Thanks for asking the question and posting the response David.
I understand where Jiri was coming from on this, although the usual
recommendation is to optimise prop blade twist for the "service" condition,
which means 'cruise', where it spends most of its working life.
With a VP prop and with the inverse-cube relationship between power and
performance, there would be little detectable difference in climb or top
speed with different blade twist optimisations, as Jiri points out.
However, if in the cruise the prop is running at 83% efficiency rather than
an off-optimum 75%, then fuel economy would be improved by 10%. That's 450
gallons of fuel over the life of the engine!
Regards,
Duncan.
----- Original Message -----
From: "David Joyce" <davidjoyce@doctors.org.uk>
Subject: Re: Europa-List: Woodcomp/Kremen propellers
<davidjoyce@doctors.org.uk>
>
> Duncan, They never had one. At one stage they expressed an interest but
FD's
> 3yr stipulation put them off and in any case Kremen prefer the idea of
> Connair.
> I talked to Jiri about yourprop design paper. He said it was
long
> and the English complex but he felt it didn't simply extend from 2 blade
> props to 3 and to props with differnt secions. I think he implied that all
> props should be optimised for the climb phase which is more critical
unless
> you are into racing. Finally he said that a firm (whose name he gave me
but
> I have forgotten) tested the kremen SR2000 and the Rospeller for their new
> fibreglass plane. The Rospeller has significantly more twist than the
> Kremen. They found that climb & cruise performance were identical but
engine
> cooling was worse with the Rospeller, so they have chosen the Kremen.
Sorry
> I did not get time (in what turned out to be a hectic schedule) to push
him
> to produce a more in depth critique of the paper.
> Cheers, David----- Original Message -----
> From: Duncan McFadyean <ami@mcfadyean.freeserve.co.uk>
> To: <europa-list@matronics.com>
> Subject: Re: Europa-List: Woodcomp/Kremen propellers
>
>
> <ami@mcfadyean.freeserve.co.uk>
> >
> > What happened to ST Aviation's Kremin agency?
> >
> > Duncan McF.
> > ----- Original Message -----
> > From: "David Joyce" <davidjoyce@doctors.org.uk>
> > To: "Europa list" <europa-list@matronics.com>
> > Subject: Europa-List: Woodcomp/Kremen propellers
> >
> >
> > <davidjoyce@doctors.org.uk>
> > >
> > > I am pleased to say that Frances Donaldson has just increased the
blade
> > life limit on the SR2000 prop from 3 yrs to 6 yrs and said he expects to
> be
> > able to remove that limit altogether in a couple of years or so. This
has
> > made it a commercial proposition to sell them in the UK and a major
player
> > in the UK GA marketpkace is pursuing the possibility of becoming their
> > agent.
> > > The Europa 6 Nations tour ( G-HOFC, G-RIXS, G-PTAG, G-NEAT &
> > G-XSDJ) visited the Kremen factory last week and were impressed and
> > unanimous that when their current props gave up they would reequip with
a
> > Kremen. I understand that Bryan Alsop has just bought one for 2600 Euros
> > which included spinner, wiring, CS unit, delivery and instruments, with
> > total weight of 9.8 Kg
> > > David Joyce, G-XSDJ
> > >
> > >
> >
> >
> > ________________________________________________________________________
> > Doctors.net.uk e-mail protects you from viruses and unsolicited messages
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> >
> >
>
>
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