The Murphy Builders Site

Hi Drew

"some" airplanes not the Rebel ;) Yes this thing comes down pretty steep.
If my VSI is accurate, I get about 8 or 900 fpm at 60 knots which is
about a 7:1 glide ratio. Barely over a mile glide from 1,000 ft with no
wind once I'm back to 60 kts. It sure doesn't seem like much but small
Cessna's are also only about 8:1 glide ratio aren't they ??? It is nice
to be going so slow if you do have to put it in a field though.

Cecil was saying that he has MAM researching slightly thicker amphib
nose gear legs due to a couple of incidents he's seen of bent/ broken
legs where the bolt goes sideways through the 5/8" thick leg. Apparently
the legs are high strength 7075 aluminum. I am beginning to think that
it is not the best idea to operate the amphibs on grass strips!

Ken

Drew Dalgleish wrote:

I had some fun and expanded the flight testing a bit this morning. A
windmilling 3 blade Warp prop seems to be a fair bit of drag at cruise
speed on 119R as expected, but at 60 knots there is surprisingly little
difference in descent rate between slow idle (600 prop rpm with closed
throttle) and a stopped prop. Some airplanes glide significantly farther
with a stopped prop but apparently mine is not one of them.

Ken

Hi Ken I don't think you should ever use the term significant glide when
refering to any rebel :)
Drew

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It would be interesting to hear glide ratio/best glide data from those
who have installed Angus McKenzie's STOL cuffs or the Harrison vortex
generators.

Ron
254R

PS - Traveling near Arlington, WA, now and headed to Sequim, WA area
over weekend.

It would be interesting to hear glide ratio/best glide data from those
who have installed Angus McKenzie's STOL cuffs or the Harrison vortex
generators.

Ron
254R

PS - Traveling near Arlington, WA, now and headed to Sequim, WA area
over weekend.






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From: Garry Wright <wrightdg@davincibb.net>
Sent: Sep 28, 2006 12:01 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] glide ratio

Just some further comments on measurements I did with FOKM on wheels. At
60 mph I get about 1000 fpm measured using a watch and the altimeter. At
70 mph it descends slightly faster vertically and I figure its a wash
for speed vs distance under no wind conditions. For engine out purposes,
I use 1 mile per minute and 1000 fpm which works out to 5:1 for
practical purposes. My 172M was 7:1 but I never did measure it so am a
bit skeptical of that at this stage. It doesn't give you a lot of time
or distance before you are on the ground but in practice, neither do the
certified aircraft.

Wayne used FOKM on grass with the amphibs for 4 years. I will look at
the floats and see if I can spot anything.

Garry

On Thu, 2006-09-28 at 11:34 -0400, Ken wrote:

Hi Drew

"some" airplanes not the Rebel ;) Yes this thing comes down pretty steep.
If my VSI is accurate, I get about 8 or 900 fpm at 60 knots which is
about a 7:1 glide ratio. Barely over a mile glide from 1,000 ft with no
wind once I'm back to 60 kts. It sure doesn't seem like much but small
Cessna's are also only about 8:1 glide ratio aren't they ??? It is nice
to be going so slow if you do have to put it in a field though.

Cecil was saying that he has MAM researching slightly thicker amphib
nose gear legs due to a couple of incidents he's seen of bent/ broken
legs where the bolt goes sideways through the 5/8" thick leg. Apparently
the legs are high strength 7075 aluminum. I am beginning to think that
it is not the best idea to operate the amphibs on grass strips!

Ken

Drew Dalgleish wrote:

Hi Ken I don't think you should ever use the term significant glide when
refering to any rebel :)
Drew

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It would be interesting to hear glide ratio/best glide data from those
who have installed Angus McKenzie's STOL cuffs or the Harrison vortex
generators.

Ron
254R

That 7:1 that I mentioned is with the STOL cuffs and. Wouldn't expect
much difference but now that Garry has posted his numbers I will have to
get out a stopwatch and see how accurate my VSI is.
Ken

rshannon@cruzcom.com wrote:

It would be interesting to hear glide ratio/best glide data from those
who have installed Angus McKenzie's STOL cuffs or the Harrison vortex
generators.

Ron
254R

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I would be very interested to get the data Ken. That stol cuff is
strongly recommended by various people but I have not seen any numbers
yet.

Garry

On Thu, 2006-09-28 at 17:20 -0400, Ken wrote:

That 7:1 that I mentioned is with the STOL cuffs and. Wouldn't expect
much difference but now that Garry has posted his numbers I will have to
get out a stopwatch and see how accurate my VSI is.
Ken

rshannon@cruzcom.com wrote:

It would be interesting to hear glide ratio/best glide data from those
who have installed Angus McKenzie's STOL cuffs or the Harrison vortex
generators.

