bit.&nbsp; At 8500' and MAP around 34", I was at 6700 RPM and 201 KTAS (about 3060 RPM at the prop with the tips doing 860fps).&nbsp; Temps still less than 160, plenty of throttle left.&nbsp; I just couldn't accept turning the prop any faster, not knowing what the limit really is.<BR><BR>My prop is a 64" diameter (pretty short) Catto (wood/composite) with a number of nicks in the leading edge and has not been dynamical balanced to date.</DIV>
<DIV>&nbsp;</DIV>
<DIV>I talked to Craig Catto about the issue and&nbsp;what he told me completely makes sense, but is utterly unhelpful in setting my racing redline.&nbsp; He said that I could turn it as fast as I want, but the risk of separating the prop. increases as I go faster.&nbsp; I just depends on too many factors.</DIV>
<DIV>&nbsp;</DIV>
<DIV>I realize the the final number is going to depend on my risk tolerance and how much I really want to post some big numbers in a race.&nbsp; But it is hard for me to balance that without better understand or the factors on the prop, hence, the opinion poll, on various factors..</DIV>
<DIV>&nbsp;</DIV>
<DIV>I have heard that it is important to keep the prop tips under 900 fps, while others say it is not a factor.&nbsp; Is there some important number for the max tip speed?&nbsp; Is it a safety issue or an efficiency issue?</DIV>
<DIV>&nbsp;</DIV>
<DIV>Most of my nicks in the paint and composite layer are in the outer 1/3 of the prop.&nbsp; Are these a big deal for safety?&nbsp; Efficiency?</DIV>
<DIV>&nbsp;</DIV>
<DIV>If I were to run the engine at 7000 RPM that would give me 3225 at the prop, tips doing 900 FPS an an aircraft speed of around 209 kts (240mph).&nbsp; This seems pretty reasonable to me as an upper limit, but it is scary a little.</DIV>
<DIV>&nbsp;</DIV>
<DIV>But what about 8000RPM at the engine (if I have the power to get there)?&nbsp; With a cleaned up and balanced prop, that would be almost 3700 RPM at the prop, tips doing 1020fps, aircraft going&nbsp;something less than 240kts&nbsp;(275 mph).&nbsp; Stupid though? Or give it a try and see how close to those numbers I can get?</DIV>
<DIV>&nbsp;</DIV>
<DIV>Any issues with the gear-box going that fast, other factors I am not considering?</DIV>
<DIV>&nbsp;</DIV>
<DIV>Anyway, it feels really cool to have broken 200kts in level flight.<BR clear=all><BR>-- <BR>David Leonard<BR><BR>Turbo Rotary RV-6 N4VY<BR><A href="http://n4vy.rotaryroster.net/" target=_blank>http://N4VY.RotaryRoster.net</A><BR><A href="http://rotaryroster.net/" target=_blank>http://RotaryRoster.net</A><BR></DIV></div></body></html>
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