Anyone know a good way to make a belly baggage pod?

[Tedstriker]

My Jurca Sirocco has so little baggage space, that it really needs
some extra room. I'd like to make a bomb-shaped belly pod, and have
seen some made on other homebuilts. I've heard of some of the Pitt's
S-1 guys welding two spinners together, back to back, but that doesn't
have the look I want. I've got 4 quarter inch bolts that are on the
bottom of the belly that hold the pitot's seat down, and would be
perfec hard points to attach a pod to. I plan to fly to Oshkosh and it
would be great to have some extra room for stuff. I can't figure out
how to mold a shape like that. Any suggestions? I'm talanted in
fiberglass work, as I've been building a Glasair 3 for 14 years, --
still working on it. It would be great if someone made a pod I could
purchase.

[Tedstriker]

On Fri, 03 Jun 2005 07:51:38 -0700, Richard Riley
> wrote:

>On Fri, 03 Jun 2005 10:45:41 -0400, Tedstriker
> wrote:
>
>:My Jurca Sirocco has so little baggage space, that it really needs
>:some extra room. I'd like to make a bomb-shaped belly pod, and have
>:seen some made on other homebuilts. I've heard of some of the Pitt's
>:S-1 guys welding two spinners together, back to back, but that doesn't
>:have the look I want. I've got 4 quarter inch bolts that are on the
>:bottom of the belly that hold the pitot's seat down, and would be
>:perfec hard points to attach a pod to. I plan to fly to Oshkosh and it
>:would be great to have some extra room for stuff. I can't figure out
>:how to mold a shape like that. Any suggestions? I'm talanted in
>:fiberglass work, as I've been building a Glasair 3 for 14 years, --
>:still working on it. It would be great if someone made a pod I could
>:purchase.
>
>Gary Hunter has been making them for EZ's for
>years, 6.5' long and 12" diameter at the largest point. I understand
>he's got new molds for slightly bigger pods - 13.5" diameter.
>
>Featherlight also makes them
>

Thanks for the info Richard, I've sent them emails and hope to find a
design. For something like this, it makes more sense to buy an
off-the- shelf item, than to keep re-inventing the wheel and having to
make a mold for just one unit.

[Gig 601XL Builder]

If you made a belly pod that provided some lift could you not increase the
MGW of the aircraft?

I think of this because at lease some of the pontoons on the market "carry
thier own weight" so to speak and don't subtract from the aircrafts useful
load.


"Richard Riley" > wrote in message
...
> On Fri, 03 Jun 2005 10:45:41 -0400, Tedstriker
> > wrote:
>
> :My Jurca Sirocco has so little baggage space, that it really needs
> :some extra room. I'd like to make a bomb-shaped belly pod, and have
> :seen some made on other homebuilts. I've heard of some of the Pitt's
> :S-1 guys welding two spinners together, back to back, but that doesn't
> :have the look I want. I've got 4 quarter inch bolts that are on the
> :bottom of the belly that hold the pitot's seat down, and would be
> :perfec hard points to attach a pod to. I plan to fly to Oshkosh and it
> :would be great to have some extra room for stuff. I can't figure out
> :how to mold a shape like that. Any suggestions? I'm talanted in
> :fiberglass work, as I've been building a Glasair 3 for 14 years, --
> :still working on it. It would be great if someone made a pod I could
> :purchase.
>
> Gary Hunter has been making them for EZ's for
> years, 6.5' long and 12" diameter at the largest point. I understand
> he's got new molds for slightly bigger pods - 13.5" diameter.
>
> Featherlight also makes them
>
>

[Corky Scott]

On Fri, 3 Jun 2005 11:17:21 -0500, "Gig 601XL Builder"
<wr.giacona@coxDOTnet> wrote:

>If you made a belly pod that provided some lift could you not increase the
>MGW of the aircraft?
>
>I think of this because at lease some of the pontoons on the market "carry
>thier own weight" so to speak and don't subtract from the aircrafts useful
>load.

