jeremylj93
Posts: 4
Joined: Sat Sep 01, 2007 2:20 pm

Hi, I've done the research on this question but i can't find the answer.
my project topic is : Can I Build a Functional Hovercraft OutOf Normal, Everyday, house hold items?
I cant figure out what the variable would be and how i'll control my experiment. Can you please help me out?
Jeremy J.

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

jeremylj93 wrote:Hi, I've done the research on this question but i can't find the answer.
my project topic is : Can I Build a Functional Hovercraft OutOf Normal, Everyday, house hold items?
I cant figure out what the variable would be and how i'll control my experiment. Can you please help me out?

First, you need to make a hypothesis. For example,

I hypothesize that I need X horse power to lift y pounds.
I hypothesis that design A will hover higher than design B.
I hypothesis that material with property Y is best for the hovercarft skirt.

You've done a lot of reading, so you should be able to come up with a hypothesis that you find most interesting (and have an idea on how to test). Once you have a hypothesis, it will bemuch easier to identify the variables. If you still have problems, post your hypothesis back here and we will help.

http://www.sciencebuddies.com/mentoring/phpBB2/viewtopic.php?t=2353&highlight=hovercraft

http://www.sciencebuddies.com/mentoring/phpBB2/viewtopic.php?t=2025&highlight=hovercraft

This link has information about the whole science fair process, including variables.

http://www.sciencebuddies.com/mentoring/project_guide_index.shtml

Hope this helps!

Louise

jeremylj93
Posts: 4
Joined: Sat Sep 01, 2007 2:20 pm

Louise wrote:
jeremylj93 wrote:Hi, I've done the research on this question but i can't find the answer.
my project topic is : Can I Build a Functional Hovercraft OutOf Normal, Everyday, house hold items?
I cant figure out what the variable would be and how i'll control my experiment. Can you please help me out?

First, you need to make a hypothesis. For example,

I hypothesize that I need X horse power to lift y pounds.
I hypothesis that design A will hover higher than design B.
I hypothesis that material with property Y is best for the hovercarft skirt.

You've done a lot of reading, so you should be able to come up with a hypothesis that you find most interesting (and have an idea on how to test). Once you have a hypothesis, it will bemuch easier to identify the variables. If you still have problems, post your hypothesis back here and we will help.

http://www.sciencebuddies.com/mentoring/phpBB2/viewtopic.php?t=2353&highlight=hovercraft

http://www.sciencebuddies.com/mentoring/phpBB2/viewtopic.php?t=2025&highlight=hovercraft

This link has information about the whole science fair process, including variables.

http://www.sciencebuddies.com/mentoring/project_guide_index.shtml

Hope this helps!

Louise

well my hypothesis is : If I build the hovercraft correctly then It will be able to hover above the ground.
Jeremy J.

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

jeremylj93 wrote:
Louise wrote:
jeremylj93 wrote:Hi, I've done the research on this question but i can't find the answer.
my project topic is : Can I Build a Functional Hovercraft OutOf Normal, Everyday, house hold items?
I cant figure out what the variable would be and how i'll control my experiment. Can you please help me out?

First, you need to make a hypothesis. For example,

I hypothesize that I need X horse power to lift y pounds.
I hypothesis that design A will hover higher than design B.
I hypothesis that material with property Y is best for the hovercarft skirt.

You've done a lot of reading, so you should be able to come up with a hypothesis that you find most interesting (and have an idea on how to test). Once you have a hypothesis, it will bemuch easier to identify the variables. If you still have problems, post your hypothesis back here and we will help.

http://www.sciencebuddies.com/mentoring/phpBB2/viewtopic.php?t=2353&highlight=hovercraft

http://www.sciencebuddies.com/mentoring/phpBB2/viewtopic.php?t=2025&highlight=hovercraft

This link has information about the whole science fair process, including variables.

http://www.sciencebuddies.com/mentoring/project_guide_index.shtml

Hope this helps!

Louise

well my hypothesis is : If I build the hovercraft correctly then It will be able to hover above the ground.

Okay, compare your hypothesis to the ones I suggested. You see that mine all have very testable things and yours doesn't. If I said, "If I bake a cake following a recipe, it will taste good", it isn't a science project, even if I say it is a hypothesis. This is why you cannot find any variables- there aren't any with your current hypothesis!

Look at one of the ideas I suggested:
I hypothesize that I need X horse power to lift y pounds.

Your motor/fan would be a controlled variable. The weight of the hovercraft would be the changing variable. The height the hovercraft hovered would be the respondng variable. So, you would change the weight of the hovercraft, and measure how high it hovers.

So, pick some part of the project design that you might like to change (see suggestions above) and try to develope a hypothesis.

Please read the science fair guide agaian that I linked to before. You want to specifically focus on the variables section and the hypothesis section:

http://www.sciencebuddies.com/mentoring/project_hypothesis.shtml

Louise

jeremylj93
Posts: 4
Joined: Sat Sep 01, 2007 2:20 pm

### measuring horse power

in your example for my hypothesis, you stated i need X horse pwer to lift Y pounds. so lnow my hypothesis is : If my leaf blower emits 20 horse power then my hovercraft will lift 200 ponds. so how would i measure the horse power? because the link you gave me said my hypothesis must be able to be measured on both the IF and the THEN part of the hypothesis. thank you
Jeremy J.

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

### Re: measuring horse power

jeremylj93 wrote:in your example for my hypothesis, you stated i need X horse pwer to lift Y pounds. so lnow my hypothesis is : If my leaf blower emits 20 horse power then my hovercraft will lift 200 ponds. so how would i measure the horse power? because the link you gave me said my hypothesis must be able to be measured on both the IF and the THEN part of the hypothesis. thank you

I don't know exactly how you would measure horsepower (this is why you should pick something you can easily test/measure), but it might say in the instruction book what the power (or wind speed or something like that) is. Or, if it has different settings (low, med, high) it should tell you about each one. You could also call the company, and ask them.

Louise

Craig_Bridge
Former Expert
Posts: 1297
Joined: Mon Oct 16, 2006 11:47 am
If my leaf blower emits 20 horse power then my hovercraft will lift 200 ponds

"emit horse power" is VERY hard to measure. Taking a bit of a detour into engines "developing horse power" in the automotive industry is measured by a simple engine dynamometer; however, to measure horse power delivered to the drive wheels, the measurement is extremely difficult and expensive and requires specifying a lot more conditions. A hover craft is an even more complex measurement problem because it invoves fluid dynamics and not the simpler mechanics in the car example. End of detour.

A hover craft is all about developing a pressure differential sufficient to lift its weight while delivering enough volume of air (cfm) to maintain the pressure. The perimeter length of the skirt, the skirt design and its ability to conform to the surface it is hovering over will determine the leakage per unit of perimeter per minute which will determine the CFM required. The area under the skirt and the weight of the craft will determine the PSI required to lift. The efficiency of the fan at the PSI and CFM and resulting rotational speed will determine how much energy is required (e.g. horse power needed).

BTW: Have you looked up the horsepower ratings of leaf blowers? You are off by at least a decimal point in reality in their "input" horsepower and their "output" horsepower is a small fraction of their input.

From an engineering perspective, I doubt you can safely experiment with any hover craft like apparatus that is self contained. The weight of the motor and fan will be a significant portion of any hover craft and until you use exotic multi-stage turbine compressor designs like jet aircraft engines, they won't be able to lift their own weight using air pressure under a skirt. I'm not recommending giving up, I'm recommending scaling back to experimenting with an external air source and some small hose connected hover craft models and finding an easier hypothesis to test.
-Craig