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Old Jan 20, 2011, 06:53 PM
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United States, GA, Buford
Joined Nov 2007
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Operation X-Craft: A Full Size Electric Hovercraft

The title pretty much sums it up. What I want to do is build a full size hovercraft.

Here is the main thread.
http://www.rcgroups.com/forums/showthread.php?t=1356457

The objective is to build a hovercraft with the following requirements:
- must be able to carry me
- compact size with good looks
- easily controlled
- electric
- water and flotation capable

Objectives:

Must be able to carry me:
The thing about this is that I only weigh 125lbs. I would like to be able to carry 175lbs. Am I being unrealistic? (Don't answer that question, because wether you say yes or no, I will reach the 175lb mark and I will strive for 200lbs.)

Compact size with good looks:
This has to be relatively small for the reasons of cost and portability. Size is money, and everyone knows that that is true. I also don't want to have a special trailer. I would like to just turn it on its side (or just slant it), take the fan shroud off, and throw it in the back of a pickup truck. Of course the rear ened would be hanging off, but ropes and padding can handle that just fine.
I don't like sloppy work. I have done basic school projects till my hand bled from the amount of time I was putting pressure on my hand. I have replaced a partner's efforts with my work if it didn't meet my standards. I have even ticked off (in a good way) my friends when washing cars due to the time I spend just cleaning the rims alone.

Easily controllable:
I figured size would play a key role in maneuverability. To add to the small size, this craft will be extremely lightweight. It will have an all foam construction with a few ply reinforcements. I aslo hope than my fan selection will give me decent thrust.

Electric:
If it wasn't electric, I wouldn't be posting this at all. This will look really good for college. I am 17 years old in twelfth grade and am getting my college stuff together. I would like to get in done in time for the science fair, which I think is at the end of March.

Water and Flotation capable:
I would like to take advantage of the bag skirt by having the capability to go on water. Things do go wrong though. In the event of a mishap, the foam construction and displacement of the hull should keep the hovercraft, the driver, and the driver's family up out of the water. That family part is just an expression, but you get what I mean.

The Hovercraft itself and List of Bills:
- the hovercraft hull
- the skirt material
- the electronics
- various hardware, such as nuts and bolts

The Hovercraft Hull:
The hull for the hovercraft will be made of foam. The foam of choice is what we all know as wallboard. It is the white isolating foam sheets that you find in hardware stores. The hull will be made of 1", 2", and 4" (if I can find) foam sheets. The base will be made of two sheets of 2" foam. Between them will be 4" spacers. These spacers will be responsible for creating and maintaining the strength of the hull. These spacers will also create the air chamber (lack of proper term). If you do not understand my description, you will see what I mean when I post the pictures. The style will come from the fairings. The fairings are not necessary for making the hovercraft work, so its strength doesn't have to be all that. They will be made of 1" foam. The fan shroud will also be made of 1" foam, but will have a 1" thick ring around the leading edge. The control vanes will be made of reinforced 1" foam.

1"x4'x8' Foam Sheet - Cost Each $12.57, Final Cost $?
2"x4'x8' Foam Sheet - Cost Each $21.97, Final Cost $43.94
If I can not find a 4" sheet, I'll have to get another 2" sheet.

The Skirt Material:
The common skirt material for hovercrafts is nylon. I want to use polyester, which is more resistant to damage. The skirt will be sealed all around. The skirt will rap around the air chamber. There will be no holes in the skirt.

I will need 8.52 yards.
$9.99 per yard, Final Cost $89.91

The Electronics:
I spent a few days looking over a very big list of components. I have settled on the batteries, motors, speed controllers, monitoring equipment, and more. My list is below.

