Propellers

[Mr Crayon]

I have noticed that it seams to be standard practice to replace the kit provided propeller. I was wondering how the different size propellers behave and what would be the best size for my own model.

My model is a 20" span Beechcraft Musketeer, and I have just started building a 24" span Cessna 180.

I guess a bigger propeller would result in a slower flight, which could be good. Also wondering how important it is to balance and lighten the prop.

[thymekiller]

I could be wrong, but I believe that as a general rule: A prop should be about 25% of the wing span, on a rubber powered plane. More than that might produce torque roll, and less is under powered. Not a hard fast law, just a decent starting point.

Balancing. A bad prop can cause a shaky flight and stress your plane, maybe shake it to death. After you balance one, you will see the BIG differance. Spin it on the plane once or twice while holding it in your hand and then again after balancing. You will then understand far better than I can explain with words. This is how I was taught. I was surprized !!! All props need to be balanced, regardless of who made it. I was also surprized at what a differance a tiny drop of lite oil on the prop shaft made.

The weight and pitch of a prop depend on who you ask. Some like a heavy prop because it puts ballast where it does the most good , therefore you need less dead weight in the nose. Some dont like the heavy spinning mass. Take your pick. My knowledge of pitch angle is poor at best, so I'm going to hope someone else will share with all of us.

Balanceing also means checking that both blades have the same pitch angle and are the same lengh.

Hope this helps.
thymekiller

[MickeyB49]

I have just started building these kits again. the last time i did so I was in my teens. Right now I am still leaning the ropes, so mostly I am working on my building techniques and not focusing on flight yet. I was wodnering if anyone knows of a manufacturer who makes three and four blade props for kits like the 400 series Fw-190 and P40? Since my planes right now are more for display then they are for flight, I would like t make them more authentic looking. Right now I have no clue how to carve a prop like is shown on the plans.

[MickeyB49]

oops, I said in my former post that I was building the 400 series planes. Actually I am building the 500 series P40, FW190 and the Spitfire. I also have the 900 Series P51. It would be great to have multiblade props for them. Thanks all.

[cliffm]

I will try and share my understanding of pitch. Comparing it to gearing, the greater the pitch the higher the gearing. The less pitch, the lower the gearing . If you want a long steady pull on your rubber motor you would go with a greater pitch, whereas, if you want a fast, quick climb with that same motor you would use a prop with a decreased pitch allowing for higher rpm's, smaller bites of air making for quicker acceleration. So for longer sustained flights you would seek an air screw with greater pitch thus lowering your revs with the bigger bites it takes. Hope this helps cliffm