I've always wondered about that. Seems to me that works fine in the
air (although any additional flat plate area will of course affect
overall drag), but what about landing?

Also, in order for the pod to not contribute to the gross weight of
the airplane, wouldn't it have to be able to produce it's lift at the
time of takeoff? And if it's doing that, will it add a lot of drag at
cruise?

Corky Scott

[Gig 601XL Builder]

"Corky Scott" > wrote in message
...
> On Fri, 3 Jun 2005 11:17:21 -0500, "Gig 601XL Builder"
> <wr.giacona@coxDOTnet> wrote:
>
>>If you made a belly pod that provided some lift could you not increase the
>>MGW of the aircraft?
>>
>>I think of this because at lease some of the pontoons on the market "carry
>>thier own weight" so to speak and don't subtract from the aircrafts useful
>>load.
>
> I've always wondered about that. Seems to me that works fine in the
> air (although any additional flat plate area will of course affect
> overall drag), but what about landing?
>
> Also, in order for the pod to not contribute to the gross weight of
> the airplane, wouldn't it have to be able to produce it's lift at the
> time of takeoff? And if it's doing that, will it add a lot of drag at
> cruise?
>
> Corky Scott

I building a Zenith 601XL and it has a fairly thick wing. I was thinking use
the same front and main ribs and build one that was about 3 feet long. sure
there would be additional drag but there would also be additional lift. The
question is how much lift would a three foot piece of wing mounted under the
fuselage produce?

If it is enough to overcome the weight of the wing and say 80 lbs of cargo
there would be times that I could live with the lower airspeed, higher Vr
and higher stall.

Gig G

P.S. Corky, your great to talk to when your not talking politics. :)

[Corky Scott]

On Fri, 3 Jun 2005 13:48:30 -0500, "Gig 601XL Builder"
<wr.giacona@coxDOTnet> wrote:

>P.S. Corky, your great to talk to when your not talking politics. :)

Heh heh, I'm great then too, you just don't like the answers. :-D

By the way, my engine is down again. When I assembled it (Ford V-6),
I noticed that the timing chain cover had a minor crack around one of
the tabs that bolts to the engine block. I didn't have another timing
chain cover as I'd discarded the spare engine I'd bought for parts
long before I noticed this problem. So I fixed it using a space age
epoxy I got from MSC. It duly hardened up like metal and could be
filed, machined or tapped, but it didn't seal the crack very well.
I'd flipped the timing chain upside down and poured the epoxy in so
that it hardened directly on top of the crack. I didn't do anything
with the crack on the outside of the cover.

Well that just didn't work. After running the engine for a while I
noticed oil on top of the timing chain cover right next to the crack.

So I pulled the cover, again (third time) and tested the epoxy. I
tapped on it with a screw driver and it sounded hollow. Not a good
sign. I got a small chisel and popped it a couple of times where it
was thick, where it mated with the block, and the entire piece popped
off.

Obviously, it hadn't bonded properly.

So the cover is at a local shop where a guy who knows how to weld
aluminum and who has a good TIG machines has agreed to run a bead on
the inside and outside to seal the crack. By the way, this crack is
in a non structural area, around a little tab that has a bolt hole in
it. It may have cracked due to some past ham handed mechanic trying
to remove the timing chain cover without first removing this bolt.
That's what the crack looks like, it kind of travels half way around
the tab.

Then it's back together with a fresh coat of paint and some long term
testing. I'll have to stand right next to the engine while it's
running to keep an eye on the guages so this will be interesting. I
guess I won't have to worry much about Mosquitos or Black Flies...

Corky Scott

[Morgans]

"Tedstriker" > wrote

> My Jurca Sirocco has so little baggage space, that it really needs
> some extra room. I'd like to make a bomb-shaped belly pod, and have
> seen some made on other homebuilts.

