Duncan, when I wrote my article I was not able to come by
any definition of twist so took the difference in pitch at
tip and 1/3 radius. If you are measuring somewhere else
then it isn't possible to make comparisons, but at the
time Europa Warp drive blades were around 12 degrees
measured thus.
Regards, David
"Duncan & Ami" <ami-mcfadyean@talktalk.net> wrote:
><ami-mcfadyean@talktalk.net>
>
> <<.whereas 12 degrees (your Warp drive blade)>>
> David the Warp has 19.5 degrees twist at 72" diameter,
>as measured to the
> point that the undersurface no longer has a point that
>is flat. All other
> incarnations of the Warp Drive come from the same mould
>and are cut down to
> the required size.
> Removing 5" from the tip of a Warp Drive takes off about
>1.75 degree of
> twist; I have some tips spare if you'd like one!
>
> Whilst this twist is measured from the point adjacent to
>the root where the
> underside still has a flat area; it could be argued that
>measuring from
> closer to the root where there is at least a 3:1
>symmetrical airfoil section
> will indicate more twist.
>
> Not forgetting that an asymmetrical aerofoil will need
>at least a few
> degrees of negative incidence before it starts to
>generate 'reverse thrust'.
> I agree that there's not enough!
>
> The fixed pitch Arplast has more twist (about 22
>degrees), and other
> versions (the faster VP blade) more still.
>
>
>
> Duncan McF.
>
> -----Original Message-----
>From: owner-europa-list-server@matronics.com
> [mailto:owner-europa-list-server@matronics.com] On
>Behalf Of David Joyce
> Sent: 25 August 2012 12:20
> To: europa-list@matronics.com
> Subject: Re: Europa-List: Re: Landing mishap/ prop twist
>
>
> --> <davidjoyce@doctors.org.uk>
>
> Duncan, As all Europa props are close to 1600mm it makes
> very little difference. The actual maths are set out in
> the article 'Does propeller twist matter?' in Europa
>Flyer
> no 65 (available like all back numbers on the beautiful
> new Europa Club website at
> www.theeuropaclub.org/the-club/europa-flyer/ ). For a
> 1600mm prop, the amount of twist needed rises rapidly
>from
> 6 degrees at 20 kts to 24 at 100kts but then levels off
>to
> just 29 degrees at 160 kts before coming down somewhat
>at
> higher speeds. As the curve flattens out in the working
> range an increase in diameter just moves you marginally
> along this relatively flat segment. In practice 26
> degrees is within 3 degrees of optimal for speeds
>between
> 90 odd kts and 200+ kts, whereas 12 degrees (your Warp
> drive blade) is optimal for sitting stationary on the
> ground with the throttle half open (this giving an
>airflow
> of 40kts past the cock[pit!)
> Regards, David
>
>
> "Duncan & Ami" <ami-mcfadyean@talktalk.net> wrote:
>><ami-mcfadyean@talktalk.net>
>>
>> You'll also need to measure the diameter for any
>>meaningful comparison;
>> generally, as diameter increases, the required overall
>>prop twist along the
>> blade needs to be slightly less.
>> Then there's the fact that most manufactured blades in
>>our class of use
>> (e.g. Warp Drive, Arplast) start off as a larger
>>diameter prop (with a
>> better amount of twist) which is then cut down to the
>>required diameter.
>> This of course removes twist, usually to well below the
>>optimum!
>>
>> Duncan McF.
>>
>> -----Original Message-----
>>From: owner-europa-list-server@matronics.com
>> [mailto:owner-europa-list-server@matronics.com] On
>>Behalf Of zwakie
>> Sent: 21 August 2012 20:57
>> To: europa-list@matronics.com
>> Subject: Europa-List: Re: Landing mishap - asking for
>>advise
>>
>>
>><mz@cariama.nl>
>>
>> David, Graham and others,
>>
>> I will take it upon myself to come up with the numbers
>>on the twist of the
>> Arplast PV50 and publish them here in due time.
>>
>> --------
>> Marcel
>> (Europa Classic Tri-Gear PH-MZW)
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=381475#381475
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>Un/Subscription,
>>Forums!
>>Admin.
>>
>>
>>
>
>
>
>
>
>
>
>
>Un/Subscription,
>Forums!
>Admin.
>
>
>
|