On Fri, 06 Aug 2004 16:38:31 +0200, Stefan
wrote:

Rick Durden wrote:

requirements such as slower turning, shorter props and more effective
mufflers. It won't be fun.

Why won't it be fun? What's the fun of making a lot of noise and
embarrassing the neighbours? Effective mufflers already exist, three or
four blade props already exist, and it make a huge difference without
any negative side effect.

Where have you been? There are several negatives. Speed and fuel
consumption for a trip. Lower RPM means less HP.

The idea is not to make noise, but to gain efficiency.

The more blades you add to a prop the less efficient. You do gain
climb, but you lose cruise and take more fuel.

Going from a 2 to a three blade prop greatly quieted the Deb, but it
lost about 4 knots top end. Normally you are talking more HP to swing
more blades. Now, if you go to a monster airfoil like the 3-blade
used on Rare Bear, it turns slower and makes less noise than the high
RPM props at the races, but it is *huge*.

BTW, the 3-blade prop on mine weighs 83#. It replaced a 57# 2-blade.
It also cost $8800 exchange and that was nearly 10 years ago.

The most efficient exhaust system is a tuned exhaust and they are not
quite.

One example is http://www.airliners.net/open.file/231156/M/

No, this is an example of a muffler on a light, slow, airplane, not
something with speed. I travel 500 to 1200 miles. I don't want to do
it at 120 MPH. OTOH I normally do it at 5,000 to 8000 feet although
my last trip was over a month ago and most of it was at 2800 due to
the ceilings and airspace.

Just opening the cowl flaps costs me 20 to 30 knots. Imagine what
something like that hanging out would do. Putting the gear down feels
like some one put on the brakes and turned it into a very expensive
Cherokee that burns a lot of gas. With the gear down top speed is
less than the 140 MPH gear down speed. With the gear up and cowl
flaps closed, cruise is a160 knots true at ~6,000 feet.

Currently from Central Michigan I can normally beat the airlines to
Denver or Central Florida as there are no direct flights from here. I
may be slower than they are and I may have to stop once for a potty
break and to top off the tanks, but I'm still usually an hour faster.
That was before 9/11. Now I'm probably 2 hours faster but I've not
had the chance to get to Denver in a couple of years..


Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com




Stefan