Science Project: How can propeller blade shapes/ cuts affect the speed of a 7.5CC motor? (Need help

[Brandon Atwell]

For my science project this year, my teacher asked we do a high level project as he wants us to be entered into the county science fair.

I thought what better to do than test a variable on model boats.

So here's my set- up:

6 differently cut 1450's (test)

we will keep the hull the same (Shaman tunnel boat)

Motor (Rossi 7.5CC outboard)

Lower unit (K&B )

We will also be using the same radar gun and be testing at the same pond.

I have to do research before starting, so I was wondering what you guys have seen from trying different cuts on props and how it has affected the speed of a boat.

Thanks for helping me out guys,

Brandon

 

[stan simpson iv]

Sounds like fun...

 

[Brandon Atwell]

I feel i need to be more specific,

I'm looking to see how a different prop cuts affect the overall attitude of a boat.

How can one cut maybe help speed, but lose handling, or vice- versa, what cut tended to want to make a boat blow over more often, etc.

We will be making SAW passes only, no ovals.

This does not have to be for one particular cut, i just need to know how cutting a prop in different ways affects the speed.

Also, does not need to be solely on the 14XX series as I stated before.

Any ideas for websites to check out?? As I need multiple sources for infromation. Would be nice to have an experts opinion though.

Thanks guys,

Brandon

 

[Thomas Hulbert]

if you are doing it as a sience project you will need to be able to back up your experaments.

I would look at getting a fish tank and rig the motor to it with a set of recirculating system for the prop thrust and have it run as an electric system. This way you can measure the thrust produced ( water speed ) amp draw on the motor temp and different rpm.

This way you can be able to display your test rig at a science fair if needed.

inlet of test tank on bottom of tank ( baffled ) outlet of test tank to catch tank ( in line with prop thrust ) catch tank is to remove any air bubbles foarmed in thrust ( multy baffles to reduce bubbles ) outlet of catch tank to main tank should have a spill flow infeed.

Tweeking of the tank system would be need to get the best water conditions for you to see the prop for cavatation etc.

Look for some cavatation vidios on the web and this might also help you out.

 

[RonShaw]

I feel i need to be more specific,

I'm looking to see how a different prop cuts affect the overall attitude of a boat.

How can one cut maybe help speed, but lose handling, or vice- versa, what cut tended to want to make a boat blow over more often, etc.

We will be making SAW passes only, no ovals.

This does not have to be for one particular cut, i just need to know how cutting a prop in different ways affects the speed.

Also, does not need to be solely on the 14XX series as I stated before.

Any ideas for websites to check out?? As I need multiple sources for infromation. Would be nice to have an experts opinion though.

Thanks guys,

Brandon

Brandon,

Here is a great website that will help answer most of your questions:

http://rcboat.com/prop.htm

Good luck with your project. Get an "A" and follow-up with your findings. It will be interesting to see what you post and the feedback you will get!!!....

 

[stan simpson iv]

So what is the "MAD SCIENTIST" up to,how you coming along with the proj..

 

[Brandon Atwell]

Just gotta finish up some research.

Then it' s off to testing!

- Brandon

 

[larcor69]

20 somedays since your last post, whats your findings?

 

[Brandon Atwell]

Sorry!

I just saw this. I did figure out the Shaman/ Rossi combo does NOT like the 1450's we have. I dont even want to say the numbers we got out of it, lol.

- Brandon