Ron
254R

Garry and Ron

I finally got out with a stop watch this morning. With Angus's STOL
cuffs and Dave's hoerhner wing tips I have confirmed close to 700 fpm
descent at 60 and 65 knots with 0 flap. With my geared engine I again
saw no appreciable difference at slow idle or with the prop stopped. So
I figure about 6.5 to 1 glide ratio. That was at about 1370 lbs so it
might be a tiny bit better at gross weight. Higher weight usually means
more stored energy= glide a bit further...

Ken

Garry and Ron

I finally got out with a stop watch this morning. With Angus's STOL
cuffs and Dave's hoerhner wing tips I have confirmed close to 700 fpm
descent at 60 and 65 knots with 0 flap. With my geared engine I again
saw no appreciable difference at slow idle or with the prop stopped. So
I figure about 6.5 to 1 glide ratio. That was at about 1370 lbs so it
might be a tiny bit better at gross weight. Higher weight usually means
more stored energy= glide a bit further...

Ken

Garry Wright wrote:

I would be very interested to get the data Ken. That stol cuff is
strongly recommended by various people but I have not seen any numbers
yet.

Garry

On Thu, 2006-09-28 at 17:20 -0400, Ken wrote:

That 7:1 that I mentioned is with the STOL cuffs and. Wouldn't expect
much difference but now that Garry has posted his numbers I will have to
get out a stopwatch and see how accurate my VSI is.
Ken

rshannon@cruzcom.com wrote:

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Garry and Ron

I finally got out with a stop watch this morning. With Angus's STOL
cuffs and Dave's hoerhner wing tips I have confirmed close to 700 fpm
descent at 60 and 65 knots with 0 flap. With my geared engine I again
saw no appreciable difference at slow idle or with the prop stopped. So
I figure about 6.5 to 1 glide ratio. That was at about 1370 lbs so it
might be a tiny bit better at gross weight. Higher weight usually means
more stored energy= glide a bit further...

Ken

Ken,

Do you have any special drag reduction efforts on your plane? I'm
wondering if one can really attribute that much difference (between 1000
fpm and 700 fpm) to the cuffs and tips. I will have to try a little
higher speed for the descent. It seems to me that at 65 knots my descent
rate is even higher than 1000 fpm. More tests are in order at my end
perhaps.

Garry

On Wed, 2006-11-15 at 16:46 -0500, Ken wrote:

Garry and Ron

I finally got out with a stop watch this morning. With Angus's STOL
cuffs and Dave's hoerhner wing tips I have confirmed close to 700 fpm
descent at 60 and 65 knots with 0 flap. With my geared engine I again
saw no appreciable difference at slow idle or with the prop stopped. So
I figure about 6.5 to 1 glide ratio. That was at about 1370 lbs so it
might be a tiny bit better at gross weight. Higher weight usually means
more stored energy= glide a bit further...

Ken

Nothing special for drag reduction Gary other than my cooling system. I
have a fairing covering the gap between the inner and outer flaperon
section. Also steel compression springs instead of bungee cords. I have
very little airflow through the cowl but I have that large radiator duct
under the fuselage. I'd guess that I have similar cooling drag to many
Lycomings although quite possibly less than the ones with the large
exit flap below the cowl. From what I'm seeing, I'd guess that a big
difference may be that the higher Lycoming idle speed might cause
significantly more drag while gliding. It surprised me that while RRD
slows quickly if you pull off power in cruise, the high prop drag seems
to go away as the speed comes back and the Warp drive slows to about 700
prop rpm. Sounds counter intuitive but power in or out of the crankshaft
is of course proportional to rpm and torque. I've got lower gliding idle
prop rpm which I think is key. (although I'd also guess that it does not
take any more torque to turn my engine over than for a Lycoming as I
have less than half the displacement, less than a 2:1 gear ratio, and I
think lower piston speeds.)