You could also go with a flat belly pod, like on some Caravans. Basically,
just a taper on front, and back, with flat between. Curved corners, a
door(s) on the side. Easily done with fiberglass with some 1/2" foam for
the core, with some blocks in the corners to give some room to radius the
outside corners. Easy shape to make, lots more storage space than a bomb,
and less wind resistance, I would think.
--
Jim in NC

[Morgans]

"Gig 601XL Builder" <wr.giacona@coxDOTnet> wrote

> I building a Zenith 601XL and it has a fairly thick wing. I was thinking
use
> the same front and main ribs and build one that was about 3 feet long.
sure
> there would be additional drag but there would also be additional lift.
The
> question is how much lift would a three foot piece of wing mounted under
the
> fuselage produce?

Damn little lift, I would think, because of the poor aspect ratio. Long
wings produce more lift, with less drag, and part of that is there is less
loss at the tips. All of a belly pod would be tips, practically speaking.
--
Jim in NC

[Morgans]

"Corky Scott" > wrote

> By the way, my engine is down again.

I got a small chisel and popped it a couple of times where it
> was thick, where it mated with the block, and the entire piece popped
> off.
>
> Obviously, it hadn't bonded properly.

I would think the real culprit is the different expansion rates of epoxy and
aluminum.
--
Jim in NC

[jls]

"Tedstriker" > wrote in message
...
> My Jurca Sirocco has so little baggage space, that it really needs
> some extra room. I'd like to make a bomb-shaped belly pod, and have
>

On one of Mike Arnold's AR-5 tapes he makes one, and you can watch and learn
to make one for yourself. Matter of fact, Arnold's meticulous techniques
are the best I have ever seen. He is a master at it, having trained with
another master, Burt Rutan.

IIRC, Arnold made a mold for baggage pod production for the RV series of
aircraft.

[Montblack]

( jls wrote)
[snip]
> IIRC, Arnold made a mold for baggage pod production for the RV series of
> aircraft.


That's a photo I would like to see.


Montbalck

[Pete Schaefer]

http://www.eaa1000.av.org/pix/rvpods.jpg

[Tedstriker]

>
>On one of Mike Arnold's AR-5 tapes he makes one, and you can watch and learn
>to make one for yourself. Matter of fact, Arnold's meticulous techniques
>are the best I have ever seen. He is a master at it, having trained with
>another master, Burt Rutan.
>
>IIRC, Arnold made a mold for baggage pod production for the RV series of
>aircraft.
>

That's interesting, where can one obtain those tapes?

[Tedstriker]

>
>You could also go with a flat belly pod, like on some Caravans. Basically,
>just a taper on front, and back, with flat between. Curved corners, a
>door(s) on the side. Easily done with fiberglass with some 1/2" foam for
>the core, with some blocks in the corners to give some room to radius the
>outside corners. Easy shape to make, lots more storage space than a bomb,
>and less wind resistance, I would think.


I've been thinking of just that type of pod. It would indeed hold more
than a round, bomb-shaped type. Not sure which one would be more drag
than the other. And my plane has a perfectly flat belly, so it would
take to that type of pod easily. Now I just have to figure on whether
to build in Epoxy or vinyl-ester resin. I guess it depends on the type
of foam used, since vinyl-ester disolves the foams used in the eze's.
Most of my experience has been with vinyl-ester, building my Glasair.
But I guess with Epoxy, you are free to use just about any type of
foam? Aren't the foams used in with epoxies a lot cheaper? But then
I've noticed that epoxy resin is more expensive than vinyl-ester.
Matter of fact, for a belly pod, I can just build it out of polyester
resin I can buy locally. One thing I wonder about is the exhaust.
A center mounted bomb pod would be between my exhaust pipes, but a
rectangular pod would be hit on both corners by engine exhaust. I
wonder if the heat would eat through the fiberglass?

[Morgans]

"Tedstriker" > wrote

> Aren't the foams used in with epoxies a lot cheaper?

