Earthstar Forums

Thanks Mark
I understand and its good advice.
Fred

Your going to have to rename your plane to "Greased Lightning"

Cool! I might do that!

kb

I did a little research a few years back on wheel pants design. The best author I found,  had done a lot of testing and says ones similar to the ones in these links have the least drag. It has a lot to do with air cleanly leaving the trailing edge.

http://ar-5.com/gallery/AR-5/wheelpantrear
http://ar-5.com/gallery/AR-6/reno_still_18

Look at stills # 2, 3, 4, 6 and 13 at what they did to get the air to break away from the trailing edges and especially where the wings atach to the fuselage.

I recall in the original article I read about Arnolds AR-5, he mentioned the "Coke bottle" shape used so commonly now for fast plane fuselages and used it on both the 5 and twice on the 6. The engine air exhaust ducts were carefully designed to help reduce drag and increase the effect of the fuselage shape on te AR-5. I wonder if a little thin in the middle would help a wheel pant.
Maybe some inlet ducts at the front of the fuselage and numerous small slits before the trailing edge to help the air break away.
There used to be a great article written by Mike about how and why etc. but I don't see it now. Instead, I see disks for sale. Go figure. ;-) I may look on my old computer to see if I have it saved there.
Loren

I think that given our airspeeds, that the usual shaped ones available from Aircraft Spruce, and from our look-a-like airplane mfr. would be just fine. Now if I were persuing 200mph+, I would start looking at optimum shapes. But hey, if your creative with fibreglass, anything is possible. For me, I just want to bolt on ( with a few holes drilled) set of reasonable priced pants.

kb

In a message dated 2/24/2011 7:25:19 PM Pacific Standard Time,
meflyslo@yahoo.com writes:


I did a little research a few years back on wheel pants design. The best
author I found, had done a lot of testing and says ones similar to the ones
in these links have the least drag. It has a lot to do with air cleanly
leaving the trailing edge.

http://ar-5.com/gallery/AR-5/wheelpantrear
http://ar-5.com/gallery/AR-6/reno_still_18

Look at stills # 2, 3, 4, 6 and 13 at what they did to get the air to
break away from the trailing edges and especially where the wings atach to the
fuselage.

I recall in the original article I read about Arnolds AR-5, he mentioned
the "Coke bottle" shape used so commonly now for fast plane fuselages and
used it on both the 5 and twice on the 6. The engine air exhaust ducts were
carefully designed to help reduce drag and increase the effect of the
fuselage shape on te AR-5. I wonder if a little thin in the middle would help a
wheel pant.
Maybe some inlet ducts at the front of the fuselage and numerous small
slits before the trailing edge to help the air break away.
There used to be a great article written by Mike about how and why etc.
but I don't see it now. Instead, I see disks for sale. Go figure. ;-) I may
look on my old computer to see if I have it saved there.
Loren





Hi Loren
The "Coke Bottle" shape is called the area rule. It has to do with the area
of the exposed surfaces on an aircraft and the way they interact with the
mass flow around the aircraft. The wing causes Pressure deference's on the
fuselage and it turns out that narrowing the fuselage at the point were the
wing is imposing its effects on it works to reduce the size of the mass
flow disturbance. If you think of an airplane traveling through the
undisturbed air and causing a bubble of pressure and a turbulent wake behind it that
is reduced pressure sucking it bakwords. than any thing that is done to
reduce the volume of the disturbance results in increased speed without
addition of more power.
Happy Flying
Mark

I wonder what % of the wheel pant efficiency
would be achieved by a wheel afterbody?

-Alan Cossitt

>From my iPhone. Please excuse typos and terseness.

Thanks Mark, I followed the automobile speed record attempts for years and was a mechanic on mach 2 jet aircraft for several years so I know how important shapes become at high speed. Change the shape some and get more speed but it soon comes down to more HP. As you all know already, it takes a lot more HP at 100 mph to gain another mph than it does at 50mph so instead why not cut down on drag and the wheel pants are about the only place left on the TG etc.
I am not totally stupid, I know why you designed your planes with the engine back where it is and I have loved them from the very start.

Do you know if Paul McDonald ever made his main gear pants?
Before he moved to AZ, he landed at my place with his new nose gear pant and it looked awesome. He brought it up before he installed it to show me the job he did and I was very impressed indeed. It was made in two pieces and designed to separate (horizontally, not lengthwise) for removal and installation. It was tiny compared to the ones Aircraft Spruce sells. He bought a DVD on glass layup and followed it step by step.
BTW, the nose gear was narrowed some so the pant could be made even narrower.
Loren

Hi Alan
I would guess about 80%.
Mark


In a message dated 2/25/2011 10:32:33 A.M. Pacific Standard Time,
alan.cossitt@frontier.com writes:

I wonder what % of the wheel pant efficiency
would be achieved by a wheel afterbody?

-Alan Cossitt

Hi Loren
I am sorry if I made you think that I was saying you were stupid. that is
certainly not what I mean to say. Nor is it how I feel.
Paul has sold his plane and ordered another one. this one he is building
from a kit but has spent much time in the shop drilling lighting holes in
the lighting holes. and has knocked about 10 lb out of it all ready.
Hi is the one that I gave my wheel pant molds to finish up. so if he has
time they should be really slick. if you don't have his contact info I can
get that for you.
Happy Flying,

Mark

In a message dated 2/25/2011 11:15:39 A.M. Pacific Standard Time,
meflyslo@yahoo.com writes:






--- In _Earthstar_Aircraft@yahoogroups.com_
(mailto:Earthstar_Aircraft@yahoogroups.com) , thundergul@... wrote:

>
>
> Hi Loren
> The "Coke Bottle" shape is called the area rule. It has to do with the
area
> of the exposed surfaces on an aircraft and the way they interact with
the
> mass flow around the aircraft. The wing causes Pressure deference's on
the
> fuselage and it turns out that narrowing the fuselage at the point were
the
> wing is imposing its effects on it works to reduce the size of the mass
> flow disturbance. If you think of an airplane traveling through the
> undisturbed air and causing a bubble of pressure and a turbulent wake
behind it that
> is reduced pressure sucking it bakwords. than any thing that is done to
> reduce the volume of the disturbance results in increased speed without
> addition of more power.
> Happy Flying
> Mark
>

Thanks Mark, I followed the automobile speed record attempts for years and
was a mechanic on mach 2 jet aircraft for several years so I know how
important shapes become at high speed. Change the shape some and get more speed
but it soon comes down to more HP. As you all know already, it takes a lot
more HP at 100 mph to gain another mph than it does at 50mph so instead
why not cut down on drag and the wheel pants are about the only place left on
the TG etc.
I am not totally stupid, I know why you designed your planes with the
engine back where it is and I have loved them from the very start.

Do you know if Paul McDonald ever made his main gear pants?
Before he moved to AZ, he landed at my place with his new nose gear pant
and it looked awesome. He brought it up before he installed it to show me
the job he did and I was very impressed indeed. It was made in two pieces and
designed to separate (horizontally, not lengthwise) for removal and
installation. It was tiny compared to the ones Aircraft Spruce sells. He bought a
DVD on glass layup and followed it step by step.
BTW, the nose gear was narrowed some so the pant could be made even
narrower.
Loren