newbie prop question

What plane and what engine?

If it's an .049 reed valve then a 5x3 is a good one as Jim suggested.

You probably won't find them at your local hobby shop. Smallest you usually find is 7" and up.

Ron

you are right about not finding the size i need,pitch explanations make sense yes i have only 049s and a couple of tee dee 051s

I buy master airscrew 7x3's and cut them down. I go as far as 4.75x3 on my "hot" reed valve engines but that is with 15% nitro. My next fuel purchase will be 25% and that may call for 5x3.

Jim

It may go without saying... both of the Cox resellers here on this forum...be it Matt at ExModelengines or Bernie at CoxInternational have a great supply and superb prices on all the .049 through .15 props you may need..

That said, if all out performance is your cup o tea than shop for the Russian or Ukrainian glass 4.25X2.55 or similar for all engines in the .049/.051/.061 class

Might I suggest VY 4.49x3.15" (114x80mm) Blue 1/2A F/G Propeller VY 4.49x3.15" (114x80mm) Blue 1/2A F/G Propeller

Available now, as of Oct. 25' 2012

Technical Details:

Specially Designed for 1/2A Combat and other 1/2A applications

from Hobby club at
http://www.hobbyclub.com/product_info.php?cPath=29_62_176&products_id=1349

bullit132 wrote:you are right about not finding the size i need,pitch explanations make sense yes i have only 049s and a couple of tee dee 051s

PM sent.

JPvelo wrote:I buy master airscrew 7x3's and cut them down. I go as far as 4.75x3 on my "hot" reed valve engines but that is with 15% nitro. My next fuel purchase will be 25% and that may call for 5x3.

Jim

JP, you really cut down the MA 7" props. Is the hole in the hub the right size?

My go-to prop for my 1/2As is the Master Airscrew GF series 6x3. I cut them to 5", 5-1/4", 5-1/2", and 5-3/4". The 6" is too much load for stunting. I have used them on Big Migs, but they are really too much for them in tight stunts too. For plain circles they work fine on most of the engines.

If I want to fly a small circle on 35' lines with a fast engine(Tee Dee or Norvel), I put an APC 6x2 or 5.5x2 on it. APC props aren't as heavy a load as MAs and let the engine turn high enough RPMs to run well, but the 2" pitch keeps them from moving a gazillion MPH.

My main flyer:
http://masterairscrew.com/6x3gfseriespropeller.aspx

A good balancer like a Top Flite magnetic is a Must-ave item. It takes a while to get the hang of balancing, but it will save your engines and make a big performance difference.

I totally agree! The cut down MA's work good. I plan on using them more now that my crashes are more infrequent. They can be a bit on the fragile side.

My advice to any new flier is stick with the Cox rubber duckies. They are nearly indestructable.

Ron

....also, remember the pitch is a average across the length of the blade, if you take a 7"x3" prop and cut an inch off each side you'd likely end up with a 5x4-5x5 prop?

That's true, Cribbs is right. Just bend them back straight and keep flying. I never had any luck balancing the rubber duckies, so until you graduate from noobiehood, just bolt them on and fly. From the time I was 12 until I was 54, I never balanced a damn prop. Then I got anal about it when I started turning into a high performance stunt nut. One thing at a time. We don't want you to get overloaded with details. Just have fun and experiment. Keep asking questions and it will gradually fall into place.

Mark Boesen wrote:....also, remember the pitch is a average across the length of the blade, if you take a 7"x3" prop and cut an inch off each side you'd likely end up with a 5x4-5x5 prop?

And that, my friend, is a recipe for making a plane go VERY fast. Maybe that's why JP is turning 3 second laps. He can handle it, but it took a bit of practice.

I cut down 7x3 because that's the smallest me hobby shop carries. I may order some 6x3 now that I'm not busting a prop every flight. I wish the apc 5x3 wasn't five bucks. That's a faaaast prop!

I think RknRusty started the performance differences, first. Now, from what I understand, the prop's pitch controls the speed of the plane, and the diameter controls the speed of the engine. That's as simple as I can get it. True? Any explanation offered for that by a real expert would probably help.

Gus:

Propeller PITCH is the theoretical inch distance moved forward in one propeller revolution.

(Since propellers are never 100% efficient this must be factored in considering the weight of the plane and the air resistance it presents)

Engine TORQUE is the pulling power the engine produces at a given RPM.

(High RPM does NOT equate to greater torque. It depends upon the plane used))

SD

Bullit, here's some info for your future use in balancing, but for now, good important things to know regarding getting your prop properly centered on the engine. A lot of people don't realize the true center of a prop is the molded hole in the REAR of the hub, not the front hole.

http://www.apcprop.com/v/html/balancing.html

well learned something new today,i dont have any apc props,all i have is thimble drome6x3s and 5x3s also windsor 6x3s and cox 5x3s i got my props off of used engines i purchased,i think there kind of old??

bullit132 wrote:well learned something new today,i dont have any apc props,all i have is thimble drome6x3s and 5x3s also windsor 6x3s and cox 5x3s i got my props off of used engines i purchased,i think there kind of old??

If they are flexible and don't have any stress cracks when bent back and forth they are probably fine. Even so safety glasses may be required when starting.

too late,ive allready test run every engine i have with the props they came with,safety glasses,whats that????

GUS THE I.A. wrote:I think RknRusty started the performance differences, first. Now, from what I understand, the prop's pitch controls the speed of the plane, and the diameter controls the speed of the engine. That's as simple as I can get it. True? Any explanation offered for that by a real expert would probably help.

yep, that pretty much sums it up: Pitch for speed, diameter for RPM.

I have had seemingly good props EXPLODE when the engine is started. These have been aged props that looked good and seemed supple.

"Rubber ducky" props are props that do not have a reinforcing fiber in the plastic. They are very crash resistant, and can be quite chewed up and still be "safe" to operate, at least in the sense they won't shatter in operation. Rubber ducky props also tend to flatten under high RPM so the actual pitch in use may be less than the pitch when the engine is not running.

More rigid props have glass or polyester fibers in the nylon plastic. These tend to perform better since the prop is much more rigid, however they are also much more fragile and tend to not survive propeller strikes and crashes.

Eye and hearing protection are recommended.

Phil

bullit132 wrote:too late,ive allready test run every engine i have with the props they came with,safety glasses,whats that????

For now a 5x3 to 6x3 prop should serve you well. Make sure you do not get props meant for electric use.

Be aware that using small props and higher nitro fuel will increase the possibility/frequency that you will need to reset the fit between the piston and the connecting rod.

If you are not going to wear safety glasses be careful of the prop arc in case a blade breaks off.

George

RknRusty wrote:

JPvelo wrote:I buy master airscrew 7x3's and cut them down. I go as far as 4.75x3 on my "hot" reed valve engines but that is with 15% nitro. My next fuel purchase will be 25% and that may call for 5x3.

Jim

JP, you really cut down the MA 7" props. Is the hole in the hub the right size?

My main flyer:
http://masterairscrew.com/6x3gfseriespropeller.aspx

A good balancer like a Top Flite magnetic is a Must-ave item. It takes a while to get the hang of balancing, but it will save your engines and make a big performance difference.

I purchased a top flite balancer yesterday from the LHS and they were kind enough to special order ten MA 6x3's for me.