Yep. you can get a 4' x 8' x 1/2" sheet for about 10 bucks, take or give a
couple. Get some 2" stuff, too, for the corners. To bend it for the taper,
take a straight edge, and lay it perpendicular to the fuselage, and make a
series of cuts with a utility kife, about halfway through. Put the cuts on
the outside of the curve, and experiment on how close you need to put them.

> But then
> I've noticed that epoxy resin is more expensive than vinyl-ester.
> Matter of fact, for a belly pod, I can just build it out of polyester
> resin I can buy locally.

Heavy, isn't it? Gotta keep this thing super light, right?

> One thing I wonder about is the exhaust.
> A center mounted bomb pod would be between my exhaust pipes, but a
> rectangular pod would be hit on both corners by engine exhaust. I
> wonder if the heat would eat through the fiberglass?

I think you would need to keep the pod slightly back from the center of
gravity, to keep the aerodynamic stability, and the weight and balance still
close. Slope the back side way back, to keep that side area behind the
center of pressure. If the front were a couple feet back from the pipes, I
would think that the turbulence from the propwash would have mixed enough
air with the exhaust, to keep it cool enough. I would think that the worst
that would happen, is that it might soften the epoxy a little, but it gets
hard again when it is cooled off. The inside layer of glass would be kept
cooler, from the insulating value of the foam.

It might be necessary to put a layer of aluminum on the front of it. I
really don't know how much of an issue this heat thing is, but my gut
feeling is, not much. Anyone else got any idea? A pipe extension, perhaps?

> Not sure which one would be more drag than the other. (Bomb pod type)

My guess is it would be close to a wash. A bomb pod has a mounting pylon,
and that is going to have intersection drag at two places. (the pylon to
wing, and pylon to pod) Wetted surface is low, but so is storage space.

The belly pod would have no intersection drag, and no more corners than
before. More wetted surface, but SO MUCH more storage. to me, that is the
biggest factor. Skis, tent poles, fishing rods, a few golf clubs, would all
fit in a belly pod.

Another thing you could plan on, is using the belly pod to hold some extra
tankage, for ferry flights. Gonna have to fly solo, with that option, most
likely. Make the top (side towards the fuselage) with a lightweight
removable panel (for waterproofing) and only include strong cross struts, or
tabs, for mounting it on the bolts to the plane. Gotta keep that weight
down, right? That way, you could drop the tank in through the top, and bolt
it up. You would need a electric fuel pump to transfer fuel.

Disclaimer: I am not an aerodynamic specialist, or an A and P. (or anything
else) Make all changes at your own risk, after consulting a specialist.
This is all more of a thought exercise, than anything else, for me. I did
stay at a Holiday Inn, last night! <g>
--
Jim in NC

[Charlie]

Pete Schaefer wrote:
> http://www.eaa1000.av.org/pix/rvpods.jpg
>
>
What Pete didn't mention is the minimal (possibly even positive) effect
on the gross weight capability of the wing due to using 2 wing mounted
pods instead of a single belly mounted pod.

[Pete Schaefer]

There's a lot I didn't mention. Like...getting the pods out of prop wash is
a good idea. Like, putting a pod on centerline increases back-end flow
separation (especially if it's designed to produce lift) and hence total
drag. Also, a shape other than the old bomb could be destabilizing in roll
(a positive increment to Cpbeta....could cause you problems in cross-wind
landings...). I could go on and on. But, in the end, the two wing-mounted
pods just look a lot cooler, so why bother with a centerline pod.

Pete


"Charlie" > wrote in message
. ..
> Pete Schaefer wrote:
> > http://www.eaa1000.av.org/pix/rvpods.jpg
> >
> >
> What Pete didn't mention is the minimal (possibly even positive) effect
> on the gross weight capability of the wing due to using 2 wing mounted
> pods instead of a single belly mounted pod.

