Roland, I would not for a moment knock the benefits of having better
designed cowlings and internal cooling air flow arrangements. If I were
starting again I would go down that course as well as having a high
twist prop. The most impressive cowling design I have come across is the
beautiful one Nigel Graham has produced for his Callisto Europa variant.
However as a fix, a high twist prop seems comparitively cheap and easy
(Dutch authorities apart!) and has the added benefit of improved
performance.
For interest I have worked out the 'natural air flow rate' past the tip
and 1/3 radius points of my two props when they are idling in fine pitch
at 1700 engine rpm:
Low twist tip (31 deg) 69kts 1/3 R (43 deg) 35.7 kts
High twist Tip (23 deg) 49kts 1/3 R (49 deg) 44.2kts
You will see that the low rwist blade is trying to produce an airflow at
its tip almost twice that at its inner part, whereas the flow on the
high twist blade is relatively unifofm along its length. I am not an
aerodynamicist, so cannot say just what effect that might have, but
would be surprised if it does not result in a significant diversion of
air flow out from the central portion which of course contains the
colling air inlets. These figures are for the Woodcomp props, but Warp
Drive and other low twist blades must provide very similar results.
Regards, David Joyce, GXSDJ
On 2016-07-28 23:20, zwakie wrote:
>
> Hi Roland,
>
> Roland wrote:
>
>> ...that I thought of something cheaper than a new propeller. I even would
>> consider
this, when it would be "only" the money provided it's a reliable solution.
But since my Europa is on the Dutch register, I'd expect considerable paperwork
with the authorities going along with additional costs.
>
> This might be easier than you might think: if I remember correctly, PH-DIY has
this engine/prop combination (2-blade version I think).
>
> Roland wrote:
>
>> ...I have to stick to more or less easy solutions like removing the
>> thermostate
first.
>
> How is removing the water thermostat going to help? With CT temps over 85C
> it's
wide open, isn't it? With CHT's way up high, it is fair to assume that CT temps
are well above 85C. I would not expect you're getting more coolant to flow
by removing the thermostat and don't see how this is going to help you to bring
the CHT's down...
>
> One option you could consider, but only worthwhile looking at if you your
> oil-temps
are 'well below' red-line: an oil-water heat exchanger. This would allow
you to use the excess cooling capacity of your oil radiator to bring down CHT
indirectly (additional benefit of this approach a.o. is your oil temp will be
above 50C quicker after startup)
>
> --------
> Marcel Zwakenberg
> XS TG || 912ULS || PH-SBR
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=458847#458847 [1]
>
Links:
------
[1] http://forums.matronics.com/viewtopic.php?p=458847#458847
[2] http://www.matronics.com/Navigator?Europa-List
[3] http://forums.matronics.com
[4] http://wiki.matronics.com
[5] http://www.matronics.com/contribution
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