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orion

Well-Known Member
Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
Well, since you ask...

First off, no, a sphere is not the most aerodynamic shape, at any speed. The most aerodynamic shape is an airfoil. If we look at the example of equivalency and just at a 2D case, if you take a circle like a cross section of a flying wire or rod, a simple 1/8" diameter wire has the same drag as a symmetrical wing airfoil shape with a chord of about two feet. If the wire is smooth, the drag is even worse.

So, for a belly container, you could assemble something like a torpedo or some faired in surface like a revolved airfoil, but when you suspend it under the belly of an airplane or under a wing, you will have the extra drag of the suspending mechanism plus all the interfearance drag that is created whenever you have two bodies moving through the air in close proximity to each other.

Done right, a conformal tank would be better however, you do not want the point of the shape below the surface of the belly like you show in the last set of pictures. Look again at the pod with the kids. Yes, it's ugly and it could be done much better and prettier than that, but in general, that is sort of an ideal configuration.

The best would be more of a tapered and rounded cross section which is then blended into the belly. One word of caution though - the pod in that case will sit just aft of the cowl. You will need to make sure that the heat of the exhaust will not impinge on the structure and also make sure that the mounting of the pod does not affect the air flow in front of it to the point of decreasing the effectiveness of the cowl bottom where the cooling air exhausts.
 

Captain_John

Well-Known Member
Joined
Feb 3, 2003
Messages
699
Location
KPYM
HA!

The exhaust!

That is why it isn't done!

DOH!

I like the last pic, but initially I planned it to be wider.

After thinking about the exhaust heat, maybe one just like that pic under the Pax side for Balance and to remove it from the exhaust stream?

Hmmm,

This place is GREAT for brainstorming!

:gig: CJ
 

BD5builder

Well-Known Member
Joined
Jul 29, 2005
Messages
102
Location
Greenville, SC
the only thing i can think of for a release mechanism would be a pair of the Hartwell canopy latch's for the BD-5. They have a locking mechanism that is actuated with 1 handle, and also have a "safety" lock that if the latch where to come un-done the pod/canopy would not pop open/come off. But i'm not sure if it would be up to holding a 100 or 200lbs.
 

Captain_John

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Joined
Feb 3, 2003
Messages
699
Location
KPYM
Originally posted by ebonheart_2
What plane is this for again... an RV-7?
Yep... a dash Seven.

The mechanism is a ways off, but do you have a pic of this one you speak of?

:D CJ
 

Captain_John

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Joined
Feb 3, 2003
Messages
699
Location
KPYM
OH! I see... I won't need anything that nice. A "tools required" one is fine with me, as I won't be deploying it unless I am on terra firma. A simple loading door is all I need along with a bolt up installation method.

Thanks for the input!

:D CJ
 

Midniteoyl

Well-Known Member
Joined
Sep 3, 2003
Messages
2,406
Location
Indiana
I am open to plastic. I would beed to practice before taking on a task as big as that!
Sacrificial foam mold. When the shape is prefect, cover it in fiberglass, 'melt' the foam, add attach points and a door, and 'voilà'.

As for the attach points, how about 4 eye attachments mounted to the belly, two fore / two aft, that are received by the belly tank, with through rods inserted span-wise, one fore / one aft? A flexable urethane or silicone fairing mounted on the tank would cover any gap and smooth the transition..
 

Captain_John

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Joined
Feb 3, 2003
Messages
699
Location
KPYM
Need to mount a demonstration slice of plastic there to be sure it won't melt from the exhaust heat!

:D CJ
 

Craig

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Joined
Jan 30, 2003
Messages
543
Location
Jupiter, Florida
Attachments

When I was welding the fuse on Deuces Wild, I welded on 4 - 4" stubs from frame sta. 3 and 4 - with a "tee" at the end for a span-wise AN-4 bolt. That is how we attach our "bomb", which is actually a weather-tight cargo container.

We limit the load in the bomb to 50 lb. - at 6G, that is 300 lb. Working through any two AN-4 bolts, that amounts to about 150/each - well within the limit for those bolts.

Takes about three minutes to install or remove the thing, which we made from an old water-softener tank and added some plastic fins and a dummy nose fuse. Cut the door out with a die grinder, glassed in a ledge, and used some good weatherstrip material, hinges, and latches to keep it water tight.
 

Midniteoyl

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Joined
Sep 3, 2003
Messages
2,406
Location
Indiana
Re: Attachments

Originally posted by Craig
When I was welding the fuse on Deuces Wild, I welded on 4 - 4" stubs from frame sta. 3 and 4 - with a "tee" at the end for a span-wise AN-4 bolt. That is how we attach our "bomb", which is actually a weather-tight cargo container.

We limit the load in the bomb to 50 lb. - at 6G, that is 300 lb. Working through any two AN-4 bolts, that amounts to about 150/each - well within the limit for those bolts.

Takes about three minutes to install or remove the thing, which we made from an old water-softener tank and added some plastic fins and a dummy nose fuse. Cut the door out with a die grinder, glassed in a ledge, and used some good weatherstrip material, hinges, and latches to keep it water tight.



Sounds about right :gig:
 
Joined
Nov 1, 2005
Messages
16
I've seen a picture somewhere recently of a floatplane with a surfboard lashed to the float struts on one side. Seemed to be flying along just fine - asymmetry and all. Personally, I'd try carrying something small and gradually work up. Just in case.

It was on some Canadian manufacturer's page. Murphy was the first thought that came to mind but I couldn't find it there.

Best Wishes, Max
 

Rhino

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Joined
Apr 8, 2004
Messages
771
Location
SW Ohio
Murphy used to always run ads with a picture of a Moose floatplane with a canoe strapped to the float struts. I know others do that regularly up north, so asymmetry can't be too bad, at least in some cases. I imagine the inside of that canoe must create some hellacious drag, being hollow and all.
 

Captain_John

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Joined
Feb 3, 2003
Messages
699
Location
KPYM
The Cessna 180 series floatplanes have a "Moose/Canoe" STC for externally carried loads. Basically it is a loading scenario for stuff strapped onto the floats!

My friend had it on his floatplane that I trained in.

I never saw him carry anything, though.

:p: CJ
 

PilotSpike

Member
Joined
Dec 3, 2005
Messages
5
John you could also look into moving the end of the exhaust pipe.

I think personally I would look at a conforming belly space under the fuse. Keep in mind though that this is going to be more of a pain to load than on the Zenith, etc, because its a low wing. You will have to be on your back or knees to get to it dude.

How much ground clearance do you have now between the belly of a 7A and the ground, say, midway back?
 
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