[Lou]

Wow, was I off. I was trying to picture a pod, but this wasn't it. My
thought went to something that went on the bottom of the fuselage i.e.
bellypod.
I pictured something similar to an upside down ski rack that would hook
up to the bottom. Something that could be released at the push of a
lever in an emergency.
Something that, when released (standing still) would be an enclosed
unit for camping gear, golf clubs, ect.
Wow was I off.
Ron

Pete Schaefer wrote:
> http://www.eaa1000.av.org/pix/rvpods.jpg

[kumaros]

Lou wrote:
> Wow, was I off. I was trying to picture a pod, but this wasn't it. My
> thought went to something that went on the bottom of the fuselage i.e.
> bellypod.
> I pictured something similar to an upside down ski rack that would hook
> up to the bottom. Something that could be released at the push of a
> lever in an emergency.
> Something that, when released (standing still) would be an enclosed
> unit for camping gear, golf clubs, ect.
> Wow was I off.
> Ron
>
> Pete Schaefer wrote:
>
>>http://www.eaa1000.av.org/pix/rvpods.jpg
>
>
I'm planning of fitting a bellypack to the bottom of my Cozy
III, rectangular form, fitting to the lines of the plane,
contoured and streamlined fore and aft, dimensions something
like 20X40X80" (50X100X200cm), mainly dictated by the
dimensions of a Honda Dax moped on the one hand and the
dimensions of my little aluminum frame/inflatable pontoons
catamaran on the other hand. The pack will be built just
like the rest of the plane in foam core glass epoxy sandwich
construction, will be removable and hinged on one side like
the Cozy canopy.

[Lou]

Now thats what I had in mind.

[Thomas O'Grady]

In article >,
Tedstriker > wrote:

> >
> >You could also go with a flat belly pod, like on some Caravans. Basically,
> >just a taper on front, and back, with flat between. Curved corners, a
> >door(s) on the side. Easily done with fiberglass with some 1/2" foam for
> >the core, with some blocks in the corners to give some room to radius the
> >outside corners. Easy shape to make, lots more storage space than a bomb,
> >and less wind resistance, I would think.
>
> One thing I wonder about is the exhaust.
> A center mounted bomb pod would be between my exhaust pipes, but a
> rectangular pod would be hit on both corners by engine exhaust. I
> wonder if the heat would eat through the fiberglass?

I have a pod on my Cessna 206. It comes to a point on the front, but
the sides and bottom are all flat sheets and the corners have very
little radius, maybe 1 inch. It wraps up the side of the fuselage about
4 inches, so the bottom is actually flatter than the original. It is
less than 8 inches behind the exhaust. There is no problem with heat,
but when you fly in the rain, the lead in the exhaust mixes with the
steam coming through the cowling and you end up with two lead streaks a
foot wide on the bottom. It is hard to scrub off. It does affect the
air flow out of the cowl flaps and a two inch extension of cowl flap
travel is required.

[[email protected]]

The AR-5 tapes were advertised in Sport Aviation. I don't know if
Arnold still advertises them there. His address, as shown on the VHS
videotape cover:

The Arnold Company
1203 Wanda St.
Crockett, CA 94525

[Montblack]

("Thomas O'Grady" wrote)
[snip]
> I have a pod on my Cessna 206. It comes to a point on the front, but
> the sides and bottom are all flat sheets and the corners have very
> little radius, maybe 1 inch. It wraps up the side of the fuselage about
> 4 inches, so the bottom is actually flatter than the original. It is
> less than 8 inches behind the exhaust.


What's the approx size of your pod L-W-D?
(...forget the ends if that's an easier est. <g>)

How do you access it?

What did it cost in performance numbers before-and-after? Noticeable?

Oh, what's the back of your pod look like?

Thanks.