My WAG would be that yes the wingtips could reduce drag enough to be
noticeable but the cuffs probably don't do much either way at 65 knots.
C of G will also affect it a bit. It seems that I pretty much always
have a bit of up elevator deflection even though I reduced the stab
incidence a bit. Aircraft with an aft c of g should have slightly less
drag. I think the cuffs do make it much more comfortable to fly at very
low airspeeds for STOL work but that is based on experience with the
4415 aerofoil on other aircraft, as I've never flown a Rebel without the
cuffs. If you can ignore the ridiculous nose up attitude, I'm
comfortable down to 40 knots (46 mph) and even then it is still easilly
controlled with rudder as it starts to sink below 40 knots. I've
confirmed that speed with gps. And it will go airborne at 40 knots.
(You should have seen the size of my daughter's eyes when she added
power and it launched from the 3 point attitude on her during a touch
and go ;)

I really like the instant thrust from this water cooled (thermostat),
geared and electronically injected engine with a light carbon prop. This
thing has never hesitated or missed a beat (so far...) and having no
engine controls except the throttle is nice. We could not really count
on getting that kind of instant thrust out of the radial engines if
things got hairy on short final and the throttle had already been closed.
Ken

Garry Wright wrote:

Ken,

Do you have any special drag reduction efforts on your plane? I'm
wondering if one can really attribute that much difference (between 1000
fpm and 700 fpm) to the cuffs and tips. I will have to try a little
higher speed for the descent. It seems to me that at 65 knots my descent
rate is even higher than 1000 fpm. More tests are in order at my end
perhaps.

Garry

On Wed, 2006-11-15 at 16:46 -0500, Ken wrote:

Garry and Ron

I finally got out with a stop watch this morning. With Angus's STOL
cuffs and Dave's hoerhner wing tips I have confirmed close to 700 fpm
descent at 60 and 65 knots with 0 flap. With my geared engine I again
saw no appreciable difference at slow idle or with the prop stopped. So
I figure about 6.5 to 1 glide ratio. That was at about 1370 lbs so it
might be a tiny bit better at gross weight. Higher weight usually means
more stored energy= glide a bit further...

Ken

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Thanks Ken. I'm away from FOKM for the next few weeks and its pretty
cold in my unheated hangar. Will have to wait for a chinook to try
anything I guess.

Garry

On Sat, 2006-11-18 at 10:01 -0500, Ken wrote:

Nothing special for drag reduction Gary other than my cooling system. I
have a fairing covering the gap between the inner and outer flaperon
section. Also steel compression springs instead of bungee cords. I have
very little airflow through the cowl but I have that large radiator duct
under the fuselage. I'd guess that I have similar cooling drag to many
Lycomings although quite possibly less than the ones with the large
exit flap below the cowl. From what I'm seeing, I'd guess that a big
difference may be that the higher Lycoming idle speed might cause
significantly more drag while gliding. It surprised me that while RRD
slows quickly if you pull off power in cruise, the high prop drag seems
to go away as the speed comes back and the Warp drive slows to about 700
prop rpm. Sounds counter intuitive but power in or out of the crankshaft
is of course proportional to rpm and torque. I've got lower gliding idle
prop rpm which I think is key. (although I'd also guess that it does not
take any more torque to turn my engine over than for a Lycoming as I
have less than half the displacement, less than a 2:1 gear ratio, and I
think lower piston speeds.)

My WAG would be that yes the wingtips could reduce drag enough to be
noticeable but the cuffs probably don't do much either way at 65 knots.
C of G will also affect it a bit. It seems that I pretty much always
have a bit of up elevator deflection even though I reduced the stab
incidence a bit. Aircraft with an aft c of g should have slightly less
drag. I think the cuffs do make it much more comfortable to fly at very
low airspeeds for STOL work but that is based on experience with the
4415 aerofoil on other aircraft, as I've never flown a Rebel without the
cuffs. If you can ignore the ridiculous nose up attitude, I'm
comfortable down to 40 knots (46 mph) and even then it is still easilly
controlled with rudder as it starts to sink below 40 knots. I've
confirmed that speed with gps. And it will go airborne at 40 knots.
(You should have seen the size of my daughter's eyes when she added
power and it launched from the 3 point attitude on her during a touch
and go ;)

I really like the instant thrust from this water cooled (thermostat),
geared and electronically injected engine with a light carbon prop. This
thing has never hesitated or missed a beat (so far...) and having no
engine controls except the throttle is nice. We could not really count
on getting that kind of instant thrust out of the radial engines if
things got hairy on short final and the throttle had already been closed.
Ken

Garry Wright wrote:

Ken,

Do you have any special drag reduction efforts on your plane? I'm
wondering if one can really attribute that much difference (between 1000
fpm and 700 fpm) to the cuffs and tips. I will have to try a little
higher speed for the descent. It seems to me that at 65 knots my descent
rate is even higher than 1000 fpm. More tests are in order at my end
perhaps.

Garry

On Wed, 2006-11-15 at 16:46 -0500, Ken wrote:

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