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

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" 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

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

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.

("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

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"

"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.

( 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