Montblack

[Tedstriker]

On Sat, 11 Jun 2005 12:04:35 -0700, Richard Riley
> wrote:

>On Sat, 04 Jun 2005 15:24:02 -0400, Tedstriker
> wrote:
>
>:
>:>
>:>On one of Mike Arnold's AR-5 tapes he makes one, and you can watch and learn
>:>to make one for yourself. Matter of fact, Arnold's meticulous techniques
>:>are the best I have ever seen. He is a master at it, having trained with
>:>another master, Burt Rutan.
>:>
>:>IIRC, Arnold made a mold for baggage pod production for the RV series of
>:>aircraft.
>:>
>:
>:That's interesting, where can one obtain those tapes?
>
>With the world's most obvious url - http://www.ar-5.com/tapes.html

I ended up ordering one of Gary Hunter's EZ pods. I'm goint to invert
it, so the more curved surface is on the bottom, and shortening the
pylon. With something like this, it's horribly inneffiencent to shape
a pod, glass it, then use it to make a mold, then finally make a
finished pod. He's already done all that, so all I'll have to do to
mount it, is a little fiberglass work. This must me a common issue
with tadem airplanes with two people in them. Side by side planes
really have a baggage space advantage. The RV-8 has the best baggage
space I've seen for a two-place tandem homebuilt.
Thanks to Richard Riley for the good tip on where to buy one, I should
have it installed for Oshkosh. All other advice and tips appreciated.

[Lou]

Is there a web address for these pods?

[Tedstriker]

>
>My pleasure. Did he have the bigger ones available yet?
>
>Sorry to hear about your drinking problem.

Yes, he has a "Mark IV" version that is larger. I ordered that one,
since I will use only one, instead of the 2 that go on EZE's. It's a
little over 13" in dia. and a few inches longer.

Still working on the drinking problem.

[Cy Galley]

Isn't the more curved on top to produce lift to offset the additional
weight?


"Tedstriker" > wrote in message
...
> On Sat, 11 Jun 2005 12:04:35 -0700, Richard Riley
> > wrote:
>
>>On Sat, 04 Jun 2005 15:24:02 -0400, Tedstriker
> wrote:
>>
>>:
>>:>
>>:>On one of Mike Arnold's AR-5 tapes he makes one, and you can watch and
>>learn
>>:>to make one for yourself. Matter of fact, Arnold's meticulous
>>techniques
>>:>are the best I have ever seen. He is a master at it, having trained
>>with
>>:>another master, Burt Rutan.
>>:>
>>:>IIRC, Arnold made a mold for baggage pod production for the RV series of
>>:>aircraft.
>>:>
>>:
>>:That's interesting, where can one obtain those tapes?
>>
>>With the world's most obvious url - http://www.ar-5.com/tapes.html
>
> I ended up ordering one of Gary Hunter's EZ pods. I'm goint to invert
> it, so the more curved surface is on the bottom, and shortening the
> pylon. With something like this, it's horribly inneffiencent to shape
> a pod, glass it, then use it to make a mold, then finally make a
> finished pod. He's already done all that, so all I'll have to do to
> mount it, is a little fiberglass work. This must me a common issue
> with tadem airplanes with two people in them. Side by side planes
> really have a baggage space advantage. The RV-8 has the best baggage
> space I've seen for a two-place tandem homebuilt.
> Thanks to Richard Riley for the good tip on where to buy one, I should
> have it installed for Oshkosh. All other advice and tips appreciated.

[Tedstriker]

On Mon, 13 Jun 2005 01:45:56 GMT, "Cy Galley" >
wrote:

>Isn't the more curved on top to produce lift to offset the additional
>weight?

With a round pod like that, there's no way it could produce any lift.
Any low pressure area that could be generated on the top, would be
instantly neutralized by air from the bottom just flowing around to
the top. To produce lift, it would require large, ugly end plates
along both middle-upper sides of the pod. I'd rather use a wing to
make lift.

[Marc J. Zeitlin]

Tedstriker wrote:

> With a round pod like that, there's no way it could produce any lift.

A very definitive statement, but incorrect. Not only is there a way,
but there's no way for it NOT to produce lift, if placed at the right
angle of attack.

> Any low pressure area that could be generated on the top, would be
> instantly neutralized by air from the bottom just flowing around to
> the top.

