Today's Message Index:
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1. 04:29 AM - Re: Re: What ultralight? (John Bolding)
2. 04:52 AM - Re: Re: What ultralight? (Wayne Bressler)
3. 08:13 AM - Re: What ultralight? (davecove)
Message 1
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| Subject: | Re: What ultralight? |
Why would you want to do that? if you have more hp get more pitch or a
longer prop.
JB
----- Original Message -----
From: "davecove" <dave@gmail.com>
Sent: Monday, May 02, 2011 1:08 AM
Subject: Ultralight-List: Re: What ultralight?
>
> So, could you realistically swing a 54x20 prop at around 4100 if you had
> enough hp? (Do I calc correctly that a 54" prop at 4060rpm is 85% mach
> and is thus OK?)
>
> Dave
>
> --------
> Dave
> 701-wannabe-soon
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=338616#338616
>
>
>
Message 2
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| Subject: | Re: What ultralight? |
The longer the prop, the better. Slower RPM's are more desirable for prop performance,
yes?
Wayne Bressler
Taildraggers, Inc.
www.taildraggersinc.com
On May 2, 2011, at 7:24 AM, "John Bolding" <jnbolding1@teleshare.net> wrote:
>
> Why would you want to do that? if you have more hp get more pitch or a longer
prop.
>
> JB
>
> ----- Original Message ----- From: "davecove" <dave@gmail.com>
> To: <ultralight-list@matronics.com>
> Sent: Monday, May 02, 2011 1:08 AM
> Subject: Ultralight-List: Re: What ultralight?
>
>
>>
>> So, could you realistically swing a 54x20 prop at around 4100 if you had enough
hp? (Do I calc correctly that a 54" prop at 4060rpm is 85% mach and is thus
OK?)
>>
>> Dave
>>
>> --------
>> Dave
>> 701-wannabe-soon
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=338616#338616
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>
>
>
Message 3
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| Subject: | Re: What ultralight? |
Why? Only because a certain engine (not the vw) develops its best hp at that rpm.
So what I seem to be learning is this... if the ground clearance only allows for
a 54" prop, you could use 4100rpm (best hp for a certain engine) because the
tips don't go over .85 mach, but it isn't very efficient prop-wise. So while
you get more hp out of the engine, less of it makes it to the air. It might be
better to turn the engine and prop at 3500 and while you get lower hp, more
makes it into the air.
Better might be to let the engine run 4100 and use a PSRU to get the prop down
to 2500... unless the weight of the PSRU eats all the gains made by moving the
prop from 4100 down to 2500.
I think I am beginning to see what all the discussion is about... finding that
balance.
Dave
--------
Dave
701-wannabe-soon
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=338639#338639
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