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

( 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

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

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?

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?

"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

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.

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.

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

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.

Now thats what I had in mind.