Not really. While it is certainly the case that this shape is an
inefficient producer of lift, even a blunt cylinder oriented
longitudinally into the airstream will produce lift if placed at a
positive angle of attack. Dirigibles and blimps produce lift at
positive AOA's.

>.... To produce lift, it would require large, ugly end plates
> along both middle-upper sides of the pod.

No, it wouldn't. They might make the lift production more efficient
(meaning that the lift curve slope might be steeper, and the Lift/Drag
ratio might be higher), but they're not necessary for the production of
lift.

>.... I'd rather use a wing to make lift.

As would we all.

--
Marc J. Zeitlin
http://marc.zeitlin.home.comcast.net/
http://www.cozybuilders.org/
Copyright (c) 2005

[Tedstriker]

On Mon, 13 Jun 2005 22:42:25 -0400, "Marc J. Zeitlin"
> wrote:

>Tedstriker wrote:
>
>> With a round pod like that, there's no way it could produce any lift.
>
>A very definitive statement, but incorrect. Not only is there a way,
>but there's no way for it NOT to produce lift, if placed at the right
>angle of attack.
>
>> Any low pressure area that could be generated on the top, would be
>> instantly neutralized by air from the bottom just flowing around to
>> the top.
>
>Not really. While it is certainly the case that this shape is an
>inefficient producer of lift, even a blunt cylinder oriented
>longitudinally into the airstream will produce lift if placed at a
>positive angle of attack. Dirigibles and blimps produce lift at
>positive AOA's.
>
>>.... To produce lift, it would require large, ugly end plates
>> along both middle-upper sides of the pod.
>
>No, it wouldn't. They might make the lift production more efficient
>(meaning that the lift curve slope might be steeper, and the Lift/Drag
>ratio might be higher), but they're not necessary for the production of
>lift.
>
>>.... I'd rather use a wing to make lift.
>
>As would we all.

A dirigble can produce some lift due to it's size, the air would
have so far to travel to get to the top to neutralize the low pressure
up there. But on 13" diameter cylinder, any lift produced would be so
insignificant, as to be barely measurable.

[Morgans]

"Tedstriker" > wrote

> A dirigble can produce some lift due to it's size, the air would
> have so far to travel to get to the top to neutralize the low pressure
> up there.

Incorrect. The reason the dirigble has noticible lift is not how far the
air has to travel, but has to do with pure size, (area) and also the
Reynolds Number effect. Larger would measure more lift per square foot than
the smaller per square foot due to the multiplier of the Reynolds Number in
the equation.

> But on 13" diameter cylinder, any lift produced would be so
> insignificant, as to be barely measurable.

True, it would be barely measurable, but it would be measurable, *if* you
wanted to do it.
--
Jim in NC

[Tedstriker]

On Tue, 14 Jun 2005 23:32:34 -0400, "Morgans"
> wrote:

>
>"Tedstriker" > wrote
>
>> A dirigble can produce some lift due to it's size, the air would
>> have so far to travel to get to the top to neutralize the low pressure
>> up there.
>
>Incorrect. The reason the dirigble has noticible lift is not how far the
>air has to travel, but has to do with pure size, (area) and also the
>Reynolds Number effect. Larger would measure more lift per square foot than
>the smaller per square foot due to the multiplier of the Reynolds Number in
>the equation.
>
>> But on 13" diameter cylinder, any lift produced would be so
>> insignificant, as to be barely measurable.
>
>True, it would be barely measurable, but it would be measurable, *if* you
>wanted to do it.