Main Components
ZIPPY Flightmax 5800mah 6S1P 30C - Two of these will be paired in series to result in a 5800mah 12S1P 30C lipo.
Cost Each $68.58, Final Cost $137.16
Turnigy 80-100-A 180kv Brushless Outrunner
Cost $99.95
Turnigy 80-100-A 130kv Brushless Outrunner
Cost $100.33
Turnigy Sentilon100A HV 5-12S BESC (Ver4) - Two of these will be the driving forces behind the motors.
Cost Each $82.07, Final Cost $164.14
Control and Monitoring Components
Turnigy Servo Driver - One of these will control each ESC. I might use another as I am thinking about implementing a complete drive-by-wire setup.
Cost Each $8.95, Final Cost $17.90, Drive-by-Wire Cost $26.85
Turnigy S8166M Servo 154g / 33kg / .21sec - This would be the servo of choice for the drive-by-wire- setup.
Cost each $24.95, If I use two $49.90
Turnigy 6S Mini Lipo Battery Monitor
Cost Each $8.89, Final Cost $17.78
Turnigy Watt Meter and Power Analyzer
Cost Each $23.95, Final Cost $47.90
Turnigy BESC Programming Card
Cost $6.95
Reciever/System Switch

Math:

Charge Time and Discharge Currents:

So we know that the mAh of the 6 pack setup is 37,400mAh.

A x H = AH, where A=5
H = AH / A
37.4 / 5 = 7.48
-------------------------
7 hrs, 28 min

where A=7
37.4 / 7 = 5.3428
-------------------------
5 hrs, 20 min, 34 sec

where A=10
37.4 / 7 = 3.74
-------------------------
3 hrs, 44 min, 24 sec

Max charge current: 74.8 amps
Continuous discharge current: 561 amps
Max burst discharge: 748 amps

Runtime:

I = 140a, but I will not be drawing that much per motor. ... 5.8ah battery
Please correct me if my math is wrong.

A x H = AH (capacity)
H = AH/A

80(2) x H = 5.8
H = 0.03625
.03625 x 60 (min) = 2.175 minutes

That isn't much, but the batteries are not heavy, so I can always just add more at a cost of $137.16.
S = amount of battery pairs
137.16 x S = 2.175 x S = cost for a given time

Do I have the power?

I have plans for the power if things don't workout as planned. The 180kv motor puts out 7000W. That is equivalent to 9.387hp. But lets consider that as being optimistic and drop the hp down to 7. The remaining 2.387hp will be safety. Going off of that, There should be enough power to easily get the craft 6" off of the ground.

A UH-10F is around the same size, but has an 8" hover height and weighs 140-170lbs. Specs say a 8-15hp engine that weighs less than 65lbs. You also need fuel.

- The little motor I'm looking at only weighs 1570g which is 3.461lbs. Two of those make 7lbs.
-The batteries taken into consideration weigh 838 grams which is 1.847lbs. Six of those make 12lbs.
- The ESCs only weight 125g which is .276lbs. Two of those make .6lbs.
Note that I added to the weights when I made my estimate. This should accomidate for associated wiring.

So the entire motor and energy package only weighs 19.6lbs. Wow, that is an entire 50lbs less already! Total amp draw will be about 150-190 amps, maybe even less.

Comparison:

I am basing the power requirements off of the UH-10F.


UH-10F Specifications
Capacity - 1 Person
Payload - Up to 250 Lbs
Speed - 25 to 35 mph
Hover Height - 8 inches
Length - 10 ft
Width - 5 ft
Empty Weight - 140 to 170 Lbs
Flotation - 600 Lbs
Climb Gradient - 10 to 20%
Engine - 8-15 hp horizontal shaft (under 65 Lbs)
Construction Method - Foam and Plywood Composite
Construction Time - 40 to 100 hours

X-Craft Specifications
Capacity - 1 Person
Payload - striving for 175 Lbs
Speed - striving for 25 mph
Hover Height - 6 inches
Length - 8 ft without skirt, 9 ft 2 in with skirt
Width - 4 ft without skirt, 5 ft 2 in with skirt
Empty Weight - striving to keep it below 100 Lbs
Flotation - striving for 400 Lbs
Climb Gradient - IDK
Engine - Twin 7000W bl motors
Construction Method - Foam with Wood and Fiberglass Accessories
Construction Time - IDK
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Last edited by boredom.is.me; Jan 20, 2011 at 07:04 PM.
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