agreed, I should have mentioned reynolds number.
I am inverting the baggage pod, so the more curved portion is in the
bottom. And a comment was made that it would produce lift in the wrong
direction. But the amount of that should be so small as to make
insignificant difference.
Another thing comes to mind, and that is the ability of the pod to
absorb shock in a forced landing with the gear up. Most high
performance tailwheel airplanes are recommended to land gear up in an
off airport, forced landing, to reduce the possibility of a nose over.
But I just remembered watching the "Wings of the Luftwaffe" series
about the ME 163 Komet, that landed on a skid that was equipped with a
shock absorber. And in every case where the skid did not extend, the
piltot suffered severe back injuries to the spine, from the shock of
sliding along the ground. In my plane, there is only inches of space
between the pilots seat, and the belly with the gear up, and in a
forced landing, with gear up in a field, I would expect to probably be
subjected to similar types of shocks and back injuries. Very painful.
The only shock absorber I have is the foam in the seat cushion. So I
am thinking that the belly pod should be reinforced to possibly
provide some shock absorbing ability. Couldn't hurt. My plane lands
around 80mph, stalls at 65. So I'd be initially sliding along at a
good clip. Add to that going over rows of plowed ground. It could be
very violent. And most fields look smooth as a carpet from the air,
and it's only when you are so low as to make landing elsewhere
impossible, that you can see what the field conditions really are.

[Morgans]

"Tedstriker" > wrote

> The only shock absorber I have is the foam in the seat cushion. So I
> am thinking that the belly pod should be reinforced to possibly
> provide some shock absorbing ability. Couldn't hurt.

Remember that parts tearing off, also removes energy. I'm not so sure that
I wouldn't design it to break away, after some reasonable stress.

Is it possible to put some closed cell Styrofoam (like cheap ice chests)
between your seat foam and the floor? That is what is in motorcycle
helmets.

I agree with your assessment that the pod up or down isn't a significant
issue. Personally, I would go with what looks best.
--
Jim in NC

[Tedstriker]

On Wed, 15 Jun 2005 22:55:44 -0400, "Morgans"
> wrote:

>
>"Tedstriker" > wrote
>
>> The only shock absorber I have is the foam in the seat cushion. So I
>> am thinking that the belly pod should be reinforced to possibly
>> provide some shock absorbing ability. Couldn't hurt.
>
>Remember that parts tearing off, also removes energy. I'm not so sure that
>I wouldn't design it to break away, after some reasonable stress.
>
>Is it possible to put some closed cell Styrofoam (like cheap ice chests)
>between your seat foam and the floor? That is what is in motorcycle
>helmets.
>
>I agree with your assessment that the pod up or down isn't a significant
>issue. Personally, I would go with what looks best.

Yes, and the pod that is designed for the eze's is better inverted on
my plane's belly, as that way the pod's tail has an upsweep, and
better ground clearance in the 3-point attitude.
I may in fact have room to put some closed cell foam under the pilots
seat. And if so, I'll put some in there. I forgot to mention, the
pilot's seat is a canvas sling-type attached to a 4130 steel frame. So
that would probably stretch and provide some additional cushioning, if
it didn't tear. If that happened, that would be the time to have the
foam underneath.
The break away idea sounds reasonable, so I won't get carried away
making it too strong. If it were, I would assume it would transfer
stress to other areas of the airframe, causing other failures.

[TJ]

In article >,
"Montblack" > wrote:

> ("Thomas O'Grady" wrote)
> [snip]
> > I have a pod on my Cessna 206. It comes to a point on the front, but
> > the sides and bottom are all flat sheets and the corners have very
> > little radius, maybe 1 inch. It wraps up the side of the fuselage about
> > 4 inches, so the bottom is actually flatter than the original. It is
> > less than 8 inches behind the exhaust.
>
>
> What's the approx size of your pod L-W-D?
> (...forget the ends if that's an easier est. <g>)
>
> How do you access it?
>
> What did it cost in performance numbers before-and-after? Noticeable?
>
> Oh, what's the back of your pod look like?
>
> Thanks.
>
>
> Montblack

Useable about 40 inches W x 70 inches L x 9 inches D, overall 96 inches L
10 inches H x 27 inches W door on side.
Book says 5 to 8 mph and 50 fpm climb
Width tapers from 40 inches at 60 inches back to 30 inches at 84 inches
to 20 at end. Bottom is flat and curves up to meet the fuselage.
Book says "designed to accommodate three 'two-suiters' plus misc"